Effects of Light,Nitrogen and Their Interaction on Grain Yield and Matter Production Characteristics of Japonica Super Rice

Field experiment was conducted using japonica super rice Nanjing 44 and Ningjing 3 with two nitrogen fertilization levels(N10:150 kg ha–1,N20:300 kg ha–1) and three shading treatments(L1:no shading,L2:shading 20 days before heading,L3:shading 20 days after heading) to study the effects of light,nitrogen and their interaction on grain yield and matter production.Results showed that,compared with L1 treatment,L2 not only reduced the effective panicles and grains per panicle,resulting in the decline of total spikelets by 24.81% to 35.63%,but also significantly reduced the tiller number and leaf area index at heading by 2.90%–6.44% and 19.02%–27.17% respectively,causing photosynthetic potential,dry matter accumulation decreased significantly from heading to maturity,and at last the final yield decreased by 27.23%–35.26%.Compared with L1 treatment,L3 mainly affected photosynthate accumulation from heading to maturity,leading to seed setting rate and grain weight significantly decreased by 1.49%–4.48% and 5.54%–9.17%,respectively,and the final yield decreased by 10.91%–18.47%.Under L2 condition,with increasing nitrogen level,tiller number and leaf area index at heading increased significantly,resulting in photosynthetic potential,dry matter accumulation increased significantly from heading to maturity,and the ultimately effective panicles,number of grains per panicle,total number of spikelets and the yield improved significantly.Under L3 condition,with increasing nitrogen level,photosynthate accumulation from heading to maturity increased significantly,dry matter translocation from stems and leaves to the panicle increased significantly,meanwhile,translocation rate and contribution rate were further improved,and the ultimate yield improved significantly.This indicated that nitrogen fertilizer could partially offset the impact of low light stress on the matter production and yield of japonica super rice.