Green manure plant biomass evaluation and total mineral nitrogen in the soil of a peach-orchard system

This research was carried out in a warm-arid area of Southern Italy (Basilicata region) on a peach orchard, green manured with a Vicia faba and Avena sativa mixture. Dry matter biomass production of the canopy in 1995, 1996, 1997 was 7.5 (N 2.3%), 5.8 (N 3.4%) and 5.1 (N 2.6%) Mg ha-1 respectively. In 1996, by incorporating cover crops at peach bloom time, it was found that green-manuring ensured a sufficient supply of mineral nitrogen when the demand from peach trees was greatest. Green-manuring determines high concentrations of mineral nitrogen in the soil in autumn, when the nitrogen is subject to leaching, owing to higher rainfall and reduced demand from the trees. The results obtained from the field trials suggest: - the possibility of synchronizing the supply of mineral nitrogen with demand from the trees by incorporating cover crops into the soil at bloom time and by adding small amounts of chemical fertilizers soon after the green manuring; - that cover crops should be sown towards the end of October so that they can function as catch crops for the mineral nitrogen in the soil; - the possibility of regulating the mineralization processes of green manure by acting on the irrigation management technique; - that during dry years, earlier irrigation is necessary at peach bloom time so as to avoid dangerous water stress due to the strong water uptake by the cover crops during their intense vegetative growth phase.