Salt Concentration In Irrigation Water Research Articles

Salinity and irrigation method affect crop yield and soil quality in watermelon (Citrullus lanatus L.) growing

AbstractThe experiment was set up in the Neretva River Valley in southern Croatia, with the aim to determine the influence of increasing salt concentrations in irrigation water using different irrigation systems (sprinkler and drip) in watermelon production on plastic mulch. Saline drip irrigation reduced the development of salinized plants. Under drip irrigation, salinity did not cause plant mortality, but it led to a reduction in the number and length of vines. Saline sprinkler irrigation caused plant mortality. Soil solution ion composition was remarkably altered by saline drip irrigation. Saline irrigation also had detrimental effects on yield. Application of saline water rapidly changed the ion composition of soil solution. Significant changes in Ca, Na and Cl concentrations in soil solution were determined parallel to increasing the irrigation water salinity, whereas changes in Mg and K concentrations were not statistically significant. Marketable yield was reduced by salinity. Saline drip irrigation had detrimental effects on yield (26 and 35% yield reduction). In the trial treatment involving saline sprinkler irrigation, plants were completely damaged and no yield was attained. Copyright © 2008 John Wiley & Sons, Ltd.

A Comparison of Subcanopy Versus Overhead Application of Constructed Wetland Treated Nursery Runoff on Short and Long Rotation Nursery Crops

Abstract The nursery/greenhouse industry is the fastest growing segment of U.S. agriculture. Consumer demand for excellent product quality requires luxury applications of water and agricultural chemicals. These cultural practices tend to yield significant volumes of runoff rich in nutrients and pesticides. A capture and recycle system at the Nursery/Floral Crops Research and Education Center at Texas A&M University was fitted with 12 gravel filtration sub-surface flow (SSF) and 12 bog-like free-surface flow (FSF) wetland cells. Three cells of each type were planted with Canna x generalis Bailey ‘Cherry Red’, Iris L. x ‘Clyde Redmond’, both species, or no wetland plants. Runoff was continually collected from the nursery and recycled through wetland cells prior to application via overhead impact sprinklers or subcanopy microsprinklers. Short-term (10 wk) differential effects between overhead and subcanopy irrigation during production of Fraxinus pennsylvanica, Pistacia chinensis von Bunge, Quercus virginiana P. Miller, and Taxodium distichum (L.) Richard in 9.4 liter (#3) containers or Ilex vomitoria W. Aiton ‘Nana’ and Catharanthus roseus G. Don in 5.8 liter (#2) containers were limited in magnitude. However, overhead irrigation reduced height and caliper growth or injured the foliage compared to plants irrigated with subcanopy microsprinklers during longer-term (14 months) production in large 87.9 liter (#27) containers. The extent of reduction was species dependent with Pinus elliottii Englemann being minimally impacted, Pyrus calleryana Descaisne ‘Bradford’ intermediate, and Lagerstroemia L. x ‘Basham's Party Pink’ (purportedly a Lagerstroemia indica L. x Lagerstroemia fauriei B. Koehne hybrid) and T. distichum exhibiting more pronounced effects. Damage appeared to be largely a result of high dissolved salt concentrations in irrigation water contacting the foliage. Recycling of runoff through the FSF cells concentrated soluble salts more so than passing the water through the SSF cells. Efficacy of nitrate nitrogen removal varied with species, season, loading rate, and wetland type. However, the constructed wetlands were generally effective under our test conditions at maintaining effluent nitrate levels at ≤10 mg/liter (10 ppm) when loading rates were ≤50 mg/liter (50 ppm). Presence of emergent wetland plants (those with roots imbedded in the substrate and shoots extending above the water surface, rather than floating or submerged plants) in the system was more important for effectively reducing nitrate levels in effluent from SSF than from FSF cells.

