Showing papers in "Irrigation Science in 1985"

Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Abstract: The effect of soil texture and CaCO3 content on water infiltration rate in crusted soil was studied with the use of a rain simulator Two types of soils with low exchangeable sodium percentage (ESP 400 mm winter rain Soil samples with clay percentages between 3 and 60 were collected in each region Distilled water (simulating rainfall) and saline water (simulating irrigation water) were sprinkled on the soil The soils were exposed to ‘rain’ until steady state infiltration and corresponding crust formation were obtained For both types of soils and for both types of applied water, soils with ∼ 20% clay were found to be the most sensitive to crust formation and have the lowest infiltration rate With increasing percentage of clay, the soil structure was more stable and the formation of crust was diminished In soils with lower clay content (< 20%), there was a limited amount of clay to disperse and, as a result, undeveloped crust was formed Silt and CaCO3 had no effect on the final infiltration rate for either type of applied water, whereas with saline water, increasing the silt content increased the rate of crust formation

Drip irrigation of cotton with saline-sodic water

Abstract: A two-year study was conducted in the Negev region of Israel, using the drip method, to determine the effect of four levels of water quality (EC =1.0, 3.2, 5.4 and 7.3 dS/m) in combination with three soil amendment treatments (gypsum spread on the soil surface along the drip laterals after planting, injection of H2SO4 into the water during each irrigation, and a control) on plant response, salt distribution in the soil profile, and soil sodification processes. Salinity did not reduce yields even at the highest level, in spite of sodium and chloride accumulation. The highest seed cotton yield (6.4 t/ha) was obtained with the local well water (EC =3.2 dS/m), indicating an optimal response to salinity. The addition of soil amendments during the irrigation season, although reducing exchangeable sodium accumulation near the emitter, endangers the next crop by increasing sodium accumulation under the plant row. It is therefore, recommended that the amendment be applied only before the winter.

Grain yield, yield components, drought sensitivity and water use efficiency of spring wheat subjected to water stress at various growth stages

Abstract: The influence of water stress at various growth stages on yield and yield structure of spring wheat (Triticum aestivum, L., cv. “Sappo”) was investigated using lysimeters in the field, automatically protected from rain by a mobile glass roof. Each drought treatment consisted of a single period without irrigation. Irrigation was resumed when all available soil water (100 mm between field capacity and permanent wilting to a depth of 100 cm) had been used. The drought periods were defined as beginning when relative evapotranspiration decreased below one and ending at reirrigation. The first drought occurred during tillering and jointing and the final one during grain formation.

Salt effects on germination and seedling emergence of several vegetable crops and guayule

Abstract: Salt effects on seed germination and seedling emergence of several crops are evaluated to understand poor plant stands occurring in furrow-irrigated fields in saline areas. The test crops were carrot (Daucus carota L. cv. Imperator 58), chile pepper (Capsicum annuum L. cv. New Mexico 6-4), tomato (Lycopersicon esculentum M. cv. Rutgers), and guayule (Parthenium argentatum G. cv. 593). Seed germination was measured in petri-dishes containing saline solutions (0.8 to 32 dSm−1 with a Na to Ca + Mg ratio of about 2 : 1); and seedling emergence in potted fine loamy sand subirrigated in a greenhouse with saline waters (0.8 to 7.6 dSm−1 with SAR < 16). Seedling emergence through a thin layer of salted-loamy sand (having ECeup to 46 dSm−1) placed on emerging seedlings was also evaluated. Germination of tomato and carrot seeds began to decline at solution salinities of 12 and 18 dSm−1, respectively, and was virtually zero at 23 dSm−1, Chile pepper and guayule germinated well at 23 dSm−1, Tomato had the highest emergence, and guayule the lowest, showing less than 20% when subirrigated at 2.2 dSm−1, Seedling emergence which increased in the order of guayule, carrot, chile pepper and tomatoes did not quantitatively correlate with seed germination. However, it did correlate with the emergence through the thin layer of the salted-sand placed over emerging seedlings except in tomato. Salinity of the saturation extract of the surface 5 mm soil increased to 21 and 31 dSm−1, in 7 days when subirrigated with water of 4.3 and 6.4 dSm−1, respectively. Poor seedling emergence of guayule, carrots and, to some extent, chile pepper appeared to be caused by hypocotyl mortality associated with the salts accumulated at the soil surface, but not by reduced seed germination. The control of surface accumulated salts should be the target of management for improved emergence of these crops.

