Theses and Dissertations Collection

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Strategies for establishing adequate phosphorus levels in three soils with different phosphorus fixing capacities
(Sokoine University of Agriculture, 2004) Eliuth, Stephan Ngailo
A study was conducted under pot and field conditions to establish adequate levels of phosphorus in three soils with different P fixing capacities. These soils were from Magadu, Morogoro District, classified as Oxic Haplustidt, Sasanda, in Mbozi District, classified as Drystropept and Nkundi in Nkasi District, classified as Acruoxic Kancliustult. A pot experiment was conducted at SUA- Department of Soil Science while field experiment was carried out at Sasanda in Mbozi District in Mbeya region. The treatments were 0, 40, 80 and 160 mg P/kg of soil for Nkundi, 0, 100, 200 and 400 mg P/kg of soil for Magadu and 0, 800, 1600 and 3200 mg P/kg of soil for Sasanda soil. For field experiment the treatments were 0, 800, 1600 and 3200 kg P/ha. The sources of P were TSP and MPR. There were seven treatments for field and eight treatments for pot experiment. The experiment was laid out in a Randomized Complete Block Design. The tested crop was maize {Zea mays var UH 615). The objectives of the study were to identify rates of P required for optimizing maize dry matter grain yields, and associated available P levels in the soils. Results of the study showed that, both TSP and MPR were effective sources of P in the soils studied. Both TSP and MPR significantly (P = 0.05) increased DM and grain yield, P uptake and available P over the control by 97.7, 95.8, 76,8 and 95.3%, respectively in Sasanda soil. This was attributed to 95.3% increase in available P in the soil after TSP and MPR application in Sasanda soil. This was supported by the highest grain yield, DM yield, and P uptake of 2.97 t/ha, 64.18 g, and 124.8 mg/kg at the rates of 3200 kg P/ha and 3200 mg/kg, respectively in Sasanda soil. However, MPR was slightly less effective than TSP for most of the aspects studied. The optimum rates were 160, 200 and 3200 mg P/kg for Nkundi, Magadu and Sasanda soils, respectively under pots. However, these rates have to be confirmed under field conditions. In Sasanda field experiment, P application did not significantly (P = 0.05) increase available P and the available P was below the critical level. This was attributed to high fixing capacity of the soil. The rale of 1600 kg P/ha gave the highest grain yield of 2.97 t/ha in the current study. Results from the current study indicated that MPR has the potential of supplying P for maize production therefore it could be used as an alternative source of P to TSP. A large, one-time application of P on highly P deficient soils is not always the solution for correcting P deficiency in all soils like in Sasanda soil. A gradual seasonal P application might be the most cost-effective approach for high P-fixing soils.
Agronomic evaluation of some industrial wastes as alternative sources of plant nutrients in Morogoro District, Tanzania
(Sokoine University of Agriculture, 2001) Ndaki, Stephen Mhoja Mashauri
A study’ was conducted at Magadu. Morogoro. Tanzania to evaluate the industrial wastes as alternative sources of plant nutrients and/or soil conditioners. The soil of Magadu was classified by Kaaya (1989) as Oxic Haplustult. The soil was characterised in this study for its physical and chemical properties prior to planting of the test crop. The analytical data showed that the soil was strongly acidic with a pH of 5.1. Total N. available P. %OC, exchangeable Ca and Na. CEC. and DTPA extractable Zn were in the low range. Exchangeable Mg was in the medium range, while exchangeable K. DTPA extractable Fe, Mn and Cu were high. In the field a randomised complete block design was used to evaluate the wastes using maize as test crop. The rate of waste application were 5.24 4.8, 4.25, 4.5 and 3.7 tonnes/ha of waste tea, wattle bark chippings, waste tobacco, wood ash and saw dust respectively. Prior to soil incorporation, the wastes were analysed for their chemical properties. Maize dry matter yields were significantly higher in plots which received 5.24 tonnes/ha of waste tea followed by plots which received 4.25 and 4.5 tonnes/ha of waste tobacco and wood ash respectively. Maize grain yields were significantly higher in waste tea and wattle bark chippings amended plots than in the other waste amended plots. At the end of the growing season the soil was analysed to evaluate the residual effect of wastes on soil properties. Soil pH, available water capacity, available P, % OC, total N, exchangeable bases, CEC, DTPA extractable Zn and Cu in waste amended plots increased in the top 15 cm of soil relative to the control plots. DTPA extractable Fe and Mn, exchangeable Al and acidity were significantly reduced in all waste treatments. Total N and % OC in wood ash and saw dust amended plots were at par with those found in control plots. The results from the field suggested that when applied at agronomic rates, industrial wastes can produce satisfactory plant growth and yields. The results revealed further that waste application on a long term basis will allow good build up of soil organic matter and plant nutrients which in turn will improve on soil productivity. It is recommended that N supplement to wood ash which is rich in almost all macro and micronutrients (except N) would balance its nutrient supply to plants. A glasshouse decomposition experiment was carried out with some wastes including sawdust and wattle bark chippings in perforated plastic litter bags. The wastes were either surface applied or buried to 10 cm depth in wooden troughs. The decomposition process which was monitored at 0. 3, 6, 9, and 12 weeks of incubation revealed that soil incorporated wastes decomposed and released nutrients faster than surface applied ones.
Effects of Land Degradation in the uplands on Land use Changes in the Plains: The case study of Chimala River Catchment in the Usangu plains
(Sokoine University of Agriculture, 2002) Mwalukasa, Emmanuel Hudson
A study was carried out in Chimala River catchment in Makete-Iringa (uplands) and Mbarali-Mbeya (plains), Tanzania to relate land use changes occurring in the plains to upland degradation. The objectives of this study were: (a) to establish land use/cover inventory for the catchment; (b) to assess upland vegetation degradation; (c) to assess upland soil erosion by gully expansion; (d) to assess catchment soil fertility status; (e) to assess the Chimala River water flow trend; and (f) to assess the socio-economic activities related to land degradation. Aerial photographs and satellite images were used, interpreted and analysed using GIS ArcView/ArcINFO and ERDAS Imagine softwares. Mean monthly water levels were compared using a student t-Test. Soil samples were collected from four different forest-covers for organic carbon (OC) content analyses. Total nitrogen (N) contents were estimated using C:N ratios. A structured questionnaire and SPSS programme were used to collect and analyse socio-economic survey data. Results showed that upland grassland decreased by 3.6% and 45.8% for 1963-77 and 1977-2001 periods respectively due to extending cultivation activities. On the scarp, dense and open woodlands decreased by 56.2% and 4.6% respectively for 1963-77 while for 1977- 2001 dense woodland decreased by 100% due to firewood collection; open woodland increased by 21.2% through regeneration. Gully erosion expanded by 206% between 1963 and 1977 because of poor land management but decreased by 69% for 1977-2001 through natural recovery and afforestation. Consequently upland vegetation degradation and gully erosion caused soil transfer from the mountains and deposition in the plains. About 0.4% (1977) and 0.6% (2001) of the catchment area under irrigation were abandoned to bushland due to siltation problems. River valleyiii soils in the plains indicated adequate OC (3.4%) due to alluvial deposition thus attracting more agricultural activities. Low OC (0.61-1.09%) indicated low N (0.06- 0.11%) as a limiting factor for paddy rice production in upper areas of the plains. No significant variations (P<0.05) in the stream flows of Chimala River were observed between 1960 and 1993 as a result of upland degradation. It is therefore concluded that upland degradation has contributed significantly to land use changes/degradation occurring in the plains that calls for more efforts to safeguard land resources in the uplands by concerned stakeholders
Soil fertility assessment and microbial enhanced solubility of Minjingu phosphate rock in neutral to slightly alkaline soils of Kongwa district
(Sokoine University of Agriculture, 2023) Nhunda, Daniel Masumbuko
