Effects of nitrogen, phosphorus and sulphur nutrition on yield and grain composition of wheat

Abstract

In the 1978-79 season, Kopara was autumn sown on a moisture-retentive soil to assess responses of grain yield and grain composition to N, P, and S nutrition in a non-irrigated experiment using a four factor central composite second order design in incomplete blocks with five levels, each, of P applied at sowing (0, 100, 200, 300, 400 kg/ha), N at tillering (early; 0, 50, 100, 150, 200 kg/ha) and at the spikelet growth stage (late; 0, 50, 100, 150, 200 kg/ha), and S (0, 25, 50, 75, 100 kg/ha). The growing season was wetter and warmer than normal, and the crop did not suffer from water-stress except slightly at the early stage of grain growth. Mean grain weight, the main component of grain yield, was decreased significantly by N treatments. Early N increased both number and fertility of spikelets per spike, but decreased grain set and number of grains per spike. Late N did not affect spikelet production but improved grain set. The highest rate (200 kg/ha) of early and late N decreased grain yield by 19% and 11% respectively in absence of any significant increase in the spike population.

P and S did not have any significant effect on any yield component and on grain yield, except that P tended to improve grain weight at the early stages of grain-filling. While N treatments depressed harvest index (H.I.) significantly, early N-S interaction tended to increase grain yield and H.I. Correlation between grain yield and H.I., and grain yield and biological yield was r = 0.60** and r = 0.83** respectively. Grain N concentration increased linearly with N treatments, with later application being more efficient in increasing grain N concentration and N yield per m². While other factors tended to decrease it, P application improved N harvest index substantially.

P application tended to increase grain P concentration, enhance P translocation from non-grain parts and increase P harvest index noticeably. N treatments decreased concentration and accumulation of grain P as well as grain P yield per m² S application did not appreciably increase either grain S concentration or grain S yield, but increased S accumulation in the vegetative organs and decreased S harvest index (SHI). N treatments increased grain S concentration, but decreased S accumulation per grain. Late N application promoted S accumulation in the non-grain parts and hence decreased SHI. An early N-S interaction was associated with a decrease of SHI, but a late N-S interaction with an increase.

The results are discussed in relation to the effect of each of the four factors and the interactions on grain yield and its components and on grain nutrient content.