Corn and alfalfa production as influenced by limited irrigation

Summary Several corn and alfalfa varieties were subjected to varying levels of water deficits under field conditions over a two-year period at the Utah State University Evans farm at Logan, Utah. Dry matter yields of corn and alfalfa varieties showed a linear relationship to evapotranspiration (E _t . In most cases grain yields also showed a linear response to E _t . When relative yields of dry matter and grain of corn varieties were related to relative E _t it was found that the slopes of the linear regression lines changed more between the two years than between the varieties within a given year. It was found that yields predicted by Hanks' (1974) model were highly correlated with measured yields for both corn and alfalfa.in coperation with Agric. Exp. StnGraduate student and professor, respectively     

Corn production as influenced by irrigation and salinity — Utah studies

Summary This paper reports the results of a two-year field study at Logan, Utah which was one of a series of similar experiments carried out at Ft. Collins, Colorado, Davis, California and Yuma, Arizona. A range of water application rates were imposed using the line-source system (Hanks et al., 1976) and in some treatments water was withheld during certain growth stages. Salinity variables were imposed by presalinization before planting and by the use of saline irrigation water. Regardless of irrigation or salinity regime, corn grain and total dry matter production were linearly related to evapotranspiration, which was measured as the sum of irrigation, rainfall and soil water depletion minus drainage. Presalinization of the soil decreased yields in proportion to the salinity imposed, the decrease being associated with reductions in evapotranspiration caused by reduced soil water depletion as compared to the nonsalinized treatments.Contribution from Utah State University, Department of Soil Science and Biometeorology, in cooperation with Utah Agr. Exp. Sta., Logan, Utah 84 322. Journal Paper No. 2188. Supported in parts by Grants No. C-5189, Consortium for International Development and No. B-121-UT, Utah Water Res. Lab. and USDI, Office of Water Res. and TechnologyProfessor, Associate Professor, and Research Assistants, respectively     

国内外甜菜生产与机械化收获分析

甜菜作为主要的糖料作物,近年来其生产与机械化收获已呈现出蓬勃发展的势头,本文阐述了甜菜在世界主要区域的种植生产与分布情况以及在我国的种植分布情况,简要分析了甜菜的人工收获、分段收获和联合收获的机械化收获历程.阐述了国内外甜菜机械化收获的现状和发展趋势,并结合我国甜菜机械化收获当前的实际情提出了甜菜机械化收获发展的措施和建议.     

Yield and water relations of wheat as influenced by irrigation and depth of tillage

