The Decomposition Process Of Crop Straw And It’s Effects On Soil Organic Carbon And Nutrient

Most researches on straw amendments are major in the way that straw return to the filed, the varieties of soil moisture, addition straw together with the fertilizer and other external conditions. While the influence of adding different amounts of straw to soil is still rare. So this research is pivoted on the influence of different straw varieties and amounts to see the fluctuation of soil microbial biomass carbon, nitrogen, dissolved organic carbon, organic carbon, total nitrogen and mineral nitrogen etc under the condition of indoors simulation of outdoors condition, which controls the influences of other outdoors factors. At the same time research on the changes of chemical of the straw itself in the process of 150 days, the result indicates as follows:1. It produces some soluble organic matters after putting some organic materials into the soil. The amount of straw addition have an obvious effects on the soil dissolved organic carbon and nitrogen. With the increase of the straw amount the dissolved organic carbon and nitrogen in the soil is increased. The dissolved organic carbon and nitrogen in the experimental soil fluctuated with the cultivation time. Straw addition also has certain influence to the soil mineral nitrogen, the nitrate nitrogen in the soil is approximately to zero after a while, in the late period when tested the applied straw treatment it was found that there was some traces of nitrate nitrogen, the ammonium nitrogen in the soil have a significant changes in the process of early middle and late period of the experiment. It was also found that different species and content of straw have no significant effect on the ammonium nitrogen. Returned straw is one of the important sources of soil dissolved organic carbon and nitrogen. So straw returned to the soil could increase the soil dissolved organic carbon and nitrogen, it also offer effective resource of carbon and nitrogen to the soil microorganism.2. The properties C/N of straw itself got a better influence than the soil DOC and DON. C/N:corn leaves<wheat straw< corn straw. The DOC and DON is almost matched in the process of cultivation during the same period under the same amount of straw. The experiment shows that corn leaves treatments>wheat treatments> corn stalk treatments. The straw of the same properties have no significant effect on the soil DOC and DON.For example Yi, Y2, Y3, Y4 with the same amount of straw in the same period of cultivation got a similar changing process in 150 days.3. The use of straw can obviously increase the content of soil microbial biomass carbon and nitrogen. Due to the different C/N in the straw, the amount of soil microbial biomass carbon and nitrogen of corn leaves treatments is the highest, corn stalk treatment is the lowest. It means that the smaller C/N in the straw is the larger content of soil microbial biomass carbon and nitrogen will be. When the addition amount of straw confined to 2% to 6% the content of soil microbial biomass nitrogen stays the stable. There is an obvious distinction of the content of microbial biomass carbon and nitrogen when different straw species were added. So it is necessary to take the property of different C/N into account when straw returns. Only by that could the balance of nitrogen and carbon in the soil be coordinated. And only in that way could microbial biomass factors perform its utmost functions to recover the soil fertilizer.4. The addition of straw could accumulate the soil organic carbon, total nitrogen and potassium. And at the same time it increases with the addition amount of straw. The smallest content of soil organic carbon is corn leaves treatments, the second smallest is corn stalk treatment, the largest one is wheat treatment. On the content of total nitrogen, it was found that the corn stalk treatment was smallest one in the soil, the second smallest was wheat straw treatments, the largest content of nitrogen was corn leaves treatment, which is relevant with the chemical property of the different straw. The content of P in the addition straw treatment decreased and it shows that more addition of straw amount is the more P would decrease.5. Different kind of straw, even the same kind under the different condition of cultivation, the component of the straw behaves totally different. But the nutrient of the same kind straw shows dynamically the same trend in the entire process of the decomposition. Besides the amount of nutrient in the same kind of straw approximately equal in the same period. The content of total N and P ascend with time goes on in 150 days of cultivation. While the content of soil organic carbon and P decreased gradually. After 150 days of observation it is found that the content of N and P stays the order which is as following:corn leaves>wheat straw>corn stalk. On the released amount of potassium the first one is corn stalk, second is wheat straw, the third is corn leaves. The content of organic carbon of com leaves has always lower than corn stalk and wheat straw in the entire cultivation period. The content of organic carbon in the wheat straw has always been approximately equal to corn stalk. The same species of straw treatments have the same changing trend. The content of organic carbon of the plant shows minor differences in the same experimental period. Corn leaves still released the largest amount of carbon. But the amount of carbon released by corn stalk almost or a little bit larger than wheat straw did.