Potato water use and yield under furrow irrigation

Field experiments were conducted to study the effects of plant-furrow treatments and levels of irrigation on potato (Solanum tuberosum L.) water use, yield, and water-use efficiency. The experiments were carried out under deficit irrigation conditions in a sandy loam soil of eastern India in the winter seasons of 1991/92, 1992/93, and 1993/94. Two plant-furrow treatments and two levels of irrigation were considered. The two plant-furrow treatments were F₁ - furrows with single row of planting in each ridge with 45 cm distance between adjacent ridges, and F₂ - furrows with double rows of planting spaced 30 cm apart in each ridge with 60 cm distance between adjacent ridges. The two levels of irrigation (LOI) were I₁ - 0.9 IW/CPE and I₂ - 1.2 IW/CPE, where IW is irrigation water of 5 cm and CPE is cumulative pan evaporation. Treatment F₂ produced highest tuber yield in all years with average value of 10,610 kg ha ^-1 and 12,780 kg ha ^-1 at LOI of I₁ and I₂, respectively. On average, six irrigations with a total of 25 cm, and seven irrigations with a total of 30 cm were required for both treatments F₁ and F₂ at LOI of I₁ and I₂, respectively. Treatment F₂ resulted in a significantly higher number of branches and tubers per plant, foliage coverage and water-use efficiency for both irrigation levels than treatment F₁. Average daily crop evapotranspiration was found to range from 1.1 to 3.4 mm and from 1.2 to 3.9 mm for treatment F₁ and from 1.1 to 3.6 mm and from 1.2 to 4.0 mm for treatment F₂ at LOI of I₁ and I₂, respectively.     

Forage sorghum yield and water use efficiency under variable irrigation

The response of forage sorghum [Sorghum bicolor (L.) Moench] to three irrigation treatments in a semiarid environment was studied in the field for two seasons. Treatments were light frequent, moderate less frequent, and heavy infrequent irrigation, where irriga-tion water at 8 mm day^–1 was delivered every 7, 10, and 13 days, respectively. These irrigation regimes meant heavier water inputs with increasing irrigation frequency. Plant heights and leaf area indices of forage sorghum were higher in the frequently watered plots than in plots where irrigation water was delivered less frequently. Averaged over the two seasons, maximum dry matter (DM) yields were 16.3, 11.8, and 10.5 tonnes ha^–1 for frequent, intermediate, and infrequent irrigation regimes, respectively. Light, frequent irrigation resulted in a significantly higher water use efficiency (WUE) compared to the other two regimes, thus increasing the return from irrigation. These results suggest that in such semiarid environments, DM yields and WUE of forage sorghum could be increased by combining light irrigation with a short interval. Received: 6 February 1997     

Cotton yield and water use efficiency at various levels of water and N through drip irrigation under two methods of planting

The present investigation was undertaken to evaluate the effect of various levels of water and N application through drip irrigation on seed cotton yield and water use efficiency (WUE). In this experiment three levels of water (Epan 0.4, 0.3, and 0.2) and three levels of N (100, 75, and 50% of recommended N, 75 kg/ha) through drip were compared with check-basin method of irrigation under two methods of planting (normal sowing, NS; paired sowing, PS). The results revealed that when the same quantity of irrigation water and N was applied through drip irrigation system, it increased the seed cotton yield to 2144 from 1624 kg/ha (an increase of 32%) under check-basin method of irrigation. When the quantity of water through drip was reduced to 75%, the increase in seed cotton yield was 12%; however, when water was reduced to 50%, it resulted 2% lower yield than check-basin. The decrease in N through fertigation resulted in reduction in seed cotton yield at all the levels of water supply, but the magnitude of reduction was the highest at highest level of water supply. In paired sowing (PS), 20% higher seed cotton yield was obtained as compared with check-basin method under NS along with 50% saving of water. In paired sowing the sacrifice of 9% seed cotton yield as compared with NS resulted in saving of 50% water as well as the cost of laterals because there was one lateral for two paired rows. The WUE increased by 26% (22.1 from 17.6 kg/ha cm) in drip irrigation system when same quantity of water and N fertilizer was applied as compared with check-basin. WUE was not affected with quantity of water but decrease in rate of N caused a decrease in WUE at all the quantities of water applied. In general, WUE was higher in PS as compared with NS. The agronomic efficiency of nitrogen increased from 21.65 to 28.59 kg of seed cotton per kg of N applied when same quantity of water and N was applied through drip irrigation as compared with check-basin. However, decrease in quantity of water applied resulted in a decrease in agronomic efficiency of N but reverse was true for rates of N applied. When the same quantity of water and N was applied under both the methods of planting, PS produced 22% higher seed cotton yield and along with reduced cost owing to half the number of laterals required.     

