Residual Effects of Different Organic and Inorganic Fertilizers on Spinach ( Spinacia Oleracea L.) Plant Grown on Clay and Sandy Soils

The present study aims to residual effects of composts (plant residues, animal residues and mixed) with and without inorganic fertilizers on spinach (spinicia oleracea L.) plants and soils. The obtained results showed that the finished compost of plant residues was high in germination index (GI) and low in C/N ratio compared with the other composts. The study demonstrated that the spinach yield with 50% N mineral + 50% N organic treatments were higher than the other treatments in the clay and sandy soils especially with the plant compost. The high nitrate accumulation of spinach plants was found in organic and inorganic combinations fertilizers compared with inorganic fertilizer, where as, the nitrate concentrations in the of spinach leaves was lower than the acceptable limit of WHO. The nitrogen and phosphorus remained in the study soils increased with the increase of organic nitrogen applied as well as soil organic C. The combinations of organic and inorganic fertilizers to soils had a greater effect on increasing yield and improvement of the soil fertility.