Olive-mill wastewater spreading in southern Italy: effects on a durum wheat crop

The results of an experiment on olive-mill wastewater (OMWW) distribution in durum wheat are reported. The OMWW was spread without pre-treatments, at the maximum amount allowed by law, on a durum wheat crop in a Mediterranean environment. The experiment was carried out on the same plots from 1999 to 2001 in Monopoli (southern Italy) with two treatments-(not treated) NT and (treated) T. In the treated plots, OMWW obtained from a traditional press system was spread, during the crop vegetative phase, at 50 m(3) ha(-1). Soil and OMWW were characterised from both physical and chemical aspects. An automatic meteorological station recorded main climatic variables during the period from January to May each year. During the growth cycle of durum wheat, destructive growth analysis was carried out for every 14 days, to measure dry matter weight, leaf area index (LAI), plant population and, at harvest, yield components and grain quality. The results indicated that OMWW without pre-treatments spread on a durum wheat crop during vegetative phase produced some necrosis of the leaves and caused a slow emission of secondary stems. However, in this stage, durum wheat showed good capability to recover. Plant dry matter accumulation was not significantly influenced by OMWW spreading since it occurred at the beginning of the vegetative stage, when plants grow quickly. No significant differences, neither for grain nor for straw yield, between the two treatments were highlighted. The results of 3 years of experiments showed that the dururn wheat crop can tolerate OMWW spreading during early growing stages. Great care should be used in spreading the wastewater uniformly on the soil, respecting the laws about soil capability to endure OMWW application. (C) 2003 Elsevier B.V. All rights reserved.