Effect of greenhouse soil bio-disinfection on soil nitrate content and tomato fruit yield and quality

Abstract

Intensive horticultural practices in the greenhouse can cause proliferation of soil phytopathogenic organisms and pollution of groundwater from nitrate leaching. Among the different soil disinfection techniques, bio-disinfection through the addition of organic amendments (OA), with subsequent solarisation (biosolarisation) or without (biofumigation), is an efficient and economically viable alternative for the control of soil pathogens. This greenhouse experiment was conducted to initiate the process of conversion of a conventional tomato culture to organic farming. The effects of OA applied through biofumigation and biosolarisation in the first season on soil nitrate concentration and tomato fruit yield and quality were evaluated with the following treatments: control, no OA; T1, 0.3 kg m–2 of dehydrated pellets of Brassica carinata seed meal; T2, 0.8 kg m–2 of packaged and dehydrated B. oleracea var. italica; T3, T2 + 0.15 kg m–2 of dehydrated poultry manure; T4, T1 + 0.16 L m–2 of microbial cocktail. The experiment was carried out over the autumn crop cycle of two seasons (2011–12, 2012–13). Addition of OA increased soil nitrate concentration, more so with biosolarisation. Total and marketable yield of tomato and number of marketable fruits were higher in the biosolarised plots in the first crop after treatments. No effects were observed in the second crop after treatments. Except for tomato fruit firmness, quality attributes (size, soluble solids, acidity and colour) improved with some OA treatments. The supply of OA through biosolarisation is a soil disinfection technique with potential to minimise the impact of nitrate leaching and to provide improved yield and quality of tomatoes.