An analysis of the effects of nitrogen deficiency on the growth and yield of a Western Australian wheat crop

Abstract

A wheat crop was grown on a nitrogen-deficient sandy soil. Urea was supplied at rates of 0 (N0), 56 (N1), and 336 (N2) kg nitrogen/ha. In general, the relative growth rate (R) decreased with time. During the first half of the growing season R for N2 > N1 >> N0, but in August deficient plants recovered rapidly. The recovery was associated with the emergence of the second tiller, an increase in net assimilation rate and nitrogen uptake, and a decrease in nitrogen stress. There was no evidence that the recovery was due to an increase in mineralization of soil nitrogen. Nitrogen stress in treatment N0 decreased from 48% in July to 14% in September. By contrast, stress in treatment N1 increased rapidly from 6 to 23% during July and fell to 5% by September. Flower initiation in N0 plants was delayed 14 days and ear emergence was delayed 8 days compared with N1 plants. The grain yields of N0 and N1 plants were 30 and 60% respectively of those of N2 plants. The decrease was due mainly to differences in the number of heads per sq metre, although nitrogen deficiency also reduced the number of grains per head and the weight per grain. The duration of photosynthetic activity after anthesis was not affected by nitrogen treatments. Harvest index was highest on N0 treatment and similar on N1 and N2 treatments.

Nitrate leaching stimulates subsurface root growth of wheat and increases rhizosphere alkalisation in a highly acidic soil

“…Similarly, the modelling work of Dunbabin et al (2003) shows that higher root densities as well as deeper rooting can increase nitrate capture in leaching conditions. This is further supported by field observations, which indicate that the capture of leached N reduced N stress in the latter part of the growing season in wheat (Halse et al 1969). The high N uptake efficiency by the roots in subsurface soil can be attributed to the improvement of 'synchronisation' between NO 3 − availability and NO 3 − interception by roots before it moved beyond the rooting zone (Angus 2001;Liao et al 2006).…”

Water and Nitrogen Effects on the Growth and Yield of Spring Wheat.

“…The shorter duration of tiller production in nitrogen stressed wheat was also reported by Roy and Gallagher (1985). Accelerated maturity of wheat was reported by Baker et al (1986) under severe drought, and by Halse et al (1969) under severe nitrogen deficiency. Non-stressed plants (WHNH) continued to form main tillers until T7 and produced numerous subtillers.…”

Salinity Affects the Timing of Phasic Development in Spring Wheat

“…McMaster et al (1992b) reported that the phyllochron estimates for the durations of various growth stages of well-watered wheat were about 20% greater than for wheat grown under dryland conditions. Time to maturity was also reduced by mild to moderate N deficit, although severe N deficiency tended to delay barley (Hordeum vulgare L.) development (Halse et al, 1969).…”