بررسي تاثير تراكم خاك بر حركت نيتروژن ، فسفر و پتاسيم در ستون خاك

The Effect of Soil Compaction on Movement of Nitrogen, Phosphorus and Potassium in Soil Columns

Soil compaction influences soil structure, permeability, porosity, pore size distribution, soil water retension. When a soil is compacted, large soil pores change to small pores, and therefore, matric potential and soil water holding capacity will increase. These changes can cause impediments in mass flow and diffusicn of nutrients in soil. The aim of this study was to investigate the movement and distribution of some macro nutrient in soil as affected by soil compaction. The soil was packed into PVC columns to a bulk density of 1.4 to 1.95 Mg ni-3. Three levels of N, P, K fertiliser (200, 130 and 220 mg/kg soil ) were applied. The soil columns were irrigated for 5 times and effluents were continuously collceted and analyzed for the 3 elements. At the end of the experiment all the soil columns were divided into 6 parts and analyzed for measuring soil physical and chemical properties as well as N,P,K. The results showed that the movement and leachate of N and K in the soil columns were reduced as the soil compaction increased. But P transport was in contrast. The reason for the movement of nitrogen in low level of compaction is the existance of macro pores for preferential flow and suitable condition for nitrification. The mechanisms of potassiun movement was the same as nitrogen. Phosphorus transport in high compacted soil can be related to increased ion concentration, high moisture and diffusion coefficent in the soil. The larger applications of fertiliser practiced on compacted soil to overcome crop yield losses increase the potential for nutrient losses.