The Use of Saline Water in Agriculture in the Near East and North Africa Region: Present and Future

SUMMARY Salinity is a major problem that negatively impacts agricultural activities in many regions in the world, and especially the Near East and North Africa region. Generally, salinity problems increase with increasing salt concentration in irrigation water. Crop growth reduction due to salinity is generally related to the osmotic potential of the root-zone soil solution. This will lead to certain phenological changes and substantial reduction in productivity. Salinity also affects the soil physical properties. Sewage treated wastewater is an alternative water source for irrigation. Using such wastewater will provide a new water resource to expand agricultural activities as well as reduce the environmental pollution. Each country in the region has a unique system of rules and regulations to protect the quality of water resources. Important aspects that should be taken into account when using wastewater for irrigation are discussed, including some information on the different irrigation systems used in the region, and the factors leading to success of using saline water for economic crop production. Information on the use of saline water or marginal saline soils for wheat production and improvement of irrigation systems, including old land irrigation systems, under Egyptian conditions is also presented. The regional experiences and the future prospects of using saline water for crop production that vary greatly among countries in the Near East and North Africa region are summarized. This article also presents information on special cultivation methods, such as protected agriculture and soilless culture that can help in alleviating the salinity effects. Finally, the article includes some examples on the inherited knowledge for saline agriculture that conveys the grower's experience in the Near East and North Africa region where several living examples for unique and sustainable cultivation system are still in operation. One of the most impressive cultivation techniques for bio-saline crop management in Egypt is the Edkawy production system.

Leaching requirement conceptual models for reactive salt

Accurate prediction of the leaching requirements (Lr) of crops and striving to attain them is essential for efficient irrigation water use. Solute modeling was extended to develop four Lr conceptual models that do not neglect solute reactions in the root-zone, surface evaporation, and the influence of immobile wetted pore space. The models were based on: (i) the water movement equation which included an exponential water-uptake function (-e) or the 40-30-20-10 water-uptake function (-4); (ii) the solute movement equation for a reactive salt of a linear reaction term (the Lrchem-e and Lrchem-4 models); or the employment of output (salinity of soil solution, EC vs concentration factor, CF) of the SAO comprehensive chemical model (the LrSAO-e and LrSAO-4 models); and (iii) the inclusion of an effective soil solution volume in the transport equations. The root-zone average relative effective soil solution volume νeff (L | L50, p) was of sigmoidal response to leaching fraction (L) with two adjustable parameters L50 and p; the root-zone average reduced retention coefficient decreased linearly with L; and salt concentration at soil surface was related to salt concentration of irrigation water (ECi) by the fraction of irrigation water that evaporated (∈). The resulted concentration profiles indicated the salt behaved as a conservative one down to a threshold depth (xs) below of which salt was retained and precipitated. The depth of the conservative-salt front, xs increased with L and the 40-30-20-10 water-uptake pattern overestimated the xs depth relative to the exponential pattern. Concentration profiles were integrated to compute the root-zone average salinity, which was converted to crop salt-tolerance threshold (AE). The four conceptual models were successfully calibrated using experimental AE/ECi vs. Lr data with the input parameter values: ς = 0.27, p = 1.44, L50 = 0.16, ω = 2, and ∈ = 0 or 0.1 for the exponential or the 40-30-20-10 pattern, respectively; where ς is relative root length parameter and ω is a weighing parameter. No significant difference existed between the four model correlations at the 0.05 level. The four models require ECi and AE of the crop as input for Lr prediction. Sensitivity analysis revealed predicted Lr was sensitive the least to error in ∈. For tolerant and moderately tolerant crops Lr was sensitive the most to ς, and for sensitive crops to L50 and p. Model verification and validation were discussed. In deriving the present Lr models, no osmotic adjustment was required and both the exponential and the 40-30-20-10 water uptake patterns were, equivalently, applicable.

