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.

Full-text

Available from: Martinus Th. Van Genuchten, May 29, 2015
1 Follower
 · 
206 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study has investigated the possibility for monitoring simultaneously and continuously the relationship between the macroscopic crop response and the evolution of water content, electrical conductivity and root density along the soil profile during the whole growing season of a tomato crop under different salinity treatments. Water storages measured by TDR sensors were used for calculating directly the actual water uptake by the root system along the whole soil profile under the different salinity levels imposed during the experiments. It was observed that during irrigation with saline water the salt content increased along the whole profile but that it tended to accumulate quite uniformly below the 20 cm in the case of the 4 dSm-1 treatment and at depth between 15 and 25 cm in the case of the 8dSm-1 salinity treatment. Compared to the reference freshwater treatment, the evapotranspiration under salinity treatments started to decrease at a threshold value of the time-depth average electrical conductivity (EC) of soil water of about 3dSm-1. Based on the results of soil and plant monitoring, the root uptake process was simulated by using a model for water and solute flow in the soil-plant-atmosphere continuum. This way, the root activity reduction at each depth-node was calculated as a function of the salinity (and eventually water) stress. This enabled relating the distribution of higher/lower activity of root uptake along the soil profile in response to the actual distribution of salts.
    12/2013; 19. DOI:10.1016/j.proenv.2013.06.073
  • [Show abstract] [Hide abstract]
    ABSTRACT: Agricultural water management in arid and semi-arid regions largely depends on availability and quality of irrigation water at different plant growth stages. In saline environments, plant response to salinity varies at different growth stages. Information on plant response to salinity at various growth stages can be used in managing saline waters for irrigation. This study was conducted to quantitatively assess response of sorghum (Sorghum bicolor L. Moench) to salinity at seedling stage. Consequently, an extensive experiment in natural saline sandy loam soil with five natural saline water treatments including 4, 6, 8, 10, and 12 dS/m was conducted. The reason for selecting natural sources of saline water and a saline soil was to minimize deviations from natural conditions under which sorghum grows. Sorghum seeds were planted and seedles counted at 24 h time intervals. The macroscopic models of Maas and Hoffman, van Genuchten and Hoffman, Dirksen et al., and Homaee et al. were used to predict relative seedlings at different salinity levels. The obtained results indicated that salinity threshold value EC* for sorghum at seedling stage is 1 dS/m and the seedling rate reduces to 50 percent at 11 dS/m of soil salinity. All evaluated models overestimated the EC* value. Calculated statistics indicated that the nonlinear salinity models are more accurate than the linear model. Among those, Homaee et al. model provided better predictions at seedling growth stage.
    Agricultural Water Management 04/2015; 152. DOI:10.1016/j.agwat.2015.01.008 · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The information on salinity threshold levels for food legumes when irrigating with saline water is limited and old. In a multi-year study at two sites in the Euphrates Basin, we aimed at (i) evaluating the potential of saline water irrigation for chickpea, faba bean and lentil production; and (ii) using the SALTMED model to determine threshold crop yields based on irrigation water salinity in equilibrium with ambient soil solution salinity. To evaluate 15 accessions each of lentil and chickpea, and 11 accessions of faba bean, three irrigation treatments were used with salinity levels of 0.87, 2.50 and 3.78 dS m-1 at Hassake and 0.70, 3.0 and 5.0 dS m-1 at Raqqa. Aggregated grain yields showed significant differences (p < 0.05) among crop accessions. Calibration and validation of the SALTMED model revealed a close relationship between actual grain yields from the field sites and those predicted by the model. The 50% yield reduction (π50 value) in chickpea, lentil, and faba bean occurred at salinity levels of 4.2, 4.4 and 5.2 dS m-1, respectively. These results suggest that of the three food legume crops, faba bean can withstand relatively high levels of irrigation water salinity, followed by lentil and chickpea. Copyright © 2015 John Wiley & Sons, Ltd.RésuméLes informations sur les seuils de salinité pour les légumineuses alimentaires irriguées avec de l'eau saline sont limitées et anciennes. Dans une étude pluriannuelle sur deux sites dans le bassin de l'Euphrate, nous avons cherché à (i) évaluer le potentiel de l'irrigation de l'eau salée pour le pois chiche, la féverole, les lentilles; et à (ii), déterminer les rendements des cultures influencés par de l'eau saline en équilibre avec la solution du sol ambiante, en utilisant le modèle SALTMED. Nous avons évalué 15 rangées de lentilles et de pois chiches, et 11 de féves avec trois traitements d'irrigation de salinité de 0.87, 2.50 et 3.78 dS m-1 à Hassake, et de 0.70, 3.0 et 5.0 dS m-1 à Raqqa. Les rendements en grains ont montré des différences significatives (p < 0.05) dans les différents traitements. Le calibrage et la validation du modèle SALTMED ont révélé la relation étroite entre les rendements réels en grains et les prédictions du modèle. La réduction de rendement de 50% (valeur π50) pour les pois chiches, les lentilles et la féverole se produit à des niveaux de salinité de 4.2, 4.4 et 5.2 dS m-1, respectivement. Ces résultats suggèrent que parmi les trois cultures de légumineuses alimentaires, la féve peut résister à des niveaux relativement élevés de salinité de l'eau d'irrigation, suivie par les lentilles et les pois chiches. Copyright © 2015 John Wiley & Sons, Ltd.
    Irrigation and Drainage 03/2015; DOI:10.1002/ird.1912 · 0.72 Impact Factor