Research On The Activation Of Insoluble Phosphorus In Soil Of Alfalfa Root Exudates

Select six varieties of alfalfa: knight 2, adidas, TG3, knight T, zhong mu no.1 and the target. Using the method of nutrient solution culture in artificial climate chamber.The mobilization of insoluble P in soils and the effect of phosphorus availability with the root exudates of alfalfa growth 60 d, 90 d, 120 d under the phosphorus(P) deficiency conditions and for phosphorus conditions was studied systematically.Test results show that:Compared with the control, under the P deficiency conditions, after the soil treated with six varieties alfalfa root exudates, the effectiveness of P was improved.The activation of Ca2-P was the most significant, Al-P, Fe-P and Ca8-P all have diffent levels of activation, O-P and Ca10-P have no significant effect. For P conditions have the similar results, but the effect is less than P deficiency treatment. Both under the P deficiency conditions and for P conditions, Olsen-P with Ca2-P has a significant or very significant negative correlation, with Al-P have a significant negative correlation, with O-P and Ca10-P has no correlation. under P deficiency also negatively correlated significantly with Ca8-P, with Fe-P has a no significant negative correlation. So Ca2-P is the main source of Olsen-P under deficiency stress, Al-P and Ca8-P can be also offered the Olsen-P, the effective less than Ca2-P, the effective of Fe-P less than Al-P and Ca8-P.Compared with the control, after the soil treated with six varieties alfalfa root exudates cultured under P deficiency conditions in 60 d, the Olsen-P content and insoluble P in soils have different changes. Olsen-P of TG3 treatment on soil increase(11.98%) was the most significant, followed by knight T of 7.36%; the activated ability of Ca2-P, outstanding varieties is TG3 and knight T, decreased by 24.99%(P<0.01) and 24.90%(P<0.01), and activated ability of Ca8-P of adidas, zhong mu no.1and target less than TG3 and knight T. cultured in 90 d, the Olsen-P content of knight T were higher than other varieties except zhong mu no.1 and target. the activated ability of Ca2-P outstanding varieties were knight T, zhong mu no.1 and target, Their’s Ca2-P content significantly lower than the control(P<0.01), and significantly lower than(P<0.05) other variety trentments; the performance of TG3, knights and zhong mu no.1were better in the activation effect of Fe-P, but were not significant(P>0.05) with other variety treatments. In 120 d, the Olsen-P content of knight T, zhong mu no.1 and target were significantly higher than control and other variety treatments(P<0.01); All varieties treatments’ s activated ability of Ca2-P was outstanding,all significantly lower than the control(P<0.01); About the activated ability of Ca8-P, knight T has better performance, but were not significant(P>0.05) with other variety treatments; target’s activated ability of Al-P has better performance, significantly decreased 28.49 % than control(P<0.01).Under for P conditions, In 60 d, the Olsen-P content of TG3 treatment significantly higher than knight 2, adidas and knight T; TG3 has the best activation of Ca2-P; the Al-P, Fe-P and Ca8-P content of six varieties have no significant difference(P>0.05). In 90 d, the content of knight T and zhong mu no.1were higher than(P<0.05)knight 2 and adidas; the activated ability of Ca2-P, knight T、zhong mu no.1 and target were better than other varieties, but all varieties have no significant difference(P>0.05); the Al-P, Fe-P and Ca8-P content of six varieties have no significant difference(P>0.05). In 120 d, the Olsen-P content of knight T and zhong mu no.1 significant higher than other varieties except target; the Ca2-P content of knight T significantly lower(P<0.01) knight 2, adidas and TG3; Target treatment’s activation effect of Al-P was significantly(P<0.05) higher than other there varieties except TG3 and zhong mu no.1.The effect of Olsen-P content on soil of same alfalfa varieties root exudates of different cultured time was different, the performance of 120 d>90 d>60 d; The tend with increase of growth days, Olsen-P content on soil was to be improved was showed. The content of Ca2–P was 120 d<90 d<60 d, Cultured in P deficiency conditions in 120 d, compared with the 60 d, the content of Ca2-P decline sharply, decreased by 76.34%, 74.95%, 74.92%, 87.06%, 88.67% and 86.00%(P<0.01); the contents trends of Al-P, Fe-P and Ca8-P was 120 d<90 d<60 d; O-P and Ca10-P showed no significant regularity. Cultured in 120 d under P deficiency conditions, the activation of alfalfa root exudates on Al-P, Fe-P, Ca2-P and Ca8-P were higher than 60 d and 90 d. It showed that with the increase of growing days, the activation of root exudates was more significant.The alfalfa root exudates in the supply of P and P deficiency conditions both have activation of Ca2-P, Ca8-P, Al-P and Fe-P on soil, the activation effect under P deficiency was higher than for P treatment. In the six varieties, compared to other five species, Knight T improved the Olsen-P content and the activation of soil insoluble P was most significant. With the plant growth days increased, the Olsen-P activation of root exudates on soil increased, the activating effect was 120 d>90 d>60 d.