Experimental study on the impacts of rainfall intensity on phosphorus loss from loessial slope land

Phosphorus (P) loss from slope land is an important factor for soil degradation and water environmental worsening. It is very significant to study the mechanisms of rainfall characteristics affecting soil P loss for slope nutrients management and environmental protection. Impacts of rainfall intensities on P loss from loessial slope land were studied using loessial soil with texture of silty loam and through simulated laboratory rainfall experiments. Results show that Dissolved P(DP) contents in the slope runoff are above 0.18 mg/L. DP contents in runoff significantly decrease with increase of rainfall intensity at the same rainfall amount. The contents and loss amounts of Sediment Extractable P(SEP) and Sediment Total P(STP) are all the greatest under the smallest rainfall intensity 0.91 mm/min. Changes in DP, SEP, and STP contents all show a similar "low-high-low" tendency and are positively related to sediment concentration during runoff process, while the accumulative amounts increase with accelerative rates. Contents for different P forms in the runoff from loessial slope land decreases with increase of rainfall intensities. However, the loss amounts for different P forms are affected by multiple factors including rainfall intensity and runoff process.