The effect of polyacrylamide on runoff,erosion, and cotton yield from fields irrigated with moving sprinkler systems

Summary Irrigation with self-propelled moving sprinkler irrigation system (MSIS) enhances seal formation at the soil surface and results in large amounts of runoff and erosion which are aggravated by the MSIS high water application rate and reflected in lower yields. The effect of polyacrylamide (PAM) application (at the equivalent rate of 20 kg ha^-1), prior to the irrigation season, on runoff and erosion from bare soil and soil covered with a crop, as well as on cotton yield was studied in a clay loam vertisol (Typic Chromoxert) and a silt loam loess (Calcic Haploxeralf). A center pivot and a lateral MSIS were used in the vertisol and loess, respectively. Vegetative growth of cotton plants in the vertisol was inversely related to water application intensity, which in turn affects runoff. PAM significantly reduced runoff in both the bare and crop-covered soils. The runoff level from the PAM treatments was 50–70% of that of the control. PAM also reduced erosion especially in the vertisol soil. However, the amount of eroded material carried by a unit runoff was similar in both treatments for both soils, indicating that PAM influences erosion by reducing runoff levels. A trend whereby PAM increased yield of cotton (Gossypium hirsutum L., cv. Pima S5) compared with the control was observed. Our results suggest that, under irrigation with a MSIS, reducing runoff is essential for obtaining higher yields. PAM is suggested as an effective tool to attain this target.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 2866-E, 1989 series     

Influence of leaching with different amounts of water on desalinization and permeability behaviour of chloride and sulphate-dominated saline soils

Desalinization studies were carried out in Cl-dominated (Cl:S0₄ = 7:3) and SO₄-dominated (Cl:S0₄ = 3:7), saline (ECe = 9 dS m⁻¹, ESP = 10) sandy loam soils, filled in plexiglass columns up to a height of 60 cm at uniform bulk density. Both soils were subjected to leaching with three amounts, i.e. 20, 40 and 60 cm of distilled water, 5 cm at a time until the three leaching cycles were completed. The S0₄ profiles had 20–75% faster percolation than their Cl counterparts, when 40 cm of water was leached. With higher amounts of leaching water, the differences in permeability between the two soils narrowed and became indistinguishable when 60 cm of water was leached. Desalinization of the Cl-profiles was more efficient than the S0₄-profiles, but the reverse was the case with desodification. When the depth of water (dW) leached was less than or equal to the depth of soil WS), desalinization was less efficient (10–25%) under S0₄ than under Cl-salinity. However, when dW was greater than dS, the differences in the magnitude of leaching of salts under the two salinities narrowed and became equal at a dW/dS ratio of 2. An increase in the soil ESP from 10 to 35 resulted in a 75% decrease in soil permeability under Cl compared with a 64% decrease in S0₄-salinity. At ESP of 10, application of farmyard manure (FYM) as an amendment increased soil permeability for both Cl- and S0₄-dominated soils. However, at higher ESP levels (30–35), FYM application decreased soil permeability under Cl-dominated soil, but increased it under S0₄-dominated soil.     

Soil solution and exchange complex response to repeated wetting–drying with modestly saline–sodic water

