Crop Nutrient Requirements and Management in Protected Cultivation

Keywords: Crop model, Substrate model, Nutrient uptake, Nitrogen, Phosphorus, Potassium, Greenhouse horticulture.

In greenhouses, above and below-ground conditions can be controlled to a large extent. This opens possibilities for a precise control of water and nutrient flows and crop production and quality. To do this requires an accurate tuning of the supply of nutrients and water to the demands of the plant. In this paper first the regulation of growth by nitrogen (N) and phosphorus (P) is discussed. The effects on growth are factorised into effects on assimilation rate, leaf area expansion and dry matter partitioning. Experiments have quantified the dynamics of growth, water and nutrient uptake of tomato plants to a temporal N, potassium (K) and calcium (Ca) shortage. Plant nutrient concentration shows a distinct ontogenetic change during plant development. Several approaches to quantify this change are discussed. Subsequently, a crop growth model and a substrate model are described and tested. The crop model simulates crop growth as well as plant-water and plant—nutrient relationships. The substrate model describes water movement, solute transport, and root uptake of water and nutrients in the substrate (rockwool). The crop model is used to show some effects of the greenhouse climate on water and nutrient uptake. Subsequently this crop model combined with the substrate model is used to simulate effects of EC on plant growth and on transport and uptake processes in the root zone. Finally, it is shown how the combined crop and substrate model can be used in a control system for water and nutrient supply.

L.F.M. Marcelis, C.C. De Groot¹, F.M. Del Amor², A. Elings and P.H.B. De Visser, Plant Research International, PO Box 16, 6700 AA Wageningen, The Netherlands.

M. Heinen, Alterra, Green World Research, PO Box 47, 6700 AA Wageningen, The Netherlands.

¹ Present address: Bejo Zaden BV, PO Box 50, 1749 ZH Warmenhuizen, The Netherlands.

² Present address: Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario. 30150 La Alberca, Murcia, Spain.

36 Pages, 17 Figures, 1 Table, 81 References.