Long-term effect of alley cropping system on soil productivity and soil quality: evaluation of its sustainability on soil resources

Alley cropping with mulching was the best among the cropping systems studied and is considered to be the most promising alternative for sustainable upland crop production system for sloping agricultural lands. Alley cropping with mulching was found to reduce runoff, soil erosion and nutrient loss. Soil loss under alley cropping with mulch was 9.6 ton/ha, which is much lower than the farmer's practice (117.0 ton/ha) and alley cropping without mulching (42.2 ton/ha). It minimized nutrient losses due to soil erosion and runoff. Alley cropping with mulch had the highest total score of soil quality for crop productivity or soil productivity (71) and soil quality for crop productivity and environmental stability (76), as against 57 and 58, respectively, in the farmer's practice. In addition, only one limiting factor was noted for crop productivity in this cropping system as compared to four limiting factors in the farmer's practice. In alley cropping with mulch, 9 tons dry matter of green manure was produced during corn cropping season. Since these were used as mulch or organic fertilizer, it provided 192 kg N, 16 kg P, and 168 kg K/ha. This recycled biomass provided favorable nutrient balance. Also, it helped maintain higher soil organic matter level, earthworm population and microbial activity. The grain yield of corn was highest (5,922 kg/ha) in alley cropping with mulch. It was lower in farmer's practice (4,628 kg/ha) and lowest in alley cropping without mulch (4,527 kg/ha). Considering the previous six cropping years, the trend of corn yield was increasing in the alley cropping with mulch but not in the other cropping systems. Unlike the farmer's practice, alley cropping with mulch was less dependent on fertilizer inputs. Since farmer's practice plots suffered severe soil degradation, the soil was highly deficient in nitrogen. As a result, yield response to 60 kg N/ha as urea fertilizer was very high. On the other hand, the soil in the alley cropping appeared to have adequate level of N and yield was already high even without the application of fertilizer. In the alley cropping schemes, the presence of woody perennials improved field biodiversity as compared to farmer's practice which is practically a monocropping system