Subsurface Drip Irrigation Treatments Research Articles

Improving Water Productivity Using Subsurface Drip Irrigation in the Southwest Monsoon Area in Yunnan Province of China

Due to the influence of the Asian southwest monsoon, seasonal drought is serious and water resources are scarce in the Yunnan province of Southwest China. More effective water-saving irrigation methods should be developed to solve the problem of water scarcity in the dry season. In this study, a subsurface drip irrigation method was used to improve the water productivity of tomato cultivation. Deficit irrigation was conducted. We controlled the lower limit of soil moisture at three different levels (55~65%, 65~75%, and 75~85% of the field capacity). The results indicated that the subsurface drip irrigation treatment significantly increased tomato height in the later stage of tomato growth. Due to the buried pipes, the root/shoot ratio was 8~18% higher for subsurface drip irrigation than for surface drip irrigation methods. Though the yields using subsurface drip irrigation methods were slightly lower than those obtained using surface drip irrigation methods, the tomato quality and water productivity improved significantly. The subsurface drip irrigation methods improved the water productivity by 8.5~21.8% at different soil moisture levels and improved the chlorophyll content by 9.1~17.3%. The VC, soluble sugar, soluble solids, and the ratio of sugar to acid increased by 6.5~15.2%, 7.3~21.6%, 4.1~6.6%, and 3.2~20.8%. This study also indicated that by optimizing the irrigation methods and patterns, water productivity and fruit quality could be improved by more than 50%. This research will be helpful for guiding irrigation during the drought season in the southwest monsoon area in Asia.

Potential Use of Subsurface Drip Irrigation Systems in Landscape Irrigation under Full and Limited Irrigation Conditions

Water is an essential component of life in the world. In addition to being crucial to keeping plants alive, water is also used in various areas, such as landscape irrigation, decorative pools, and ponds. The use of water more efficiently is getting more and more important day by day because of the increasing demands of different sectors. In cities with limited water resources, such as Konya, water should be used even more efficiently to reduce irrigation water quantities and prevent water losses. The potential use of the sub-surface drip irrigation method in the irrigation of green areas in Selçuklu district of Konya province was investigated, and the sub-surface drip irrigation method was compared with the fixed sprinkler irrigation method (pop-up) in terms of irrigation parameters (amount of irrigation water applied, plant water consumption) and plant characteristics (germination, plant height, number of mows, mowing weight, root depth). In the present experiments, 18 different sub-surface drip irrigation treatments (100, 80, and 60% irrigations + 40, 60, and 80 cm lateral spacings + 10 and 15 cm lateral depths) and three different sprinkler irrigation treatments (100, 80, and 60% irrigations) were used. Present findings revealed that sub-surface drip irrigation systems were suitable for irrigation of green areas, and this system was more advantageous for municipalities in terms of water savings, irrigation labor, and maintenance. For sub-surface drip irrigation systems, S1 (supply 100% of evaporation from Class-A pan + 40 cm lateral spacing + 10 cm lateral depth) treatments were found to be the best system arrangement for landscape irrigations in Selçuklu district in Konya province.

Water Use, Growth, and Yield of Ratooned Guayule under Subsurface Drip and Furrow Irrigation in the US Southwest Desert

Guayule (Parthenium argentatum, A. Gray) is a perennial desert shrub with ratoon-cropping potential for multiple harvests of its natural rubber, resin, and bagasse byproducts. However, yield expectations, water use requirements, and irrigation scheduling information for ratooned guayule are extremely limited. The objectives of this study were to evaluate dry biomass (DB), contents of rubber (R) and resin (Re) and yields of rubber (RY) and resin (ReY) responses to irrigation treatments, and develop irrigation management criteria for ratooned guayule. The water productivity (WP) of the yield components were also evaluated. Guayule plants that were direct-seeded in April 2018 were ratooned and regrown starting in April 2020, after an initial 2-year harvest at two locations in Arizona: Maricopa and Eloy on sandy loam and clay soils, respectively. Plots were irrigated with subsurface drip irrigation (SDI) at 50, 75, and 100% replacement of crop evapotranspiration (ETc), respectively, and furrow irrigation at 100% ETc replacement, as determined by soil water balance measurements. The Eloy location did not include the 100% irrigation treatment under SDI due to unsuccessful regrowth for this specific treatment. The irrigation treatments at the locations were replicated three times in a randomized complete block design. After 21–22 months of regrowth, the guayule plants were harvested in plots. The results showed that DB increased with the amount of total water applied (TWA, irrigation plus precipitation), while R and Re were reduced at the highest TWA received at both locations. Ultimately, the SDI treatments with 75% ETc replacement resulted in the best irrigation management in terms of maximizing RY and ReY, and WP for both locations and soil types. Compared to the initial 2-year direct-seeded guayule crop, ratooned guayule required less TWA and attained higher DB, RY, and ReY, as well as higher WP, with average increases of 25% in dry biomass, 33% in rubber yield, and 32% in resin yield. A grower’s costs for planting the initial direct-seeded guayule crop would be offset by the additional yield revenue of the ratooned crop, which would have comparatively small startup costs.