不同喷灌水氮组合对马铃薯耗水、产量和品质的影响

为了探讨黑龙江省克山县圆形喷灌机条件下不同水氮组合对马铃薯的耗水规律、产量和品质的影响,同时确定节水、节肥、高产目标下适宜的水氮组合方式,试验设置了2个灌水水平:灌水总量W1(80 mm)和W2(100 mm);4个追氮量水平:F1(45 kg/hm²),F2(56.6 kg/hm²),F3(70 kg/hm²)和F4(86.6 kg/hm²);2个施氮频次:C1为块茎膨大期1次施入,C2为块茎膨大期分2次施入,并选择雨养区作为对照.结果表明:马铃薯全生育期耗水量为313~332 mm,块茎膨大期耗水量最大,占全生育期耗水总量63.4%~66.0%,幼苗期和块茎形成期是需水关键期,应结合马铃薯生长状况和当地雨水情况,适当进行补充灌溉;相比于其余处理,W2F4C2处理产量最高,达到46 525 kg/hm²;不同水氮组合间马铃薯的淀粉、维生素C、粗蛋白含量及商品薯率无显著差异,粗蛋白含量随着施氮量的增加呈现先降低后升高的趋势.综合比较,建议在黑龙江半湿润地区,可采用高水(100 mm)高肥(86.6 kg/hm²)高频次(块茎膨大期分2次施入)的方案.     

Soil microbial response, water and nitrogen use by tomato under different irrigation regimes

The objectives of this study were to investigate the effects of full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD) on plant biomass, irrigation water productivity (IWP), nitrogen use efficiency (NUE) of tomato, and soil microbial C/N ratio. The plants were grown in pots with roots split equally between two soil compartments in a climate-controlled glasshouse. During early fruiting stage, plants were exposed to FI, DI, and PRD treatments. In FI, both soil compartments were irrigated daily to a volumetric soil water content of 18%; in PRD, only one soil compartment was irrigated to 18% while the other was allowed to dry to ca. 7-8%, then the irrigation was shifted; in DI, the same amount of water used for the PRD plants was equally split to the two soil compartments. The results showed that, the FI treatment produced significantly higher dry biomasses of leaves, stems, and fresh weight of fruit and water productivity of aboveground dry biomass production than either DI or PRD, however, fruit IWP in DI was 25% higher than that of FI, and harvest index in DI and PRD were 50% and 22% higher than FI, respectively, for the 26% and 23% less water used in the DI and PRD, respectively, than the FI treatment. The DI treatment caused the smallest losses of N and highest N use efficiency by fruit. Both DI and PRD caused a significant increase in the soil microbial C/N ratio, meaning ratio of fungal biomass was high at low soil water contents. The result indicates that more work is needed to link the aboveground N uptake and the underground microbially mediated N transformation under different water-saving irrigation regimes.     

