Soil Carbon Stocks in Long Term Organic Crop Production System: Dynamics, Relationships and Prospects

ABSTRACT

Quantification of soil organic carbon (SOC) stocks as indices of soil health, crop productivity and environmental sustainability necessitates the conduct of this research. A three-year field experiment was established to evaluate the dynamics, relationships and prospects of soil carbon storage under organic crop production system. The experiment involved four studies in Randomized Complete Block Design with two factors replicated thrice. Factor A for the various studies included corn, leafy vegetables, root vegetables and fruit vegetables. Factor B comprised of liquid organic amendments such as fish amino acid (FAA), fermented plant juice (FPJ), vermi tea and formulated organic fertilizer (FOF) which were submitted to the laboratory for nutrient analysis. Recommended management practices for the production of various crops were followed. Crop yield data were recorded. Composite soil samples were processed and brought to the Soils Laboratory for analysis of soil pH, % organic matter, total nitrogen, available phosphorus and exchangeable potassium. After two croppings, there was a declining trend in SOC of plots grown with corn, leafy, root and fruit vegetables applied with organic amendments. Among the soil chemical properties, pH, available P and exchangeable K were found to be significantly correlated to corn yield. Best fitted regression equation to estimate corn yield is given as: Yield (corn) = 15.19 + (-1.45*pH) + (-0.06*P) + (-0.01*K), R2=0.5528. Soil organic carbon was found to be significantly correlated with soil pH, available P and exchangeable K. Application of FOF resulted to the highest SOC accumulation rate (∆C=2.07 t/ha/yr) and shortest year (PY=22.52 yrs) to achieve potential SOC pool for corn; leafy vegetables (∆C=3.29 t/ha/yr; PY=14.13 yrs) and fruit vegetables (∆C=2.65 t/ha/yr; PY=17.58 yrs). For root vegetable production, application of FAA showed the highest SOC accumulation rate (∆C=4.72 t/ha/yr) and shortest year to achieve potential SOC pool (PY=9.86 yrs).

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