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Title: RESIDUAL EFFECTS OF FALL DEEP TILLAGE ON SOYBEAN YIELDS AND NET RETURNS ON TUNICA CLAY SOIL

Author
item Wesley, Richard
item Smith, Lowrey
item SPURLOCK, STAN - MISSISSIPPI STATE UNIV.

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/1999
Publication Date: 9/1/2000
Citation: Wesley, R.A., Smith, L.A., Spurlock, S.R. 2000. Residual effects of fall deep tillage on soybean yields and net returns on tunica clay soil. Agronomy Journal. 92(5):941-947.

Interpretive Summary: In the midsouthern USA, soybean are normally planted on the clayey soils in May and June in a seedbed prepared with a disk harrow in the fall or spring. During the 1970 through 1991 period, yields from this system of production averaged 1500 kg/ha in Mississippi and were only marginally profitable. The objectives of this research were to determine: 1) the residual effect of fall-applied deep tillage on yield and net returns from nonirrigated soybean planted in April on a Tunica clay, and 2) the frequency of deep tillage necessary to maximize and sustain higher yield and net returns. Over the 5-yr study, yield from soybean grown in production systems with annual fall deep tillage averaged 1016 kg/ha (42%) greater than the average yield from the conventional (disked) production system (2436 kg/ha), whereas production systems with fall deep tillage applied once every 2 yr or once every 3 yr averaged 823 kg/ha (34%) greater. Net returns from the conventional production system averaged $220/ha, whereas net returns from production systems with fall deep tillage applied annually, once every 2 yr, or once every 3 yr averaged from $396 to $436/ha, or from 80 to 98% greater than net returns from the conventional production system. Fall deep tillage should be applied at least once every 3 yr to maximize and sustain higher yield and net returns on nonirrigated Tunica clay.

Technical Abstract: A 5-yr study was conducted on a nonirrigated Tunica clay (clayey over loamy, montmorrillonitic, non-acid, thermic, Vertic Haplaquept) to determine: 1) the residual effects of fall deep tillage on soybean yield and net returns, and 2) the frequency of deep tillage necessary to maximize and sustain higher yield and net returns. The deep-till treatments included fall deep tillage applied: 1) annually; 2) once every 2 yr; 3) once every 3 yr; 4) once every 4 yr; 5) once every 5 yr; 6) with a Paratill plow, annually; 7) with an experimental machine to extensively modify the soil profile once every 5 yr; and 8) a conventionally-tilled treatment that was disked annually. Yields from soybean grown in production systems with fall deep tillage applied annually, once every 2 yr, once every 3 yr, or with a Paratill plow annually averaged 1016 (42%), 826 (34%), 819 (34%), and 808 ka/ha (33%) greater, respectively than the average yield from the conventional production system (2436 kg/ha). Net returns from the conventional production system averaged $220/ha over the 5-yr study, whereas net returns from soybean grown in production systems with fall deep tillage applied annually, once every 2 yr, or once every 3 yr averaged from $396 to $436/ha, or from 80 to 98% greater than net returns from the conventional production system. Fall deep tillage should be applied at least once every 3 yr to maximize and sustain higher yield and net returns from soybean grown on nonirrigated Tunica clay.