抄録
We attempted to establish an organic fertigation system by suing corn steep liquor (CSL) as liquid fertilizer, instead of the usual inorganic fertilizer. CSL is a byproduct of corn starch manufacturing. It is a viscous liquid and contains about 3% each of N, P_2O_5 and K_2O. We found that CSL had to be diluted less than 4 times to prevent decay and the irrigation tube had to be rinsed just after nutrient liquid application by rinsing through an egual amount of tap water to keep the irrigation tube clean. By using this organic fertigation system, we conducted a cultivation experiment for practical use and compared it with the same system using inorganic liquid fertilizer and with the conventional method. This system worked during the experiment without trouble. Height, stem diameter and chlorophyll content of plants grown with the organic fertigation system were the lowest among the three cultivation methods. Leaf area and photosynthetic activity were higher when grown with the organic fertigation system as compared with the other systems, especially for the higher leaves. Greater leaf area and photosynthetic activity of organic fertigation-grown plants led to higher yield on higher fruit trusses as compared with plants grown with the other systems, and the reverse was true for the lower trusses. As a result, about the same yield was obtained among the three cultivation methods. Brix sugar content was the highest in basal dressing, probably because high soil EC stimulated fruit sugar accumulation. While CSL has been used mainly for feed of livestock, a culture medium for bacteria and so on, this system showed that CSL could be sued as liquid fertilizer for fertigation to produce vegetable. Moreover, it was indicated that fertigation systems including organic fertigation provide an alternative fertilizer management for reduction of chemical stress on the rhizosphere.
