Effect Of Mineral Potassium Fulvic Acid On Fertilizer Reduction Of Soybean Growth And Rhizosphere Soil Nutrient

Soybeans possess noteworthy nutritional components and constitute a pivotal oilseed crop in China.The diverse modes of soybean consumption have led to a continual increase in demand,both in the domestic and global marketplaces.The high import volume of soybeans in China has made it challenging to satisfy local needs.Therefore,enhancing soybean production and quality is an urgent societal issue that needs to be addressed.Mineral potassium fulvic acid（MPFA）is a type of humic acid,characterized by its low molecular weight,numerous active functional groups,and high reactivity.MPFA can react with nutrients in the soil,promoting crop growth,while the humic substances within it can ameliorate soil conditions.In this study,a field experiment was conducted to compare the effects of MPFA combined with a 20%reduction in fertilizer application（T2）and varying MPFA dosages of 7.5kg·hm^-2（T3）,15 kg·hm^-2（T4）,22.5 kg·hm^-2（T5）,and 30 kg·hm^-2（T6）against conventional fertilization（T1）.The focus was on the impact on soybean yield,metabolism,seed quality,and soil nutrient content.The primary results are as follows:1.Under the conditions of reduced fertilizer application,the MPFA enhanced the total nitrogen,total phosphorus and total potassium contents in various soybean plant organs.The most considerable nutrient uptake of nitrogen and phosphorus occurred when conventional fertilization was reduced by 20%and combined with MPFA dosage of 22.5 kg·hm^-2（T5）.In comparison to conventional fertilization,the total phosphorus contents in root tissues during the initial flowering stage respectively increased by 13.2%.During the pod-setting stage,the total nitrogen and phosphorus in pod shells increased by 16.0%and 23.3%compared to the T1 treatment.The most considerable nutrient uptake of potassium occurred when conventional fertilization was reduced by 20%and combined with an MPFA dosage of 30 kg·hm^-2（T6）,which increased by 5.0%～34.0%compared with the control.2.Under the conditions of reduced fertilizer application,the MPFA improved the activity of key enzymes involved in the carbon metabolism of soybean plants,with the most pronounced effect observed in the T5 treatment.During the initial flowering stage,the activities of sucrose phosphate synthase（SPS）,invertase（AI）,and the total sugar content in T5 treatment significantly increased by 16.1%,6.0%,and 11.2%,respectively,compared to T1 treatment.In the pod-setting stage,the total sugar content in the T5 treatment increased by 15.5%compared to T1.During the seed-filling stage,the activities of sucrose synthase（SS）,AI and the total sugar content in the T5treatment significantly increased by 10.1%,16.9%,and 13.9%,respectively,compared to the T1treatment.3.Under the conditions of reduced fertilizer application,the MPFA enhanced the activity of key enzymes involved in nitrogen metabolism in soybean plants.The fertilizer was reduced by20%,the application of MPFA increased significantly compared with the T1 control in the application of GOGAT and GDH at 22.5kg·hm^-2（T5）,and the NR and GS activities at 30kg·hm^-2（T6）compared with the T1 control.4.Under the conditions of reduced fertilizer application,the MPFA improved soybean yield,number of pods per plant,and seed weight per plant,but had no significant effect on the 100-seed weight,with the most pronounced effect observed in T5 treatment.The seed weight per plant and number of pods per plant in the T5 treatment significantly increased by 5.1%and 7.5%,respectively,compared to the T1 treatment,and the yield significantly increased by 4.8%compared to the T1 treatment.5.Under the conditions of reduced fertilizer application,the MPFA enhanced the quality of soybean seeds.In the T5 treatment,the protein content increased by 2.5%compared to the T1treatment,while also increasing the Mn,Ca,Cu,Fe,Mg and Zn contents in the seeds,with no effect on Na content.6.Under the conditions of reduced fertilizer application,the MPFA improved the contents of available nitrogen,available phosphorus,available potassium and organic matter content in rhizosphere soil.During the seed-filling stage,the available nitrogen and organic matter contents in the T5 treatment increased by 13.5%and 11.4%,respectively,compared to the T1 treatment.