Submitted to: International Soil Conservation Organization Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 20, 1999
Publication Date: N/A
Technical Abstract: Grain sorghum [Sorghum bicolor (L.) Moench] is grown extensively in the US southern Great Plains, both with and without irrigation. Research involving dryland (rainfed) sorghum at the USDA-Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, Texas, USA, which provided 502 treatment-years of data from 37 studies, indicated grain yields more than tripled during the 1939 to 1997 period. A major yield increase occurred in the early 1970s when crop reside retention on the soil surface through use of no-tillage became common in the studies. From 1939 through 1970, mean annual grain yields exceeded 2000 kg ha**-1 only six time, but exceeded 2000 kg ha**-1 in 20 out of 27 years after 1970. Our objective was to determine the factors responsible for the increased yields. Factors evaluated were annual precipitation, growing season rainfall, soil water use, total water use, and year of record. Analyses performed for the 1956 through 1997 period included one uniformly managed study for which the overall yield increase was 139%. Results for the study showed use of improved hybrids accounted for about 46% of the increase and the remaining 93% was attributable to other factors, including increased soil water content at planting after 1970. This corresponded with the time when conservation tillage (no-tillage) studies involving use of improved herbicides became common at the Laboratory. Retaining crop residues on the surface through use of no-tillage increased soil water contents at planting in many studies and was primarily responsible for the yield increases.