No abstract

Although seed priming is well known to be an effective method for enhancing seed vigor and seed performance, the efficacy of priming (soaking in water and re-drying) on the physiological performance of iron-coated rice (Oryza sativa L.) seeds under submerged conditions, and the physiological mechanisms of coleoptile elongation of the primed rice seeds under anoxia, have not been well elucidated. In the present study, primed and unprimed rice seeds with or without iron-coating were produced. We examined the physiological performance of these rice seeds and the physiological efficacy of priming on coleoptile elongation under anoxia. For the primed rice seeds, seed germination, coleoptile elongation, seedling emergence and the establishment of iron-coated rice seeds all improved considerably, which resulted in an increase of plant height and dry weight for the iron-coated primed rice seeds. Increases in -amylase activity and glucose concentration over time were significantly higher in the primed rice seeds than in the unprimed rice seeds. Under anoxia, the -amylase activity and soluble sugar concentration were significantly higher in the primed rice seeds than in the unprimed rice seeds. The glucose and fructose concentrations in the coleoptiles were significantly higher in the primed rice seeds than in the unprimed rice seeds, suggesting that the stimulated coleoptile elongation is partly related to the increased availability of soluble sugar from the seed to the coleoptiles. The increased availability of soluble sugar from the rice seeds to the coleoptiles can be assumed to help maintain glycolytic flux and alcoholic fermentation under the submerged conditions. These results clearly indicate the efficacy of priming on iron-coated rice seeds, and that the coleoptile elongation of the primed rice seeds can be partly ascribed to the sugar availability from the rice seeds to the coleoptiles. Therefore, the use of primed rice seeds for iron coating is highly effective to induce the emergence and establishment of stable seedlings in direct rice sowing systems.

Root-proof capillary wick culture is expected to eliminate water drainage. Application of controlled release fertilizer instead of liquid fertilizer may be economical because liquid fertilizer equipment would not be required. In this experiment, large-fruited tomato was grown at three fertilizer levels; 11.3 gN (LF), 16.2 gN (MF), 21.0 gN (HF) per plant to evaluate a suitable level of controlled-release fertilizer needed for the culture of 15 trusses between October and July. For HF, the experiment was terminated at the end of December due to severe wilting. There was no significant difference in marketable fruits weight between LF and MF, but the soluble sugar content was higher in MF. The stem diameter at the end of experiment was larger in MF. The amount of nutrient remaining in the substrate was lower for N, P 2 O 5 and K 2 O, but greater for CaO and MgO at each fertilizer level. Each nutrient concentration in the substrate solution was low after the middle of February for both LF and MF. Therefore, enrichment of nutrients in the substrate solution did not occur in either LF or MF. In conclusion, the amount of 16.2 gN per plant may have been sufficient for 15 trusses of tomatoes undergoing forcing culture.

No abstract

In many agricultural areas, nitrogen pollution of groundwater owing to the influence of surplus chemical fertilizer inputs has been reported. In this study, we examine a cultivation system for satsuma mandarin that reuses nitrogen in groundwater to retrench chemical fertilizers and reduce their environmental impact. Specifically, we conducted a field test combining groundwater use and a drip irrigation and liquid fertigation system with year-round plastic mulching, a popular and stable production system for high-quality fruit. We quantitatively evaluated the eutrophication impact using the life cycle assessment method. Consequently, in a standard cultivation system, the nitrogen emission had a very high impact of approximately 90% of the eutrophication impact. In the drip irrigation and liquid fertigation system, the nitrogen emission was drastically decreased and the eutrophication impact dropped to approximately 15% of that of the standard cultivation system. When the nitrogen balance was evaluated for the basin on the basis of a water source well, the amount of nitrogen in groundwater used by the drip irrigation and liquid fertigation system exceeded the amount of nitrogen emission during the satsuma mandarin production stage. Moreover, according to the estimated eutrophication impact, this cultivation system could be used as a purification system.