不同磷(P)水平对土壤中钼(Mo)有效性的影响

EFFECT OF P—LEVEL TO AVAILABILITY OF MOLYBDENUM IN SOIL

一、前言土壤中微量元素对植物的有效性,在很大程度上受肥料的影响。Pendias等早就指出,施用P肥可以提高酸性土壤中Mo的有效性,stont,P.R.等其他许多研究者,也证明磷酸盐能促进作物对土壤中原有Mo的吸收,但James,W.S.等则提出,消量P会降低草本植物对土壤中Mo的吸收。因此,P对土壤中Mo的有效性,似乎有促进和抑制的双重影响。利用这种双重影响,国外已有人从提高土壤中Mo的有效性,来探索一条缓解植物缺Mo,以及为解决Mo毒引起反刍动物缺Cu症而降低土壤过高有效Mo的新途径。而这一做法,对改变我省南方大约三分之一缺Mo土壤和淮北。

Red-yellow earth, yellow-brown soil, and Shajiang black soil from Anhui province were incubated at 28℃ for 15 and 30 days after treated with nine p levels. The available molybdenum (Tamm's solution extracted) of the three soil types were found obviously decreased on the 15th day. soil available Mo dropped down below the soil Mo-background of the first two soils as determined on the 15th day of incubation, yet, it went back rapidly and even surpassed the background as obtained on the 30th day. The up and down of soil available-Mo during incubation formed a peak and a bottom both at 30-70 pppm treatments, in Shajiang black soil, the decrease of available Mo was only found in high p-treatments.Experiment initially revealed that the variation of soil available Mo during incubation depended greatly upon soil type, time of incubation, and p level. some considerations were resulted from the study:1. For yellow-brown soil with soluble Mo less than 0.1 ppm, and pH lower than 6, the addition of proper amount of p may improve the situation of soil Mo-deficiency;2. For red-yellow earth with soil available Mo around 0.15 to 0.20 ppm, and pH lower than 5.5, application p combrined with Mo as basal manure or seed-dressing would be beneficial;3. For the shajiang black soil with higher pH and high amount of available Mo (More than 0.3 ppm averagely), only high addition of p showed, a reduce of soluble Mo as proved by the study, which might a way for avoiding possible Mo-toxicity of ruminants.