The effect of Different Tillage Managements on Soil Organic Phosphorus Forms

Changes in management practices like different soil tillage and keeping crop residues can be alter phosphorus (P) dynamics and increased P bioavailability. Conservation agriculture (CA), which reduces soil disturbance and keeps crop residues on the soil surface, affects the cycle and stratification of soil P, resulting a high P concentration in the upper layers of the soil. The objective of this study was to determine the changes in organic P fractions in a soil under different tillage managements using a sequential extraction procedure. The experimental design was a completely randomized block design (CRBD) with 5 replications. Tillage treatments were: conventional tillage (CT), Raised Bed system (RB), Minimum Tillage (MT) and No-Tillage (NT) systems. Soil samples were taken from the 0–8 and 8-16 centimeters depths at all four tillage treatments. Organic P pools were fractionated at each depth using modified Bowman and Cole (1978) procedure. The results showed that the change in soil tillage from CT to CA (Raised Bed Tillage (RB), Minimum Tillage (MT) and No-Tillage (NT)) significantly increased the amount of all organic P forms (labile P, moderately labile P, and non-labile, residual P). Also, the P concentration of wheat grain in MT and NT showed increasement about 35% rather than the CT. In addition, the wheat grain yield was the highest in the MT and increased about 21% rather than to CT. The results of this research showed that low soil disturbance under NT has changed the concentration and distribution of P in the soil, leading to the establishment a P concentration gradient that decreases with soil depth. Conversely, under CT systems incorporation of plant residues within the soil plough layer increases the organic matter decomposition rate and reduces the storage of labile and moderately labile organic P fractions.