Organic amendment effects on potato productivity and quality are related to soil microbial activity
Applying manure to row-crop systems can reduce inorganic fertilizer dependence and enhance soil biology and crop yields. However, it remains unclear whether low manure application rates or semi-annual application rates can provide these benefits. Our objective was to evaluate the effects of variable rates and timing of manure application on soil microbial processes and crop performance in a potato-corn cropping system.
We tested the effects of five manure application rates of 0.0 (Ctrl), 1.54 (T1), 3.08 (T2), 6.16 (T3), and 12.32 (T4) Mg C ha−1 on potato productivity, severity of common scab, and soil biological processes.
The highest rates of manure application consistently increased crop yields but even the lowest rate (1.54 Mg C ha−1) increased potato and corn yields. The severity of common scab incidence on daughter tubers was reduced by treatments T2, T3, and T4 in year one but was unaffected by any treatment in year two. Yield increases and reduced common scab severity were related to increased activities of C- and N-acquiring enzymes and microbial biomass C and N.
Manure application rates of <2 Mg C ha−1 can provide crop and soil benefits that appear to increase with multiple applications, while higher application rates provide stronger and more consistent effects on yields, and especially soil biological properties related to nutrient cycling and organic matter dynamics.
KeywordsManure Soil organic matter Potato Enzymes Microbial biomass Potato common scab
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