Article

Root-zone salinity. II. Indices for tolerance in agricultural crops.

Crop Science (Impact Factor: 1.48). 10/2005; 45:221-232.
Source: OAI

ABSTRACT This paper provides the tools for distinguishing levels of tolerance to root-zone salinity in agricultural crops. Such distinction rests on the response of a crop's product yield following the declining, sigmoid-shaped, modified compound-discount function (Y(r) = 1/1 + (C/C50)exp(sC50)) for plants grown as crops exposed to increasing root-zone salinity. This nonlinear function relates relative yield (Y(r)) to root-zone salinity (C) measured in equivalent saturated soil-paste extract electrical conductivity with two nonlinear parameters, the salinity level producing 50% of the nonsaline crop yield (C50) and a response curve steepness constant (s) equal to the absolute value of the mean dY(r)/dC from Y(r) = 0.3 to 0.7. These discount parameters suggest the existence of a single-value salinity tolerance index (ST-Index) equal to the 50% reduction in crop yield from that of the nonsaline yield plus a tendency to maintain some product yield as the crop is subjected to salinity levels approaching C50, i.e., ST-Index = C50 + s(C50). The explicit purpose of this study is to determine if the discount function using biophysically relevant parameters can be applied to historical data sets. Approximations for C50 and s were identified in the threshold salinity (C(t)) and declining slope (b) parameters of the well-known threshold-slope linear response function. Several procedures for converting C(t) to C50 and b to s offer the linkage between these linear and nonlinear response functions. From these procedures, two regression equations, C50 = 0.988(0.5/b) + C(t) - 0.252 and s = 1.52b, proved the most appropriate for the eight representative field, forage, and vegetable crops tested. The selected conversion procedures were applied to previously published C(t) and b values to obtain a list of the relative root-zone salinity tolerance in agricultural crops. In addition to C50 and s, values for exp(sC50) and the ST-Index were computed for each crop. The revised list provides extension personnel and plant growth modelers the parameter values from a nonlinear analog of crop yield response to root-zone salinity.

0 Bookmarks
 · 
165 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Field experiments were conducted in arid Southern Xinjiang, Northwest China, for 3 years to evaluate sustainable irrigation regimes for cotton. The experiments involved mulched drip irrigation during the growing season and flood irrigation afterward. The drip irrigation experiments included control experiments, experiments with deficit irrigation during one crop growth stage, and alternative irrigation schemes in which freshwater was used during one growth stage and relatively saline water in the others. The average cotton yield over 3 years varied between 3,575 and 5,095 kg/ha, and the irrigation water productivity between 0.91 and 1.16 kg/m3. Crop sensitivities to water stress during the different growth stages ranged from early flowering-belling (most sensitive) > seedling > budding > late flowering-belling (least sensitive), while sensitivities to salt stress ranged from late flowering-belling > budding > seedling > early flowering-belling. Although mulched drip irrigation during the growing season caused an increase in salinity in the root zone, flood irrigation after harvesting leached the accumulated salts to below background levels. Numerical simulations, based on the 3-year experiments and extended by another 20 years, suggest that mulched drip irrigation using alternatively fresh and brackish water during the growing season and flood irrigation with freshwater after harvesting is a sustainable irrigation practice that should not lead to soil salinization.
    Irrigation Science 01/2014; · 2.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Kochia species has recently attracted the attention of researchers as a forage and fodder crop in marginal lands worldwide. Kochia is drought and salt tolerant and native to Iran. This plant has a potential to grow in saline soils and it can be irrigated with brackish water. To evaluate how salinity stress affects growth parameters, an experiment was conducted wherein plants of Kochia scoparia were exposed to six levels of saline waters (1.5, 7, 14, 21, 28 and 35 dS/m). The function method was used for evaluating growth parameters. The results showed that all growth parameters decreased with increasing salinity higher than 7 dS/m. Kochia scoparia is a meso-halophyte, thus low salt stress (7 dS/m) improved its dry matter production and leaf area index (LAI). Stem dry weight (SDW) and plant dry weight (PDW) decreased significantly under salt stress, but the salt induced reduction in plant dry weight (PDW) was more than that in the former growth attribute. However, while salt stress improved leaf weight ratio (LWR) in K. scoparia. Salinity affected Kochia leaf morphology and increased leaf thickness. Fifty percent yield reduction occurred at 38.8 dS/m salinity. In view of the growth performance of this species under saline conditions, this plant shows a high potential to sustain under irrigation with saline water in summer when good quality water is usually scarce.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A variety of analytical and numerical models have been developed during the past several decades to predict water and solute transfer processes between the soil surface and the groundwater table. While many models quantifying solute transport in soils usually consider only one solute and severely simplify various chemical interactions, others such as the geochemical module of HYDRUS-1D consider multiple solutes and their mutual interactions. In this study we use HYDRUS-1D to analyze water flow and solute transport in three soil lysimeters (1.2 m2 × 1 m) irrigated during the summer months with waters of different quality that were used to evaluate salinization and alkalization hazards. The soil monoliths were constructed in a Eutric Fluvisol in Alentejo, Portugal. The electrical conductivity (EC) of irrigation water varied between 0.4 and 3.2 dS m−1, and the sodium adsorption ratio (SAR) varied between 1 and 6 (mmol(c) L−1)0.5, while maintaining a ratio of Ca:Mg equal to 1:2. The soil monoliths were subjected to regular rainfall and leaching during the rest of the year. Water contents and fluxes, concentrations of individual ions (Na+, Ca2+, and Mg2+), electrical conductivity of the soil solution, SAR, and exchangeable sodium percentage (ESP) indices were monitored from May 2001 to September 2004 at four depths (10, 30, 50, and 70 cm) in all three soil monoliths. Irrigation water with EC up to 1.6 dS m−1 did not cause salinization or alkalization hazards. The rainfall water leached the salts accumulated during the irrigation period down to a depth of 100 cm. Rainfall, however, did not restore the salinity and sodicity of the soil to its original values below a depth of 60 cm for the lysimeter irrigated with water having an EC equal to 3.2 dS m−1. HYDRUS-1D successfully described field measurements of the water content (R2 = 0.60), overall salinity (R2 = 0.65), and the concentration of individual soluble cations (R2 ranged between 0.62 and 0.78) as well as the sodium adsorption ratio (R2 = 0.87) and the exchangeable sodium percentage (R2 = 0.76).
    Water Resources Research 01/2006; W08401. · 3.71 Impact Factor

Full-text (3 Sources)

Download
126 Downloads
Available from
May 30, 2014