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Economic trade-offs of biomass use in crop-livestock systems : exploring more sustainable options in semi-arid Zimbabwe

Posted by gabrielamartinez on , in Journal Articles

56873Authors: Homann-Kee Tui, S.; Valbuena, D.; Masikati, P.; Descheemaeker, K.; Nyamangara, J.; Claessens, L.; Erenstein, O.; Rooyen, A.; Nkomboni, D.

Published in: Agricultural Systems , 134: 48–60, 2015.


 

In complex mixed crop-livestock systems with limited resources and biomass scarcity, crop residues play an important but increasingly contested role. This paper focuses on farming systems in the semi-arid areas of Zimbabwe, where biomass production is limited and farmers integrate crop and livestock activities.
Conservation Agriculture (CA) is promoted to intensify crop production, emphasizing the retention of surface mulch with crop residues (CR). This paper quantifies the associated potential economic tradeoffs and profitability of using residues for soil amendment or as livestock feed, and explores alternative biomass production options. We draw on household surveys, stakeholder feedback, crop, livestock and economic modeling tools. We use the Trade-Off Analysis Model for Multi Dimensional Impact Assessment (TOA-MD) to compare different CR use scenarios at community level and for different farm types: particularly the current base system (cattle grazing of maize residues) and sustainable intensification alternatives based on a CA option (mulching using maize residues ± inorganic fertilizer) and a maize–mucuna (Mucuna pruriens) rotation. Our results indicate that a maize–mucuna rotation can reduce trade-offs between CR uses for feed and mulch, providing locally available organic soil enhancement, supplementary feed and a potential source of income. Conservation Agriculture without fertilizer application and at non-subsidized fertilizer prices is not financially viable; whereas with subsidized fertilizer it can benefit half the farm population. The poverty effects of all considered alternative biomass options are however limited; they do not raise income sufficiently to lift farmers out of poverty. Further research is needed to establish the competitiveness of alternative biomass enhancing technologies and the socio-economic processes that can facilitate sustainable intensification of mixed crop-livestock systems, particularly in semi-arid environments.

Options for increasing the productivity of the rice–wheat system of north-west India while reducing groundwater depletion : Part 1. Rice variety duration, sowing date and inclusion of mungbean

Posted by gabrielamartinez on , in Journal Articles

56831

Authors: Singh, B. ; Humphreys, E.; Yadav, S.; Gaydon, D.S.

Published in: Field Crops Research, 173: 68–80, 2015.


 

The irrigated rice–wheat (RW) systems of north-west India are critical for food security. However, these systems are not sustainable due to over-exploitation of the groundwater resource on which they largelyrely. Current farmer practice (FP) involves manual transplanting of rice into heavily tilled/puddled soil from 10 June to early July, prolonged periods of flooding, rice residue burning, and heavy tillage prior to sowing wheat. Inclusion of a short duration mungbean crop between wheat harvest and rice transplanting has also been promoted at times. Options for reducing irrigation input to the RW system include delaying transplanting until after the monsoon rains start (late June), switching to shorter duration rice varieties, and alternate wetting drying (AWD) water management for rice. However, the effect of such practices on groundwater depletion is not well-understood. Examining the effects of these options on cropping system yield and components of the water balance and water productivity is highly complex because of the need to consider the interactions between each crop in the system. Therefore, we used a cropping system model (APSIM) to compare the performance of RW systems with a range of rice transplanting dates (4 dates from 10 June to 10 August) and rice variety durations (long – 158 d, medium – 144 d, short – 125 d), with and without mungbean in the system. The results suggest that changing from long to short duration varieties would reduce ET by around 250 mm, more than enough to halt the groundwater decline, but with a reduction in rice-equivalent system yield of about 2.5 t ha−1 compared with current FP.
On the other hand, inclusion of mungbean into the RW system results in much higher system yield than recommended farmer practice (by over 3 t ha−1), but the tradeoffs are much higher ET (by 250–300 mm) and irrigation requirement (by 300–450 mm). The results of this study suggest that more effort should be directed towards the development of higher-yielding, short duration rice varieties to reduce groundwater depletion of the RW system while maintaining yield, and that inclusion of short duration summer crops such as mungbean should not be recommended.