Effects Of Different Organic Materials Input On Soil Organic Carbon And Nutrients In Lou Soil

There are many soil problems in Guanzhong plain, such as decline of soil fertility and productivity, poor soil structure, and the serious waste of straw resources. The study set rain-fed and irrigated two levels, 6 different processing respectively: control（CK）, nitrogen and phosphorus fertilizer（NP）, NP + organic fertilizer（MNP）, NP + straw（SNP）, NP + biochar（B1NP）, NP + 200% biochar（B2NP）, investigated the influence of different organic material input on soil carbon and nitrogen for the purposes fertilizer, and to provide scientific theory and practice basis on selection of a better way to improve soil fertilities. Based on Irrigation experimental station of Northwest A&F University, key lab of agricultural water-soil engineering of Ministry of Education in Yangling of Shaanxi province, the effect of different organic material input（organic fertilizer, straw and biochar） on soil organic carbon and nutrients of nitrogen, phosphorus and potasium were studied to explore the effect of different organic material input on soil carbon and nitrogen cycling by the field experiment on Lou soil under the rainfed and irrigated conditions during September 2013 to June 2015.The results are as follows:1. The effects of different organic material input on soil organic carbon content promotion are remarkable. After three cropping, soil organic carbon present the trend as 200% biochar>biochar>crop straw>organic fertilizer>nitrogen and phosphorus fertilizer>control both under the rainfed and irrigated conditions. Compared with the treatment of nitrogen and phosphorus fertilizer, soil organic carbon of 200% biochar treatment significantly was increased by an average of 35.5%, 77.1% and 44.6% after three cropping respectively; that of Biochar treatment was significantly increased by 20.1%, 39.4% and 21.1% respectively, that is the input of biochar could improve soil fertility sustainably. SOC of Straw return treatment was increased by an average of 18.9% significantly after a year’s decomposition, while organic fertilizer had no significant effect on SOC after the second winter wheat seasonthat the organic material input was stopped. Organic fertilizer has an effect on soil organic carbon promotion at the current crop season, but has weak effect after it was stopped. Different organic material input had smaller effects on increasing soil total nitrogen, which was increased at 0.09⁰.19 g/kg after three cropping. The trend is like organic carbon. It is more advantageous to improve the soil organic carbon and total nitrogen content undert irrigated condition, but the difference was not significant to compare with that under rainfed condition. Therefore, application of biochar can improve soil organic carbon and total nitrogen content continuously, which is remarkable on soil fertility improvement in Guanzhong Plain.2. Under different organic material input after 3 cropping, soil microbial biomass carbon and nitrogen, ratio of soil microbial biomass carbon and nitrogen, and qMB were elevated by crop season, thereby it raised the effective nutrient which can be absorbed quickly by crops. Under the rain-fed condition, soil microbial biomass carbon and nitrogen presented the trend as crop straw>organic fertilizer ≈biochar ≈200% biochar>nitrogen and phosphorus fertilizer>the control（P < 0.05）during all three cropping; under the condition of irrigation and the organic material input, soil microbial biomass were increased by crop season. As a result, organic material input could improve the soil microorganism quantity. The promotion effect of crop straw is the best, then the biochar and organic fertilizer.3. different organic material input could improve soil available potassiumgreatly, and soil available pa little. After three cropping, soil available K were showing the trend as 200% biochar>biochar>crop strow>organic fertilizer>nitrogen and phosphorus fertilizer>the control（P<0.05） both under rain-fed and irrigated conditions. Compared with nitrogen and phosphorus fertilizer, these organic materials treatments increased significantly by 79%, 43%, 31% and 43%. After three cropping, biochar and 200% biochar treatments could improve soil available P and available K content by a slowly ascending trend season by season under rain-fed condition; Crop strawreturn could increase the soil available P season by season significantly under irrigated condition. The effect of organic fertilizer and straw return on available P and K promotionis obvious in current crop season, while biochar and 200% biochar could increase soil available phosphorus and potassium steady when the organic materialinput was stopped. Elevated levels of irrigation on the promotion of soil available phosphorus and potassium is greater under irrigated condition than that under rainfed condition. Therefore, It was suggested to use biochar to improve soil available phosphorus and potassium.4. The organic fertilizer could improve crop nitrogen uptake rapidly and nitrogen utilization effeciency, but less soil fertility steadily. The contribution of crop straw, biochar and 200% biochar is bigger to increase crop nitrogen uptake and NUE of summer maize and the secondwinter wheat. The organic material input could increase NUE, nitrogen agronomic efficiency, and nitrogen partial productivity season by season. The NUE of winter wheat is greater than that of summer corn. Proper irrigation is beneficial to the nutrient release of organic materials, so as to improve crop nitrogen uptake and NUE. Therefore, applying biochar and straw return is useful to improve crop nitrogen uptake and fertilizer utilization effeciency.5. Soil NO₃^--N of organic materials treatment fell sharply at the top soil layer. There was a high accumulation peakat around 100 cm soil layer on soil profile, and then soil nitrate-N was downward slowly. Biochar and 200% biochar treatments can significantly reduce the amount of nitrate nitrogen content and accumulation amount on soil profile, thus to improve the fertilizer utilization effeciency and to decrease the leaching risk, while the organic fertilizer and strawreturn treatments could increase the amount of nitrate-N content and accumulation of soil profile significantly. biochar and 200% biochar have no significant differences on reducing quantity of soil NO₃^--N residues. So on Guanzhong plain, applying 4 t/ha biochar could not only improve the soil fertility effectively, but also reduce the loss of nitrogen leaching and improve NUE, which is a recommended way to improve soil fertility on Lou soil.