Original Article. Studies on trinexapac-ethyl dose reduction by combined application with adjuvants in spring barley

Abstract Trinexapac-ethyl is a popular plant growth regulator used in various crops, mostly due to its unique anti-lodging properties. Recently it has been found that this substance is also active in stress protection, which may increase its importance in the coming years. This paper presents a new approach to its application. Trinexapac-ethyl belongs to the cyclohexanedione class of herbicide chemistry, thus it is structurally similar to common graminicides frequently used with adjuvants. This study examines the effects of the application of trinexapac-ethyl with adjuvants. Field trials were conducted in the Institute of Plant Protection in Poznań (Poland), in 2014 and 2015. Trinexapac-ethyl was applied at recommended (0.4l・ha-1) and reduced doses (0.2l・ha-1) with organosilicone surfactant, ammonium sulphate and citric acid on spring barley. Stem shortening, yield components and grain quality were examined. The results of the study confirmed the possibility of dose reduction of trinexapac-ethyl by way of combined application with citric acid that reduced the pH of spray liquid or with ammonium sulphate without affecting its effectiveness. The greatest stem height reduction was observed after the application of a full dose of trinaxapac ethyl and its reduced dose in the mixture with citric acid or ammonium sulphate. Depending on the year of study, the effectiveness of the substances on stem reduction ranged from 5.6 to 16.5%. The tested mixtures did not have any significant impact on the number of grains per ear or the yield of spring barley. Trinexapac-ethyl and its mixtures with adjuvants did not influence the crude protein and starch in spring barley grains.