Effects Of Combined Application Of Organic And Inorganic Fertilizers On Soil Fertility And Winter Wheat Yield In Guanzhong Area

The Guanzhong area of Shaanxi Province is an important winter wheat grain production base in northern part of China.In order to increase crop yields,the area has severely overapplied chemical fertilizers,which has caused a decline in soil quality and serious pollution of the ecological environment.It is detrimental to the sustainable development of agriculture.Several studies have shown that combined application of organic and inorganic fertilizers can improve soil fertility,increase soil moisture and crop yields,and improve water use efficiency.However,the reasonable ratio of combined application of organic and inorganic fertilizers under rain-fed conditions in Guanzhong area needs further study.This study adopted the principle of equal nitrogen,used new organic fertilizers and inorganic fertilizers to mix in a certain proportion,respectively set six treatments: control treatment(CK,no fertilizer);full inorganic fertilizer treatment(M0);25% organic fertilizer combined with 75% inorganic fertilizer(M25);50% organic fertilizer combined with 50% inorganic fertilizer(M50);75%organic fertilizer combined with 25% inorganic fertilizer(M75);full organic fertilizer treatment(M100).We combined two-year field experiments and indoor cultivation trials to study the effects of different organic and inorganic fertilizer application ratios on soil nitrogen mineralization,soil physical and chemical properties,wheat yield and water use efficiency to provide an optimal application ratio of organic and inorganic fertilizers and theoretical guidance for scientific and reasonable field management in this area.The main findings are as follows:(1)In the indoor aerobic culture experiment,the fertilization treatments significantly increased the soil mineral nitrogen content and nitrogen mineralization accumulation.During the cultivation period,the soil ammonium nitrogen contents increased rapidly and then rapidly decreased under different fertilization treatments,and finally remained basically unchanged.The soil nitrate nitrogen and mineral nitrogen contents showed rapid increases at first and then gradually stabilized with the increase of cultivation time.After the experiment,there were significant differences in the accumulation of soil mineral nitrogen between different fertilization treatments(P<0.05),which was expressed as M0>M25>M50>M75>M100>CK.Compared with the CK treatment,the soil accumulated mineralized nitrogen and nitrogen mineralization rate of the combined application of organic and inorganic fertilizers increased by 58.1-325.2%.The soil accumulated mineralized nitrogen was fitted to the first-order kinetic equation,and the results showed that the fitting effects were good.(2)The combined application of organic and inorganic fertilizers can improve soil structure and nutrient content.The combination of organic and inorganic fertilizers treatments can improve soil physical property,reduce the bulk density of 0-40 cm depth,increase soil porosity,saturated water content and hydraulic conductivity.The two-year average bulk density was 3.3-7.8% lower than CK treatment,and the average porosity is 3.9-8.1% higher than CK treatment,and the effects were more significant as time increased.Compared with CK and M0 treatments,the combined application of organic and inorganic fertilizers significantly increased the >0.25 mm soil aggregates in the different soil layers,increased the average weight diameter(MWD),geometric mean diameter(GMD),and the stability of soil aggregates.In two study years,soil organic matter and total nitrogen content under the combined application of organic and inorganic fertilizers were significantly higher than those of the CK treatment,and the effects of high-volume organic fertilizers in replace of chemical fertilizers were better which increased with the time.(3)The combined application of organic and inorganic fertilizers can increase soil water content and water storage,and improve winter wheat yield and water use efficiency during the growth period of winter wheat.In the early growth period(seedling and overwintering stages),combined application of organic and inorganic fertilizers can significantly increase soil surface water content and increase soil water storage.The combined application of organic and inorganic fertilizers can significantly increase winter wheat yield,panicle number,thousandgrain weight and other yield components,and improve water use efficiency.In 2018-2020,the winter wheat yields of M75 treatment were highest,and increased by 110.8-136.3% compared with CK treatment and 18.7-23.1% compared with M0 treatment,respectively.In summary,among the different combination of organic and inorganic fertilizer treatments,the M75 treatment(75% organic fertilizer combined with 25% inorganic fertilizer)was beneficial to improve soil quality,increase soil physical and chemical properties,soil water,wheat yield,and water use efficiency in the Guanzhong area of Shaanxi Province.It could be the optimal application ratio of combined organic and inorganic fertilizers in the area.This study clarified the effects of different organic and inorganic fertilizer application ratios on soil fertility and winter wheat improvements in Guanzhong area of Shaanxi Province,and put forward a reasonable combined organic and inorganic fertilizer application ratio,which provided theoretical guidance for local fertilization strategies and field management measures.