Managing subsurface drip irrigation in the presence of shallow ground water

A 3-year project compared the operation of a subsurface drip irrigation (SDI) and a furrow irrigation system in the presence of shallow saline ground water. We evaluated five types of drip irrigation tubing installed at a depth of 0.4 m with lateral spacings of 1.6 and 2 m on 2.4 ha plots of both cotton and tomato. Approximately 40% of the cotton water requirement and 10% of the tomato water requirement were obtained from shallow (<2 m) saline (5 dS/m) ground water. Yields of the drip-irrigated cotton improved during the 3-year study, while that of the furrow-irrigated cotton remained constant. Tomato yields were greater under drip than under furrow in both the years in which tomatoes were grown. Salt accumulation in the soil profile was managed through rainfall and pre-plant irrigation. Both drip tape and hard hose drip tubing are suitable for use in our subsurface drip system. Maximum shallow ground water use for cotton was obtained when the crop was irrigated only after a leaf water potential (LWP) of −1.4 MPa was reached. Drip irrigation was controlled automatically with a maximum application frequency of twice daily. Furrow irrigation was controlled by the calendar.     

The effects of different irrigation regimes on cucumber (Cucumbis sativus L.) yield and yield characteristics under open field conditions

A study was conducted to determine the effects of different drip irrigation regimes on yield and yield components of cucumber (Cucumbis sativus L.) and to determine a threshold value for crop water stress index (CWSI) based on irrigation programming. Four different irrigation treatments as 50 (T-50), 75 (T-75), 100 (T-100) and 125% (T-125) of irrigation water applied/cumulative pan evaporation (IW/CPE) ratio with 3-day-period were studied.Seasonal crop evapotranspiration (ET_c) values were 633, 740, 815 and 903 mm in the 1st year and were 679, 777, 875 and 990 mm in the 2nd year for T-50, T-75, T-100 and T-125, respectively. Seasonal irrigation water amounts were 542, 677, 813 and 949 mm in 2002 and 576, 725, 875 and 1025 mm in 2003, respectively. Maximum marketable fruit yield was from T-100 treatment with 76.65 t ha⁻¹ in 2002 and 68.13 t ha⁻¹ in 2003. Fruit yield was reduced significantly, as irrigation rate was decreased. The water use efficiency (WUE) ranged from 7.37 to 9.40 kg m⁻³ and 6.32 to 7.79 kg m⁻³ in 2002 and 2003, respectively, while irrigation water use efficiencies (IWUE) were between 7.02 and 9.93 kg m⁻³ in 2002 and between 6.11 and 8.82 kg m⁻³ in 2003.When the irrigation rate was decreased, crop transpiration rate decreased as well resulting in increased crop canopy temperatures and CWSI values and resulted in reduced yield. The results indicated that a seasonal mean CWSI value of 0.20 would result in decreased yield. Therefore, a CWSI = 0.20 could be taken as a threshold value to start irrigation for cucumber grown in open field under semi-arid conditions.Results of this study demonstrate that 1.00 IW/CPE water applications by a drip system in a 3-day irrigation frequency would be optimal for growth in semiarid regions.     