Cotton yield and applied water relationships under drip irrigation

Different irrigation scheduling methods and amounts of water ranging from deficit to excessive amounts were used in cotton (Gossypium hirsutum L.) irrigation studies from 1988 to 1999, at Lubbock, TX. Irrigation scheduling treatments based on canopy temperature (T_c) were emphasized in each year. Surface drip irrigation and recommended production practices for the area were used. The objective was to use the 12-year database to estimate the effect of irrigation and growing season temperature on cotton yield. Yields in the irrigation studies were then compared with those for the northwest Texas production region. An irrigation input of 58 cm or total water application of 74 cm was estimated to produce maximum lint yield. Sources of the total water supply for the maximum yielding treatments for each year averaged 74% from irrigation and 26% from rain. Lint yield response to irrigation up to the point of maximum yield was approximated as 11.4 kg ha⁻¹ cm⁻¹ of irrigation between the limits of 5 and 54 cm with lint yields ranging from 855 to 1630 kg ha⁻¹. The intra-year maximum lint yield treatments were not limited by water input, and their inter-year range of 300 kg ha⁻¹ was not correlated with the quantity of irrigation. The maximum lint yields were linearly related to monthly and seasonal heat units (HU) with significant regressions for July (P=0.15), August (P=0.07), and from May to September (P=0.01). The fluctuation of maximum yearly lint yields and the response to HU in the irrigation studies were similar to the average yields in the surrounding production region. The rate of lint yield increase with HU was slightly higher in the irrigation studies than in the surrounding production area and was attributed to minimal water stress. Managing irrigation based on real-time measurements of T_c produced maximum cotton yields without applying excessive irrigation.     

Evapotranspiration, seed yield and water use efficiency of drip irrigated sunflower under full and deficit irrigation conditions

Deficit irrigation occurrence while maintaining acceptable yield represents a useful trait for sunflower production wherever irrigation water is limited. A 2-year experiment (2003–2004) was conducted at Tal Amara Research Station in the Bekaa Valley of Lebanon to investigate sunflower response to deficit irrigation. In the plots, irrigation was held at early flowering (stage F1), at mid flowering (stage F3.2) and at early seed formation (stage M0) until physiological maturity. Deficit-irrigated treatments were referred to as WS1, WS2 and WS3, respectively, and were compared to a well-irrigated control (C). Reference evapotranspiration (ET_rye-grass) and crop evapotranspiration (ET_crop) were measured each in a set of two drainage lysimeters of 2 m × 2 m × 1 m size cultivated with rye grass (Lolium perenne) and sunflower (Helianthus annuus L., cv. Arena). Crop coefficients (K_c) in the different crop growth stages were derived as the ratio (ET_crop/ET_rye-grass).

Lysimeter measured crop evapotranspiration (ET_crop) totaled 765 mm in 2003 and 882 mm in 2004 for total irrigation periods of 139 and 131 days, respectively. Daily ET_crop achieved a peak value of 13.0 mm day⁻¹ at flowering time (stage F3.2; 80–90 days after sowing) when LAI was >6.0 m² m⁻². Then ET_crop declined to 6.0 mm day⁻¹ during seed maturity phase. Average K_c values varied from 0.3 at crop establishment (sowing to four-leaf stage), to 0.9 at late crop development (four-leaf stage to terminal bud), to >1.0 at flowering stage (terminal bud to inflorescence visible), then to values <1.0 at seed maturity phase (head pale to physiological maturity). Measured K_c values were close to those reported by the FAO.

Average across years, seed yield at dry basis on the well-irrigated treatment was 5.36 t ha⁻¹. Deficit irrigation at early (WS1) and mid (WS2) flowering stages reduced seed yield by 25% and 14% (P < 0.05), respectively, in comparison with the control. However, deficit irrigation at early seed formation was found to increase slightly seed yield in WS3 treatment (5.50 t ha⁻¹). We concluded that deficit irrigation at early seed formation (stage M0) increased the fraction of assimilate allocation to the head, compensating thus the lower number of seeds per m² through increased seed weight. In this experiment, while deficit irrigation did not result in any remarkable increase in harvest index (HI), water use efficiency (WUE) was found to vary significantly (P < 0.05) among treatments, where the highest (0.83 kg m⁻³) and the lowest (0.71 kg m⁻³) values were obtained from WS3 and WS1 treatments, respectively. Finally, results indicate that irrigation limitation at early flowering (stage F1) and mid flowering (stage F3.2) should be avoided while it can be acceptable at seed formation (stage M0).     

