| Scientific fertilization is one of the important technical ways to achieve high and stable yield of maize.It is play important role to improve maize yield,reduce fertilizer loss and realize sustainable agricultural development.It is always a difficult problem to determine the optimal recommended fertilizer rate.Data derived from 52 experimental sites in Liaoning Province of China were conducted to study the characteristics of maize yield,nutrient uptake,and estimate the balanced nutrient requirements at different yield potential using the QUEFTS model.And levels of soil nutrient supply in Liaoning province was graded,and fertilizer recommendation according to different levels of soil nutrient supply.At the same time,the effects of different potassium application rates on maize yield and related parameters were mainly analyzed based on multi-year and multi-site field experiments of potassium fertilization,in order to verify the feasibility of the recommended potassium fertilizer application in the previous section.In addition,the related parameters of soil nitrogen supply and nitrogen fertilizer agronomic efficiency were further studied.The main findings are as follows:(1)Through 300 field experiments at 52 experimental sites in Liaoning Province,the average yields of maize were 8858 kg/ha,with a range of 2543~10427 kg/ha.Of these,17.3%and 19.3%of the output data were distributed in the range of 8000~9000 kg/ha and9000~10000 kg/ha.The average uptakes of nitrogen,phosphorus and potassium in the upper part of corn field were 176.1 kg/ha,36.9 kg/ha,and 134.8 kg/ha,respectively.The average harvest index of N,P and K for maize was 0.61,0.81 and 0.23,respectively.About 61%N,81%P and 23%K in the aboveground of the plant were accumulated in the grain,and about70.1%K accumulated in the straw.The average internal efficiencies of N,P and K were 54.3kg/kg,251.5 kg/kg and 78.2 kg/kg,respectively.In other words,16.7 kg N,3.8 kg P,and 11.4kg K were required to produce 1000kg of grain.(2)The coefficients of the two boundary lines of maximum nutrient accumulation(a) and maximum dilution(d)of nitrogen,phosphorus and potassium,respectively,were aN=34.1,dN=93.3,aP=151.8,dP=410.9,aK=40.2 and dK=184.4.The QUEFTS model predicted a linear–parabolic–plateau curve for balanced nutrient uptake.The nutrient requirements exhibit linear increase as the yield target approached to approximately 60%–70%of the yield potential,i.e.16.7 kg N,3.8 kg P,and 11.4 kg K were required in order to produce 1000 kg grain.Until yield target reached the yield potential,the balanced nutrient uptake is a plateau curve.(3)The average optimum recommended N,P and K rate for maize in Liaoning Province were 177.7 kg/ha and 116.4 kg/ha and 125.1kg/ha,respectively.Therefore,the average of corresponding theoretical yield of optimum recommended N,P and K rate were 10068.2kg/ha,10329.6 kg/ha and 10635.3 kg/ha,respectively.(4)The average optimum recommended N rates were 185.3 kg/ha,172.8 kg/ha and148.1 kg/ha at the low,middle and high levels of soil N supply,and the corresponding theoretical yield of optimal N rate averages were 9788.0 kg/ha,10672.0 kg/ha and 10854.9kg/ha respectively.The average optimum recommended P rates were 136.4 kg/ha,123.0kg/ha and 125.5 kg/ha at the low,middle and high levels of soil P supply,while the corresponding theoretical yield averages were 9804.3 kg/ha,10461.3 kg/ha and 10869.1kg/ha,respectively.The average optimum recommended K rates was 139.8 kg/ha,130.2kg/ha and 107.1 kg/ha at low,medium and high levels of soil K supply,and the corresponding theoretical yield averages were 10330.3 kg/ha,10561.9 kg/ha and 10812.9 kg/ha.(5)Potassium fertilizer application could significantly increase grain yield for maize.More importantly,the application of K had no significant effect the grain K concentrations for maize.Conversely,the K application significantly increased the straw K concentration.The performances of grain yield,agronomic efficiency and K fertilizer contribution rates in in following order:K2 treatment>K3 treatment>K1 treatment.The K fertilizer contribution rate and agronomic efficiency in K2 treatment were 10.45 kg/kg and 17.9 kg/kg,respectively.Therefore,K2 treatment was beneficial to promote plant K uptake and had a significant effect on yield.Comprehensive consideration of all parameters,the reasonable K application for maize in Liaoning province should be in the range of 120~150 kg/ha.(6)The average maize yield in no N treatment was 6.85 t/ha,the average maximum yield was 9.70 kg/ha.According to different experimental sites,the optimal recommended N rates were in the range of 111.50~349.29 kg/ha.The average soil N supply in Liaoning Province was 221.52 kg/ha,and in the range of 87.90~368.25 kg/kg.The average soil nitrogen supply intensity was 0.47,and ranged from 0.30 and 0.72.The results indicated that the source of plant nutrient uptake depended partly on soil to provide nutrients and partly on the application of nitrogen fertilizer for nitrogen supplement.The average soil N agronomic efficiency was 35.10 kg/kg,ranged from 18.06 and 63.30 kg/kg;the average N agronomic efficiency was 12.38 kg/kg,and ranged from 3.98 and 24.21 kg/kg.Compared with the two parameters,the value of soil N agronomic efficiency was significantly higher,indicating that the plant N uptake mainly depends on soil supplying.(7)There was a significant negative power function relationship(R~2=0.47)between yield increase and soil N supply;while a significant negative linear function relationship(R~2=0.818)between yield increase and relative yield;a significant positive exponential function relationship(R~2=0.609)between yield increase and nitrogen fertilizer agronomic efficiency.Among them,there was a significant negative linear correlation(R~2=0.695)between soil N supply and soil N agronomic efficiency.The correlation between relative yield and soil nitrogen supply reached a extremely significant level(R~2=0.99).The results indicated that the relative yield(Ry)can be used as one of the indicators of soil support. |
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