Subirrigation System Research Articles

AUTOMATED CONTROL OF WATER TABLE LEVELS FOR SUBIRRIGATED TOMATO PRODUCTION USING THE FULLY ENCLOSED SEEPAGE SYSTEM

The use of the recently developed fully-enclosed seepage subirrigation system for fresh market tomato production has demonstrated an improved ability to maintain a water table at a desired level (when compared to conventional ditch-conveyed seepage subirrigation) by means of more precisely controlled application and a greater uniformity throughout the field. This is achieved through use of microirrigation tubing rather than open ditches to convey water to raise the water table to desired levels. When manually controlled, the system has shown to save 30-40% in irrigation amounts primarily due to almost total elimination of surface runoff. An automated control system was designed and evaluated with respect to practicality, durability, and performance of various designs of level-sensing switches. The advantages and limitations of the designs in relation to water table control for tomato production will be presented.

Subirrigation by Microirrigation

A fully enclosed subirrigation (FES) system was developed as an economical, water conserving method of water application for subirrigation purposes. Microirrigation (drip) tubing laterals with emitters spaced on 61 cm (24 in.) centers, and a discharge rate of 3.7 L/min/100 m @ 68 kPa (0.3 gpm/100 ft @ 10 psi) of pressure were installed on 6.5 m (21.3 ft) centers at the Gulf Coast Research and Education Center, Bradenton, Florida, during the spring of 1991. Tubes were installed at three positions: on the surface; 15 cm (6 in.) deep; and 40 cm (16 in.) deep.

Management of the Sweetpotato Whitefly and Geminivirus on Fresh Market Tomatoes in West-Central Florida, Spring, 1991

Abstract On 14 Mar, transplants were set 18 inches apart on raised beds of EauGallie fine sand covered with black polyethylene mulch. Plots consisted of three, 20-ft-long rows on 5 ft centers and were irrigated by a seepage subirrigation system. Treatments were replicated 4 times in a randomized complete block design. Treatments were applied with a high clearance, self-propelled sprayer on 20, 27 Mar, 3, 10, 17, 22 Apr, 1, 8, 13, and 29 May. The sprayer was operated at 200 psi and 3.4 mph and used hollow cone nozzles fitted with D-3 disks and #25 cores. The number of nozzles per row were increased from 4 to 8 to increase gallonage as the plants grew. Thus, 50 gal/acre were applied the first six sprays (4 nozzles), 75 gal/acre the seventh and eighth sprays (6 nozzles) and 100 gal/acre for the remaining sprays (8 nozzles). The terminal leaflet was collected from the 7th or 8th leaf (counting from the top) of each of ten stems from the middle row of each plot on 5 Jun. The numbers of eggs, crawlers, sessile nymphs, pupae, and pupa exuviae of the iweetpotato whitefly were counted. On 10 Jun the number of Liriomyza spp. leafmines were counted in a 1 minute search of each plot. All plants were examined weekly for characteristic symptoms of an unknown geminivirus transmitted by the whitefly. All fruit of marketable size were harvested on 28 May and 3 Jun and the fruit were counted and weighed.

A Pulsed Subirrigation System for Small Plots

A schematic diagram and parts list is presented for a simple and inexpensive system for pulsed subirrigation (commerically referred to as ebb and flow or flood and drain). The system can be readily modified for flowing solution culture. It has proven useful in teaching and research applications. It can be assembled from readily available parts using hand tools.

Evaluation of Insecticides for Management of the Sweetpotato Whitefly and Geminivirus on Fresh Market Tomatoes in West-Central Florida, Fall, 1990

Abstract On 5 Sep, transplants were set 18 inches apart on raised beds of EauGallie fine sand covered with black polyethylene mulch. Plots consisted of three 20-ft-long rows on 5 ft centers and were irrigated by a seepage subirrigation system. Treatments were replicated 4 times in a randomized complete block design. Treatments were applied with a high clearance, self-propelled sprayer on 14, 19, 24 Sep, 1, 8, 15, 22, 29 Oct, 5, 13, 19, 26 Nov, and 3 Dec. The sprayer was operated at 200 psi and 3.4 mph and used hollow cone nozzles fitted with D-3 disks and #25 cores. The number of nozzles per row was increased from 4 to 8 to increase gallonage as the plants grew. Thus, 50 gal/acre were applied the first five sprays (4 nozzles), 75 gal/acre the sixth and seventh sprays (6 nozzles), and 100 gal/acre for the remaining sprays (8 nozzles). The terminal leaflet was collected from the 7th or 8th leaf (counting from the top) of each of ten stems from the middle row of each plot on 25 Oct and 27 Nov. The numbers of eggs, crawlers, sessile nymphs, and pupae of the sweetpotato whitefly were counted. All plants were examined weekly for characteristic symptoms of an unidentified geminivirus transmitted by the whitefly. All fruit of marketable size were harvested on 14, 28 Nov, and 10 Dec and the fruit were counted and weighed. Samples of 50 fruit from each plot were held at room temperature in paper bags. As the fruit ripened, each was rated 1 to 4 for increasing severity of external symptoms of irregular ripening (IRR). This disorder is associated with high populations of the sweetpotato whitefly and is characterized by incomplete ripening of longitudinal sections of fruit. The percentage of unmarketable fruit was calculated (fruit rated 3 or 4 were considered unmarketable).