Potato evapotranspiration and yield under different drip irrigation regimes

A field experiment comparing different irrigation frequencies and soil matric potential thresholds on potato evapotranspiration (ET), yield (Y) and water-use efficiency (WUE) was carried out in a loam soil. The experiment included five treatments for soil matric potential: F1 (-15 kPa), F2 (-25 kPa), F3 (-35 kPa), F4 (-45 kPa) and F5 (-55 kPa) and six treatments for irrigation frequency: N1 (once every day), N2 (once every 2 days), N3 (once every 3 days), N4 (once every 4 days), N6 (once every 6 days) and N8 (once every 8 days). Results indicate that both soil matric potential and drip irrigation frequency influenced potato ET, Y and WUE. Potato ET increased as irrigation frequency and soil matric potential increased. Comparing soil water potential, the highest ET was 63.4 mm (32.1%) more than the lowest value. Based on irrigation frequency treatments, the highest ET was 36.7 mm (19.2%) more than the lowest value. Potato Y and WUE were also found to increase as irrigation frequency increased. Potato Y increased with an increase in soil water potential then started to decrease. The highest Y and WUE values were achieved with a soil matric potential threshold of -25 kPa and an irrigation frequency of once a day.Communicated by J. Ayars     

Effect of soil matric potential on tomato yield and water use under drip irrigation condition

Field experiment was carried out to investigate the effect of soil matric potential (SMP) on tomato yield, evapotranspiration (ET), water use efficiency (WUE) and irrigation water use efficiency (IWUE) under drip irrigation condition in North China Plain. The experiment included five treatments, which controlled SMP at 0.2 m depth immediately under drip emitter higher than −10 (S1), −20 (S2), −30 (S3), −40 (S4) and −50 kPa (S5), respectively, after tomato plant establishment. The results showed that different SMP affected irrigation amount and tomato ET. Irrigation amount decreased from 185 mm (S1) to 83.6 mm (S5) in 2004, and from 165 mm (S1) to 109 mm (S5) in 2005, respectively. The ET decreased from 270 mm (S1) to 202 mm (S5) in both years. However, it was found that SMP did not affect the tomato yield significantly, for the range of SMP investigated. Both WUE and IWUE increased as SMP decreased. The maximum WUE (253 and 217 kg/ha mm) and IWUE (620 and 406 kg/ha mm) were for S5 in 2 years, whereas the minimum WUE (178 and 155 kg/ha mm) and IWUE 261 and 259 kg/ha mm) were for S1 in 2004 and 2005. Based on the above results, therefore, it is recommended that if the tomatoes are well irrigated (SMP is higher than −20 kPa) during establishment, controlling SMP higher than −50 kPa at 0.2 m depth immediately under drip emitter can be used as an indicator for drip irrigation scheduling during following period of tomato growth in North China Plain.     

灌水量对烤烟产量和水分利用效率的影响

灌水时期不当或灌水量过大会降低烟叶的产量,同时造成水分的浪费,探究烟草适宜的灌水量至关重要。在蒸渗仪中开展试验,研究了不同灌水量对土壤水分、烤烟的水分利用效率和产量的影响。结果表明：烤烟 K326各处理不同土层含水率变化规律比较一致,（0,10]cm 土层含水率受气温、日照等气候因素较大;（10,20]cm 土壤含水率变化较剧烈;（20,60]cm 土壤含水率在整个生育期变化比较平缓,尤其在成熟后期各处理均出现不同程度的回升趋势,结合烤烟成熟期生理活动减弱、需水量减少,说明成熟期采取较小的灌水量比较适宜。成熟期烤烟的干物质产量在一定范围内随灌水量的增大而增加,如果继续加大灌水量将出现“报酬递减”现象。结合烟叶产量、烟株长势、耗水量和水分利用效率的结果,表明2700～3000 m3／hm2可以作为烤烟K326适宜的灌水量。在烤烟生产中,应均衡协调产量、水分利用效率与耗水量之间的关系,在高产前提下,适当减少灌水量,可达到既高产又节水的协调统一。     