Effects of different irrigation methods on shedding and yield of cotton

In general, cotton is irrigated by surface methods in Turkey although sprinkler and drip irrigation have been suggested as a means of supplying most types of crops with frequent and uniform applications of water, adaptable over a wide range of topographic and soil conditions. Recently, sprinkler irrigation systems have been introduced for cotton as a result of increased pressure to develop new irrigation technology suited to limited water supply as well as to specific topographic and soil conditions. In this study, the effects of three different irrigation methods (furrow, sprinkler and drip) on seed-cotton yield, shedding ratio and certain yield components are presented. The research was carried out in The Southeastern Anatolia Region (GAP) of Turkey from 1991 to 1994. The maximum cotton yields were 4380, 3630 and 3380 kg/ha for drip, furrow and sprinkler irrigation, respectively. Drip irrigation produced 21% more seed-cotton than the furrow method and 30% more than the sprinkler method. Water use efficiencies (WUE) proved to be 4.87, 3.87 and 2.36 kg/ha/mm for drip, furrow and sprinkler, respectively. Shedding ratios ranged from 50.8 to 59.0% (furrow), 52.9 to 64.8% (sprinkler), 50.8 to 56.8% (drip), depending on the amount of water applied. The shedding ratio for sprinkler irrigation was significantly higher than that of either furrow (P=0.10) or drip irrigation (P=0.05), resulting in lower seed-cotton yield for sprinkler irrigation. For all methods, a quadratic relationship was found between the amount of water applied and shedding ratios, with the least shedding occurring between 1000 and 1500 mm of water. Both limited and over-irrigation increased the shedding ratio for all methods. Accordingly, a lower boll number per plant and a lower seed-cotton yield were obtained from sprinkler-irrigated cotton; a significantly decreasing linear relationship between the shedding ratio and the total cotton yield and boll number per plant.     

Trickle and sprinkler irrigation of potato (Solanum tuberosum L.) in the Middle Anatolian Region in Turkey

The potato (Solanum tuberosum L.) is widely planted in the Middle Anatolian Region, especially in the Nigde-Nevsehir district where 25% of the total potato growing area is located and produces 44% of the total yield. In recent years, the farmers in the Nigde-Nevsehir district have been applying high amounts of nitrogen (N) fertilizers (sometimes more than 900 kg N ha⁻¹) and frequent irrigation at high rates in order to get a much higher yield. This situation results in increased irrigation and fertilization costs as well as polluted ground water resources and soil. Thus, it is critical to know the water and nitrogen requirements of the crop, as well as how to improve irrigation efficiency. Field experiments were conducted in the Nigde-Nevsehir (arid) region on a Fluvents (Entisols) soil to determine water and nitrogen requirements of potato crops under sprinkler and trickle irrigation methods. Irrigation treatments were based on Class A pan evaporation and nitrogen levels were formed with different nitrogen concentrations.The highest yield, averaging 47,505 kg ha⁻¹, was measured in sprinkler-irrigated plots at the 60 g m⁻³ nitrogen concentration level in the irrigation treatment with limited irrigation (480 mm). Statistically higher tuber yields were obtained at the 45 and 60 g m⁻³ nitrogen concentration levels in irrigation treatments with full and limited irrigation. Maximum yields were obtained with about 17% less water in the sprinkler method as compared to the trickle method (not statistically significant). On the loam and sandy loam soils, tuber yields were reduced by deficit irrigation corresponding to 70% and 74% of evapotranspiration in sprinkler and trickle irrigations, respectively. Water use of the potato crop ranged from 490 to 760 mm for sprinkler-irrigated plots and 565–830 mm for trickle-irrigated treatments. The highest water use efficiency (WUE) levels of 7.37 and 4.79 kg m⁻³ were obtained in sprinkle and trickle irrigated plots, respectively. There were inverse effects of irrigation and nitrogen levels on the WUE of the potato crops. Significant linear relationships were found between tuber yield and water use for both irrigation methods. Yield response factors were calculated at 1.05 for sprinkler methods and 0.68 for trickle methods. There were statistically significant linear and polynomial relationships between tuber yield and nitrogen amounts used in trickle and sprinkler-irrigated treatments, respectively. In sprinkler-irrigated treatments, the maximum tuber yield was obtained with 199 kg N ha⁻¹. The tuber cumulative nitrogen use efficiency (NUE_cu) and incremental nitrogen use efficiency (NUE_in) were affected quite differently by water, nitrogen levels and years. NUE_cu varied from 16 to 472 g kg⁻¹ and NUE_in varied from 75 to 1035 g kg⁻¹ depending on the irrigation method. In both years, the NH₄-N concentrations were lower than NO₃-N, and thus the removed nitrogen and nitrogen losses were found to be 19–87 kg ha⁻¹ for sprinkler methods and 25–89 kg ha⁻¹ for trickle methods. Nitrogen losses in sprinkler methods reached 76%, which were higher than losses in trickle methods.     

