Effects of agricultural wastes on the hydraulic properties of a loamy sand cropland in Turkey

Abstract

This study was carried out to determine the proper amount of application for manure (M), hazelnut husk (Corylus avellane L.) (HH), tobacco (Nicotiana tabacum L.) (TO) and tea (Camellia Sinensis (L.)) (TE) wastes based on hydraulic property improvement of a loamy sand cropland in Turkey. The effects of agricultural wastes on field capacity (FC), permanent wilting point (PWP), available water content (AWC), relative saturation (RS) and initial infiltration rate (IR) were determined for a loamy sand soil 7 months after agricultural wastes were incorporated to 15cm soil depth at four different rates (0, 2%, 4% and 6%, weight:weight) in a randomized plot design experiment with three replicates. While increases in soil OM content for the M application rates were generally lower, TE and HH treatments including high organic carbon (OC) contents resulted in high soil organic matter (OM) increases. Organic wastes generally increased the values of soil hydraulic properties, with increased aggregate stability (AS) and total porosity (F) and reduced bulk density (BD). The highest AS and F values were obtained with 6% HH and 6% TE applications, respectively. Due to different mineralization rates of the organic wastes attributable to their carbon: nitrogen (C:N) ratios, the same application rate had different effects on the soil's hydraulic properties. Manure, having the lowest C:N ratio, generally had a lower effect on AS and BD. Increased IR due to increases in AS and F by the agricultural waste treatment, especially at 4 and 6% HH, reduced the AW content to 15cm compared with 2% HH. This indicates that the significant application of higher C:N ratio wastes is not suitable in terms of AW, due to significant improvement of IR. While the highest FC (17.3%) and AWC (10.7%) values were found in the 6% TE application, the highest PWP (7.2%) and IR (333.4cmh(-1)) were in the 6% TO and 6% HH applications, respectively. To improve soil physical and hydraulic properties, 6% TO and M, 4% TE and 2% HH applications are suggested for loamy sand cropland.