ISHS Acta Horticulturae 571: Workshop Towards and Ecologically Sound Fertilisation in Field Vegetable Production
ASSESSING RISK OF NITRATE LEACHING FROM THE HORTICULTURAL INDUSTRY OF ALMERIA, SPAIN |
| Authors: | R.B. Thompson, M. Gallardo, C. Giménez |
| Keywords: | greenhouse, horticultural management, fertigation, nitrogen, horticulture |
| Abstract:
Approximately 24,000 ha of plastic greenhouses are used for intensive horticultural production in the coastal region of Almeria, in south-eastern Spain. Underlying aquifers have appreciable concentrations of NO3-, suggesting contamination from the horticultural industry. Ninety-two percent of cropping occurs on soils, the other 8% with "open" hydroponic systems. As part of a survey conducted to identify nutrient and irrigation management practices that risk causing nitrate contamination of groundwater, 52 greenhouses were sampled to determine mineral N in the soil profile at the end of a crop. 28 greenhouses were sampled to 40 cm depth, and 17 to 60 cm (also 7 greenhouses to <40 cm). Total amounts of NH4+-N, NO3--N and mineral N (combined NH4+-N and NO3--N) to these depths were determined. In 28 greenhouses sampled to 40 cm, mineral N at sampling was 153–776 kg N ha-1, with mean and median values of, respectively, 317 and 279 kg N ha-1. In 17 greenhouses sampled to 60 cm, mineral N at sampling was 282–1,654 kg N ha-1, with mean and median values of, respectively, 527 and 360 kg N ha-1. On average, NH4+-N was 58% of mineral N. Soil NO3--N showed a large and skewed distribution between greenhouses, with many having relatively small amounts, and a small number having very large amounts. The variation in soil NO3--N data may have resulted from considerable denitrification loss occurring in some greenhouses. The soil mineral N data suggested that large amounts of mineral N entered the soil and were potential sources of contamination of underlying aquifers. Management practices to reduce this risk are proposed. | |
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