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Reduced chemical input cropping systems in the southeastern United States. II. Effects of moderate rates of N fertilizer and herbicides, tillage, and delayed cover crop plow-down on crop yields

Published online by Cambridge University Press:  30 October 2009

Larry D. King
Larry D. King
Affiliation:
Professor, Department of Soil Science, North Carolina State University, Raleigh, NC 27695-7619.
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Abstract

In a previous study of reduced chemical cropping systems (N from legumes; chisel plow and disk tillage; cultivation for weed control) in the southeastern U.S., corn and wheat yields were less than half those obtained with recommended practices. The following practices were studied as possible ways to improve yields in the reduced chemical systems: 1) conventional tillage (chisel plowing and disking), inorganic Nat 70 or 140 kg/ha, and either cultivation or herbicides; 2) early versus late plow-down of clover green manures; 3) supplemental inorganic N fertilizer on corn and wheat in rotations relying on clover green manures for N; and 4) nicosulfuron herbicide banded on corn.

Yield of soybean in the rotations was not affected by any of these practices. With herbicides and fertilizer N at 140 kg/ha, continuous corn yields with no-till and conventional tillage were equal in 1990 and 1992, but no-till yield was 30% higher in 1991. When cultivation was used for weed control in the conventional tillage treatment, corn yield was similar to that of no-till with herbicide in the one year when rain was plentiful (yield 6000 kg/ha). However, in 2 of 4 dry years, yields (<2600 kg/ha) were higher with no-till. Clover biomass consistently increased by between 700 and 3500 kg/ha when plow-down was delayed from mid-April to early or mid-May (13 to 26 days). However, biomass N content increased significantly (by between 35 and 90 kg/ha) in only 2 of 5 years. Corn yields were affected in only 2 of 12 possible comparisons. In these cases, delayed clover plow-down reduced yield by about 50%. Supplementing corn with 45 kg N/ha and banding nicosulfuron increased yields, but only to between 62 and 84% of yields with recommended practices. Supplementing wheat with 45 kg N/ha increased yields by half, but only to between 40 and 60% of the yields with 90 kg N/ha.

Keywords

reduced chemical systemsbanded herbicidegreen manurecornwheatsoybeancloverno-tillconventional tillageN fertilizer
Type
Research Article
Information
American Journal of Alternative Agriculture , Volume 9 , Issue 4 , December 1994 , pp. 162 - 170
Copyright
Copyright © Cambridge University Press 1994

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