FERTILIZATION MANAGEMENT TO REDUCING NITRATE ACCUMULATION IN SOME LETTUCE VARIETIES (Lactuca sativa L.) GROWN IN SANDY CALCAREOUS SOILS

Abstract

The present investigation was conducted during the two seasons of 2005/2006 and 2006/2007 at the Desert experimental Farm of Assiut Agric. Res. Station to study the effect of five levels of N-fertilizer (0, 30, 60, 90 and 120 kg N/fed.) and three levels of composted waste farm (Control (zero), Compost (3 ton/fed.) and bio-compost (3 ton /fed. compost with Biogen). Tow varieties were used in this investigation (Latoga and Balady). These varieties were grown in sandy calcareous soil under drip irrigation system. The interaction between the two fertilizer sources was studied. The results indicated that there were significant differences among the five levels of N fertilizer in all studied characters. Increased for both mineral and organic fertilizer were obtained of both lettuce varieties on yield and its components. Meanwhile, application of composted waste farm at a rate of 3 ton/fed in combination with Biogen reduced the application of mineral N to 50% and reduced nitrate concentration in leaves of both lettuce varieties. Compost and bio-compost as organic and bio fertilizers play an important role in maintaining soil fertility with releasing nutrients in the soil. The most increase in soil N and P content was observed with compost and bio-compost application. The increase percentage in P content over the control was 10.12 and 38.38 in 2006 and 25.58 and 19.08 % in 2007, respectively.