Browsing by Author "Mwango, Sibaway Bakari"
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Item Characterization of some typical soils of the miombo woodland ecosystem of Kitonga Forest Reserve, Iringa, Tanzania: physico-chemical properties and classification(Journal of Agricultural Science and Technology, 2014-03-20) Shelukindo, Hassan Bashiru; Msanya, B. M.; Semu, Ernest; Mwango, Sibaway Bakari; Singh, Bal Ram; Munishi, PantaleoDespite the fact that miombo woodland soils have significant implications in global climate change processes, few studies have been done to characterize and classify the soils of the miombo woodland ecosystem of Tanzania. The current study was carried out to map and classify soils of Kitonga Forest Reserve, which is a typical miombo woodland ecosystem, in order to generate relevant information for their use and management. A representative study area of 52 km 2 was selected and mapped at a scale of 1:50,000 on the basis of relief. Ten representative soil profiles were excavated and described using standard methods. Soil samples were taken from genetic soil horizons and analyzed in the laboratory for physico-chemical characteristics using standard methods. Using field and laboratory analytical data, the soils were classified according to the FAO-World Reference Base (FAO-WRB) for Soil Resources system as Cambisols, Leptosols and Fluvisols. In the USDA-NRCS Soil Taxonomy system the soils were classified as Inceptisols and Entisols. Topographical features played an important role in soil formation. The different soil types differed in physico-chemical properties, hence exhibit differences in their potentials, constraints and need specific management strategies. Texture varied from sandy to different loams; pH from 5.1 to 5.9; organic carbon from 0.9 g/kg to 20 g/kg; and CEC from 3 cmol/(+)kg to 24 cmol/(+)kg. Sustainable management of miombo woodlands ecosystem soils requires reduced deforestation and reduced land degradation.Item Effectiveness and performance of indigenous soil and water conservation measures in the west Usambara mountains, Tanzania(Sokoine University of Agriculture, 2015) Mwango, Sibaway BakariThe West Usambara Mountains in Tanzania are severely affected by soil degradation caused by water erosion that includes rill, interill, gully and landslides. To a large extent the area is also affected by soil degradation that is caused by declining soil fertility and harvesting of tuber, bulb and root crops. The problem of soil degradation in the area has triggered adverse effect on crop productivity and is a serious threat to livelihood. Many scientific „Soil and Water Conservation‟ (SWC) measures such as bench terraces, Fanya Juu terraces, cut off drains, contour strips and agroforestry have been promoted in the area to combat the escalating problem of soil degradation. However, these technologies were rejected or minimally adopted because most of them were laborious and expensive. In the West Usambara Mountains, farmers have their own local SWC measures such as miraba (rectangular grass bound strips that do not necessarily follow contour lines), micro ridges and stone bunds, technologies which unfortunately have received very little considerations. Miraba is the most preferred and widely practised indigenous SWC measure in the West Usambara Mountains because it is cheaper in implementation and provides fodder for livestock. Despite all the efforts in combating soil degradation, little success has been achieved as the process has been active even in places where SWC measures are practised. The general objective of the current study was to enhance knowledge on indigenous SWC measures under smallholder farming conditions for preventing soil degradation and improving crop yields in the West Usambara Mountains. Specifically the study aimed to i) evaluate potentials and constraints of indigenous SWC technologies for minimizing soil degradation and enhancing crop yields in various landscape types in farmers‟ fields ii) determine the effectiveness and performance of selectediii indigenous SWC measures for improved crop yields and iii) investigate the mass of soil and nutrient losses due to crop harvesting under different indigenous SWC measures. The study was conducted in Majulai and Migambo villages in Lushoto District, Tanzania. The studied villages belong to two major contrasting agro- ecological zones of the West Usambara Mountains. The former village belongs to dry warm and the latter to the humid cold agro-ecological zone. Participatory Rural Appraisal (PRA) coupled with soil fertility and crop yield surveys under various SWC technologies in farmers‟ fields were conducted. Low soil fertility and spatial variability of soil fertility were revealed as major constraints to high crop yields under miraba. Thus, miraba were integrated with mulching and spacing of grass strips adjusted to rectify the observed constraints such that i) the spacing of grass strips that form