Effects Of Chemical Fertilizer Reduction Combined With Organic Fertilizer On Soil Fertility In Rice-wheat Rotation

In this study,the rice-wheat cropping area in Chengdu Plain was taken as the research object.According to the zero growth requirement of chemical fertilizer,the field fertility,organic carbon and total nitrogen were studied by field experiment and mathematical statistics method.The change of reserves is used to explore the optimal dosage of fertilizers combined with organic fertilizers,in order to provide a scientific theoretical basis for the formation and technical promotion of the fertilizer-fertilizer combined with organic fertilizer technology system in rice-wheat rotation area.There are six treatments in this experiment,including blank non-fertilization（CK）,local conventional fertilization（T1）,80%conventional fertilization（T2）,80%conventional fertilization+commercial organic fertilizer 1500 kg·hm^-2（T3）,80%conventional fertilization+commercial organic fertilizer 3000 kg·hm^-2（T4）,80%conventional fertilization+commercial organic fertilizer 4500 kg·hm^-2（T5）.Soil samples from plough layer（0-20 cm）were collected at the maturity stage of rice and wheat,and the changes of soil basic physical and chemical properties,nutrient content,soil organic carbon storage and total nitrogen storage under six treatments in two years were studied.The actual wheat yield was measured and the following conclusions were drawn:（1）Effects of different fertilization reserves on crop yieldFertilizer reduction and application of a certain amount of organic fertilizer will not reduce the yield of rice and wheat.80%chemical fertilizer combined with3000-4500 kg·hm^-2 organic fertilizer can ensure stable yield of rice and wheat.The results of two consecutive years of experiments showed that in the rice season,80%of the chemical fertilizers combined with organic fertilizer 3000-4500kg·hm^-2 could increase the yield of rice by 2.81%-9.62%compared with 80%conventional fertilization（T2）.In the wheat season,80%of the fertilizer was applied with 4,500kg·hm^-2 of organic fertilizer,and the yield of wheat was increased by 7.65%-8.07%compared with T2 treatment.（2）Changes in basic soil properties under different fertilization treatmentsThe effect of chemical fertilizer reduction combined with organic fertilizer on soil pH,soil density and cation exchange capacity showed a general trend.The soil density of the treated organic fertilizer was lower than that of the blank treatment,and the cation exchange amount increased compared with the blank treatment,while the soil pH increased with the increase of the organic fertilizer dosage.（3）Changes in soil nutrients under different fertilization treatmentsFertilizer combined with organic fertilizer could increase soil organic matter,total nitrogen and available phosphorus in rice and wheat,and the organic matter and total nitrogen content of rice and wheat increased with the increase of organic fertilizer application.In the rice season,soil organic matter,total nitrogen and available phosphorus increased by 3.04%-9.50%,6.25%-22.80%,25.24%-58.64%,respectively,compared with blank treatment.The wheat season increased by9.68%-15.74%,18.03%-29.71%,and 37.39%-52.38%,respectively,compared with blank treatment.When the rice season was applied with organic fertilizer3000-4500kg·hm^-2,the soil available potassium content was higher than the blank,but it was lower than 80%fertilizer application 0.88%-5.10%.In the wheat season,the content of available potassium in soil treated with organic fertilizer was higher than that of blank and 80%fertilizer treatment,but there was no law of reproduction.（4）Changes in soil carbon and nitrogen storage under different fertilization treatmentsFertilizer combined with a certain amount of organic fertilizer could increase soil carbon and nitrogen storage which effect was better than fertilizer.80%of the chemical fertilizers combined with organic fertilizer 3000-4500kg·hm^-2 could increase soil carbon storage of rice and wheat by 1.07%-5.91%,10.76%-12.80%,respectively,compared with blank treatment,increase soil carbon of rice and wheat by0.73%-5.59%,2.21%-5.60%,respectively,compared with 80%conventional fertilization;and which could increase soil nitrogen storage of rice and wheat by14.0%-19.2%,16.24%-26.34%,respectively,compared with blank treatment,increase soil nitrogen storage of rice and wheat by2.30%-10.78%,0-11.52%,respectively,compared with 80%conventional fertilization.（5）Screening of fertilizers combined with organic fertilizersUnder our test conditions,compared with no fertilization（CK）and 80%conventional fertilization（T2）treatment,80%conventional fertilization+commercial organic fertilizer 3000kg·hm^-2（T4）and 80%conventional fertilization+commercial organic Fertilization 4500 kg·hm^-2（T5）treatment has significant effects on soil basic properties,nutrient content,soil organic carbon storage,total nitrogen storage and crop yield.