Date of this Version
Thesis (M.S.)—University of Nebraska—Lincoln, 1972. Department of Agronomy.
During the past two decades sorghum [Sorghum biocolor (L.) Moench] has become a major crop in the central Great Plains. Today three states, Texas, Kansas, and Nebraska account for 80% of the total United States sorghum production. Estimates from the sorghum producing areas, however, indicate that sorghum yield losses due to weeds of 20 to 40% exceeds those in any other grain crop.
Recently, interest has developed in chemicals that protect crops from herbicide injury. These protectants are applied to the seed, transplants, soil, or with herbicides and protect the crop from herbicide injury. This concept has a twofold appeal: (a) the use of plant protectants can result in less crop injury and (b) many hard-to-kill weeds can be controlled selectively because higher rates of herbicide can be used without crop injury.
The objective of this research was to study crop protectants and herbicides which give good control of weedy grass in order to develop selective, broad-spectrum weed control methods for sorghum. Studies were conducted in the greenhouse and field at Lincoln, Nebraska, during 1970, 1971, and 1972.
Greenhouse and field studies were used to evaluate herbicides which would improve grass weed control in sorghum [Sorghum biocolor (L.) Moench] and also to evaluate protectants which would reduce herbicide injury to sorghum. Of the many herbicides tested 2-chlorc-2’,6’-diethyl-N-(methoxymethyl) acetanilide (alachlor) was the only herbicide causing sorghum injury which could be moderated with crop protectants. The crop protectant, 1,8-naphthalic anhydride was most effective in reducing alachlor injury when applied as a seed treatment at ½% by sorghum seed weight. Storage of anhydride treated seed for 1 year did not effect sorghum seedling growth and development or the effectiveness of anhydride in reducing alachlor injury. Sorghum hybrids were found to differ in their response to anhydride and to alachlor injury.
Preemergence applications of alachlor at 3.4 kg/ha in the field did not cause a significant sorghum yield loss. Preplant applications of alachlor, incorporated into the soil, caused 4X more injury to sorghum than the same rate applied preemergence. Combinations of 2-chlorc-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) and alachlor did not increase sorghum injury or alter the effects of the crop protectants. Sorghum growth and development was stimulated by the crop protectants N,N-diallyl-2,2-dichlorcacetamide (R-25788) and R28725 (chemistry not released) when applied without a herbicide. In the field, anhydride was the most effective crop protectant used. R-28725 at ½% by sorghum seed weight at 0.6 kg/ha tank mix was effective in reducing sorghum injury at the lower alachlor rates. R-25788was the least effective of the crop protectants studied; however, seed treatment at ½% by sorghum seed weight was more effective than the tank mix.
Advisor: O. C. Burnside