miraba across the slope was reduced from traditionally very wide (10 m - 30 m apart depending on the size of the farm plots) to 5 m apart to mimic the recommended maximum width of hand made bench terraces; and ii) mulching applications using leaves of readily available plants namely Tithonia (Tithonia diversifolia) and Tughutu (Vernonia myriantha). These plants are also reported to have appreciable contents of N, P and K. The effectiveness and performance of miraba that were adjusted to 5 m and with above-mentioned mulching materials were tested in runoff experiments that were set in Majulai and Migambo villages, in which climatic data were also collected using standard rain gauges and tipping bucket rain gauges. Furthermore, root properties of Guatemala grass (Tripsacum andersonii), Napier grass (Pennisetum purpureum) and Tithonia shrub (Tithonia diversifolia) were investigated in farmers‟ fields and theiriv erosion-reducing effects predicted. Since these plants are used for establishing miraba and stabilizing the edge of bench terraces, it was deemed rational to investigate the erosion-reducing potential of their roots since during drought or fire outbreak, the above biomass disappears but roots remain and these could significantly contribute to reduction of soil runoff. A survey was also conducted in farmers‟ fields to investigate the magnitude of soil and nutrient losses resulting from harvesting of root, tuber and bulb crops under miraba. The aim was to determine the magnitude and effect of this process on soil degradation and extent to which it may contribute to frustrate soil conservation efforts in the area. The results of the current study showed that: at 5 m spacing of miraba grass strips, there was formation of progressive bench terraces which significantly demonstrated their effectiveness in controlling soil erosion in the West Usambara Mountains. Formation of progressive bench terraces as a result of miraba implementation is by far cheaper than mechanical construction of bench terraces which is not favoured by farmers due to the labour costs that are involved. The roots of Guatemala grass had higher (p < 0.05) potential to reduce soil erosion rates by concentrated flow than Napier grass and Tithonia shrub in the 0-40 cm soil depth. These findings have implications on the selection and use of appropriate plants for soil erosion control. Soil loss was significantly (p < 0.05) higher in cropland with no SWC measure than under miraba with mulching (e.g. 184 Mg ha -1 yr -1 vs. 8 Mg ha -1 yr -1 ). The annual nutrient losses (kg ha -1 yr -1 ) were higher (p < 0.001) in croplands with no SWC measures (e.g. 307, 0.8, 14 NPK) than under miraba with mulching (37, 0.1, 4.0 NPK respectively). Soil fertility was higher (p < 0.05) under miraba with Tughutu than under miraba with Tithonia and miraba sole. Similarly, maize and bean yieldsv (Mg ha -1 ) followed the same trend e.g. 3.8 vs. 1.6 for maize and 1.0 vs. 0.6 for beans under miraba with Tughutu mulching vs. cropland with no SWC measures respectively. The crop yields did not vary between segments under miraba or miraba with mulching, whereas, under cropland with no SWC measures, maize yields differed significantly (p < 0.05) with lower position segments having higher yields than the upper position segments. Climatic conditions had an influence on the effectiveness and performance of miraba such that miraba were found more effective in Migambo village which is humid than in Majulai village which has drier climate. During dry spells, Napier grasses forming miraba were found to die out and rejuvenate during the rainy seasons, hence the formed Napier grass strips become weaker and less effective. On the other hand, soil loss due to crop harvesting (SLCH) under miraba was significantly (p < 0.05) higher for carrot 7.1 than 3.8 for onion and 0.7 Mg ha -1 harvest -1 in the case of potato harvesting. Soil nutrient losses in kg ha -1 harvest -1 were higher (p < 0.05) for carrot than for onion and potato harvesting. Soil water content at harvest time played a significant role at 5 % level in inducing SLCH for onion crop. Bulk density and soil texture played only a minor role to SLCH of the studied crops. These observations imply that soil degradation due to crop harvesting under miraba is substantial and poses a challenge that calls for immediate attention on the harvesting practices. Based on the findings, it is concluded that i) low soil fertility and spatial variability of soil fertility and crop performance under traditional miraba and micro ridges are the major constraints to high crop yields in smallholder farmlands of the West Usambara Mountains. ii) soils of the West Usambara Mountains are susceptible to erosion as indicated by their very low values of K factors and very high rates of soilvi degradation by water erosion. iii) roots of Guatemala grass are more effective in reducing concentrated flow erosion rates in the 0 - 40 cm soil depth than the roots of