Study On Effect Of Using Humic Acid To Phosphorus Availability Of Cotton Soil

By the field and the pot test, we studied the effect of using humic acid on phosphorus available, the inorganic phosphorus various components, soil pH, CaCO₃ content influence as well as various ingredients mutual influence in the typical gray desert cotton soil, and discussed the effective way of using humic acid activate soil phosphorus. The main results are as follows:1. The activation of humic acids to gray desert cotton soil fixed phosphorus was being connected with the quantity of humic acid and wasn't limited by soil fertility condition, as the quantity of humic acid used being increased, the degree of soil fixed phosphorus being activated increasingly. In the typical gray desert cotton soil, it was obvious that the available phosphorus content of soil increased in 0-20cm soil root level and near the cotton root level by using humic acid, and the soil available phosphorus content increased along with the humic acid quantity increased.2. In the typical gray desert cotton soil, humic acid accelerated several kinds of shape soil inorganic phosphorus change. The fixed phosphorus was activated by humic acid from other forms to available transform Ca2- P,Ca8- P, and was obviously in the cotton flower bell time. The soil fertility level has more influence to soil Ca2- P, Ca8- P, O- P, Ca10- P content, but was not remarkable to soil Al- P and the Fe- P influence; There were more influences on Ca2- P,Ca8- P of soil for using humic acid in the low fertility soil, simultaneously, it was remarkable for reducing O- P,Ca10- P. Under the identical fertility level, the quantity of humic acid became larger, increase the scope of Ca2- P, Ca8- P became larger, Fe- P became smaller, Al- P, O- P content increased or decreased, decrease the scope of Ca10- P content became larger.3. Humic acids have some reducing effect on cotton soil pH, and the reducing degree increased along with the quantity of humic acid used increased. The reducing effect of humic acid to the cotton soil pH 0-20cm soil layer was remarkable than 20-40cm soil layer, near the cotton plant root 5cm was remarkable than 15cm. The reducing effect of humic acid to the cotton soil pH, decreased along with the depth of soil increased, decreased along with distances from the cotton plant root increased. The soil fertility level have great effect on soil pH, soil pH was higher under the low fertility condition and lower under the high fertility condition; Under the same fertility level, the soil pH became smaller along with increasing quantity of humic acid, decreased the scope was small.4. Humic acids have some reducing effect on cotton soil CaCO₃ both vertical and horizontal direction. 0-20cm soil layer was remarkable in the vertical direction, and the place which near the cotton plant root was remarkable in the horizontal direction. It was shown that, the reducing effect of humic acid to the cotton soil CaCO₃, decreased along with the depth of soil increased, weaken along with distances from the cotton plant root increased. The soil fertility level have a little effect on soil CaCO₃; Under the same fertility level, the soil CaCO₃ became smaller along with increasing quantity of humic acid, decreased the scope was small.