Center Pivot Irrigation System Research Articles

Optimum Center‐Pivot Irrigation System Design with Tillage Effects

A method is presented for designing the outer-end sprinkler of a center-pivot irrigation system to prevent surface runoff. The smallest wetted diameter, for which soil infiltration capacity equalled or excceeded nozzle application rate, was determined by equating a nozzle application rate relationship and a Green and Ampt infiltration rate relationship. The computed wetted diameter was used in developed relationships to select nozzle type, orifice diameter, and operating pressure. Sensitivity analysis determined that wetted diameter is primarily sensitive to soil characteristics related to infiltration and to evapo-transpiration rate. Examples illustrated variations in irrigation system design because of tillage system. Greater operating pressure of an irrigation system is necessary to prevent runoff if the tillage system does not prevent soil surface crusting or compaction by raindrops. Considering a no-till system resulted in the selection of a low-pressure impact sprinkler instead of a conventional high- or medium-pressure impact sprinkler. Therefore, the developed methodology can be used to design the optimum center pivot irrigation system for given soil, climate, cropping pattern, and tillage practices.

Center-Pivot Irrigation Position Alarm System

A position alarm system was designed, developed, and evaluated for use on a single tower, center-pivot irrigation system. The alarm system signals the operator when the pivot boom reaches an established position. The position of the pivot boom and tower can be determined within 0.62° when the direction of rotation is reversed (clockwise and counter-clockwise travel) and within 0.03° when rotating in the same direction. With modification, this low-cost system may be used to automate a center-pivot system to stop, change direction or velocity, or perform other functions at preset positions.

Performance of Chemigation Backflow Prevention Assemblies

When chemicals are applied using irrigation systems, there is potential for contamination of the water source by backflow if the irrigation system shuts off while unattended. This study was conducted to determine the operating and performance characteristics of new, i.e., unused, chemigation backflow prevention assemblies (CBPAs). Four manufacturer’s models were tested in the laboratory. However, two of CBPAs have been modified since the testing was completed. In general, the CBPAs do not meet the standards established for municipal water suppliers and many industries. The backpressures required for the two current models to seal were 0.0 and 6.7 kPa (1.0 psi). Backflow was a function of backpressure for the three check valves that did not seal at zero backpressure. All four valves exhibited a backpressure backflow relationship when artificially fouled with hexagonal bars placed across the valves seat. At the backpressure head of 3.7 m (12 ft), the low pressure drains on all models intercepted 100% of the backflow (leakage) when the check valves were fouled with 0.12 cm (3/64 in.) bars placed across the valves seats. A typical backpressure head after shutoff of a center pivot irrigation system is 3.7 m (12 ft). These findings support the results of field tests of eight used valves where the low pressure drains intercepted 100% of the backflow at all backpressure heads evaluated [3.7 m and less (12 ft)].

A Farm Management Analysis of Supplemental Center-Pivot Irrigation in Humid Regions

Many farmers in humid areas are turning to supplemental irrigation as a means of hedging the risk of crop failure. While center-pivot irrigation systems provide more even water coverage than many other systems, they can be difficult to position on irregularly shaped fields that are common in many areas of the Eastern USA. In order to analyze the farmer's decision regarding the use of center-pivot systems, a risk programming model was developed using a grid system for optimal center pivot positioning. Due to the complexity of commodity programs, financing, risk, and field characteristics, partial budgeting techniques may not be capable of providing the insights into the interaction of farm management considerations that are generated by the model. The financial problems that have existed in the U.S. agricultural sector during the 1980s have slowed the growth of supplemental irrigation acreage. The inverse relationship between production and financial risks associated with supplemental irrigation is demonstrated by model results. In a case study in southern Alabama, irrigation could increase net farm income by as much as 100% over not irrigating by improving average yields and allowing some doublecropping. Irrigation could also decrease income variability as much as 32% by reducing yield variability. It is worth the investment provided a source of financing is available. The ability to benefit from irrigation use is often dependent on financial constraints. Irrigation may not be advisable or feasible depending on the farmer's debt load or debt limit. There is a clear tradeoff between production and financial risk that must be judged by the individual producer. Public sector initiatives to foster the expansion of supplemental irrigation should consider financial programs that extend the payoff period, thereby decreasing the debt burden in the initial years of the investment.

