Cultivars And Soil Factors Affecting Grain Mn Concentration Of Wheat In Main Wheat Production Regions Of China

Manganese is a necessary trace element for human body and crops.Wheat is one of the three main grain crops in China,with a sowing area of 23570 thousand hectares and a yield of136.95 million tons.Therefore,it is of great significance to explore changes of the grain Mn concentration among wheat cultivars and the corresponding soil factors,for regulating grain Mn concentration and optimizing mineral nutrition quality of high-yield wheat.In the present study,field experiments were conducted in Northwest dry-farming wheat area（DW）from2017 to 2020,Huanghuai wheat-maize rotation area（WM）and Southern rice-wheat rotation area（RW）from 2016 to 2020.At maturity,wheat and soil samples were collected to analyze the wheat yield,the biomass and concentration of nitrogen,phosphorus,potassium,sulfur,calcium,magnesium,iron,Mn,zinc and copper in grains,stems,leaves and glumes,as well as soil p H and the concentrations of total nitrogen,organic matter and available nutrients.The differences of wheat yield and grain Mn among locations,cultivars and years,as well as the soil factors affecting grain Mn were studied.The relationships between grain Mn and the yield,biomass,yield composition,and other nutrient concentration,uptake and utilization of wheat were clarified.Main results are as follows:1.There were significant differences in yield and grain Mn concentration of main wheat cultivars in main wheat production regions of China.The wheat yield was in the following order:WM>RW>DW,with the average value of 8.1,5.9 and 5.9 t·hm^-2,respectively.The Mn concentration in wheat grains was in the following order:RW>DW>WM,with the average value of 46.9,45.4 and 41.4 mg·kg^-1,and 38%,17%and 36%of cultivars exceeded the upper limit of nutrient critical value 48.7 mg·kg-1,respectively.Therefore,it should be paid more attention to the regulation of manganese nutrition in wheat grains.2.The yield and Mn uptake of wheat cultivars were the main factors affecting the Mn concentration of grains.In DW and WM,the grain Mn concentration was correlated significantly negatively with the yield,biomass,harvest index,panicles and grains per panicle of wheat,while positively with the Mn uptake of aboveground and grains.In RM,the grain Mn concentration was positively correlated with panicle number,aboveground Mn uptake and grain Mn uptake,but negatively correlated with 1000 grain weight and Mn harvest index.Therefore,it is beneficial to resolve the problem of excessive Mn concentration by increasing the yield and reducing the aboveground Mn uptake and grain Mn uptake.3.There were significant interactions between Mn concentration in wheat grains and uptake and utilization of other nutrients.In DW,the Mn concentration in grains was significantly positively correlated with the concentrations of N,P,S,Fe,Zn and Cu in grains,the aboveground uptake of N,P,Zn and the grain uptake of Zn,while significantly negatively with the grain K,the grain uptake of uptake,and the harvest indexes of N,P,K,S,Ca,Mg,Zn and Cu.In WM,the Mn concentration in grains was significantly positively correlated with the grain concentration of P,S,Mg,Zn and Cu,and the harvest index of grain S,Mg,Fe,Zn and Cu,but negatively correlated with the grain concentration of K and Ca,the aboveground uptake of N,K,S,Ca and Fe,and the grain upake of N and K.In RW,the Mn concentration in grains was significantly positively correlated with grain N,P,Mg and Fe concentrations,aboveground uptake of N,P and Mg,the grain uptake of N,P,Mg and Fe,and the harvest index of N,S and Zn,while significantly negatively correlated with grain Ca concentration,aboveground S uptake,and grain Ca uptake.Therefore,the synergistic uptake and utilization of nutrient elements is also an important way to regulate manganese nutrition in wheat.4.The Mn concentration in wheat grains was affected by soil p H and nutrient availability.In DW,the increase of soil available P could increase the grain Mn concentration,while soil available K could inhibit Mn uptake in grain.In WM,the grain Mn concentration was significantly negatively correlated with soil p H,and positively correlated with available Fe,available Cu and available Mn in WM.In RW,grain Mn concentration was significantly negatively correlated with soil p H,available Cu and total nitrogen.It is concluded that reajusting soil p H and available nutrient concentration could help regulate Mn nutrition in wheat grains.In conclusion,there was a dilution effect between wheat yield and Mn concentration.It is beneficial to reduce Mn concentration in wheat grains in each wheat region by increasing spike number,grain number per spike and 1000-grain weight,and by adopting high-yield cultivars.In addition,it is necessary to control the uptake and utilization of various nutrients in the proper range of soil total nitrogen,available Fe,available Mn,available Cu and p H based on the soil physical and chemical properties of wheat regions,so as to achieve high yield and high quality wheat production.