根系分隔方式对玉米/大豆根际土壤碳含量及磷有效性的影响

【目的】豆科与禾本科间作体系中对磷有效性的影响主要集中在根系分泌物的活化作用，由根际沉淀引起的土壤碳含量与磷酸酶活性变化及其对红壤磷有效性的影响机制尚不清楚。【方法】本研究以间作玉米大豆为研究对象，设置根系完全分隔、尼龙网分隔、不分隔3种方式，在0、21.83、43.67、65.50和87.34 P mg kg-1（分别记为P0、P1、P2、P3和P4）磷肥施用水平下进行盆栽试验，研究根系分隔方式对间作玉米大豆根际土壤微生物量碳（MBC）、溶解性有机碳（DOC）、根际土壤有机碳（ROC）、酸性磷酸酶活性（ACP）、碱性磷酸酶活性（ALP）、速效磷和Hedley磷组分的影响。【结果】相比完全分隔，根系不分隔可提高玉米和大豆根际土壤MBC含量，显著降低玉米根际土壤DOC含量，低磷水平（P0、P1）时显著提高大豆DOC含量，显著提高玉米（仅在低磷时）和大豆根际土壤ACP活性，低磷时显著提高大豆根际土壤ALP活性。除玉米活性磷组分外，根系分隔方式对间作玉米大豆根际土壤速效磷、磷组分有显著或极显著影响。根系不分隔较完全分隔可通过降低大豆根际活性无机磷（Pi）(P0除外)和中活性Pi从而提高玉米根...

Effects of Root Barriers on Carbon Content and Phosphorus Availability in Maize/soybean Rhizosphere

  Objective  The effects of rhizosphere precipitation on phosphorus (P) availability in the cereal-legume intercropping system mainly focus on the activation of root exudates. The effects of rhizosphere precipitation on P availability in red soil are not clear.   Methods  Maize and soybean intercropping was used as the research object. Three root barriers, namely, complete separation of the root system, separation of nylon net, and no separation of the root system, were used in pot experiments at 0, 21.83, 43.67, 65.50 and 87.34 P mg kg–1 (P0, P1, P2, P3 and P4) application levels. Maize and soybean intercropping with root barrier, nylon mesh barrier, and no barrier pot experiments were conducted. The experiment was carried out at the levels of microbial biomass carbon (MBC), dissolved organic carbon (DOC), rhizosphere soil organic carbon (ROC), acid phosphatase activity (ACP), alkaline phosphatase activity (ALP), available phosphorus and Hedley P fractions in intercropping maize and soybean rhizosphere soil.   Results  Compared with a root barrier, no barrier can improve soil MBC in maize and soybean rhizosphere, significantly reduced soil DOC in maize rhizosphere, increased DOC in soybean rhizosphere at low P levels (P0, P1), significantly improved ACP activities in maize (only in low P) and soybean rhizosphere soil, and significantly increased soil ALP activities in soybean rhizosphere at low P level. In addition to the labile P fraction of maize, the available P and P fraction in rhizosphere soil of intercropping maize and soybean were significantly affected by root barrier methods. The labile Pi in maize rhizosphere soil was increased through decreasing labile Pi (except P0) and moderate Pi in soybean rhizosphere. In general, root interaction decreased the labile Po and moderate Po in maize and soybean rhizosphere. Regression analysis showed that root biomass was significantly positively correlated with MBC content in maize rhizosphere and DOC content in soybean rhizosphere (P < 0.01). Redundancy analysis showed that MBC accounted for 74.4% of available P and P components in maize rhizosphere soil, and DOC accounted for 18.3% of available P components in soybean soil. Mantel test showed that the relationships of labile carbon (C) fraction and phosphatase activities were significantly correlated with root biomass and soil P fraction in maize rhizosphere were much more than soybean.   Conclusion  Root interaction can improve the P availability in red soil by changing labile C fraction (MBC and DOC) in rhizosphere soil, promoting the secretion of phosphatase by microorganisms, and improving the conversion of moderate P fractions (Pi and Po) to labile Pi. MBC and DOC are the most important factors affecting the rhizosphere P fraction of maize and soybean, respectively. Therefore, the mechanism in the influence of rhizosphere precipitation on the P availability in maize and soybean rhizosphere could be different.