Soil–plant water status and yield of sweet corn (Zea mays L. cv. Saccharata) as influenced by drip irrigation and planting methods

A field experiment was conducted during summer season of 1998 at the Main Research Station, University of Agricultural Sciences, Hebbal, Bangalore. Experiment consisted of four irrigation levels and two methods of planting. Drip irrigation at 0.8 Epan with normal planting recorded significantly higher green cob (20.07 t ha⁻¹) and fodder yield (24.87 t ha⁻¹) compared to either drip at 0.6 Epan or weekly surface irrigation at 0.8 Epan, while drip at 0.4 Epan under paired planting (10.53 and 15.23 t ha⁻¹, respectively registered the lowest. Drip at 0.4 Epan with normal planting recorded higher WUE of green cob and fodder (48.21 and 61.22 kg ha mm⁻¹) with total water requirement of 330.46 mm. With increase in water use (drip at 0.6 Epan, drip/surface irrigation at 0.8 Epan) the water use efficiency decreased. Drip irrigation at 0.8 Epan resulted in higher leaf water potential (−4, −7, −8 bars) at 20, 40 and 60 DAS before irrigation. Consequently, the RWC in the leaf was 81.10% and the available soil moisture ranged from 55.62 to 61.91%.     

Response of green bean (P. vulgaris L.) to subsurface drip irrigation and partial rootzone-drying irrigation

Effects on water use, green bean yield, irrigation water-use efficiency (IWUE), water-use efficiency (WUE), plant dry weight and crop water relationship were investigated for two-drip irrigation techniques and four irrigation water levels in the Mediterranean region of Turkey. The treatments were conventional (SDI) and alternating subsurface drip irrigation (SPRD). At each irrigation event, half of the volume of water applied to the SDI was applied to one side of the crop, representing the partial rootzone-drying treatment. All treatments received 295 mm of irrigation during crop establishment, prior to beginning the different irrigation regimes. Differing irrigation amounts corresponded to four crop-pan coefficients (Kcp₁ = 0.6, Kcp₂ = 0.8, Kcp₃ = 1.0 and Kcp₄ = 1.2), appropriate to pan data. Total water applied to the SDI and SPRD treatments ranged from 366 to 437 mm and from 331 to 366 mm, respectively, depending on Kcp values, with water uptake varying from 396 to 470 mm and 364 to 409 mm, respectively. While differences of green bean yield and dry plant weights were not significantly affected by the SDI and SPRD irrigation techniques, the overall irrigation water saving was found to be 16% for the SPRD irrigation treatment compared with the SDI treatment. SPRD irrigation techniques increased IWUE, WUE, and slopes of yield water relationships. Increase in slopes of the yield–irrigation water and yield–water-use function of SPRD according to the equivalent slopes of the SDI were 215.8 and 151.4%, respectively. SPRD increased the green bean yield response factor (ky) with value of 128.4% according to the equivalent slopes of the SDI. In conclusion, irrigation scheduling based on a 0.8 crop-pan coefficient is recommended for conventional SDI, with 1.0 being more appropriate for partial rootzone-drying practice.     

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.     

Effect of drip irrigation on squash (Cucurbita pepo) yield and water-use efficiency in sandy calcareous soils amended with clay deposits

