James P. Bordovsky

Subsurface Drip Irrigation: Status of the Technology in 2010

Subsurface drip irrigation (SDI), although a much smaller fraction of the microirrigated land area than sur- face drip irrigation, is growing at a much faster rate and is the subject of considerable research and educational efforts in the U.S. This article discusses the growth of SDI, highlights some of the research and extension efforts, and points out some of the challenges to SDI adoption and some of the future opportunities for SDI.

Cotton Response to Pre-plant Irrigation Level and Irrigation Capacity Using Spray, LEPA, and Subsurface Drip Irrigation

Wind incidence can affect microsprinkler water distribution. Evaluations in those conditions can be facilitated using simulations by computational models. The present work evaluates the performance of a ballistic model on simulating the wind effect on microsprinkler water distribution. Experimental tests were carried out using self-compensating microsprinklers, nozzle sizes 1.00 mm (gray), 1.10 mm (brown), 1.48 mm (orange), and 1.75 mm (yellow). The gray and brown nozzles used black swivels and the orange and yellow nozzles used blue swivels. The wind effect was artificially caused by fourteen 200 W fans. The computational simulations were realized using SIRIAS software, which is based on a ballistic model originally developed for sprinkler systems. The correlation coefficients (r) varied between 0.619 and 0.880, while the exactness coefficients (d) varied between 0.842 and 0.944. Swivels internal geometry influenced the results. The tested model presented a performance classified as very good for the black swivel nozzles and a regular performance for the blue swivels nozzles.

Can Subsurface Drip Irrigation (SDI) be a Competitive Irrigation System in the Great Plains Region for Commodity Crops

Subsurface drip irrigation (SDI) as with all microirrigation systems is typically only used on crops with greater value. In the US Great Plains region, the typical irrigated crops are the cereal and oil seed crops and cotton. These crops have less economic revenue than typical microirrigated crops. This paper will present a case for how SDI can be economically competitive for the lesser value crops of the Great Plains. The case will have 5 sections: 1) How do Great Plains crops respond to SDI? 2) Are there special uses for SDI in the Great Plains? 3) How can SDI system costs be minimized without causing operational and maintenance problems? 4) Can SDI systems have a long life? 5) How does SDI compare economically to alternative irrigation systems?

A Three-Dimensional Index for Characterizing Crop Water Stress

The application of remotely sensed estimates of canopy minus air temperature (Tc-Ta) for detecting crop water stress can be limited in semi-arid regions, because of the lack of full ground cover (GC) at water-critical crop stages. Thus, soil background may restrict water stress interpretation by thermal remote sensing. For partial GC, the combination of plant canopy temperature and surrounding soil temperature in an image pixel is expressed as surface temperature (Ts). Soil brightness (SB) for an image scene varies with surface soil moisture. This study evaluates SB, GC and Ts-Ta and determines a fusion approach to assess crop water stress. The study was conducted (2007 and 2008) on a commercial scale, center pivot irrigated research site in the Texas High Plains. High-resolution aircraft-based imagery (red, near-infrared and thermal) was acquired on clear days. The GC and SB were derived using the Perpendicular Vegetation Index approach. The Ts-Ta was derived using an array of ground Ts sensors, thermal imagery and weather station air temperature. The Ts-Ta, GC and SB were fused using the hue, saturation, intensity method, respectively. Results showed that this method can be used to assess water stress in reference to the differential irrigation plots and corresponding yield without the use of additional energy balance calculation for water stress in partial GC conditions.

