Surface soil responses to silage cropping intensity on a Typic Kanhapludult in the piedmont of North Carolina.

摘要

Although reduced tillage itself is beneficial to soil quality and farm economics, the amount of crop residues returned to the soil will likely alter the success of a particular conservation tillage system within a farm operation. We investigated the impact of three cropping systems (a gradient in silage cropping intensity) on selected soil physical, chemical, and biological properties in the Piedmont of North Carolina, USA. Cropping systems were: (1) maize (Zea mays L.) silage/barley (Hordeum vulgare L.) silage (high silage intensity), (2) maize silage/winter cover crop (medium silage intensity), and (3) maize silage/barley grain - summer cover crop/winter cover crop (low silage intensity). There was an inverse relationship between silage intensity and the quantity of surface residue C and N contents. With time, soil bulk density at a depth of 0-3 cm became lower and total and particulate C and N fractions, and stability of macroaggregates became higher with lower silage intensity as a result of greater crop residue returned to soil. Soil bulk density at 0-3 cm depth was initially 0.88 Mg m-3 and increased to 1.08 Mg m-3 at the end of 7 years under high silage intensity. Total organic C at 0-20 cm depth was initially 11.7 g kg-1 and increased to 14.3 g kg-1 at the end of 7 years under low silage intensity. Stability of macroaggregates at 0-3 cm depth at the end of 7 years was 99% under low silage intensity, 96% under medium silage intensity, and 89% under high silage intensity. Soil microbial biomass C at 0-3 cm depth at the end of 7 years was greater with low silage intensity (1910 mg kg-1) than with high silage intensity (1172 mg kg-1). Less intensive silage cropping (i.e., greater quantities of crop residue returned to soil) had a multitude of positive effects on soil properties, even in continuous no-tillage crop production systems. An optimum balance between short-term economic returns and longer-term investments in improved soil quality for more sustainable production can be achieved in no-tillage silage cropping systems..