Influence of Chemigation Parameters on Fall Armyworm Control in Field Corn

The application of pesticides in irrigation water (chemigation) is developing into a highly efficient and economical pest management strategy as the influence of application parameters are understood. In the current study, the effects of main-line water velocity, injection port direction, and sprinkler nozzle type were evaluated with two rates of chlorpyrifos to control fall armyworm larvae, Spodoptera frugiperda (J. E. Smith), in whorl-stage field corn grown under 0.6 ha center pivot irrigation systems. Chlorpyrifos injected into a main-line water velocity of 2.7 m/s generally gave as good or better fall armyworm control than when injected into a water velocity of 0.9 m/s regardless of sprinkler type. Upstream injection of chlorpyrifos formulated in non-emulsifiable oil resulted in better control of fall armyworm than did downstream injection. Chlorpyrifos applied with a 360@* spray sprinkler with coarse plates and nozzle orifice diam. between 3.6 and 9.5 mm at a main-line water velocity of 0.9 m/s gave the poorest fall armyworm control while an impact sprinkler gave the best control. The formulation droplet breakup in the main line and at the sprinkler were important factors in the distribution of insecticides to the target.

METHODOLOGY FOR RISK ANALYSIS OF CHEMIGATION

ABSTRACT A method was developed for analyzing the risks of direct contamination of a water source when chemicals are applied with center pivot irrigation systems. To demonstrate the utility of the model, data were collected to estimate equipment failure parameters and the hydraulic characteristics of chemigation safety equipment.

Evaluation of Granular Insecticides for Control of Lesser Cornstalk Borer in Irrigated and Unirrigated Tropical Corn, and in Two Levels of Soil Ph in Peanuts, 1990

Abstract Granular treatments were applied to conventionally tilled and planted fields of tropical corn and peanuts in sandy loam soil at the Wiregrass Experiment Substation at Headland, Ala. Four replicates of 3 treatments and an untreated control were planted in a randomized complete block design for tropical corn, and 4 replicates of 4 treatments and an untreated control were planted in a randomized complete block design for peanuts. Treatments were applied to fields with a single-row, small-plot, granular applicator in a 7-inch band over the row. A liquid methyl parathion treatment was applied to the foliage in peanuts weekly for 4 consecutive wk using a boom sprayer with 1 hollow cone nozzle per row at 40 psi and delivering 8 gal/acre. Tropical corn plots were 12 rows wide (36-inch row spacing) × 60 ft long, and treatments were applied to both fields at emergence (13 Jun). One field was irrigated on 2 Jun (pre-planting) and at 15 and 47 DAT with a center pivot irrigation system. The other field was not irrigated. Granular treatments were applied to peanuts at flowering (27 Jun) on the two fields with differing pH. Plots were 6 rows wide (36-inch row spacing) and 50 ft long. A soil sample was taken at 0, 6, 13, 20, 34 and 50 DAT from tropical corn plots and at 0, 6, 13, 28 and 43 DAT in peanuts. Each soil sample (12-inch wide × 4-inch long × 1-inch deep) consisted of 3 subsamples from within each plot, and sampled areas were flagged to prevent resampling. Soil samples were returned to the laboratory and refrigerated until processed. Soil from each treatment was air dried to <1.0% moisture and placed in 1-oz plastic cups to a depth of 0.5 inch. Larvae were placed in cups and artificial insect diet was provided as a food source. Efficacy of pesticides was evaluated by exposing 27 first-instar lesser cornstalk borer larvae (3 replicates times 3 cups per replicate times 3 larvae per cup) to each treatment. At the end of 72 h exposure, living and dead insects were counted.

