Characteristic Analysis Of Yield Gap And Nutrient Use Efficiency Gap Of Winter Oilseed Rape In Yangtze River Basin

Oilseed rape is widely cultivated as the high economic value around the world.China has contributed 20% of the global rapeseed production with 7.5×106 ha of planting area.Nevertheless,the self-sufficiency rate of edible oil is still less than 40% in China.The Yangtze River Basin(YRB)has sufficient resources,including light,heat,water,and soil,which is the major rapeseed production area.Oilseed rape is planted in winter and rotation with rice,maize or other summer crops.Winter oilseed rape(WOSR)has a long growth period and a high nutrient requirements.Farmers‘ enthusiasm for planting WOSR was not so high due to the low returns,which led the extensive management practices.Further improvement of yield and efficiency will be great significance for the sustainable oilseed rape industry development.In this study,we divided the WOSR planting area into five zones: the low and high altitude areas in the upper reaches of YRB(L-URY and H-URY),the double and triple cropping system areas in the middle reaches of YRB(D-MRY and T-MRY),and the lower reaches of YRB(LRY).On the base of the field experimental data with statistical data,we built a database of WOSR yield,fertilizer rate and nutrient use efficiency.Combining the boundary line system and synthesis analysis,we focused on the current oilseed rape yield and nutrient use efficiency in different zones,and explored the yield limiting factors and the fertilizer saving potential.Consequently,providing scientific evidence to promote the development of regional oilseed rape industry.The main results are summarized as follows.(1)The oilseed rape production shown a steady growth trend and obvious interannual fluctuation during the past five decades in China.The variations of planting area and yield per unit area has contributed 47.3% and 49.3% to the fluctuation,respectively.The contribution of yield variation was 63.3% in 1970 s,and decreased to 44.3% in 2000 s.The decreasing trend was also appeared in YRB.The interannual fluctuation of yield per unit area was mainly affected by climatic factors.The contribution of climatic factors was more than 70%,and far higher than that of social factors.The trend-yield induced by social factors improved year by year,but the climate-yield induced by climatic factors changed without rules.(2)The yield variations of oilseed rape were influenced by the spatial distribution and trend of climate condition in some degree.The heat resources(average temperature(T)and accumulation temperature more than 0°C(AT0))were high in T-MRY and L-URY,and the diurnal temperature(DT)was large in D-MRY and LRY.The precipitation(P)was much higher in T-MRY than in the other zones.D-MRY and LRY have more abundant light resources(sunshine hour(S)and radiation(R)).When the precipitation in the late period(P3-5)increased 10 mm,the WOSR yield decreased 12-39 kg/ha in the different zones.When the temperature in the early period(T9-11)increased 0.1°C,the WOSR yield decreased 53 kg/ha in D-MRY,the temperature in the late period(T3-5)increased 0.1°C,the WOSR yield decreased 40 kg/ha in T-MRY.The WOSR yield increased 39 kg/ha when the diurnal temperature in the late period(DT3-5)increased 0.1°C in L-URY,and increased 29 kg/ha when the total radiation(R)increased 10 MJ/m2 in LRY.(3)The average actual yield(Yact),experimental yield(Yexp),attainable yield(Yatt)and potential yield(Yp)were 1810,2437,3702 and 3996 kg/ha,respectively.The yield benchmarks were generally high in L-URY and LRY,followed in D-MRY,and low in H-URY and T-MRY.Total yield gap(YGt)was 2187 kg/ha in the region.Farmers have only achieved 33%-53% of potential yield across the zones.The yield gaps caused by crop nutrition management,cultivation management,and uncontrollable factors were 16%,32% and 8%,respectively.(4)The partial factor productivity(PFP)of N,P and K for WOSR across the zones was 6.5-11.9,22.4-38.0 and 27.1-48.3 kg/kg,respectively.And the recovery efficiency(RE)of N,P and K was 13.3%-28.4%,9.1%-20.0% and 21.7%-42.5%,respectively.Optimal fertilization improved PFPN and RE of N,P and K,but had a negative impact on PFPP and PFPK as decreasing N rate and increasing P and K rate.The total efficiency gap of REN,REP and REK was 32.6%,15.5% and 11.7%.Crop cultivation management was the major limiting factor,but nutrition management was equally important for N efficiency gap.(5)The development of ?high yield,fertilizer saving,and high efficiency? model mainly depend on the improvement of agronomic practices.Optimal fertilization,timely drainage,high density planting,suitable sowing,disease control,weed control,transplant,residue retention and tillage increased WOSR yield at 21.1%,35.3%,17.1%,18.6%,21.6%,45.6%,15.2%,10.8% and 5.1%,respectively.Fertilizer application method,N type and N management increased N efficiency at 14.9%,11.0% and 29.5%,respectively.