Organic fertilization on soil water content, yield and quality of processing tomato

Soil water retention is improved by the application of organic matter (crop residues, compost, and manure). In the last years, the application of compost to the soil assumed increasing importance for enhancing the fertility of agricultural ecosystems, and representing nowadays a possible strategy for disposing organic wastes. In the present work, the influence of compost application (COMP) to the soil, used as fertilizer, compared to a conventional mineral (MIN) fertilizer on: 1) the soil moisture evolution, 2) the yield and 3) the quality of a tomato crop was evaluated. A randomized block design with four replications (each experimental unit represented by three double-rows of plants, length=10 m - i.e., 150 plants/plot), was used. On three different times during the growing season, soil water content (layer 0–40 cm) was measured at a distance of 0, 45 and 90 cm from the drippers and after 2 hours, 1, 3 and 8 days after the irrigation practice. At harvest, productive parameters and quality of the fruits were assessed. The COMP treatment increased soil water retention (+12%) at field capacity and, during the following 8 days, the loss of humidity occurred more slowly compared to MIN treatment. Soil moisture decreased exponentially by increasing the distance from the dripper; such tendency was faster in MIN than in COMP. Total dry mass yield was not influenced by the treatments (13.5 t·ha-1 on average), while greater values in plant fresh weight (+16.8 t ha-1), total fruit yield (+18.4 t·ha-1) and marketable yield (+13.4 t·ha-1) were assessed by employing COMP instead of MIN as fertilizer. Yield differences were due to a higher number of fruits (+17%) in the compost fertilized plants. No differences were found in all the qualitative characteristics (dry matter, °Brix and pH) of the fruits.