To optimize production of maize and other crops, assessment of soil fertility should be done in agricultural areas from which cite specific fertilizer recommendations will be established. This study was conducted in selected fields of Kongwa district in Dodoma Region to assess the soil fertility status and maximize availability of Phosphate from Minjingu phosphate rock (MPR) for maize production through the use of phosphate solubilizing bacteria (PSB). The specific objectives of the study were to determine the levels of N, P, K, S, Mg, Ca, Na, Zn, Cu, Fe and Mn in soils and evaluate capability of phosphate solubilizing bacteria (PSB) on enhancing P availability from Minjingu Phosphate Rock (MPR) and evaluate field characteristics in slightly acid to neutral soils. Assessment of soil fertility status was done by analysing soils from twenty-four maize growing areas of Kongwa district. Composite soil samples of top soils (0 – 20 cm depth) were collected for physical and chemical analysis. Organic carbon was determined by the Walkley-and Black wet oxidation method (Nelson and Sommers, 1982) and total nitrogen (TN) by the micro-Kjeldahl procedure (Loria et al., 2005). Available P was extracted using Bray-1 and Olsen methods of Bray and Kurtz (1945) and measured by Spectrophotometer following colour developed by molybdenum blue method (Murphy and Riley, 1962). Exchangeable bases were extracted by ammonium acetate saturation method (Thomas, 1986) and cation exchange capacity was determined from NH 4+ saturated soil colloids and displaced using 1 M KCl, then determined by Kjeldahl distillation method for estimation of cation exchange capacity (CEC) of the soil (Robertson and Philip et al., 1999). Extractable sulphur (SO4 2- S) was extracted using calcium monophosphate (Ca(H 2 PO 4 ) 2 .H 2 O), then determined by the turbidimetric method as described by Moberg (2001). The EC for soil samples from Kongwa was measured by using EC meter in a 1:2.5 soil: water (or CaCl 2 for pH only) extract as described by McLean, (1982).Extractable metallic micronutrients e.g., Cu, Fe, Zn and Mn, were extracted by diethylenetriaminepentaacetic acid (DTPA) as described by Lindsay and Norvell (1978). Results indicated that 48% of the sampled fields were sandy clay loam, 26% were sandy loam and the remaining whad a clay or loamy sand textural classes. Soil pH ranged from extremely acid (3.52) to moderately alkaline (7.7), organic carbon ranged from very low to medium (0.19-1.60%) and total N values were very low to low (0.01-015%). Also, results indicated 42% of soils had P deficiency and 16.7% with inadequate S. In addition, 45.8% of the soils had inadequate exchangeable K and exchangeable Mg were very low to high (0.29-4.06cmol (+) kg -1 ). Exchangeable Ca was low to very high (1.06 to 10.04 cmol (+) kg -1 ) with favourable base saturation for crop production. The CEC ranged from very low (2.62cmol (+) kg -1 ) to medium (18.9 cmol (+) kg -1 ). Extractable micronutrients such as Cu, Fe, and Mn were adequate but Zn was inadequate in 58% of the soils. The study area had poor soil fertility is poor with deficiencies in N, P, K, Zn, Mg, and Ca, hence calling for proper management to improve crop production. Phosphorus (P) is one of the major growth-limiting macronutrients required for proper plant growth and it is contained within nucleic acids, enzymes, coenzymes, nucleotides, and phospholipids. One of the ways to replenish P in soils is the use of inorganic fertilizers such as Minjingu Phosphate rock. The challenge is that, phosphate rock (PR) generally requires P-deficient acidic soils with pH of less than 6.2 for P to be released and become available for uptake. Application of PR in neutral to slightly alkaline to soils (pH >6.2) is therefore discouraged since PR solubility is very low in such soils and therefore can not supply sufficient available P to plants. Phosphate solubilizing bacteria have a capability among others, of producing organic acids which in turn lowers the local acidity of the soil in which they operate. The lowering of the pH will/may bring about right conditions for solubility of MPR . Maize trials were established in two villages (Nghumbu and Mlali) of Kongwa District to assess effectiveness of PSB in solubilizing MPR in neutral to slightly alkaline soils and two factors were tested, which are field characteristics (in which treatments were sites), the second factor was PSB co-applied with MPR. Maize trials were established using randomized complete block design (RCBD), the seven sites ,PSB inoculum co-applied with different rates of Minjingu phosphate rock (MPR) (0 – 60 kg ha -1 ). Limiting nutrients such as N and S were corrected then Minjingu RP was applied as basal fertilizer during planting by placing it below the seed and covering with a thin layer of soil followed by a co-culture of PSB inoculant at 5 mL (10 9 bacteria per litre) poured around each plant four days after emergence. Maize plants were harvested at maturity then grain and straw samples were analysed for N, P and K content, phosphorus uptake and phosphorus use efficiency were calculated. Using the soil data, it was found that Nitrogen was the main limiting nutrient in all seven fields. The limiting nutrients in Nghumbi were N and K while N, P, K and Zn were limiting nutrients in Mlali village. In the trial fields, the main effect of fields’ characteristics indicated that the performance of maize and its analyzed parameters (N, P, K, S, Mg, Ca, Na, Zn, Cu, Fe and Mn) were significant (P < 0.001) across the fields reflecting heterogeneity in nutrient levels. There was no significant effect of PSB treatments on maize grain yield and straw yield. Results also did not show significant (P =0.427) interaction effects of field characteristics and treatment combinations on the measured variables in maize because of drought experienced in the study area. The findings of the present study, apart from setting site-specific fertilizer recommendations, also suggest that the performance of maize in the study area depends on the soil nutrient status, especially for native P, N, and K. The studied soils need external nutrient inputs and proper management to optimize crop production and more research is recommended on PSB for more than one season in neutral to slightly alkaline soil before ascertaining the technology to farmers because in this season PSB did not enhance solubility of MPR due to drought experienced in the study area.
The use of coal ash from power plants as a soil conditioner
(University of Nottingham, 2015) Sanga, Hilda Gerald
The disposal of coal ash, produced in large quantities by power plants as a by-product of coal combustion, is a significant environmental concern. Coal ash can be used as an agricultural soil conditioner because of its liming potential and the presence of many essential plant nutrients. However, recommendations for the agricultural use of coal ash should be based on sound knowledge of the coal ash characteristics, particularly the concentrations of potentially toxic elements (PTEs) in the ash. Due to the uptake of PTEs by crop plants it may pose risks to human health following the consumption of food crops. The aim of this study was to evaluate the potential for the safe application of power station derived coal ash to soil as a beneficial disposal route. The specific objectives included; (i) testing the variability of fly ash obtained from different sources in the UK, Czech Republic and Tanzania, (ii) quantifying the short- and long-term changes in soil characteristics induced by applications of ash, (iii) determining the effects of coal ash on soil enzyme activities, (iv) quantifying the utility of coal ash as a fertilizer by evaluating its effect on growth and yield of wheat and (v) assessing risks of long-term use/multiple applications of coal ash to arable soils. Coal ash from the Czech Republic, the UK and Tanzania was characterized; the latter two were used in pot experiments to determine their effects on soil enzyme activities, wheat growth and PTE uptake when added to two contrasting soil types (woodland and arable sandy loams). Two incubation experiments were undertaken to quantify short- and long-term effects of the coal ashes on soil characteristics. Calculations were also performed to evaluate the probable risks of increased contamination of soil and plant material as well as human ingestion of PTEs following repeated applications of fly ash to arable soils. Coal ashes from each source contain varying quantities of essential nutrients and PTEs due to differences in coal ranks and the combustion conditions of the power plants producing each ash. Different batches of ash from the UK and from Tanzania had different characteristics, despite coming from the same industrial source within the respective countries. Application of the first batch of ash collected in the UK (UK1) to woodland soil increased the soil pH, soil respiration and nutritional status during a two-year incubation experiment. Soil amendment with high UK1 ash concentrations (8-16%) contaminated the soil with PTEs through the experiment. In a four-month incubation experiment, the effects of different coal ashes applied to acidic woodland soil varied depending on the characteristics of each individual ash and the amount of ash applied. In a pot experiment designed to evaluate the effect of coal ash on microbial activities, soil amendment with the UK1 ash increased the pH of woodland and arable soils, while application of the TZ1 ash reduced the pH of both soils. Application of low concentrations (0-4%) of UK1 ash to both soils increased dehydrogenase and urease activities and wheat growth while application of TZ1 ash at high concentrations (8-16%) inhibited the enzyme activities. In pot experiments to evaluate the effects of ash on wheat growth, application of 0- 32% of the UK1 ash to woodland and arable soils increased soil pH while application of the TZ1 ash at 0-32% decreased the pH of both soils. Soil amendment with 0-4% of either UK1 or TZ1 ash increased the concentrations and extractability of nutrients and wheat growth and yield, but application of 16-32% of both ashes to both soils contaminated the soils and wheat plants with PTEs. Despite PTE uptake by plants, grain PTE concentrations were within the FAO/WHO 'safe' limits for ingestion, except for As and Cd in grains from plants grown in woodland soil amended with the highest concentrations of UK1 and TZ1 ash respectively, which were both present in higher than acceptable concentrations. Soil and plant concentrations and human consumption of selected PTEs (As, Cd, Cr, Pb and Zn) were calculated following simulated annual applications of TZ1 ash to an arable soil for five consecutive years. This showed that, even when residual contamination over a 25-year period was considered, applications of 2% ash to the soil are unlikely to breach 'permissible' standards for soil, wheat grain contamination and human dietary intake of PTEs, which were far below 'permissible' limits. It would be possible to apply ash with similar characteristics to TZ1 more frequently or over more than five cropping cycles. In conclusion, coal ash can be used as an agricultural soil conditioner; however, low concentrations (0-4%) and the strategic agronomical use of ash, specifically targeting problematic soils, are highly recommended for future studies.
