In order to utilize high EC water for fertigation, the effects of irrigation frequency, fertilizer concentration, salinity for Komatsuna (Brassica rapa var. perviridis) were investigated. We observed significant interactions between fertilizer concentration and salinity on the number of leaves and shoot fresh weight, and between salinity and irrigation frequency on root dry weight. We found that low fertilizer concentration increased leaf length and shoot fresh weight at the beginning of cultivation, whereas leaf length, shoot fresh weight, shoot dry weight, root dry weight decreased at the end of cultivation. Additionally, we found that salinity decreased leaf length, number of leaves, shoot fresh weight, leaf area, shoot dry weight, and root dry weight. High irrigation frequency increased leaf length and root dry weight. The average soil volumetric moisture content increased after adding salt in the high-fertilizer concentration plot. High fertilizer concentration increased the average soil moisture content on the low-frequency irrigation plot. Overall, the average soil volumetric moisture content was higher in the high-frequency irrigation plot than in the low-frequency irrigation plot. It is considered that the root area can be maintained in the wet state, which contributes to water-efficient cultivation. Growth analysis showed no significant interactions among all the parameters studied, but showed a clear trend in the relative growth rate (RGR), net assimilation rate (NAR), and leaf area rate (LAR) in each growth period. There were significant correlations between RGR and NAR and between RGR and LAR. Correlation between RGR and NAR was higher than that between RGR and LAR. It suggested that the changes in dry weight yield were due to the changes in photosynthetic rate.

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