The Effect of 4,6‐dinitro‐o‐cresol* (Dnoc) on Growth, Development and Yield of Winter Rye (Secale Cereale L.)

Summary. The spraying with DNOC as a herbicide in a young crop of winter rye results in an increased grain yield, even in weed‐free trials. In order to trace the sequence of reactions by which treatment in winter affects the yield next summer, growth, development and yield of treated and untreated plants were examined in a single weed‐free experiment which included the study of several seed rates. As a result of the DNOC treatment, vegetative growth was retarded at first, but later the treated plants recovered and surpassed the control plants in fresh and dry weight. Since their dry matter percentage was somewhat lower and their nitrogen content a little higher, the crop appeared both more vigorous and more youthful. Leaf blade area and chlorophyll content of leaves and culms were increased and chlorophyll breakdown at ripening was delayed. No effect could be observed on the rate of development of the young spike, but heading, flowering and ripening were retarded. Yield increase on the DNOC‐treated plots was 10% on an average. The analysis reveals that on these plots 3% more culms were formed, each of which bore 5% more kernels; the average kernel weight was unaffected. The increase in ear density can be ascribed to the more luxuriant vegetative growth, while the kernel weight per car is correlated with the nitrogen content of the culm. It is concluded that the yield increase is due to a stronger vegetative growth together with a prolonged period of generative development. Effets d'un traitement au DNOC sur la croissance, le développement el le rendement d'un seigle d'hiver