| Winter rapeseed(Brassica napus L.)is focally distributed in the Yangtze river valleys of China,rotating mainly with paddy rice in cultivation.Located in the upper reaches of the Yangtze River,Sichuan Province is an important oilseed rape producing region in China,and its rapeseed production has become at the first place in China.With the changes in labor availability in the rural areas,agricultural production structures and management scales,transformation in rapeseed production techniques from manual operations,such as seedling raising and transplantion,to mechanized operations has become an inevitable trend.At the same time,as the emphasis of the country on agricultural ecological environment protection and reduction in chemical drug applicaction is put forward,the crop production forms of resource saving and environmentally friendly performing has become important and of high practical significance.To explore the high yield and efficient and environment friendly nitrogen management measures for rapeseed production in Chengdu Plain area,different nitrogen levels(0,135,180,135,180 kg N/hm~2)and different planting densities(15 x10~4,30 x 10~4 plant/hm~2)were tested in 2015-2016,2015-2017 in Guanghan City to studied their influences on rapeseed yield,nitrogen absorption,nitrogen utilization rate and the effects of nitrogen apparent balance.The main results are as follows:1.Compared with no nitrogen treatment(N0),increasing nitrogen application significantly or significantly increased the yield of two days of direct seeding rape.There was no significant difference in grain yield between two nitrogen treatments.In the range of nitrogen application 135-270kgN/hm~2,there was no obvious regularity in the change of grain yield in the year of 2015-2016,but in the year 2016-2017,the change trend was increased first and then decreased,and the maximum value of the nitrogen application level of 225kgN/hm~2(N225)treatment was reached.Under the same variety of P1,the grain yield of 2016-2017 treatments was higher than2015-2016 years,and the yield increased by 428.73,728.73,927.15,1418.10 and1233.98kg/hm~2,respectively.2.In the range of nitrogen application 135-270kgN/hm~2,the nitrogen absorption of stem,nitrogen absorption of kernaris shell,nitrogen absorption of grain and nitrogen absorption of plant showed a different trend in the two year.In the2015-2016 year,the performance was increased first and then descended,and reached the maximum value at the time of N225 treatment,and the value was 37.54,51.65,113.66 and 202.85kg/hm~2 respectively.In the 2016-2017 year,it increased with the increase of nitrogen application rate.The two experiment also showed that the agronomic utilization rate of nitrogen fertilizer was the same as that of nitrogen fertilizer,and it was significantly or significantly decreased with the increase of nitrogen application rate.The contribution rate of nitrogen fertilizer increased with the increase of nitrogen application rate,but the difference between treatments was not significant.In the 2015-2016 year,the nitrogen harvest index increased significantly or significantly higher than that of N0 treatment,but there was little difference in2016-2017 years.There was no significant difference in nitrogen harvest index between different treatments.3.In 2015-2016 years,increasing planting density was beneficial to increasing grain yield,but there was no significant difference in yield between density treatments.The number of pod per plant in M2 was significantly lower than that in M1 treatment.Nitrogen uptake,nitrogen uptake by hornnut shell and nitrogen uptake by M2 were significantly higher than those of M1 treatment.There was no significant difference in nitrogen uptake between different planting densities.The planting density had a significant effect on the agronomic utilization of nitrogen fertilizer,which showed that M1 treatment was significantly greater than that of M2 treatment.However,there was no significant effect on the partial productivity of nitrogen fertilizer,the contribution rate of nitrogen fertilizer and the nitrogen harvest index.In the last 2015-2016 years,the interaction between plant dry weight and nitrogen nitrogen application level and planting density was very significant,but the interaction effect of nitrogen level and planting density was significant in 2016-2017 years of grain number,1000 grain weight,grain nitrogen and nitrogen fertilizer apparent residual rate.4.There were significant differences in nitrogen apparent loss of nitrogen treatment(N135,N180,N225,N270)in the growing season of live rape(2015-2016years and 2016-2017 years).The nitrogen surplus in farmland increased generally with the increase of nitrogen application rate.In the 2015-2016 years,the apparent loss of nitrogen in the two treatments of N135 and N180 was very low,and the apparent loss of nitrogen in N270 treatment was the largest.In the 2016-2017 year,the apparent loss of nitrogen in farmland increased first and then decreased with the increase of nitrogen application rate,and reached the maximum in N225 treatment.Comparing the results of two years,the apparent nitrogen loss and nitrogen surplus of farmland treated with N application in 2016-2017 years were significantly higher than those in 2015-2016 years.The results of the two year also showed that nitrogen fertilizer application was controlled in the range of 135-180kg/hm~2,and the apparent loss of nitrogen and the surplus amount of nitrogen in farmland were relatively low,thus reducing nitrogen loss and reducing the soil nitrogen surplus.Comprehensive crop yield,nitrogen absorption and utilization as well as nitrogen apparent balance of farmland,under the system of rice oil tanker in Chengdu plain,the reasonable cultivation measure of high yield of rapeseed,efficient use of nitrogen fertilizer and friendly environment is nitrogen application 135-180kg/hm~2,and planting density of 300 thousand plant/hm~2 is suitable. |
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