Effects Of Nitrogen Application And Planting Density On Yield Formation And Quality Of Rice In Coastal Saline Alkali Land

With the reclamation of coastal saline alkali land and the expansion of rice planting area,suitable nitrogen application and planting density have become the key technical problems to be solved urgently in high yield cultivation of rice in saline alkali land.Therefore,the experiment of combination of different nitrogen application and density was designed and conducted at Shun Tai farm,Sheyang,Yancheng in 2016 and.2017.Rice cultivar Nanjing 9108 was chosen as material,treated with six nitrogen application rate and transplanting density levels.The nitrogen application rate was ON(0kg/667m2),14N(14kg/667m2),17N(17kg/667m2),20N(20kg/667m2),23N(23kg/667m2)and 26N(26kg/667m2)respectively,and transplanting density was D1(25 cm x 12 cm)and D2(30 cm×12 cm).The study aimed at exploring the effects of nitrogen application rate and planting density on the yield formation of rice in saline alkali soil,nitrogen absorption and utilization and rice quality,which could further provide the basis for high yield cultivation of rice in coastal saline soil.The main results are as follows:(1)With the increase in nitrogen rate,the spike number per 667m2 decreased,and spike number under D1 was higher than D2 treatment.With the increase of nitrogen application,the number of grains per panicle was significantly increased while the seed setting rate and 1000 grains weight significantly decreased.Thegrain yield increased firstly and then decreased with the increase of nitrogen,,especially at later stage.Grain yield under high density treatment was higher than that under the low density under low nitrogen rate(0N-20N).Grain yield under low density was higher than that under high density at high nitrogen rate(23N,26N),while grain yield under high density was higher than that under low density at lower and medium nitrogen rate(0N-20N).The highest grain yield was achieved under 20ND1 tratments,559.14 kg/667m2.(2)The tillers number under D1 was always higher than that under D2 treatment under different nitrogen rate treatments.,The tillers number increased gradually after transplanting to the jointing stage but increased first and then decreased at the heading stage and mature stage with the increase of nitrogen application rate.The leaf area index and leaf area decay rate increased with the increase in nitrogen application rate.The leaf area index at jointing and heading stage under D1 were larger than those under D2 treatment.With the increase in nitrogen rate,dry matter weight at jointing and heading increased synchorously.At the jointing stage,dry matter weight under DI was higher than that under D2 treatment,and such trends were also observed at jointing and maturity stages.(3)With the continuous increase of nitrogen application rate,the nitrogen content of plants increased,while the opposite trend was observed in the nitrogen accumulation.The nitrogen content of rice under D1 treatment was lower than that under D2 treatment.The nitrogen accumulation of rice plants at jointing and maturity stages under D1 treatment were lower than those under D2 treatment,while the opposite trend was observed at heading stage.With the increase in nitrogen application rate,the nitrogen accumulation rate before jointing stage and increased from jointing stage to heading stage,while nitrogen accumulation from heading heading to maturity stage increased firstly and then decreased,and the highest value was observed under 23N treatment.The nitrogen absorption rate under D1 before jointing was slightly lower than that under D2,while the opposite trend was observed at the other growth stages.With the increase in nitrogen application rate,the nitrogen utilization rate,the agronomic efficiency and 100 kg seed nitrogen demand increased firstly and then decreased,while physiological efficiency and partial factor productivity decreased.The nitrogen absorption and utilization rate under D1 treatment was slightly lower than that under D2,while the opposite trend was observed in partial productivity.(4)Nitrogen application has great influence on rice processing quality,and the.effect of planting density on processing quality was relatively less.With the increase in nitrogen,the integrity of the brown rice rate,milled rice rate,chalkiness rate,chalkiness,protein content and steamed rice increased,while rice amylose content and steamed rice aroma,luster,taste,taste,taste value was significantly decreased and poor taste value was close to 10.The chalkiness and cretaceous degree under D1 treatment were higher than that under D2 treatment.