Subsurface Drip System Research Articles

Effects of Fertigation Treatment Using a Subsurface Drip System on Spring Potato (Solanum Tuberosum L.) Growth and Yield

Background: In potato, irrigation and fertilization significantly affect yield. Subsurface drip irrigation and fertigation system are very effective in supplying water and fertilizers directly to crop root zones. Objective: This study was conducted to investigate the effect of fertigation treatment according to fertilizer concentration and composition on spring potato growth and yield using a subsurface drip system. Methods: Fertilizers containing nitrogen, phosphoric acid, and potassium were applied at various concentrations and fertilizer compositions during the tuber initiation and filling stages to determine the appropriate fertilizer concentration. And then, the selected EC 1.0 (NK) and K single-use treatments (K 20, K 50, and K 70 kg, ha-1) were used for fertigation treatment with a subsurface drip system. Results: The nutrient uptake by fertilizer concentration results for spring potato cultivation confirmed that nutrient absorption was best at EC 1.0. Accordingly, based on EC 1.0, the nutrient uptake rate by fertilizer composition (EC 1.0; NPK, NK, K) was the best in the NK and K treatments. The application of K 50 (50 kg ha-1) for subsurface fertigation had the highest yield, with an approximately 61% increase over the control treatment and a 19% increase over the irrigation treatment. Conclusion: Fertigation treatment using the surface drip system at the tuber initiation and filling stages will contribute to the stable production and improvement of potato productivity by increasing the efficiency of water and fertilization.

A Multi-sensor Analysis of Selected Reflectance-Based Crop Coefficient Models for Daily Maize Evapotranspiration Estimation

This study evaluated three reflectance-based crop coefficient models (RBCC) for daily maize actual evapotranspiration (ETa) estimates, using multispectral data from spaceborne, airborne, and proximal platforms. The goal was to identify the optimal multispectral sensor that gives more accurate daily ETa estimates. The remote sensing (RS) multispectral platforms included Landsat-8, Sentinel-2, Planet CubeSat, handheld multispectral radiometer (MSR), and unmanned aerial system or UAS, spatial resolution from 30 m to 0.03 m. Three RBCC models that use different vegetation indices as input variables were evaluated in the study. One RBCC uses the normalized difference vegetation index (NDVI). The second model uses the soil-adjusted vegetation index (SAVI), and the third model uses canopy cover (fc). The data for this study were from two maize research sites in Greeley and Fort Collins, Colorado, USA, collected in 2020 and 2021. The Greeley site had a subsurface drip system, while the Fort Collins site had surface irrigation (furrow). Daily maize ETa predictions were compared with observed daily maize ETa data from an Eddy Covariance system installed at each research site. Results indicated that, depending on the RS of ETa algorithm and platform, the optimal input RS data was different. The MSR sensor (1 m) provided the best remote sensing data (input) for the SAVI-based RBCC ETa model, with a maize ETa error (MBE±RMSE) of -0.13 (-3%)±0.67 (16%) mm/d. Sentinel-2 was the best sensor for the remaining two RBCC daily maize ETa algorithms, since the errors for the NDVI-based and fc-based RBCC models for maize ETa were 0.21 (5%)±0.78 (18%) mm/d and 0.59 (14%)±1.07 (25%) mm/d, respectively. These results indicate the need for methods to improve the spectral quality of the remote sensing data to improve spatial ETa estimates and advance sustainable irrigation water management.

Introducing a stratified vertical gravel tube subsurface drip system under different irrigation regimes for pistachio: Growth, yield and water productivity

