Impact of direct sowing mulch-based cropping systems on soil carbon, soil erosion and maize yield
Résumé
We studied the impact of direct seeding mulch-based cropping systems (DMC) on soil characteristics and maize production compared with conventional tillage management (CT) in the semi-arid region of western Mexico. Mulch treatments included 0, 1.5, 3 and 4.5 Mg ha-1 of added surface crop residues. The study was carried out from 1994 to 1998 on a Dystric Cambisol soil in La Tinaja in the state of Jalisco. Water runoff, soil erosion, soil C changes, maize aboveground biomass and grain yield were monitored on field plots. The results show that mulch treatments reduced annual water runoff losses by 10 to 50% relative to the conventional tillage treatment depending on residue amounts, slope and year. Soil erosion losses were reduced by 50 to 90%. Over a 5-year period soil carbon levels under mulch increased by 23 to 29% compared with conventional tillage, mainly due to increased crop residue inputs and reduced soil carbon erosion under mulch treatment. In the year with the most intense rainfall (1997), the conventional treatment lost about 800 kg of C ha-1 i.e. 2 to 7 times greater than mulch treatments. Maize grain yields were greater by 170 to 190% under mulch. Yield increases under mulch occurred each year, notably due to improved water and nutrient use efficiency. Potential yield benefits under mulch in the longer term due to build-up of soil organic matter and reduction of soil erosion were not obvious in our experiment. Overall, even small amounts of surface residue are effective at sustaining rainfed maize productivity under the semi-arid conditions of western Mexico. The short-term yield benefits are a promising factor for adoption of direct seeding mulch-based systems in the region.
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