Assessment of the fertility status of soils of rice growing areas of Same District, Kilimanjaro Region, Tanzania.
(Sokoine University of Agriculture, 2003) Amur, Nyambilila
This study was conducted to assess the fertility status of the soils of rice growing areas of Same district. Thirty soil samples were collected from ten different sites where rice is grown. Following laboratory analysis, three bulk soil samples were collected from Kisiwani, Ndungu and Kihurio for pot experiments. The laboratory analysis included determination of total N, organic carbon, P by Bray 1 and Olsen methods, and exchangeable bases by ammonium acetate saturation. The micronutrients were determined by extracting with 0.005M DTPA at pH 7.3. The response of rice (Oryza saliva L) variety super SSD5 to N, P and K, as well as to different levels of Zn were assessed in a glasshouse experiment where plants were grown for 56 days. The harvested plant samples were analysed for N, P, K, Ca, Mg, Zn and Fe using the HNO3-H2O2 wet digestion procedure. The results showed that all the soils in this study were deficient in N. About 53% of the soils had low available P. All the soils had adequate levels of K, Ca, Mg and Na, with the exception of soils from Ndungu, which had a low K, supply. Also, most of the soils had low Zn levels, and only two sites had adequate Zn levels. Soils from Mbugani had low Fe while the rest had adequate Fe and Cu. The glasshouse experiments showed that application of N, P and K increased rice dry matter yields in all the soils used. It was further revealed that Zn supplementation in addition to NPK also increased rice dry matter yields further. The results also indicated that the uptake of each nutrient applied was consistent with the dry matter yields increases. It was concluded that most of the soils under rice cropping in the district were deficient in N, P and Zn and required fertilisation using these nutrients. Iron was also required in Mbugani soils, whichiii were deficient of this element. Field experiments are recommended to confirm these initial findings.
Effects of limestone, Minjingu phosphate rock and green manure application on improvement of acid soils in Tonga Butare, Rwanda
(Sokoine University of Agriculture, 2003) Nabahungu, Leon Nsharwasi
A study was conducted under pot and field conditions to assess the effects of limestone, Minjingu Phosphate Rock (MPR) and green manures (GMs) on maize yield, soil properties and nutrient uptake. The treatments tested in the greenhouse experiment were four rates of limestone applied either alone or in combination with MPR and/or green manures. In the field experiment, 13 treatments were tested namely an absolute control, recommended rate of NPK and burned lime, NP and limestone, combinations of any two of the following materials: limestone, MPR, Tithonia GM, Tephrosia GM, and combinations of three of these amendments. Soil analysis at the beginning of the experiment revealed that the soil was deficient in N, P, and K, had low levels of Ca and Mg and toxic levels of exchangeable AI. Application of GMs improved the supply of N and K appreciably while limestone played a great role in reducing exchangeable AI. A significant contribution of P was from MPR. A combination of MPR, GMs and limestone supplied ample amounts of N, P, K, Ca, Mg and reduced exchangeable AI and hence resulted into high yield. However, high rates of limestone decreased DM yield and nutrient uptake in the treatment with three amendments. A significant increase in DM yield was obtained in pots, which received a combination of low rate of limestone (1/4 of the lime requirement), MPR and GMs. In general Tithonia application gave higher yields than Tephrosia. These results were consistent with the higher quality of Tithonia biomass relative to Tephrosia biomass. The green manures in combination with MPR increased P uptake significantly. Nutrient concentration data from both field and pot experiments indicated serious deficiencies of P, K and N consistent with soil analysis data but Ca, Mg, Zn and Cu were in the sufficiency range. Furthermore, the results indicated that using a combination of moderate rates of limestone, MPR and GMs is the best strategy in improving acid soils in Tonga, Rwanda.
Screening coalmon bean [Phaseolus vulgaris l. savi] genotypes adapted to low soil phosphorus
(Sokoine University of Agriculture, 2006) Mourice, Sixbert Kajumula
Two screen house pot experiments were conducted to identify bean genotypes, diverse in their places of origin and seed size, based on vegetative growth and P uptake and final grain yield for adaptation to low phosphorus. Three phosphorus levels; low P (0 added P), medium P (40 mg P/kg soil) and high P (160 mg P/kg soil) were main plots whereas 27 genotypes were subplots, in a split-plot laid out in a completely randomised design. The test soil was very fine, kaolinitic Kanhaplic I-Iaplustult. Out of 27, seven bean genotypes were further evaluated for yield components and final grain yield at low P in the same soil. Shoot biomass, root biomass, shoot P concentration and P uptake increased with increased P supply and genotypic variability in these parameters was significant (P < 0.05). Genotypes G92, PRETO 143, MILENIO, VEF 88(40), BAT 477, A785, ANT 22, DOR 714 and AFR 708 performed better than other genotypes at low P level; also their response to P addition was significant. It was revealed that P was a major limiting factor to bean growth in the soil used for the experiment. Number of pods/plant increased significantly with increase in P levels and was correlated with grain yield at low P and adequate P. P treatments did not affect the seed size of genotypes. Genotypes BAT 477, MILENIO, DOR 714 and A785 had significantly higher grain yield than other genotypes at low P and may be favoured in the selection process. Although genotypes produced some grain yield at low P, soil fertility improvement by applying medium P or appreciable amounts of organic manure may improve yields and increase productivity per unit area.