Effect of irrigation and nitrogen on yield,yield components and water use efficiency of barley in Saudi Arabia

Water use efficiency and yield of barley were determined in a field experiment using different irrigation waters with and without nitrogen fertilizer on a sandy to loamy sand soil during 1994–1995 and 1995–1996. Depending upon different fertilizer treatments, the overall mean crop yield ranges for two crop seasons were: greenmatter from 19.48–55.0 Mg ha⁻¹ (well water) and 21.92–66.5 Mg ha⁻¹ (aquaculture effluent); drymatter from 6.86–20.69 Mg ha⁻¹ (well water) and 7.87–20.90 Mg ha⁻¹ (aquaculture effluent); biomass from 4.12–21.31 Mg ha⁻¹ (well water) and 8.10–19.94 Mg ha⁻¹ (aquaculture effluent) and grain yield from 2.12–5.50 Mg ha⁻¹ (well water) and 3.25–7.25 Mg ha⁻¹ (aquaculture effluent). The WUE for grain yield was 3.37–8.74 kg ha⁻¹ mm⁻¹ (well water) and 5.17–11.53 kg ha⁻¹ mm⁻¹ (aquaculture effluent). The WUE for total biomass ranged between 6.55–33.88 kg⁻¹ ha⁻¹ mm⁻¹ (well water) and 12.88–31.70 kg ha⁻¹ mm⁻¹ (aquaculture effluent). The WUE for drymatter was 10.91–32.90 kg ha⁻¹ mm⁻¹ (well water) and 12.51–33.22 kg ha⁻¹ mm⁻¹ (aquaculture effluent). It was found that grain yield and WUE obtained in T-4 and T-5 irrigated with well water and receiving 75 and 100% nitrogen requirements were comparable with T-4 and T-5 irrigated with aquaculture effluent and receiving 0 and 25% nitrogen requirements. In conclusion, application of 100 to 150 kg N ha⁻¹ for well water and up to 50 kg N ha⁻¹ for aquaculture effluent irrigation containing 40 Mg N l⁻¹ would be sufficient to obtain optimum grain yield and higher WUE of barley in Saudi Arabia.     

Effects of irrigation regimes on the yield and water use of strawberry

Summary Strawberry plants (Fragaria x annanasa D. cv Chandler) were grown in field plots and in drainage lysimeters under controlled soil moisture regimes. Four irrigation treatments were established by watering the plants when soil water potential reached -0.01, -0.03,-0.05 and -0.07 MPa. The maximum yield was attained at -0.01 MPa soil water potential. Differences in yield were caused by both changes in the number of fruits per plant and in the fresh weight per fruit. Yield reductions were associated with reductions in total assimilation rate resulting from the decreased assimilatory surface area in plants irrigated at lower soil water potentials. The crop water production function calculated on a fruit fresh weight basis resulted in a yield response factor (K _y) of 1.01.     

Grain yield and water use efficiency of two types of winter wheat cultivars under different water regimes

