苜蓿根系分泌物对土壤中难溶性磷的影响

Effects of alfalfa root exudates on insoluble phosphorus in soil

选取中苜1号、标靶、TG3、骑士2、骑士T和阿迪娜6个苜蓿(Medicago sativa)品种,采用水培法分别在缺磷条件下和供磷条件下收集根系分泌物,研究其对土壤中难溶性磷的活化作用及磷素有效性的影响。结果表明,和未添加苜蓿根系分泌物的土壤相比,苜蓿根系分泌物处理后的土壤,有效磷(Olsen-P)含量提高,缺磷条件下Olsen-P含量高于供磷处理;磷酸二钙(Ca2-P)含量极显著降低(P<0.01);磷酸铝盐(Al-P)、磷酸铁盐(Fe-P)和磷酸八钙(Ca8-P)的含量显著降低(P<0.05);闭蓄态磷(O-P)和磷酸十钙(Ca10-P)含量则无显著变化(P>0.05),缺磷条件下苜蓿根系分泌物对土壤中难溶性磷的活化效果高于供磷条件下的。6个苜蓿品种中,加入TG3根系分泌物的土壤Ca2-P的降幅最大,磷的有效性最高,骑士T次之;骑士T的Ca8-P含量降幅最大。苜蓿根系分泌物对Al-P、Fe-P、Ca8-P、Ca2-P均具有活化作用,且对Ca2-P的活化作用最明显,Ca2-P是苜蓿缺磷胁迫下Olsen-P的主要来源。

The root exudates of 6 alfalfa cultivars including Zhongmu No. 1,Target,TG3,Knight 2,Knight T and Adina growing in hydroponics with phosphorus or without phosphorus were collected to investigate their activation of insoluble phosphorus and effects on P effectiveness in soils. Compared with the soils without root exudates,the contents of effective P（ Olsen-P） increased,the contents of Ca2-P extremely significantly decreased（ P〈0. 01）,the contents of Al-P、Fe-P and Ca8-P significantly decreased（ P〈0. 05） and the contents of O-P and Ca10-P did not change in soils treated with root exudates（ P〉0. 05）. The activation of insoluble phosphorus of root exudates from plants without P was better than that of root exudates from plants with P. The contents of Ca2-P had the largest decline in soil treated with TG3 root exudates with the highest P effectiveness. The contents of Ca8-P had the largest decline in soil treated with Knight T root exudates with the secondly P effectiveness. Alfalfa root exudates have activation on Al-P,Fe-P,Ca8-P,Ca2-P and especially for Ca2-P which was the largest source of Olsen-P under phosphorus deficiency condition.