| China has fairly rich biomass resources. The annual production of crop straws, including corn straw (35%), wheat straw (21%), rice straw (19%), and the other (25%), exceeded 700 million tons. As an important source of organic fertilizer, straw is rich in nitrogen, phosphorous, trace minerals, as well as organic matters. However, a recent investigation revealed that less than 40% of straw were effectively utilized in China, largely due to technical and social-economical constraint. Every year, over 200 million tons of straw were simply burned or discarded, causing severe atmosphere and water pollution, wasting this valuable resource as well. Therefore, how to properly utilize straw is key to China's sustainable agriculture, and also a challenge for agriculture researchers.Simulated soil culture experiment and isothermal adsorption were conducted to investigate the activation of phosphorus (P) under the influence of straw amelioration materials, and its impact on providing P in soil. To improve phosphorus-holding capacity of soil, the best ratio and amount of various substances in the straw improved materials were obtained. This research provided scientific basis for improving P effectiveness and sandy soil by applying straw improved materials. The main conclusions of research are:1. The simulated soil culture experiment showed that the straw modified materials can not only increase the concentration of available phosphorus in sandy soil, but also improve its effectiveness, activating the phosphorus of sandy soil. Adding wheat straw improved material, the order of average phosphorus content was 90d (31.21mg·kg-1)>60d (30.51mg·kg-1)>30d (28.19mg·kg-1)>10d (20.44mg·kg-1); adding rape straw modified materials, the order of average phosphorus content was 90d (33.29mg·kg-1)> 60d (32.75mg·kg-1)> 30d (31.91mg·kg-1)> 10 d (27.76mg·kg-1).With the increase of improved materials, the content of available phosphorus in sandy soilgenerally increased. Compared with control, it did not reach significant difference when the treatment is 2g·kg-1], while 5g·kg-1 and 10g·kg-1 reached a significant difference. Different rate of PAM added in the straw modified materials had impact add to the content of available phosphorus in sandy soil, the more PAM, the more content of available phosphorus. At different culture time, the content of available phosphorus was lowest without adding PAM treatment in sandy soil added straw improved materials; for other treatment, the highest content of available phosphorus were T2,3, T5,3, T10,3. Correlation analysis showed that, the content of PAM and available phosphorus in sandy soil reached a significant positive correlation.Different culture time had different effect to the content of available phosphorus in sandy soil. With the increase of culture time, the control of available phosphorus content did not change. For other treatments, with the increase of culture time, the content of available phosphorus increased.Both of the two straw modified materials can increase the content of available phosphorus in sandy soil, and activate the available phosphorus, but the impact of rape straw modified material was more significant. From the total average, after the culture time 10 days,30 days,60 days and 90 days, the content of available phosphorus was higher in sandy soil with rape straw modified materials than that wheat, and the difference reached a significant level (p<0.05).2. Experiment of phosphorus isothermal adsorption-desorption of sandy soil was studied.The results indicated that indigenous phosphorus supplying capacity of sandy soil was improved after improved material of cole and wheat straw was applied.The total average phosphorus adsorption rate of sandy soil increased significantly while improved material was applied.Besides, phosphorus adsorption rate of sandy soil increased generally with the application of improved material. Phosphorus adsorption rate of the treatment 10g·kg-1 increased most.The content of PAM in improved material would affect the phosphorus adsorption rate. With the increase of the content of PAM in improved material,phosphorus adsorption rate of sandy soil increased.Compared with other treatment,the treatment without PAM had lowest phosphorus adsorption rate of sandy soil. The highest phosphorus adsorption rate were found in T2,3, T5,3, T10,3respectively. Meanwhile, application of meliorative material of cole and wheat straw could decrease total average phosphorus desorption rate of sandy soil and increase phosphorus desorption rate of sandy soil through the course of physical adsorption-desorption.Maximum absorption capacity of phosphorus of sandy soil decreased generally after meliorative material was applied. Maximum absorption capacity (Xm) of phosphorus of sandy soil varied by the capacity of meliorative material. Maximum absorption capacity (Xm) of phosphorus of sandy soil decreased with increasing the capacity of improved material. The content of PAM in meliorative material would affect maximum absorption capacity(Xm) of phosphorus. Maximum absorption capacity(Xm) of phosphorus of sandy soil decreased with increasing the content of PAM in meliorative material. Compared with other treatment, the treatment without PAM had lowest maximum absorption capacity(Xm) of phosphorus after 10,30,60 and 90 days' culture time. The highest maximum absorption capacity were found in T2,3, T5,3, T10,3respectively. Maximum absorption capacity (Xm) of phosphorus in control barely changed with time. Maximum absorption capacity of phosphorus of sandy soil decreased with culture time in the treatments which added improved material of cole straw. For the treatments which added improved material of wheat straw,maximum absorption capacity(Xm) changed adversely after 90 days. It was more than 60 days, but it was still less than control and 30 days. Thereby, indigenous phosphorus supplying capacity could be improved for the decrease of maximum absorption capacity(Xm) of phosphorus of sandy soil.The application of straw improved material could increase the adsorption equilibrium constant(K) and maximum buffer capacity(MBC) of phosphorus, however, varied with the capacity of improved material. Adsorption equilibrium constant(K) and maximum buffer capacity(MBC) increased with the capacity of improved material. Besides, Adsorption equilibrium constant(K) of phosphorus and maximum buffer capacity(MBC) of phosphorus increased with the content of PAM in improved material.The treatment without PAM had lowest adsorption equilibrium constant(K) and maximum buffer capacity(MBC)of phosphorus after 10,30,60 and 90 days'culture time. The highest adsorption equilibrium constant(K) and maximum buffer capacity(MBC)of phosphorus were found in T2,3, T5,3, T10,3respectively. |
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