To improve grain yields of winter wheat and water-use efficiency in the water-shortage region of the North China Plain (NCP), field experiments involving three irrigation levels and two types of winter-wheat cultivars (Shijiazhuang 8 and Xifeng 20, with moderate and strongly drought tolerance, respectively) were conducted over three growing seasons with different levels of precipitation. The results showed that irrigation significantly improved the grain yield of both wheat cultivars. The response of grain yield was largest in the dry year, followed by the normal and wet years. Shijiazhuang 8 responded more strongly than Xifeng 20. Compared to aboveground biomass under no irrigation treatment, the aboveground biomass of Shijiazhuang 8 and Xifeng 20 improved by 87.0% and 57.8%, respectively, in a dry year, by 27.2% and 18.3%, respectively, in a normal year, and by 13.7% and 11.7%, respectively, in a humid year when irrigation were applied twice. The total water use (TWU) of the two cultivars also increased upon irrigation. The increase was more pronounced in the dry year than in the normal or humid years. However, there were no significant differences in the TWUs of the two cultivars. The water-use efficiency at grain-yield level (WUE_y) of Shijiazhuang 8 increased significantly upon irrigation in the dry year, did not change in the normal year, and showed a clear decline in the humid year, while the WUE_y of Xifeng 20 was reduced by irrigation in each of the three growing seasons. The harvest index (HI) was not altered by irrigation but it did vary by growing season. The HI of Shijiazhuang 8 was always higher than that of Xifeng 20. A positive correlation was found between both the WUE_y and the water-use efficiency at the aboveground-biomass level (WUE_bm) and the HI. This suggests that the changes in WUE_y as a result of irrigation are mainly due to changes in the WUE_bm and that the differences in WUE_y between the two cultivars were due to differences in WUE_bm and HI. These results suggest the following. (1) The TWUs in the two cultivars were roughly equal, although their levels of drought tolerance differed. (2) A wheat cultivar with moderate drought tolerance is expected to be more suitable for the semi-arid region of the NCP. The variety with strongly drought tolerance was able to keep its biomass high and to maintain grain yield under serious drought stress. (3) In order to both increase grain yield and WUE_y, two irrigations in a dry year, one irrigation in a normal year, and no irrigation in a humid year will give optimal results in the studied region.     

Corn crop response under managing different irrigation and salinity levels

Non-uniformity of water distribution under irrigation system creates both deficit and surplus irrigation areas. Water salinity can be hazard on crop production; however, there is little information on the interaction of irrigation and salinity conditions on corn (Zea Mays) growth and production. This study evaluated the effect of salinity and irrigation levels on growth and yield of corn grown in the arid area of Egypt. A field experiment was conducted using corn grown in northern Egypt at Quesina, Menofia in 2009 summer season to evaluate amount of water applied, salinity hazard and their interactions. Three salinity levels and five irrigation treatments were arranged in a randomized split-plot design with salinity treatments as main plots and irrigation rates within salinity treatments. Salinity treatments were to apply fresh water (0.89 dS m⁻¹), saline water (4.73 dS m⁻¹), or mixing fresh plus saline water (2.81 dS m⁻¹). Irrigation treatments were a ratio of crop evapotranspiration (ET) as: 0.6ET, 0.8ET, 1.0ET, 1.2ET, and 1.4ET. In well-watered conditions (1.0ET), seasonal water usable by corn was 453, 423, and 380 mm for 0.89EC, 2.81EC and 4.73EC over the 122-day growing season, respectively. Soil salt accumulation was significantly increased by either irrigation salinity increase or amount decrease. But, soil infiltration was significantly decreased by either salinity level or its interaction with irrigation amount. Leaf temperature, transpiration rate, and stomata resistance were significantly affected by both irrigation and salinity levels with interaction. Leaf area index, harvest index, and yield were the greatest when fresh and adequate irrigation was applied. Grain yield was significantly affected in a linear relationship (r² ≥ 0.95) by either irrigation or salinity conditions with no interaction. An optimal irrigation scheduling was statistically developed based on crop response for a given salinity level to extrapolate data from the small experiment (uniform condition) to big field (non-uniformity condition) under the experiment constraints.     

Water use and yields of sugarbeet grown under every-other-furrow irrigation with different irrigation intervals

The water stress effects of every-other-furrow irrigation on yield may be alleviated by more frequent irrigation intervals. This research was conducted to determine yield and water use efficiency of sugarbeet under every-other-furrow and every-furrow irrigations at different irrigation intervals. Every-other-furrow irrigation (EOFI) at 10-day irrigation intervals used a smaller amount of irrigation water, but some yield reduction occurred. However, frequent EOFI at 6-day intervals produced a similar root yield to that of every-furrow irrigation (EFI) at 10-day intervals and saved an average of 23%v of irrigation water. Also, 73% relative applied water may produce 16% more yield if water was applied as EOFI rather than as EFI. Furthermore, an average of 43% higher water use efficiency was obtained in more frequent EOFI compared with EFI at less frequent intervals.     