Water research studies in Saudi Arabia clearly showed sever depletion of groundwater. Therefore, the scientifically applied research program related to water saving and conservation in agriculture is essential, where agricultural activities account for more than 85% of the total water consumed. This study aims to investigate the effect of four irrigation levels, two irrigation methods and three clay deposits on water-use efficiency (WUE) of squash and the distributions of salts and roots in sandy calcareous soils. A field experiment was conducted at the college experimental station in 2002 and 2003. It consists of three clay deposits, three rates (CO = 0, C2 = 1.0 and C3 = 2.0%), four irrigation levels (T₁ = 60, T₂ = 80, T₃ = 100 and T₄ = 120% of Eto) using surface (IM1) and subsurface (IM2) drip irrigation.Results indicated that squash fruit yield was significantly increased with the increase in irrigation water level for each season. Generally, WUE values were increased as linearly with applied irrigation water and decreased at the highest irrigation level. Types of clay deposits significantly affected fruit yields compared with the control. The yield increase was 12.8, 8.35 and 6.4% for Khulays, Dhruma and Rawdat clay deposits, respectively. The differences between surface and subsurface drip on fruit yields and WUE were also significant. Results indicated that moisture content of subsurface-treated layer increased dramatically, while salts were accumulated at the surface and away from the emitters in subsurface drip irrigation. Intensive root proliferation is observed in the clay-amended subsurface layer compared with non-amended soil. The advantages of subsurface drip irrigation were related to the relative decrease in salt accumulation in the root zone area where the plant roots were active and water content was relatively higher.     

Economics of drip irrigation of olives in Turkey

Agricultural growers need investment and cost guidelines for drip irrigation to evaluate the economics of getting crops into production as quickly as possible and to minimise economic losses from drought during the productive life of an olive orchard. The benefits of irrigation may include; better olive survival, earlier crop production, greater yields, efficient nutrient distribution, less plant stress, reduced yield variability and improved crop quality.This research was conducted to help olive growers make decisions regarding investments in drip irrigation systems. This analysis was aimed at the farm business level to provide an economic rationale for investing in drip irrigation systems.The net present value (NPV) criterion was used to determine the discounted break-even investment results from published responses to drip irrigation systems. Growers with typical drip irrigation systems can expect investments of US$ 2244 ha⁻¹ with 1.6 ha blocks of olives. Analysis of survey findings indicate that net present value was US$ 3464 ha⁻¹ after an initial investment of US$ 2244 ha⁻¹.     

Yield response of greenhouse grown tomato to partial root drying and conventional deficit irrigation

Greenhouse grown tomato was used to test partial root drying (PRD), a newly developing irrigation technique to save irrigation water, in Spring- and Fall-planted fresh-market tomato (Lycopersicon esculentum L., cv. Fantastic) cultivar. The PRD practice simply requires wetting of one half of the rooting zone and leaving the other half dry, thereby utilizing reduced amount of irrigation water applied. The wetted and dry sides are interchanged in the subsequent irrigations. Six irrigation treatments were tested during the two-year work in 2000 and 2001: (1) FULL, control treatment where the full amount of irrigation water, which was measured using Class-A pan evaporation data, was applied to the roots on all sides of the plant; (2) 1PRD30, 30% deficit irrigation with PRD in which wetted and dry sides of the root zone were interchanged with every irrigation; (3) 1PRD50; (4) 2PRD50, 50% deficit irrigation with PRD in which wetted and dry sides of the root zone were interchanged every and every other irrigation, respectively; (5) DI30 and (6) DI50, 30 and 50% deficit irrigations, respectively. The defined deficit levels were all in comparison to FULL irrigation. During the first year study in 2000, only three treatments (FULL, 1PRD30 and 2PRD50) were tested. Five treatments with exception of 2PRD50 were included in 2001. The FULL irrigation treatment, in Spring-planted tomato having a 153 day growth period, yielded 110.9 t ha⁻¹. The resulting irrigation-water-use efficiency (IWUE) was 321.8 kg (ha mm)⁻¹. The 1PRD50 treatment gave 86.6 t ha⁻¹, which was not statistically different (P ≤ 0.05) from the FULL irrigation (the control) and had 56% higher IWUE. Although yield differences were not statistically significant in Fall-planted tomato, the highest fruit yield was again obtained under FULL irrigation treatment (205.2 t ha⁻¹) over a growth period of 259 days after transplanting. The PRD treatments had 7–10% additional yield over the deficit irrigation receiving the same amount of water. The PRD treatments gave 10–27% higher marketable tomato yield (>60 g per fruit), compared with the DI treatments. Abscisic acid (ABA) concentrations measured in fresh leaf tissue was the highest under PRD practice relative to FULL and DI treatments. The high ABA content of fresh-leaf tissue observed in the work supports the root signalling mechanism reported earlier in plants having undergone partial root drying cycles.     