Summary Development of a ploughpan has been reported in Bangladesh for almost all ploughed soils which are puddled for transplanted rice cultivation. Field information on the water requirement of dryland crops such as wheat and the effects of loosening the dense layer on crop yield and water use efficiency are very limited. Field experiments were, therefore, conducted in the grey floodplain soil of Sonatala series (Aeric Haplaquept) to study the irrigation and tillage effects on the yield and water relations of wheat (Triticum aestivum L. cv. Sonalika). The split plot design experiment comprised four irrigation treatments in the mainplots viz. W₀ = no irrigation, W₁ = irrigation of 5 cm at 4 weeks after planting, W₂-W₁ + irrigation(s) of 5 cm each at irrigation water to cummulative pan evaporation (IW/CPE) ratio of 0.75 and W₃- W₁ + irrigation(s) of 5 cm eacht at IW/CPE ratio of 0.50. The sub-plot tillage depth treatments were: A-7.5 cm (traditional), B-15 cm, C-22.5 cm, D-22.5 cm practised in alternate wheat seasons. Measurements were made of grain and straw yield, soil water depletion and water expense efficiency.Irrigation had no effect on grain or straw yield. Tillage to 15 cm increased wheat yield by about 15% over traditional depth to ploughing. In general, deep tillage coupled with one irrigation at four weeks after planting produced the largest wheat yield.Soil water depletion (SWD) in the 0–90 cm profile was greatest in the treatment receiving two irrigations, one at 4 weeks and again at IW/CPE ratio of 0.50. The average SWD in this treatment was 113 in 1982–83 and 82 mm in 1983–84. Plots receiving traditional tillage (7.5 cm) had the greatest SWD. Total water expense were the greatest in treatments receiving three irrigations. The maximum water expense efficiency (WEE) of wheat was observed in the non-irrigated plots in 1982–83 and 1983–84, respectively. Deep tillage treatments, in general, had significantly greater WEE than those under traditional ploughing. Intensive irrigation and efficient soil and water management are important factors in enhancing crop productivity. The former not only permits judicious water use but also better utilization of other production factors thereby leading to increased crop yield which, in turn, helps stabilize the farming economy. The best way to meet increasing demand for water is to adopt efficient water management practices to increase water use efficiency.Irrigation should aim at restoring the soil water in the root zone to a level at which the crop can fully meet its evapo-transpiration (ET) requirement. The amount of water to be applied at each irrigation and how often a soil should be irrigated depend, however, on several factors such as the degree of soil water deficit before irrigation, soil types, crops, and climatic conditions (Chaudhury and Gupta 1980).Knowledge of movement of water through the soil is imperative to efficient water management and utilization. The presence of a dense pan impedes water movement into the sub-soil. As a result, the top soil becomes saturated by irrigation and sensitive dryland crops can fail as this plough layer impedes the penetration of roots into deeper soil layers and decreases water extraction. Crops growing in these soils often undergo severe water stress within 5–8 days after rainfall or irrigation (Lowry et al. 1970). Due to decrease rates of water flow, the lower soil layer may remain unsaturated and as a result, the recharge and soil water storage in the profile are considerably decreased (Sur et al. 1981).In Bangladesh, ploughpans develop to varying degree in almost all ploughed soils (Brammer 1980). They are particularly marked in soils which are puddled for transplanted rice cultivation where the pan is usually only 8–10 cm below the soil surface and 3–5 cm thick. Its presence is generally regarded as advantageous for cultivation of transplanted rice in that it prevents excessive deep percolation losses of water. But in the same soil this cultivation for a subsequent dryland crop would adversely affect yield. A slight modification of the plough layer could enable good yields of both rice and a dryland crop to be obtained in the same soil in different seasons (Brammer 1980). The sub soils have a good bearing capacity, both when wet and dry and the pan can easily be reformed, if desired, for cultivating transplanted rice after a dryland crop like wheat.Professor of Soil Science, Dhaka University, Dhaka, Bangladesh     

Response of sugar beet to non-uniform irrigation

Summary A field experiment was conducted using a linear-move irrigation machine to test the interactive effects of irrigation uniformity, a representative length of nonuniformity and water quality on crop yield and growth responses. Christiansen's uniformity coefficient values of 60, 80, and 90% were achieved with a sinusoidal pattern of applied water superimposed on the 60 and 80% uniformity treatments. Two wave-lengths 2.4 m (S) and 4.9 m (L), were used. Water qualities used were: 0.3 dS m^-1 and 3 to 5 dS m^-1. Results showed that both the magnitude and the scale of the nonuniformity affect the water use efficiency. Sugar yields were not affected by water quality. Yields on a row basis were significantly correlated to applied water in the 60% uniformity, long scale length (60-L) treatment.     

Modelling uptake of Na and Cl by tomato in closed-cycle cultivation systems as influenced by irrigation water salinity

