The effects of nitrogen and irrigation on timothy (Phleum pratense) grown for production of seed: I. Vegetative growth

Abstract

1. Plants of S.48 timothy were established on a 1 ft square pattern for production of seed. Two series of plots, one irrigated and one not irrigated, were treated with three levels of applied nitrogen: 0 (NO), 87 (Nl) and 261 (N2) lb N per acre (0, 97·5 and 292·5 kg N/ha) per annum, for 3 years. In this, the first of two papers, only vegetative aspects of growth are considered. Since the irrigation treatment started only 2 weeks before most of the data were recorded, effects of irrigation on vegetative growth were generally small.2. The number of tillers per plant was increased by application of nitrogen; the lower increment was more effective than the additional nitrogen in the higher dose.3. The weight of tillers per plant was increased by nitrogen at both levels of application. The mean weight of each tiller was increased by nitrogen after the first year, predominantly in the N 2 treatment. In the second year, irrigation also increased the weight per tiller.4. The weight of roots per plant was significantly affected by application of nitrogen. In the first year, the weight was increased by nitrogen in irrigated plots; in the second year the roots were significantly heavier in the Nl treatment than in N0 and N2 treatments, where weights were similar; the same situation existed in irrigated plots in the third year, but in non-irrigated plots the weights of roots were similar in N1 and N2 treatments and were heavier than in the N0 treatment. Irrigation had positive effects on the weight of roots in the first and second years.