Nutrient supply and fruit yields in tomato rockwool hydroponics under daily quantitative nutrient management: analysis and evaluation based on leaf area index

摘要

The aim of this study was to investigate whether daily quantitative nutrient management (QNM) consumed less nutrients without decreasing yields than conventional electrical conductivity (EC)-based management at a given leaf area index (LAI) in tomato rockwool hydroponics. Plants in a greenhouse were supplied with low (QNM-L) or high (QNM-H) daily amounts of nutrients at a given daily water uptake for QNM treatments and with a nutrient solution at a constant EC with an open system for EC-based management from April to August 2010. Variation of LAI was obtained by varying plant density in each nutrient supply treatment. When compared at the same plant density, the amount of nutrients supplied during the experiment and cumulative total fruit yield were significantly lower in QNM treatments than in EC-based management associated with a lower LAI. In the relationship between fruit yields or nutrient supply per unit ground area and LAI, the total and marketable fruit yields and nutrient supply increased linearly with the increasing LAI in all treatments. At a given LAI, QNM-L supplied the least nutrients per ground area followed by QNM-H, and EC-based management supplied the most. In the total or marketable fresh fruit yield per unit ground area, there was no significant difference in slope or intercept among the three treatments, indicating that fruit yields on a ground area basis can be accounted for by LAI irrespective of the nutrient supply treatment. The conclusion is that daily QNM was more nutrient-efficient than EC-based management without lowering fruit yields if the same LAI was achieved. Although QNM and EC-based management gave a comparable marketable yield at a given LAI, QNM treatments yielded more marketable fruits with smaller individual fruits than EC-based management, implying that the relationship between the fruit number and individual fruit weight is a trade-off at a given LAI.