|Baumhardt, Roland - Louis|
Submitted to: International Soil Conservation Organization Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/10/2001
Publication Date: 5/30/2001
Interpretive Summary: Grain sorghum is a major crop in the US southern Great Plains. Data were obtained for 37 studies totaling 502 treatment-years of research on dryland grain sorghum from 1939 to 1997 at the USDA-Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, Texas. The results showed that grain yields more than tripled during that period. Much hof the yield increase occurred starting in the early 1970s when no-tillage became commonly used in some studies. The use of no-tillage resulted in more crop residues being kept on the soil surface. From 1939-1970 (32 years), average grain yield was above 2000 kg/ha (about 1800 pounds/acre) only six times, but was above that amount 20 out of 27 times after 1970. Our objectives were to document the yield increases that occurred through the years and to identify factors that were responsible for the increases. We considered total annual precipitation (rain and snow), growing season rainfall, soil water content at planting, soil water use, total water use, and year of record. Grain yield for a uniformly-managed study (1958-1997) increased of 139%. We found that changing to improved hybrids resulted in a yield increase of 46%. The other 93% of the increase resulted from other factors, including greater soil water contents at planting after 1970. This was the time when no-tillage became a common treatment in some studies at the Laboratory. Keeping more crop residues on the soil surface by using no-tillage increased soil water contents at planting in many studies because it resulted in less soil water loss due to evaporation and possibly greater water infiltration (less runoff). Greater soil water content at sorghum planting time was found to be the main factor that resulted in the yield increases with time at the Laboratory.
Technical Abstract: Grain sorghum [Sorghum bicolor (L.) Moench] is grown extensively in the US southern Great Plains. Data from 37 studies totaling 502 treatment-years on dryland grain sorghum research at the USDA-Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, Texas, USA, indicated grain yields more than tripled from 1939-1997. Much of this sincrease occurred in the early 1970s when crop residue retention on the soil surface through use of no-tillage became common in the studies. From 1939-1970, mean annual yield exceeded 2000 kg ha**-1 in only 6 years, but exceeded that amount 20 out of 27 years after 1970. Our objectives were to document the yield increases and identify factors responsible for the increases. Factors evaluated were annual precipitation, growing season rainfall, soil water content at planting, soil water use, total water use, and year of record. Results for a uniformly-managed study (1958-1997) with han overall increase of 139% showed that use of improved hybrids increased yields about 46%; the other 93% were attributed to other factors, including increased soil water content at planting after 1970. This corresponded with the time when conservation tillage (no-tillage) studies 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.