Exploring the variability among smallholder farms in the banana-based farming systems in Bukoba district, Northwest Tanzania

A study was conducted in the high and low rainfall zones in the banana-based farming system in Bukoba district, Tanzania, to explore the variability among household characteristics and farm productivity. Approaches used included a participatory rural appraisal, rapid system characterization, surveys and detailed farm monitoring in two villages, one from each zone in 2005 through 2006. Based on a wealth-ranking, four household resource groups with decreasing wealth were identified: Resource group 1 > Resource group 2 > Resource group 3 > Resource group 4, distinguished by domestic assets, livestock ownership and labour relations. Through principal component analysis using additional variables defined by research team, three Functional Resource Groups from among the four Resource groups at each rainfall zone were identified distinguished by: soil fertility management, food security and farm and off-farm income as important indicators of variability. Further detailed monitoring over 14 months (from March, 2006 through May, 2007) in at least three households from each functional resource group showed that N, P and K balances among land use types and farms were driven by levels of organic inputs used and were also related to wealth and dependence on off-farm activities. However, all households were net food buyers, implying food insecurity. In addition, off-farm activities and off-farm income were important livelihood survival strategie

Managing legume cover crops and their residues to enhance productivity of degraded soils in the humid tropics: a case study in Bukoba District, Tanzania

In degraded soils, establishment of soil-improving legumes can be problematic and requires investment of labour and other resources. We investigated various aspects of managing herbaceous legumes in farmers¿ fields in Bukoba District, Tanzania. Biomass and N accumulation by Crotalaria grahamiana was 1.1 Mg ha¿1 and 34 kg N ha¿1 when established without farmyard manure (FYM) and 3.0 Mg ha¿1 and 95 kg N ha¿1 when established with 2 Mg FYM ha¿1, and incorporation of the biomass gave an increment of 700 kg ha¿1 of grain in the subsequent maize crop. Maize grain yield at different application rates of Tephrosia candida residues ranged from 1.4 to 3.3 Mg ha¿1 and from 2.0 to 2.8 Mg ha¿1 in the high and low rainfall zone, respectively. Application of tephrosia biomass at a rate of 2 Mg ha¿1 had no significant effect on maize yield whereas rates of 4, 6 and 8 Mg ha¿1 gave comparable yields. Apparent N recovery efficiencies at all rates of tephrosia residues were maximally 27 and 13% for the high and low rainfall zones, respectively. Mulching with Mucuna pruriens suppressed weeds by 49 and 68% and increased maize yield by 57 and 103% compared with the weedy fallow in the respective zones. Incorporated residues had a weaker effect on suppressing weeds and poor labour productivity (2 l and 36 kg grain person-day¿1) compared with mulched residues (32 and 52 kg grain person-day¿1) in the high and low rainfall zone, respectively. These results indicate that if well managed, legume residues have the potential to increase yields of subsequent maize crops on degraded soils

Shoot water content and reference evapotranspiration for determination of crop evapotranspiration

Determination of water requirement for crops in resource limited areas is challenging, yet worsened by the common assumption that all crop varieties within a species have similar water requirements. The objective of the study was to indirectly determine crop evapotranspiration of soybean varieties, using reference evapotranspiration and shoot water content under tillage and no tillage cultivation. The treatments were no tillage and conventional tillage as main plots, and soybean varieties Nyala, SB19, and SB20 as sub-plots, replicated three times. Crop evapotranspiration (ETC) and crop coefficient (KC) were different among varieties, and increased during growth period. SB20 had the highest KC (0.8437 at 87 days after planting - DAP); followed by SB19 (0.7888 at 70 DAP), and Nyala (0.7026 at 66 DAP). Conversely,water use efficiency (WUE) was 0.58 in SB19, 0.52 in Nyala, and 0.47 in SB20.Validation of the calculated ETC using a crop production function showed a correlation of r = 0.97 between the observed and predicted yields of the three varieties. Furthermore, the normalised root mean square error (NRMSE) and the index of agreement (d) were 0.14 and 0.87, respectively indicating accurate fit. Calculated crop coefficient strongly correlated with observed shoot water content of Nyala (R2 = 1), SB19 (R2 = 1), and SB20 (R2 = 1).La d\ue9termination du besoin en eau de la plante dans des milieux \ue0 ressources limit\ue9es est un d\ue9fi, encore aggrav\ue9 par l\u2019hypoth\ue8se commune qui stipule que toutes les vari\ue9t\ue9s d\u2019une esp\ue8ce ont les m\ueames besoins en eau. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9terminer indirectement l\u2019\ue9vapotranspiration de la culture des vari\ue9t\ue9s de soja, en utilisant l\u2019\ue9vapotranspiration de r\ue9f\ue9rence et la teneur en eau de la pousse sous labour et sans labour. Les traitements \ue9taient sans labour et avec labour conventionnel comme parcelles principales, et les vari\ue9t\ue9s de soja Nyala, SB19, et SB20 comme sous parcelles, r\ue9pliqu\ue9es trois fois. L\u2019\ue9vapotranspiration des cultures (ETc) et le coefficient de culture (Kc) \ue9taient diff\ue9rents entre les vari\ue9t\ue9s, et augmentaient durant la p\ue9riode de croissance. SB20 avait la valeur la plus \ue9lev\ue9e de Kc (0,8437 \ue0 87 jours apr\ue8s plantation - DAP)\ua0; suivie de SB19 (0,7888 \ue0 70 DAP), et Nyala (0,7026 \ue0 66 DAP). Inversement, l\u2019efficience d\u2019utilisation de l\u2019eau (WUE) \ue9tait 0,58 dans SB19, 0,52 dans Nyala, et 0,47 dans SB20. La validation de l\u2019ETc calcul\ue9e en utilisant la fonction de production de la culture a montr\ue9 une corr\ue9lation r= 0.97 entre les rendements observ\ue9s et pr\ue9dits des trois vari\ue9t\ue9s. De plus, la racine des carr\ue9es moyens normalis\ue9s de l\u2019erreur (NRMSE) et l\u2019index d\u2019accord (d) \ue9taient 0,14 et 087, respectivement indiquant une concordance pr\ue9cise. La valeur calcul\ue9e du coefficient de culture \ue9tait fortement corr\ue9l\ue9e avec la valeur observ\ue9e de la teneur en eau de la pousse de Nyala (R2 = 1), SB19 (R2 = 1), et SB20 (R2= 1)