Prediction of leaching fraction from soil properties, irrigation water and rainfall

Abstract: Fine textured soils (> 40% clay) form a major proportion of irrigated soils in northeastern Australia. More than half these soils are irrigated with groundwater, some of which has high salinity (electrical conductivity > 2.9 mS cm−1). A simple prediction of salt leaching was sought to aid in land management decisions.

Irrigation uniformity as related to optimum crop production — additional research is needed

Abstract: The fact that uniformity of infiltrated water has significant effects on crop yield and optimum water application has been well documented. However procedures for obtaining quantitative data on infiltrated water uniformity on a field scale which can appropriately be combined with crop-water production functions to quantify and establish optimum irrigation management have not been adequately developed and verified and justify further research. Matching the scale of measurement to root zone scale is conceptually important but has not been properly verified. Data on infiltration rates measured in the field which have been reported in the literature were combined with crop water production functions to illustrate that the effects of uniformity on yields can be large.

Evapotranspiration of citrus as affected by soil water deficit and soil salinity

Abstract: The extent to which evapotranspiration (ET) of Valencia citrus trees is affected by differing soil water depletions (SWD) and soil salinity regimes was determined during five seasons during which soil salinity levels varied. Three weighing lysimeters, each with a 14 year old tree, were used to measure daily ET and to schedule irrigation to maintain SWD at maxima of 15, 75 and 150 mm respectively. Tensiometers and salinity sensors were used to indicate the in situ soil matric and soil solution osmotic potentials. Total soil water potential was calculated from tensiometer and salinity sensor readings weighted for root density with depth. The total of these for the summer months was found to be linearly related (Fig. 5) to the mean ET/Ep (Ep=A-pan evaporation). The slope and threshold of ET reductions with decreasing soil water potential for the low frequency irrigation treatment (150 mm SWD) show good agreement with the slope and threshold of yield decrease that is calculated from soil salinity in the lysimeter using previously reported salinity-yield relationships. The reduced water uptake due to increasing soil salinity has important implications for soil salinity control, since the lower uptake should in theory increase the leaching fraction. This implies a degree of self adjustment to the leaching fraction when irrigating with increasingly saline waters if water applications are scheduled as for non-saline conditions.

Chloride toxicity in citrus

Abstract: Citrus orchards (cv. Valencia and cv. Washington Navel Orange) on sandy soils in semi-arid South Australia (evaporation 1,900 mm, rainfall 240 mm) are irrigated with water from the River Murray having a chloride content of less than one to over 10 meq/1 (electrical conductivity 0.35–1.4 dS/m). Field observations and the literature suggest that at irrigation water salinities above 4 meq/1 Cl-, yield losses might be expected due to toxic effects of chloride rather than osmotic effects.

Water and salt balance in an irrigated area of the Ebro River Basin (Spain)

Abstract: Water balance components (effective precipitation, diverted water, actual evapotranspiration and irrigation return flow) and salt balance components (TDS of precipitation, diverted water and irrigation return flow, and sources/sinks in the soil profile) of the Violada irrigation district (3,913 ha) located in the Ebro river basin were measured for the 1982 and 1983 hydrological years. The irrigation district discharges annually 73,000 t of salt into its receiving river. The gypsiferous character of the soils gives a saturated gypsum character to the leachate resulting in a fairly constant TDS of the irrigation return flow (coefficient of variation of 12% for the 1982 hydrological year). The salt load of this area is 18.8 t/ha due to the gypsum content of the soils and improper water management. This results in a mean annual irrigation application efficiency (JAE), calculated as the average actual evapotranspiration/diverted irrigation water ratio, of 0.67 for the 2 years studied. On-farm irrigation system evaluation tests were performed in order to evaluate uniformity of water application and irrigation requirements of the main crops. The results indicate that JAE can be improved by means of better irrigation water management (especially irrigation scheduling) and proper land levelling of the fields.

