Effect Of Nitrogen And Phosphorus Fertilizer Rate On Yield,Nutrient Utilization And Grain Mineral Nutrient Quality Of Wheat In Dryland

Wheat is the major food crop for residents living in northern China, and is the main sourceof essential mineral elements, such as zinc, calcium, iron and so on. A6-year continuedexperiment was conducted to investigate the effects of different ratess of N, P applied onwheat yield, nutrient use efficiency and grain mineral nutrient quality, and to explore therelationships among rainfall, fertilizer rates and wheat yield, nutrient use and mineral nutrientquality. The objectives were to optimize the management of water and fertilizer, and providea theoretical basis for high yield, high quality, high efficiency and sustainable development ofagricultural production in dryland of China. The main results were as follows:1. With increasing N supply wheat yield significantly increased, and reached the highestvalue of6244kg ha^-1at the N rate of240kg N ha^-1, increasing by124%compared to thecontrol （without nitrogen fertilizer application）. But there was not significant differencebetween the rate of240and360kg N ha^-1. Nitrogen, phosphorus and potassium accumulationalso increased and reached the greatest value of200kg ha^-1,20kg ha^-1and121kg ha^-1at therate of320kg N ha^-1, respectively, increasing by274.7%,64.5%and183.4%. Nitrogenrequirement for100kg grain significantly increased, but phosphorus requirement remarkablyreduced, potassium requirement first decreased and then increased. The partial factorproductivity （PFP） and use efficiency of nitrogen fertilizer decreased, while those forphosphorus fertilizer increased; Rainfall affected the PFP and the accumulations of total N, Pand K, i.e. they increased by the elevated rainfall that ranged from269to422mm, anddecreased by the rainfall with more than422mm.2. With N-input incraese, N, Fe, Zn, Cu, Cr, Ni, Pb, Se and Co contents in wheat grainsignificantly increased. Compared to the control, the contents of Cr, Ni, Pb, Se and Co inwheat grain at the N rate of160kg ha^-1reached the highest value and increased by30.4%,7.0%,45.0%,57.1%and32.5%, respectively, while the contents of N, Fe, Zn and Cu at the Nrate of240kg ha^-1reached the highest value, and increased by44.4%,37.1%,12.0%and 37.5%, respectively; With the increasing rainfall before the wheat sowing, the contents of P,Mg, Fe, Mn, Zn, Cu, Ni and Cd in wheat grain significantly increased. The contents of P, Znand Cd reached the highest value of3.2g kg^-1,27mg kg^-1and40.1μg kg^-1with the rainfall of422mm, while those of Mg, Fe, Mn, Cu and Ni reached the highest value of1117,4,35,4.3and0.70mg kg^-1with the rainfall of484mm, respectively.3. With increasing phosphate fertilizer supply, wheat yield, N, P and K accumulations inthe plant significantly increased, and reached the highest value of5703,145.9,18.5and93.5kg ha^-1at the rate of100kg P2O5ha^-1with increase by32%,18.0%,47.6%and27.4%,respectively, and there was not significant difference between the rate of100and150kg P2O5ha^-1. Phosphorus requirement for100kg grain increased, but nitrogen and potassiumrequirement significantly decreased. PFP of N fertilizer increased significantly, while that ofP fertilizer reduced. Nitrogen accumulation and nitrogen requirement for100kg grain, useefficiency of P and K fertilizer significantly increased by the increase of rainfall with rangingfrom269to386mm, and decreased with the rainfall being above386mm. Nitrogen useefficiency reached the highest of45.9kg kg^-1with the rainfall of478mm.4. With increasing phosphate fertilizer supply, the contents of P, K, Ca, Mg, Cr, Pb, Seand Co in wheat grain significantly increased, and reached the highest value at the rate of100kg ha^-1with the increase by18.1%,8.8%,3.5%,7.2%,32.8%,61.1%,22.2%and35.6%,respectively, compared to the control, while the contents of N, Mn, Zn, Cu and Nisignificantly decreased, and the contents of P, Fe, Mn, Cu, Cd and Ni in wheat grain increasedwith the increase of rainfall before wheat sowing, the contents of P, Zn and Cd reached thehighest value with the rainfall of422mm, and those of Fe, Mn, Cu, Ni and Cd were highestwith the value of59,30,4.5,0.78kg kg^-1and14μg kg^-1, respectively, when the rainfall was484mm.5. The yield and biomass of wheat increased significantly with the increase of nutrientinputs, and the high-yielding varieties were more sensitive to nutrient inputs than thelow-yielding varieties. Under the condition of low nutrient inputs, the yield depended onpanicles per unit area and grain number per spike, but panicles per unit area dominated theyield under the condition of high nutrient inputs. Under the condition of low nutrient inputs,nitrogen and phosphorus recovery efficiency, agronomic use efficiency and partial factorproductivity of the high-yielding varieties were higher (i.e.6.3%-61.6%,52.1%^-122%,9.8～5%and31.2%～33.3%,58.9%～126.3%,7.0%～4.9%, respectively) than those of thelow-yielding varieties. Nitrogen and phosphorous partial factor productivity significantlydecreased by the high nutrient inputs, and the low-yielding varieties were more sensitive tofertilizer inputs than the high-yielding varieties. 6. With the nutrient inputs increase, the contents of N, Mg, Fe, Zn, Cu, Cr, Ni and Pb ingrain of different varieties wheat increased, but those of P, K and Mn decreased. The contentsof N, P, Mg, Fe, Zn, Cu and Ni in grain of different varieties wheat in unfertilized treatmentsreflected more genotype difference than those in the fertilized treatments, while the contentsof K, Ca, Mn, Cr, and Pb in fertilized treatments reflected more genotype difference thanthose in the control Treattments. There was a positive correlation between the contents of Pand N, Mg, Fe, Mn, Zn, and a positive correlation between the content of Zn and N, Fe, Mn.