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Nine years of conservation agriculture-based cropping systems research in eastern Africa to soil degradation and mitigate effects of climate change

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In Ethiopia, repeated plowing, complete removal of crop residues at harvest and aftermath grazing of crop fi elds have reduced the biomass return to the soil and aggravated cropland degradation. Conservation Agriculture (CA)-based cropping systems may reduce runoff and soil erosion, and improve soil quality and crop productivity. Thus, a long-term tillage experiment has been carried out (2005 to 20123) on a Vertisol to quantify - among others - changes in runoff and soil loss for two local tillage practices, modifi ed to integrate CA principles in semi-arid northern Ethiopia. The experimental layout was a randomized complete block design with three replications on permanent plots of 5 m by 19 m. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, ploughed only once at planting by refreshing the furrow from 2005 to 2013 and 30% standing crop residue retention, (ii) terwah+ (TER+) with furrows made at 1.5 m interval, plowed once at planting, 30% standing crop residue retention and fresh broad beds, and (iii) conventional tillage (CT) with a minimum of three plain tillage operations and complete removal of crop residues. Wheat, teff, barley and grass pea were grown in rotation. Runoff and soil loss were measured daily. Signifi cantly different (p<0.05) runoff coeffi cients averaged over 9 years were 14, 22 and 30% for DER+, TER+ and CT, respectively. Mean soil losses were 3 t ha-1 y-1 in DER+, 11 in TER+ and 178 in CT. A period of at least three years of cropping was required before improvements in crop yield became signifi cant. Further, modeling of the sediment budgets shows that total soil loss due to sheet and rill erosion in cropland, when CA would be practiced at large scale in a 180 ha catchment, would reduce to 581 t y-1, instead of 1109 t y-1 under the current farmer practice. Using NASA/GISS Model II precipitation projections of IPCC scenario A1FI, CA is estimated to reduce soil loss and runoff and mitigate the effect of increased rainfall due to climate change. For smallholder farmers in semi-arid agro-ecosystems, CA-based systems constitute a fi eld rainwater and soil conservation improvement strategy that enhances crop and economic productivity and reduces siltation of reservoirs, especially under changing climate. Adoption of CA-based systems in the study area requires further work to improve smallholder farmersU+2019 awareness on benefi ts, to guarantee high standards during implementation and to design appropriate weed management strategies.
Boek: Green carbon : making sustainable agriculture real, Abstracts
Aantal pagina's: 1
Jaar van publicatie:2014