Relationship between root uptake-weighted mean soil water salinity and total leaf water potentials of alfalfa

Abstract: Alfalfa was grown in five laboratory soil columns and irrigated at a fixed average amount per day. One column received tapwater at 6-day intervals; the others saline water (h o=−12 m) at intervals of 4, 6, 8, and 12 days. The alfalfa was harvested at 24-day intervals. The resulting widely varying distributions of soil water content, pressure potential and osmotic potential were measured in detail. From these data variously weighted mean soil water potentials were calculated and correlated with measured total leaf water potentials. This indicated that in the moist, saline soil columns the alfalfa plants tended to maximize the root uptake-weighted mean total soil water potential and, since the pressure potentials were generally high compared with the osmotic potentials, also the uptake-weighted mean osmotic soil water potential (minimize the uptake-weighted mean salinity). For the drier nonsaline soil column the leaf water potentials were much lower than expected from the soil water retention function. This was attributed to dominant resistance for water flow through the soil and across the soil-root interface.

Dilution of brackish waters in irrigation networks —An analytic approach

Abstract: Rational method of improving poor water by the admixture of good-quality water for irrigation purposes is proposed and demonstrated. The principles of the dilution process, carried out in dilution junctions, are explained. Continuity equations for water and for the mass of relevant substances present in the water are derived for a dilution junction. These equations characterize the suitability of the mixture for irrigation. The optimal operation of a dilution network for irrigation with brackish, sewage and fresh water is formulated and analyzed based on graph theory. A system of non-linear constraints which satisfactorily describes requirements for water quality and flow rates in terms of field demands and water sources is presented. Optimal operation is defined as the minimum water delivery cost. In dilution networks having no more than one outflow conduit of unknown concentration per junction, the non-linear optimization problem can be reduced into a linear one, making the use of Linear Programming (LP) possible.

The transport of chloride and non-diffusible solutes through soil

Abstract: The mean velocity at which water flowed through large undisturbed cores of soil was determined from the breakthrough of surface-applied Cl−, using a transfer function based on the normal distribution of the logarithm of cumulative drainage. For soils ranging in texture from sandy loam to silty clay loam, mean pore water velocities varied from 7 to 30 cm h−1 for an input rate of 2 cm h−1. Antibiotic-resistant Escherichia coli applied to the soil surface appeared to be transported through large pores only (> 10–15 μm diameter), and the relative concentration in the effluent (C/C0) did not change significantly with effluent volume. Mean C/C0 values for E. coli in these soils, which ranged from 0.003 to 0.94, could be predicted from the mean pore water velocity derived from Cl− transport.

Effect of nozzle type on runoff and yield of corn and sorghum under center pivot sprinkler systems

Abstract: Corn (Zea mays L.) and grain sorghum (Sorghum bicolor L.) production were compared under impact and spray nozzled center pivot sprinkler systems. The crops were grown under two pairs of sprinkler systems located approximately 110 km apart. One system of each pair was equipped with high pressure (379 or 414 kPa) impact sprinkler heads and the other system was equipped with low pressure (172 or 207 kPa) spray nozzles. Half of each circle was planted to corn and half was planted to sorghum. Additionally, four tillage treatments were included in the experimental design (conventional tillage, conventional tillage + deep ripping, conventional tillage + diking, and minimum tillage). The evaporative losses from the high pressure system with impact sprinkler heads were not significantly different from the low pressure system with spray nozzles. The minimum tillage and deep ripped treatments reduced runoff while diking eliminated it. The two nozzle types did not produce significantly different grain sorghum yields; however, corn yielded significantly more under the high pressure system with impact sprinkler heads than under the low pressure system with spray nozzles. The different tillage treatments did not influence yields of either crop significantly.

Calibration and verification of an irrigation return flow hydrosalinity model

Abstract: A modified irrigation project model (first developed and tested in its original form by Tanji in 1977) is presented which evaluates the impacts of present as well as future alternative land and water resource management on the volume and salt concentration in the irrigation return flow. Modifications were necessary to fit more closely into the prevailing hydrologic and salinity conditions in the Ebro River Basin (Spain), and include the initial and final stored soil water, rim inflows from adjacent hydrologic systems and contributions of gypsum and soluble salts to salt loadings.

