We evaluated the appropriate planting density in ridge-making narrow-row cultivation of two soybean cultivars “Enrei” and “Ayakogane” in drained paddy fields with heavy clay soil in Niigata prefecture. Two cultivars differed in their adaptability to dense planting cultivation. The relative photosynthetically active radiation (PAR) under the plant canopy with narrow row cultivation decreased with increase in the planting density. The relative PAR at any planting density was less than 10% at the flowering stage, which was sufficient to suppress weed growth. Higher planting density led to more spindly growth at the maturing stage in both cultivars. The lodging index of “Enrei” in narrow row cultivation with the planting density over 17.8 plants m–2 was higher than that in conventional cultivation with 75 cm interrow space and 8.9 plants m–2. The lodging index of “Ayakogane” in narrow-row did not differ from that in conventional cultivations. The seed yield of both cultivars tended to increase with increasing planting density. The seed yield of “Enrei” cultivated at a planting density over 17.8 plants m–2 was significantly higher than that under conventional cultivation. The yield of “Ayakogane” was also increased at a planting density over 13.3 plants m–2. The appropriate planting density to avoid lodging in ridge-making narrow-row cultivation of “Enrei” was judged to be 8.9–13.3 plants m–2 to avoid lodging, and that of “Ayakogane” 13.3–26.7 plants m–2 to promote seed yield.
In Hokkaido, dense planting of rice has been recommended to keep a higher percentage of whole grain (PWG), but sparse planting is demanded to save labor and cost. A field experiment of sparse planting was conducted in NARO Hokkaido Agricultural Research Center from 2013 to 2015. Rice cultivar “Nanatsuboshi” was transplanted with 30 cm row spacing at 4 levels of hill spacing and 2 levels of seedling number per hill (SNPH). Temperature in cropping season was higher than in an average year in all of the 3 years, but reduced SNPH resulted in lower grain yield due to lower percentage of ripened grains than standard SNPH. Wider hill spacing did not reduce the yield significantly, but tended to decrease PWG. Spikelet number per panicle (SNPP) was negatively correlated with PWG, and the PWG was lower than 70% when SNPP exceeded 70 under a low temperature condition at the grain-filling stage (cumulative mean temperature at 40 days after heading was lower than 800°C). In standard SNPH, SNPP with 22 cm hill spacing was 70.7. Therefore, to maintain more than 70% PWG, hill spacing should not be wider than 22 cm.
We analyzed the correlation of wheat yields with climate conditions in Northern Kyushu from 2000 to 2014. The yield of wheat seeded at the standard date (November 20) was 1) negatively correlated with precipitation in mid-December (beginning of tillering stage), 2) positively correlated with temperature in early-January (early tillering stage), 3) negatively correlated with temperature in late-February (terminal spikelet formation stage), and 4) negatively correlated with temperature in mid-May (late maturing stage). Precipitation in mid-December and temperature in mid-May showed a stronger negative correlation with the yield in lower yield areas, indicating that a combination of wet damage at the early growing stage and heat damage at the late maturing stage results in a significant yield reduction. Higher temperatures in early January increased spike number and hastened the time of spike formation stage which extended the duration to heading and increased the yield. Thus, we considered that wheat yield in Northern Kyushu as 1) effective field drainage before planting, 2) seeding after November 5 to 10 to avoid frost damage and to accelerate spike formations, 3) effective field drainage and topdressing in all growing stages to sustain plant activity. Further yield increase should be achieved by improvement of frost tolerance other than winter habit, utilization of wheat Vrs1 gene that increases grain number, and the improvement of dual tolerance to wet and heat damage in addition to the tolerance to pre-harvest sprouting and grain discoloration by rain.
