Different fractions of phosphorous and potassium in soils as affected by successive fertilization

Changes of three different fractions of phosphorous (P) and potassium(K) in soil with 10 years successive fertilization were studied. The results showed that three years application of both NPK and NPK plus OM (organic manure) increased the total organic P (OP) and by 1.34 and 2.09 times in all three test soils. Of OP,the active OP content rose up to 2.71 and 3.45 times as in the original soils, moderately active OP to 1.42 and 1.58, highly active OP to 1.28 and 1.41 times, respectively. During the same period, the inorganic P (IP) increased by 1.4 and 1.47 times, respectively. Of IP, the Ca2-P rose up to 7.37 and 8.69, Ca8P to 1.99 and 2.15, Al-P to 3.67 and 4.06, Fe-P to 2.29 and 2.36, O-P to 1.21 and 1.4, Ca10P to 0.96 and 0.97 times, respectively. As for the total K in the test soils, both NPK and NPK plus OM fertilization practices changed K contents, which were 1.02 and 0.999 times that of the original soils. The fraction of soluble K rose to 7.88 and 12.17, non-specific adsorbed K to 1.82 and 2.31, rapidly available to 1.49 and 1.85, slowly available to 1.04 and 1.23, mineral K to 1.012 and 1.015 time, respectively. In contrast, each fraction of P and K declined in all non fertilized soils. X-ray diffraction diagrams indicated that K?containing minerals as mica had little changes when K applied. However, the total K in the clay fraction (2m) tended to decline without K application. It is assumed that part of the adsorbed K by crops probably come from mica and the like minerals.