生物碳对土壤磷素和棉花养分吸收的影响

通过两年温室盆栽试验，研究了不同磷肥用量下生物碳对土壤磷素含量、 棉花生长和养分吸收的影响。试验以棉花秸秆为原料制备生物碳，制成三种热解温度（450℃、 600℃和750℃）的生物碳，分别以BC450、 BC600和BC750表示，同时以空白土壤为对照（CK）; 磷肥（P2O5）用量设3个水平0、 0.25、 0.5 g/kg（分别以P0、 P1、 P2表示）。研究结果表明，施用生物碳可显著提高土壤磷素含量及其有效性，随着生物碳热解温度的升高，土壤水溶性磷、 速效磷及全磷含量均显著增加，且对三种磷素含量的影响表现为水溶性磷 全磷 速效磷。施用生物碳处理两年棉花的干物质重均显著高于对照，但不同热解生物碳处理对两年棉花干物质重的影响各异。施用生物碳可显著增加棉花养分吸收量，总体表现为750℃ 600℃ 450℃。因此，施用生物碳可显著提高土壤磷素含量，促进棉花生长和养分吸收; 热解温度是影响生物碳质量的重要因素，生物碳的热解温度越高（450~750℃），其促进作用越好。

Effects of biochar on soil phosphorus content and cotton nutrient uptake

Influence of biochar on soil phosphorus (P),  cotton growth and nutrient uptake under different phosphorus fertilizer application rates was evaluated with a pot experiment in years of 2011 and 2012. Biochar was produced from dried cotton stalks via pyrolysis in oxygen-limited conditions. Three types of biochar produced at 450℃,  600℃ and 750℃ (BC450,  BC600 and BC750) were used as the soil organic amendment,  and an untreated soil was set as control (CK) in this study. Each soil treatment was applied with three levels of P fertilizer (P₂O₅) as 0,  0.25 and 0.5 g/kg of soil weight (P0,  P1 and P2). The experiment was that of 4×3 factorial design with four biochar treatments (BC450,  BC600,  BC750 and CK) and three P application rates (P0,  P1 and P2). Cotton was planted for two consecutive growth seasons in 2011 and 2012. The results show that the soil P content and availability are significantly improved with biochar added. With the increase of pyrolysis temperature of biochar,  the contents of water-soluble P,  available P and total P in soil are increased significantly,  and the order of influence of biochar on soil P content is water-soluble P> total P> available P. The dry matter amounts of cotton are significantly higher under the biochar treatments than those under the control (CK) in both 2011 and 2012,  but there are differences among three biochar treatments between 2011 and 2012. The P uptake of cotton is also promoted with biochar added. The order of cotton nutrients uptake under three biochar treatments is BC750 > BC600 > BC450 These results suggest that biochar can increase soil P content,  and enhance cotton growth and nutrients uptake. Thus,  pyrolysis temperature is a vital factor for biochar,  and the high temperature (750℃) biochar treatment demonstrates higher soil P,  cotton dry matter weight and P uptake compared to the low temperature (450℃) biochar.