The effect of a spray with 4,6-dinitro-o-cresol (DNOC) on nitrogen nutrition and yield of winter rye (Secale Cereale L.)

Abstract

Spraying a young cereal crop with the herbicide DNOC enhances yield apart from its weed-eliminating action. This study examined the extent to which this increase is due to the nitrogen-fertilizing effect of the spray. To this end the effects of a spray on growth, nitrogen uptake and yield of winter rye were examined at four nitrogen levels in two field experiments. Analogous in many respects to nitrogen fertilizing, the DNOC spray stimulated vegetative growth and the production of photosynthesizing area, retarded chlorophyll breakdown at ripening and increased yield by improving both the number of ears and number of grains per ear. It differed, however, in that growth stimulations was preceded by a temporary retardation and also in that the other positive effects were generally strongest not under conditions of nitrogen deficiency but when DNOC was applied together with nitrogen. The thousand-kernel weight was affected in opposite directions by the two treatments. The extra amounts of nitrogen taken up by the DNOC-treated plants could not account for the magnitude of the effects of the spray. It is argued that the DNOC spray, rather than replacing nitrogen, promotes a better use of it by inducing stronger growth of the root system and a prolongation of the vegetation period. This involves both a larger uptake of nitrogen from the soil and a better distribution of it in the plant.