The potential of Crotalaria juncea L. as a summer green manure crop in comparison to Brassicaceae catch crops for management of Meloidogyne incognita in the Mediterranean area

A study was carried out in a glasshouse, in pots, on the life cycle of Melodoigyne incognita on Crotalaria juncea (sunn hemp), in comparison with other catch crops of the Brassicaceae family (Eruca sativa, Raphanus sativus ssp. oleiformis, Reseda luteola) and Solanum lycopersicum (tomato) as control. All the tested plants were effective in decreasing M. incognita populations in soil. Particularly, after 13 weeks from the inoculation of nematode second stage juveniles, the nematode’s reproduction factor on C. juncea (Rf = 0.2) was similar to that on E. sativa and R. sativus, and lower than on R. luteola (Rf = 0.5), in comparison with tomato (Rf = 42.0). Field trials on the evaluation of the suppressive effect of sunn hemp towards M. incognita juveniles and its adaptability to the climatic conditions of Po Valley (Northern Italy) were also reported. In field conditions, C. juncea significantly decreased M. incognita population in infested soil (Rf = 0.2), whereas tomato increased it (Rf = 148.09). The cultivation trials confirmed the adaptability of sunn hemp to the Po Valley summer conditions and the high nitrogen content recorded particularly in leaves. Furthermore, soil cover in summer, before autumn-winter crops, could prevent mineralization of organic matter, avoiding the typical summer carbon depletion of Mediterranean soils.