Screening coalmon bean (Phaseolus Vulgaris L. Savi) genotypes adapted to low soil phosphorus
(Sokoine University of Agriculture, 2006) Mourice, Sixbert Kajumula
Two screen house pot experiments were conducted to identify bean genotypes, diverse in their places of origin and seed size, based on vegetative growth and P uptake and final grain yield for adaptation to low phosphorus. Three phosphorus levels; low P (0 added P), medium P (40 mg P/kg soil) and high P (160 mg P/kg soil) were main plots whereas 27 genotypes were subplots, in a split-plot laid out in a completely randomised design. The test soil was very fine, kaolinitic Kanhaplic H0aplustult. Out of 27, seven bean genotypes were further evaluated for yield components and final grain yield at low P in the same soil. Shoot biomass, root biomass, shoot P concentration and P uptake increased with increased P supply and genotypic variability in these parameters was significant (P < 0.05). Genotypes G92, PRETO 143, MILENIO, VEF 88(40), BAT 477, A785, ANT 22, DOR 714 and AFR 708 performed better than other genotypes at low P level; also their response to P addition was significant. It was revealed that P was a major limiting factor to bean growth in the soil used for the experiment. Number of pods/plant increased significantly with increase in P levels and was correlated with grain yield at low P and adequate P. P treatments did not affect the seed size of genotypes. Genotypes BAT 477, MILENIO, DOR 714 and A785 had significantly higher grain yield than other genotypes at low P and may be favoured in the selection process. Although genotypes produced some grain yield at low P, soil fertility improvement by applying medium P or appreciable amounts of organic manure may improve yields and increase productivity per unit area.
Influence of cover crops on nitrogen availability, soil moisture content and maize yield under sub humid climate of Morogoro, Tanzania
(Sokoine University of Agriculture, 2005) Kalumuna, Matilda Charles
A study was conducted in Morogoro Tanzania, for 3 consecutive years to evaluate the influence of cover crops planted in short rains on nitrogen (N) availability, soil moisture and grain yield of the subsequent maize crop planted in the long rains. The cover crops namely cowpea (Vigna unguiculata [L] Walp.), lablab (Lablab purpureus, L.), mucuna (Mucuna pniriens) and pumpkin (Cucurbita maxima') were evaluated against weed and bare fallows in Randomized Complete Block Design (RCBD) replicated three times. Cover crops residues had N content 2%. Pumpkin, although not a legume, had high quality residues, having 2.1% N and higher P (0.25% P) and base content than other cover crops. Mucuna was the only cover crop that produced an average biomass above the threshold of 2 Mg DM ha'1. Mucuna biomass was significantly higher (P < 0.05) than that of the other cover crops, ranging from 2.7 to 5.1 Mg DM ha'1, with good short rains and accumulating 63 to 118 kg N ha'1. At the end of the short rainy season, mineral N after mucuna increased by 2 to 30% and was significantly higher (P < 0.05) than after the other cover crops. Seventeen and 35% of N accumulated in pumpkin and cowpea residues was released in the first 7 days of incubation, respectively. These were significantly higher than the 4 and 6% accumulated N in lablab and mucuna residues, respectively. At 35 days of incubation, mineral N released from lablab, pumpkin and mucuna residues was 19, 34 and 31% of the applied amount, respectively. Mucuna and lablab significantly increased soil moisture reserve in the 40 - 60 cm soil layer (P < 0.05) by 9 mm in the short rainy season whereas pumpkin and weed fallow reduced it by 3 and 4 mm, respectively. In the long rainy seasons, mucuna and lablab reduced runoff from 30 - 45% to 6 - 15% of rainfall. Mucuna significantly increased the number of maize plant silking (P < 0.05) at 53 days after planting by 15 - 17% over weed fallow and maize grain yield by 3 - 4 fold in seasons with insufficient long rains. It is recommended that in order to increase maize production in the sub humid area of Morogoro, mucuna should be planted in the short rains instead of leaving the land under weed fallow and supplemental mineral N fertilizer should be topdressed at 28 to 35 days after maize planting.
Carbon sequestration and nitrogen addition in selected soils of Morogoro, Mbeya and Ruvuma under maize-soybean intercropping and rotations
(Sokoine University of Agriculture, 2022) Hamadi, Said
This study was conducted in some selected soils of Morogoro (Magadu) and Mbeya (Uyole) regions of Tanzania to classify and characterize their properties. Two representative pedons (SUARAT-P1 and UYOLE-P1) were dug and described using FAO guidelines clarifying morphological features, physico-chemical properties and genesis. The representative pedons were geo-referenced using Global Positioning System (GPS) receiver. A total of nine (9) genetic soil horizons were identified from both sites and samples from each horizon collected for physical and chemical analyses. Soils from both sites were very deep and topsoil moist colors ranged from hue of 7.5YR to 10YR with chroma of less than 3 in SUARAT-P1 and UYOLE-P1 pedons. Soil structure ranged from strong fine crumbs in topsoils to medium coarse sub-angular blocks in subsoils of SUARAT-P1 while UYOLE-P1 had weak fine sub-angular blocks in topsoils and subsoils. The SUARAT-P1 had sandy clay (SC) texture in topsoil and clay texture in subsoil while UYOLE-P1 was sandy loam (SL) in topsoil and sand clay loam (SCL) in subsoil. Soil reaction were slightly acid to very strongly acid in SUARAT-P1 (pH 6.54 - 4.46) whereas UYOLE-P1 were slightly acid to neutral in the subsoil horizons (pH 6.35 – 7.32). Organic carbon ranged from very low to low (0.12- 0.95%) in SUARAT-P1 from 0-23 cm and medium (1.5%) from surface to 25 cm depth in UYOLE-P1. Nitrogen levels were very low to low (0.05 - 0.12%) in both sites, whereas available P ranged from low (0.30 mg kg - 1 ) to medium (8.55 mg kg -1 ) in both pedons. The figures for soil OC and N will be used as baseline to forecast SOC and N sequestration potential in selected study sites. CEC of SUARAT-P1 was medium ranging from 12.4 to 23.2 cmol(c) kg -1 , whereas UYOLE-P1 was medium to high (15 – 34 cmol(c) kg -1 ). The figures for soil OC and N will be set as baseline for SOC and N sequestration studies in the next chapters. In SUARAT-P1, topsoil BS was high (> 50%) and low (< 50%) in the subsoil while UYOLE-P1 registered high BS throughout its profile depth. As diagnostic horizons for soil classification, the SUARAT-P1 had an ochric epipedon overlying a kandic horizon and classified according to USDA Soil Taxonomy as Typic Kandiustults, while UYOLE-P1 had an ochric epipedon over a cambic horizon and was named as Andic Dystrudepts corresponding respectively to Haplic Lixisols and Eutric Andic Cambisols in the WRB for Soil Resources. The results have indicated that, studied soils are less fertile with possible reconstitution through land and crop management practices which include but not limited to no-tilling or conservation tillage, manuring and proper fertilizer application; residue retention, possible fallowing, liming for potential buffering of soil pH especially at SUARAT-P1 and crop rotation and intercropping with leguminous crops.
