A Macroscopic Water Extraction Model for Nonuniform Transient Salinity and Water Stress

Abstract

Quantitative description of root‐water uptake under combined salinity and water stress is needed to optimize crop yields and water management in arid and semiarid regions. This study was conducted to develop a simple macroscopic root‐water uptake model for nonuniform transient soil water content and salinity conditions in the root zone. This new model and previous models were tested against detailed experimental data obtained with Alfalfa (Medicago sativa L.) grown in the greenhouse in packed sandy loam (Typic Haplaquent) columns. Soil water content, pressure head, and osmotic head distributions in the root zone were varied by means of the amounts, application intervals, and salinities of the irrigation water. Experimental data under separate and combined stresses were used to test the various models using mean values of soil solution osmotic and pressure heads. The simple additive reduction function provided the worst agreement with the experimental data, while for most cases the multiplicative reduction functions could not adequately account for both water and salinity stress conditions. The newly proposed linear reduction function is neither additive nor multiplicative, but was assumed that both the intersect and slope of the reduction function increased with salinity. This model provided excellent agreement with the experimental data, particularly at higher soil solution salinities. The new reduction function could be used with any other nonlinear salinity reduction function.

Evaluation of water movement and water losses in a direct-seeded-rice field experiment using Hydrus-1D

“…The method to consider water stress was used to determine root water uptake. Parameter values optimized by Singh et al (2003) for rice crops (h 1 = 100 cm, h 2 = 55 cm, h 3 (high) = −160 cm, h 3 (low) = −250 cm, and h 4 = −15,000 cm) were used to parameterize the water stress response function proposed by Feddes et al (1978) and Homaee et al (2002). Parameters h 1 through h 4 represent different pressure head values, which affect root water uptake in the soil.…”

Tolerance of canola to drought and salinity stresses in terms of root water uptake model parameters

“…Combined water and salinity stresses have been proposed in macroscopic RWU models (Feddes and Raats, 2004;Homaee et al, 2002). To express the reduction of the water uptake rate under the coexistence of drought and osmotic stresses, we employed an additive form:…”

Interactive effect of salinity and two nitrogen fertilizers on growth and composition of sorghum

“…Halophytes grown in highly saline and N-deficient environments and glycophytes grown in mildly saline and N-deficient environments respond similarly to added N (Okusanya and Ungar 1984). Some studies also indicate that corn and cotton dry matter decreased by increasing salinity but increases by N application (Homaee et al 2002).…”

“…However, this depends on the type of nutrients and composition of soil solution (Grattan and Grieve 1999, Maas and Grattan 1999, Homaee et al 2002. Although plants selectively absorb potassium over sodium, Na + -induced K + deficiency can develop on crops under salinity stress by Na + salt (Maas and Grattan 1999).…”