The aim of the present investigation was to simulate the uptake concentrations (weights of ion per volume of water absorbed) of Na⁺ and Cl⁻ in hydroponic tomato crops as a function of the NaCl concentration in the root zone. An empirical model was calibrated and validated, which can be incorporated into on-line operating decision support systems aimed at optimizing the nutrient supply and minimizing the discharge of drainage solution in tomato crops grown in closed-cycle hydroponic systems. Three experiments were conducted, of which one was carried out to calibrate the model using irrigation water with NaCl concentration ranging from 0 to 14.7 mol m⁻³ while the other two experiments were commissioned to validate the model within either a low (0.5-2 mol m⁻³) or a high (1.2-12 mol m⁻³) concentration range. The model could successfully predict the uptake concentration of Na⁺, but Cl⁻ could not be simulated by this model at external Cl⁻ concentrations lower than 10 mol m⁻³. The results indicate that Na⁺ is excluded actively and effectively by the tested tomato cultivar even at low external Na⁺ concentrations, while Cl⁻ is readily taken up at low concentrations, particularly during the initial growing stages. Due to the efficient exclusion of Na⁺ by tomato, the Na⁺ concentration in the root environment increased rapidly to extremely high levels even when the Na⁺ concentration in the irrigation water was relatively low. These results indicate that tomato genotypes characterized by high salt-exclusion efficiency, require irrigation water with a very low NaCl concentration, if they are grown in closed hydroponic systems and the drainage water is not flushed periodically. To maintain Na⁺ at levels lower than 19 mol m⁻³ in the root zone of the tomato hybrid ‘Formula’ in closed hydroponics, a maximum acceptable Na⁺ concentration of 0.53 mol m⁻³ was estimated for the irrigation water.     

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.     

Wheat root distribution,water extraction pattern and grain yield as influenced by time and rate of irrigation

The effect of first irrigation (26, 40 and 54 days after seeding) and the rate of irrigation (5.5, 7.5 and 9.5 cm) applied subsequently at $\text{IW}\text{E}{}_{\mathrm{<mtext>pan</mtext>}}$ ratio of 0.9 on wheat root distribution, water extraction pattern and grain yield was studied on a barrier-free, sandy loam soil. The crop developed a more extensive root system when the first irrigation was applied after 26 days than after 40 and 54 days. With the first irrigation on the 26th day, the crop, receiving subsequent irrigations less frequently but at a heavier rate, developed a deeper root system than the crop receiving frequent, light irrigations. The water extraction pattern corresponded with the root distribution pattern. A relatively small difference in root density in the deeper layers caused a greater difference in soil water content than in the upper layers. Light and frequent irrigations produced maximum grain yields. However, for developing an extensive root system and enhancing water utilization in the subsoil, an early, light irrigation with subsequent irrigations applied less frequently at a relatively heavier rate seems desirable.     

Seed composition is influenced by irrigation regimes and cultivar differences in soybean

In the midsouth USA, soybean is produced either under irrigated or non-irrigated conditions. The objective of this experiment was to show the utility of supplemental irrigation as an alternative to full-season and non-irrigation to achieve high yield and high seed composition. The effects of irrigation and cultivar differences on soybean yield and seed composition were conducted. Two cultivars (Dwight and Freedom) and three irrigation regimes (full-season irrigation, FS; reproductive stage/supplemental irrigation, RI; and non-irrigation, NI) were used. Protein percentage was higher in Dwight under FS and RI than NI. In Freedom, protein percentage was higher under NI than under FS and RI. Under NI, Freedom had higher protein percentage than Dwight, especially in 2004, but lower oil in 2003 and 2004. Cultivars showed significant differences in fatty acids. Yield in Freedom under FS and RI was not significantly different. Nitrogen fixation was substantially higher under NI conditions. The results indicate that irrigation management and cultivar selection significantly affect seed composition and yield. Protein increase in Freedom under non-irrigated conditions may benefit producers for high protein seed under dry-land conditions. Supplemental irrigation at the reproductive stage may be a possible alternative for full season irrigation for the cultivar Freedom. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.     

Growth of faba bean (Vicia faba L.) as influenced by irrigation water salinity and time of salinization

A greenhouse study was conducted to investigate the response of faba bean (Vicia faba L.) to water salinity applied at different times of salinization. Faba beans were grown on loamy sand in pots and irrigated daily with modified half-strength Hoagland's solution. Salinization of the nutrient solution with NaCI and CaCl₂ (2:1 molar ratio) provided four treatment solutions with electrical conductivities of 2, 6, 10 and 14 dS m⁻¹ and was imposed on the tenth day from planting, and continued until day 30 (T1), from day 30 until day 50 (T2) and from day 50 to day 70 (T3) using a randomized block factorial design with five replications. The results indicated that faba bean was more sensitive to salinity during the vegetative stage and less sensitive at later stages. Water salinity significantly reduced the grain yield and grain number but did not affect grain weight. Vegetative growth decreased significantly by salinity stress during the three salinization periods but was more serious at the first stage.     

