[Effects of nitrogen application rate on light interception and dry matter distribution at diffe-rent layers in wheat...

With the large-spike wheat cultivar Shannong 23 as test material,a field experiment was conducted by increasing the relative soil moisture content to 70% and 65% at jointing and anthesis stages. Four nitrogen levels,0 (N₀), 180 (N₁), 240 (N₂) and 300 kg·hm^-2(N₃), were designed to examine the effects of nitrogen application rates on the interception of photosynthetic active radiation (PAR) and dry matter distribution of wheat at different canopy layers. The results showed that the total stem number of wheat population at anthesis stage, the leaf area index at 10, 20 and 30 days after anthesis, PAR capture ratio at upper and middle layers and total PAR capture ratio in wheat canopy on day 20 after anthesis of treatment N₂ were significantly higher than those in the treatments of both N₀ and N₁. Those indexes showed no significant increase when the application rate increased to 300 kg·hm^-2(N₃). The vegetative organ dry matter accumulation of all layers at maturity stage of treatment N₂ were significantly higher than N₀ and N₁. Compared with treatment N₀ and N₁, N₂ increased the grain and total dry matter accumulation by 36.7% and 35.4%, 9.5% and 10.2%, respectively, but had no significant difference with treatment N₃. The vegetative organ dry matter accumulation at all layers, grain and total dry matter accumulation were significantly and positively correlated with PAR capture ratio at upper and middle layers, and had no significant correlation with that at lower layer. The vegetative organ dry matter accumulation at all layers was significantly and positively correlated with grain dry matter accumulation. The application rate at 240 kg·hm^-2(N₂) would be the optimum treatment under the present experimental condition.