Effects of organic and mineral fertilizers on yield and nutritional status of lettuce

The effects of different organic and mineral fertilizers were investigated on yield and nutritional status of lettuce. Yield of lettuce was measured and total nitrogen, phosphorus, potassium, calcium, magnesium, iron, zinc, manganese and copper were analyzed to determine the effects of different fertilizers [liquid poultry manure (LPM), solid poultry manure (SPM), blood meal (BM) and mineral fertilization (MF)] in two different periods. Yields were increased by fertilizer applications in the rate of 17.0 and 221.2% when compared with the control values in two different periods. While the highest yield in autumn experiment was determined at LPM 300 kg da(-1) -/+ SPM 300 kg da(-1), the highest yield in spring experiment was determined at mineral fertilization. While the most effective fertilizers on yield were the ones with high phosphorus content in autumn experiment, fertilizers with high in nitrogen content were the most effective in spring experiment, It was determined that seasonal effects (i.e. temperature) might be important on the selection of combinations and amounts of organic fertilizers. As far as the nutrient elements content of lettuce leaves is concerned: N, P, K, Ca and Mg contents of lettuce leaves were insufficient in both the spring and autumn experiments, but Fe, Mn, Zn and Cu contents of leaves were sufficient. These results indicated that the present fertilizer applications were insufficient for a higher productive lettuce growth. Particularly. in organic farming; it was seen that the combinations of different organic fertilizers were important for sufficient and balanced plant nutrition and that seasonal conditions might have considerable effects on the effectiveness of the fertilizers.