Forage production of cool season pasture grasses as related to irrigation

A significant portion of the irrigated acreage in the intermountain western U.S. is comprised of cool season grass pastures. Droughts, coupled with increasing demands for limited water supplies in the region, have decreased the water volumes available for irrigating these pastures and other crops. Consequently, relationship between crop yield and irrigation (water production functions) should be defined for various species and cultivars to help growers and water managers make appropriate selections based on water availability.During a 3-year study on the Colorado Plateau, a line-source irrigation system was used to evaluate the relationship between applied water and dry forage production of orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), meadow brome (Bromus riparius Rehmann), smooth brome (Bromus inermis Leyss.), two cultivars of intermediate wheatgrass (Elytrigia intermedium [Host] Nevski), crested wheatgrass (Agropyron cristatum L. Gaertn. X desertorum [Fisch. ex Link] J.A. Schultes) and perennial ryegrass (Lolium perenne L.). Irrigation treatments, including precipitation, ranged from 457 to 970 mm in 1996, 427 to 754 mm in 1997 and 490 to 998 mm in 1998. There was a positive linear relationship between yield and irrigation for all cultivars when averaged over all years but the relationships varied between cultivars and years. Orchardgrass, meadow brome and tall fescue produced more dry forage than the other grasses at the highest irrigation levels in all years. These grasses also produced the greatest rates of yield increase per unit of irrigation (average of 0.0129 Mg ha⁻¹ mm⁻¹) and exhibited greater yield stability from year to year than the other grasses at irrigation levels above 700 mm. The intermediate wheatgrasses produced more forage than the other grasses under limited irrigation (less than 600 mm) but the average production rate with irrigation (0.0066 Mg ha⁻¹ mm⁻¹) was only about half that of the aforementioned grasses. The average rate of forage produced per mm of irrigation was intermediate in the smooth brome (0.0096 Mg ha⁻¹) and lowest in the crested wheatgrass and perennial ryegrass (0.0048 and 0.0034 Mg ha⁻¹, respectively). These results suggest that orchardgrass and meadow brome be included in irrigated pastures receiving more than 700 mm of water annually while the intermediate wheatgrasses be selected for pastures receiving an annual water application of less than 700 mm.     

Timing of limited irrigation and N-injection for grain sorghum

When subsurface irrigation sources are lacking in humid and subhumid regions, high yearly precipitation may allow for storage of surface water in farm ponds and lakes for irrigation. Irrigation at selected growth stages may avoid critical stress for crops with some drought tolerance, such as grain sorghum [Sorghum bicolor (L.) Moench]. Because grain sorghum is responsive to N, injecting fertilizer N through the irrigation system also may improve production. The objective of this study was to determine the effect of timing of limited-amount irrigation and N fertigation on grain sorghum yield; yield components; grain N content; and N uptake at the 9-leaf, boot, and soft dough stages. The experiment was conducted from 1984 to 1986 on a Parsons silt loam (fine, mixed, thermic, Mollic Albaqualf). The experiment was designed as a 6 × 2 factorial plus two reference treatments. Six timings for irrigation were targeted at the 9-leaf (9L), boot (B), soft dough (SD), 9L-B, 9L-SD, and B-SD growth stages. N application systems were either 112 kg N ha^–1 surface-banded preplant or 56 kg N ha^-1 preplant and 56 kg N ha^–1 injected through the irrigation at a rate of 28 kg N ha^–1 per 2.5 cm of irrigation. Two reference treatments included were one receiving N but no irrigation and one receiving neither N nor irrigation. In 1984, irrigation generally increased grain sorghum yield by nearly 1 Mg ha^–1. However, yield was not affected by selection of irrigation timing, N application method, or the interaction of the two factors. This was partly because early irrigations increased kernels/head, whereas later irrigations increased kernel weight. Above average rainfall during the growing season, especially just prior to the 9-leaf, boot, and soft dough growth stages, resulted in no irrigations in 1985. In 1986, yield was increased by early (9-leaf) irrigations as compared to soft dough irrigations. Early irrigations resulted in higher kernels/head; however, rainfall after the soft dough irrigation may have masked any treatment effect on kernel weight. As in 1984, N application method did not affect grain sorghum yields, even though yield was reduced to less than 3 Mg ha^–1 with no N nor irrigation. In both 1984 and 1986, N uptake at succeeding growth stages appeared to respond to irrigations made at previous growth stages. Injecting half of the fertilizer N through the irrigation system did not affect N uptake compared to applying all N preplant. The lack of response to fertigation may be related to the low leaching potential of the soil used in this study.Contribution No. 92-606-J, Kansas Agricultural Experiment Station     