Coal bed natural gas (CBNG) extraction in the Powder River (PR) Basin of Wyoming and Montana produces modestly saline-sodic wastewater, which may have electrical conductivity (EC) and sodium adsorption ratios (SAR) exceeding accepted thresholds for irrigation (EC = 3 dS m⁻¹, SAR = 12 (mmol_c l⁻¹)^1/2. As an approach to managing large volumes of CBNG-produced water, treatment processes have been developed to adjust produced water salinity and sodicity to published irrigation guidelines and legislated in-stream standards. The objective of this laboratory study was to assess acute and chronic soil solution EC and SAR responses to various wetting regimes simulating repeated flood irrigation with treated CBNG product water, followed by single rainfall events. Fifty-four soil samples from irrigated fields in southeast Montana were subjected to simulated PR water or CBNG water treated to EC and SAR values accepted as thresholds for designation of saline × sodic water, in a single wetting event, five wetting–drying events, or five wetting–drying events, followed by leaching with distilled water. Resultant saturated paste extract EC (ECe) and SAR of soils having <33% clay did not differ from one another, but resulting ECe and SAR were all less than those for soil having >33% clay. Repeated wetting with PR water having EC of 1.56 dS m⁻¹ and SAR of 4.54 led to SAR <12, but brought ECe near 3 dS m⁻¹. Repeated wetting with water having salinity = 3.12 dS m⁻¹ and SAR = 13.09 led to ECe >3 dS m⁻¹ and SAR near 12. Subsequent inundation and drainage with distilled water, simulating rainfall-quality leaching, reduced ECe and SAR more often in coarse-textured, high salt content soils than in finer-textured, lower salt content soils. Decreases in ECe upon leaching with distilled water were of greater magnitude than corresponding decreases in SAR, reinforcing supposition of sodium-induced dispersion of fine-textured soils as a consequence of rainfall following irrigation with water having salinity and sodicity levels equal to previously published thresholds.     

Polyacrylamide coated Milorganite™ and gypsum for controlling sediment and phosphorus loads

The application of polymer for controlling erosion and the associated nutrient transport has been well documented. However, comparatively less information is available on the effect of polymer application together with soil amendments. In this study, the effect of polyacrylamide (PAM) in combination with surface application of gypsum and Milorganite™ (MILwaukee ORGAnic NITtrogEn) biosolid for reducing sediment and phosphorus transport under laboratory rainfall simulations was investigated. The treatments considered were bare soil, gypsum, Milorganite™, gypsum + Milorganite™, PAM-coated gypsum and PAM-coated Milorganite™. Application rates for gypsum and Milorganite™ were 392 kg ha⁻¹ (350 lb/acre) and 726 kg ha⁻¹ (650 lb/acre), respectively. The PAM was coated on gypsum and Milorganite™ at an application rate of 11.2 kg ha⁻¹ (10 lb/acre) and 22.4 kg ha⁻¹ (20 lb/acre), respectively. Rain simulation experiments were conducted using a rainfall intensity of 6.0 cm h⁻¹ for 1 h on a 10% slope. Surface runoff was collected continuously from each soil box over 10 min intervals and leachate was collected continuously over the 60 min simulation. The reduction in runoff or in leachate for all treatments was not significantly different from the bare soil control. The sediment loss for PAM coated Milorganite™ was reduced by 77%, when compared to bare soil. However, the sediment loss was not significantly reduced for any other treatment compared to bare soil. The PAM-coated gypsum was not effective for erosion control in our study, and there appears to be a correlation between effectiveness and prill size. However, the gypsum (coated and uncoated) contributed about half of the dissolved reactive phosphorus (DRP) export (in the runoff) compared to bare soil. The PAM-coated Milorgante™ reduced the DRP and total phosphorus (TP) export to 0.3-0.5 times that of Milorganite™ and to levels similar to bare soil. The decreased sediment and phosphorus export for the PAM-coated Milorganite™ treatment is a signal for a potential management practice for controlling erosion and nutrient transport in fertilized agricultural landscapes.     

Effect of polyacrylamide and gypsum on surface runoff, sediment yield and nutrient losses from steep slopes

Hilly terrains with steep slopes and poor vegetative cover are prone to soil erosion. Crop productivity from such lands can be increased by adding correct amounts of soil conditioners such as polyacrylamide (PAM) and gypsum (G) to reduce soil erosion and to improve settling of suspended sediment. The field experiments were conducted in hilly areas with 97% land slope to evaluate the effectiveness of PAM and G when applied as single and concurrent doses of 20 and 2500 kg ha⁻¹, respectively to check surface runoff, sediment yield and major nutrient (N, P, and K) losses under natural rainfall conditions. The results indicate that concurrent application of PAM and G was most effective closely followed by G alone. However, considering the costs of PAM and gypsum and labor involved in their concurrent application on large scale, the application of gypsum alone is recommended in controlling the surface runoff, sediment yield and major nutrient losses from steeply sloped lands in Indian Himalayas.     