Napier grass while the roots of Tithonia shrub are the least effective. Thus selection of plants with effective rooting characteristics for controlling concentrated flow erosion is important. iv) improved miraba are effective in reducing runoff, soil and nutrient losses, but, improved miraba with either Tithonia or Tughutu mulching were more effective. v) Tughutu mulches had higher potential in soil fertility restoration than Tithonia mulches; and thus improved miraba with Tughutu mulching was the best SWC measure for improving crop yields. vi) although miraba and miraba with mulching were effective in reducing soil and nutrient losses, significant rates of soil and nutrient losses under miraba that were revealed due to harvesting of root, tuber and bulb crops could frustrate the success of soil conservation efforts that have been achieved. The following recommendations are made: i) due to the vulnerability of the West Usambara Mountains to soil degradation, it is recommended not to cultivate in these areas without the use of appropriate SWC measures. ii) in dry areas such as Majulai village drought resistant grasses such as Guatemala should be used for establishing miraba because Napier grasses mostly preferred are sensitive to drought, thus leading to reduced effectiveness of miraba. iii) the spacing of miraba grass strips across the slope is recommended at 5 m apart for effectively controlling spatial variability of soil fertility and crop yields and for allowing miraba to form progressive bench terraces that are effective in controlling soil erosion in the West Usambara Mountains. iv) the use of Tughutu shrub should be strongly promoted for use as mulching materials under miraba as the shrub has demonstrated itsvii effectiveness in controlling soil erosion and at the same time improving soil fertility and crop yields. v) furthermore, Tughutu shrubs should be planted along the borders of farm plots so that the plants can easily be available for use as mulching materials. vi) farmers should remove as much as possible soil stuck on the harvested crops at their farm plots to avoid losses of soil and nutrients from farm lands. vii) further studies should be carried out on the scaling up of the application of improved miraba in other areas not only in the West Usambara Mountains but also in other areas of the country with similar socio-economic and environmental conditions for reduced soil degradation and improved crop productivity. viii) the potentials of the studied mulching materials should be tested for the productivity of vegetables such as cabbage, tomatoes, onions and carrots which are widely cultivated in the West Usambara Mountains. ix) further research should be carried out to investigate the effectiveness of the studied soil conservation practices on watershed protection to mitigate river stream sedimentation. x) more studies should be carried out to investigate SLCH for other crops in different climatic conditions and soil types tovalidate further this process under low input farming.Item Effectiveness of mulching under miraba in controlling soil erosion, fertility restoration and crop yield in the Usambara mountains, Tanzania(Wiley Online Library, 2014-09-23) Mwango, Sibaway Bakari; Msanya, B. M.; Mtakwa, Peter W.; Kimaro, D. N.; Deckers, Jozef; Poesen, JeanSoil erosion is a major threat to food security in rural areas of Africa. Field experiments were conducted from 2011 to 2014 in Majulai and Migambo villages with contrasting climatic conditions in Usambara Mountains, Tanzania. The aim was to investigate the effectiveness of mulching in reducing soil erosion and restoring soil fertility for productivity of maize (Zea mays) and beans (Phaseolus vulgaris) under miraba, a unique indigenous soil conservation measure in the area. Soil loss was significantly higher (p < 0·05) under miraba sole than under miraba with mulching, for example, 35 versus 20 and 13 versus 8 Mg ha 1 y 1 for Majulai and Migambo villages, respectively, in 2012. Soil fertility status was significantly higher (p < 0·05) under miraba with Tughutu mulching than under miraba sole, for example, 0·35 versus 0·25% total N, 37 versus 22 mg kg 1 P and 0·6 versus 0·2 cmol(+) kg 1 K for the Majulai village; and 0·46 versus 0·38 total N, 17·2 versus 10·2 mg kg 1 P and 0·50 versus 0·2 cmol(+) kg 1 K for the Migambo village. Maize and bean yields (Mg ha 1 ) were significantly higher (p < 0·05) under miraba with Tughutu mulching than under miraba sole, 2·0 versus 1·3 for maize and 0·9 versus 0·8 for beans in Majulai; and 3·8 versus 2·6 for maize and 1·0 versus 0·8 for beans in the Migambo village in 2012. This implies that Tughutu mulching is more effective in improving crop yield than Tithonia, although both could potentially protect the arable land from degradation caused by water erosion under miraba. Copyright © 2014 John Wiley & Sons, Ltd.Item Effectiveness of selected soil conservation practices on soil erosion control and crop yields