Effects of irrigation method on chile pepper yield and Phytophthora root rot incidence

A field experiment was conducted in 1995 and 1996 to examine the effects of different irrigation methods on yields and Phytophthora root rot disease of chile plants (Capsicum annum New Mexico `6–4'). Three irrigation methods, daily drip, 3-day drip, and alternate row furrow irrigation, were applied to plots infested with P. capsici and uninfested plots. For both years, the drip irrigation (either daily or 3-day) created higher marketable green chile yields than the alternate row furrow irrigation (p < 0.05), and the yields between the daily and 3-day drip irrigation were statistically similar. The effect of irrigation on marketable combined yields was similar to that on green chile yields. In 1995, root rot disease incidence in the infested plots was significantly higher under alternate row furrow irrigation than for daily and 3-day drip irrigation. There was no disease development in the uninfested plots regardless of the irrigation method. The disease decreased green chile yield by 55% (p < 0.1), and combined yield (green + red chile) by 36% (p < 0.1) in 1995 compared to that in uninfested plots in alternate row furrow irrigation. In 1996, however, no disease occurred in any treatment. The results suggested that drip irrigation increases chile yield through providing either favorable soil moisture conditions or unfavorable conditions for Phytophthora propagation.     

Water and nitrate movement in drip-irrigated onion under fertigation and irrigation treatments

Frequent fertigation of crops is often advocated in the technical and popular literature, but there is limited evidence of the benefits of high-frequency fertigation. Field experiments were conducted on an Indo-American Hybrid var., Creole Red, of onion crop during three winter seasons of 1999–2000 through 2001–2002 in coarse-textured soil of Delhi under the semi-arid region of India. Three irrigation levels of 60, 80 and 100% of the crop evapotranspiration (ET) and four fertigation frequencies of daily, alternate day, weekly and monthly comprised the fertigation treatment. Analysis of soil samples indicated considerable influence of fertigation frequency on NO₃-N distribution in soil profile. NO₃-N in lower soil profiles (30.0–60.0 cm soil depth) was marginally affected in daily, alternate day and weekly fertigation. However, fluctuations of NO₃-N content in 0.0–15.0, 15.0–30.0, 30.0–45.0 and 45.0–60.0 cm soil depth was more in monthly fertigation frequency. The level of soil NO₃-N after the crop season shows that more NO₃-N leached through the soil profile in monthly fertigation frequency. Amounts of irrigation water applied in three irrigation treatments proved to be too small to cause significant differences in the content of NO₃-N leached beyond rooting depth of onion. Yield of onion was not significantly affected in daily, alternate day and weekly fertigation, though there was a trend of lower yields with monthly fertigation. The highest yield was recorded in daily fertigation (28.74 t ha⁻¹) followed by alternate day fertigation (28.4 t ha⁻¹). Lowest yield was recorded in monthly fertigation frequency (21.4 t ha⁻¹). Application of 56.4 cm irrigation water and 3.4 kg ha⁻¹ urea per fertigation (daily) resulted in highest yield of onion with less leaching of NO₃-N.     