Effects of wastewater irrigation on soil sodicity and nutrient leaching in calcareous soils

Soil column studies were conducted with two soils to assess the effects of irrigation with wastewater on soil and groundwater quality. Upon the application of wastewater, exchange occurred between solution sodium (Na⁺) and exchangeable cations (Ca²⁺, Mg²⁺, K⁺), whereby these cations were released into solution. The average exchangeable sodium percentage (ESP) of the soils increased during leaching from 9 to 21 and 28.8 to 29.7 after applying 5.0 and 3.5 l (about 7 and 6 pore volumes) of wastewater to the soils columns, respectively. Adverse effect of high Na⁺ concentration in the wastewater on raising ESP was less pronounced in the soil having initial high ESP than in the soil with low initial ESP. Salinity of the soils was also increased with the application of wastewater and Mg²⁺ and K⁺ were leached from the soils. These losses would be more severe on soils having a low cation exchange capacity and if, uncorrected could lead eventually to their deficiencies for plant growth. When the soil columns were leached with distilled water the flow rate of one soil decreased to zero after 2.2 pore volume indicating damage to soil structure. Irrigation with wastewater, which is generally more sodic and saline than regional groundwater, increases the rate of soil sodification of shallow groundwater. A relatively simple chromatographic model was used to estimate final ESP profiles in the soils assuming the condition of local equilibrium. This approach had a limited success for one of the soil. Since the final leached concentrations are in good agreement with those of wastewater, we attribute these differences to non-uniform flow through the column. In terms of practical soil and water management, our study reveals that relatively simple means can be useful to predict the water quality in soils, their discharge to ground water, and the hazard of soil structure deterioration.     

模拟降雨下PAM对砂黄土养分迁移影响实验研究

利用室内人工模拟降雨试验,研究了砂黄土施用不同量PAM在降雨条件下入渗-径流、土壤侵蚀和养分迁移特征。研究结果表明,砂黄土在不同PAM用量下均较对照表现出降低入渗增加径流,并能有效减少土壤侵蚀,其侵蚀量随PAM用量增加而减少。径流的增加造成硝态氮,水溶性磷和水溶性钾累积流失量增加,通过径流和泥沙流失的养分很少,硝态氮主要通过淋溶损失,磷和钾移动性弱,土壤固定性强,损失不大。PAM适宜用量在1~3 g/m2之间。     

Irrigation of lucerne with saline groundwater on a slowly permeable,duplex soil

Summary Lucerne was irrigated for three years on a slowly permeable, duplex soil, with saline water up to 2.4 dS m^–1 without significant yield decline. Irrigation water of 4.5 dS m^–1 significantly reduced yield. Lucerne yield was most closely related to the soil ECe of the 0–15 cm depth, rather than the total rootzone, and was described by; Relative yield=100–6.5 (ECe-2.1). While lucerne roots reached depths of at least 150 cm, approximately 80% of total root length was located in the 0–60 cm depth.Increasing salinity increased the plant concentrations of sodium and chloride, however, these changes were not closely related to changes in yield.Soil salinity increased with increasing salinity of the applied water. However, during the irrigation season water penetration and the accumulation of salt within the profile was predominantly restricted to the 0–60 cm depth. No portion of the applied irrigation water was available as a leaching fraction. Any leaching of salts to the watertable, particularly below 120 cm, was due to winter rainfall rather than the application of summer irrigation water.Ripping the soil to a depth of 75 cm increased water infiltration and resulted in increased crop yields, but did not significantly affect the crop relative yield-soil ECe relationship.From the results it is proposed that on the slowly permeable duplex soils, when watertable depth is controlled, management strategies for lucerne irrigated with saline water should be based on controlling the salinity of the shallow soil depths, to 60 cm.     