Real-time adaptive irrigation scheduling under a limited water supply

The problem of real-time irrigation scheduling under limited water supply is considered. The goal is to develop an irrigation operation policy which maximizes crop yields and is responsive to current season changes in weather and other variables. Because irrigation decisions are sequential and dependent on crop and soil water status, and also because crop yields can only be known at the end of the season, the decisions are arrived at by a two-stage process. In the first or the design stage, irrigations are planned for the entire season at weekly intervals using historical data and an optimal irrigation scheduling model. In the second stage, the decisions for the subsequent weeks are revised each week after updating the status of the system with real time data up to that week and solving the irrigation optimization model once again for the new conditions. Thus, each week an irrigation decision is made, the entire planning horizon is kept in view. The procedure is illustrated by application to a case study.     

Effects of limited irrigation on lettuce and chinese cabbage yields

Summary Yield response of lettuce (Lactuca sativa L.) and Chinese cabbage (Brassica campestris L. Group pekinensis) to eight different drip irrigation rates was determined in 1980–1984 at Lalamilo, Hawaii. Treatments were arranged in a gradient irrigation design replicated three times and were irrigated daily with amounts ranging from 0.76 mm to 6.09 mm. Yield response from a 0 treatment, equal to rainfall, was also measured. Marketable yield increased linearly with increased water application up to 49.7 Mg/ha for lettuce and 73.1 Mg/ha for Chinese cabbage with an associated seasonal evapotranspiration of 205 mm and 209 mm for lettuce and Chinese cabbage, respectively. The relationship between deficit relative yield (yield divided by maximum yield) and deficit relative evapotranspiration (evapotranspiration divided by maximum evapotranspiration) was linear with a deficit response coefficient of 1.07 for lettuce and 1.35 for Chinese cabbage. Marketable percentage of total potential biomass production decreased linearly with a decrease in marketable yield. Lettuce head size also decreased linearly with a decrease in marketable yield. Water use efficiency (yield divided by water applied) was 24 and 36 kg/m3 of water for lettuce and Chinese cabbage, respectively.     

Design of a farm layout for irrigation with limited discharges

In order to improve the irrigation efficiencies of small farms employing cavity wells for their water supply, an experimental study was conducted at the Central Soil Salinity Research Institute, Karnal. The cavity wells of the Karnal region do not have any discharge regulating devices for improving the irrigation efficiencies. The only way of improving these efficiencies is by designing an efficient irrigation layout, so that uniform water application is accomplished. The present study involves field determination of the opportunity time at each point along the border from advance and recession curves and computing the depth of cumulative infiltration from the infiltration rate curve. The irrigation efficiencies are also calculated from soil moisture measurements made before and after each irrigation.The results of this study show that a realistic field assessment of the irrigated border efficiencies is obtained through a soil moisture measurement procedure. The procedure, based on opportunity time and infiltration, overestimates the irrigation efficiencies due to the empirical nature of the infiltration equation. For small farms, with a limited discharge of 10 l/s, an irrigation layout of borders of 50–70 m in length and 6–8 m in width is recommended.     