in the Usambara Mountains, Tanzania(SCIENCEDOMAIN international, 2014-12-16) Mwango, Sibaway Bakari; Msanya, B. M.; Kimaro, D. N.; Mtakwa, Peter W.; Deckers, Jozef; Poesen, Jean; Massawe, I.; Samwel, J.Indigenous soil conservation measures such as miraba have been widely used in Usambara Mountains for controlling soil erosion but with little success. On-farm runoff experiments were set from 2011–2014 on Acrisols in Majulai and Migambo villages with contrasting agro-ecological conditions in the Usambara Mountains, Tanzania. The aim was to investigate the effectiveness of miraba and miraba with various mulching materials in reducing runoff, soil and nutrient losses and improving productivity of maize (Zea mays) and beans (Phaseolus vulgaris). Results show that mean annual runoff coefficients (mm mm -1 ) ranged from 0.72 for cropland with no soil conservation measure (control) to 0.15 for cropland with miraba and Tithonia (Tithonia diversifolia) mulching in Majulai village and respectively from 0.68 to 0.13 in Migambo village. Soil loss was significantly (P = .05) higher under control than under miraba with either Tughutu (Vernonia myriantha) or Tithonia -1 -1 mulching e. g. 184 vs. 20 in Majulai and 124 vs. 8 Mg ha year in Migambo village in 2012. The P- factors were significantly (P = .05) higher under miraba sole than under miraba with mulching in Majulai village (0.18 vs. 0.11) and in Migambo village (0.10 vs. 0.05).The annual nutrient losses in kg ha -1 yr -1 were significantly (P = .05) higher under control than under miraba with mulching 367 vs. 37 total N, 0.8 vs. 0.1 P and 14 vs. 4 K for Majulai village; 474 vs. 26 total N, 0.7 vs. 0.1 P and 20 vs. 1.2 K for Migambo village in 2012. Maize and bean yields were significantly (P = .05) higher under miraba with Tughutu mulching than under control (e.g. 2.0 vs. 0.7 Mg ha -1 for maize in Majulai in 2012). Thus miraba with Tughutu mulching is more effective in improving crop yields than miraba with Tithonia and miraba sole.Item The influence of selected soil conservation practices on soil properties and crop yields in the Usambara Mountains, Tanzania(SCIENCEDOMAIN international, 2014-12-08) Mwango, Sibaway Bakari; Msanya, B. M.; Mtakwa, Peter W.; Kimaro, D. N.; Deckers, Jozef; Poesen, J.; Nzunda, I.; Ringo, S.The Usambara Mountains in Tanzania are severely affected by soil erosion which has led to deterioration of soil properties and reduced crop productivity. Indigenous soil erosion control measures such as miraba which are widely practised in the area have yielded little success. Field plot experiments were laid down in Majulai and Migambo villages from 2011 – 2014 on typical soils of the area (Acrisols). The aim was to single out soil properties developed under the studied soil conservation practices and their impact on crop productivity with reference to maize (Zea mays) and 2+ 2+ + beans (Phaseolus vulgaris). Results showed that total N, OC, available P, Ca , Mg , K and Ph were powerful (P = .05) attributes that discriminated conservation measures. Magnitudes of the discriminating attributes followed the trend: miraba with Tughutu (Vernonia myriantha) mulching >miraba with Tithonia (Tithonia diversifolia) mulching > miraba sole > cropl and with no ‘Soil and Water Conservation’ (SWC) measures (control). Contents ofmicro-nutrients did not differ significantly with SWC measures except for Zn which was significantly (P = .05) lowin the control. Bulk density and available moisture content (AMC) were also strong discriminators of conservation measures. Maize and bean grain yields differed significantly (P = .05)with the trend: miraba with Tughutu > miraba with Tithonia > miraba sole > control in both villages. Crop yields under miraba were a 2 2+ + 2 function of AMC and pH (R = 0.71); AMC, available P, Ca and K (R = 0.89) under miraba with 2+ + 2 Tithonia mulching; AMC, available P, Ca and K (R = 0.90) under miraba with Tughutu mulching. These findings imply that miraba with Tughutu mulching had greater potential in improving soil properties and crop yields than miraba with Tithonia mulching and miraba sole.Item Root properties of plants used for soil erosion control in the Usambara Mountains, Tanzania(SCIENCEDOMAIN international, 2014-08-25) Mwango, Sibaway Bakari; Msanya, B. M.; Mtakwa, Peter W.; Kimaro, D. N.; Deckers, Jozef; Poesen, Jean; Massawe, V.; Bethuel, I.Plant roots may have a strong erosion-reducing effect. However, little is known about root characteristics of tropical plants used for erosion control. A study was thus conducted in the Western Usambara Mountains, Tanzania to investigate rooting characteristics of Guatemala grass (Tripsacum andersonii), Napier grass (Pennisetum purpureum) and Tithonia shrub (Tithonia diversifolia), also referred to as wild sunflower, and to evaluate their potential for erosion control. For each plant species, mean root diameter (D), root density (RD), root length density (RLD) and root area ratio (RAR) were assessed