Effects Of Reducing Seaweed Composite Fertilizer Application On Wheat Corn Growth And Nitrogen Utilization

Due to the current situation of excessive use of chemical fertilizers has led to soil compaction,soil acidification,and pollution of the water environment.It is urgent to reduce the application of chemical fertilizers,to increase fertilizer use efficiency,to improve soil fertility,and to protect the environment while ensuring stable and increased crop yields.As a new type of fertilizer,seaweed compound fertilizer contains small molecule alginate and other substances,has active substances such as trace elements and minerals and amino acids required for crop growth,which can effectively promote crop growth and development.Therefore,9 treatments were set up in this experiment,including no fertilizer（CK）,no nitrogen fertilizer（BN）,no phosphorus fertilizer（BP）,no potassium fertilizer（BK）,and conventional fertilizer（T1）as the control,and seaweed compound fertilizer（T2）with equal amount of nutrients and seaweed compound fertilizer treatments with 10%（JS1）,20%（JS2）,and 30%（JS3）reduction.Effects of various treatments on plant biological traits,leaf chlorophyll SPAD values,photosynthetic characteristics,chlorophyll fluorescence characteristics,yield,N accumulation,N fertilizer utilization of wheat and corn and soil fertility were investigated,as well as the physiological characteristics of corn at the seedling stage using fucoidan,the main acting substance of alginate,as an exogenous additive.These finding of study will provide a theoretical basis for the wide application of this new seaweed compound fertilizer in ecological agricultural production.The main research results are as follows:1.Compared with conventional fertilization,the application of algae compound fertilizer could increase wheat and corn yield,nitrogen accumulation and nitrogen fertilizer utilization rate.The grain yield of wheat treated with equal nutrient amount of seaweed compound fertilizer increased by 8.93%compared with conventional fertilization,and also showed significant yield increase at the level of 10%reduction,and 4.46%compared with conventional fertilization;The yield was maintained at the level of 20%reduction,and 30%reduction resulted in significant yield reduction;The number of ears,number of grains and thousand grain weight of equal nutrient amount of seaweed compound fertilizer T2 increased by 4.64%compared with conventional fertilization Compared with the conventional fertilizer T1,the number of spikes,grain size and thousand grain weight of T2 increased by 4.64*10~4 Spike hm^-2,1.27 and 3.20 g,respectively,which contributed more to the yield increase of wheat.The yield of corn treated with equal nutrient amount of seaweed compound fertilizer increased by11.98%compared with conventional fertilizer,and the yield increased by 5.94%compared with conventional fertilization at 10%reduction level.;At the level of 20%reduction,the yield could be maintained at the same level,and at the level of 30%reduction,the yield was significantly reduced,and the equal nutrient amount of seaweed compound fertilizer T2 increased the number of rows of ears,the number of grains in rows and the weight of 100 grains compared with conventional fertilizer T1.The number of rows,number of grains in a row and weight of100 grains were increased by 0.46,3.56 and 5.15 g,respectively,compared with the conventional fertilizer T1,which contributed more to the yield increase of corn.In wheat and corn field trials,N accumulation was the highest in all the equal nutrient seaweed compound fertilizer treatments T2,and the apparent N fertilizer utilization increased by10.84%and 9.95%,respectively,compared with conventional fertilizer application T1 in wheat and corn trials,and increased the agronomic efficiency of N by 3.29 kg kg^-1,5.68 kg kg^-1.2.The application of equal nutrient doses of seaweed compound fertilizer increased the plant height,stem thickness,ear length,ear width,leaf area and leaf chlorophyll SPAD values as well as photosynthetic and chlorophyll fluorescence characteristics of wheat corn,and the overall trend of each index decreased with the reduction of nutrient doses,but the reduction of10%and 20%could still ensure the healthy growth and development of wheat corn.The application of seaweed compound fertilizer can reduce soil pH and improve urease activity,and the application of equal nutrient amount of seaweed compound fertilizer can improve soil nitrate nitrogen and ammonium nitrogen content,and the 10%and 20%reduction still have a good effect of inhibiting nitrification.3.Fucoidan solution at appropriate concentrations improved above-ground biomass and photosynthetic characteristics of corn at seedling stage,basically the best treatment was at 100mg L^-1,plant height and stalk thickness at 50 mg L^-1,and the highest leaf chlorophyll SPAD value at 150 mg L^-1,indicating that high concentration of fucoidan solution would have inhibitory effect.The effects of low and high concentrations of fucoidan solutions on corn tended to be similar.100 mg L^-1 fucoidan solution had the maximum root length,200 mg L^-1fucoidan solution had the smallest average root diameter,50 mg L^-1 had the maximum root surface area and root volume,and 50-150 mg L^-1 had the maximum range of root vigor.Therefore,fucoidan has a dual regulating effect on the root vigor of corn,promoting growth at100 mg L^-1.In summary,according to the role of seaweed compound fertilizer in nitrogen uptake,yield increase and biological characteristics as well as soil fertility,the application of seaweed compound fertilizer at 80%to 100%of the nutrient dosage of conventional fertilization in the wheat-corn rotation is more effective.