AbstractHigh evapotranspiration and low precipitation are known as the main challenging factors for pistachio (Pistacia vera L.) orchards situated in arid and semi‐arid regions. Therefore, it is necessary to take some measures to mitigate surface evaporation. This study was carried out to assess water productivity (WP) as well as yield and annual shoot growth of pistachios using a new method of irrigation known as the stratified vertical gravel tube subsurface drip irrigation (SVGTSD) system in a 15‐year‐old pistachio orchard in an arid region in Iran. In this system, each tree contained four vertical gravel columns with different lengths. A randomized complete block design with a split‐plot arrangement with three replicates (five trees in each plot) for 3 years was used. Three irrigation regimes included 100% crop evapotranspiration (100% ETc), 85% ETc and 70% ETc (as the main plots), and seven vertical gravel column with a depth arrangement of 40–40–40–40 cm (using a gravel column from the lateral pipe level and without a gravel tube as the control) and gravel‐filled tubes with depths of 10–10–10–10 cm, 10–10–20–20 cm, 10–10–30–30 cm, 10–10–20–30 cm, 10–10–20–40 cm and 10–10–20–50 cm (all 30 cm below ground level) (as subplots) were used. The results showed that the different depths of gravel tube placement significantly affected the annual shoot growth and yield. The deeper the tube was placed, the greater the yield and annual shoot growth, resulting in 10–10–20–50 cm being the most productive. Regarding tree growth, yield and WP, the best performance was observed at full irrigation (100% ETc) with a 10–10–20–50‐cm vertical gravel tube arrangement. Furthermore, in this subsurface irrigation method, there was no concern regarding emitter clogging by roots, root accumulation around the emitters or root intrusion into the emitters. In addition, having a low additional cost (only 13.9%) in comparison with conventional subsurface drip irrigation together with a higher yield (3475 kg ha−1), WP (0.9 kg m−3) and shoot growth (35 cm), SVGTSD is more economical and feasible compared to other irrigation methods and can be extensively applied in pistachio orchards.

Effect of using reclaimed water via furrow and subsurface drip systems under alternate partial root-zone irrigation mechanism on crops growth and soil properties

The growing population in the face of water scarcity inevitably necessitates the quest for alternative sources of irrigation water, which integrates them with irrigation strategies for improved agricultural productivity to meet the Sustainable Development Goals. A three-year field experiment was conducted in 2017, 2018, and 2019 to investigate the effect of water quality (reclaimed water (RW) and clean water (CW)), irrigation techniques (subsurface drip irrigation (SDI) and furrow irrigation (FUI)), irrigation methods (full irrigation (FI) and alternate partial root-zone irrigation (APRI) (70% ETc)), and their interactions on the fresh fruit yield (FY), irrigation water use efficiency (IWUE), and nitrogen use efficiency (NUE) of tomatoes. Further, electrical conductivity (EC), pH, and organic matter (OM) of soil were evaluated. The experiments were undertaken over three growing spring seasons in a greenhouse at the Chinese Academy of Agricultural Sciences in Henan Province, China. Throughout the three years of this study, the yield, the IWUE, and the NUE values of all treatments under RW were higher than those corresponding values under CW. The trend was the same under SDI as it was under FUI. Statistical analyses revealed that there was no significant effect (P > 0.05) of water quality, irrigation technique, and irrigation methods on the soil EC, pH, and OM over the three years. In addition, the interaction between the different experimental factors over the three years of the study was not significant. In conclusion, the application of RW under SDI can result in saving CW and increasing productivity without any negative effect on the investigated soil properties. Furthermore, when RW-SDI is used in conjunction with APRI, it can result in increasing IWUE.

Growth and yield responses of soybean according to subsurface fertigation

AbstractTo increase soybean [Glycine max (L.) Merr.] yield, appropriate amounts of water and fertilizer are required at optimal times from sowing to maturity. This study was conducted to investigate how soybean growth and yield were affected by irrigation and fertigation using a subsurface drip system, which consisted of a buried (40‐cm underground) drip pipe that can be used in a semipermanent manner without affecting agricultural work on the ground. The amount of water required for the fertigation treatment was determined to be 176 t ha−1 with the sandy loam soil in this experimental field. Fertigation treatments based on 176 t ha−1 were carried out as topdressing applications and were applied through the subsurface drip system based on the fertilizer concentration (nitrogen only: N 20, N 40, N 60 kg ha−1, or compound fertilizer, that is, NPK 1/2 [half of the standard fertilizer amount applied as 16–16–18]). The other treatments included irrigation only and control (nontreatment). The results indicated that the N 20 treatment was the most effective, increasing yield by 83% compared with the control, whereas the N 40, N 60, and NPK 1/2 treatments produced slightly lower yields. In terms of fertigation, an excessive fertilizer concentration increased the growth of aboveground parts but reduces nodulation and yield. These results highlight the effectiveness of fertigation as a form of topdressing fertilization using a subsurface drip system for achieving a high yield and stable soybean production.

Assessment of crop water stress index and net benefit for surface- and subsurface-drip irrigated bell pepper to various deficit irrigation strategies

AbstractThis study addresses the assessment of crop water stress index (CWSI) of bell pepper (Capsicum annuum L.) and net income generated under regulated deficit irrigation (RDI), conventional deficit irrigation and partial root-zone drying (PRD) and full irrigation (I100) using surface- and subsurface-drip systems (DI and SDI) during 2016 and 2017 in the Mediterranean region. The experimental design was split-plots with four replications. RDI was supplied with 50% of I100 during vegetative stage until flowering, then received 100% of crop water requirement. PRD50 received 50% of I100, but from alternative laterals each watering. The results revealed that CWSI was correlated significantly (P < 0.01) and negatively with yield, yield per plant, total soluble solid, ETa, fruit weight and plant height indicating that yield of bell pepper declined with increasing CWSI values (P < 0.01). Bell pepper should be irrigated at mean CWSI value of 0.20 without any yield reduction. CWSI in the RDI and I75 treatments were slightly greater than 0.20. Irrigation treatments had significant effect on yield and quality traits. The highest total soluble solutes were found in PRD50 and I50. The DI I100 treatment generated the highest net income followed by the SDI I100 and RDI. In conclusion, RDI and I75 appear to be good alternatives to I100 for sustainable bell pepper production in the Mediterranean region.

Yield, dry matter and water productivity simulation for surface and subsurface drip-irrigated bell pepper using the SALTMED model

AbstractSALTMED model performance was evaluated by comparing simulated and observed soil water content, dry matter (DM) yield, yield and water productivity (WP) data of field-grown bell pepper (Capsicum annuum L.) under Mediterranean climatic conditions irrigated with surface and subsurface drip systems. Simulation data were obtained from field experiments performed in 2016 and 2017. Treatments were full irrigation (I100), conventional deficit irrigation at 75 and 50% actual crop evapotranspiration (ETa; I75 and I50), regulated-deficit irrigation (RDI) and partial root-zone drying (PRD) at 50% ETa using surface (SfDI) and subsurface drip systems (SbDI) on a clay-loam soil, in a split-plot with four replications. Results showed that 56 and 29 mm less irrigation water was applied to SdDI100 in 2016 and 2017, respectively, than SfDI100; RDI used 27 and 77 mm less irrigation water than SfDI100 in experimental years, respectively. SbDI and SfDI performed similarly for bell pepper yield, DM and WP. However, the effect of irrigation treatments on yield, DM and WP was significant. I100 showed the highest yield (74.9 and 71.1 t/ha in 2016 and 2017, respectively), followed by RDI in 2016; I100, RDI and I75 produced greater yield than other treatments in 2017. PRD50 and I50 produced the least yield (49.8 and 45.9 t/ha in 2016 and 2017, respectively). SbPRD50 and SbI50 had the greatest WP value under SbDI in the experimental years. Results showed that the SALTMED model simulated yield, DM, soil water content and WP reasonably well (R2 = 0.95, 0.97, 0.98 and 0.74, respectively).

Comparison of aerobic rice cultivation using drip systems with conventional flooding

AbstractIn this study, yield and water productivity response of rice to various irrigation levels applied with subsurface and surface drip systems in 2019 and 2020 in the Mediterranean Region of Turkey was evaluated in comparison with conventional flooding (CF). The treatments consisted of two irrigation methods namely surface drip (DI) and subsurface drip systems (SDI), three irrigation levels designated as plant pan coefficients (I1.00: Evaporation from Class A pan (Ep) × 1.00; I1.25: Ep × 1.25 and I1.50: Ep × 1.50) and CF as control. The effects of drip systems and coefficients on yield and yield components were statistically significant (P < 0.01). DI produced higher yield than SDI. CF produced significantly greater yield than both DI and SDI systems. With two drip systems, average water savings of 60.5% in I1.00, 54.5% in I1.25 and 49% in I1.50 were achieved as compared to CF. However, yield reductions of 15% in I1.50, 20% in I1.25, 29% in I1.00 were observed for DI; corresponding values for SDI were 20, 28 and 44%, respectively. Drip irrigation in aerobic rice production system had almost twice the water productivity based on total irrigation water applied (WPI) or total water input (irrigation + rainfall) (WPI+P) compared with CF. During the study years, the highest WPI and WPI+P values were found in DI-I1.00 (0.81–0.73 kg/m3) and (0.85 and 0.74 kg/m3), respectively. In conclusion, DI-I1.50 treatment is recommended for sustainable aerobic rice production since DI-I1.50 resulted in water saving of 49% but yield decrease of 15% as compared to CF.

Agro-hydrological models and field measurements to assess the water status of a citrus orchard irrigated with micro-sprinkler and subsurface drip systems

ISHS International Symposium on Precision Management of Orchards and Vineyards Agro-hydrological models and field measurements to assess the water status of a citrus orchard irrigated with micro-sprinkler and subsurface drip systems

Yield and water productivity response of quinoa to various deficit irrigation regimes applied with surface and subsurface drip systems

AbstractThis study evaluated the yield and water productiivty response of quinoa to regulated deficit irrigation (RDI), partial root-zone drying (PRD) and conventional deficit irrigation (DI) and full irrigation (FI) using surface (SD) and subsurface drip (SSD) systems in 2016 and 2017 in the eastern Mediterranean region of Turkey. The treatments consisted of RDI, PRD50, DI50, DI75 and FI. A rainfed treatment (RF) was also included in the study. The experimental design was split plots with four replications. DI75 and DI50 received 75 and 50% of FI, respectively. PRD50 received 50% of FI, but from alternative laterals. RDI received 50% of FI during vegetative stage until flowering, and then received 100% of water requirement. The results showed that quinoa under SD used slightly more water than SSD due to reduced surface evaporation. RDI resulted in water saving of 23 and 21% for SD and SSD, respectively, compared to FI; and RDI produced statistically similar grain yields to FI. DI75 treatment resulted in water savings of 16% for both drip methods in the first year and 10 and 25% for SD and SSD systems, respectively, in the second year. PRD50 produced greater yield than DI50 eventhough they received the same amount of irrigation water. RF and PRD50 treatments resulted in significantly greater water productivity (WP) values than other treatments. There was no significant difference between SD and SSD regarding the grain and dry matter yields and WP values. Thus, RDI and DI75 appear to be good alternatives to FI for sustainable quinoa production in the Mediterranean region.

Irrigation with treated wastewater containing nanobubbles to aerate soils and reduce nitrous oxide emissions

The objective of the present study was to examine whether we could improve the aeration of clayey soils that had been degraded by long-term irrigation with treated wastewater (TWW) through drip irrigation with TWW aerated with oxygen (O2) nanobubbles (ONB). A lysimeter set-up was irrigated using surface and subsurface drip systems, and the effects of those systems on soil oxygen concentration, nitrogen transformations, nitrous oxide (N2O) emissions, and crop yield were investigated. In the surface drip system, irrigation with ONB-aerated TWW increased soil oxygen concentrations from 15.6% to 19.7% (p = 0.0001). In the subsurface drip system, soil oxygen concentrations increased from 18.2% to 19.2% (p = 0.0266). In all treatments, nitrate was the dominant N form in the root zone porewater (soil solution) and leachates. Nitrite concentrations were low in all treatments (<4 mg L−1), yet a clear daily accumulation pattern (from ∼0.05 to ∼1.0 mg L−1) was observed in the ONB-aerated treatments. Irrigation with ONB-aerated TWW reduced cumulative N2O emissions by 37% in the surface irrigation system and 14% in the subsurface irrigation system. Our results imply that irrigation with ONB-aerated TWW may be an effective way to improve soil aeration, especially in clayey soils that have been degraded by prolonged irrigation with TWW. Such practices may reduce N2O production and the overall N leakiness of agricultural activity.

Evaluation of crop water stress index and leaf water potential for differentially irrigated quinoa with surface and subsurface drip systems

A 2-year field experiment was conducted with the objectives to evaluate the physiological and yield response of quinoa cv Titicaca to various deficit irrigation strategies applied with surface drip (SD) and subsurface drip systems (SSD) under the Mediterranean climatic conditions in 2016 and 2017. The treatments consisted of regulated deficit irrigation (RDI), partial root-zone drying (PRD50), conventional deficit irrigations (DI50, DI75) and full irrigation (FI) under SD and SSD. A rainfed treatment was also included. The experimental design was split plots with four replications. DI75 and DI50 received 75 and 50% of FI, respectively. PRD50 plots received 50% of FI, but from alternative laterals in each application. RDI received 50% of FI during vegetative stage until flowering, then received 100% of water requirement. The results indicated that RDI resulted in water saving of 23 and 21% for surface drip (SD) and SSD systems, respectively, and RDI produced statistically similar yield to FI treatment in both experimental years. DI75 treatment resulted in water savings of 16% for both drip methods in the first year and 10 and 25% for SD and SSD systems, respectively, in the second year. Thus, RDI and DI75 treatments appear to be good alternative to FI for sustainable quinoa production in the Mediterranean environmental conditions. Greater leaf water potential (LWP) and smaller crop water stress index (CWSI) values were measured in FI plots under both drip systems than deficit irrigation treatment plots. Significant second-order polynomial relations were determined between CWSI and LWP for the drip systems. Leaf area index (LAI), LWP decreased and CWSI increased as the drought increased. CWSI correlated significantly (P < 0.01) and negatively with grain yield, dry matter yield, LAI, and mean soil water content indicating that grain yield of quinoa declined with increasing CWSI values. All these relations are best described by significant second-order polynomial equations. The results revealed that quinoa should be irrigated at LWP values between − 1.35 and − 1.60 MPa, and average CWSI value of approximately 0.35 for high yields.

Підземне крапельне зрошення. Технічне забезпечення та застосування

Підземне крапельне зрошення. Технічне забезпечення та застосування

Preplant and early-season cotton irrigation timing with deficit amounts using subsurface drip (SDI) systems in the Texas High Plains

Two major irrigation challenges of cotton producers in the Texas High Plains (THP) include the depletion of the Ogallala Aquifer and the highly evaporative, semi-arid environment during late spring and early summer. A recent cotton experiment using center pivot irrigation at deficit irrigation capacities showed the reduction in seasonal irrigation by 20% with minor yield loss by reducing irrigations during the vegetative period instead of attempting to store soil water during this period of high evaporative losses. Due to its method of delivery, subsurface drip irrigation (SDI) should reduce evaporation losses during the preplant and early-season periods and improve water storage efficiency and crop yield even at low irrigation capacity. Two experiments having different SDI installation designs and irrigation capacities were conducted in adjacent fields on clay loam soils over 4- and 5-year periods. Treatments included levels of preplant (PP) and vegetative (Veg) period irrigations. In both experiments, under seasonal growing conditions ranging from favorable to unfavorable, yields and crop values were only modestly increased by additional PP irrigations above that required for germination. Among treatments with common PP amounts, larger irrigation amounts during the vegetative period did not significantly (p < 0.05) increase yield or crop value in any individual year or any group of years. In three growing season groupings, with unfavorable to favorable weather conditions, as seasonal irrigation increased, gross irrigation value decreased. Results suggest that in most years, on heavy soils within the THP, SDI productivity can be improved by limiting PP and early-season irrigations under deficit irrigation conditions.

Tomato production as a function of aeration levels after subsurface drip irrigation

ABSTRACT After rain or irrigation, the soil pores may present a low oxygen content (hypoxia). Soil aeration after irrigation has been used to overcome hypoxia-based problems. This study aimed to investigate the effect of four aeration levels (0, 0.5, 1.0 and 1.5 times the standard volume) applied after irrigation, using a subsurface drip system, at two soil depths (0.15 m and 0.30 m). A randomized block design was used, in a 4 x 2 factorial scheme, with six replications. The yield characteristics assessed were: total fruit mass per plant, average fruit mass and number of fruits per plant. The growth characteristics were root and stem dry mass. The water-use efficiency was also calculated. The results indicated that the highest aeration level, at a depth of 0.30 m, increased the yield by 41.2 %, when compared with plants that received only irrigation, at the same depth. The water-use efficiency was influenced by the soil aeration after irrigation only at the depth of 0.30 m.

Crop rotation, irrigation system, and irrigation rate on cotton yield in southwestern Georgia

AbstractLong‐term yield data would be useful for determining crop rotation, irrigation system selection, and irrigation rate for maximum production and economic sustainability. Research was conducted at the USDA–ARS National Peanut Research Laboratory's Multi‐crop Irrigation Research Farm in Shellman, GA (84°36″ W, 30°44″ N), on a Greenville fine sandy loam (a fine, kaolinitic, thermic Rhodic Kandiudult) soil with 0–2% slope. This long‐term study (2001–2013) compared three irrigation systems, three cotton (Gossypium hirsutum L.) crop rotations, and various irrigation rates on cotton lint yield and quality factors. Irrigation systems were sprinkler, subsurface drip (SSDI), and shallow subsurface drip (S3DI) irrigation compared with a dryland control. Irrigation rates were 100, 66, 50, 33, and 0% of estimated water use. Crop rotations were (a) cotton–corn (Zea mays L.)–peanut (Arachis hypogaea L.), (b) cotton–cotton–peanut; and (c) cotton–peanut–cotton. There was no difference in cotton yield by crop rotation. Sprinkler and S3DI systems had greater lint yield than the SSDI system at the 100% irrigation level when averaged across all years and rotations. Lint yield tended to be lower in high rainfall years without respect to irrigation system. Irrigation increased lint yield by an average 10% when rainfall was less than average. All fiber quality factors were within acceptable ranges without any value discounts across years, rotation, or irrigation system. Irrigation system selection should not be based entirely on long‐term yield information but also on field size, system installation cost, irrigation system controls, and crop management.

Yüzeyaltı Damla Sulama Yöntemiyle Sulanan Yalova İncisi Sofralık Üzüm Çeşidinde Yaprak Su Potansiyeline Göre Sulama Programının Oluşturulması

This research was carried out in the Eastern Mediterranean Region of Turkey where to determine the effects of various irrigation strategies applied with subsurface drip systems on Yalova Incisi table grape variety and yield and water use efficiency along with optimal irrigation program during 2016, in the experimental fields of Alata Horticultural Research Station, Tarsus Soil and Water Resources Topcu Unit. In the study six irrigation levels (Full irrigation, TS; deficit irrigation, KS75; deficit irrigation, KS50; Partial Root-Zone Drying PRD75% , Partial Root-Zone Drying PRD50% of full irrigation treatments and Rainfed, RF) were tested. Soil water deficit in the rootzone depth was replenished to field capacity in irrigations. The experimental was carried out in randomized block design with three replications. The effect of the irrigation levels on the yield were found statistically significant. Full irrigation treatment under the produced the highest yield (30.9 t ha-1), the lowest yield was obtained in rainfed treatment plots (11.7 t ha-1). Leaf water potantial were measured throughout the growing season with a pressure chamber. The YSP values decreased with increasing water stress. Highest yields of Yalova Incisi variety can be obtained when irrigated at leaf water potential value Ψ =0.92 MPa.

Effects of three irrigation systems on ‘Piel de sapo’ melon yield and quality under salinity conditions

The melon crop is moderately sensitive to soil salinity and, as a consequence, its yield decreases under saline conditions. Nevertheless, the exposure to moderate salinity also influences the melon quality by improving it, which offers compensation to the farmer. As a consequence, in moderately salt-affected lands, like the traditional irrigation area of the ‘Vega Baja del Segura’ (Alicante, Spain), melons are being grown. In this area the modernization of the secular irrigation system through the replacement of flood by drip systems, is currently being fostered. This fact, however, is generating some controversy, due to the known salt leaching effect that flood irrigation followed by drainage makes in the soil. In this study, the effects of three irrigation systems, namely, drip (DI), subsurface drip (SDI) and flood (FI), on soil salinity and thus, on the yield and quality of the melon, were compared. According to the results, the FI system kept the soil salt levels during the growth period at 4.1 ± 0.3 dS/m, that is, significantly lower than the 4.7 ± 0.2 dS/m attained with the DI and SDI systems. Nevertheless, the DI and, overall, SDI, provided higher and more homogenous soil moisture completely counteracting the effect of salinity as revealed by the soil water potential calculations. As a result, the SDI gave 27 ± 5 Mg/ha of total yield in comparison to 23 ± 2 Mg/ha (DI) and 20 ± 6 Mg/ha (FI). Besides, the SDI system reduced the number of damaged melons, thus additionally contributing to the significant higher marketable yield of the SDI (25 ± 4 Mg/ha) in comparison to the DI (20 ± 1 Mg/ha) and the FI (19 ± 7 Mg/ha). On the contrary, in the SDI treatment the fruit soluble solids content, tritatable acidity and pulp firmness decreased a bit, however, in the sensory evaluation no differences among irrigation treatments were observed.

HYDRUS-2D simulations of water and potassium movement in drip irrigated tropical soil container cultivated with sugarcane

Subsurface drip irrigation is increasingly being used for sugarcane production in Southeast Brazil in attempts to conserve water, especially after extreme droughts in 2014 and 2015. Correct design of a subsurface drip system is essential to provide information about water and solutes dynamics in the subsurface, leading to possible water savings. While field investigations demand much time and financial resources, numerical models can also provide much information about expected water and solute distributions in the soil profile. The objective of this study was to use HYDRUS-2D for simulations of water and potassium movement in containers packed with a subsurface drip-irrigated tropical soil cultivated with sugarcane and comparing simulated and observed data through statistical parameters. Investigations were carried out in a greenhouse during 240 days after the tillering stage. Spatial and temporal distributions of water content and potassium concentrations were collected using Time Domain Reflectometry (TDR) to calibrate and validate HYDRUS-2D. Simulations were carried out using hydraulic properties fitted directly to measured retention date, as well as estimated using pedotransfer functions (Rosetta Lite and the class pedotransfer of Carsel and Parrish). RMSE and MAE indicated a favorable capacity of the model to simulate soil water content using with measured properties and a better performance than estimated properties by pedotransfer functions. For the potassium concentrations, a less than optimal performance was obtained with HYDRUS-2D using both the measured hydraulic properties and the pedotransfer functions. A better understanding and accurate determination of solute concentrations in soil, uptake parameters, the crop root growth and distribution should be necessary for improve the simulations and observed data. The inability of HYDRUS-2D to accurately estimate potassium concentrations was not necessarily a limitation of model, but rather a limitation of knowledge about the soil and plant parameters involved.

Okra Crop Response Under Subsurface Drip and Conventional Furrow Irrigation with Varying N Fertilization

ABSTRACTThere is a growing concern about excessive use of nitrogen (N) and water in agricultural system with unscientific management in Indian and developing countries of the world. Field experiments were conducted on the lateritic sandy loam soils of Kharagpur, West Bengal, India, during spring–summer (February-June) seasons for three years (2015–2017) to evaluate okra crop response under subsurface drip and conventional furrow irrigation with varying amount of nitrogen treatments. Irrigation treatments had three levels of soil water depletion from field capacity (i.e., 20%, 35%, and 50%) under subsurface drip system. There was no soil water depletion under conventional furrow irrigation system. There were four levels of nitrogen fertilizer treatments (i.e., 0, 80, 100, and 120 kg ha−1). This was supplied using urea as a nitrogenous fertilizer. The yield response of okra crop under subsurface drip was found to be 56.4% higher than that of the furrow irrigation treatment. Best yield response and maximum water use efficiency and nitrogen use efficiency were recorded under 20% soil water depletion with 100 kg ha−1 of nitrogen fertigation. Among the various soil moisture depletions, subsurface drip at 20% soil water depletion treatment responded least quantity of water lost through deep drainage and nitrogen loss beyond the root zone as compared to other irrigation treatments. The water loss through subsurface drainage was observed as 33.11 mm lesser under subsurface drip as compared to that of the furrow irrigation, and this may due to low-volume and frequent irrigation water application with subsurface drip. Hence, irrigation through subsurface drip should be used for improving water and nitrogen fertilizer use efficiency of okra crop cultivation.