for six plants in each species and relative soil detachment rate (RSD) predicted. Mean RD values in the 0 - 0.4 m soil depth for Majulai village and Migambo village respectively 3 3 were 50.9 and 58.6 kg/m for Guatemala grass, 30.4 and 31.3 kg/m for Napier grass and 3 3 22.1 and 23.0 kg/m for Tithonia shrub. RLD values were 35.9 and 45.0 km/m for 3 3 Guatemala grass, 31.3 and 150.0 km/m for Napier grass and 10.5 and 6.4 km/m for -12 -14 Tithonia shrub. Predicted RSD values were 4.43*10 and 1.20*10 for Guatemala -5 -4 -3 -4 grass, 6.10*10 and 2.74*10 for Napier grass and 4.43*10 and 2.24*10 for Tithonia shrub in the 0 - 0.4 m soil depth. The results indicate that Guatemala grass has a higher potential to reduce soil erosion rates by concentrated flow as compared to Napier grass or Tithonia shrub in the 0 - 0.4 m soil depth. These findings have implications on the selection and use of appropriate plants for soil erosion control.Item Soil fertility and crop yield variability under major soil and water conservation technologies in the Usambara Mountains, Tanzania(SCIENCEDOMAIN international, 2014-12-15) Mwango, Sibaway Bakari; Msanya, B. M.; Mtakwa, Peter W.; Deckers, J.; Poesen, J.; Meliyo, J. L.; Dondeyne, S.Indigenous soil and water conservation (SWC) technologies such as miraba (rectangular grass strip bounds that do not necessarily follow contours) and micro ridges have been used widely in the Usambara Mountains, Tanzania. However, their strengths and limitations to crop productivity have not been investigated. This study aimed to determine soil fertility and crop yield variability under miraba, micro ridges and bench terraces as a way to explore and compare these SWC technologies. A survey was carried out in Majulai watershed (with Acrisols as dominant soils) which is highly affected by soil degradation due to water erosion. Composite soil samples were collected from 0 - 30 cm depth in upper, middle and lower segments within bench terraces, micro ridges and miraba at the upper, mid and lower slopes of the watershed. Contents of most soil nutrients (e.g. + 2+ 2+ available P, K , Ca and Mg ) and maize grain yields varied significantly (P=.05) between SWC technologies, with the trend: bench terraces > micro ridges >miraba>control (fields with no SWC measures). Similarly under all SWC technologies soil fertility and maize grain yields varied significantly (P=.05) with slope position, showing the trend: lower slopes > mid slopes > upper slopes. Moreover, soil fertility and maize grain yields varied significantly (P=.05) between segments of the studied SWC technologies except for bench terraces. The trends for both soil fertility and maize grain yields were as follows: lower segments > middle segments > upper segments under micro ridges; lower segments > upper segments > middle segments under miraba. These observations call for management strategies and technological adjustments that would reduce pattern and magnitude of spatial variations of soil nutrients and crop yields under miraba and micro ridges for improved crop production in the Usambara Mountains.Item Soil loss due to crop harvesting in Usambara Mountains, Tanzania: the case of carrot, onion and potato(SCIENCEDOMAIN international, 2014-09-06) Mwango, Sibaway Bakari; Msanya, B. M.; Mtakwa, Peter W.; Kimaro, D. N.; Deckers, J.; Poesen, J.; Lilanga, S.; Sanga, R.Among the various soil erosion processes threatening sustainable agriculture, soil losses due to root, tuber and bulb harvesting are poorly documented, particularly in tropical environments. A study was thus conducted in two villages with contrasting agro-ecological conditions on Acrisols and Fluvisols in Western Usambara Mountains, Tanzania. The aim was to investigate the mass of soil and nutrients lost and the factors influencing variation of soil loss due to crop harvesting (SLCH) for Carrot (Daucus carrota), Onion (Allium cepa L.) and Potato (Solanum tuberosum L.) under low input agriculture. A total of 108 farm plots were sampled from the two villages. The mean SLCH values were significantly higher for carrot (7.1 Mg/ha/harvest) than for onion (3.8 Mg/ha/harvest) than for potatoes (0.7 Mg/ha/harvest). Soil nutrient losses in kg/ha/harvest were higher for carrot than for onion and potatoes (e.g. 30 N, 0.1 P, 1.5 K for carrot vs 6.3 N, 0.04 P, 0.2 K for onion) in Majulai village. SLCH was greater in Migambo (humid cold) than in Majulai (dry warm) for all the studied crops. Soil water content at harvest time played a significant (P = .05) role in inducing SLCH for onion while bulk density for carrot, whereas for potato they were not significantly influenced by soil water content and bulk density. Soil texture played only a minor role to SLCH of the studied crops. The observed soil and nutrient losses in the current study are substantial and pose a challenge that calls for immediate attention to the harvesting practices in the study area. However, combating water erosion is far more urgent.