Effect Of Planting Patterns And Nitrogen Fertilization On Soil Environment And Yield Of Winter Oilseed Rape

Oilseed rape is one of the most important oil crops in China.In recent years,the planting area of winter oilseed rape in northwest China has been increasing year after year with the global warming condition.However,due to the impact of drought and water shortage,the production of winter oilseed rape,its utilization efficiency of water and fertilizer,and the economic benefits are low.The technology of ridge film mulching and furrow planting(RFMF)can effectively improve the precipitation utilization efficiency,increase the soil moisture effectiveness,and improve the yield,water and fertilizer use efficiencies of maize and potato and so on.While its applicability to winter oilseed rape in northwest China is still unclear.In addition,the response of crops to nitrogen(N)fertilizers is dependent upon many environmental factors including water availability,ambient temperature and soil properties.RFFM has been suggested to have an effect on soil N-transport,N mineralization and plant N uptake through its effect on soil temperature and moisture.All of these factors may alter the responses of crops to N fertilization,affecting crop yield and their water and N use efficiencies.At present,there are few studies on the appropriate N amount applied to crops under RFMF,and are not systematically strong.In this paper,a3-year(2014-2017)field experiment was conducted to determine whether the RFMF cultivation pattern has the potential of improving winter oilseed rape productivity.The optimal N application rate for the maximum yield of winter oilseed rape under the RFMF cultivation pattern was also determined by measuring growth and physiological parameters,nutrition uptake,rhizosphere soil environment,yield and quality,and water and N use efficiencies of winter oilseed rape.Winter oilseed rape was planted in RFMF and flat planting(FP)patterns,both with six nitrogen(N)application rates:0,60,120,180,240 and 300 kg/hm~2,named N0,N60,N120,N180,N240 and N300,respectively.(1)RFMF pattern significantly increased the plant height,stem diameter,leaf area index,aboveground dry matter,and improved the root traits of winter oilseed rapeseed,and meanwhile improved the chlorophyll content by 11.11%~48.80%and the photosynthetic rate by 5.93%~32.54%,respectively.N application can significantly improve the growth and development of the above-and under-ground part of winter oilseed rapeseed,increase chlorophyll content and photosynthetic rate.Plant height,stem diameter,leaf area index,dry matter quality and root traits,as well as chlorophyll content and photosynthetic rate were basically in the trend of first rising and then decreasing with the increase of N rate,and reached the maximum in N240 treatment under RFMF pattern,and N180 treatment under FP pattern.(2)Compared to FP,RFMF significantly increased the N,phosphorus(P)and potassium(K)uptake in each organs(leaf,stem,pod wall and seed)of winter oilseed rape at seedling,flowering,and harvest stages,and the increase of N,P,and K uptake at harvest stage under RFMF pattern were 17.44%~61.27%,16.51%~58.25%,and17.85%~74.46%,respectively.The N,P,and K uptake in each organ of winter oilseed rape at seedling,flowering,and harvest stages were all firstly significantly increased and then basically kept stable with the increase of N application rate.At harvest,N,P and K uptake of winter oilseed rape in N240 under RFMF pattern were all significantly higher than those in N0,N60,N120 and N180,but had no significant differences with N300;N,P and K uptake in N180 under FP pattern were all significantly higher than those in N0,N60 and N120,however,no marked differences were found among N180,N240 and N300.(3)RFMF pattern markedly improved soil moisture content and soil temperature,but decreased soil oxygen concentration in the root zone(0-30 cm depth)of winter oilseed rape.Rhizosphere soil invertase,urease,alkaline phosphatase and catalase activities,and soil bacteria,fungi and actinomycetes abundances were also significantly higher in RFMF plots than in FP plots.Meanwhile soil microbial biomass carbon(SMBC)was increased,soil microbial biomass N(SMBN)was decreased,and nitrate-N and ammonium N were remarkably improved under RFMF pattern in comparison to FP.The soil water content mainly gradually decreased,and soil temperature and oxygen concentration did not vary obviously with the increase of N application rate.N application significantly increased rhizosphere soil enzyme activities,microbial population,SMBC,SMBN,nitrate-N and ammonium N contents.In all treatments,the highest soil enzyme activities and microbial population were found in N240 under RFMF pattern,while the lowest were occurred in N0 under FP.(4)Compared with FP,RFMF significantly increased seed yield by15.5%~37.7%,improved seed quality(oil and protein content),and increased oil production by 18.0%~48.4%.Seed yield and oil production increased at first and then decreased,while seed oil content decreased and seed protein content increased with the increase of N application rate.The economic benefit of winter oilseed rape were also increased firstly and then decreased when increased N application rate.The economic benefit of winter oilseed rape under RFMF pattern was less than that under FP when the N application rate was low(0-60 kg N/hm~2).When N levels increased to120-300 kg N/hm~2,the economic benefit of RFMF was greater than that of FP.Of all the treatments,N240 under RFMF gained the highest seed yield,oil production and economic benefit,and is a suitable cultivation and N application measure for winter oilseed rape.(5)Evapotranspiration(ET)was markedly decreased by 3.4%~11.0%,while precipitation utilization efficiency(PUE),water use efficiency(WUE)and N partial factor productivity(NPFP)of winter oilseed rape were increased by 15.6%~43.1%,25.5%~69.6%,and 15.4%~43.0%,respectively,under RFMF than FP.N application significantly improved PUE,WUE,N agronomic efficiency(NAE),N physiological efficiency(NPE),N recovery efficiency(NRE)and NPFP of winter oilseed rape,while these parametes were all markedly decreased when excessive N was applied.Under RFMF pattern,the highest PUE and WUE were occurred in N240,and the highest NAE,NPE and NRE were found in N180;however,NAE,NPE and NRE in N240 did not differ significantly with N180.Under FP pattern,N180 obtained the highest PUE,WUE,NAE,NPE and NRE.(6)In this study,methods of principal component analysis,grey correlation degree,and entropy weighted DTOPSIS were used to comprehensively evaluate the indice of growth,physiology,nutrient uptake,yield,quality,water consumption,water use efficiency,and economic benefit of winter oilseed rape.The results of the three evalution methods all showed that N0 treatment under FP pattern had the worst effect on winter oilseed rape,and the N240 treatment under RFMF pattern had the best effect.Thus,the N240 treatment under RFMF pattern in this study is the most suitable planting method and N application rate of winter oilseed rape in the northwest China.