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Tillage and residue management effects on soil carbon and nitrogen under irrigated continuous corn

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Demand for corn (Zea mays L.) stover as forage or as a cellulosic biofuel has increased the importance of determining the effects of stover removal on biomass production and the soil resource. Our objectives were to evaluate grain yield, soil organic C (SOC), and total soil N (0 to 150 cm) in a 10-year, irrigated, continuous corn study under conventional disk tillage (CT) and no-till (NT) with variable corn stover removal rates (none, medium, high). Natural abundance C isotope compositions were used to determine C additions by corn (C4-C) to the soil profile and to evaluate the retention of residual C3-C. After ten years of management treatments, mean grain yields were 7.5% to 8.6% higher for NT when residue was removed compared with no stover removal, while grain yields were similar for CT in all stover removal treatments. Turnover of SOC occurred as C3-C stocks were replaced by C4-C in the 0- to 120-cm soil profile. Total SOC and N stocks changed mainly in surface soils (0 to 30 cm), with no detectable cumulative changes at 0 to 150 cm. Specifically, SOC declined after 10 yr under CT at 0 to 15 cm and was affected by residue management at 15 to 30 cm. Total soil N was greater when no stover was removed (P = 0.0073) at 0 to 15 cm and from residue management at 15 to 30 cm. Total soil N was greatest when no residue was removed (P=0.0073) compared to high stover removal at 0 to 15 cm. Long-term NT ameliorated medium stover removal effects by maintaining near-surface SOC levels. Results support the need to evaluate SOC cycling processes below near-surface soil layers.
M. R Schmer , V. L. Jin , B. J. Wienhold , G. E. Varvel , R. F. Follett
USDA Scientist Submission
Soil Science Society of America journal 2014 Nov.-Dec. no.6 v.78
Journal Articles, USDA Authors, Peer-Reviewed
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