Effects of green-manure and organic fertiliser on organic maize (Zea Mays L.) in south Tuscany

Summary

Green-manure in Mediterranean stockless organic farms is a useful tool to improve nitrogen availability, reduce production cost and conserve soil fertility. A 2-year on farm research was carried out in Tuscany (Italy) to evaluate the effect of 3 different green manures (Hordeum v. + Avena s. mixture, Trifolium s. + Avena s. mixture, Vicia faba var. minor) and 2 levels of organic N fertilization (0 and 120 Kg N ha-1) on maize in 2004 and 2005. Green manures were ploughed into the soil in April 2004 and organic fertiliser was applied before sowing; neither green manure nor fertilizers were applied in 2005 to evaluate the residual effect of the treatments. The effect of the distribution of organic fertilizer was not efficient in comparison to green-manure. Field-bean increased maize productivity in both the years thanks to an increase in N availability as suggested by its total N uptake that exceeded the uptake of maize after control by 19.5 and 14,3 Kg N ha-1 in the first and second year. In our experimental conditions, with low organic matter and nitrogen content in the soil, the use of grasses as green-manure caused temporary immobilisation of N and maize yield reduction.