Tomato root distribution, yield and fruit quality under different subsurface drip irrigation regimes and depths

Tomato rooting patterns, yield and fruit quality were evaluated in a field trial where three irrigation regimes [0.6 (DI), 0.9 (DII) and 1.2 ET_c (DIII)] and three drip irrigation depths [surface (R0), subsurface at 20 cm depth (RI) and subsurface at 40 cm depth (RII)] were imposed following a split-plot experimental design, with four replications. The behaviour of the root system in response to the irrigation treatments was evaluated using minirhizotrons installed between two plants, near the plant row. Root-length intensity (L _a)—length of the root per unit of minirhizotron surface area (cm cm⁻²)—was measured at four crop stages. For all sampling dates, none of the factors studied were found to influence L _a or rooting depth significantly or the interaction between treatments. For all treatments most of the root system was concentrated in the top 40 cm of the soil profile, where the root-length density ranged from 0.5 cm cm⁻³ to 1.4 cm cm⁻³ . The response of tomato fruits to an increase in the water applied was similar in quantitative and qualitative terms for the different drip irrigation depths. Water applied by drip irrigation had the opposite effect on commercial yield (t ha⁻¹) and soluble solids (°Brix) (r=−0.82, P<0.001), however, yield in terms of total soluble solids (t ha⁻¹) was the same for the 0.9 and 1.2 ET_c. The increase in commercial yield can be described by the equation      

The effect of drip line spacing, irrigation regimes and planting geometries of tomato on yield, irrigation water use efficiency and net return

This study was conducted in order to determine the effect of drip line spacing, irrigation regimes and planting geometries of tomato on yield, irrigation water use efficiency (IWUE) and net return. The experiments were carried out in the conditions of Eskisehir in Central Anatolian part of Turkey, between 2003 and 2005, with cv. Dual Large F1 tomatoes (Lycopercion esculentum L). The maximum yield of 121.1 t ha⁻¹ was obtained from the treatment in which both the lateral and row spacing were 1 m, and irrigated with water amount based on the percentage of canopy cover. The seasonal irrigation water amount of the treatment was 551 mm. Tomatoes yield of 109.9 t ha⁻¹ was obtained under conditions of 491 mm seasonal irrigation water applied for the 2-m lateral spacing in which two plant rows (twin rows) were planted 0.35 m on either side of the lateral with a row spacing of 0.70 m across the drip lateral and 1.30 m in the interrow between each set of twin rows. Although water saving of 60 mm and investments economy of 40% were provided from the twin-row design, the yearly return of the design including one lateral for each row was US$ 1590 ha⁻¹ higher than that the return of the twin-row design. The method of determination of irrigation water amount based on the percentage of canopy cover appeared to be the most reasonable and effective one in terms of the yield and IWUE. On the other hand, the maximum irrigation water use efficiency (22.3 kg m³) was obtained from 2-m lateral spacing and the percentage of canopy cover for calculation of the amount of irrigation water applied. Thus, canopy cover may be used successfully at any lateral design conditions.     

Effect of full and limited irrigation amount and frequency on subsurface drip-irrigated maize evapotranspiration,yield, water use efficiency and yield response factors

The objectives of this study were to: (1) to evaluate the effects of subsurface drip irrigation amount and frequency on maize production and water use efficiency, (2) develop production functions and quantify water use efficiency, and (3) develop and analyze crop yield response factors (Ky) for field maize (Zea mays L.). Five irrigation treatments were imposed: fully irrigated treatment (FIT), 25 % FIT, 50 % FIT, 75 % FIT, rainfed and an over-irrigation treatment (125 % FIT). There was no significant (P > 0.05) difference between irrigation frequencies regarding the maximum grain yield; however, at lower deficit irrigation regime, medium irrigation frequency resulted in lower grain yield. There was a decrease in grain yield with the 125 % FIT as compared to the FIT, which had statistically similar yield as 75 % FIT. Irrigation rate significantly impacted grain yield in 2005, 2006 and 2007, while irrigation frequency was only significant during the 2005 and 2006 growing seasons (two dry years) and the interacting effect was only significant in the driest year of 2005 (P = 0.006). For the pooled data from 2005 to 2008, irrigation rate was significant (P = 0.001) and irrigation frequency was also significant (P = 0.015), but their interaction was not significant (P = 0.207). Overall, there were no significant differences between irrigation frequencies in terms of grain yield. Ky had interannual variation and average seasonal Ky values were 1.65, 0.91, 0.91 and 0.83 in 2005, 2006, 2007 and 2008, respectively, and the pooled data (2005–2008) Ky value were 1.14.     

