Leaching of potassium,magnesium, manganese and iron in relation to porosity of tilled and orchard loamy soil

Abstract

The aim of this study was to examine the leaching of potassium, magnesium, manganese and iron in tilled and orchard silty loam soil. The experimental treatments were: conventionally tilled field (CT) with main tillage operations including pre-plough (10 cm)+harrowing followed by mouldboard ploughing to 20 cm depth, and a 35-year-old apple orchard (OR) with a permanent sward. Leaching of the cations was determined in soil columns of undisturbed structure, 21.5 cm diameter and 20 cm height, from a depth of 0–20 cm. All the columns were subjected to spray irrigation at a level of 1110 ml (30 mm), and leachate in 50-ml increments was collected. Concentration of the cations in the leachate was determined using a spectrophotometer ICP-AS. Pore size distribution data showed that the volume of pores >20 µm under CT was greater at a depth of 0–10 cm and lower in the 10–20 cm soil layer under OR, and the reverse was true with respect to pores <6 µm. At each 50-ml leachate, concentration of all the cations was greater under CT than OR. In most leachates the differences were more pronounced for potassium and magnesium than iron and manganese. Percolation of the leachate was considerably faster in orchard than tilled soil.