Shallow Incorporation of Manure in Reduced Tillage Systems.

Identifying effective manure management options that are compatible with reduced-tillage corn (Zea mays L.) systems is important for reducing nutrient runoff and nitrogen (N)-volatilization. Nine 2-yr field-scale corn trials (two corn grain, 8 corn silage) were initiated in 2008 in seven New York State counties to test the hypothesis that shallow incorporation of spring applied manure will provide the same N conserving benefits as more aggressive tillage options. Each trial consisted of two manure incorporation treatments (chisel versus aerator incorporation) and a control treatment (no incorporation within 5 d after application), conducted in four replications. Fields were 2^nd, 3^rd or 4^th year corn stands. Soil samples (0-20 cm) for fertility assessment and moisture content assessment were taken before manure application, at planting, when the corn was 15-30 cm tall, and at harvest. Additional measurements consisted of the presidedress nitrate test (PSNT), surface residue measurements (before manure application and after manure incorporation), and soil compaction (before manure application, when the corn was 15-30 cm tall, and at harvest). Yield was measured and forage analyzed for the eight corn silage sites. All plots were sampled for the late season corn stalk nitrate test (CSNT). The 2008 results showed no yield, PSNT, or CSNT differences between the aerator and chisel treatments indicating similar levels of N conservation. Aerator incorporation did result in greater surface residue cover with no significant differences in soil compaction or moisture content. The control treatment resulted in significantly lower yields at sites where the sum of soil N supply and N release from the organic fraction of the manure was insufficient to meet crop N needs. Shallow incorporation of spring applied manure appears to be an effective option for conserving nitrogen and maintaining greater coverage by surface residue. Additional site years are needed to further test this management option.