Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2000
Publication Date: 4/1/2001
Interpretive Summary: Winter wheat and grain sorghum are major dryland crops in the southern Great Plains, and yield well when grown continually or in a rotation. Improved water conservation practices are now available, suggesting they also could be rotated with other crops. Also, present federal farm policies allow farmers to produce other crops without losing government payments. Wheat, grain sorghum, and some other crop yields were determine in different cropping systems. Yields of opportunity crops, grown when enough soil water became available, were determined also. Effects of all systems on soil properties were determined. Wheat yielded 1620 lb/acre when rotated with grain sorghum or fall canola and 1080 lb/acre when grown continually or rotated with spring canola. Soil water content differences at planting resulted in the yield differences. Grain sorghum yielded 2580 and 2690 lb/acre when grown in rotation with wheat or continually. It yielded 2000 lb/acre when grown in rotation with kenaf. Kenaf yielded only 2050 lb/acre dry matter, but its protein content ranged from 19.5 to 32.7%. The canola crops failed. Triticale produced more forage than wheat (4100 vs. 3660 lb/acre), but less grain (970 vs. 1180 lb/acre). Opportunity crop yields were strongly influenced by soil water contents and precipitation. Soil organic carbon contents increased during the study. No definite trends in soil aggregate sizes, aggregate water stability, soil bulk density were found due to the systems. Some alternative and opportunity crops yield well, but generally no better than wheat or grain sorghum. Growing opportunity crops could increase overall production or result in some production when wheat or grain sorghum can not be grown.
Technical Abstract: Dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] yield favorably in the southern Great Plains when rotated or grown continually, but improved water conservation practices are available making other systems possible for these crops. Also, present federal farm policies allow farmers to produce other crops without losing government payments. Winter wheat, grain sorghum, and opportunity crop performance; alternative crop adaptability; and system effects on soil properties were determined in this study. Wheat yielded 1.82 Mg ha**-1 when rotated with grain sorghum or fall canola (Brassica napus L.) and 1.21 Mg ha**-1 when grown continually or rotated with spring canola. Water contents at planting resulted in the differences. Grain sorghum yielded 2.89 and 3.02 Mg ha**-1 when rotated with wheat or grown continually and 2.24 Mg ha**-1 when rotated with kenaf (Hibiscus cannabinus L.), although water contents were similar. Kenaf produced only 2.3 Mg ha**-1 dry matter, but contained 327 g kg**-1 protein at 32 d after planting and 195 g kg**-1 when killed by frost. Fall and spring canola crops failed. Triticale (x Triticosecale Wittmack) produced more forage than wheat (4.6 vs. 4.1 Mg ha**-1), but less grain (1.09 vs. 1.32 Mg ha**-1). Soil water contents at planting and precipitation strongly influenced opportunity crop yields. Mean soil organic carbon contents increased during the study (5.52 vs. 5.94 g kg**-1). Aggregate mean weight diameters and percentages <0.25 mm in diam. showed no definite trends. Few bulk density and no aggregate water stability results differed. Some alternative and opportunity crops produced favorably, but generally no better than wheat or grain sorghum.