ISHS Acta Horticulturae 700: International Symposium Towards Ecologically Sound Fertilisation Strategies for Field Vegetable Production
MANAGEMENT FACTORS CONTRIBUTING TO NITRATE LEACHING LOSS FROM A GREENHOUSE-BASED INTENSIVE VEGETABLE PRODUCTION SYSTEM |
| Authors: | R.B. Thompson, C. Martínez, M.D. Fernandez, J.R. Lopez-Toral, M. Gallardo, C. Gimenez |
| Keywords: | nitrogen management, irrigation, nutrient management, pepper, capsicum |
| Abstract:
Considerable nitrate (NO3-) contamination of underlying aquifers is associated with greenhouse vegetable production in Almería, Spain. Eighty percent of cropping occurs in soil, the rest in “open” hydroponic systems. To identify the management factors associated with NO3- leaching loss from soil-based cropping, a survey of irrigation and N management practices was conducted on commercial farms, and a field study was conducted using lysimeters. The survey of management practices showed that N and irrigation management were based mostly on experience. Approximately one third of greenhouses were clearly applying total irrigation volumes during the growing season that were in excess of crop water requirements. In the first six weeks after transplanting, excessive volumes were applied in most greenhouses. All farmers routinely used large irrigations during the non-cropping period to apply soil disinfectant, to wet the soil profile before transplanting a new crop, and to leach salts. N supplied by sources other than mineral N fertiliser such as manure or soil mineral N was seldom considered when developing N fertiliser plans. Very large applications of manure had been applied in most greenhouses. In the field study, appreciable NO3- leaching occurred following large irrigations given for soil management purposes and in the first three weeks of the crops as a result of large pre-transplant irrigations and frequent irrigation just after transplanting. NO3- concentration in drainage was generally 6-12 mmol L-1 (350-600 mg NO3- L-1), even when nutrients were not applied. Overall, these studies suggest that mineralisation of soil organic N, from manure applications, and/or accumulation of soil mineral N during cropping created a risk for NO3- leaching, and that drainage associated with irrigations during the non-cropping period and in the early phase of the crop resulted in appreciable NO3- leaching loss. | |
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