ISHS Acta Horticulturae 401: International Symposium on Growing Media & Plant Nutrition in Horticulture
DYNAMICS OF WATER AND NUTRIENTS IN CLOSED, RECIRCULATING SAND BED SYSTEMS: MODELING WATER FLOW, NUTRIENT TRANSPORT, ROOT WATER AND NUTRIENT UPTAKE |
| Authors: | M. Heinen, P. de Willigen |
| Keywords: | hydraulic properties, plant potential, root length density, substrate, simulation, transpiration |
| Abstract:
A simulation model based on physical properties of a substrate and plant root uptake can be a helpful tool in developing new closed cropping systems. In this paper the general equations for water movement and nutrient transport will be presented. The boundary conditions will be described, with special attention for root water and nutrient uptake. Root water uptake depends on root length density, on root hydraulic conductivity, on root radius, on the water potentials of the plant, rhizosphere and bulk substrate, and on the volume of substrate from which one root can take up. The actual transpiration is a function of plant potential and potential transpiration. Maximum possible nutrient uptake depends on root length density, on root radius, on bulk substrate concentration, on water uptake rate, on diffusion coefficient, and on the volume of substrate from which one root can take up. The actual nutrient uptake equals the minimum of required and maximum possible uptake. Two examples are presented for a thin layer cropping system. When natural soils are used as a substrate, saturated conditions will be present for prolonged times after irrigation has ceased, while this is not the case for a coarse substrate. These saturated conditions may limit oxygen supply to the root system. Therefore, coarse substrates are needed in thin layer cropping systems. In the second example it is shown that for a nutrient that is not taken up by the crop its concentration at the top of the substrate increases due to plant root water uptake and evaporation. | |
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