Effects of chlormequat application on stem characteristics, yield and panicle conformation of winter oats

Abstract

SUMMARYThe responses to treatment with chlormequat of winter oats at various rates of applied N were investigated in field experiments over two seasons. Chlormequat, applied at crop growth stage (GS) 32, significantly reduced stem length by an overall average of 25·3% in 1985/86 and 27·4% in 1986/87. The percentage reduction was not significantly influenced by variety or by the rate of N applied. All intcrnodes apart from the basal one were significantly shortened. The third internode from the base showed the largest percentage reduction and the uppermost internode the largest actual reduction in length, in all three varieties. Stem shortening was always associated with an increase in the weight per unit length of stem. In 1985/86 lodging in untreated control plots became more severe as N rate increased, but was completely controlled by the application of chlormequat at all but the highest rate (150 kg N/ha).Combine-harvested grain yields of the variety Pennal in 1985/86 and of Bulwark and Pcnnal in 1986/87 were reduced where chlormequat had been applied. Hand-harvested samples from these treatments did not show the same reductions in yield, but revealed a significant increase in the number of grains per panicle and a significant reduction in their mean individual weight. The grain characteristics of Peniarth were unaffected.The lengths of the main-stem panicles and primary branches in the panicle were shortened as a result of chlormequat application. In addition, the degree of branching and the number of spikelets were increased in the lower third of the panicle but reduced in the upper two thirds. In both Bulwark and Pennal the numbers of sterile grains were increased by the application of chlormequat and, in Bulwark only, the number of fertile grains was reduced. In Peniarth the numbers of fertile and sterile grains were unaffected.