Effects Of Chemical Fertilizer Reduction Combined With Humic Acid Biological Fertilizer On Soil Properties And Maize Growth

In northern China,the climate is cold and the utilization efficiency of chemical fertilizer is low.Therefore,there are some practical problems in agricultural production,such as the continuous increase of chemical fertilizer application,the decrease of soil physical and chemical properties,the increase of production cost,and the aggravation of agricultural non-point source pollution,which limit the increase of maize yield and the sustainable use of arable land.Therefore,corn was the study object,a two-year indoor simulation experiment was conducted to study the effects of humic acid bio-fertilizer on soil chemical and biological characteristics,physiological characteristics and nutrient absorption of maize under the condition of 15%(T2)and 30%(T3)reduction of chemical fertilizer compared with conventional fertilizer(T1),so as to clarify the effect of soil crop on humic acid bio-fertilizer.It can provide a reference for the application technology of chemical fertilizer reduction.The main results are as follows:1.The application of humic acid bio-fertilizer significantly increased soil fungal and bacterial numbers,and the number of flora increased with the increase of humic acid bio-fertilizer,with the increase of fungal numbers in the T2 and T3 treatments by 10.8%-144.4%and 13.8%-181.8%,compared with the T1 treatment,and the increase of bacterial numbers by 6.5%-40.5%and16.2%-47.4%,respectively in different stage.2.The application of humic acid bio-fertilizer with appropriate fertilizer dosage reduction(T2)significantly increased the activities of sucrase,urease,and catalase in soil,and the activities of sucrase and urease significantly increased by 34.9%-46.7%and 11.4%-21.6%,at the maize tasseling stage,respectively,and catalase increased by 6.5%?13.4%,at the nodulation stage.Humic acid bio-fertilizer enhanced the activity of soil carbon and nitrogen metabolism in the late stage of maize growth,and it had a certain promoting effect on soil humification progress.3.The humic acid bio-fertilizer had a certain"slow-release"effect on soil nitrogen transformation,and the contents of available nitrogen in the soil before the bolting stage of maize in the T2 treatment decreased by 7.1%-22.7%compared with T1,which guaranteed the nitrogen supply capacity of the soil after the tasseling stage.The content of available phosphorus and potassium increased by 6.4%-121.0%and 2.3%-35.2%,respectively in ddifferent stage.The effect of humic acid on the activation of phosphorus and potassium was more significant with the increase of humic acid.4.Humic acid bio-fertilizer promoted the absorption of nitrogen,phosphorus and potassium in maize plants.The total nitrogen and potassium contents in T2 treatment increased by 1.3%-20.1%and 5.8%-37.3%,respectively,especially the absorption of potassium increased with the increase of humic acid bio-fertilizer,and the phosphorus content in jointing stage was significantly improved than that in T1 treatment.However,humic acid bio-fertilizer reduced the absorption capacity of calcium and magnesium in maize plants after jointing stage.5.The application of humic acid bio-fertilizer enhanced photosynthetic carbon assimilation and conversion capacity of maize plants especially in the T2 treatment,the activities of1,5-diphosphonyl ribulose carboxylase and phosphoenolpyruvate carboxylase significantly increase,and the activities of sucrose phosphate synthase and sucrose synthase by 22.7%-84.4%and17.8%-135.7%,respectively.The contents of soluble sugars,reducing sugars and starch of plant increased by 0.9%-72.8%,6.3%-25.8%and 1.0%-127.7%,respectively,the application of humic acid bio-fertilizer enhanced the photosynthetic carbon metabolism activity of plants.6.The application of humic acid bio-fertilizer increased the nitrogen metabolism activity of maize plants,nitrate reductase activity of T2 treatment increased by 33.0%-45.0%,and the activities of glutamine synthetase and glutamate synthase increased by 26.7%?44.7%and 34.3%?54.3%in the jointing stage,respectively,simultaneously improve the nitrogen assimilation and transformation process.the soluble protein content of plants in the jointing stage and tasseling stage increased significantly by 15.8%-18.5%and 15.0%-24.2%,respectively comparing with the T1 treatment.7.The activity of antioxidant enzymes and the content of antioxidant substances were increased,so the systemic resistance of maize plants were strengthened with the application of humic acid bio-fertilizer,and T2 treatment was more significant.The activities of superoxide dismutase,catalase,peroxidase and ascorbate peroxidase were increased at jointing stage,while the activities of peroxidase and ascorbate peroxidase were increased at tasseling stage.The ascorbate-glutathione cycle showed higher activity at the jointing and tasseling stages,and the malondialdehyde content decreased by about 10.0%,the protection of plasma membrane integrity was strengthened.The application of humic acid bio-fertilizer(replace potassium at the same amount)at 85%or70%of the conventional chemical fertilization promoted maize growth,biomass in maize aerial parts enhanced 112.3%?106.2%or 88.8%?120.7%,and improved the metabolic activity of the soil-crop system and fertilizer utilization.For the comprehensive analysis,319 kg of urea(N 46%),191 kg of diammonium phosphate(N 18%,P₂O₅ 46%),50 kg of potassium sulfate(K₂O 50%),and400 kg of new humic acid bio-fertilizer(fulvic acid 65%,K₂O 12.5%)were applied as recommended fertilization mode per hectare for maize in the study area.