EVALUATION OF SHEEP GRAZING EFFECTS ON NEMATODE COMMUNITY, INSECT INFESTATION AND SOIL FERTILITY IN SWEET CHESTNUT ORCHARDS: A CASE OF STUDY

In sweet chestnut cultivation, important ecosystem in Europe, the moderate sheep grazing practice may have some beneficial effects in organic farming. Its impact, on soil fertility, soil nematode community and level of fruit infested by tortricids and curculionids was evaluated in a case of study in Tuscany (Central Italy). An organic farm with sheep grazing system (SG) based on long-term field application was compared with an adjacent organic farm with poultry manure system (PM). In both managements, no treatment to control pests and diseases was applied and 0.19 kg /plant of nitrogen were distributed. SG increased twice the amount of organic C, total N and available P than PM. Moreover, the salinity effect of uric acid significantly increased the pH values in SG (from 5.0 to 6.2). The greatest accumulation of organic matter under SG provided stability in nematode community structure and the plant parasitic nematodes decreased. The analysis on the nematodes emerged from Galleria mellonella larvae, revealed that the abundance of native entomopathogenic nematodes was low and not effective to control insect pests. The sheep demonstrated to be the effective predators of tortricid and weevil larvae and in November, the total infestation was significantly lower in SG (34.3%) than PM (54.3%).