Quantification of Leaf Growth, Height Increase, and Compensatory Root Water Uptake of Sunflower in Heterogeneous Saline Soils

Abstract

Core Ideas Compensatory growth and root water uptake are observed in heterogeneous saline soils. Three types of indexes are proposed to determine the heterogeneous water and salt stresses. Critical compensation factors for each growth stages of sunflower are determined and linked with heterogeneous soil water and salt. ABSTRACTTo characterize the crop growth and root water uptake (RWU) under heterogeneous soil water and salt (SWS) conditions, 2‐yr subplot experiments with sunflower (Helianthus annuus L.) were conducted at the Yichang experimental station in the Hetao Irrigation District (HID), China. Three types of stress indices, including average (αmean, ω), positional (αupper, αdeeper), and extreme (αsmax, αsmin) indices, were defined to quantify the heterogeneity of the SWS stresses at each growth stage of sunflower. The relative increase in the leaf area index (REDLAI) and height (REDH) of sunflower were quantified based on correlation analyses with SWS heterogeneity indices. The critical compensation factor (ωc) of RWU at different sunflower growth stages was inversely calculated based on the Feddes Jarvis (FJ) model and quantified using a defined soil environmental stress factor (δ). The results showed that the vertical heterogeneity of SWS gradually improved and that soil stress indices varied with sunflower growth. The relatively high correlations of REDLAI and REDH with the ω (average stress coefficient weighted by the root length density) were determined, and quantitative relationships of the REDLAI and REDH with the ω at different growth stages were established. Furthermore, relatively high coefficient of determination (R2) values of quantitative relationships between ωc and δ were acquired (0.75, 0.78, 0.64, and 0.46 at the seedling, budding, flowering, and maturity stages, respectively). The proposed methods could improve the prediction of crop leaf growth, height development, and compensatory root water uptake (CRWU) based on SWS information in salt‐affected regions.