Effects On Nitrogen Of Farmland Ecosystem And Nitrogen Runoff Loss Risk Evaluation Under Manure Application To Field

With the adjustment of agricultural industrial structure,livestock and poultry breeding industry develops rapidly which contributes to increasing agricultural benefits and peasants incomes.On the other hand, many problems come following with the breeding industry. There are more and more animal manure waste produced because of rapidly expanding of livestock production.Because of lack of environmental protection conception and valid waste disposal approaches of a great number of breeding farms in china, most of the animal waste discharged directly into environment without effective disposal and reuse, which result in tremendous environmental pollutions. Applying manure to field has a few positive functions. It could amend soil conditions, improve soil fertility, as well as increase crop yield and improve product quality by way of participating the matter cycling of the agro-ecosystem. As a traditional treatment in the coordination of cropping and breeding, manure application to field is suitable for the practical production in our country. Only base organic manure application to field has become more and more popular in Northeast and North China, and some peasants applly same in downstream regions of Yangtze River. Meanwhile, secondly pollution comes consequently, acting as a negative function. Because of limited uptake capacity of soil and crops in a certain region or a certain scale, surplus nutrient would lapsed followed by water or evaporated by gaseous from the excessive manures. Thus, how to apply manures to field scientifically is essential to maintain a high quality environment and insure a sustainable agricultural production.By means of applying different levels of cattle manure and pig manure to rice ryegrass rotation system for two and a half years(five seasons) under field experiments,and one and a half years (three seasons) under potted experiments, the paper studies the effects on yield or biomass of rice and ryegrass, nitrogen uptake by rice and ryegrass plants, nitrogen distribution in soil profile, nitrogen surplus and nitrogen loss of field systems caused by applying different types of manure to field, different levels of manure to field and manure to field continuous. It is aimed to determine the appropriate scope of manure applying to field, ensuring the maximum elimination on manures from breeding farms and gaining some agriculture benefits, while minimizing potential secondary pollution on the environment of manure application to field. It also provides a reference for large-scale breeding farms to return manure to field. According to the traits of the characteristics of water and nutrient management of rice cultivation in rice cropping regions, the paper also constructs a rainfall-runoff-nitrogen loss simulation model.We study the nitrogen runoff loss risk under different levels of manure application, compared the distinction of nitrogen runoff loss of paddy field between only base manure application to field and the conventional fertilizer application. The main conclusions are as follows:1、In a certain range of manure application to field, the biomass or yield of rice and ryegrass increases basically with the enhance of manure application level. Over this range, the increasing potential of yield will be much less, even would make crops suffered. As far as rice is concerned, it’s biomass or yield increase with the enhance of manure application level in addition to that of the highest level of pig manure (P5) in the first year of manure application to field. But the rice biomass or yield decline significantly to the low levels when manure application two or three years consecutively, the third year’s decline points even move to the P3 level. As far as ryegrass is concerned, though biomass increase with the enhance of manure application level in the first year of manure application to field, biomass under C5 treatment has been slightly lower than that of C4 treatment when manure application two years consecutively. According to the influence on crop yield or biomass by applying manure to field, the suitable pig manure applying amount in rice season of the first year in rice- ryegrass cropping system is between P3 and P4, P2 to P4 in the second year, P1 to P2 in the third year; the suitable cattle manure applying amount in rice season of the first year in rice- ryegrass cropping system is between C3 and C5, C2 to C5 in the second year, C2 to C4 in the third year. In terms of ryegrass, the appropriate amount of pig manure applying to field is between P4 to P5 both in the first year and second year, the appropriate amount of cattle manure applying to field is between C4 and C5, C4 in the second year.2、As far as rice is concerned, the nitrogen load absorbed by rice plants increases continuously with the promotion of manure application level in the first year in addition to that of the highest level of pig manure (P5), but the increasing degree becomes smaller gradually between adjacent treatments with the promotion of manure application level. The nitrogen load absorbed by rice plants had appeared the trend of rising first and falling later when manure application two or three years consecutively, the highest nitrogen load absorbed by rice plants of nitrogen obviously moved to the low level treatment, even moved to P2 treatment in the third yearl. Most of the rice seedlings were dead indeed under potted experiment in the second year. As far as ryegrass is concerned, the nitrogen load absorbed by ryegrass plants increases continuously with the promotion of manure application level in the first year, though that of C5 level is lower than that of C4 level in the second year. In spite of pig manure or cattle manure, nitrogen agronomy efficiency of field rice during three years, nitrogen recovery efficiency and soil dependence rate of rice-ryegrass rotation period in first or second year are all continuously decreased by the promotion of manure treatment level.3、With manure application to field continuous in the rice-ryegrass rotation system, they appeared that the total nitrogen content in the surface of different soil layer was highest, lower content in the deeper soil. The total nitrogen content descend quickly between surface and 20cm soil layer, slowly below 20cm soil layers after harvest every season in the three years. The soil total nitrogen in the same soil layer after harvest every season increased with the promotion of manure treatment level, deeper the soil, smaller the difference between different treatments. After rice harvest in first year, the soil total nitrogen content of 20-50cm soil layer basically keep in the same level under different treatment level, and that of ryegrass decreased to 30-50cm soil layer. After the ryegrass havest in second year, the nitrogen content decreased to 40-50cm, then there was no soil total nitrogen content keeping in the same level under different manure treatment after rice harvest in the third year. In spite of one or two years after manure application, the nitrogen content of the cultivated layer in the soil of rice-ryegrass rotation system were all higher than the soil background values. The nitrogen content and nitrogen surplus of cultivated layer continuously increased with the promotion of manure application level. The nitrogen content of cultivated layer after two years application was higher than that of one year, higher the manure application, larger the difference of the nitrogen content between one year later and two years later.4、In spite of pig manure treatment or cattle manure treatment, rice season or ryegrass season in the first year or second year, rice season in the third year, or rice-ryegrass rotation period of the first year or second year, nitrogen loss amount and rate of rice- ryegrass rotation system continuously increased with the promotion of manure applying level. Compared with that of rice season, ryegrass season, rotation period of rice- ryegrass rotation system in the first year, the nitrogen loss rate of rice- ryegrass rotation system in the second year were higher generally, which had little difference. According to agriculture benefits and the effects on environment by applying manure to field with various levels, the suitable pig manure applying amount in rice season of the first year of rice-ryegrass cropping system was about P3 (876kg/hm2), while the cattle manure was about C3 (876kg/hm2); the suitable pig manure applying amount in ryegrass season of the first year was between p4 (552kg/hm2) and P5 (1104kg/hm2), while the cattle manure was about C4 (808kg/hm2). The suitable pig manure applying amount in rice season of the second year of rice- ryegrass cropping system was about P2 (438kg/hm2), while the suitable cattle manure was between C2 (438kg/hm2) and C3 (876kg/hm2); the suitable pig manure applying amount in ryegrass season of the second year was about P4 (552kg/hm), while the suitable cattle manure was still about C4 (808kg/hm2). The suitable pig manure applying amount in rice season of the third year of rice-ryegrass cropping system was between P1 (219kg/hm2) and P2 (8438kg/hm2), while the suitable cattle manure applying amount was about C2 (438kg/hm2)5、In spite of applying fertilizer to field or applying only base cattle manure to field,or cattle manure of various levels, there were significant linear correlation between nitrogen runoff loss and rainfall during the rice growing season, though they sometimes displayed large deviation. Nitrogen runoff loss from paddy field under cattle manure application was much less than that of fertilizer application. Nitrogen runoff loss from paddy field under high level of cattle manure application was significant higher than that of middle level; middle level was significant higher than that of low level.