| Water and nutrient are the main limiting factors of wheat production in dryland,fertilization with precipitation fluctuation is the fundamental way to promote efficient utilization of water and fertilizer in dryland wheat of Loess Plateau.In order to clarify the current situation of wheat fertilization management in dryland.The fertilization management survey was carried out in Wenxi and Hongtong counties of Shanxi Province and Sanyuan and Fuping counties of Shaanxi Province during 2016-2020;To clarify the relationship between precipitation and yield & efficiency,and to explore the optimal nitrogen application rate for simultaneous increase of yield and water and fertilizer use efficiency,the correlation between precipitation and yield formation in fallow period from 1983 to 2020 was analyzed.The study of the effects of rainfall year type and nitrogen rate(0,90,120,150,180,210,240 kg ha-1)on water and nitrogen utilization and yield formation of dryland wheat were carried out in Wenxi Dryland Wheat experimental base of Shanxi Agricultural University during 2009-2017;In order to further clarify the fertilization management measures for high yield and good quality of main varieties in this area,the screening research on wheat varieties(YH20410,YH618,YH805,JM92,LH6 and C6359)with high yield and good quality was carried out in dryland during 2018-2020.The main results are as follows:(1)The average yield in dryland region of loess Plateau was 4001 kg ha-1.The yield was divided into five levels,among which 14.8% of the farmers belonged to the high yield level in the research area.There were insufficient or excessive nitrogen application rates at different yield levels,among which 62 % were more than 173 kg ha-1,and mainly concentrated in low and medium yield farmers.(2)The mean precipitation during fallow period was 296 mm(June-September),accounting for 58 % of annual precipitation,and with the increase of fallow season precipitation,grain yield increased logarithmically(R~2=0.42*).(3)Year type classification method based on fallow season precipitation : wet year: Pi > Pm + 0.33δ;normal year: Pm-0.33δ≤ Pi ≤ Pm + 0.33δ;dry year: Pi < Pm-0.33δ.Pi is annual precipitation(mm);Pm is the average annual rainfall for many years(mm);δ is mean variance of annual rainfall(mm).Year types were divided based on fallow season precipitation(Wenxi,1983-2020): Dry year(fallow precipitation <220 mm),normal year(220 mm < fallow precipitation < 440 mm),wet year(fallow precipitation > 440 mm).(4)According to the year type classification method based on fallow season precipitation,the field experiment years from 2009 to 2017 were divided into two year types,2010-2011,2011-2012,2013-2014 and 2014-2015 were normal years.In normal years,compared with 210 kg ha-1,180 kg ha-1 significantly increased water consumption in 80-240 cm soil layer from jointing to anthesis by 22.7 %,significantly increased percentage of ear bearing tiller(PET)by 7 %,significantly increased dry matter accumulation from jointing to anthesis by 9%,increased yield by 5.5%,significantly increased WUE,NUE and PFP by 8.5%,17%,15%,respectively.2009-2010,2012-2013,2015-2016 and 2016-2017 were dry years.In dry years,compared with 210 kg ha-1,150 kg ha-1 significantly increased water consumption in 80-240 cm soil layer from jointing to anthesis by 36.6 %,significantly increased percentage of ear bearing tiller(PET)by 20.3%,significantly increased dry matter accumulation from jointing to anthesis by 14.8%,increased yield by 5.5%,significantly increased WUE,NUE PFP by 6.1%,36%,32%,respectively.The results also showed that the nitrogen rate of 150 kg ha-1 in dry year and 180 kg ha-1 in normal year could significantly increase the water consumption during jointing to anthesis,and the water consumption during jointing to anthesis was closely related to leaf area index at anthesis and the tiller percentage rate,and the leaf area index at anthesis,the tiller percentage rate,the jointing-anthesis,anthesis-maturity dry matter and nitrogen accumulation was closely related to yield and its components.(5)The rainfall during the fallow period from 2018 to 2020 was 245.5 mm and 288.9 mm,respectively.According to the classification method of fallow season precipitation,it belongs to normal year,and nitrogen rate was 180 kg ha-1.The yield of wheat varieties in different dryland was the highest of YH20410,reaching 4890 kg ha-1,which was significantly higher than YH805,JM92,C6359 and LH6,but not significantly different from YH618;the highest grain protein content of YH618 was 15.2%,which was significantly higher than YH20410 and C6359,but not significantly different from JM92,YH805 and LH6;YH618 had the highest N use efficiency and N uptake efficiency,which were 11.6 kg kg-1 and 0.61 kg kg-1,respectively.Therefore,the yield of dryland wheat in loess Plateau was low and varied greatly,and the phenomenon of excessive fertilization in farmers is serious.Apply nitrogen fertilizer scientifically according to fallow season precipitation,150 kg ha-1 in dry year and 180 kg ha-1 in normal year,and combined with high yield nitrogen efficient varieties,can realize high yield and high efficiency of water and nutrient,and promote high yield,high efficiency and safe production in dryland wheat region of loess Plateau. |
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