Author
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WINTERS, STEVEN - TAES |
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Unger, Paul |
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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/30/2000 Publication Date: 5/1/2001 Citation: N/A Interpretive Summary: Sorghum grain yields are 10-20% greater with conservation than with conventional tillage in ungrazed production systems. We conducted this study to validate tillage guidelines for grazed systems. The study was conducted on Pullman clay loam and involved grazing duration on winter wheat (Triticum aestivum L.) and tillage during fallow before dryland grain nsorghum [Sorghum bicolor (L.) Moench]. Soil compaction was greater and wheat residue amounts were less in grazed plots. Soil penetration resistances (0-5 cm depth) were 0.36, 0.52, 0.75, and 0.92 MPa; wheat residue amounts were 6.0, 4.8, 3.5, and 1.2 Mg/ha; and sorghum yields with no-tillage were 7.9, 7.5, 7.0, and 3.8 Mg/ha, for ungrazed, and early, normal, and late cattle removal dates, respectively, in 1996, which was a wet season. In 1997, a dry season, only the late removal treatment with no-tillage reduced yield (3.4 vs. 3.9 Mg/ha for the ungrazed no-tillage treatment). Use of one sweep or paratill operation early in fallow resulte in 1.9- and 1.4-Mg/ha sorghum yield increases, respectively, in 1996 for late cattle removal treatments, but had no effect on yield with the normal cattle removal treatment. In 1997, one sweep tillage operation increased yield 0.3 Mg/ha with late cattle removal. One sweep tillage operation reduced compaction, increased soil water content at planting an average of 26 mm over 2 years, and increased grain yield of sorghum that followed grazed wheat when wheat residue was 2.4 Mg/ha or less. If wheat residues amounts were 3.5 Mg/ha or more after grazing, no-tillage was as effective as any tillage treatment, and conservation tillage recommendations that were developed for ungrazed wheat would apply. Technical Abstract: Use of conservation tillage improved sorghum yields 10-20% in ungrazed production systems. Our objective in this study was to validate tillage guidelines for grazed systems. Grazing duration on winter wheat (Triticum aestivum L.) and tillage during fallow before dryland grain sorghum Sorghum bicolor (L.) Moench] were treatments on Pullman clay loam (Torrertic Paleustoll). Soil compaction was greater and wheat residue amounts were less in grazed plots. Soil penetration resistances (0-5 cm depth) were 0.36, 0.52, 0.75, and 0.92 MPa and wheat residue amounts were 6.0, 4.8, 3.5, and 1.2 Mg/ha for ungrazed, and early, normal, and late cattle removal dates, respectively, in 1996. Sorghum yields in 1996, an exceptionally wet season, with no-tillage were 7.9, 7.5, 7.0, and 3.8 Mg/ha, respectively. In 1997, a dry season, only the late removal no-tillage treatment reduced yield (3.4 Mg/ha compared with 3.9 Mg/ha for ungrazed no-tillage). Use of one sweep or paratill operation early in fallow resulted in 1.9- and 1.4-Mg/ha sorghum yield increases, respectively, in 1996 for the late cattle removal treatments, but had no effect on yield with the normal cattle removal treatment. In 1997, one sweep tillage operation increased yield 0.3 Mg/ha with late removal. One sweep tillage operation reduced compaction, increased soil water at planting an average of 26 mm over 2 yr, and increased grain yield of sorghum that followed grazed wheat when wheat residue amount was 2.4 Mg/ha or less. If wheat residue amount was 3.5 Mg/ha or more after grazing, no-tillage was as effective as any tillage treatment, and conservation tillage recommendations that were developed for ungrazed wheat would apply. |
