Plant Mineral Nutrition and Growth in a Saline Mediterranean Soil Amended with Organic Wastes

Abstract

This work describes the effects of a poultry manure and a compost (prepared from olive mill and cotton wastes) on soil conditions and plant nutrient status and growth in a saline soil from Mediterranean Spain, having an electrical conductivity for a 1:5 aqueous extract of 1.51 dS m-1. Two Brassica spp. (B. carinata A. Br. and B. oleracea L.) were selected from a hydroponic screening with two salinity levels, in which the greater tolerance of B. oleracea seemed to be related to maintenance of shoot K+ and restriction of Na+ and Cl-, behavior shown also by B. carinata at the lower salinity level. Brassica carinata and B. oleracea were grown in the soil after incorporation of the organic materials. The amendments increased the cation exchange capacity of the soil and the concentrations of exchangeable K+ and Mg2+. A significant proportion of the K+ added by the amendments was retained in the exchange complex. The equilibrium between soluble and exchangeable K+ tended toward the exchangeable forms, whereas Na+ remained mainly in the soil solution. Addition of manure significantly increased shoot growth for both Brassica species, while compost markedly improved B. oleracea shoot growth. These effects may have been related to increased shoot tissue K+:Na+ ratios and total phosphorus (P) concentrations, reflecting the K+ and P contents of the amendments. When tomato (Lycopersicon esculentum Mill.) was grown in the amended soils used for B. oleracea, its growth was not significantly greater than in the control. Although the organic amendments raised the water-extractable boron (B) concentration of the soil, plant tissue B concentrations were unaffected, possibly due to the elevated concentration of soluble in the soil.