遮光と培養液のNO<SUB>3</SUB>/NH<SUB>4</SUB>比がNFT栽培トウガラシの生育•収量に及ぼす影響

Abstract

The effects of NO3 : NH4 mixture with a gram-N ratios of 10 : 0, 9 : 1 and 8 : 2 in the nutrient solution and shading pepper plants grown under NFT to 0, 25 and 50% full so- lar radiation on their growth, yield, and photosynthesis were investigated.Main stem and branch lengths increased significantly under shaded conditions. Fresh weight of leaf, stem, and roots of equally shaded plants were heavier at a NO3 : NH4 ratio of 9 : 1 compared to those grown at a ratio of 10 : 0.The pepper plants set fewer, smaller fruits in proportion to the degree of shading. Fruit yieid of the shaded plants increased significantly by replacing 10% of NO3-N with NH4-N in the nutrient solution.Dry weights of leaf and stem and leaf area increased under shaded conditions. As the NH4-N/NO3-N ratio in the nutrient solution increased, dry weight and leaf area decreased in fully exposed plants, whereas the trend was reversed in shaded plants.As the NH4-N/NO3-N ratio of the nutrient solution increased, leaf photosynthetic rates decreased in exposed plants, but increased slightly in shaded plants.Compared with exposed plants, shaded plants had considerably lower net assimilation rate (NAR) and relative growth rate (RGR) during the flowering and the early fruit development stage, 46 days after treatments, irrespective of the nitrogen sources in the nutrient solution. However, the differenes were observed in NAR and RGR during the later fruit maturing stage, 47 to 68 days after treatments.The results obtained in this study indicate that as a nitrogen source of NFT-grown pepper plants, 100% NO3-N is recommended under high solar radiation, whereas a NO3-N : NH4-N ratios of 9 : 1 or 8 : 2 is superior when the solar radiation is reduced.