Effects Of Nitrogen Replacement Of Chemical Fertilizers By Organic Manure On Rice And Wheat Yield And Soil Fertility

In this study,we investigate the effect of different organic-inorganic substitution ratios on soil physical and chemical properties,rice and wheat yield,soil enzyme activities,and the stability of soil aggregate.Six treatments were conducted,including replace 0%(W100),10%(Y1W9),20%(Y2W8),30%(Y3W7),40%(Y4W6),and 50%(Y5W5).The results showed that:1.Compared with the single application of inorganic fertilizer nitrogen,the replacement of inorganic fertilizer with organic fertilizer increased the content of soil organic matter,total nitrogen,total phosphorus,available phosphorus and available potassium,and alleviate the degree of soil acidification.Among them,the treatment of 40%organic nitrogen instead of inorganic nitrogen resulted in the largest fertility improvement effect.Compared with the single application of inorganic fertilizer,nitrogen substitution such as organic fertilizer increased the total output of three-year crop rotation by about 0.8-2.7%,of which the 20%organic nitrogen substitution of inorganic nitrogen had the most obvious effect of increasing the yield of rice and wheat.2.The proportion of aggregates>0.25 mm under the combined application of chemical fertilizer and organic fertilizer is higher than that under the single application of inorganic fertilizer.Treatment of organic fertilizers and other nitrogen instead of inorganic fertilizers increased the mean weight diameter(MWD)and geometric mean diameter(GMD)of the aggregates.The organic carbon and total nitrogen in each treatment were mainly distributed in 0.25-2 mm and 0.053-0.25 mm agglomerates.The C/N of different particle size aggregates was ranked from high to low to<0.053 mm(11.7)>0.25-2 mm(11.4)>Greater than 2 mm(11.3)>0.053-0.25 mm(11.1).The MWD had a very significant correlation with GMD and R0.25(r=0.940**,r=0.903**).3.Under cultivation conditions of 25℃ and 3 5℃,the organic carbon mineralization rate of soil and agglomerates was as follows:the rate of CO2 production in the early stage of culture decreases rapidly and the rate of later stage slows down,and with the extension of the cultivation time,the rate of soil CO2 production basically stabilizes.During the same incubation period,the average daily CO2 mineralization rate and cumulative mineralization rate both increased with the increase of temperature.The cumulative amount of organic carbon mineralization showed that the initial amount of CO2 production was large,and the release rate gradually increased with the extension of the incubation time.It tends to be gentle and the higher the temperature,the more CO2 was released,and the more CO2 could be mineralized from the cultivated soil.4.The cumulative mineralization rate of organic carbon under each fertilization treatment under the culture condition at 35℃ was significantly higher than the cumulative mineralization rate under the culture condition at 25℃.Under the two culture temperatures,the organic carbon mineralization rate of the aggregates of each particle size decreased rapidly in the early stage of the culture,and gradually stabilized in the later stage.With the increase of incubation time,the cumulative amount of organic carbon mineralization of aggregates of each particle size gradually increased,the increase was rapid in the early stage,and the cumulative release intensity in the later stage gradually slowed down.With the decrease of the aggregate particle size,the cumulative organic carbon mineralization also shows a downward trend,and the higher the temperature,the higher the cumulative organic carbon mineralization of each particle size agglomerate.The potential mineralizable carbon(C0)of the soil under cultivation at 35℃ is significantly greater than the C0 at cultivation temperature at 25℃.5.With the increase in the proportion of organic-inorganic fertilizers,β-glucosidase showed a downward trend and then an upward trend,while soil β-cellobiosidase showed a downward trend,and the enzyme activity was lower than that of single application of inorganic fertilizer.Compared with single application of inorganic fertilizer,combined application of organic and inorganic fertilizer increased the activities of urease and sucrase.There was no significant difference in the effects of single application of inorganic fertilizers and combined application of organic and inorganic fertilizers on soil acid phosphatase activity.