Effect of salinity and K/Na ratio of irrigation water on growth and solute content of Atriplex amnicola and Sorghum bicolor

Total salinity and K/Na ratios in the irrigation water were varied for two different types of plants; sorghum, a moderately salt tolerant crop plant whose growth is inhibited by high NaCl levels, and Atriplex, an extreme halophyte whose growth is stimulated by high NaCl levels. Sorghum growth was significantly reduced at all salinity levels from 50 to 150mM, but Atriplex growth was not reduced until salinity exceeded 100 mM. In both species, growth reductions were increased by increasing the ratio of K to Na from 1/100 to 1/1 in the irrigation water. The amount of K and Na accumulated in the leaves of Atriplex reflected the relative amounts in the irrigation water, but in sorghum most of the increase in the concentration of K + Na was due to the increase in K regardless of the ratio of K/Na in the irrigation water. Nitrate levels in leaves of sorghum were little affected by salinity but were decreased in Atriplex by the combination of high salinity and K/Na ratio. The lower amount of salt accumulation in sorghum was compensated for by greater accumulation of soluble organic compounds, such as proline and soluble carbohydrates, that presumably were osmotically active and could contribute to osmotic adjustment. All of the results supported the general conclusion that, despite differences between glycophytes, such as sorghum, and halophytes, such as Atriplex, in sensitivity to the total soluble salt concentration in irrigation water, in both species growth was reduced more by K/Na ratios of 1/1 and 1/10 than by a ratio of 1/100 at those salinity levels that significantly reduced growth in each species.

Irrigation with brackish water under desert conditions VI. Automated systems to produce a range of salt concentrations in irrigation water for experimental plots

This paper describes three different systems developed recently in the Negev desert to enable the carrying out of both small- and large-scale field trials on irrigation with brackish and saline water. All three systems are fully automated. The first system, called the mixing junction, was designed to supply to the field relatively large quantities of water with a predetermined, constant salt concentration, when the salinity level of the water source at the field head may vary. The system has an electrical conductivity (EC) sensor inserted after the mixing junction and connected to an electronic logic circuit that operates hydraulic valves for brackish and fresh water in opposite directions to obtain the desired EC level. The second system, called the brine injection system, was developed to produce a range of salt solutions for field studies of salinity when the major water source is of a low and constant salinity level. The system is based on the injection of different amounts of brine simultaneously into several irrigation lines with a water-driven fertilizer pump, through a series of water flow regulators. The third system, called the mixing manifold, was developed to dilute an abundant source of water having a high and constant salinity level with fresh water, to obtain a range of salt concentrations in the irrigation water. The two water sources pass through parallel flow regulators and are mixed at the outlet of the regulators. Water flow through the regulators is controlled by an irrigation computer. All these systems have been operating successfully for periods of from 2 to 5 years.

Evaluation of irrigation water quality for a spatially variable field

A model to predict the optimal salt concentration of irrigation water when various sources of water are available is described and illustrated for citrus. The model employs a stochastic model for soil water and solute movement and a linear programing economic model for best solutions over an extended time period. The model was developed for a Mediterranean‐type climate where an irrigation (salt accumulation) season is followed by a rainfall (salt leaching) period. Soil water flow generated by an irrigation or rainfall is assumed to be steady and vertical. Transient solute transport is assumed to obey the diffusion‐convection equation. The probability of any given average root zone salinity after any cycle of irrigation or rain is calculated for any combination of applied water salinity and initial soil salinity using a probability density function for the saturated hydraulic conductivity. The expectation of the total income from a crop yield having a known response function to soil salinity is maximized by the model subject to a given probability of the average root zone salinity exceeding a prespecified critical concentration. The cost of water is assumed to decrease as the salinity of irrigation water increases. Optimal water management depending on the salt concentration of the irrigation water over 6 years for citrus is illustrated in terms of minimum cost, maximum income, optimum salt concentration of the irrigation water, spatial distribution of average root zone salinity, and the probability of exceeding a prescribed critical soil salinity concentration.

Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds

AbstractIrrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes.