Nitrogen assimilation during seed filling limits the seed yield in soybean. Seed nitrogen dependence on either redistributed nitrogen or absorbed nitrogen from soil during seed filling shows varietal differences. The objective of this study was to investigate the timing of nitrogen enrichment for effective nitrogen assimilation. Two soybean cultivars Sachiyutaka and Tamahomare were sown in the pots filled with well-washed fine sand. The plants were well watered with nutrient solution containing 100 ppm nitrogen and other nutrient elements before and after the treatment. The treatments were conducted from reproductive stage R1 to R5 or from R5 to R7 by applying the nutrient solution with different nitrogen concentrations. The high nitrogen concentration from R1 to R5 delayed the decline in SPAD value and leaf nitrogen concentration and improved the seed yield performance in Sachiyutaka, whereas stimulated the decline in SPAD value and leaf nitrogen concentration and had no effect on seed yield in Tamahomare. However, high nitrogen concenntration during R5 to R7 delayed the decline in SPAD value and leaf nitrogen concentration and improved the yield performance more significantly in Tamahomare than in Sachiyutaka. The large seed yield increase by nitrogen enrichment during R5 to R7 in Tamahomare could be caused by both the high photosynthetic rate and vigorous nitrogen uptake during seed filling. These results suggested that the most effective timing of nitrogen enrichment during the reproductive growth period to increase seed yield varies with the cultivar due to the difference in the pattern of nitrogen assimilation.
Post-rainy season sorghum (Sorghum bicolor (L.) Moench) yields are often constrained by cold stress. Cold tolerance is a prerequisite for adaptation to post-rainy season. A study was conducted to develop a field screening technique for cold tolerance, and to identify traits that discriminate genotypes to cold response. A set of rainy and post-rainy season adapted sorghum genotypes were sown in 2010 – 2011 and 2011 – 2012 in 3 dates of sowing in post-rainy seasons from third week of October to second week of November. The average minimum temperature during a 30-day period after the initial 40-day vegetative growth was lower in October sowing, moderate in November sowing and high in December sowing. The panicle harvest index (PHI) was found to be sensitive to low temperatures and was identified as a stable trait for genetic discrimination. Reduction in PHI can be indicative of failure to set seed or poor grain filling. The genotypes bred for rainy season ICSB 52, ICSR 149 and ICSR 93034 exhibited reduced PHI and lighter seed in cold-prone environments, indicating that their sensitivity is also well reflected in the yields of ICSB 52 and ICSR 149. However, the genotypes bred for post-rainy season, Dagadi solapur, SPV 1411 and M 35-1, were not affected by cold, as indicted by their higher PHI and relatively less reduction in seed weight. It was suggested that PHI and seed weight together can be used as proxies in selecting for reproductive stage cold tolerance in sorghum.
Maintaining root function is crucial for favorable plant growth under flooding. The genetic variation in the response of root development to flooding is unclear, because measurement of root growth is time consuming, especially with numerous lines. To overcome the methodological problems and to reveal the effect of flooding on root development and its genetic variation, we developed a new capillary watering system without soil medium and raised cotyledon-stage seedlings of 92 soybean lines with and without flooding. After 7 days of flooding, dry weights (DW) and root characteristics were determined and the results were compared with those in non-flooded plants. The root DW decreased linearly with decreasing total root length and root surface area, and the degree of damage varied greatly among lines. Short-term flooding inhibited root elongation and branching, but not in flood-tolerant lines.
This study investigated the changes in the chemical properties of the plow soil during a 7-year period with yearly application of anaerobically-digested manure (ADM), and the effect of the different ADM application methods on nitrogen (N) uptake by rice plants and the apparent N balance (input N minus output N). Among the treatments significant differences were observed in the pH, total N, and available N in the plow soil. The cumulative N uptake by rice plants in the ADM split application plots was significantly higher than that in single application plots. Consequently, the apparent N balance (input N minus output N) in the single ADM application plots was more positive. This result suggests that split application of ADM is more favorable for N uptake by rice plants. Although the apparent N balance was negative in the plots without N fertilizer, with chemical N and with low ADM, there was no observable decline in the total N and available N in the plow soil. This result implies that input and output of N in these plots were well balanced by additional N supply other than fertilization. On the other hand, the apparent N balance during the 7-year study under standard and heavy application of ADM was positive, indicating the preservation of soil fertility.
Rice florets are susceptible to high-temperature damage at anthesis, but rice production remains stable in the Riverina region of Australia even when the air temperature during flowering exceeds 40ºC. To identify the mechanism that supports rice production under these conditions, we examined sterility and pollination in relation to microclimate and panicle temperature in an extremely hot paddy field in the Riverina region of New South Wales. In windy > 40ºC weather, the panicle temperature was > 38ºC at the windward edge of the crop but around 35ºC inside the crop, probably because of strong transpirational cooling due to the extremely dry wind (15% RH). Pollen from the windward edge of the crop showed extremely poor germination, yet that from inside the crop showed sufficient germination for fertilization. Moreover, sterility inside the crop was significantly lower than that at windward edge. We concluded that the wind with large vapor pressure deficit enabled stable rice production under the extreme heat during flowering.