Simulated effects of water table and irrigation scheduling as factors in cotton production

Summary Irrigation is essential for economic production of some crops in semiarid climates. Benefits from irrigation may be partially offset by detrimental effects of rising water tables and salinization. Drainage systems are usually installed when the water table rises to the root zone, but installation of a drainage system and safe disposal of drainage water are expensive. The long-term consequences of a high saline water table on crop production, particularly as related to irrigation scheduling, has not been firmly established. A multiseasonal transient state model, known as the modified van Genuchten-Hanks model, was used to simulate cotton (Gossypium hirsutum L.) production using a three or four in-season irrigation schedule (3irr or 4irr) under both free drainage and water table conditions. Under drainage conditions, irrigation scheduling to avoid applying more water than the soil water-holding capacity during any irrigation event is important, whereas this factor is less important under water table conditions. Excess water during an irrigation causes a rise in the water table, but this water remains available for later crop use which lowers the water table. In the presence of a water table the simulations indicate, (1) higher yields are achieved by applying less irrigation during the crop season and more during the preirrigation for salt leaching purposes, (2) annual applied water must equal evapotranspiration to avoid long-term water table rise or depletion, and (3) high cotton yields can be achieved for several years even if the water table is saline and no drainage occurs if the irrigation water is low in salinity.     

Corn grain yield as influenced by timing of evapotranspiration deficits

Summary Field experiments were conducted at two sites with differing root zone water holding capacities. Corn grain yield was measured as a function of water management treatments. Stress development in given treatments was generally limited to one of three periods (planting-to-12-leaf, 12-leaf-to-blister-kernel, and blister-kernel-to-physiologic-maturity) during the growing season. Stress levels were defined as low (L), moderate (M) or severe (S) and were based on degree of soil water depletion and an allowable level of leaf xylem pressure depression in midafternoon.Yield vs seasonal ET exhibited linear relationships. Slope of an estimated upper bound function was 0.28 T/ha-cm of water use. Maximum seasonal grain yields were consistently produced with an L-L-L stress sequence allowing about 30–40% depletion of the root zone available water capacity (to 122 cm depth) between irrigations. A trickle irrigated treatment that maintained near zero soil water potential averaged about 4% more yield than the 30–40% depletion criteria, but this difference was not significant at P=0.05.Results, when normalized as relative yield (Y/Y_m) vs relative seasonal evapotranspiration (ET/ET_m), indicated an upper bound slope of 1.50% yield loss per 1% decline in seasonal ET from the ET_m level. When stress was concentrated in the 12 leaf to blister kernel period, the yield reduction slope was 2.60%.Average observed Y/Y_m ratios were 0.95 for M-L-L, 0.92 for S-L-L, 0.85 for L-M-L, 0.62 for L-S-L, 0.62 for L-S-L, 0.90 for L-L-M, and 0.69 L-L-S stress sequences.If water stress is limited to one growth period per season an upper bound yield attainment is likely if irrigations relieve stress before available root zone storage capacity is 90–95% depleted in the planting to 12 leaf period, 80–90% depleted in 12 leaf to blister kernel period or when a programmed depletion to 100% available water exhaustion near physiological maturity is achieved in the later grain fill period.Yield reduction of less than 5 % from potential levels appears likely in the climatic setting of this study when root zone available water depletions are limited to 60–70% in the early vegetative period (assumes near field capacity moisture at planting), 30–40% in the 12 leaf to blister kernel period, and 50–60% in the later grain fill period.This work was supported by North Dakota Agricultural Experiment Station Projects 1432 and 1435 and by funds provided by the U.S. Department of Interior, Water and Power Resources Service     

Yield and quality of two tomato (Solanum lycopersicum L.) cultivars as influenced by drip and furrow irrigation using waters having high residual sodium carbonate