Comparison of Subsurface Drip Irrigation Uniformity Designs on Cotton Production

Relaxing subsurface drip irrigation (SDI) uniformity design standards for systems irrigating cotton in semi-arid environments could reduce installation costs. A SDI system was installed and cotton production experiment conducted from 2001 to 2005 to evaluate good, acceptable, and poor irrigation uniformity (FV = 7.5, 15.7, and 37.1%) at moderate and near full irrigation levels (0.6BI and 1.0BI). Flow variation treatments were established by installing drip laterals in separate zones with lateral diameters of 22, 25, and 17 mm and pressurizing corresponding laterals at 83, 45, and 69 kPa in very good (VGD), acceptable (ACC), and poor (POOR) treatment areas. Cotton yield response tended to follow changes in emitter flow rate along the length of drip laterals, but not to the extent expected. Total cotton lint yield and total yield value within a treatment area were not significantly affected by irrigation system designs with flow rate variations (FV’s) between 7.5 and 37.1 during the four test years. Average total lint yields were in a narrow range between 1442 and 1490 kg ha-1 yr-1and average yield values were between 1681 and 1749

Irrigation Interval Effects on Cotton Production Using Subsurface Drip Systems

ha-1 yr-1 among all treatments. Conditions other than SDI design, common to the Texas High Plains, impacted cotton yield variability.

CONCEPTS OF IN-CANOPY AND NEAR-CANOPY SPRINKLER IRRIGATION

Irrigation intervals as frequent as every 8 hours have been advocated by subsurface drip irrigation (SDI) service providers in an attempt to reduce severe water stress on Texas High Plains cotton where irrigation capacity is limited. Negative aspects of high-frequency, drip irrigation include non-uniform water distribution following zone valve closure and potential increases in mineral concentrations in the smaller wetted volumes adjacent to the drip lateral. A field study was conducted from 2009 to 2011 with the objective of determining cotton response to SDI application intervals of 0.25, 2 and 7days using both low and high irrigation capacities in a field with topography common to the Texas South Plains. The high irrigation capacity treatments provided approximately 80% of crop water needs using ET scheduling, while low irrigation treatment quantities were 50% of the high. The soil texture was clay-loam and the field slope was less than 1%. Over the three year period at both irrigation levels, lint yields, seasonal irrigation water use efficiencies, and loan values of the 7-d irrigation interval treatments were equal to or greater than the 0.25- and 2-d interval treatments.

Subsurface Drip Irrigation: Status of the Technology in 2010 Freddie

The use of in-canopy and near-canopy sprinkler application from mechanical move systems is prevalent in the U. S. Great Plains. These systems can reduce evaporative by nearly 15%, but introduce a much greater potential for irrigation non-uniformity. Close attention to the design, installation and operational guidelines for these systems can prevent many non-uniformity problems from becoming unmanageable.

Hydrogen Peroxide Treatment of Manganese Clogged SDI Emitters

Subsurface drip irrigation (SDI) although a much smaller fraction of the microirrigated land area than surface drip irrigation is growing at a much faster rate, and is the subject of considerable research and educational efforts in the United States. This paper will discuss the growth in SDI, highlight some of the research and extension efforts, and point out some of the challenges to SDI adoption and some of the future opportunities for SDI.

In-Season Nitrogen Status Sensing in Irrigated Cotton

Dissolved manganese in irrigation water has contributed to emitter clogging of subsurface drip irrigation (SDI) systems in the Texas High Plains. During the 2002 growing season, areas of clogged emitters occurred in a 6-ha research field at the Texas AgriLife Research and Extension Center at Halfway, Texas. Water samples from the irrigation source were analyzed and SDI emitters in the affected areas were uncovered and examined in a laboratory setting. Evaluations indicated clogging was caused primarily by manganese oxides deposited inside SDI laterals and emitters. Observations of reactions of manganese compounds with combinations of acids and hydrogen peroxide (H2O2) resulted in a protocol that dissolved these oxides in open laboratory containers. Further tests examined pressurized sections of excavated, clogged SDI laterals with H2O2 / acid solutions for periods of up to 96 hours. This exercise led to the successful field treatment that cleared clogged emitters at the research site. Continued maintenance of the research system involved the injection of 2.5 ppm H2O2 in slightly acidic irrigation water during normal irrigation. Issues with the use of these procedures include human safety, due to the caustic nature of the required materials, and high chemical cost.