The Effect of some Irrigation Methods and Moisture Depletion percent in the Growth and Productivity of Corn

The experiment was conducted in the fields of Al-Hilla - Babylon province, with loam soil, during the autumn season of 2021, to study the effect of different irrigation methods and levels of depletions on the growth and yield of corn (Zea mays L.). The Randomized Complete Block Design (RCBD) was an as complete split plot with three replications, the main plot included the treatment of depletion levels and subplot irrigation systems, and the treatments were distributed on the experimental plots randomly. Irrigation systems included three levels of subsurface drip irrigation - surface drip irrigation - surface irrigation with furrows, and the levels of depletion for each treatment were 20%, 40%, and 60%. The result showed that the subsurface drip irrigation treatment with 40% depletion achieved the highest plant height (206.92). While there was no significant difference with the surface drip treatment. The furrows irrigation system has the lowest plant height, which reached (174.14). There are significant differences between the treatment and the level of depletion in the area of the leaves of the plant. Also, the irrigation methods used did not significantly affect the weight and depth of the roots, while there were significant differences in the values ​​of yield weight for the treatments and water depletion rates.

Crecimiento y rendimiento de maíz bajo riego por goteo superficial y subsuperficial

To evaluate the effect of surface and subsurface drip irrigation on the growth and yield of corn, a trial was carried out at the Technical University of Machala-Ecuador, 1,600 m2 of hybrid corn (PIONEER 30K75) were cultivated to apply the treatments: irrigation by surface and subsurface drip at 10, 20 and 30 cm depth. The seed was sown in August 2019 at 80 cm between rows and 40 cm between plants, two seeds per point, with a plant density of 62,500 plants.ha-1. The experimental design was randomized blocks with four treatments and four repetitions. Plant height, fresh and dry biomass of leaves, stalks, and roots, biomass of 100 dry kernels, and yield of dry kernel were evaluated. The highest plant height and biomass of 100 dry kernels was 2.79 m, and 39.08 g, which corresponded to the subsurface drip irrigation treatment at a depth of 30 cm; the highest fresh and dry biomass of leaves, 13,631.3 kg.ha-1 and 3,800 kg.ha-1 respectively, as well as the highest yield of dry kernel 10,337.5 kg.ha-1 was for the subsurface drip irrigation treatment at 20 cm depth. The highest fresh and dry biomass of stalks 32,768.8 kg.ha-1 and 10,381.3 kg.ha-1, and the fresh and dry biomass of roots of 6,381.3 kg.ha-1 and 2,150 kg.ha-1, corresponded to the superficial drip irrigation treatment. With drip irrigation, at 20 and 30 cm depth, higher growth and yield were obtained.

Different pipe burial depths associated with subsurface drip irrigation significantly affected soil gas emissions

AbstractEfforts are needed to reduce soil greenhouse gas emissions from irrigated croplands. Thus, in this study, patterns of soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions in the root zone of tomato plants grown under subsurface drip irrigation (SDI) involving different pipe burial depths were studied, with surface drip irrigation (DI) used as a control (CK). The soil CO2 and N2O emission curves under DI and SDI with pipe burial depths of 10 and 20 cm tended to be similar. In contrast, SDI with a pipe depth of 30 cm resulted in peak CO2 and N2O emissions occurring at different times. The different pipe burial depths led to significantly different spatial distributions of soil water‐filled pore space, which indirectly affected root–soil interactions and soil gas emissions through direct effects on total tomato root fork numbers and microbial community composition. The SDI treatments involving 10‐ and 20‐cm pipe burial depths increased the number of root forks to 1.85 and 2.77 times that in the DI treatment, respectively, and increased the Shannon index of the fungal community by 11.9 and 7.29% compared with that in the DI treatment, respectively. The SDI treatment involving the 30‐cm pipe burial depth resulted in 2.22 times the number of root forks compared with that in the DI treatment; however, the Shannon index of the fungal community decreased by 13.6% compared with that in the DI treatment. As a result, the total soil CO2 emissions and total soil N2O emissions in the SDI treatment involving the 10‐cm pipe burial depth were 1.37 and 2.03 times those in the DI treatment, and those in the SDI treatment involving the 20‐cm pipe burial depth were 1.33 and 2.17 times those in the DI treatment, respectively. In the SDI treatment involving the 30‐cm pipe burial depth, the total amount of soil CO2 emissions was similar to that in the DI treatment; however, the total amount of soil N2O emissions was 28.98% lower than that in the DI treatment. Therefore, soil gas emissions can be reduced by increasing the burial depth of irrigation pipes. These results provide insights into the control of soil gas emissions in agroecosystems.

Drip irrigation mode affects tomato yield by regulating root–soil–microbe interactions

A deep understanding of root–soil–microbe interactions in response to drip irrigation can help optimize drip irrigation techniques and improve crop yield; however, relevant knowledge remains limited. In this study, field experiments were conducted for two consecutive years to investigate the effects of surface drip irrigation (DI), subsurface drip irrigation (SDI), and alternate drip irrigation (ADI) on root–soil–microbe interactions and tomato yield. The results showed that the soil moisture distribution uniformity in the root zone (0–60 cm depth) was reduced in the order SDI > DI > ADI. In the SDI treatment, the tomato root lengths were 4.83- and 3.94-fold higher than those in the DI and ADI treatments, respectively, and the relative abundances of Patescibacteria in the bacterial community and Blastocladiomycota in the fungal community were significantly elevated. In the ADI treatment, the root length was 1.23-fold higher than that in the DI treatment, and the relative abundance of Patescibacteria also increased significantly compared with that in the DI treatment. These changes led to distinct root–soil–microbe interactions. The most intensive positive root–soil–microbe interactions occurred in the SDI treatment, followed by the ADI and DI treatments. The differences in the root–soil–microbe interactions regulated tomato yield. The tomato yield in the SDI treatment was increased by 19.77% and 7.77% compared with that in the DI and ADI treatments, respectively. In the ADI treatment, the tomato yield was 24.09% higher than that in the DI treatment. Therefore, the different drip irrigation methods can regulate tomato yield by affecting root–soil–microbe interactions. The results provide a reference for the optimization of the drip irrigation mode to regulate root–soil–microbe interactions and increase tomato yield.

Growth, water use, and crop coefficients of direct-seeded guayule with furrow and subsurface drip irrigation in Arizona

Crop establishment costs of guayule (Parthenium argentatum A. Gray), a perennial desert shrub that produces natural rubber, can be significantly reduced using direct seeding rather than the traditional practice of transplanting greenhouse-grown seedlings. However, information regarding the irrigation application, crop evapotranspiration (ETc), and crop coefficients (Kc) for managing direct-seeded guayule crops has not been provided. In this study, guayule was direct-seeded in Apr. 2018 in fields at two location in Arizona; Maricopa, on a sandy loam soil and Eloy, on a clay soil, and harvested 23–24 months later in 2020. At each location, five irrigation rates were applied with subsurface drip irrigation (SDI) ranging from 50 to 150 % replacement of ETc (denoted as D50 to D150 treatments), respectively. A 6th treatment using furrow irrigation at 100 % ETc replacement (F100) was included. Treatments were replicated three times. The ETc was estimated for the first 74–84 days of crop establishment and thereafter, actual ETc (ETc act) was determined weekly-biweekly for the D100 and F100 treatments using a soil water balance. The objectives were to evaluate the responses in dry biomass (DB), rubber yield (RY), and resin (ReY) yield to water application rate, develop irrigation management criteria for the two soil types, and determine the ETc and crop coefficients for the 100 % treatments.The total irrigation applied to treatments ranged from 1830−1910 mm to 5090–5470 and averaged 3590 and 3320 mm for the 100 % SDI (D100) and furrow (F100) treatments at Maricopa and Eloy, respectively. The summed estimated ETc plus ETc act for the D100 and F100 treatments were 3663 and 3506 mm at Maricopa, respectively and 3428 and 3320 at Eloy, respectively. Average measured mid-season Kc in the 1st year varied from 1.20 to 1.26. Average measured mid-season Kc in the 2nd year were higher for D100 (≈1.30) than for F100 (≈1.23). Adjusted to the standard climate proposed in FAO56, mid-season Kc are 1.24 for D100 and 1.17 for F100 in the 2nd year. Average DB at Eloy (28.6 Mg ha−1) was not significantly higher than at Maricopa (24.0 Mg ha−1). However, RY and ReY were both significantly higher at Maricopa. At each location, rubber content was significantly higher for the F100 and the two lowest SDI rates than for other treatments. The highest mean RY and ReY were achieved with D100 at Maricopa and D75 at Eloy. These two also had significantly greater water productivity (WP; DB, RY, and ReY per unit of total water applied) than those at higher SDI rates and the F100 treatments. RY and ReY and their WP were generally higher for D100 than F100 in the sandy loam but not in the clay soil. For direct-seeded guayule in clay soils, furrow irrigation should be considered due to the lower rubber content and higher costs associated with SDI.

Effect of dripline depth on the agronomic parameter of eggplant Solanum melongena L. (Solanaceae)

Despite numerous researches investigated on subsurface drip irrigation (SDI), local information about the response of eggplant growth and water dynamics on SDI still very limited in Tunisia. Results showed that lower values of soil water contents were obtained under traditional drip irrigation (DI) treatment, as a consequence of higher evaporative demand. Leaf area, the number of fruits per plant, as well as the crop yield obtained on SDI treatment, resulted significantly higher (P = 0.05) than the corresponding measured on DI treatment. The better performance associated to SDI compared to DI, was due to the minor evaporation losses from the soil surface and consequently higher irrigation water use efficiency. When the drip laterals were buried, the wet bulbs in the soil induced the concentration of roots around the points where water is applied. Moreover, the occurrence of capillary rise could contribute to a redistribution of water stock around zones of active roots.

Reducing Surface Wetting Proportion of Soils Irrigated by Subsurface Drip Irrigation Can Mitigate Soil N₂O Emission.

To reveal the impact of soil moisture distributions on nitrous oxide (N2O) emissions from wet soils irrigated by sub-surface drip irrigation (SDI) with different surface soil wetting proportions, pot experiments were conducted, with surface irrigation (SI) as a control. Results indicated that irrigation triggered N2O pulsing effect in all SDI treatments, yet N2O values reduced with the decrease of surface soil wetting proportions of SDI irrigated soils, and the occurrence times were lagged. The peak N2O fluxes and the corresponding soil water filled pore space (WFPS), as well as the coefficients of determination (R2) of the exponential function between N2O fluxes and soil WFPS, decreased with the reduction of surface soil wetting proportions with SDI treatment, and from the central sub-region to the periphery sub-region. The pulse period contributed most to the reduction of N2O emissions in SDI compared to SI treatments and should be a key period for N2O emission mitigation. Over the whole experimental period, the area-weighted average cumulative N2O fluxes from SDI treatments were 82.3–157.3 mg N2O m−2 lower than those from SI treatment, with periphery sub-regions of R3 and R4 (radius of 19–27 cm and 28–36 cm from the emitter horizontally) contributing to more than 75.8% of the total N2O emission mitigation. These results suggest that reducing surface soil wetting proportions or the increments of topsoil WFPS for SDI irrigated soils is a promising strategy for N2O emission reduction.

Assessment of yield and water productivity of clementine trees under surface and subsurface drip irrigation

Irrigation systems aimed to optimize water use efficiency in agriculture have become essential due to the increasing water limitations that agriculture is currently facing. Assessment of crop responses to different irrigation systems and strategies are therefore encouraged to find the most efficient options for each specific case. The main objective of this study was to assess the performance of a citrus crop under a surface (SI) and subsurface drip irrigation (SSI) with 7 (SI7, SSI7) or 14 emitters (SI14, SSI14) per plant, as well as a third SS treatment (SSIA), identical to SSI7 but equipped with and additional drip line buried between the tree rows. Evaluations were made in terms of yield, fruit composition, irrigation water productivity (IWP) and water savings. Results showed that, on average, water savings were 23.0% in the SSI treatment compared to the SI treatment without significant differences in either yield or fruit composition. IWP was higher in SI14, SSI14 and SSIA than in SI7 and SSI7 treatments. SSIA was the treatment with the lowest irrigation volumes and the highest yield and compared to SI7 allowed, over the three years, water savings in the range between 22.4 and 27.9%. Results from this study illustrate that there is opportunity to substantially save water in citrus production and that further research in this direction is needed to contribute to better optimize the water resources in agriculture.

Evaluation of yield and leaf water potantial (LWP) for eggplant under varying irrigation regimes using surface and subsurface drip systems

This research was carried out to evaluate the effect of various irrigation regimes applied with subsurface and surface drip systems on yield, quality and midday leaf water potential (LWP) on eggplant in the Mediterranean Region of Turkey. The field experiments were carried out during the growing seasons of 2013–2014, in the experimental fields of Soil and Water Resources Research Unit in Tarsus. In the study, two irrigation systems namely surface drip (DI) and subsurface drip systems (SDI); two irrigation intervals (IF3: 3-day; IF6: 6-day) and four irrigation regimes (Full irrigation, FI; deficit irrigations, DI-50; DI-75); and Partial Root-zone Drying PRD-50, which received, respectively 50, 75, and 50% of FI were tested in split-split plot design with four replications. Leaf water potential were measured throughout the growing season with a pressure chamber. Irrigation methods, irrigation intervals and irrigation levels resulted in significantly different yields. Surface drip performed slightly better than the subsurface drip considering yield and quality of eggplants. The highest yield values were obtained from the full irrigation treatments DI IF3FI and SDI IF3FI with 3-day interval. In both trial years PRD-50 treatment in subsurface drip with 6-day interval plots resulted in the lowest yield. The highest water use efficiency (WUE) was found in subsurface drip 6-day interval deficit irrigation (SDI IF6 DI-50) (21.9 and 24.5kgm−3 in 2013 and 2014) and the lowest in subsurface drip 6-day interval PRD-50 (SDIIF6 PRD50) (12.2 and 16.6kgm−3). LWP values in the surface drip irrigation treatments ranged between −1.11 and −1.55MPa in 2013, and ranged between −0.98 and −1.48MPa in the 2014 growing season. In subsurface drip irrigation treatments LWP values ranged between −1.0 and −1.51MPa in 2013 and ranged between −0.91 and −1.43MPa in the 2014. The LWP values decreased with increasing water stress. A significant linear relationship between LWP and yield was obtained. The results revealed that eggplant should be irrigated at LWP values between −0.95 and −1.05MPa (−9.5 ile −10.5bar) for high and good quality yields. Thus, LWP can be used for irrigation scheduling for eggplant.

시설오이 지중관비시 자동관수센서의 적정 매설깊이

시설오이 지중관비에서 지중 점적호스를 30 cm에 매설 시에 텐시오미터를 이용한 자동관수센서의 적정 깊이를 제시하고자 2010-2011년까지 2년간에 걸쳐서 조사하였다. 오이의 생육은 텐시오미터 30 cm 깊이에서 낮았으나 텐시오미터 10 및 20 cm에서는 유의성 있는 차이는 없었다. 1년 및 2년차 수량에서도 텐시오미터 30 cm에서 각각 40.9 및 41.2 <TEX>$Mg\;ha^{-1}$</TEX>로 가장 적은 생산량을 나타내었나, 텐시오미터 10 cm에서는 57.0 및 56.9 <TEX>$Mg\;ha^{-1}$</TEX>, 텐시오미터 20 cm에서는 56.0 및 60.5 <TEX>$Mg\;ha^{-1}$</TEX>로 처리간의 차이가 없이 동일한 수량을 나타내었다. 오이재배에서 한 작기 당 질소 및 일일 물 공급량은 63 <TEX>$kg\;N\;ha^{-1}$</TEX>의 질소와 1.3 <TEX>$mm\;day^{-1}$</TEX>로 물이 공급된 텐시오미터 20 cm 처리에서 질소 및 수분 이용효율이 높았다. 또한 토양깊이 0-30 cm에 대한 뿌리길이에서도 텐시오미터 20 cm에서 0.87 <TEX>$cm\;cm^{-3}$</TEX>으로 유의성은 없었지만 가장 높은 값을 나타내었다. 이러한 결과로부터 시설오이에서 지중 점적호스를 30 cm 깊이에 매설 시에 텐시오미터를 활용한 자동관수센서의 적정 깊이는 20 cm인 것으로 판단되었다. Vegetables production in greenhouse are typically intensely managed with high inputs of fertilizers and irrigation water, which increases the risk of ground-water nitrate contamination. In 2010 and 2011, a study was conducted to determine the appropriate depth of soil moisture sensor for automatic irrigation control to use water and nitrogen efficiently under subsurface drip irrigation (SDI) systems. The irrigation line for SDI placed 30 cm below soil surface and tensiometer was used as soil moisture sensor. Three tensiometer treatments placed at 10 (SDI-T10), 20 (SDI-T20) and 30 cm (SDI-T30) depths below soil surface under SDI. These are also compared to SUR-T20 treatment where tensiometer placed at 20 cm below soil surface under surface drip irrigation (SUR) systems. The growth of cucumber was not statistically different between SUR and SDI without SDI-T30 treatment. Fruit yields (Mg/ha) were 57.0 and 56.9 (SDI-T10), 56.0 and 60.5 (SDI-T20), 40.9 and 41.2 (SDI-T30) and 56.6 and 54.3 (SUR-T20) for 2010 and 2011, respectively. Slightly higher total yield was observed in tensiometer placed 20 cm below the soil surface, although no significant differences were found between SDI-T10 and SDI-T20 under SDI treatments. In addition, nitrogen application rates and daily irrigation rates were lowest in SDI-T20 compared with other SDIs and SUR treatments. Nitrogen and daily irrigation application under SDI-T20 was lower than that under SUR-T20 by 6.0%. These findings suggested tensiometer 20 cm depth under SDI systems was best for cucumber production in greenhouse.

Effect of air injection under subsurface drip irrigation on yield and water use efficiency of corn in a sandy clay loam soil

Subsurface drip irrigation (SDI) can substantially reduce the amount of irrigation water needed for corn production. However, corn yields need to be improved to offset the initial cost of drip installation. Air-injection is at least potentially applicable to the (SDI) system. However, the vertical stream of emitted air moving above the emitter outlet directly toward the surface creates a chimney effect, which should be avoided, and to ensure that there are adequate oxygen for root respiration. A field study was conducted in 2010 and 2011, to evaluate the effect of air-injection into the irrigation stream in SDI on the performance of corn. Experimental treatments were drip irrigation (DI), SDI, and SDI with air injection. The leaf area per plant with air injected was 1.477 and 1.0045 times greater in the aerated treatment than in DI and SDI, respectively. Grain filling was faster, and terminated earlier under air-injected drip system, than in DI. Root distribution, stem diameter, plant height and number of grains per plant were noticed to be higher under air injection than DI and SDI. Air injection had the highest water use efficiency (WUE) and irrigation water use efficiency (IWUE) in both growing seasons; with values of 1.442 and 1.096 in 2010 and 1.463 and 1.112 in 2011 for WUE and IWUE respectively. In comparison with DI and SDI, the air injection treatment achieved a significantly higher productivity through the two seasons. Yield increases due to air injection were 37.78% and 12.27% greater in 2010 and 38.46% and 12.5% in 2011 compared to the DI and SDI treatments, respectively. Data from this study indicate that corn yield can be improved under SDI if the drip water is aerated.

Optimizing productivity and irrigation water use efficiency of pearl millet as a forage crop in arid regions under different irrigation methods and stress

A field experiment was carried-out at the Agriculture Experimental Station of King Abdulaziz University located at Hada Alsham, 110 km north east of Jeddah, to optimize the productivity and irrigation water use efficiency of pearl millets (Pennisetum glaucum L.), as green fodder under different irrigation methods and stress. Five treatments were investigated in this study: three with full irrigation requirements including sprinkler irrigation (SPI), drip irrigation (DI) and sub-surface drip irrigation (SDI), the remaining two treatments were stress treatment namely: sub-surface drip kept at 85% of field capacity (SDI 1) and sub-surface drip kept at 70% of field capacity (SDI 2). Irrigation water for all treatments was precisely supplied using water electronics module (WEM). Results indicated that SDI treatment gave the highest fresh and dry biomass, followed by SDI 1 compared to other treatments. Increasing number of cuts sharply decreased biomass production. Increasing water stress decreased biomass production but SDI with water stress increased biomass production compared to SPI with full irrigation requirement. Irrigation water use efficiency (IWUE) was decreased by increasing water stress and number of cuts. Results also proved that WEM is a practical tool to precisely supply irrigation water when needed, and can be effectively used to precisely control water stress. Key words: Irrigation methods, pearl millet, precision irrigation, water stress.

地下滴灌下土壤水势对毛白杨纸浆林生长及生理特性的影响

在6、7年生三倍体毛白杨(triploid <em>Populus tomentosa)</em>纸浆林中研究了地下滴灌(SDI)下不同土壤水势(-25、-50、-75 kPa,即灌溉起始阈值)对林木生长及生理特征的影响。结果表明:与不灌溉(CK)相比,SDI使6、7年生林分的生产力分别平均提高24%和28%;其中,-25 kPa使6年生林分的生产力达到39.90 m³ hm^-2a^-1,较CK极显著提高43.5%(<em>P</em><0.01)。各水势处理间,-25 kPa的生产力在林分6年生时分别较-50和-75 kPa极显著提高20%和31%(<em>P</em><0.01),在7年生时分别提高13%和14%(<em>P</em>>0.05)。能在毛白杨速生期内(4-7月)大幅提高土壤含水率(20和50 cm处分别平均提高35%和27%)、树干日平均液流速率(46%,SF_mean)、黎明前叶水势(41%,<em>ψ</em>_pd)是SDI促进林木生长的重要机制。灌溉起始水势阈值的差异对毛白杨SF_mean和<em>ψ</em>_pd无显著影响(<em>P</em>>0.05)。3个水势处理中,-25 kPa的平均SF_mean和<em>ψ</em>_pd均最高,且其能使根系活动剧烈的表土层(0-20 cm)的水分有效性有最大幅的提高,这可能是其对林木生长有最大促进作用的主要原因。综上,应在毛白杨纸浆林培育中大力推广SDI,并在应用时可将距滴头10cm、地下20 cm处的土壤水势达到-25 kPa作为灌溉起始阈值。另外,在与试验地环境相似地区栽植毛白杨时,应于4-7月灌溉,8-10月一般可不灌溉。;Subsurface drip irrigation (SDI) is an intensive silvicultural practice which has the potential to increase productivity of triploid <em>Populus tomentosa</em> pulpwood plantations. In order to efficiently apply SDI in the cultivation of <em>P. tomentosa</em> pulpwood plantations, it is necessary to determine irrigation timing. A field experiment was conducted to investigate the effect of soil water potential (<em>ψ</em>_soil) on the growth and physiological characteristics of 6-7 year old trees under SDI in a <em>P. tomentosa</em> pulpwood plantation. The experiment included three <em>ψ</em>_soil treatments, which initiated irrigation when the <em>ψ</em>_soil at 20 cm soil depth and 10 cm distance from a drip emitter reached -25, -50, and -75 kPa, respectively. A control non-irrigation treatment (CK) was also included. Meteorological factors, <em>ψ</em>_soil, groundwater level, and tree growth were monitored hourly, daily, every 1-10 days, and monthly for two years, respectively. Soil water content at 20 and 50 cm depth, pre-dawn leaf water potential (<em>ψ</em>_pd), and trunk sap flow rate were measured in selected periods. Results showed that relative to CK, SDI could improve diameter, height, and individual volume increment of <em>P. tomentosa</em>. Irrespective of SDI treatment, SDI on average increased annual volume growth of the 6- and 7-year-old plantations by 24% and 28%, respectively over the CK treatment. Annual volume growth of the 6-year-old plantation following the -25 kPa treatment reached 39.90 m³ hm^-2a^-1, which was 43.5% higher than the CK treatment (<em>P</em><0.01). Relative to the -50 and -75 kPa treatments, annual volume growth in the -25 kPa treatment was 20% and 31% higher (<em>P</em><0.01) in the 6-year-old plantation, respectively, and 13% and 14% higher (<em>P</em>>0.05) in the 7-year-old plantation, respectively. Relative to CK during the fast growing period (April-July) of <em>P. tomentosa</em>, SDI increased the soil water content at 20 and 50 cm depth by 35% and 27%, respectively; increased average daily trunk sap flow rate (SF_mean) by 46%; and increased <em>ψ</em>_pd by 41%. The <em>ψ</em>_soil threshold for initiating irrigation had no significant effect (<em>P</em>>0.05) on the SF_mean and <em>ψ</em>_pd of <em>P. tomentosa</em>. However, among the three <em>ψ</em>_soil treatments, the average SF_mean and <em>ψ</em>_pd values were highest following the -25 kPa treatment. The increase of soil water availability in the 0-20 cm soil layer (i.e., active rooting zone) was also greatest in the -25 kPa treatment. These results may explain why the -25 kPa treatment had the highest tree growth rate among the three <em>ψ</em>_soil treatments. Overall, the observed increase in soil water content, SF_mean, and <em>ψ</em>_pd indicate that these are the mechanisms by which SDI significantly improves <em>P. tomentosa</em> tree growth. In conclusion, our findings suggest that SDI should be promoted in the cultivation of <em>P. tomentosa</em> pulpwood plantations. To realize optimum tree growth, irrigation should be initiated when the <em>ψ</em>_soil at 20 cm depth and 10 cm distance from a drip emitter reaches -25 kPa. Furthermore, it is recommended that irrigation should be applied between April and July, and terminated between August and October when planting <em>P. tomentosa</em> in regions similar to our experimental plantation.

