Proposing a crop-water-salt production function based on plant response to stem water potential
Xianbo Zhang, Hui Yang, Manoj K. Shukla, Taisheng Du
Abstract
Prediction of crop yield under water and salt stress is essential for guiding deficit irrigation in saline soil. The responses of tomato plants to water and salt stress, and their interactions have profound effect on yield. Traditional crop-water-salt production functions do not fully account for the physiological response of plants to all stresses, especially the response to the interaction of soil salinity and water deficit. We developed a static crop water and salt production function based on the traditional water and salt production function, combined with the interaction between water deficit and soil salinity and the specific effects of soil salinity, based on a statistical model. This research involves measurement of plant pre-dawn stem water potential (ψs), osmotic potential (ψπ), leaf turgor (ψp), relative leaf water content (RWC), net photosynthesis (Pn), stomatal conductance (Gs) and transpiration (Tr), and the responses of these physiological parameters to four water deficit treatments or four salt salinity treatments as well as combined water deficit and soil salinity. The correlation analysis of physiological parameters showed that the pre-dawn stem water potential of plant was closely correlated with ψπ, ψp, RWC, Pn, Gs and Tr. The variations of physiological parameters with plant stem water potential were different under different soil salinity levels. We used the pre-dawn plant stem water potential as a unified indicator to characterize water deficit, soil salinity and combined water deficit and soil salinity. When predicting yield by stem water potential, we quantified the difference between the responses of the physiological parameters to the reduction of pre-dawn stem water potential under salt stress, combined water deficit and soil salinity and that under water stress. To improve the applicability of the function, we established quantitative relationships between soil volumetric water content, conductivity of saturated extract, and predawn stem water potential. Finally, we established a new crop-water-salt production function that takes the rhizosphere soil water content and electrical conductivity as the input, and considers the interaction between water deficit and soil salinity and the effect of ion accumulation. Compared with other crop-water-salt production function models, the new model has higher simulation accuracy and easier data acquisition, which is conducive to application in greenhouse crop water and salt management.