Distribution and dynamics of soil water and salt under different drip irrigation regimes in northwest China

A 2-year experiment was carried out to investigate the effects of different drip irrigation regimes on distribution and dynamics of soil water and salt in north Xinjiang, China. Five treatments—F7 (0.24 dS m^?1 + Once every 7 days), B7 (4.68 dS m^?1 + Once every 7 days), S7 (7.42 dS m^?1 + Once every 7 days), F10 (0.24 dS m^?1 + Once every 10 days) and F3 (0.24 dS m^?1 + Once every 3 days)—were designed. For all treatments, additional 150-mm fresh water was applied on 10th November in 2009 (winter irrigation) to leach the accumulated salt. The results revealed that irrigation frequency and water quality had significant effects on the spatial distribution and change of soil water content, soil salt and the crop water consumption rate, but had a limited impact on the seasonal accumulative water consumption, and the cotton yield decreased with the decrease in irrigation frequency and water quality on the whole. During the cotton growing season, results showed that the salt mainly accumulated in the 0- to 60-cm soil layer, while the soil salt in 60- to 100-cm layer changed slightly, indicating that the drip irrigation could not leach the soil salt out of the root zone under the irrigation regimes. Therefore, salt leaching was necessary to maintain the soil water–salt balance and to prevent excessive salt accumulation in the root zone. After the 150-mm winter irrigation and subsequent thawing, soil salts were leached into the deeper layers (below 60 cm), and the soil salt content (SSC) (EC_1:5) in root zone in the next year was about 0.2 dS m^?1. Moreover, compared to 2009 season, the SSC within the root zone did not increase even the EC of the irrigation water was up to 7.42 dS m^?1. Additionally, it is important to note that the results were concluded based on the data of the 2-year experiment; further studies are need to optimize winter irrigation amount and assess the sustainability of saline water irrigation since long-term utilization of saline water may lead to soil degradation.     

The effect of saline irrigation on lucerne production: shoot and root growth, ion relations and flowering incidence in six cultivars grown in northern Victoria, Australia

The effect of irrigation with saline (0.1-7.6 dS m^-1) water on the growth of six cultivars of lucerne was assessed over four irrigation seasons at Tatura, Victoria, Australia. Measurements made in the study included shoot dry matter production, shoot ion concentrations, flowering incidence, root distribution and soil salinity and sodicity levels. After four seasons, soil EC_e levels had risen to 4.2 dS m^-1 at the beginning of the irrigation season and this increased to around 6 dS m^-1 at the end of the season for the highest salinity irrigation treatment (7.6 dS m^-1). The soils in the two most saline irrigation treatments also became sodic (SAR_1:5>3) by the third and fourth seasons. By the second season, cultivars differed significantly in salt tolerance as defined by the rate of decline in dry matter production. The cultivars CUF 101 and Validor were consistently the most salt-tolerant cultivars, although cv. Southern Special produced the greatest amount of dry matter over all salinity treatments. Root densities at depths from 0 to 60 cm were greater under saline (2.5 and 7.6 dS m^-1) than under non-saline conditions (0.1 dS m^-1). Flower production was increased by salinity. It was concluded that, despite the presence of intraspecific variation for salt tolerance, it is detrimental to irrigate lucerne with water at electrical conductivities greater than 2.5 dS m^-1 on a red-brown earth in southern Australia.     

PAM和SAP交并施用对旱区坡地固土截水的影响

对PAM和SAP交并施用对旱区坡地固土截水的影响进行初步测定。PAM和SAP都是很好的土壤改良剂。使用PAM可以显著降低土壤结皮,减少地表径流和土壤侵蚀。SAP可以提高土壤的保水性,改善土壤结构。采用两种SAP施用方式:SAP(0~20cm)混施和SAP(20cm)层施。土槽装填好后,将PAM均匀撒施在土壤表层。将土槽置于调整好角度的支架上。降雨10min,湿润土壤。静置1d后再进行试验。试验结果表明PAM和SAP交并施用可以明显增强土壤的固土截水能力。当SAP混施时,PAM施用量的影响比SAP显著。而SAP层施时,SAP施用量的变化对土壤的固土截水能力没有影响,但PAM依然影响很大。相同PAM和SAP施用量的情况下,SAP混施比层施时减少水土流失量、土壤侵蚀量、地表径流量更大。     

雨滴打击对黄土坡面细沟侵蚀特征的影响

基于模拟降雨试验和纱网覆盖消除雨滴打击作用的试验方法,研究雨滴打击对黄土坡面细沟侵蚀特征的影响。试验包括3种黄土高原代表性的侵蚀性降雨强度(50、75、100 mm/h)和3个细沟侵蚀发生最常见的坡度(10°、15°和20°)。结果表明,与有雨滴打击试验处理相比,纱网覆盖消除雨滴打击后,坡面径流稳定产流率和含沙量均明显减小;坡面侵蚀量和细沟侵蚀量分别减少28.1%~47.7%和20.2%~38.6%;而细沟侵蚀对坡面侵蚀的贡献率增加。消除雨滴打击后,坡度对细沟侵蚀的影响与有雨滴打击时相同,而降雨强度对细沟侵蚀的影响增加。有、无雨滴打击试验处理的细沟密度和割裂度均随着降雨强度和坡度的增加而增大;而细沟倾斜度的变化较为复杂,所以细沟密度和割裂度可作为描述细沟形态的最佳指标。试验结果还表明,雨滴打击对细沟沟槽形状也有间接影响,即消除雨滴打击后,细沟宽度和深度的变异程度减小,沟槽形状更为规则。同时,有雨滴打击试验处理的细沟宽深比随着坡度和降雨强度的增加而减小,而无雨滴打击试验处理的细沟宽深比随着坡度的增加而减小,随着降雨强度的增加呈微弱的增加趋势。     

Model-based evaluation of irrigation needs in Mediterranean vineyards

The irregular rainfall distribution causes interannual variation of water status in Mediterranean vineyards. A frequential analysis of irrigation needs was carried out from continuous simulation of the soil water balance during 39?years in south France. The off-season soil water refilling was often incomplete, with a higher frequency in soils with a high total transpirable soil water (TTSW) and/or susceptible to runoff and high evaporation. On soils with high TTSW (over 250?mm), the irrigation need was nil or small (except in situations of high runoff) and focused on the beginning of the crop cycle. On soils with lower TTSW, the irrigation need increased on average and was spread all along the grapevine cycle due to the limited buffering effect of the soil water reservoir. For 100?mm TTSW, the irrigation need was 40–60?mm for half of the years. The calculated irrigation needs were sensitive to the soil (TTSW, susceptibility to runoff and evaporation) and canopy (crop coefficient) properties. Therefore, soil and canopy management should be considered together with irrigation for an integrated approach of water management.     

Irrigation water quality options for corn on saline,organic soils

Summary Corn production on the organic soils of the Sacramento-San Joaquin Delta of California was affected by the salinity of the irrigation water and the adequacy of salt leaching. Full production was achieved on soils that were saline the previous year, provided the electrical conductivity of the irrigation water (EC_i) applied by sprinkling was less than about 2 dS/m and leaching was adequate from either winter rainfall or irrigation to reduce soil salinity (ECM_SW) below the salt tolerance threshold for corn (3.7 dS/m). For subirrigation, an EC_i up to 1.5 dS/m did not decrease yield if leaching had reduced ECM_SW below the threshold. If leaching was not adequate, even nonsaline water did not permit full production. In agreement with previous results obtained in a greenhouse, surface irrigation with water of an electrical conductivity of up to 6 dS/m after mid-season (end of July) did not reduce yield below that of treatments where the salinity of the irrigation water was not increased at mid-season. Results also reconfirm the salt tolerance relationship established in the previous three years of the field trial. The earlier conclusion that the irrigation method (sprinkler or subirrigation) does not influence the salt tolerance relationship was also confirmed.This project was sponsored jointly by the California State Water Resource Control Board, the California Department of Water Resources, the University of California, and the Salinity Laboratory of the US Department of Agriculture     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