Adapting to change in banana-based farming systems of northwest Tanzania: the potential role of herbaceous legumes

Keywords: Land use changes; Herbaceous legumes; Adoptability; N 2 -fixation; Residual effect; Legume management; Exploration of options, Nutrient depleted soils.The banana-based farming system inBukoba District,Tanzania, has been in existence for over 300 years. At present, banana productivity in homegardens is declining largely due to the decline in soil fertility, which in many years was counteracted by the availability of manure. The grazing land is being converted to crop fields and other uses. Crop fields have in part, assumed the role of grazing land of providing for fodder to the few cattle kept today, which is not sustainable in many years. This thesisexplores opportunities for integrating herbaceous legumes in the farming system, to act as a engine to keep maintain the farming system by providing fodder to the cattle (hence manure for use in the home gardens) and improvement the fertility of soils of annual crop fields as improved fallows.The area of grasslands was shown to have decreased over 50 years by 40% whereas the area of annual crop fields increased by 225%. Encroach on grasslandreduced the ability of farmers to restore the fertility of their soils as possibilities to keep livestock, thus the supply of manure diminished.This had a consequence on nutrient balances where by the home gardens receiving manure, had positive balances of N, P and K whereas the home gardens receiving no manure had negative nutrient balances. Nutrient balances of annual crops were negative particularly with maize, indicating that they are vulnerability to impoverishment.Field experiments showed that the biomass, N accumulation and N 2 -fixation varied among the legume species. The performance of legumes was regulated more by the soil N and the soil pH. The non-forage legumes species Tephrosia candida , Crotalaria grahamiana and the forage species Mucuna pruriens and Macrotyloma axillare performed better among the tested legumes, and were selected by farmers on the basis of biomass yield, weed suppression and tolerance to pest and diseases. Laboratory experiments showed that the rate of N release from decomposing legume residues depended on the quality [(polyphenols + lignin)-to-N ratio, lignin-to-N ratio and lignin content] of residues, whereby residues with low (polyphenols + lignin)-to-N ratio, lignin-to-N ratio or lignin contents decomposed faster. Maize yield doubled or tripled when legume residues were applied though the yield response to legume residues was limited when compared with the application of the recommended rate of mineral N fertilisers (50 kg N ha -1 ). It was further observed that, in short term, application of large quantities of legume residue (above 2 Mg ha -1 ) does not add to significant higher maize production. In the degraded soils, the biomass yield and N accumulation of legume species increased by 100% when established with farmyard and had higher residual effect (80%) on the yield of the subsequent maize. Mulching with legume residues was the best option to apply legume residues as it suppressed weeds in the maize crop and had higher labour productivity. Field experiment with farmers showed that the growing legumes as improved fallows increase maize production and maintained positive N balance. However, growing legumes for fodder was in conflict with maize production and N balance of annual crop fields. The model experiments with a multiple goal liner programming (MGLP) model showed that legumes can act asaengine to keep maintain the farming system by providing fodder to the cattle, hence manure to the homegardens and improvement the fertility of soils of annual crop fields as improved fallows. Farmers have different preferences on legumes and choice of legumes to be introduced in the farming system should be based on farmer production objectives. The main policy implication of the findings is that promotion of legumes is best approached by taking the socio-economic systems into account. These include securing other farm inputs and marketing of farm produce by reliable and attractive markets