Variations in water and macronutrient uptake of soilless tomato as affected by the nutrient solution composition

Abstract

Greenhouse growers must reduce the nutrients that leach from soilless growing systems. To enable continued use of nutrient solutions, the water and nutrient uptake by plants in soilless systems needs to be quantified. Plants were grown in water culture with different nutrient solution compositions to determine the nutrient uptake of soilless tomato cultivation. The nutrient concentration (measured as electrical conductivity [EC]; mS cm⁻¹) and macronutrient ratios were varied in four trials. Nutrient uptake was determined through solution and tissue analysis. Water uptake decreased from 62 and 64 L plant⁻¹ (for cultivars ‘MFH 9343’ and ‘FA593’, respectively) to 58 and 46 L plant⁻¹ as the EC increased from 0.8 to 4.0 mS cm⁻¹. The nitrogen, phosphorus and potassium uptake was increased at higher ECs. The calcium, magnesium and sulphur uptake was only affected by the nutrient solution concentration. Calcium uptake decreased with an increase in nutrient solution concentration. The nutrient uptake concentrations (UC^Ca; mmol L⁻¹) did not differ significantly between the cultivars at an EC of 1.6, 2.4 or 3.2 mS cm⁻¹. However, at a low EC the UC^Ca was 2.03 for FA593 and 1.76 for MFH9343. The results indicate that macronutrient uptake depends on the concentration of macronutrients in the rootzone.