Effects of wetting agents on water infiltration into poorly wettable sand, dry sod and wettable soils

Abstract: Six commercial wetting agents (three nonionic and three anionic compounds) were tested for their effects on water infiltration into poorly wettable sand, a layer of dry bermudagrass sod, and two wettable soils. The poorly wettable sand and the sod of dormant bermudagrass were obtained from an old lawn area, and the wettable soils (silty clay, and saline sodic silty clay loam) from a pecan orchard and a cotton field. The infiltration of tap water (salinity of 0.8 dS m−1 and a sodium adsorption ratio of 5) was measured in laboratory columns using air-dried soil (or sod) samples after initial soil application of wetting agents at rates equivalent to 12 and 24 L ha−1. The stem of the dormant bermudagrass exuded a brownish substance, and was found to be strongly water-repellent. Application of wetting agents markedly improved initial water infiltration into both the poorly wettable sand and the sod. The effect persisted for the entire test period of four irrigations using a total of 10 cm of water. Effectiveness, however, varied significantly among the tested compounds: polyoxyethylene glycol, polyethylene glycol ether and sulfosuccinate compounds were more effective than linear sulfonate or ethoxolated alcohol. The water-repellency of the poorly wettable sand was reduced substantially without wetting agents after two irrigations (using 5 cm of water), and that of the dormant sod after three irrigations (7.5 cm of water). Water infiltration into the air-dried wettable soils also increased significantly in the 1st irrigation (using 10 cm of water) showing 10 to 25% reductions in infiltration time with the application of polyoxyethylene glycol and polyethylene glycol ether.

Potassium induced improvement of yield response in barley exposed to soil water stress

Abstract: The interaction of different K status of barley plants (Hordeum vulgare, L.) and water stress on yield and water relations was studied. The plants which were cultivated outdoor in pots and supplied with 0.8, 5.0, 8.5 or 12.0 g K per pot, as KCl, were subjected to increased soil water stress during the early grain filling stage.

Irrigation management methods for reducing water use of cowpea ( Vigna unguiculata [L.] Walp.) and lima bean ( Phaseolus lunatus L.) while maintaining seed yield at maximum levels

Abstract: In a previous study conducted at the University of California at Riverside, it was shown that water use of cowpea could be reduced while maintaining seed yields by withholding irrigation during the vegetative stage in a rain-free environment, and then irrigating when estimates based on potential evapotranspiration, indicated 40% depletion of available moisture in 90-cm depth of soil The general applicability of this efficient irrigation management method was tested by experiments conducted at the West Side Field Station in the San Joaquin Valley of California with six irrigation treatments, three different row spacings (single rows on 76- and 102-cm beds, and double rows on a 102-cm bed), a semi-erect cultivar of cowpea (Vigna unguiculata [L] Walp), and a prostrate cultivar of lima bean (Phaseolus lunatus L) Withholding irrigation during the vegetative stage following pre-irrigation substantially reduced dry matter at anthesis (−17% to −38%) and water use (−101 mm) of cowpea, but did not influence seed yield or shoot dry matter at harvest for either cowpea or lima bean Increasing the irrigation interval until 75% nominal depletion of available water in 90-cm depth of soil reduced water use (−139 cm), but did not affect seed yield of cowpea Lima bean, however, showed a significant decrease in shoot dry matter production (−17%) and in seed production (−18%) at the longest irrigation interval involving 75% nominal depletion The different row spacings used in this experiment did not affect shoot dry matter or seed production of the semi-erect cowpea However, shoot dry matter and seed yield were significantly greater for the prostrate lima bean grown with double rows on a 102-cm bed Seed yield was 46% and 18% greater than with single rows on 76-cm and 102-cm beds, respectively Generally, variations in seed yields of lima bean were positively correlated with variations in shoot dry matter production Nominal depletion of available soil water provided a practical method for scheduling irrigations, but the results with cowpea indicated that the critical level, which resulted in the greatest reductions in water use while maintaining maximum seed yield varied from 40% (at Riverside) to 75% (at West Side Field Station) Additional methods are needed to fine-tune irrigation which is based mainly on nominal depletion of available water Generally, pressure chamber estimates of leaf water potential exhibited too little variation among plants subjected to different irrigation treatments for it to be useful for fine-tuning irrigation schedules for either cowpea or lima bean However, differences in temperature between canopy and air, when expressed as a function of either vapor pressure deficit or canopy temperature, and related to percent reduction in yield, appeared to have sufficient resolution to provide a practical method for fine-tuning irrigation schedules for cowpea during flowering and pod-filling, but not lima bean Normalizing temperature differences with vapor pressure deficit was more effective, but normalizing with canopy temperatures is more convenient because it does not require a measurement of air humidity