Effects of timing and duration of brackish irrigation water on fruit yield and quality of late summer melons

Brackish water (7 dS m⁻¹) is frequently utilized to drip-irrigate crops in the Negev desert of Israel, the practice being to use deep sandy soils (96% sand) to avoid soil salinization. When muskmelon (Cucumis melo L.), a moderately salt-sensitive crop species, was grown using brackish irrigation under these conditions, yields declined due to a significant reduction in fruit size, but fruit quality parameters improved markedly. In the present study, we tested the hypothesis that the use of fresh irrigation water during the early vegetative phase would increase canopy size and leaf area index (LAI) and hence the potential productivity of the melon plant. The application of brackish water during the reproductive phase, on the other hand, would improve fruit quality. Using multiple irrigations within a 24-h period, applied with drip irrigation, we examined the timing, the duration, and the concentration of brackish irrigation water as tools to optimize fruit yield and quality in late-summer melons. Indeed, the combination of fresh (1.2 dS m⁻¹) and brackish (7 dS m⁻¹) irrigation water increased the yield level to that of fresh water plants whereas it brought about the improvement of fruit quality typical to brackish water plants, thus providing an attractive approach to optimize late-summer melon production. Our results demonstrate the trade-off between fruit size and fruit quality as related to the timing and the duration of brackish irrigation water. The use of a milder (<4.5 dS m⁻¹) salinity level of irrigation water from plant emergence until harvest may be considered as well.     

Irrigation management in arid areas affected by surface crust

The effects of supplemental irrigation and irrigation practices on soil water storage and barley crop yield were studied for a crust-forming soil at the University of Jordan Research Station near Al-Muwaqqar village during the 1996/97 growing season. An amount of 0.0, 48.9, 73.3, 122.2 and 167 mm supplemental irrigation water were applied. The 48.9, 73.3 and 122.2 mm applications were applied through surface irrigation into furrows with blocked ends, and the 0.0 and 167 mm applications via sprinkler irrigation. The greatest water infiltration and subsequent soil storage was achieved with the 122.2 mm application followed by the 73.3 mm irrigation, both surface applied. Application efficiency (the fraction of applied water that infiltrated into the soil and stored in the 600 mm soil profile) and soil water storage associated with supplemental blocked furrow irrigation was significantly greater than with supplemental sprinkler irrigation. For arid zone soil, which has little or no structural stability, application of supplemental irrigation water via short, blocked-end furrows prevents runoff and increases the opportunity time for infiltration, thereby increasing the amount of applied water that is infiltrated into the soil and stored in the soil profile. Supplemental irrigation, applied by a low-rate sprinkler system, was not as effective because of the low infiltration rates that resulted from the development of a surface throttle due to dispersion of soil aggregates at the soil surface. The differences in stored water had a significant effect on grain and straw yields of barley. Without supplemental irrigation, barley grain and straw yields were zero in natural rainfall cultivation with a total rainfall of 136.5 mm. Barley yields in the control treatment, with a 167 mm supplemental sprinkler irrigation were low being 0.19 and 1.09 ton/ha of barley grain and straw, respectively. Supplemental irrigation through blocked-end furrows increased barley grain and straw yields significantly compared with supplemental sprinkler irrigation to a maximum of 0.59 and 1.8 ton/ha, respectively. The improvement coming from the increased water storage associated with furrows. Since irrigation water is very limited if available, farmers are encouraged to form such furrows for reducing runoff from rainfall thereby increasing the amount of water available for forage and field crop production.     

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.     

Water requirement of drip irrigated tomatoes grown in greenhouse in tropical environment

