Field sugarcane transpiration based on sap flow measurements and root water uptake simulations: Case study on Tanegashima Island, Japan
Field sugarcane transpiration based on sap flow measurements and root water uptake simulations: Case study on Tanegashima Island, Japan
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DOI：
10.1016/j.agwat.2021.106836
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发表时间：
2021-05
影响因子：
6.7
通讯作者：
K. Momii;Hiroki Hiyama;S. Takeuchi
中科院分区：
文献类型：
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作者：
K. Momii;Hiroki Hiyama;S. Takeuchi
在农业中，土壤蒸发被认为是水分的损失，而作物蒸腾是影响作物生长和产量的关键因素。尽管已有大量的农田蒸散研究，但由于田间条件下作物蒸腾的直接测定和蒸发与蒸腾的单独评价存在困难，对田间作物蒸腾的研究很少。在本研究中，我们使用热脉冲法测量甘蔗茎的液流速度，以评估夏季在日本种子岛（约31° N）的研究地点的田间蒸腾。参考作物蒸散量是由联合国粮食及农业组织（FAO）的Penman-Monteith方法从现场气象数据确定的，并与实测蒸腾量进行了比较。8月份的日蒸腾量为3.3 mm d-1 ~ 6.6 mm d-1，相应的液流为0.27 L d-1 ~ 0.55 L d-1/茎。对蒸散量的逐日分析表明，粮农组织提出的作物系数标准值1.25可作为研究区甘蔗生长中期的作物系数。采用引入汇项的理查兹方程，对8月份连续20个晴天和干旱日的根系吸水量对大气蒸腾需求的响应进行了数值模拟。根区土壤水分的减少主要取决于白天的蒸腾需求，而土壤水分的再分配和恢复主要是在夜间进行。8月份的每小时数值结果支持粮农组织提出的在季中生长阶段基础作物系数的标准值1.20。模拟结果表明，根系优先从深层和湿润土层中汲取水分以满足蒸腾需求;由汇项预测的蒸腾量与热脉冲法实测的蒸腾量吻合较好。因此，基于参考作物蒸散量的大气蒸腾需求下土壤水分动态的数值分析可以作为甘蔗田间耗水量估算的有效工具。
In agriculture, soil evaporation is considered a loss of water, and crop transpiration is a crucial factor affecting crop growth and yield. Although there have been numerous studies on evapotranspiration (ET) on farmland, only a few have been conducted on field crop transpiration because of the difficulties in the direct measurement of transpiration and in separate evaluation of evaporation and transpiration under field conditions. In this study, we used the heat-pulse method to measure the sap velocity in sugarcane stems to evaluate field transpiration during summer at the study site on Tanegashima Island (at about 31° N) in Japan. The reference crop ET was determined by the Food and Agriculture Organization (FAO) Penman–Monteith method from on-site meteorological data and was compared with the measured transpiration. The daily transpiration in August ranged from 3.3 mm d−1to 6.6 mm d−1; the corresponding sap flow varied from 0.27 L d−1to 0.55 L d−1per stalk. The daily analysis of ET showed that a standard value of 1.25 for the crop coefficient presented by the FAO is acceptable as the crop coefficient for the mid-season growth stage of sugarcane in the study site. Numerical simulations of Richards equation with the sink term were conducted to examine the response of root water uptake to atmospheric transpiration demand throughout 20 consecutive clear and dry days in August. The decrease in the soil moisture in the root zone depends on the transpiration demand during daytime, and soil moisture is redistributed and recovered during the nighttime. The hourly numerical results in August support a standard value of 1.20 for the basal crop coefficient in the mid-season growth stage, as proposed by FAO. The simulations showed that roots extract water preferentially from the deep and wet soil layers to meet the transpiration demand; transpiration predicted from the sink term agreed well with the actual transpiration measured by the heat-pulse method. Therefore, the numerical analysis of soil moisture dynamics under the atmospheric transpiration demand based on the reference crop ET can be an effective tool to evaluate field sugarcane water consumption.