Nematode indicators as integrative measures of soil condition during conversion from conventional to organic rice production in Italy: a case study.

The Vercelli district is one of the most technologically advanced rice cultivation areas in the world, but the sector is causing serious environmental problems. This study aimed to acquire information on the ecological impact during conversion from conventional to organic farming, using the nematode community as an indicator of soil quality. An organic farming system managed with a 5-year crop rotation, based on rice (4-years) and soybean (1-year), was compared, during the fourth and fifth year after conversion, with conventional and integrated farming systems, both based on monoculture of rice. The relationship between soil biology and the type of farming system was explored by examining the nematode community, assessing maturity, plant parasitic, basal, enrichment, structure, channel indices and diversity-weighted abundance. No significant differences in total soil organic C, total N and C/N ratio were found between the management systems. Total nematode abundance was not strongly affected by the conversion, but the response of the nematodes to change varied with the trophic groups, year by year. The conversion from conventional to organic farming represented a disturbance factor. The introduction of the soybean crop determined a marked change in nematode composition; the persistent nematode population was only 20%, while the colonizer reached 80%. The indices showed that the nematode community varied between the farming system; in both years maturity index was lower in organic than in other management systems. Higher values of pH, C/N ratio and available P favoured basal and channel indices, while total N was negatively correlated. [ABSTRACT FROM AUTHOR]