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Rheinischen Friedrich-Wilhelms-Universität zu Bonn (2010)

Improving the water productivity of integrated crop-livestock systems in the semi-arid tropics of Zimbabwe an ex-ante analysis using simulation modeling

Masikati Patricia

Titre : Improving the water productivity of integrated crop-livestock systems in the semi-arid tropics of Zimbabwe an ex-ante analysis using simulation modeling

Auteur : Masikati Patricia

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität zu Bonn

Grade : Doktor der Agrarwissenschaften (Dr. agr.) 2010

Description
The semi-arid tropics of Zimbabwe are characterised by low levels of economic activity, high incidence of land degradation and a high concentration of the rural poor. Water scarcity is also a principle constraint, and available water is used ineffectively, as evidenced by low crop and livestock water productivity. Low crop productivity is partly attributed to inherent low soil fertility and impoverishment is further exacerbated by continuous cropping without addition of adequate organic and inorganic fertilizers due to unavailability and high costs, while feed shortages especially during the dry season, high incidence of diseases and mortality rates mainly cause low livestock productivity. In this study soil fertility and feed issues were addressed as they were perceived as some of the constraints with solutions that are within the farmers’ capabilities. On-farm surveys and field experiments were done in Nkayi district in northwest Zimbabwe to understand the current situation in crop-livestock systems. A simulation modeling approach was used to evaluate potential interventions, which can be used as entry points to improve crop and livestock water productivity. Crop and livestock production were the main livelihood activities. Average cultivated land was 3 ha while fallow land was 1 ha per household. Livestock holdings that include cattle, donkeys and goats were 9.5 TLU. Soil fertility in terms of N, P and OC was very low, average values were 0.04, 0.01 and 0.37%, respectively. Crop and livestock water productivity was also very low, average values were 0.04 kg m-3 and 0.02 US$ m-3, respectively. Interventions which use low cost and locally available organic inputs were evaluated using APSIM and feed deficits using the MLA model. The interventions were the FP, MN and MMR treatments. Their potential effects on crop water productivity, soil fertility and contribution to dry season feed were assessed. Average maize grain water productivity was 0.34 0.42 and 0.76 kg m-3 under the FP, MN and MMR treatments, respectively, while mucuna water productivity was 1.34 kg m-3. Cropping under the FP and MN treatments showed negative trends in SOC and TN over years with losses ranging from 17 to 74 kg ha-1 yr-1 and 6 to 16 kg ha-1 yr-1, respectively. In contrast the MMR treatment showed positive trends in both SOC and TN under the poor and average farmers while for the better-off it was maintained. SOC and TN were increased by about 2.6 to 194 kg ha-1 yr-1 and 6 to 14 kg ha-1 yr-1, respectively. Crude protein (CP) content in maize stover was 29, 32 and 82 g kg-1 under the FP, MN and MMR treatments, respectively. The potential contribution to daily feed requirements during the dry season, in-terms of DM, CP and ME of stover and mucuna biomass was also evaluated. Maize stover obtained from the FP and MN treatment could not supply 100% of the daily required DM, CP and ME. Stover and mucuna biomass from the MMR treatment could supply 100% of daily required DM, CP and ME for the poor and average farmers while it could supply about 50% of DM and 100% of CP and ME required for the better-off farmers. The MMR treatment has the potential to improve soil fertility, crop and livestock water productivity in the semi-arid smallholder farming systems of Zimbabwe.

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Page publiée le 8 novembre 2011, mise à jour le 10 novembre 2021