Browsing by Author "Poesen, J."
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Item Effect of conservational tillage on soil loss and plant nutrient status on vegetable yield, Northern slopes of Uluguru Mountains, Morogoro, Tanzania(2010) Msita, H. B.; Mtakwa, P. W.; Kilasara, M.; Kimaro, D. N.; Msanya, B. M.; Ndyetabula, D. K.; Deckers, J. A.; Poesen, J.The study was conducted to evaluate effects of conservational tillage on vegetable production on the northeastern part of Uluguru Mountains in Tanzania. Six treatments such as control conservational tillage; conservational tillage with manure; conservational tillage with insitu composting; control traditional tillage; traditional terrace with manure and traditional tillage with in situ composting were examined. Nutrient levels were determined from soil before and after harvest and from plant samples after harvest. Soil losses were assessed by collecting runoff using polyethylene troughs for each treatment. Analysis of variance and Multiple range test (P=0.05) was done to test the effect of the treatments. The differences (P=0.05) on soil loss, plant nutrient status and vegetable yield were observed. All conservational treatments gave high fresh yield (4.3–44.7 ton/ha), high nutrient retention (N% 0.11–0.14, P% 5.17– 16.33, K% 0.33-0.36) and experienced low soil losses (0.49, 0.54 to 0.65 ton/ha/season). While the opposite was true for traditional treatments lower fresh yield (0.9–13.9 ton/ha), low nutrient retention (N% 0.10–0.11, P% 0.91–4.00 and K% 0.29–0.32) and high soil losses (0.54, 0.83 to 1.26 ton/ha/season) at P=0.05. It was concluded from this study that the conservational tillage for vegetable production on sloping land ranging from 20 to 80 percent was the best practice resulting in increased crop yield, nutrient uptake, plant nutrient retention, and reduced soil loss.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, S. B.; Msanya, B. M.; Mtakwa, P. W.; Kimaro, D. N.; Deckers, J.; Poesen, J.; 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 mulching e. g. 184 vs. 20 in Majulai and 124 vs. 8 Mg ha-1 year-1 in Migambo village in 2012. The Pfactors 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-1yr-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 Magnitude of soil erosion on the northern slope of the Uluguru Mountains, Tanzania: Interrill and rill erosion(Elsevier, 2008) Kimaro, D. N.; Poesen, J.; Msanya, B. M.; Deckers, J. A.The magnitude of interrill and rill erosion was determined on the northern slopes of the Uluguru Mountains, Tanzania which is representative for larger areas of East African Arch Mountains, where population pressure is high and land degradation is severe. The aim of the study was to develop a database to support soil conservation in the area. The study was done on two distinct geomorphic units with respect to altitude and hence rainfall distribution pattern: mountain ridges with an altitude ranging from 1000 to 1500 masl and mean annual rainfall of 2300 mm and mountain foothills whose altitude and mean annual rainfall are 550 to 900 masl and 900 mm, respectively. Total soil loss was measured on 36 individual bounded plots measuring 1.2 m × 20 m using Gerlarch troughs on each day with rain from July 2000 to June 2001. The plots were located on six different geopedologic units, nine on mountain ridges and the rest on the mountain foothills. The slope gradient on the terrain ranged from 30% to 70%. The plots were put under maize cultivation as the main crop. Soil loss through rill erosion was estimated by volumetric measurements of rills on each soil erosion plot. The soil loss due to interrill erosion was obtained by subtracting soil loss through rill erosion from the total soil loss measured in the Gerlarch troughs. The results indicate that soil loss due to both interrill and rill erosion was very high with mean soil loss of 69 and 163 t/ha/year, respectively. Rill erosion accounted for about 58% of the total soil loss while interrill erosion contributed to the remaining 42%. Both interrill and rill erosion were higher in the mountain ridges with mean soil loss of 88 t/ha/year and 210 t/ha/year compared to 49 and 116 t/ha/year in the mountain foothills, respectively. Rill erosion was significantly higher (P ≤ 0.001) in all geopedologic units with slope gradient above 40% (mean soil loss ranged between 91 and 258 t/ha/year) compared to interrill erosion with mean soil loss varying from 41 to 115 t/ha/year. In geopedologic units with slope gradient above 60% both interrill and rill erosion were highly active while in geopedologic units with slope gradient below 40% the two processes were less active. The results demonstrate that rill erosion is more important than interrill erosion in the study area particularly where the slope gradient exceeds 40%. The results further show that the major part of the studied