We examined the effect of nitrogen (N) topdressing at the spike formation stage on yield and ripening physiology of the naked barley in Yamaguchi. N dressing was applied as basal dressing (4 or 6 g m^-2) -topdressing at tillering stage (2 g m^-2) -topdressing at spike formation stage (2,4 or 6 g m^-2) in five combinations (4-2-2, 4-2-4, 4-2-6, 6-2-2 and 6-2-4 g m^-2) with a total N of 8,10 or 12 g m^-2 in two seasons, 2010/2011 and 2011/2012. Yield and its components, crop growth rate (CGR), spike and leaf area index (S & LAI), net assimilation rate (NAR), and N contents of grains, spikes, leaves and stems were measured. Grain yield, spike number and biomass production were the highest in the 4-2-6 g m^-2 plot (total 12 g m^-2 N) in both seasons. However, topdressing at a later stage did not have a positive effect on grain yield when total N was 10 g m^-2, because the grain yields were lower in the 4-2-4 g m^-2 plot than in the 6-2-2 g m^-2 plot. CGR, S&LAI and NAR were also the highest in the 4-2-6 g m^-2 plot. The N content of whole plant was already highest at the full heading stage in the 4-2-6 g m^-2 plot, and the N uptakes during the grain filling period was also highest in the 4-2-6 g m^-2 plot in both seasons. CGR in the early grain filling period was lower in the 4-2-4 and 6-2-2 g m^-2 plots (total 10 g m^-2 N) than in the 4-2-2 g m^-2 plot, (total 8 g m^-2 N) due to lower NAR.

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We evaluated the salinity tolerance of 13 cultivars of quinoa (Chenopodum quinoa Willd.) and 3 other crops, rapeseed, Japanese radish and Komatsuna, at germination and early growth stage. To clarify the varietal differences in salinity tolerance of quinoa, we evaluated the germination rates by irrigation treatment using 6 different concentrations (0, 200, 400 600, 800 and 1000 mM) of NaCl solutions. Of the 13 cultivars studied, CICA-127 showed the highest salinity tolerance at germination having a germination rate of 58.8% in 600 mM NaCl solution at 5 days after sowing. The other crops (rapeseed, Japanese radish and Komatsuna) showed low salinity tolerance and could not germinate in 600 mM NaCl solution. Early growth of quinoa and the other crops was evaluated using 1/10000a pot with 0.5–1.0 g NaCl per 100 g soil. Top dry weight and leaf area of quinoa were higher in all NaCl-applied plots than in the control plot. In this study, quinoa cv. CICA-127 was found to be the most tolerant to salinity at germination and early growth stage.

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Chinese milk vetch (CMV) (Astragalus sinicus L.) at flowering-stage is a green manure traditionally used as alternative basal nitrogen in paddy rice fields. In order to evaluate the nitrogen availability of mature-stage CMV, compared with the flowering-stage CMV, we carried out field cultivation and incubation studies using ill-drained Gley soil with either mature-stage CMV incorporated. The results showed that mature-stage CMV provided less available nitrogen for early rice growth than the fresh flowering-stage CMV, resulted in lower panicle number and hence lower total grain number of rice. Contrary to our expectation, which mature-stage CMV replace nitrogen topdressing due to the prolonged nitrogen mineralization, the small amount of the mineralized nitrogen was insufficient to support the rice growth. Nevertheless, rice cultured with the mature-stage CMV achieved a yield over 450 g m^-2, without the use of agrochemicals. Mature-stage CMV was suggested to be potentially applicable under ill-drained soil conditions, if applied heavily.

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In two growing seasons (2008-09 and 2009-10) we applied nitrogen topdressing every 1 to 2 weeks from stem elongation to ripening, and examined the effects on yield, grain protein content, and dry matter and nitrogen accumulation in the spikes after anthesis in ‘Yumeshihou’ wheat. Topdressing at the stem elongation stage about 16 days before anthesis, and that at the mid-grain-filling stage about 20 days after anthesis tended to increase the yield in both growing seasons. The topdressing at about anthesis did not increase the yield owing to a decrease in grain number per spike. Dry-matter accumulation after anthesis was increased by topdressing at the stem-elongation and mid-grain-filling stages. Grain protein content was increased by topdressing at anthesis to ripening stage but not by topdressing at the stem elongation stage. The lack of increase in grain protein content in the plants topdressed at the stem elongation stagewas attributed to an increase in dry matter accumulation before and after anthesis as well as nitrogen accumulation in the spikes. Topdressing after anthesis significantly increased in grain protein content in plants because nitrogen accumulation in the spikes was greater than the dry matter accumulation after anthesis.

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Salinity stress as well as water stress impairs crop production in saline soil. This study was conducted to examine the relationship between water use, which may depend on root growth, and dry matter production in rice. Paddy soil of 1∼10 kg was put in appropriate pots. A definite amount of NaCl solution corresponding to 50% of soil weight was applied to establish saline soil containing NaCl at 0 (control), 1 and 2 g kg^-1. Seedlings of salt-tolerant cultivar IR4595-4-1-13 and normal cultivar Nipponbare were transplanted to the pots which were not irrigated thereafter. Shoot and root dry weight on the day when leaf ceased to elongate increased as soil amount increased, and decreased as soil salinity increased. Shoot growth decreased with the increase of plant sodium concentration. The amount of soil water increased with the increase in soil weight and salinity, indicating that evapotranspiration was decreased due to soil salinity. Shoot dry weight increased in proportion to the evapotranspiration. Soil water content was low in the control which had vigorous root growth, and high in the high-salinity soil which had poor root growth. It was concluded that rice shoot growth on saline soil increased in proportion to evapotranspiration and poor root growth may be responsible for reduced evapotranspiration.

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We conducted a field survey to determine the causes of rice leaf injury observed in rice paddy field located in hilly and mountainous northern regions of Nagasaki. (1) Solar radiation in the mountainous region where the rice “hakare” symptom occurred was about 20% lower than that of the low altitudes. (2) The top / root ratio of the rice plant (dry weight basis) was higher in the injured rice than that with normal growth. (3) Our results suggest that delaying the time of transplanting than the conventional cultivation reduces the occurrence of rice “hakare” symptom. (4) With the approaching of low pressure system at the end of rainy season, the local dry wind blows up in the mountainous rice paddy areas and the difference in temperature and humidity between high and low altitudes become larger. From the above, we concluded that rice “hakare” symptom occurs as a result of the following factors. The imbalance growth between the above-ground and underground parts of the rice plant due to the shortage of solar radiation during rainy season, and the dry wind peculiar to the mountainous region enhanced the transpiration from the leaves and stems cause a deficiency of water in newly growing leaves.

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