Oo Aung Zaw, Yamamoto Akinori, Ono Keisuke, Umamageswari Chellappan, Mano Masayoshi, Vanitha Koothan, Elayakumar Palanisamy, Matsuura Shoji, Bama Kaliappan Sathiya, Raju Marimuthu, Inubushi Kazuyuki, Sudo Shigeto, Saitoh Naoko, Hayashida Sachiko, Ravi Venkatachalam, Ambethgar Vellaisamy
Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan.
Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8604, Japan.
Sci Total Environ. 2023 Jan 1;854:158541. doi: 10.1016/j.scitotenv.2022.158541. Epub 2022 Sep 6.
The lowland tropical triple-cropping rice system has unique characteristics that affect the hydrological, nutrient, and atmospheric environments. To better understand the ecosystem carbon and water dynamics of a triple-cropping rice paddy from the perspective of sustainability, ecosystem-level CO flux and ecosystem water use efficiency (eWUE) were observed using eddy covariance over 2 years (2016-2018) at an experimental field site in southern India, and gross primary production (GPP) and ecosystem respiration (RE) were derived using the flux partitioning technique. Results showed that among the three crop seasons per year, GPP and RE were higher (887.2 and 570.2 g C m, respectively) in Thaladi (October-January: wet season) than in Kuruvai (June-September: dry season; 773.4 and 568.9 g C m, respectively) and summer rice (February-May; 694.0 and 499.7 g C m, respectively) owing to the longer growing season. Triple-cropping meant that the quasi-annual GPP of 2598 g C m (i.e., the total value for the three consecutive seasons, including the corresponding fallow periods) was much greater than the quasi-annual RE of 1974 g C m. Consequently, the net ecosystem production value was positive (624 g C m). Evapotranspiration was also high on the annual scale (1681 mm); that is, 48 % greater than mean annual precipitation (1139 mm). Analysis revealed that Thaladi had higher eWUE (2.21 g C (kg HO)) than that of Kuruvai (1.46 g C (kg HO)) and summer rice (1.57 g C (kg HO)) owing to decreased water loss in cloudy weather. Intense solar radiation is generally recognized as advantageous for crop growth in most regions, but not for Kuruvai and summer rice, when too strong solar radiation increases loss of water unused for photosynthesis. The findings indicate that water-saving techniques should be targeted on the Kuruvai and summer rice seasons.
低地热带三季稻系统具有影响水文、养分和大气环境的独特特征。为了从可持续性角度更好地理解三季稻田的生态系统碳和水动态，在印度南部的一个试验田站点，使用涡度相关技术在两年（2016 - 2018年）内观测了生态系统层面的CO通量和生态系统水分利用效率（eWUE），并使用通量分配技术得出了总初级生产力（GPP）和生态系统呼吸（RE）。结果表明，在每年的三个作物季节中，由于生长季节较长，塔拉迪季（10月至1月：湿季）的GPP和RE较高（分别为887.2和570.2 g C m），高于库鲁瓦伊季（6月至9月：干季；分别为773.4和568.9 g C m）和夏稻季（2月至5月；分别为694.0和499.7 g C m）。三季种植意味着2598 g C m的准年GPP（即包括相应休耕期在内的三个连续季节的总值）远大于1974 g C m的准年RE。因此，生态系统净产值为正（624 g C m）。年尺度上的蒸散量也很高（1681 mm）；即比年平均降水量（1139 mm）高48%。分析表明，由于多云天气下水分损失减少，塔拉迪季的eWUE（2.21 g C (kg H₂O)）高于库鲁瓦伊季（1.46 g C (kg H₂O)）和夏稻季（1.57 g C (kg H₂O)）。在大多数地区，强烈的太阳辐射通常被认为有利于作物生长，但对于库鲁瓦伊季和夏稻季并非如此，因为过强的太阳辐射会增加未用于光合作用的水分损失。研究结果表明，节水技术应针对库鲁瓦伊季和夏稻季。