Application of automated flow and salinity control to dilution of saline irrigation water

Abstract: The utility of a saline water source for irrigation might, in many cases, be greatly increased if it could be diluted by mixing it with a higher quality source of water prior to field application. This paper discusses a number of options for achieving such a dilution subject to imposed constraints. Firstly, we derive and discuss the principles of achieving control of irrigation salinity level when waters of two different qualities and flow rates are used. Secondly, we formulate and discuss the dynamic performance of a prototype on a controlled dilution junction with and without water storage. Finally, we discuss the general problem of achieving simultaneous salinity and flow rate control, using dual feedback control sensors to compensate for variations both in salinity and in flow rate of the saline supply source in order to produce a desired salt concentration in the irrigation water.

Reclamation of saline organic soil

Abstract: Reclamation of saline, organic soils in the Sacramento-San Joaquin Delta of California was accomplished by both sprinkling and continuously ponding water on the soil surface. The reclamation data support the generalized guideline established for saline, organic soil.

Influence of season to season variability in weather on irrigation scheduling of wheat: A simulation study

Abstract: There is an increasing demand from farmers for irrigation scheduling advice. Where rainfall and evapotranspiration vary little from year to year, advice on a fixed irrigation schedule based on mean climatic data can be given. However where significant year to year variability in weather occurs a more flexible approach using actual weather data to predict the current level of soil water and mean climatic data to forecast the future rate of depletion and hence irrigation date may be needed. A technique for deciding the most appropriate scheduling approach was tested by using a simple model of crop growth combined with a soil water balance model to simulate year to year variability in scheduling advice. This technique was applied to irrigated wheat using a set of climatic data from 1968 to 1978 for Griffith in the Murrumbidgee Irrigation Area of New South Wales, Australia. A typical sowing date in early June was used and simulated irrigations were scheduled at an allowable soil water depletion (ASWD) of 62 mm for maximum yield and 93 mm for 80% of maximum. The analysis predicted that weather variability between years would cause the number of irrigations to vary from 2 to 7 for ASWD=62 mm and 1 to 4 for ASWD=93 mm. The interval between irrigations varied from 12 to 30 days, for ASWD=62 mm and from 16 to 28 days, for ASWD=93 mm. The first irrigation occurred between 76 and 131 days from sowing for ASWD=62 mm and from 100 to 140 days from sowing for ASWD=93 mm. The date of the last irrigation was similarly variable. This high degree of variability in the times and frequency of irrigations indicated that in south-eastern Australia accurate irrigation scheduling advice can only be given by using a flexible model using both actual and mean climatic data. A fixed schedule based on mean climatic data would lead to an inefficient use of water caused by the mistiming of irrigations.

Factors affecting uniformity and optimal water management with furrow irrigation

Abstract: A kinematic wave mathematical model which simulates the hydraulics of continuous flow furrow irrigation was linked with a crop yield model and used in combination with an economic model to analyze the effects of inflow rate, water infiltration characteristics and furrow length on uniformity of infiltrated water, runoff, gross profits and optimal number of 12 hour irrigations for corn (Zea mays) assuming other management practices to be constant. Higher uniformity of infiltrated water but more runoff and, in some cases, more deep percolation resulted from increased flow rates. Increases in uniformity of infiltrated water leads to greater profits, which are however offset by the associated increases in runoff and deep percolation. The study shows economically optimal water management for furrow irrigation can be obtained with proper balance between changes in the input variables and runoff and to some extent deep percolation.

The reduction in sodicity during the displacement of mixed CaCl2-NaCl salts from soils by water

Abstract: Displacement of solutions > i00 meq N a + C a per litre by water from columns of sandy loam soil at ESP= 18 led to a reduction in ESP by cation exchange and hydrolysis of exchangeable Na. This conferred some protection on soil structure as shown by the maintenance of hydraulic conductivity. Changes in ESP were computed based on a layer model with stepwise displacement of solution and reequilibration of exchangeable cations with solution after each step. Computed ESP values were greater than those measured, but the differences were accounted for by the hydrolysed Na.