Four different levels of drip fertigated irrigation equivalent to 100, 75, 50 and 25% of crop evapotranspiration (ET_c), based on Penman–Monteith (PM) method, were tested for their effect on crop growth, crop yield, and water productivity. Tomato (Lycopersicon esculentum, Troy 489 variety) plants were grown in a poly-net greenhouse. Results were compared with the open cultivation system as a control. Two modes of irrigation application namely continuous and intermittent were used. The distribution uniformity, emitter flow rate and pressure head were used to evaluate the performance of drip irrigation system with emitters of 2, 4, 6, and 8 l/h discharge. The results revealed that the optimum water requirement for the Troy 489 variety of tomato is around 75% of the ET_c. Based on this, the actual irrigation water for tomato crop in tropical greenhouse could be recommended between 4.1 and 5.6 mm day⁻¹ or equivalent to 0.3–0.4 l plant⁻¹ day⁻¹. Statistically, the effect of depth of water application on the crop growth, yield and irrigation water productivity was significant, while the irrigation mode did not show any effect on the crop performance. Drip irrigation at 75% of ET_c provided the maximum crop yields and irrigation water productivity. Based on the observed climatic data inside the greenhouse, the calculated ET_c matched the 75–80% of the ET_c computed with the climatic parameters observed in the open environment. The distribution uniformity dropped from 93.4 to 90.6%. The emitter flow rate was also dropped by about 5–10% over the experimental period. This is due to clogging caused by minerals of fertilizer and algae in the emitters. It was recommended that the cleaning of irrigation equipments (pipe and emitter) should be done at least once during the entire cultivation period.     

Yield and physiological traits of prickly pear cactus ‘nopal’ (Opuntia spp.) cultivars under drip irrigation

A drip irrigation system was installed above ground at 30, 45, and 60% of the weekly-accumulated evaporation depth to evaluate productivity of harvested green cladodes (leaf-like stem segments) of the prickly pear cactus. Results showed that irrigating above 30% does not increase crop production. This percentage represents an annual irrigation depth of 0.74 m, which is one of the lowest in the regional irrigation district of “La Laguna” in the state of Coahuila. Nopal Opuntia ficus indica cv. C-69 showed the highest green cladode “nopalitos” yield, with 108 tonnes (ha⁻¹ year⁻¹) and sustained growth except during the cold season. Leaf area index was 80, net assimilation rate was 0.178 g (dm⁻² day⁻¹), and dry-weight at maximum productivity was 9.2 g for the confidence parameters for the week representing average green cladodes growth     

Different irrigation methods and water stress effects on potato yield and yield components

This research was conducted during the spring seasons of 2000 and 2002 in Hatay province located in the East Mediterranean Region of Turkey. The research investigated the effects of two drip irrigation methods and four different water stress levels on potato yield and yield components. The surface drip (SD) and subsurface drip (SSD) irrigation methods were used. The levels were full irrigation (I₁₀₀), 66% of full irrigation (I₆₆), 33% of full irrigation (I₃₃) and un-irrigated (I₀) treatments. Five and three irrigation were applied in 2000 and 2002 early potato growing seasons, respectively. Total irrigation amount changed from 102 to 302 mm and from 88 to 268 mm in 2000 and 2002, respectively. Seasonal evapotranspiration changed between 226 and 473 mm and 166 and 391 mm in 2000 and 2002, respectively. SD and SSD irrigation methods did not result in a significant difference on yield. However, SD method has more advantages than SSD method, which has difficulties in replacement and higher system cost. Irrigation levels resulted in significant difference in both years on yield and its components. Water stress significantly affected the yield and yield parameters of early potato production. Water deficiency more than 33% of the irrigation requirement could not be suggested.Water use efficiency (WUE) of SD irrigation methods had generally higher values than SSD irrigation methods. Treatment I₃₃ gave maximum irrigation water use efficiency (IWUE) for both years. SSD irrigation method did not provide significant advantage on yield and WUE, compared to SD irrigation in early potato production under experimental conditions. Therefore, the SD irrigation method would be recommended in early potato production under Mediterranean conditions.     