Effect of tillage, farmyard manure and potassium rates on the perfomance and profitability of cassava in selected districts of Kagera, Tanzania
(Sokoine University of Agriculture, 2022) Merumba, Mgeta Steven
In Tanzania cassava (Manihot esculenta, Crantz) is the second most important food security crop after maize. Its roots produce at least 30% of starch on dry weight basis, which is the major source of dietary energy, different industrial products like sugar, pharmaceutics, alcohol, textile products and animal feeds. In the Lake zone of Tanzania, cassava is grown in all regions, which account for 23.7% of the total cassava production in the country. Despite the importance of cassava in food systems there is decreasing yield. For example, the national average root yield is 10 MT ha -1 compared to the potential yields of 25 - 80 MT ha -1 , whereas in Kagera region, average yield in farmers’ fields is about 7.80 MT ha -1 . The low yield is due to, among others, increased susceptibility of the crop to cassava mosaic disease (CMD) and cassava brown steak disease (CBSD), declining soil fertility and poor agronomic practices. In the Lake zone, cassava is planted on ridges or on flat tillage but little information exists on the performance of cassava when planted on ridges or on flat tillage. In addition, cassava responds well to farmyard manure and inorganic fertilizers. But scant information exists on the performance of cassava upon use of different rates of FYM and potassium fertilizer, specifically based on Kagera region climate and soils. This study, therefore, aimed to determine the effects of tillage methods and application of different rates of FYM and potassium fertilizers on the performance and profitability of cassava in Bukoba, Missenyi and Biharamulo districts of Kagera region. The specific objectives of this study were to: (i) characterize and classify the soils of the study area and assess their suitability for cassava production, (ii) assess the current soil fertility status of farmers’ fields in the study sites, (iii) determine the effects of tillage methods, farmyard manure and potassium rates on soil moisture conservation and relationship with cassava root yield, (iv) determine the effects of tillage methods, FYM and potassium rates on cassava growth, yields and root quality, and (v) evaluate the economics of using farmyard manure and potassium fertilizer rates in cassava production in the study area. To achieve objective i, pedological characterization, which involved reconnaissance field survey in Bukoba, Missenyi and Biharamulo Districts was carried out. Soil profile description and soil sampling for laboratory analysis were done according to the FAO Guidelines for Soil Description. The soils of the study sites were classified to the family level of the USDA Soil Taxonomy and to tier-2 of the FAO World Reference Base for Soil Resources. Soil suitability assessment of the experimental sites was done using a simple limitation method based on the FAO Framework for Land Evaluation. The results revealed that the soils of Bukoba and Biharamulo sites had similar morphological properties, which were different from Missenyi site. But all differed in their physical, chemical and generic properties. Based on the USDA Soil Taxonomy, Bukoba and Biharamulo sites were classified as “Typic Kandiudults”.and as “Haplic Ferralic Acrisols”, and “Chromic Ferralic Acrisols” respectively according to FAO World Reference Base for Soil Resources. Missenyi site was classified as “Typic Endoaquolls” and “Fluvic Gleyic Phaeozems” according to USDA Soil Taxonomy and FAO World Reference Base for Soil Resources, respectively. Moreover, Missenyi and Biharamulo sites were evaluated as marginally suitable and the Bukoba site as moderately suitable for cassava production. Therefore, soil fertility management strategies are recommended in each studied site for optimum cassava yields. To achieve objective ii, two wards and one village in each ward were selected in Bukoba, Missenyi and Biharamulo districts. A total of thirty-three fields were selected (five farmers' fields in each village and one experimental field in each district). Composite soil samples at 0- 20 cm depth were taken using a using a zigzag pattern over the whole field's area and analyzed. Correlation analyses among soil chemical properties were performed using IBM SPSS Statistic 20 statistical package. Soil fertility index (SFI) and identification of limiting nutrients were used to assess the fertility status of selected farmers’ the fields. Results indicate that the studied fields had poor fertility to good fertility. Phosphorus and potassium deficiencies were widely spread in Bukoba district while N and S deficiencies were widely spread in Missenyi district and N, P and K deficiencies were widely spread in Biharamulo district. There were positive and negative and significant (p≤ 0.05) and highly significant (p≤ 0.01) correlations among the soil chemical properties in each district. Therefore, site specific soil fertility management practices are recommended based on limiting nutrients. To achieve objective iii, one cassava field trial was established in each selected district (Bukoba, Missenyi and Biharamulo) during 2018/19 and 2019/20 cropping seasons using the split-plot design. The treatments were arranged in Randomized Complete Block Design (RCBD) with three replications. Tillage methods (flat tillage, open ridging and tied ridging) were the main plots and fertilizer types and rates [farmyard manure (FYM) alone at 4 MT ha -1 or FYM alone at 8 MT ha -1 , nitrogen (40 kg N ha -1 ) + phosphorus (30 kg P ha - 1 ) + potassium at 40, 80 or 120 kg K ha -1 and the combination of FYM alone at 4 MT ha -1 or FYM alone 8 MT ha -1 + potassium at 40, 80 or 120 kg K ha -1 ] were the sub-plots. Soil moisture was monitored starting from 1 week after the last rain event at an interval of 2 weeks up to the first rain event of the following season. The soil samples in cores were weighed and placed in the drying oven at 105 o C to constant weight. The soil moisture content (%) in each soil sample was determined gravimetrically. The results showed that tie and open ridges conserved significantly (p≤0.05) more soil moisture ranging from 24 to 58% (Bukoba district), 10 to 45% (Missenyi district) and 10 to 32% (Biharamulo district) than flat tillage ranging from 22 to 43% (Bukoba district), 8 to 37% (Missenyi district) and 7 to 27% (Biharamulo district) in both cropping seasons. However, tied ridges conserved significantly (p≤0.05) more (11 to 58%) soil moisture than open ridges (10 to 47%) in the medium and high rainfall areas as opposed to the low rainfall area. The results also indicate that the use of FYM significantly (p≤0.05) conserved more soil moisture (16.54 to 63.48%) than inorganic N, P and K fertilizers (12.27 to 53.60%). In addition, use of FYM alone at 8 MT ha -1 conserved significantly (p≤0.05) more soil moisture (19.94 to 62.16%) than FYM alone at 4 MT ha -1 (16.80 to 58.33%). Moreover, there was a significant (p≤0.05) association between soil moisture conservation and changes in cassava root yields. Therefore, planting cassava on ridges together with use of high rates of FYM (8 MT ha -1 ) is indispensable for adequate soil moisture conservation and improving cassava root yields. To achieve objective iv, data on daily rainfall (mm) were collected in each experimental site. Data on root and biomass yields (MT ha -1 ) were collected from the net plot from established trials described in objective ii above. About 500 g of cassava roots from each treatment were peeled and oven dried at 105 o C to constant weight for determining dry matter content gravimetrically and root starch content in each treatment was determined. In addition, the post-harvest soil samples and cassava leaf samples were collected from the control plots and the plots that received the combination of FYM at 8 MT ha -1 and potassium (K) at 40 or 120 kg ha -1 for determining the concentration of Nitrogen, phosphorus and K and soil pH. The results indicate that planting cassava on ridges gave significantly (p≤0.05) higher (18.98 - 34.84 MT ha -1 ) cassava fish root yield than on flat tillage (16.86 - 29.74 MT ha -1 ). However, use of ridges or flat tillage did not show significant (p≤0.05) difference in starch and dry matter contents in cassava roots, soil pH, and concentration of N, P and K in the soil and cassava leaves and sprouting of cassava plant. Combined use of FYM at 4 MT ha -1 or FYM at 8 MT ha -1 and potassium at 40, 80 or 120 kg K ha -1 significantly (p≤0.05) improved cassava growth and increased cassava fresh root yields (14.56 - 39.94 MT ha -1 ). Also, combined use of FYM at 4 MT ha -1 or FYM at 8 MT ha -1 and potassium at 40, 80 or 120 kg K ha -1 ; significantly (p≤0.05) improved cassava growth and increased cassava fresh biomass yields (9.36 - 32.86 MT ha -1 ). Combined use of FYM at 8 MT ha -1 and potassium at 120 kg K ha -1 or FYM at 8 MT ha -1 and potassium at 40 kg K ha -1 increased the concentration N, P and K in the soil and N and K in cassava leaves. Therefore, planting cassava on ridges and combined use of FYM at 4 MT ha -1 and potassium at 80 or 120 kg K ha -1 is desirable for improving cassava growth, increasing biomass and root yields and increasing root quality. Combined use of farmyard manure at 8 MT ha -1 and potassium at 120 kg K ha -1 is desirable for increasing the concentration of N and K in the soil and in cassava leaves. However, for the resource-poor farmers who cannot afford the high rate of K, combined use of farmyard manure at 8 MT ha -1 and potassium at 40 kg K ha -1 can be used. To achieve objective v, yields data collected from the established trials as described in objective iii above were used to perform partial budget analysis, whereby, the gross values were estimated using the adjusted yields at market price for cassava and fertilizers. Costs and benefits were calculated on a hectare basis. All variable costs were summed up to give total variable cost (TVC). Thereafter, the net benefits (NB) ha -1 of the tested treatments were calculated and used to assess the profitability of each treatment. In addition, benefit- cost ratios (BCR) of the tested treatments were compared to the acceptable value of greater than 2 for the technology to be adopted by farmers. The results indicate that in both cropping seasons, and at all studied sites, all tested fertilizer rates gave acceptable BCR of greater than 2, implying that all the fertilizer types and rates tested in this study could be used in cassava production in the study areas. In addition, the results on net benefit indicate that use of combination of FYM at 8 MT ha -1 and potassium at 80 kg K ha -1 gave higher net benefit than the other fertilizer types and rates, and is therefore, desirable for increasing cassava root yield and economic benefit in the study area. However, for the resource-poor farmers, combined use of farmyard manure at 8 MT ha -1 and potassium at 40 kg K ha -1 can still be adopted in the study area because, for some reason, not all the famers can afford the best treatment. The major conclusions drawn from this study are that the soils of Bukoba and Biharamulo sites have similar morphological properties, which are different from Missenyi site. However, all soils differ in their physical, chemical and generic properties. According to the USDA Soil Taxonomy, the soils of both Bukoba and Biharamulo sites were classified as “Typic Kandiudults” and as “Haplic Ferralic Acrisols” and “Chromic Ferralic Acrisols”, respectively, according to FAO World Reference Base for Soil Resources. The soil of Missenyi site was classified as “Typic Endoaquolls” according to USDA Soil Taxonomy and as “Fluvic Gleyic Phaeozems” according to FAO World Reference Base for Soil Resources. Missenyi and Biharamulo sites were both evaluated as marginally suitable while Maruku site was evaluated as moderately suitable for cassava production due to soil fertility constraints and hence sustainable cassava production in these areas would need interventions for soil fertility improvement. The soil fertility status of the studied fields ranged from poor fertility to good fertility whereas, P and K deficiencies were widely spread in Bukoba district while N and S deficiencies were widely spread in Missenyi district and N, P and K deficiencies were widely spread in Biharamulo district. Use of ridges conserved more soil moisture than use of flat tillage, and use of farmyard manure at 8 MT ha -1 conserved more soil moisture than combined use of inorganic N, P and K fertilizers or use of farmyard manure at 4 MT ha -1 . Moreover, plating cassava on ridges together with combined use of FYM at 4 MT ha -1 and potassium at 40, 80 or 120 kg K ha -1 improved cassava growth and increases cassava root and biomass yields than use of flat tillage together with the same fertilizer rates. Combined use FYM at 8 MT ha -1 and potassium at 80 or 120 kg K ha -1 or combined use of inorganic N at 40 kg ha -1 , P at 30 kg ha -1 and K at 120 kg ha -1 increased the contents of starch and dry matter in cassava roots and combined use of FYM at 8 MT ha -1 and potassium at 40 80, or 120 kg K ha -1 increased concentration of N, and K in the soil and cassava leaves. In terms of profitability, combined use of FYM at 8 MT ha -1 and potassium at 80 kg K ha -1 gave higher net benefit than the other fertilizer types and rates tested in this study and is therefore, desirable for increasing cassava root yield and economic benefit in the study area. However, for the resource-poor farmers, who cannot afford the best treatment, combined use of farmyard manure at 4 MT ha -1 and potassium at 80 kg K ha -1 can still be adopted.
Evaluation of the potential of green manure and plant extracts for the control of witchweed (strig a asiatica l. kuntze) in upland rice (oryza saliva l.) in Kyela, Tanzania
(Sokoine University of Agriculture., 2004) Mohamed, Juma Kayeke
Striga asiatica is a serious problem in upland rice in Kyela Tanzania. The use of inorganic nitrogen fertilizer urea assures control of the weed. Resource poor farmers cannot adopt the technology due to unavailability and higher prices of inorganic fertilizers. Therefore, the use of green manure available in upland rice fields will be a plausable alternative. Three experiments were conducted to evaluate the potential of green manure and plant extracts for the control of Striga asiatica (L.) Kuntze on upland rice (Oryza sativa L). These experiments aimed at evaluating the decomposition of the green manure, determining the effect of the green manure and inorganic fertilizer on Striga and rice yield and determining the influence of green manure and plant extracts on the germination of Striga. Decomposition of roots and shoots of Crotolaria ochlroleuca G. (sunhemp), Mimosa invisa L.(CoIla), and Cassia obtusifolia L.(Sicklepod) was determined. Results showed that by the 2nd week shoots had lost 51% of the biomass while by the 6lh week roots had lost 50% of the biomass. Then inorganic fertilizer urea at 0 N, 25 kg N ha'1 and 50 kg N ha'1 was superimposed in green manure plots. Generally, it was found that Striga infestation was reduced by 100% while the yield of rice increased from 1238 kg ha’ to 2846 kg ha'1. However, the residual effect of green manures did not reduce Striga but increased rice yield. High benefit per unit cost was realised on when C. ochlroleuca was combined with 50 kg N ha'1). Green manure application methods (ploughing under, mulch) was also superimposed with inorganic fertiliser urea (0 N, 25 kg N ha' 1 and 50 kg N ha '). Results showed that there was no significant difference between mulch and ploughing under on Striga except for rice grain yield. Mulch was found toiii be more economical than ploughing under. The potential of green manure to stimulate Striga germination, plant extracts to suppress Striga germination and application methods was also determined in the laboratory and field. Striga germination was found to be in the order C. ochlroleuca C. obtusifolia > M. in visa (both field and laboratory). Plant extracts were collected from C. ochlroleuca, M. invisa, C. obtusifolia, Vernonia amygdalina Del. (bitter leal), Neuritania niitis, Dolichos kilimandcharis and Gnidia kraussiana Mcisn. (yellow heads). It was found that Striga seed germination was reduced where D. kilimandcharis and G. kraussiana were found to be effective in suppressing Striga seeds germination. Seed hardening was selected as a good application method. Crotalaria ochroleuca and C. obtusifolia were recommended for Striga control and improvement of soil fertility in Kyela.
Use of minjingu phosphate rock combined with different organic inputs in improving phosphorus availability and maize yields on a chromic acrisol in Morogoro, Tanzania
(Sokoine University of Agriculture, 2004) Ikerra, Susan Tinkishaba
Phosphorous deficiency in highly weathered soils is one of the causes of low crop yields in Tanzania. Use of Minjingu phosphate rock (MPR) in combination with organic inputs is considered to be a possible option for increasing P availability and crop yields. However, detailed characterization of organic inputs, the effects of organic inputs when used alone or combined with MPR on soil characteristics and, consequently, maize yields, are limited. The objectives of this study were to characterize farmyard manure (FMY), tithonia, lantana and gliricidia and to evaluate the influence of MPR combined with these organic inputs on soil properties, P availability and maize yields from a Chromic Acrisol. The study consisted of incubation, pot and field experiments. Characterization of organic materials showed that manure and tithonia had more P than the critical value for net P mineralization. Tithonia contained the highest amounts of light molecular weight organic acids (LMWOA), oxalic acid being the most dominant. An incubation experiment showed that all organic materials depressed MPR dissolution, and the depressing effect increased with increase in pH, Ca and P content of the materials. Incubation and pot experiments showed that organic materials at 2.27 g kg'1 (5 t ha'1) increased soil pH, exchangeable Ca and decreased exchangeable Al. All organic materials increased labile P pools and reduced P adsorption maximum and P affinity in the incubation and field experiments. This resulted in increase in available P and consequently, in maize dry matter yields (DMY). Under field conditions tithonia increased soil pH, exchangeable Ca and oxalic acid concentration, and decreased exchangeable Al. Tithonia decreased P sorption and increased total labile P, consequently increasing maize yields. Thedecrease in P adsorption increased with tithonia rates, with the rate of 7.5 t ha'1 resulting in the largest agronomic optimum. MPR was superior to TSP (80 kg P ha'1) in increasing pH, Ca, oxalic acid and in reducing exchangeable Al. Both sole MPR and sole TSP reduced P adsorption but the influence of MPR was greater than that of TSP. Tithonia at 7.5 t ha'1 had similar P adsorption maximum to sole MPR at 80 kg P ha'1. Combining MPR at 40 kg P ha’1 with tithonia at 7.5 t ha'1 had adsorption maximum similar to that of sole tithonia at 7.5 t ha'1 or MPR at 80 kg P ha'1. Both MPR and TSP increased Ca and P uptake and maize yields in pot and field experiments. MPR was superior to TSP in supplying Ca, oxalic acid and in increasing pH in all seasons. Combining MPR with tithonia had a higher RAE in two out of the three seasons than that under sole tithonia or MPR. Organic materials alone or combined with MPR improved soil pH, Ca and decreased exchangeable Al, consequently increasing P availability and maize yields. Combining MPR with organic materials resulted in increase in P availability by reducing P adsorption rather than by enhancing MPR dissolution. Co-application of MPR with tithonia on Chromic Acrisol is recommended. Evaluation of the influence of tithonia on some chemical, physical and biological soil properties under various climatic conditions and for longer periods of time is essential so as to be able to better exploit this resource.