Performance of tomato when irrigated with sodic waters particularly under drip irrigation is not well known. A field experiment was conducted for 3 years to study the response of tomato crop to sodic water irrigation on a sandy loam soil. Irrigation waters having 0, 5 and 10 mmol_c L⁻¹ residual sodium carbonate (RSC) were applied through drip and furrow irrigation to two tomato cultivars, Edkawi (a salt tolerant cultivar) and Punjab Chhuhara (PC). High RSC of irrigation water significantly increased soil pH, ECe and exchangeable sodium percentage progressively; the increases were higher in furrow compared to drip irrigation. Effect of high RSC on increasing bulk density and decreasing infiltration rate of soil was also pronounced in furrow-irrigated plots. Higher soil moisture and lower salinity near the plant was maintained under drip irrigation than under furrow irrigation. Performance of the two cultivars was significantly different; pooled over 2002–03 and 2003–04 seasons, PC yielded 38.8 and 30.0 Mg ha⁻¹ and Edkawi yielded 31.8 and 22.9 Mg ha⁻¹ under drip and furrow irrigation, respectively. At RSC10, cultivar PC produced 38 and 46% higher fruit yield than cultivar Edkawi under drip and furrow irrigation, respectively. Reduction in fruit yield at higher RSC was due to lower fruit weight under drip irrigation and due to reduced fruit number as well as fruit weight under furrow irrigation. Decrease in fruit weight was more pronounced in cultivar Edkawi than in cultivar PC. Increase in RSC lowered quality of the fruits except the ascorbic acid content. High RSC under drip irrigation, in general, had lesser deteriorating effect on the fruit quality particularly for cultivar PC than under furrow irrigation. For obtaining high tomato yield and better-quality fruits using high RSC sodic waters, drip irrigation should be preferred over furrow irrigation. Better performance of local cultivar PC compared to Edkawi at medium and high RSC suggests that cultivars categorized as tolerant to salinity should be evaluated in the sodic environment particularly when irrigated with high RSC sodic waters.     

Deficit irrigation in a production setting: canopy temperature as an adjunct to ET estimates

Water available for agricultural use is declining worldwide as a result of both declining water resources and increasing application costs. Managing crop irrigation under conditions where the water need cannot be fully met represents the future of irrigation in many areas. On the southern high plains of Texas there is interest among producers to reduce the amount of water applied to cotton. In this study, a producer’s efforts to reduce water application to a cotton crop were assessed in terms of a comparison between evapotranspiration, rainfall, and irrigation that is widely used in the region. The producer was able to reduce water application to meet intended reductions relative to the evapotranspiration estimates but, depending on the method used for calculating the crop water need, he tended to over water the crop in two out of three intended deficit irrigation regimes. Analysis of continuously monitored canopy temperatures provided verification of over-irrigation. Continuously monitored canopy temperature is proposed as a useful adjunct to evapotranspiration approaches to deficit irrigation management.     

Water pillow irrigation compared to furrow irrigation for soybean production in a semi-arid area

Field studies were done in 2003 and 2006 to evaluate the performance of water pillow (WP) irrigation as an alternative to furrow irrigation (FI) for soybean growth in semi-arid climatic conditions. There were four irrigation treatments: two of which (FI and WP_1.0) were full irrigation, in that the water deficit in the soil profile (0.9 m) was brought to field capacity in 10-day intervals. The other two treatments (WP_0.75 and WP_0.50) were deficit irrigation treatments, and received 75% and 50% of WP_1.0 irrigation amount. The highest seed yield was achieved with the WP_1.0 treatment. Irrigation water use efficiency (IWUE) and water use efficiency (WUE) were influenced significantly by the irrigation methods and levels (P ≤ 0.05). The highest values of WUE and IWUE were obtained by the WP_0.75 and WP_0.50 treatment, respectively, in both study years. However, the smallest irrigation amount resulted in lower total yield for the WP_0.50 treatment, and is not recommended. In conclusion, the WP_0.75 treatment is recommended for soybean production in order to attain higher values of IWUE and WUE, and to conserve water and maximize yield with the same volume of water.