Subsurface Drip Irrigation Placement and Cotton Irrigation Water Requirement in the Tennessee Valley

Fluctuations in dryland cotton yield in the Tennessee Valley region of northern Alabama are common and are usually related to irregular drought periods during the growing season. Subsurface drip irrigation (SDI) has gained popularity as a water delivery system for small, irregular-shaped cotton fields. A seven-year study was conducted with the objective to determine the response of seed cotton yield to SDI tape orientation relative to crop row direction and different irrigation rates under dryland conditions of the Tennessee Valley. Seven treatments were tested in a randomized incomplete block design which consisted of three irrigation treatments (33%, 66%, and 99% pan evaporation), two SDI tape orientations (parallel and perpendicular), and a dryland control. All SDI treatments produced yields significantly higher than non-irrigated, dryland cotton in four out of seven years. Maximum yield was obtained at a median pan evaporation water replacement value of 74%. No statistical differences were observed between SDI tape orientations on seed cotton yield in all years except in 1999 when parallel out yielded perpendicular at lower irrigation rates. Results confirm the long-term efficacy of supplemental irrigation to increase seed cotton yield irrespective of SDI tape placement during sporadic periods of drought. These results are applicable only for fields with the same soil type or with similar water movement characteristics.

SDI Dripline Spacing Effect on Corn and Soybean Yield in a Piedmont Clay Soil

A subsurface drip irrigation (SDI) system was installed in the Piedmont of North Carolina in a clay soil in the fall of 2001 to test the effect of dripline spacing on corn and soybean yield. The system was zoned into three sections; each section was cropped to either corn (Zea mays L.), full-season soybean [Glycine max (L.) Merr.], or winter wheat (Triticum aestivum) double cropped to soybean representing any year of a typical crop rotation in the region. Each section had four plots; two SDI plots with dripline spacing at either 1.52 or 2.28 m, an overhead sprinkler irrigated plot, and an unirrigated plot. There was no difference in average corn grain yield for 2002–2005 between dripline spacings or between either dripline spacing and sprinkler. Irrigation water use efficiency (IWUE) was greater for sprinkler irrigated corn than for either SDI treatment and there was no difference in IWUE in soybean. Water typically moved laterally from the driplines 0.38 to 0.50 m. SDI yield and IWUE increased relative t...

Sustainable domestic effluent reuse via subsurface drip irrigation (SDI): alfalfa as a perennial model crop

Scarcity of fresh high-quality water has heightened the importance of wastewater reuse primarily in dry regions together with improving its efficient use by implementing the Subsurface Drip Irrigation (SDI) method. Sustainable effluent reuse combines soil and plant aspects, along with the maintainability of the application system. In this study, field experiments were conducted for two years on the commercial farm of Revivim and Mashabay-Sade farm (RMF) southeast of the City of Beer-Sheva, Israel. The purpose was to examine the response of alfalfa (Medicago sativa) as a perennial model crop to secondary domestic effluent application by means of a SDI system as compared with conventional overhead sprinkler irrigation. Emitters were installed at different depths and spacing. Similar amounts of effluent were applied to all plots during the experimental period. The results indicated that in all SDI treatments, the alfalfa yields were 11% to 25% higher than the ones obtained under sprinkler irrigated plots, besides the one in which the drip laterals were 200 cm apart. The average Water Use Efficiency (WUE) was better in all SDI treatments in comparison with the sprinkler irrigated plots. An economic assessment reveals the dependence of the net profit on the emitters' installation geometry, combined with the return for alfalfa in the market.

Utilizing Subsurface Drip Irrigation and Conservation Tillage in Cotton Production Systems

Ground water resources for irrigated agriculture are becoming increasing limited in semiarid regions of the world. Subsurface drip irrigation (SDI) and a no-till conservation tillage system were evaluated over 3 years on cotton (Gossypium hirsutum, L.) production and fiber quality in north Texas. Subsurface drip irrigation significantly increased cotton yields over that from furrow irrigation in 2 of 3 yr. When averaged over 3 yr, the cover crop treatments on 1 and 2 m drip line spacing and a 100% ET replacement yielded numerically more than the companion treatments without a cover crop. Across years, the SDI treatments significantly increased loan values by an average of $ 0.045 k g − 1 over furrow-irrigated cotton. Within SDI, deficit irrigation did not appear to affect cotton yield in proportion to the amount of restricted irrigation. In 2003, a 50% reduction in ET replacement under conventional tillage reduced yield only 22%, indicating that a 100% ET replacement may not be necessary to produce economically acceptable yields. Results from this study provide preliminary evidence that cover crops may actually prove beneficial under SDI systems and could play a role in developing best management practices that incorporate conservation tillage practices.