Turfgrass evapotranspiration: Responses to shade preconditioning

Abstract: Sixteen minilysimeters were used in a study to determine the effect of preconditioning to shade on evapotranspiration (ET) by Kentucky bluegrass (Poa pratensis L. var ‘Merion’). Grass that had been preconditioned to 100, 71, 51, and 27% of possible photosynthetically active radiation (PAR) was subjected to full sun (100% PAR) or full shade (2% PAR) for one day periods. Canopy temperature and ET were measured and compared for grass from differing preconditioning treatments. Live biomass was later clipped, dried and weighed. Dry weight increased by a factor of nearly 3 as pretreatment PAR increased from 27 to 100%. In spite of this difference in the 20 mm high canopy densities, ET and canopy temperature were equal for grasses from all preconditioning treatments when placed in full sun or full shade. It was concluded that ET is not influenced by preconditioning to shade as long as complete ground cover is maintained.

The effect of a change in irrigation water quality on the salt load of the deep percolate of a saline sodic soil — a computer simulation study

Abstract: Recent studies conducted in the Bree River Valley in South Africa, have indicated that the return flow from the flood irrigated soils (using saline borehole water) add substantially to the salt load of the receiving river. In the present study an irrigation return flow model, developed at the USBR, was used to predict what the effect of a change in irrigation water quality would have on the chemical composition of the deep percolate of a saline-sodic soil. Three scenarios were investigated, i.e. irrigation with saline borehole water (TDS = 1,279 mg/1), irrigation with low electrolyte water (TDS=91 mg/1), and irrigation with the low electrolyte water in the presence of surface applications of gypsum. The results indicate that the present flood irrigation practices lead to deep percolation losses of ca. 155 mm/ha/a. In the case of the borehole water the TDS content of the deep percolate ranges between 5,500 and 6,400 mg/l, equivalent to salt loads of 8.59 and 9.98 t/ha/a respectively. By replacing the saline borehole water with the low electrolyte water the TDS content of the deep percolate will, over a five year period, be reduced to 2,100 mg/1, and the salt load to 3.3 t/ha/a. Surface applications of gypsum to prevent clay dispersion and hydraulic conductivity failures will, when compared to the low electrolyte scenario, increase the salt load by 1.2 t/ha/a. However, it will still be 4.84 t/ha/a less than is presently the case. It is concluded that by using the better quality irrigation water in combination with gypsum applications, the salt load in the receiving river attributable to irrigation return flow, can be reduced by approximately 10%.

Effect of drying on soil strength and corn emergence

Abstract: Laboratory studies were conducted to evaluate the effects of drying on soil strength and corn emergence (Zea mays L.). Corn was germinated in Billings silty clay under a bank of heat lamps which operated 9, 14, 19, or 24 h per day. Soil strength (modules of rupture), soil moisture content and emergence were measured daily. The relationship of soil strength to corn seedling emergence as influenced by the four light and heat durations and bare and mulched soil surfaces was determined. As soil strength increased emergence decreased until it ceased at soil strengths of about 80 kPa. Strength of this soil had a high negative correlation with soil water content and increased with time. Mulching decreased initial rate of drying, decreased crust strength, and improved corn emergence. The 14-hour light and heat treatment resulted in the highest corn emergence.

Competition for water and nutrients in mixed stands of spring wheat

Abstract: Grain yields, moisture extraction pattern, water use efficiency and NPK uptake were studied with three spring wheat cultivars grown in pure and mixed stands under three irrigation levels. The three spring wheat cultivars produced similar grain yields. None of the mixed stands yielded more than pure stands. Soil moisture extraction pattern of the three cultivars and their binary mixed stands was similar from the top layers, however, more moisture was extracted from deeper layers by the tall cultivar C 306 and mixed stands having C 306 as a component cultivar. The water use efficiency of the dwarf cultivar HD 2160 was higher than the other two cultivars. Two mixed stands, namely, 3 : 1 and 1 : 1 Kalyansona: C 306 had a higher water use efficiency than their pure stands but all other mixed stands were intermediate. The grain yield and NP uptake of the dwarf cultivar HD 2160 were less when it was grown in mixed stands, while that of semi-dwarf cultivar Kalyansona and tall cultivar C 306 were more when grown with cultivar HD 2160 than when grown alone or together. The K uptake of all the three cultivars was adversely affected when they were grown in mixed stands. Two or three irrigations increased the moisture extraction from top layers but decreased the water use efficiency as compared to one irrigation. Grain yield and NPK uptake of the cultivars and their binary mixed stands were more with two or three irrigations than with one irrigation.