Soil Science Collection
Permanent URI for this collectionhttp://10.10.97.169:4000/handle/123456789/43
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Browsing Soil Science Collection by Author "Deckers, J."
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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.