Potassium fertilization and irrigation with treated wastewater on gas exchange of colored cotton

ABSTRACT The use of treated domestic wastewater in agriculture is promising because it contains essential nutrients for crops, especially for cotton plants. Information on leaf gas exchanges helps to understand the responses of plants to different water and nutrient managements, since they directly affect physiological processes. Thus, the objective of this study was to evaluate the effect of potassium fertilization and irrigation with treated wastewater on the gas exchange of naturally colored cotton plants grown in the semi-arid region of the state of Pernambuco, Brazil, providing a reference for evaluations of responses of cotton plants to abiotic factors. The experiment was conducted in a randomized block design, in a 5 × 5 factorial arrangement, with four replications. The treatments consisted of five potassium rates (0, 50, 100, 150, and 200% of the recommended rate for the crop) and five irrigation depths (50, 75, 100, 125, and 150% of the evapotranspiration of the crop). The highest stomatal conductance, transpiration, net assimilation rate, intercellular CO2 concentration, and carboxylation efficiency were found in irrigated plants with 110, 99, 117, 150, and 113% of ETc, combined with the potassium rates of 96, 113, 97, 100, and 100% of the recommendation rate for the crop, respectively. The increase in irrigation depths increased the diffusion of CO2 of the plants. The highest instantaneous water-use efficiency was found with the irrigation of 150% of ETc without potassium fertilization. According to the interaction between irrigation depths and potassium rates, the most efficient potassium rate for naturally colored cotton depends on the irrigation depth applied.

摘要 经处理的生活污水用于农业生产具备可观应用前景，因其含有作物生长必需的营养元素，对棉花作物尤为关键。叶片气体交换相关数据有助于解析植物对不同水肥管理措施的响应，因气体交换直接调控植物生理过程。因此，本研究旨在评估钾肥配施与再生生活污水灌溉对巴西伯南布哥州半干旱地区种植的天然彩色棉植株气体交换特性的影响，为解析棉花植株对非生物因子的响应提供参考依据。本实验采用随机区组设计，设置5×5因子试验方案，共4次重复。试验处理包含5个钾肥施用量水平（分别为作物推荐施用量的0、50、100、150、200%）以及5个灌溉水深水平（分别为作物蒸散量（evapotranspiration of the crop，简称ETc）的50%、75%、100%、125%、150%）。当灌溉水深分别为ETc的110%、99%、117%、150%、113%，且钾肥施用量分别为作物推荐施用量的96%、113%、97%、100%、100%时，植株的气孔导度、蒸腾速率、净同化速率、胞间CO₂浓度以及羧化效率均达到最高水平。提高灌溉水深可增强植株的CO₂扩散能力。当灌溉水深为ETc的150%且不施钾肥时，植株的瞬时水分利用效率达到峰值。结合灌溉水深与钾肥施用量的交互作用可知，天然彩色棉的最优钾肥施用量取决于所采用的灌溉水深。