Erosion hazard assessment in the upper ewaso Ng’lro basin of Kenya: application of GIS, USLE and EUROSEM
(Sokoine University of Agriculture, 1999-01-15) Mati, Bancy Mbura
A methodology was developed for assessing soil erosion hazard in the Upper Ewaso Ng’iro basin of Kenya, using Geographic Information Systems (GIS), the Universal Soil Loss Equation (USLE) and the European Soil Erosion Model (EUROSEM). The USLE was used in a GTS environment by creating thematic maps of R, K, L, S, C and P and then calculating soil loss by raster-grid modelling with Arc/Info GRID. The rainfall erosivity factor (R) was derived from relationships between rainfall amount and erosivity using erosion plot data from within the catchment. The nature of the relationship was found to be a function of agro-climatic zones of the region. Mean annual erosivities ranged from 145 to 990 J m"2 hr"1 For a given amount of rainfall, erosivity was higher in zone IV than in the wetter zones 11-111. The soil erodibility factor (K) was estimated using the USLE nomograph and data from laboratory analysis of field samples collected from representative major soil mapping units. The K-values were low to medium, ranging from 0.10 to 0.25 over 84 percent of the basin. The topographic factor (LS) was obtained by creating Digital Elevation Models (DEMs) of the basin with TOPOGRIDTOOL of Arc/Info. These were then used to determine the slope steepness and length factor values, calculated with raster-grid modelling. Although DEMs proved a useful tool, maximum values of both steepness and length had to be set in this reconnaissance study to achieve reasonable results. A finer resolution of input data and a smaller grid cell size are needed for accurate determination. The cover and management factors (C) were obtained by determining the land cover types within the basin using remotely sensed data (SPOT 1 colour composite prints) and ground truthing studies. The factor values were estimated from USLE guide tables and measurements of cover from plots and test sites. Some 70 percent of the basin is covered by rangelands. The conservation practice (P) factor values were estimated from USLE guide tables and then applied to areas where soil conservation had been introduced according to maps obtained from the Ministry of Agriculture. The USLE was validated using data from erosion plots. A value of R2 = 0.645 was obtained between predicted and measured values but the standard error was rather high (e = 5.745 t ha"1 yr"1). Using an annual soil loss of 9.0 t ha"1 yr"1 as tolerance level, some 36 percent of the basin was found to experience unacceptably high erosion rates. Most of this area was communal grazing land and cropland where soil conservation measures had not been applied. A critical land cover type within the grazing land is shrubland, where vegetation cover is less than 40 percent and high erosion risk was predicted and confirmed by field surveys. EUROSEM could not be integrated within a GIS in the time available for research. It was therefore simulated outside GIS environment, where it was applied to Embori and Mukogodo plot data using separate data sets for calibration and validation. Calibration was used to obtain input parameters for saturated hydraulic conductivity, cohesion and Manning’s roughness coefficients. Validation gave correlation coefficients of 0.907 and 0.840 for predictions of storm runoff and soil loss respectively at Embori; the corresponding values for bare soil plots at Mukogodo were 0.895 and 0.577. However, EUROSEM predicted runoff poorly (R2 = 0.570) and failed to predict soil loss at all the vegetated plots at Mukogodo. The model was applied to simulated vegetation covers of barley, maize, grass and forest for a 36.7 mm rainstorm at Embori. The simulated soil losses showed an exponential decrease with increasing cover. At a threshold cover of 70 percent, soil loss diminished to zero under grass and forest and decreased to a minimum value under barley and maize. These results support the USLE simulations, which showed that areas with more than 70 percent cover (such as forest) had a low erosion hazard, even with steep slopes and high rainfall erosivities. This research has demonstrated that GIS can be used with the USLE to assess and quantify erosion hazard, giving results that can be used for conservation planning. EUROSEM can be applied successfully to bare soil and cropland, but application to other land covers requires further investigation. Land cover and topography are the main factors controlling the spatial distribution of soil loss in the Upper Ewaso Ng’iro basin. Future conservation activities should be concentrated on the rangelands.
Effects of green manure and compost amended with phosphate rock on soil properties, yield and quality of amaranth and tomato.
(Sokoine University of Agriculture., 2004) Minja, Ruth R.
A study was conducted in Iringa, Tanzania to evaluate the potential of crotalaria (Crotalaria ochroleuca) green manure and compost applied alone or amended with Minjingu phosphate rock (MPR) as sources of N and P and their effects on selected soil physical and chemical properties, plant nutrient concentration and uptake, yield and some quality attributes. Two field experiments, one for amaranth and the other for tomato were conducted using a split plot design with three replications. Crop cultivars were main plots while fertilizer treatments constituted the sub plots. Two amaranth species (Amaranthus cruenlus and Amaranthus hypochondriacus) and two tomato cultivars, Tanya (determinate) and Tengeru-97 (indeterminate) were used. Fertilizer treatments included crotalaria as green manure, crotalaria + MPR, compost, compost + MPR and NPK which was used as the standard. The results indicated that compost was more effective than crotalaria in increasing organic matter and soil moisture content. Crotalaria contributed more N to the test crops than compost. Amendment of compost or crotalaria with MPR enhanced P supply, plant N and P uptake and relative agronomic effectiveness (RAE). All fertilizer materials were able to supply adequate levels of N and P as required by the two crops at their critical growth stages. The tested materials significantly increased yields, vitamins C and A, and crude protein of the two crops. The yields and nutrient content levels obtained for the two vegetables were within the range reported in literature. There were significant and positive correlations between soft available N, P and yield, protein, calcium, iron, vitamin C and A contents of the vegetables. Keeping quality of the vegetable crops was mostly influenced by their Ca contents probably due to the role of Ca in cell wall synthesis and integrity. Due to its high Ca content, MPR-amended treatments increased the evaluated keeping quality attributes of the test vegetables. It is therefore recommended that the tested organic materials could be attractive sources of N and P in organic production of tomato and amaranth. Application of crotalaria and compost should be supplemented with P sources such as MPR in order to increase their P contents. Soil fertility improvement programmes in this area and others with similar soil properties should include farmers training on proper management of organic materials such as application methods, storage and time of application.