Populations of Fungi in Soil After Chemigation with Chlorothalonil and Tebuconazole via Center-Pivot Irrigation

Chlorothalonil and tebuconazole were applied to peanut (Arachis hypogaea) through a centerpivot irrigation system (chemigation), a pivot-mounted underslung boom, or ground sprays. Populations of Rhizoctonia solani AG-4, R. zeae, and Sclerotium rolfsii in soil at midseason and at digging were variable and were not influenced significantly by chemical treatment or application method. Chemigation with tebuconazole, but not with chlorothalonil, reduced populations of total fungi in soil at digging, and in one test all applications of tebuconazole reduced populations of binucleate Rhizoctonia CAG-3

Residual Efficacy of Chlorpyrifos 4E Applied through a Center-Pivot Irrigation System on European Corn Borer (Lepidoptera: Pyralidae) Larvae

Applications of chlorpyrifos 4E through an overhead center pivot at 1.12 kg (AI)/ha with and without oil (Sunoco UN) in water volumes of approximately 0.83 cm (1984-1985), 2.03 cm (1984), and 4.82 cm (1985) were compared in bioassays using first instar European corn borer, Ostrtnta nubtlalts (Hiibner). Mortality data were obtained from 24 h bioassays done at four 72-h intervals following insecticide application. During both years, neither irrigation rate nor the addition of oil had a significant effect on efficacy or residual activity of chlorpyrifos when averaged over oil versus nonoil treatments and all irrigation rates respectively. Although not statistically significant, applications with 0.83 cm water without oil resulted in highest mortality, and applications with 2.03 cm (1984) and 4.82 cm (1985) of water with oil resulted in the lowest mortality when averaged over all time periods. Quadratic (1984) and linear (1985) responses over time were observed with all four treatments. Average mortality was 33.9 and 19.9% 12 d after application in 1984 and 1985, respectively.

Effects of Tractor Traffic and Chlorothalonil Applied via Ground Sprays or Center Pivot Irrigation Systems on Peanut Diseases and Pod Yields

Chlorothalonil (as Bravo 720) was applied at 1255 g/ha 7 times to groundnut cv. Florunner in 0.12, 17.8 or 1.7 kl of water/ha via ground sprays, centre pivot irrigation (chemigation) or pivot-mounted underslung boom, respectively. Some of the chemigated plots were subjected to tractor traffic. Rhizoctonia limb rot (caused by R. solani anastomosis group 4) was generally not controlled by chlorothalonil and tended to be more severe with tractor traffic. Plants in untreated plots had final defoliation of 96 and 68% because of late leaf spot (caused by Cercosporidium personatum [Mycosphaerella berkeleyi]) in 1987 and 1988, respectively. Ground sprays gave the best leaf spot control in both years, followed by the underslung boom and chemigation applications. In 1987, yields were significantly lower in plots that received the underslung boom or chemigation treatments than in ground-sprayed plots. With less disease in 1988, pod yields were equal in chemigated and ground-sprayed plots and were significantly higher in plots treated by means of the underslung boom.

Efficacy of Insecticides Applied to Twospotted Spider Mites on Field Corn in West Central Nebraska, 1987

Abstract Cygon 400, Capture 2 EC, and Comite were aerially applied in one trial 16 Aug to dough-stage field corn. Capture 2 EC was applied through a center pivot irrigation system; Counter 15 G and Parathion 8 EC were aerially applied 19 Aug to field corn in a second trial. Plots to be aerially applied were 120 ft wide by field length. Chemigation treatments were applied to 8 acre triangular-shaped plots. All treatments were replicated twice in a randomized complete block design. Sizes of naturally-occurring twospotted spider mite colonies were rated on the under surface of 7 leaves starting with 3 leaves below the ear through 3 leaves above the ear. Ratings were made with a 0-6 scale where 0 equaled no mites on the leaf, 1 equaled individual mites present, 2 equaled well-formed colonies ... up to 6 where mite colonies were so large that the under side of the leaf was completely covered and the leaf had died due to mite feeding. Mites were evaluated on 4 plants located about 250 ft from the edge and in the center of each plot. Evaluations were made 1 d prior to application, 12 and 21 d post-application in the first trial; 7 and 14 d post-application in the second trial.

