Effects Of Slow/controlled Release Nitrogen Fertilizer Management On Growth,Nitrogen Absorption And Utilization And Nitrogen Balance Of Direct-seeded Rapeseed

Rapeseed is one of the main oil crops in China,and plays an important role in the protection of edible vegetable oil.In order to adapt to the development trend of rapeseed light,simplified and mechanized production,high density direct seeding of rapeseed has become an important planting mode.In order to explore the application effect of controlled-release nitrogen fertilizer in direct-seeding rapeseed production,the effects of different types of controlled-release nitrogen fertilizer and mixing ratio of controlled-release nitrogen on Agronomic characteristics,yield,nitrogen uptake and utilization and nitrogen balance of high-density direct-seeding rapeseed were studied under rice-oil rotation system in Chengdu Plain from 2016 to 2017 and 2017 to 2018 respectively.In the field experiment of 2016-2017,different types of nitrogen fertilizers(common urea PU,resin coated urea BU,polypeptide urea DU,coated compound fertilizer BF)and the number of times of nitrogen application(one-time base application of nitrogen fertilizer T1,base fertilizer nitrogen + multiple application of topdressing at seedling stage T2)were used under the same amount of nitrogen application(180kg N/hm2).In the field experiment of 2017-2018,the split plot experiment was designed with two factors: different nitrogen application rates(135 kg N/hm2,180 kg N/hm2)and the mixing ratio of controlled release nitrogen(resin coated urea 0%,33%,50%,67%,100% of total nitrogen application,respectively).The test results show that:(1)Different types of nitrogen fertilizer and times of nitrogen application had no significant effect on dry matter accumulation of direct-seeded rapeseed at maturity stage.Compared with common urea disposable basal treatment(PUT1),BFT2 treatment,BUT1 treatment,DUT2 treatment and PUT2 treatment significantly increased grain yield.Nitrogen uptake of direct seeding rapeseed at maturity stage was significantly lower in resin coated urea BU treatment than in common urea PU treatment and coated compound fertilizer BF treatment.The agronomic efficiency,partial productivity and contribution rate of nitrogen fertilizer in BU treatment were significantly lower than those in PU,DU and BF treatment.There was no significant difference in apparent nitrogen loss among different nitrogen fertilizer types.The residual inorganic nitrogen in BF treatment was significantly higher than that in PU treatment,and the surplus of nitrogen in BF treatment was significantly lower than that in other three nitrogen fertilizer types(PU,BU,DU).BF,BU and DU treatment had higher apparent nitrogen residue rate than PU treatment,and lower apparent loss rate than PU treatment.(2)The dry matter accumulation of CU1(100% controlled-release urea)treatment at maturity stage was significantly higher than that of other mixing proportion treatments,and the dry matter weight of CU1(100% controlled-release urea)treatment was N180 > N135,but the difference was not significant.The interaction of nitrogen application rate and blending ratio of controlled-release urea had a significant effect on the grain yield of direct-seeded rapeseed.Compared with other treatments,the grain yield of direct seeding rapeseed increased with the increase of the blending ratio of controlled-release urea,and the yield of CU1(100% controlled-release urea)treatment was significantly higher than that of other treatments.The grain yield of N180 treatment was higher than that of N135 treatment.Compared with other treatments,CU1(100% controlled-release urea)treatment significantly increased nitrogen uptake at maturity stage.Nitrogen uptake of plants treated with N180 was significantly higher than that treated with N135.The agronomic utilization rate,partial productivity and apparent utilization rate of nitrogen fertilizer in CU1(100% CRU)treatment were significantly higher than those in other CRU treatments.Compared with different blending ratios of controlled-release urea,the residual inorganic nitrogen of CU1 treatment was slightly higher than that of CU3 treatment,but significantly higher than that of other blending ratios.The apparent nitrogen loss,nitrogen surplus and apparent loss rate of CU1 treatment were significantly lower than those of other treatments.(3)In summary,one-time basal application of slow/controlled release nitrogen fertilizer can be used in direct seeding rape production.Resin coated urea(BU)one-time basal application can improve grain yield compared with ordinary urea one-time basal application.When controlled-release urea was mixed with common urea,the proportion of controlled-release urea should be more than 50%,which was beneficial to the high-yield,high-efficiency and environment-friendly production of direct-seeded rapeseed.