We investigated the effects of plowing on growth and grain yield of maize (Zea mays L.) in an upland field converted from an andosol paddy field. A 2-year (2014 and 2015) field study with two hybrids and two tillage systems (rotary tilling and plowing) was conducted. Plowing reduced the time to silking by 1 or 2 days, whereas plant height, leaf color, and leaf area index were not significantly affected by the tillage system. Similarly, the tillage system did not significantly affect root length density; however, plowing of the fields increased root length density from the tassel formation stage to the milky stage. Additionally, plowing tended to increase dry weight at the milky and dough stages in 2014. In 2014, grain yield of the plants grown in plowed fields was higher than that of the plants grown in fields prepared by rotary tilling, while in 2015, there was no significant difference in grain yield between the two tillage systems. Since neither growth depression nor yield decline was observed in maize cultivated in plowed fields, it can be concluded that plowing is useful for maize production in upland field converted from andosol paddy fields.
The aim of this study was to clarify the method of soil management for “Toramame”, (tiger bean) a pole-type kidney bean with tiger-like stripes. We investigated the growth and root system of “Toramame”, and examined the correlation of yield with soil nitrogen level, and the depth of soil penetration resistance 1.5 MPa (effective depth of soil layer, EDS) in upland fields of Hokkaido Kitami district. Dry-matter production and nitrogen uptake rate were highest after the full bloom stage. The yield was positively correlated with autoclaving extractable nitrogen (ACN) level at 0–20 cm depth in andosol and upland soil. This suggested that when the amount of ACN increased, nitrate that could be assimilated by the crop after the bloom stage increased. The deeper the EDS at the full bloom stage within the range of 0 to 50 cm, the higher tended to be the yield. In the upland soil field where the yield was under 200 g m–2, where EDS was deep, the amount of ACN was less than 0.05 g kg–1. The yield on lowland soil tended to be lower than that on upland and andosols estimated from the amount of ACN, or EDS. Thus soil type and nitrate fertility affected the yield deeply and expanded EDS when the amount of ACN was larger than 0.05 g kg–1.
Four near-isogenic lines of Japanese soft wheat with different compositions of high-molecular-weight glutenin subunits, which are controlled by the Glu-A1 and Glu-D1 loci were cultivated with different amounts of nitrogen fertilizer applied at flowering time and the noodle quality was analyzed. In the line that carried both the null allele controlled by the Glu-A1 locus and subunits 2.2+12 controlled by the Glu-D1 locus, tensile force of the raw noodles (RN) and breaking force of the boiled noodles (BN) were weak, and deformation of BN was small, suggesting that RN became easier to break and BN had thinner appearance and softer texture. These results may have derived from the weak dough properties. Increased flour protein content brought weaker tensile force and larger deformation of the RN and stronger breaking force and larger deformation of BN. This shows that RN had better extensibility and BN had thicker appearance and harder texture. These results reflected the dough properties with high water absorption and inferior protein quality. Increased flour protein content also gave a darker flour color as reported before. These results suggest that to adjust appropriate grain protein content and not to have both the null allele controlled by the Glu-A1 locus and subunits 2.2+12 controlled by the Glu-D1 locus would be necessary to maintain good handling performance in noodle making and make the noodles with appropriate thickness, appropriate hardness and bright color.
Hot water disinfection method is a chemical-free agriculture technique which is gathering attention. It is conducted by immersing rice seeds in hot water at 60°C for 10 minutes. However, this condition is not always effective to prevent the occurrence of some seed-borne diseases. To establish and spread the use of this disinfection method, we need to introduce the heat tolerance trait to many cultivars and conduct the treatment under severer conditions. The heat tolerance varied with the rice cultivar. The seeds of “Hitomebore”, a Japonica rice cultivar subjected to hot water disinfection showed extremely strong heat resistance. On the other hands, the seeds of Indica and glutinous rice were relatively sensitive to heat. In the present study, to find a useful genetic resource, we analyzed the varietal difference in heat-stress tolerance during the hot water disinfection of rice varieties include in “NIAS world rice core collection”. The result showed that the seeds of two Japonica cultivars: “Rexmont” and “Tupa 729”, and an Indica cultivar: “Badari Dhan”, had extremely high heat-stress tolerance. In addition, we found that several Indica varieties including “Badari Dhan”, and glutinous rice cultivars had heat tolerance as strong as “Hitomebore”, and are useful as genetic resources to elucidate the gene responsible for heat-stress tolerance during hot water disinfection treatment.