Sprinkler Irrigation Runoff and Erosion Control Using Interrow Tillage Techniques

A continuous-application rainfall simulator was used to apply water at rates similar to the peak rates of center pivot irrigation systems equipped with low pressure spray sprinkler packages. Three interrow tillage treatments implanted reservoir, basin till, and subsoilerwere compared to conventional tillage for two field slope conditions (1% and 10%). Tillage that provided increased levels of surface storage provided the most effective means of controlling both runoff and soil erosion. At 10% field slope, the implanted reservoir reduced runoff by 68% and soil erosion by 92% compared to the conventional treatment. There was significantly greater soil erosion on the subsoiler treatment than on the basin till, implanted reservoir, or conventional treatments for 10% field slope conditions. However, at 1% field slopes, the subsoiler treatment was comparable to the implanted reservoir with respect to amount of water runoff and soil erosion. At 10% field slopes, the conventional treatment resulted in greater erosion than the implanted reservoir and basin till treatments. However, at 1% field slopes, no difference in runoff volume was measured.

Control of European Corn Borer on Field Corn in West Central Nebraska, 1987

Abstract Dipel ES and Lorsban 4 E were applied 1 Jul through a center pivot irrigation system to whorl stage field corn. Treatments were applied in a 0.5 inch irrigation in 2 replications arranged in a randomized complete block design. Ten plants from each plot were split from stalk to tassel in search of European corn borer larvae and/or cavities on 23 Jul. Pretreatment European corn borer infestation levels were moderate with an average of 52% of the plants with larvae and an average of 0.62 larvae/ infested plant. The purpose of this trial was to evaluate different rates and formulations of Dipel ES when applied by chemigation to control European corn borer larvae.

Calculation of Chemical Flushing Times in Center Pivot Irrigation Systems

ABSTRACT The injection of chemicals into irrigation systems, or chemigation, is fast becoming commonplace. Threadgill (1985) estimated that 4.2 million hectares in the United States were chemigated in 1983 and that the chemigated area was increasing 8-9% per year. More than 84% of the total chemigated area was chemigated with sprinkler irrigation systems and most of these were center pivots. Concern has been raised about the safety aspects of mixing chemicals with irrigation water. Management practices for chemigation safety have been presented by Hay and Eisenhauer (1985). One of the management practices recommended was to operate the irrigation pump for at least 10 min to flush chemicals from the irrigation system. Mathematical methods for estimating the time required to flush chemical solutions from center pivot irrigation systems are presented in this paper. Piston flow is assumed and movement of the chemical in other ways, such as by dispersion, is not considered.

Electronic Percentage Timer for Center Pivot Irrigation Systems

An electronic percentage timer was developed for center pivot irrigation systems. The timer provides greater timing accuracy than electro-mechanical timers presently used to vary the water and chemical application amounts to a given field.

Center-Pivot Applications of Chlorpyrifos 4E for Reducing Ear and Stalk Infestations of Second-Generation European Corn Borer Larvae (Lepidoptera: Pyralidae) in Field Corn

Applications of chlorpyrifos 4 emulsifiable concentrate (EC) at 0.56 and 1.12 kg (AI)/ha applied through a center-pivot irrigation system resulted in significantly fewer second-generation European corn borer (ECB), Ostrinia nubilalis (Hubner), larvae (and consequently a significantly higher grain yield) than the untreated control. Larval reduction was less in the ear than in the stalk. Addition of a nonemulsifiable oil (Sunoco 11N) (1.06 liters) in 1983 had no significant effect on control. In 1984, two applications of chlorpyrifos 4EC at 0.56 kg (AI)/ha applied at 6-d intervals resulted in significantly fewer ECB per plant than a single application at 1.12 kg (AI)/ha. However, yields did not differ significantly.

Chemigation of Peach Trees with a Center Pivot

Abstract Pesticides were applied to ‘Rio Grande’ peach [Prunus persica (L.) Batsch] trees at recommended rates from bloom to harvest using three sprinkler configurations on a center pivot and an air-blast sprayer. Fruit scab infection rates with a patented sprinkler configuration (Piggy-back) that has spray nozzles mounted on a lower truss rod of the center pivot were equivalent on 12 and 23 June 1987 to those with the air-blast sprayer. Scab infection rates for standard impact-nozzles and for a deflector nozzle configuration were equivalent to each other, and tended to be lower than the infection rate for the unsprayed fruit, but higher than the rate for the air-blast sprayer or piggy-back configuration. Brown rot, bacterial spot, and insect catfacing (the other fruit defects observed at harvest) were independent of the method of pesticide application. It may be feasible to chemigate peach orchards with center-pivot irrigation systems.

