|Brock, B - USDA-NRCS|
Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2005
Publication Date: March 1, 2007
Citation: Franzluebbers, A.J., Brock, B.G. 2007. Surface-soil responses to silage cropping intensity on a typic kanhapludult in the Piedmont of North Carolina. International Journal of Soil and Tillage Research. 93:126-137. Interpretive Summary: Soil degradation is a concern on dairy farms relying on high-quality silage crops as a feedstock. No-tillage management of continuous silage crops on erodible land may not effectively control erosion and improve soil quality, because of the lack of crop residue return to protect the soil surface. A collaborative research effort between the Agricultural Research Service in Watkinsville Georgia and USDA – Natural Resource Conservation Service with a local producer in the Piedmont region of North Carolina was conducted from 2000 to 2004 to assess changes in soil quality. The farmer-initiated experimental approach allowed us to evaluate the effectiveness of different crop rotations with different frequencies of silage harvest on soil physical, chemical, and biological properties. Harvesting silage less often and leaving more crop residue on the soil surface was beneficial to most soil properties. A moderately intensive silage cropping system created a more optimum balance between agronomic production and environmental quality. This research will help farmers and agricultural extension specialists to design and implement improved cropping systems to achieve simultaneous goals of production and environmental quality on the 0.5 million acres of corn silage in the southeastern USA.
Technical Abstract: 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.