To assess the risk of transfer of radiocesium from soil to brown rice on the soil with low exchangeable potassium (ExK2O) content, seedlings of rice cultivar "Tennotsubu" were transplanted to 500 cm2 Wagner pots filled with paddy soil collected from 21 sites in Fukushima prefecture, and grown to maturity without potassium fertilizer in 2015. ExK2O content of soil before and after cultivation, and radiocesium (137Cs) concentration of rough brown rice, straw and pot soil were measured to examine the effects of ExK2O content of soil on the transfer of radiocesium from soil to rough brown rice. ExK2O content of soil varied significantly with the site, and the contents at 12 sites were lower than 5 mg 100 g–1. The concentration of 137Cs in rough brown rice varied significantly with the site, in the range of 2.8 to 68.3 Bq kg–1. Transfer factors of 137Cs from soil to rough brown rice (ratio of 137Cs concentration in rough brown rice to that in the soil), obtained from this pot experiment, was markedly higher than those obtained in the field cultivation, because of the lower ExK2O content of soil in the pot. Moreover, the lower the ExK2O content of soil, the higher the ratio of 137Cs concentration in rough brown rice to that in straw, suggesting that 137Cs translocation to brown rice is enhanced by the decrease of potassium concentration in the rice shoot.
The number of farmers abandoning reclaimed farmland damaged by the tsunami following the Great East Japan earthquake has rapidly increased, and the few remaining farmers must manage substantial areas of reclaimed farmland by large scale farming. To develop a labor-saving cultivation technique to manage these fields, we investigated the suitability of two varieties of late-planted soybean, and appropriate row spacing, using a crop rotation system of rice–wheat–soybean every two years. Varieties “Akimiyabi”, a medium-maturing variety newly released in the Tōhoku Region; and “Tanrei”, an established, recommended variety were used. “Akimiyabi” had shorter and thicker stems than “Tanrei”, when planted in more narrow rows and high density. In addition, green stem disorder was reduced and harvest time was earlier in “Akimiyabi” than in “Tanrei”. The growth volume and yield were larger in “Akimiyabi” than in “Tanrei”. Seed protein content, inspection grade and seed size, were not influenced by row spacing within 24 cm to 36 cm, whereas the lodging in 24 cm row spacing was less than that in 36 cm row spacing. Our results suggest that “Akimiyabi” late planted at a high density with a row spacing of 24 cm is appropriate to obtain a stable high yield.
In the submerged direct-seeded rice cultivation, seedling establishment is important. For direct seeding, seeds are coated with chemicals such as calcium peroxide. The cost of the chemical is expensive and the coating labor is burdensome. A new seed coating method, “benmoly coating” was invented to lower the cost and burden. In this method, seeds are coated with a powdered mixture of molybdenum trioxide, iron oxide and polyvinyl alcohol. From 2013 to 2015, cultivation trials were conducted in 6 paddy fields in Saga Prefecture in Kyushu. Each paddy field had 2 experimental plots. In one plot, seeds were coated with calcium peroxide, and in another plot, seeds were benmoly-coated. Seeds were directly seeded by a shooting hill-seeder. The seedling establishment was good regardless of the coating method. There was no significant difference between the plots in the seedling establishment, growth, and yield of rice plants. Also there was no significant difference between the plots in molybdenum contents of the above-ground part, husked rice and soil after the cultivation. In the surrounding fields benmoly-coated seeds were cultivated and in these fields, the seedling establishments and yields were also good in general. Accordingly, benmoly coating could be useful in the submerged direct-seeded rice cultivation with a shooting hill-seeder in warm regions. It can save the cost and the labor for coating.
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