Tableland soil of North-Eastern Brazil:characterization, genesis and classification
(State University of Ghent, 1986) Barrera, Daniel
The coastal low level tablelands of the State of Alagoas are located in the north-eastern region of Brazil between 8° 25' and 10° 20' south latitude, and from 35° 10’ to 37° 15' west longitude of Greenwich. These surfaces formed by Tertiary Sediments are flat or slightly undulated with slopes rarely higher than 4%. It enjoys a tropical climate with a dry summer and a constant temperature throughout the year. The dominant vegetation is formed by the so-called "Atlantic Forest", presenting also minor areas of "Cerrado". Nine profiles corresponding to the soil types present in, a) the well drained surfaces of the tablelands - which classify as Oxisols, Ultisols and Oxisol-Ultisol intergrades -, and b) in poorly drained depressions - classified as Spodo-sols -, were selected for this work. The influence of the morphogenesis of the landscape and the topographical location on soil development is evident from the soils studied. The properties of the soils are strongly related to geomorphic processes. The soils were characterized in terms of their morphological, physico-chamical, mineralogical and micromorphological properties. The sedimentological analysis of the sand fraction(63 - 2000ym) was also carried out. The mineralogy of the sand fraction is similar in all profiles. The light minerals are dominant ( 91-98% ) and almost entirely composed of quartz grains and no more than traces of feldspars. In the heavy fraction the opaques are dominant, ( 84-92% ); among the transparent minerals zircon dominates, followed by tourmaline and rutile. The composition of the clay fraction is also very similar throughout the region, dominated by kaolinite and minoramounts of gibbsite and oxi-hydroxides of iron and aluminium. With the sole exception of profile 2, all the soils are developed from highly uniform parent materials. At the sametime the parent materials of the different soils are also mutually very similar from sedimentological point of view. " Selective erosion 11 of fine soil components as a consequence of run-off is throughout the plateaux the dominant morphogenetic process, which influences the physico-chemical properties, the classification and the distribution of the soils in the landscape. The micromorphological analysis indicates similar features among the dominant soils of the area; and that the illuviation of clay is present in all profiles, which however is not manifested as clay skins in the field as a result of poor structure development. The soils were classified according to Soil Taxonomy, FAO/UNESCO, the Brazilian System of Soil Classification and under the I.N.E.A.C. ( Zaire ) System.
The role of microaggregation in physical edaphology
(Sokoine University of Agriculture, 1993) Mtakwa, Peter W
Soil type and the previous tensile strength and penetration resistance as a (PR) should allow the soil compared ranging fail to failure planes in between the microaggregates. function of easily along Five Tanzanian soil hardsetting Paleustalf from a extreme of strength behaviour, through a Paleudoll, Paleustult, both It was expected (the strength characteristics). that microaggregation types were can I characterized soil strength by measuring affect soil strength. matric potential cultivation history of one at Paleudalf and a to a strongly microaggregated Orthox expected to be at At each site soils that had a history of the weak end of the scale. 7 or more years of cultivation and cropping were compared with newly cultivated soils. The and Orthox Paleustult had the best PR characteristic for ease of root growth and the Paleustalf had the worst characteristic which suggested that it would not permit root growth at matric suctions exceeding 100 kPa. The Orthox also had much the most favourable tensile strength characteristic. At air dryness (100 MPa suction), the previously uncultivated and previously cultivated Orthox topsoils strength. compressive) Paleustalf topsoils. Paleustult) a previous had 3 and respectively, 9 times than less the tensile (and corresponding For three of the soils (Orthox, Paleudoll and history of cultivation was found to have significantly and substantially reduced the tensile strength of the topsoil at any given matric suction compared to the newly cultivated soil
Soil fertility evaluation of the rice growing areas and response of rice to nitrogen and phosphorus in West district,Zanzibar.
(Sokoine University of Agriculture, 2018) Hassan, Soud Nahoda
Studies were conducted at Bumbwi, Mtwango and Kizimbani villages of West District in Zanzibar to evaluate the fertility status of the soils, and their suitability for rice production and the response of rice (Oryza saliva L. var. NERJCAX2) to nitrogen (N), and phosphorus (P). Composite soil samples (0-30cm) were collected from Bumbwi. Mtwango and Kizimbani villages and analyzed to establish their fertility status. Field experiments were conducted at each site at (Bumbwi, Mtwango and Kizimbani) to assess the response of rice to N and P and NxP interaction to establish the optimal economic production of the Rice variety-NERICA No 12 and the residual effects of nitrogen and phosphorus on subsequent rice yields were assessed. The experimental design was a Randomized Complete Block Design (RCBD) with three replications at each site. Phosphorus was applied at the .ates of 0, 20, 40, 80 and 120 kg P ha’1 at planting time and nitrogen was applied at the rates of 0, 50, 100, 150 and 200 kg N ha’1, in two equal splits applied at two weeks after seedling emergence. Determination of the residual effects of N and P involved growing of rice during second and third seasons on treated plots without further application of N and P. Data were collected on the response of rice variety NERICA No. 12 to different rates ofN and P and their combinations. The nutrient status of the soils at the study areas were low in total nitrogen (0.01 to 0.1 %) and zinc (1.0 mg Zn/kg); medium in phosphorus (7 to 20 mg P/kg). The N and P fertilizer significantly (P<0.001) increased grain yield (5.73 t ha’1), with 200 kg N ha ’’ and 80 kg P ha’1. The residual effects of N and P, significantly (PO.OOl) increased rice yield during 2012/13, 2.70 to 5.56 t ha’1, 3.26 to 5.73 t ha’1 and 2.93 to 5.70 t ha'1, 2013/4 cropping seasons, 2.40 to 4.60 t ha’1, 2.46 to 4.90 t ha-1,and 2.50 to 5.90 t ha'1 and 2014/5 cropping seasons and 1.90 to 3,50 t ha’1, 2.26 to 3.53 t ha’1 and 2.23 to 3.5 t ha’1 at Mtwango, Bumbwi and Kizimbani respectively.
Soil fertility status and response of rice to nitrogen, phosphorus and farmyard manure under rainwater harvesting systems in semi arid areas of Maswa, Tanzania.
(Sokoine University of Agriculture, 2006) Kajiru, Geophrey Jasper
In semi arid areas of Tanzania, rainfed lowland rice production is constrained by inadequate plant nutrients and soil moisture thus restricting plant growth culminating into very low yields. With the adoption of appropriate rainwater harvesting (RWH) technologies the soil moisture stress is significantly alleviated. A study was conducted on the Ndala River Catchment comprised of Isulilo, Njiapanda and Bukangilija villages in Maswa district Tanzania.The objectives were to evaluate the fertility status of the soils and their suitability for rice production and the response of rice (Oryza saliva L. var. Supa India) to farmyard manure (F), phosphorus (P), nitrogen (N) and F-P-N applications over three cropping seasons (2002/03 to 2004/05) at Bukangilija village. The fertility status of the soils and their suitability for rice production were evaluated based on the local and technical indicators of soil fertility and land quality. Nitrogen was applied at the rate of 0, 50 and 100 kg N ha'1 as urea, phosphorus at 0, 30 and 60 kg P ha'1 as TSP and farmyard manure (kraal manure) at 0, 3.5 and 7 t ha'1. The P and F rates were accordingly broadcasted and incorporated into the surface soils one week before rice sowing and N was applied at two equal splits, at tillering and panicle initiation stages. Sowing was done between December and early January based on the long term seasonal rainfall distributions. Based on local and technical indicators of soil fertility, the soils on the catchment were of low fertility status and moderately suitable for rice production under RWH. The major limitations included low total nitrogen and organic matter contents, available zinc, soil moisture retention and high exchangeable Ca: Mg and Ca: Mg: K ratios and high ESP. The F, P and N and F-P-N combinations significantly increasedIll tillering, dry matter and grain yields and N, P and K contents in the rice plants and the main effect increases were in the order N>F>P. The ranges in the number of tillers per hill, dry matter yields, grain yields, N, P and K contents in the rice plants between the control and the highest F-P-N combinations were 10.6, 3522 kg ha’1, 1342 kg ha'1, 25.92 g kg’1, 1.38 g kg‘'and 12.12 g kg'1 , respectively. The rice response to F, N and F and the FPN combinations were due to increased availability and uptake of plant nutrients particularly N, P and Zn. The long term seasonal rainfall amounts and distribution and El-Nino-Southem Oscillation (ENSO) indices gave good and reliable projections on the time of sowing rice seeds in the study area. Based on the generated data farmyard manure, P and N rates at 3.5 t ha’1 30 kg P ha’1 and 50 kg N ha’1, respectively could be adopted for increased and sustainable rice production where R.WH technologies have been adopted on the Ndala River Catchment. Agro-climate extension service should be established.

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