area has moderate interrill erosion (10–50 t/ha/year) and severe to very severe (N 100 t/ha/year) rill erosion. This study clarifies the magnitude of interrill and rill erosion which is important for designing soil conservation on agricultural fields.Item Major factors influencing the occurrence of landslides in the northern slopes of the Uluguru mountains, Tanzania(2000) Kilasara, M.; Mtakwa, P. W.; Poesen, J.; Deckers, J. N.Landslide mitigation largely depends on the understanding of the nature of the factors that have direct bearing on the occurrence oflandslides. Identification of these factors is of paramount importance in setting out appropriate and strategic landslides control measures. The present study focused on the identification of the major factors influencing the occurrence oflandslides in the Northern slopes of the Uluguru Mountains, Tanzania. The main objective was to establish relationship between spatial distribution of landslides and their causative factors. Such information would enable the planning of appropriate and strategic control measures. Aerial photographs, field survey and Geographic Information System (GIS) techniques were employed to identify the landslides features which occurred during EL NINO rains, spatial distribution and their corresponding factors. The results show that landslides dominate the geomorphic units with slope gradient ranging from 25% to over 80%. The most affected geomorphic units are in the order: debris slopes> incisions and V-shaped valleys > amphitheatres. Factors which cause theoccurrence of landslides are both soil and terrain related. The most important soil characteristics are presence of shallow soil solum with low bulk density and high macro porosity overlying a relatively less porous saprolite or hard bed rock. The terrain related factors include: undercutting of slopes by roads and pathways and presence of very steep concave side slopes. Water flow from roads and pathways and seepage from irrigation channels are precursors for the triggering oflandslides in the study area.Item Short and medium term assessment of tillage erosion in the Uluguru Mountains, Tanzania(Elsevier, 2004-05-26) Kimaro, D. N.; Deckers, J. A.; Poesen, J.; Kilasara, M.; Msanya, B. M.Soil translocation due to shallow tillage by manual hoeing appears to be one of the most important erosion processes in the Uluguru Mountains. In order to quantify erosion rates caused by manual hoeing in the area a tillage experiment was set up and an on-farm survey was conducted during the dry season of the years 2000 and 2001, respectively. Soil flux rates on eight slope gradients (31–67%) were monitored by measuring the tillage step characteristics using Trapezoid-step method and by collecting soil material lost in Gerlarch troughs. Soil flux rates due to medium-term (30 years) manual hoeing along contour bands with grass barrier were also monitored by measuring volumes of tillage step below and colluvium accumulation above the surface of the original slope on six slope gradients (51, 52, 55, 56, 58 and 60%). Average tillage depth for superficial tillage was 5.2 cm. The results obtained by the Trapezoid-step method ranged from 43 to 70 kg m À1 per tillage pass with a mean tillage transport coefficient (k) of 107.5 kg m À1 on the tested slopes. Mean soil flux rates obtained by Gerlarch trough method were slightly lower than those obtained by Trapezoid-step method with values ranging from 14 to 77 kg m À1 per tillage pass and a tillage transport coefficient (k) of 83.9 kg m À1 per tillage pass. The rates measured by both methods showed an increasing soil flux with slope gradient. Results on soil flux rates due to the medium-term tillage operation (step measurements) showed a negative trend with increasing slope gradient. Soil flux ranged from 148 to 42 kg m À1 per year for slopes between 51 and 60%. Soil flux due to colluviation behind grass barriers showed a similar trend with values higher than those obtained by step measurements. The soil flux rates behind grass barriers ranged from 153 kg m À1 per year on slope of 51% to 67 kg m À1 per year on a 60% slope in approximately 30 years of cultivation. A reasonable correspondence between calculated displaced soil (area under original slope) and the accumulated colluvium (area above the original slope) was obtained indicating significant contribution of tillage erosion. Contribution due to water erosion processes ranged from 7 kg m À1 per year on slopes of 51% to 25 kg m À1 per year on a slope of 60%. The study demonstrated that tillage translocation rates due to manual superficial tillage are very high and could partly be held responsible for the development of shallow soils observed on steep slopes and the accumulation of colluvium behind grass barriers along contour bands in the Uluguru Mountains.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.