ASSESSING RISK OF NITRATE LEACHING FROM THE HORTICULTURAL INDUSTRY OF ALMERIA, SPAIN

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.

Workshop Towards and Ecologically Sound Fertilisation in Field Vegetable Production

R.B. Thompson, M. Gallardo, C. Giménez

greenhouse, horticultural management, fertigation, nitrogen, horticulture

https://doi.org/10.17660/ActaHortic.2002.571.29