Effects Of Nitrogen Application On Occurrence,Control Of Main Diseases And Pests And Yield Of Double-cropping Rice In Jiangxi Province

Rice is the main food crop in Jiangxi Province.Diseases and pests are one of the important factors restricting the high and stable yield of rice.Application of nitrogen fertilizer can not only promote the growth of rice,but also affect the occurrence of diseases and pests.This study focused on the effects of nitrogen fertilizer on the occurrence of main diseases and pests and yield of double cropping rice in different ecological regions of Jiangxi Province.in the hope of providing theoretical basis for high yield cultivation of double cropping rice in above area.In special,the correspoding experiments were performed in Nanchang,Shanggao and Ji’an（latitude from high to low）of Jiangxi Province from 2018 to 2020.The main results are listed as follows:（1）Occurrence of main diseases and pestsIn 2018-2019,two seasons rice field experiment was carried out in the Shanggao and,Ji’an countries Five treatments with total net nitrogen application of 0-334 kg·hm^-2N-1-N-5)were set at the ratio of base fertilizer,tiller fertilizer and panicle fertilizer of 5:3:2during the whole growth period,and three different varieties were set under each treatment.The results show that the main diseases and pests of late rice in 2018 were sheath blight（Rhizoctonia solani Kuhn）,rice disease（Ustilaginoidea oryzae）,rice blast（Pyricularia grisea）,two moth（Chilo suppressalis）,vertical rice leaf moth（Cnaphalocrocis medinalis）and rice planthopper（Nilaparvata lugens）.And the main diseases and pests of early rice in 2019 were Rhizoctonia solani Kuhn（Rhizoctonia solani Kuhn）,Chilo suppressalis（Chilo suppressalis）,Cnaphalocrocis medinalis（Cnaphalocrocis medinalis）and Nilaparvata lugens（Nilaparvata lugens）.With the increase of N application,the severity of main diseases and insect pests in rice also increased.There was a significant difference between the treatment without N application and the treatment with N application,and the occurrence of diseases and insect pests with pure N application of 334 kg·hm^-2 was the most serious.In 2019,four common late Japonica Rice Varieties in Jiangxi Province（Nanchang and Shanggao）were used as experimental materials,including Yongyou 538,Xiaoyechishu,Yongyou 1538 and Yangchan 1601,Five nitrogen application rates of 0～345 kghm^-2（N₁～N₅）were set.The ratios of basal fertilizer,tillering fertilizer and panicle fertilizer were6:3:1（M₁）,5:3:2（M₂）,4:3:3（M₃）,3:3:4（M₄）and 2:3:5（M₅）,respectively.The effect of nitrogen fertilizer on the spike rate and disease index of rice cursive disease in late stalk rice.The results showed that with the increase of nitrogen application rate(0～345 kg·hm^-2),the IPR and DI of RFS increased significantly.In the early stage,the application of nitrogen fertilizer had little effect on the occurrence of RFS,but the late application of nitrogen fertilizer resulted in serious RFS（M₅ treatment）.There was a significant positive correlation between the damage of main rice diseases and insect pests and the amount of nitrogen fertilizer.（2）Chemical control of main rice diseases and insect pestsIn 2020,four nitrogen application rates（N-1～N-4）were set for early and late rice at Shanggao,and three different pesticides/fungicides were set for each rice main diseases and pests under each treatment.With the increase of pure nitrogen application rate(0～248kg·hm^-2),the control effect of fungicides/pesticides on main diseases and pests decreased,including Chilo suppressalis,Cnaphalocrocis medinalis,Rice planthopper,Rice sheath blight,Rice false smut,and Rice blast..There was significant difference between the treatments with or without nitrogen fertilizer,and the control effect of no pure nitrogen treatment was the highest.（3）Yield of double cropping rice in Jiangxi Province.Two rice field trials were conducted in Shanggao and Ji’an from 2018 to 2019.Under the condition of 5:3:2 of the total basal fertilizer,tiller fertilizer and ear fertilizer,five treatments were set up,which were 0-334 kg·hm^-2（N-1～N-5）,and three different varieties were set under each treatment.The effects of different nitrogen fertilizer amount on the occurrence,yield and yield components of different varieties of double-cropping rice were studied.The results showed with the increase of N application,the rice yield increased first and then decreased.There was a significant difference between the treatments with or without N application,and the highest yield of rice was obtained in the treatment of pure nitrogen(167 kg·hm^-2).In 2019,four common late Japonica Rice Varieties in Jiangxi Province were used as experimental materials,including Yongyou 538,Xiaoyechishu,Yongyou 1538 and Yangchan 1601 in Nanchang and Shanggao.Five nitrogen application rates of 0-345 kghm^-2（N₁-N₅）were set.The ratios of basal fertilizer,tillering fertilizer and panicle fertilizer were 6:3:1（M₁）,5:3:2（M₂）,4:3:3（M₃）,3:3:4（M₄）and 2:3:5（M₅）,respectively.The yield of rice under different treatments were explored.The results showed with the increase of N application,the rice yield increased first and then decreased,the yield of all late japonica rice reached the highest when the total nitrogen application rate was 225 kg·hm^-2（base fertilizer:tiller fertilizer:panicle fertilizer=4:3:3）.