Wheat cultivation effect on inorganic P forms in loess-derived soils of Golestan province

Knowledge of the phosphorus (P) forms is essential for understanding the behavior of phosphorus. The aim of this study was to investigate the effect of wheat cultivation on different inorganic P forms of soil. A greenhouse factorial experiment in a completely randomized design was carried out with three replications in 20 soil types and plantation at two levels (with and without plantation). The aerial parts were harvested after two months and different forms of phosphorus were determined by Jiang and Gu's inorganic-P fractionation method. The results showed that wheat cultivation had a significant effect on all forms of phosphorus in soil except occluded P in Fe oxides. Duncan's means comparisons test at P. value ≤ 0.05 also showed that the amount of phosphate dicalcium (Ca2-P) in all of calcareous loess derived soils after wheat cultivation was less than uncultivated soils and it was significant in 30% of soils at P. value ≤ 5%. Similarly, wheat planting also reduced the amount of octacalcium phosphate (Ca8-P) and aluminum phosphates (Al-P), but the reduction was significant only in three soil samples. Decrease of iron phosphates (Fe-P) and apatite (Ca10-P) after the wheat harvest was significant only in one of the soils studied.