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Long-term Effect of Alley Cropping System on Soil Productivity and Soil Quality: Evaluation of its Sustainability on Soil Resource
Dissertation Abstract:
Field and laboratory studies were conducted to evaluate the sustainability of alley cropping systems (with and without mulching) and fanners' practice as well as to im prove the existing cropping systems for a more sustainable agricul ture. Runoff, soil erosion, and nutrient loss; some soil biological, physical, and chemical properties; concentration of nutrients in soil solution: and grain yield were determined during the 1995 wet cropping season after six years of cropping experiment. Together with data from the six-year cropping experiment, the results were used to evaluate soil productivity, soil quality, and sustainability potential of the three cropping treatments.
Alley cropping with mulching was the best among the cropping systems studied and considered the most promising alternative for sustainable upland crop production systems for sloping agricultural lands. It also reduced runoff, soil erosion, and nutrient loss. It prevented the rapid deterioration of soil quality and provided better nutrient cycling, promoted biodiversity, produced higher crop yield, and was less dependent on external inputs (inorganic fertilizer) than the traditional farmers' practice.
Soil loss under alley cropping with mulch was 9.6 ton/ha, which was much lower than loss due to farmers' practice (117.0 ton/ha) and alley cropping without mulching (42.2 ton/ha). Nutrient losses due to soil erosion and runoff were minimized. Alley cropping with mulch had the highest soil quality for crop or soil productivity and soil quality for crop productivity and environmental stability as compared with the farmers ' practice. Also, only one limiting factor was noted for crop productivity in this cropping system as compared to four limiting factors in the farmers' practice.
In alley cropping with mulch, 9t dry matter of green manure was produced during the corn cropping season. Since these were used as mulch or organic fertilizer, it provided 192 kg nitrogen (N/ha), 16 kg phosphorus (P/ha), and 168 kg potassium (Kiha). 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 farmers ' 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 farmers ' practice, alley cropping with mulch was less dependent on fertilizer inputs. Since plots planted using fanners' practice suffered severe soil degradation, its so il 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 plots planted by alley cropping appeared to have adequate N and yield was already high even without fertilizer application.
In the alley cropping schemes, the presence of woody perennials improved field biodiversity as compared to farmers' practice, which was practically a monocropping system.