ISHS Acta Horticulturae 659: VII International Symposium on Protected Cultivation in Mild Winter Climates: Production, Pest Management and Global Competition
NUTRIENT SUPPLY IN SOILLESS CULTURE: ON-DEMAND STRATEGIES |
| Authors: | O. van Kooten, E. Heuvelink, C. Stanghellini |
| Keywords: | EC, greenhouse horticulture, irrigation, closed systems, water use efficiency, sustainable production, integrated nutrient and climate control |
| Abstract:
Efficient use of nutrients is of economic and environmental importance. In soilless cultures nutrient supply is coupled to water supply. Usually, a solution with a nutrient concentration (EC) and nutrient ratios based on average uptake rates is supplied. In more sophisticated strategies this may be adapted to crop developmental stage and/or radiation levels (e.g. reduced nutrient concentration during daytime at high radiation levels). Still, drain percentages of 30-40% are common in these systems, to avoid salt accumulation in the root environment and/or shortage of some nutrient ion. A nutrient supply closer to plant demand may be obtained when supply concentration is adjusted based on continuous EC measurements in the root environment or in the drain water. In such an automated supply system the total concentration (EC) of the water supply was nearly as low as the uptake concentration, and we obtained high yields with a substantially lower drain percentage (10-20%). Obviously, such a system cannot account for variations among uptake concentration of specific nutrients. Ideally, in a recirculation nutrient solution, each ion is measured continuously in the drain, and is added in agreement with its uptake. Preferably, this uptake is anticipated by model calculations to avoid large disturbances in the nutrient supply. Recently, a large-scale project under the title ‘Hydrion-line’ performed a proof of principle experiment showing the possibility of controlling different macro nutrients and water delivery based on model calculations of plant growth and nutrient distribution in the substrate and on on-line measurements of plant activity and crop status (Heinen et al. 2002). This combination may lead to higher water use efficiency with a lower nutrient input, while maintaining the same production levels. | |
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