ABSTRACT

Field experiments were carried out for 3 years to assess the effect of using drip irrigation on the growth and yield of two Japanese soybean cultivars in Kagawa Prefecture, which has the second-lowest rainfall in Japan. The treatments were drip irrigation (Drip) and rainfed (Rainfed) from the blooming stage to the full-seed stage. The largest seed yield was achieved in 2017, followed by 2018 and 2016. This order corresponded to the total water input (TWI, the sum of effective rainfall and irrigation) throughout cultivation. TWI was the main factor affecting the variation of yield and its components among years. Similarly, the higher TWI in Drip than in Rainfed contributed to the higher yield in Drip than in Rainfed within each year. ANOVA detected a significant effect of drip irrigation on total seed yield, above-ground dry matter (AGDM) at maturity, and numbers of branches, nodes, and fertile pods. AGDM had a significant correlation with the mean crop growth rate (CGR) during the treatment, and CGR was closely correlated with the mean net assimilation rate (NAR). Significant positive correlation among NAR, radiation use efficiency, and leaf water potential suggested that drip irrigation prevented the decrease of plant water status that contributed to maintain dry matter production. The advantage of using drip irrigation for soybean cultivation at the experiment site would be suppressing the decrease in yield in years with low rainfall rather than achieving higher yield than standard in years with normal or high rainfall.

Abbreviations: AGDM, aboveground dry matter; CGR, crop growth rate; CISR, cumulative intercepted solar radiation; DAS, days after sowing; ETa, actual evapotranspiration; ETr, reference evapotranspiration; FIPAR, fraction of intercepted photosynthetically active radiation; LAI, leaf area index; Ψ_L, leaf water potential; mLAI, mean leaf area index; NAR, net assimilation rate; PAR, photosynthetically active radiation; PCC, percent of canopy coverage; RUE, radiation use efficiency; TWI, total water input

摘要

在日本降雨量第二低的香川县，进行了为期 3 年的田间试验，以评估使用滴灌对两个日本大豆品种的生长和产量的影响。开花期至满粒期采用滴灌（Drip）和雨育（Rainfed）两种处理方式。2017 年种子产量最高，其次是 2018 年和 2016 年。 该顺序对应于整个栽培过程中的总水输入（TWI，有效降雨和灌溉的总和）。TWI是影响产量及其组成部分年间变化的主要因素。同样，滴灌中的 TWI 高于雨育中的 TWI，导致每年滴灌的产量高于雨育。方差分析检测到滴灌对种子总产量的显着影响，成熟时的地上干物质 (AGDM)，以及分枝、节和可育豆荚的数量。AGDM与处理期间的平均作物生长率（CGR）有显着相关性，CGR与平均净同化率（NAR）密切相关。NAR、辐射利用效率和叶水势之间的显着正相关表明，滴灌防止了有助于维持干物质生产的植物水分状况的下降。在试验地进行大豆种植滴灌的优点是抑制了低降雨年份的产量下降，而不是在正常或高降雨年份实现高于标准的产量。AGDM与处理期间的平均作物生长率（CGR）有显着相关性，CGR与平均净同化率（NAR）密切相关。NAR、辐射利用效率和叶水势之间的显着正相关表明，滴灌防止了有助于维持干物质生产的植物水分状况的下降。在试验地进行大豆种植滴灌的优点是抑制了低降雨年份的产量下降，而不是在正常或高降雨年份实现高于标准的产量。AGDM与处理期间的平均作物生长率（CGR）有显着相关性，CGR与平均净同化率（NAR）密切相关。NAR、辐射利用效率和叶水势之间的显着正相关表明，滴灌防止了有助于维持干物质生产的植物水分状况的下降。在试验地进行大豆种植滴灌的优点是抑制了低降雨年份的产量下降，而不是在正常或高降雨年份实现高于标准的产量。和叶水势表明滴灌防止了有助于维持干物质生产的植物水分状况的下降。在试验地进行大豆种植滴灌的优点是抑制了低降雨年份的产量下降，而不是在正常或高降雨年份实现高于标准的产量。和叶水势表明滴灌防止了有助于维持干物质生产的植物水分状况的下降。在试验地进行大豆种植滴灌的优点是抑制了低降雨年份的产量下降，而不是在正常或高降雨年份实现高于标准的产量。

缩写：AGDM，地上干物质；CGR，作物生长率；CISR，累积截获的太阳辐射；DAS，播种后的天数；ETa，实际蒸散量；ETr，参考蒸发量；FIPAR，截获的光合有效辐射的分数；LAI，叶面积指数；Ψ _L，叶水势；mLAI，平均叶面积指数；NAR，净同化率；PAR，光合有效辐射；PCC，冠层覆盖百分比；RUE，辐射利用效率；TWI，总进水量