Soybean Yield and Yield Component Response to Limited Capacity Sprinkler Irrigation Systems

The rapid increase in soybean [Glycine max (L.) Merr.] production under sprinkler irrigation systems in the semi-arid Great Plains necessitates more research on minimum-capacity center pivot irrigation systems. A three-year field study was conducted to evaluate yield and yield component responses to sprinkler irrigation scheduling strategies. Irrigation treatments (main plots) were nonirrigated (NI), irrigation commencing at R2 (FL), irrigation commencing at R3–R4 (POD), and irrigation scheduling based on 50% available soil moisture depletion (SCH). A solid-set sprinkler irrigation system was used to simulate a minimum-capacity center pivot system for central Nebraska on silt loam soils (1.5 in. water/wk). Water applied was greatest for SCH, intermediate for FL, and least for POD. Row widths of 30 and 10 in., were subplots, and three cultivars were evaluated as sub-subplots. In two low rainfall years, POD yielded 5 bu/acre less than FL and SCH. In a year with adequate rainfall, POD yielded 3 bu/acre more than FL and SCH due to greater lodging of two cultivars in FL and SCH. Irrigation treatments had no major effect on soybean responses to row widths. Irrigated soybeans had 16% less flower and pod abscission than nonirrigated. With a minimum-capacity irrigation system and the concomitant differences in water application of our irrigation treatments, delaying irrigation until R3–R4 in low-rainfall years will likely result in reduced yields relative to irrigation commencing at R2 or irrigation timed according to a soil moisture based irrigation scheduling system.

Friction Correction Factor For Center‐Pivot Irrigation Systems

A friction correction factor (Fcp) for use in the estimation of friction loss in a center-pivot irrigation system lateral is derived. The results obtained using the Fcp are compared with the result...

First-Generation European Corn Borer Control with Ground, Aerial, and Center Pivot Applications, 1987

Abstract Insecticide trials were established at 3 locations in South Dakota. The experimental design for 2 ground trials was a randomized complete block with 4 replications at Redfield and 3 replications at Beresford. Individual plots were single-row treatments 30 m long for the ground trials. A center pivot trial was conducted at Redfield and an aerial study was established at Armour. Ten plants with shot-hole injury midrib feeding, or both, were evaluated per replicate from each treatment for the ground trial locations. Damage was measured on the basis of one cavity equaling 2.5 cm of tunneling. Four sites were chosen randomly from within the aerial and center pivot treatments, and 10 plants/site were evaluated for damage. Experimental and registered products were tested at Redfield and Beresford. Pioneer 3475 was planted at a seeding rate of 60,540 seeds/ha on 22 Apr at Beresford. Granular materials were applied with a pneumatic applicator powered by a 3.5-horsepower engine mounted on a high-clearance ground applicator. Insecticide was metered by Noble metering units that were chain driven by a 12 V DC motor. Insecticide was banded (20 cm) over the whorl. Liquid insecticides were applied with a backpack sprayer. One 1.5 LE Even Flat Nozzle/row, pressurized at 15 psi was used to apply 19.5 gal/acre at 3.5 mph. All insecticides were applied at Beresford on 26 Jun. Stalks were split on 3 Aug and damage measured. Pioneer 3737 was planted at a seeding rate of 63,500/ha on 1 May at Redfield. Insecticides were applied on 29 Jun at Redfield. Plants were evaluated for injury on 4 Aug. Pioneer 3901 was planted at a seeding rate of 73,388/ha on 1 May at the center pivot trial in Redfield. Insecticides were injected with a Northern chemigation unit into a Valley electric drive center pivot irrigation system from 26 to 27 Jun. Plants were evaluated for damage on 4 Aug. Two irrigation rates of 0.53 and 2.5 cm water/day were used. The aerial trial was conducted at Armour. Dekalb 1100 was planted on 28 Apr at a rate of 63,010 seeds/ha. Insecticides were applied on 26 Jun with a fixed-wing aircraft in single swath treatments 13.7 × 402 m long. Stalks were split on 3 Aug and damage assessed.