Daily based quantitative nutrient management in rockwool hydroponics: Growth and yield of tomato and nutrient use at elevated CO2

Abstract

The efficacy of daily quantitative nutrient management (QNM) in tomato rockwool hydroponics under CO2-enriched conditions was tested. Three levels of nutrient supply based on daily water uptake were compared with conventional electrical conductivity (EC)-based management. A newly developed automatic QNM system with server and client controller prototypes was used to control nutrient supply. Plants in a greenhouse were supplied with 0.5 (S), 1.0 (M) or 1.5 (L) times the optimal daily amount of nutrients for normal CO2 conditions from October 2009 to February 2010. EC-based management produced highest cumulative total fruit yield during 16 weeks of fruit harvest followed by L, M and S treatments, in that order. There was no significant difference in cumulative marketable fruit yields in EC-based management, L and M treatments, but marketable yields from these three treatments were significantly higher than S treatment. Fruit dry matter content and fruit soluble solid content in QNM treatments were almost the same or higher than fruit grown in EC-based management. The amount of nutrient used during the experiment in S, M and L treatments was 10, 24 and 42%, respectively, of the amount used for EC-based management. Nutrient use efficiency (NUE), defined as marketable fruit yield per unit of the amount of nutrient used, in all three QNM treatments was higher than in EC-based management. Thus, daily QNM can reduce nutrient use without lowering fruit yields and quality under CO2-enriched conditions. The M or L treatment provided optimal balance between fruit yield and NUE. The L treatment gave slightly higher marketable yield but lower NUE than M treatment. © 2010, The Society of Agricultural Meteorology of Japan. All rights reserved.