Role of straw mulching in non-continuously flooded rice cultivation

Rice (Oryza sativa L.) cultivation under non-flooded (NF) condition is a new alternative to the conventional flooded (CF) rice cultivation system in the regions where rainfall and fresh water resources are limited. Non-flooded rice cultivation may mediate rice growth performance and mulching may be good practice to reduce evapotranspiration and increase water use efficiency (WUE). The research objectives of this study were to investigate the effects of non-flooded cultivation with straw mulching on the rice agronomic traits and water use efficiency of the second rice cropping season (late rice). The treatments were conventional flooded rice cultivation, non-flooded rice cultivations without (NF-ZM) and with rice straw mulching (NF-SM). Irrigation water was 19950 m³ ha⁻¹ in 2003 and 15,850 m³ ha⁻¹ in 2004 in the CF treatments and 7200 m³ ha⁻¹ in 2003 and 5045 m³ ha⁻¹ in 2004 in the non-flooded rice fields (NF-ZM and NF-SM treatments).The field measurements showed that water seepage was 13,442 m³ ha⁻¹ in the CF treatment, 5510 m³ ha⁻¹ in the NF-ZM treatment and 5424 m³ ha⁻¹ in the NF-SM treatment. Rice straw mulching decreased evapotranspiration by 33% and 63% (in 2003), 36.5% and 57.1% (in 2004) to the NF-ZM treatment and CF treatment, respectively. Compared with the NF-ZM treatment, mulch application significantly increased the leaf area per plant, main root length, tap root length and root dry weight per plant of crop. The yield of the NF-SM treatment (2003: 6489 kg/hm²; 2004: 8574.8 kg/hm²) was similar with the value of the CF treatment (2003: 6811.5; 2004: 8630.5 kg/hm²), and much higher than the NF-ZM treatment (2003: 4716; 2004: 6394.8 kg/hm²). The order of irrigation water use efficiency (IWUE) and water use efficiency were as follows: NF-SM > NF-ZM > CF.     

Water use and lint yield response of drip irrigated cotton to the length of irrigation season

A 2-year experiment was conducted at Tal Amara Research Station in the Bekaa Valley of Lebanon to determine water use and lint yield response to the length of irrigation season of drip irrigated cotton (Gossypium hirsutum L.). Crop evapotranspiration (ET_crop) and reference evapotranspiration (ET_rye-grass) were directly measured at weekly basis during the 2001 growing period using crop and rye-grass drainage lysimeters. Crop coefficients (K_c) in the different growth stages were calculated as ET_crop/ET_rye-grass. Then, the calculated K_c values were used in the 2002 growing period to estimate evapotranspiration of cotton using the FAO method by multiplying the calculated K_c values by ET_rye-grass measured in 2002. The length of irrigation season was determined by terminating irrigation permanently at first open boll (S1), at early boll loading (S2), and at mid boll loading (S3). The three treatments were compared to a well-watered control (C) throughout the growing period. Lint yield was defined as a function of components including plant height at harvest, number of bolls per plant, and percentage of opened bolls per plant.Lysimeter-measured crop evapotranspiration (ET_crop) totaled 642 mm in 2001 for a total growing period of 134 days, while when estimated with the FAO method in 2002 it averaged 669 mm for a total growing period of 141 days from sowing to mature bolls. Average K_c values varied from 0.58 at initial growth stages (sowing to squaring), to 1.10 at mid growth stages (first bloom to first open boll), and 0.83 at late growth stages (early boll loading to mature bolls).Results showed that cotton lint yields were reduced as irrigation amounts increased. Average across years, the S1 treatment produced the highest yield of 639 kg ha⁻¹ from total irrigations of 549 mm, compared to the S2 and S3 treatments, which yielded 577 and 547 kg ha⁻¹ from total irrigations of 633 and 692 mm, respectively, while the control resulted in 457 kg ha⁻¹ of lint yield from 738 mm of irrigation water. Water use efficiency (WUE) was found to be higher in S1 treatment and averaged 1.3 kg ha⁻¹ mm⁻¹, followed by S2 (1.1 kg ha⁻¹ mm⁻¹), and S3 (1.0 kg ha⁻¹ mm⁻¹), while in the control WUE was 0.80 kg ha⁻¹ mm⁻¹. Lint yield was negatively correlated with plant height and the number of bolls per plant and positively correlated with the percentage of opened bolls. This study suggests that terminating irrigation at first open boll stage has been found to provide the highest cotton yield with maximum WUE under the semi-arid conditions of the Bekaa Valley of Lebanon.