Effects Of Continuous Replacement Of Organic Materials On Rice-wheat Nutrient Uptake And Loss Of Nitrogen And Phosphorus From Farmland

With the rapid development of agriculture and rural economy,the input of chemical fertilizers is an important way to pursue high grain yields,but the problem of agriculturalnon-point source pollution caused by the application of a large number of chemical fertilizers has also posed a threat to human beings,how to reduce agricultural non-point source pollution under the premise of ensuring crop yield has become a long-term research problem ofscholars in the industry,and pig manure,straw organic fertilizer has an important role inimproving soil traits,cultivating fertility,improving nutrient supply capacity,increasing crop yield,so organic fertilizer will replace chemical fertilizer,and combination of the two isconducive to fertilizing soil and crop yields,and can reduce the risk of non-point source pollution.From 2017 to 2021,this study carried out long-term positioning monitoring experiments for 4 consecutive years at the farmland demonstration base of Tangzui Village,Yanjiao Town,Chaohu City,Anhui Province,and set up a total of 8 fertilization treatments,namely:blank（CK）,conventional（CF）,100%,50%,30%organic material substitution（M1,M2,M3）,100%,50%,30%straw organic material substitution（F1,F2,F3）.The effects of organicmaterial substitution on nutrient uptake,yield,nitrogen and phosphorus loss in farmland and soil fertility after harvest were studied on rice and wheat after four consecutive years,and the results were as follows:（1）The wheat yield was the highest under the 30%pig manure organic materialreplacement treatment,which was 5662.01 kg?hm^-2,an increase of 3.73%compared with the conventional treatment,while the rice yield was the highest under the conventional treatment,which was 11650 kg?hm^-2,and with the increase of the organic material replacement ratio,the rice and wheat yields showed a downward trend,and the 100%organic material replacement treatment significantly decreased the rice and wheat yields compared with other fertilization treatments.（2）Under the 30%organic material replacement treatment of pig manure,the absorption effect of nitrogen and phosphorus nutrients in wheat was highest,while the absorption effect of rice nitrogen and phosphorus nutrients was the best under the conventional treatment,and the absorption effect of rice and wheat nitrogen and phosphorus nutrients under the 100%organic material replacement treatment was the same.significantly lower than other fertilization treatments.（3）The net photosynthetic rate of rice at heading stage was the highest under the 30%straw organic material replacement treatment,which was 33.99 umol CO₂·m^-2·S^-1,which was3.66%higher than that of the conventional treatment,while the rice under the 100%organic material replacement treatment was the highest.The net photosynthetic rate at heading stage was significantly lower than that of conventional treatment.In addition,the net photosynthetic rate at heading stage of rice was significantly higher than that at tillering stage.（4）Organic material replacement helps to improve the nitrogen and phosphorus nutrient absorption of rice in different growth periods.Among them,the nitrogen nutrient absorption of rice in different growth stages was higher under the 30%pig manure organic materialreplacement treatment,but different under the 100%Organic material replacement treatment.During the growth period,the phosphorus absorption of rice was relatively high.（5）The total nitrogen loss in wheat fields under each treatment was 21.90～33.66 kg?hm^-2.Compared with the conventional treatment,the total nitrogen loss in the organic materialreplacement treatment decreased by 8.44%～25.94%,and the TP loss in wheat fields undereach treatment Compared with the conventional treatment,the total phosphorus loss increased by 24.64%～44.93%under the 100%organic material replacement treatment.The loss of total nitrogen in paddy fields under each treatment was 7.07～23.03 kg?hm^-2.Compared with theconventional treatment,the loss of total nitrogen in the organic material replacementtreatment was reduced by 4.52%～26.23%,and the loss of TP in paddy fields under each treatment was 0.15～1.00 kg?hm^-2,compared with the conventional treatment,the total phosphorus loss increased by 188.46%～284.62%under the 100%organic materialreplacement treatment.（6）The total nitrogen concentration of the paddy field surface water under each treatment was 1.76～7.42 mg·L^-1.Compared with the conventional treatment,the totalnitrogen concentration of the paddy field surface water was reduced by 5.26%～21.56%under the organic material replacement.The phosphorus concentration ranged from 0.12 to 0.90mg·L^-1,among which the 100%organic material replacement treatment had the highest total phosphorus concentration,which increased by 42.86%and 41.27%,respectively,compared with the conventional treatment.（7）The organic material replacement treatment slowed down the soil acidification of rice-wheat farmland to a certain extent,and with the increase of the organic materialreplacement ratio,the soil nutrient content of rice-wheat showed an upward trend.