Effects Of Biochar On Soil P Content And P Use Efficiency In Drip Irrigation Cotton Field

[Object] Three types of biochar were prepared in the high temperature(750 o C) and anaerobic conditions and produced by cotton straw, corncob, and chicken manure, respectively. The biochar of cotton straw was modified with HCl and Fe2(SO4), respectively. The objective of this study was to determine the characteristics of biochar that made by different materials and modified by different methods, and to evaluate the effect of different biochars application on P content of calcareous soil and P use efficiency of cotton plant.[Method] The experiment consisted of a pot experiment under greenhouse conditions and a field experiment. In the field experiment, four biochar treatments were set as: control(CK), cotton sraw biochar(SB), corncob biochar(CB), and chicken manure biochar(MB). Two P application levels were 0, 175 kg P2O5 hm-2(P0, P175). In greenhouse tests, There are four biochar treatments: control(CK1), unmodified biochar, HCl modified biochar, Fe2(SO4) 3 modified biochar. The P application rates were 0, 0.2 g P2O5 /kg(P1, P2).[The main results](1) The content of total P, available P and water-soluble P in soil were increased with biochar application, especially for water-soluble P. In the P0 plot, the water-soluble P content of soil were 23%,27%, and 23% higher in SB, CB, and MB treatments than that in CK, respectively. In the P175 plot, the water-soluble P content of soil were 50.5%, 48.2%, and 88.3% higher in SB, CB, and MB treatment than that in CK, respectively. The available P content of soil in CB and MB treatments were 31.9% and 35.2%greater than CK under P fertilized condition, and only MB treatment was 58.5% higher than CK under no P fertilized condition.(2) The MS treatment had the highest of dry matter weight and yield of cotton, and then were CB and SB treatments, CK was the least. Biochar application increased the P fertilizer use efficiency of cotton. The highest of P fertilizer use efficiency was found in MS treatment, and CB treatment significantly increased P uptake of cotton from soil.(3) When cotton straw biochar was modified with HCl and Fe2(SO4), the p H of biochar declined from10.4 to 7.0, and the surface pores and surface area increased, but the nutrient contents were significantly reduced.(4) The content of total P and water-soluble P in soil were improved by unmodified and modified biochars application. HCl modified biochar significantly increased dry matter weight and P uptake of cotton under both P1 and P2 levels, but unmodified biochar only improved the cotton dry weight and P uptake under P1 level. P fertilizer use efficiency of cotton was enhanced by unmodified biochar and HCl modified application, but not by Fe2(SO4)3 modified biochar.[Conclusion] Three types of biochar increased soil total P, available P and water-soluble P contents.Chicken manure biochar had the highest of P fertilizer use efficiency, and corncob biochar significantlyincreased P uptake of cotton from soil. Cotton straw biochar modified by HCl could reduce soil p H, and promote cotton growth and P uptake.