Physical and chemical properties of vegetable oils and consequently their use, depend on the composition of fatty acids that accumulate in storage lipids during seed development. The objective of this study was to determine the combined effects of seed development stages and organic matter content of soil on oil fatty acid composition of canola. The experiments were carried out under field conditions on four soils with different organic matter contents. To evaluate seed oil content and fatty acid composition of canola, we harvested plants at six growth stages (GS), GS 75, GS 79, GS 83, GS 87, GS 92 and GS 99 including development of seed, ripening and senescence. The synthesis of oil and fatty acids were largely influenced by seed maturity and soil type. Seeds had maximum content of stearic and palmitic acids at GS 75 (50% of pods reach final size). The seed yield, oil content of seeds and oleic acid percentage of seed oil significantly increased with increasing rate of soil organic matter in canola. This study addresses the organic matter content in poor soils should be ameliorated not only to obtain higher crop yields but also quality production.
We evaluated how the cultivation of arbuscular mycorrhizal fungi (AMF) host (wheat) and non-host (rapeseed) crops affects the subsequent soybean crop by assessing AMF spore density and AMF colonization, phosphorus (P) uptake by soybean and yields of soybean over a 4-year period. Every year wheat or rapeseed was cultivated from autumn to spring and soybean from spring to autumn. From the first to fourth year, AMF spore density was higher in the plot after the cultivation of wheat (wheat plot) than in the rapeseed plot. From the second to fourth year, the AMF colonization ratio was higher in the wheat plot than in the rapeseed plot. In the first year, there was no difference in the AMF colonization ratio, growth, and P uptake by soybean plants between the rapeseed plot and wheat plot. However, from the second to fourth year, AMF colonization ratio, plant growth, and P uptake by soybean in the wheat plot were higher than those in the rapeseed plot. The soybean yields in both plots gradually decreased from the first to fourth year, but, in the second and the fourth year, soybean yields were higher in the wheat plot than in the rapeseed plot. Soybean yield was significantly correlated with the AMF colonization ratio, but not with AMF spore density. Therefore, we concluded that AMF colonization is not determined by AMF spore density alone, and other factors influence the AMF colonization in subsequent soybean plants. It is important to increase the AMF colonization ratio to increase soybean yield.
Jilin Province is a major spring maize area of China with the highest regional yield. Nevertheless, a large yield gap existed between actual and potential yield. A super-high yield (> 15 t ha–1) is needed to fulfil the increasing demand. However, yield has been limited due to the lack of knowledge on crop performance in relation to super-high yielding managements. Ten field experiments in Jilin Province from 2008 to 2011 were summarized to understand the growing process of high-yielding spring maize. Plants were categorized into high yield (HY) plants which had a yield > 12 t ha–1, medium yield (MY) plants which had a yield of 9 – 12 t ha–1, and low yield (LY) plants which had a yield < 9 t ha–1. Crop growth during vegetative stages showed no significant differences among yield categories. HY plants grew faster than LY and MY plants after the twelve-collar stage, and the difference became more and more pronounced during silking to 30 days after silking, and even afterwards. Moreover, HY plants had a shorter vegetative period than either LY or MY plants without impacts in vegetative growth, and longer reproductive period, which contributed to better kernel formation and filling. HY plants also had the capacity to maintain a high leaf area index (LAI) at 30 days after silking, which provided for a continuous dry matter accumulation during and after this period and thus resulted in a super-high yield. Hence, special attention should be paid during the 30 days after silking in order to maintain a high photosynthetic capacity and achieve a super-high yield.
Two-striped leaf beetle (TSLB) larvae are known to damage soybean root nodules but the effect they have on yield has not been quantitatively assessed. This study was aimed to evaluate the impact of TSLB and to establish a technique to control the larvae. We surveyed 106 farmers’ fields in Aichi prefecture for two years to quantify the changes in TSLB adult population, nodule damage by larvae, and nitrogen (N) content of seeds and stems, growth and yields of soybean plants treated with two different pesticides that were applied to furrow at the time of seeding. The results showed that damage caused by TSLB larval feeding of root nodules was observed particularly in soybeans grown in N-poor soil, and that ureide N content was decreased in plants with damage caused by larval feeding of root nodule, and such damage caused reduction of yield consistently in both years. Furthermore, we also showed the effectiveness of applying insecticides to the sowing furrow at the time of seeding. Specifically, the application of disulfoton to the sowing furrow at a rate of 4 g m–2 as a simple method of pest control limited insect occurrences until the beginning of the blooming stage, curbed the feeding damage to root nodules caused by larvae, and increased the yield of soybean by 20%. This method has been adopted widely in Japan because it can be readily implemented using the fertilization application equipment installed on seeding machines and the insecticide is relatively inexpensive.
Regarding the article Vol. 15(2): 132-143, 2012. Shimada et al. “Effects of Water Table Control by Farm-oriented Enhancing Aquatic System on Photosynthesis, Nodule Nitrogen Fixation, and Yield of Soybeans”. We would like to have errata here with apology.
Correction On p. 133, the third and fourth lines of the right column are incorrect. They should be as follows: “Three FOEASs were installed in a paddy field (2100 m2), having an impermeable bottom at approximately 60 cm depth, located at the National Institute of Agro-Engineering (36ºN, 140ºE). On p. 142, between the tenth and eleventh lines above the final line of the left column, the following sentence should be inserted. “As we did the research in an experimental field having a bottom, further research is needed to verify the effect of FOEAS on farmer's fields.”
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