Subcritical water (SW) is produced from organic matter decomposed under high temperature and high pressure. Development of technique to use it for fertilizer contributes to recycling organic waste from agriculture and other human activities.
Research was conducted to analyze the fertilizer characteristics of SW and its practical use in field. SW contains much organic nitrogen, and organic acid inhibits crop growing.
Therefore, crop growth were compared in the following treatments, 1) to evaluate the influence of SW on crop growth compared with chemical fertilizer (CF) or no fertilizer (NF), 2) to analyze the effect of soil temperature difference covering soil with white (W) or clear (C) plastic mulch before the transplanting, and 3) to relieve the inhibitions and increase the effects of SW fertilizing on -1 or -21 DAT. Ten plots were made in the combination of these three types of treatments, and crops were grown until 32 DAT.
Growth was promoted in the plots of fertilized SW on -21 DAT comparing with -1 DAT. Covering with C mulch, increased soil temperature more than W one, and enhanced nitrification. Crops in the plot of SW, -21 DAT and C mulch showed the largest grown of all SW plots on 32 DAT. However, the large inhibition from 1 to 4 DAT in its plot was estimated, because its leaf area on 32 DAT was smaller than all CF plots despite higher growth in the SW from 4 to 32 DAT than the plot of CF, -21 DAT and W mulch.
