Increasing the electric conductivity (EC) of the nutrient solution for growing hydroponic tomatoes (Solanum lycopersicum L.) is an effective way to increase fruit sugar content. The potential of bittern and coarse salt (NaCl) to cause high-EC stress, thereby improving fruit yield and quality in tomato plants under single- or double-truss cultivation were compared. Bittern is a by-product of the salt manufacturing process; it is easy to use and inexpensive. In particular, bittern is more convenient than common salt for high-EC treatment, because it is distributed as a solution, whereas common salt must be dissolved to very high concentration. The experiments reported herein were conducted during two growing seasons: spring and autumn. High-EC stress treatments (bittern or coarse salt) started when the largest fruit on the first truss was 4 cm in diameter. Fruit yield and Brix sugar content in the bittern treatment were similar or higher than in the salt treatment under both cultivation schemes. The EC of the bittern-added nutrient solution increased faster than that of the solution with added coarse salt. This trend was probably caused by the different ion compositions of bittern and coarse salt. There were no differences in tomato growth among treatments. Thus, bittern is a practical and effective additive for hydroponic single-truss tomato cultivation.

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A new disbudding method using a water jet nozzle was developed. An experiment was conducted on 32-year-old satsuma mandarin trees (cv. Okitsu wase) bearing many fruits. The disbudding treatment was applied to selected lateral shoots 1 day after budding (March 31, transverse bud diameter: 1.24 mm), 7 days after budding (April 6, transverse bud diameter: 2.30 mm), 16 days after budding (April 15, transverse bud diameter: 2.86 mm), or 24 days after budding (April 23, transverse bud diameter: 4.99 mm). Two types of nozzles with different discharge volumes (WJN1: 43.8 mL/s; WJN2: 29.3 mL/s) were considered for the bud removal rate and time required. As a result, NNZO12 was more successful for removing buds. When the nozzle with the higher discharge volume (WJN1) was used 1 day after budding, the time required was 49.5% of that needed for manual disbudding, and the removal rate was 96%. Because the peduncle became thick with time, the time required to remove buds increased; from these findings, it was considered that the treatment up to 7 days after the sprouting (bud diameter 2.3 mm) was effective for disbudding using the water jet nozzle. No significant difference was found in the required time when the treatment was applied more than 7 days after budding. The development of new shoots could be damaged if the water jet disbudding was applied to very small buds just after sprouting.

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Sunflowers are grown as oilseed crops in every region of Japan, though the residues left after harvesting are seldom utilized. Recently, sunflowers have received a lot of attention for their use as landscape crops for tourist attractions and/or catch crops to perform the uptake of excess plant nutrients in the soil. This research aims to clarify the accumulation characteristics of carbon and nitrogen in sunflowers at each growth stage, and the reuse of crop residues after harvesting is discussed. Sunflowers were cultivated in 3×3 m plots with varying planting densities and the fertilizer conditions at the university farm. Growth changes in the sunflowers were observed and samples were obtained at three growth stages, namely, flowering, just after flowering, and harvesting. Dry matter, calorific value, and carbon and nitrogen content were measured and analyzed for each sunflower region. As a result, the following was revealed: the calorific value of stems and leaves was nearly equal that of seeds, sunflower biomass increased in regions with a higher planting density, and one third of the total nitrogen uptake was accumulated in seeds during grain filling.

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