Most crops of grain sorghum are grown under conditions of limited irrigation or rainfall. Reduction of the degree and length of periods of moisture stress through the use of antitranspirants to control stomatal opening may increase the amount of time when photosynthesis takes place thus increasing crop yield with the water available. The purpose of this study was to determine the proper material, method, and timing of application for field use. Under limited irrigation conditions in the field, grain sorghum (Sorghum bicolor (L.) Moench) was sprayed at various rates and times with phenylmercuric acetate (PMA), atrazine, and Folicote. Mean grain yield increases of 5 to 17% were obtained, indicating considerable economic possibility. Rates of application required were aproximately 60 g/ha for PMA, 130 g/ha for atrazine, and 2 liters/ha for Folicote. However, more work is needed on rates and volume of spray. Application just prior to the boot stage was more effective than a later application.
Little has been done on the practical use of antitranspirants to increase the yield of field crops. The objective of this study was to determine the yield response of moisture‐stressed corn to the application of an antitranspirant. Folicote, a hydrocarbon film‐type antitranspirant, was foliarly applied on moisture‐stressed field corn (Zea mays L.) grown on Pullman silty clay loam (fine, mixed, thermic Torrertic Paleustoll) soil. Single seasonal applications (foliar spray with ground rig just prior to tasseling) resulted in average yield increases of 11 and 17 %. Fields where both the upper and lower leaf surfaces were sprayed required 1.93 L/ ha for maximum yield response, 42 % less than required where spraying was from the top only. The response was curvilinear with definite yield depression when rates were too great, indicating the need to determine optimum application rates according to the method of application. It was concluded that antitranspirant application is a feasible method of increasing corn yield under the conditions of this study.
Yields of potatoes and maize were considerably reduced as the irrigation interval exceeded one week. Partial closure of stomata as early as two days after irrigation indicated stress on plant growth even when most “available” soil moisture was still present. A linear relationship between degree of stomatal opening as measured by the oil‐drop penetration technique and the length of time after irrigation of various crops was established under field conditions.
A field experiment on corn with N, Zn, Mn, B and plant population as variables resulted in important positive interactions of plant population with applied Zn and with applied B indicating that limited Zn or B may be part of the reason for the severe yield decrease resulting from planting corn too thickly. High rates of applied Zn or B (90–180 kg/ha) were depressing to grain yield at low plant populations (40,000–53,333 plants/ha) but increased yields at high plant populations (80,000–93,333 plants/ha).
The logarithm of the nitrate‐N concentration of the midrib of the sixth corn leaf at the silking stage was found to be closely correlated with grain yield up to about 1,000 ppm. The relationship between the total N concentration of the leaf blades and grain yield was less distinct. The phosphate‐P concentration of the midrib and the total P concentration of the leaf blades were significantly increased by increasing applications of N. The B concentration of midribs at the point of maximum yield varied from < 60 ppm at low plant population to 120 ppm at high plant population.
In the semi‐arid Great Plains yields of grain sorghum [Sorghum bicolor (L.) Moench] are almost always limited by lack of rainfall or soil moisture during some part of the growing season. The purpose of this study was to determine if minimal land shaping practices in combination with antitranspirant application would increase yield levels of dryland grain sorghum.
Variables were width of watershed, width of growing bed, applied N, and foliarly applied antitranspirant combined in a central composite experimental design. Use of contoured, compacted bare micro‐watersheds increased grain sorghum yields of adjacent growing beds considerably even in two relatively wet years. However, yields of the entire area (growing bed plus watershed) decreased. Atrazine (2‐chloro‐ethylamino‐6‐isopropylamino‐s‐triazine) as an antitranspirant at 0.2 to 0.3 kg/ha effectively increased sorghum grain yields under conditions of solid planting and adequate nitrogen. The antitranspirant‐nitrogen interaction was especially positive under conditions of moisture stress.
Since most grain sorghum is grown under conditions where moisture stress is likely, further work on the use of antitranspirants is warranted in order to establish the conditions of response.
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