Soil water storage and surface runoff as influenced by irrigation method in arid soils with surface crust

The effects of irrigation methods, application rates and initial moisture content on soil water storage and surface runoff were studied in soils liable to surface crust formation during 1995–1996 at the University of Jordan Research Station near Al-Muwaqqar village. Four irrigation methods were tested (sprinkler, furrow, basin and trickle) and four application rates (6.2, 14.4, 24.4 and 28.4 mm/h). Two runs were performed (soil initially dry and soil initially wet). Basin irrigation provided the highest application efficiency followed by trickle, sprinkler and furrow irrigation methods. Entrapping water by the basin borders increased soil water storage by allowing more water to infiltrate through the surface crust. Decreasing the application rate from 28.4 to 6.2 mm/h increased soil water storage significantly in all 150 mm layers to a depth of 600 mm. If the soil was already wet, soil moisture storage decreased owing to siltation during the prewetting and formation of a surface crust and low soil water storage capacity. A sedimentary crust formed at the bottom of the furrows in the furrow irrigation treatment, which reduced soil water storage and increased surface runoff significantly owing to the reduction in infiltration. Increasing the application rate from 6.2 to 28.4 mm/h in the furrow surface irrigation treatment increased the runoff discharge 10-fold. Even with the lowest application rate the runoff coefficient under sprinkler irrigation was 20.3% indicating high susceptibility of Al-Muwaqqar soils to surface crust formation.     

Uptake of shallow groundwater by cotton: growth stage,groundwater salinity effects in column lysimeters

A 3-year column lysimeter experiment was conducted with cotton (Gossypium hirsutum L.) to determine the influence of shallow groundwater salinity on groundwater uptake. Nonsaline (0.3 dS m⁻¹) irrigation water was applied at 7-day intervals throughout the growing season, with the cotton allowed to use stored soil water and groundwater as root water uptake permitted. Groundwater salinities ranging from 0.3 dS m⁻¹ electrical conductivity (EC_w) to 30.8 dS m⁻¹ were evaluated. Water for leaching was applied following harvest each year in amounts adequate to produce a nonsaline soil profile at the beginning of each year. Equations were developed to describe relationships between day of year, growth stage or growing degree days and shallow groundwater uptake. Groundwater contributed about 30 to 42% of seasonal total evapotranspiration (ET) in treatments with groundwater salinity ≤ 20 dS m⁻¹ but declined to 12 to 19% of total ET at higher salinity levels.     

Drip irrigation with saline water for oleic sunflower (Helianthus annuus L.)

The field experiments were carried out in 2007 and 2008 to study the effects and strategies of drip irrigation with saline water for oleic sunflower. Five treatments of irrigation water with average salinity levels of 1.6, 3.9, 6.3, 8.6, and 10.9 dS/m were designed. For each treatment, 7 mm water was applied when the soil matric potential (SMP) 0.2 m directly underneath the drip emitters was below −20 kPa, except during the seedling stage. To ensure the seedling survival, 28 mm water was applied after sowing during the seedling stage. Results indicate that amount of applied water decreases as salinity level of irrigation water increases. The emergence will be delayed when the salinity level of irrigation water is higher than 6.3 dS/m, but these differences will be alleviated if there is rainfall during emergence period. The final emergence percentage is not changed when salinity level of irrigation is less than 6.3 dS/m, and the percentage decreases by 2.0% for every 1 dS/m increase when the salinity level of irrigation water is above 6.3 dS/m, but the decreasing rate will be reduced if there is rainfall. The plant height and yield decrease with the increase of salinity of irrigation water. The height of plants decreases by 0.6-1.0% for every 1 dS/m increase in salinity level of irrigation water. The yield decreases by 1.8% for every 1 dS/m increase in salinity level of irrigation water, and irrigation water use efficiency (IWUE) increases with increase in salinity of irrigation water. The soil salinity increases as the salinity of irrigation water increasing after drip irrigation with saline water in the beginning, but the soil salinity in soil profile from 0 to 120 cm depths can be maintained in a stable level in subsequent year irrigation with saline water. From the view points of yield and soil salt balance, it can be recognized even as the salinity level of irrigation water is as high as 10.9 dS/m, saline water can be applied to irrigate oleic sunflower using drip irrigation when the soil matric potential 0.2 m directly under drip emitter is kept above −20 kPa and the beds are mulched in semi-humid area.     

