EVALUATION OF PRE-CROPS AND ORGANIC FERTILIZATION PROGRAM ON SOIL CHEMICAL PROPERTIES AND ON THE SUBSEQUENT CROP UNDER MEDITERRANEAN CONDITIONS: CASE OF SOUTH OF ITALY

Organic farming systems rely on soil fertility management to enhance the soil chemical properties for the optimization of crop production. Soil fertility-building crops have been reported as a way to reduce inputs, improve soil fertility and subsequent crop production and quality. The present study was conducted in southern Italy and consists in evaluating the effects of pre-crops (faba bean, vetch and broccoli) in comparison to a fallow test and of two different fertilization strategies (commercial organic fertilizer and compost tea) on the main soil chemical properties and on the subsequent crop (tomato and lettuce) in two consecutive years. A split-plot design was used with four replicates and two factors having the pre-crop as the main factor and fertilizers as sub-factor. Fallow plots accumulated up to 55-26 kg/ha of nitrogen, broccoli up to 24-26 kg/ha, faba bean up to 65-75 kg/ha and vetch up to 190-215 kg/ha, respectively, in two years. Results showed that vetch was able to satisfy the N requirement of the main crop without any fertilizer application. The main soil chemical parameters were improved over two years experiment. The trend was consistent; all studied parameters displayed a significant increase in all treatments, while no significant differences were obtained between treatments. In the first year, the effect of different pre-crops and fertilizers on tomato yield and quality parameters was insignificant. While the results obtained in the second year showed that pre-crops and fertilizers had significant effects on lettuce yield and quality. Yield of lettuce obtained after pre-crops was higher compared to fallow treatment: vetch (27%), broccoli (23%) and faba bean (18%). Different nitrate contents compared to fallow (80% lower) and the ascorbic acid contents (16% higher) were obtained after broccoli treatments. On the other hand, there was no significant effect of fertilizers used in this experiment on lettuce production. These suggest that the pre-crops, especially vetch, can improve main crop yields; while compost improves the quality parameters.