Effect of saline water on cucumber (Cucumis sativus L.) yield and water use under drip irrigation in North China

Saline water has been included as an important substitutable resource for fresh water in agricultural irrigation in many fresh water scarce regions. In order to make good use of saline water for agricultural irrigation in North China, a semi-humid area, a 3-year field experiment was carried out to study the possibility of using saline water for supplement irrigation of cucumber. Saline water was applied via mulched drip irrigation. The average electrical conductivity of irrigation water (EC_iw) was 1.1, 2.2, 2.9, 3.5 and 4.2 dS/m in 2003 and 2004, and 1.1, 2.2, 3.5, 4.2 and 4.9 dS/m in 2005. Throughout cucumber-growing season, the soil matric potential at 0.2 m depth immediately under drip emitter was kept higher than −20 kPa and saline water was applied after cucumber seedling stage. The experimental results revealed that cucumber fruit number per plant and yield decreased by 5.7% per unit increase in EC_iw. The maximum yield loss was around 25% for EC_iw of 4.9 dS/m, compared with 1.1 dS/m. Cucumber seasonal accumulative water use decreased linearly over the range of 1.5-6.9% per unit increase in EC_iw. As to the average root zone EC_e (electrical conductivity of saturated paste extract), cucumber yield and water use decreased by 10.8 and 10.3% for each unit of EC_e increase in the root zone (within 40 cm away from emitter and 40 cm depths), respectively. After 3 years irrigation with saline water, there was no obvious tendency for EC_e to increase in the soil profile of 0-90 cm depths. So in North China, or similar semi-humid area, when there is no enough fresh water for irrigation, saline water up to 4.9 dS/m can be used to irrigate field culture cucumbers at the expense of some yield loss.     

Evaluation of the influence of irrigation methods and water quality on sugar beet yield and water use efficiency

Rapid urbanization and industrialization have increased the pressure on limited existing fresh water to meet the growing needs for food production. Two immediate responses to this challenge are the efficient use of irrigation technology and the use of alternative sources of water. Drip irrigation methods may play an important role in efficient use of water but there is still limited information on their use on sugar beet crops in arid countries such as Iran. An experiment was conducted to evaluate the effects of irrigation method and water quality on sugar beet yield, percentage of sugar content and irrigation water use efficiency (IWUE). The irrigation methods investigated were subsurface drip, surface drip and furrow irrigation. The two waters used were treated municipal effluent (EC = 1.52 dS m⁻¹) and fresh water (EC = 0.509 dS m⁻¹). The experiments used a split plot design and were undertaken over two consecutive growing seasons in Southern Iran. Statistical testing indicated that the irrigation method and water quality had a significant effect (at the 1% level) on sugar beet root yield, sugar yield, and IWUE. The highest root yield (79.7 Mg ha⁻¹) was obtained using surface drip irrigation and effluent and the lowest root yield (41.4 Mg ha⁻¹) was obtained using furrow irrigation and fresh water. The highest IWUE in root yield production (9 kg m⁻³) was obtained using surface drip irrigation with effluent and the lowest value (3.8 kg m⁻³) was obtained using furrow irrigation with fresh water. The highest IWUE of 1.26 kg m⁻³ for sugar was obtained using surface drip irrigation. The corresponding efficiency using effluent was 1.14 kg m⁻³. Irrigation with effluent led to an increase in the net sugar yield due to an increase in the sugar beet root yield. However, there was a slight reduction in the percentage sugar content in the plants. This study also showed that soil water and root depth monitoring can be used in irrigation scheduling to avoid water stress. Such monitoring techniques can also save considerable volumes of irrigation water and can increase yield.