Leaching rates under a perennial pasture irrigated with saline water

Summary Dilution of saline groundwater (2.5 dS m^–1) for irrigation is a common practice in the Shepparton Region of Northern Victoria. There is little information describing the leaching rates and hence longterm soil salinity levels that will result from such practices. There is also little information to suggest the effect of irrigating with saline water on groundwater recharge.Leaching rates under perennial pastures grown on a Paleustalf were estimated using three methods based on the mass conservation of chloride. Five treatments were irrigated with water ranging from 0.22 dS m^–1 to 4.84 dS m^–1. Leaching rates were greater the higher the salinity of the irrigation water (Table 3). Increased leaching resulted from both increased electrolyte levels in the water and decreased water uptake by plants.A model based on non-steady state solute movement usefully predicted the approach of steady-state conditions in the root zone several years earlier than simple observation of the solute data allowed (Table 5).     

Effect of saline irrigation on germination and growth parameters of barley (Hordeum vulgare L.) in a pot experiment

The effect of saline irrigation was investigated on germination and growth parameters of six barley (Hordeum vulgare L.) cultivars in a pot experiment. The crop germination decreased between 24–35% with irrigation water having EC of 9.26 dS m⁻¹, 28–47% with water EC of 13.4 dS m⁻¹ and 30–53% with water EC of 16.28 dS m⁻¹ among various cultivars. The sequence of reduction in germination was Hassawi > Gusto > Madini > M. Khariji > Qassimi. Plant height and total number of plant tillers decreased significantly with increasing irrigation-water salinity. Plant height ranged between 39.43 cm (Qassimi cultivar) with water EC of 3.00 dS m⁻¹ to 1.97 cm (Gusto) with water EC of 16.28 dS m⁻¹ whereas the range for total number of plant tillers per pot was 77.00 (Qassimi) with irrigation EC of 3.00 dS m⁻¹ to 9.67 (Gusto) with irrigation EC of 16.28 dS m⁻¹. The trend of reduction in plant height for different cultivars was Gusto > Qassimi > Hassawi > Madini > M. Khariji whereas for plant tillers, the sequence was Gusto < Hassawi < M. Khariji < Qassimi < Madini. Greenmatter and drymatter yield decreased significantly with increasing irrigation water salinity. The greenmatter yield ranged between 138.67 g per pot (Madini) with water EC of 3.00 dS m⁻¹ to 11.40 g per pot (Gusto) with water EC of 16.28 dS m⁻¹. A similar trend was found for drymatter yield. The trend of reduction in yield among various cultivars (both greenmatter and drymatter) was Gusto > Hassawi > M. Khariji > Qassimi > Madini. Overall sequence of salt tolerance for different barley cultivars was Madini > Qassimi > M. Khariji > Hassawi > Gusto. A comparison of cultivars indicated that irrigation waters with EC 13.40 dS m⁻¹ and above reduced crop germination and greenmatter production to a significant level. In conclusion, there exists a lot of potential for a reasonable production of barley as forage crop with irrigation water having salinity up to 9.26 dS m⁻¹ provided 15% extra water above crop-water requirement is applied as leaching requirements to control soil salinity.