Monitor/Pyrethroid Combinations for Management of the Sweetpotato Whitefly on Fresh Market Tomatoes in West-Central Florida, Spring, 1990

Abstract On 20 Mar, transplants were set 18 inches apart on raised beds of EauGallie fine sand covered with black polyethylene mulch. Plots consisted of three, 20-ft-long rows on 5 ft centers and were irrigated by a seepage subirrigation system. Treatments were replicated 4 times in a randomized complete block design. Pyrethroid and Monitor/Pyrethroid treatments were alternated weekly with Thiodan 3 EC at 0.94 lb (AI)/acre. Beginning with Thiodan, treatments were applied with a high clearance, self-propelled sprayer on 20, 26 Apr, 4, 11, 16, 23, 30 May, 5 - 6, and 18 Jun. The sprayer was operated at 200 psi and 3.4 mph and used hollow cone nozzles fitted with D-3 disks and #25 cores. The number of nozzles per row were increased from 4 to 8 to increase gallonage as the plants grew. Thus, 50 gal/acre were applied the first three sprays, 75 gal/acre the fourth spray and 100 gal/acre for the remaining sprays. The terminal leaflet was collected from the 7th or 8th leaf (counting from the top) of each of ten stems from the middle row of each plot on 16 May, 11, and 27 Jun. The numbers of eggs, crawlers, sessile nymphs, and pupae of the sweetpotato whitefly were counted. All fruit of marketable size were harvested on 14 and 27 Jun and the fruit were counted and weighed. Samples of 50 fruit from each plot were held at room temperature in paper bags. As the fruit ripened, each was rated 1 to 4 for increasing severity of external symptoms of irregular ripening (IRR). This disorder is associated with high populations of the sweetpotato whitefly and is characterized by incomplete ripening of longitudinal sections of fruit. The percent of unmarketable fruit was calculated in which fruit rated 3 or 4 were considered unmarketable. Whitefly data were transformed to the square root of the number plus 0.5 prior to analyses and percentage data were transformed to arcsine of the square root of the proportion prior to analyses. All data are presented in the original scale.

Management of the Sweetpotato Whitefly on Fresh Market Tomatoes in West-Central Florida, Fall 1989

Abstract On 8 Sep, transplants were set 18 inches apart on raised beds of Eau Gallie fine sand covered with white polyethylene mulch. Plots consisted of 3-20 ft long rows on 5-ft centers and were irrigated by a seepage subirrigation system. Treatments were replicated 4 times in a randomized complete block design and were applied with a tractor-mounted sprayer on 2, 10, 16, 23, 30 Oct, 6, 13, 20, 27 Nov and 4 Dec. The gallonage was increased as the plants grew by increasing the number of nozzles/row and application pressure and by changing disks and cores. Thus, the sprayer delivered 50 gal/acre the first 3 sprays (4 nozzles/row, 130 psi, D-4 disks, #25 cores), 85 gal/acre the next 3 sprays (6 nozzles, 200 psi, D-3 disks, #25 cores), and 100 gal/acre for the remaining sprays (8 nozzles, 200 psi, D-3 disks, #23 cores). The terminal leaflet was collected from the 7th or 8th leaf (counting from the top) of each of ten stems from the middle row of each plot on 8 Nov and 7 Dec. The numbers of sessile nymphs and pupae of the sweetpotato whitefly were counted. All fruit of marketable size were harvested on 8 Dec and the fruit were counted and weighed. Samples of 50 fruit from each plot were held at room temperature in paper bags and the number of fruit exhibiting external symptoms of irregular ripening (IRR) were determined as the fruit ripened. IRR is associated with high populations of the sweetpotato whitefly and is characterized by inhibited or incomplete ripening of longitudinal sections of fruit.

COMPARISON OF LOW VOLUME DRIP AND SUBIRRIGATION SYSTEMS.

Low volume drip (2 l/h) was compared with 2 subirrigation ('trough' and `ebb and flo') systems for production of poinsettias and chrysanthemums in 15 cm diameter (1.6 l) `azalea' pots. Irrigation frequency as well as fertilizer rates were the same for all systems. The drip system received 280 ml per watering.Two plantings of poinsettias (fall) as well as two plantings of chrysanthemums (spring and summer) showed no differences in plant growth between the drip and the subirrigation systems. Water uptake by the medium was similar for all irrigation systems, but water and fertilizer application was 70% higher for the drip system. Nutrients, measured at 4 depths within the pot at monthly intervals, increased with time and was markedly more concentrated in the top layer, regardless of the irrigation system.

EFFECTS OF DRAIN ENVELOPE AND SLOPE ON PERFORMANCE OF A DRAINAGE-SUBIRRIGATION SYSTEM

ABSTRACT A field study was conducted to determine the effect of fabric wrap envelope and drain slope on the performance of a combination drainage and subirrigation system. The experiment consisted of 32, 102-mm drain tubes in four treatments of 0 and 0.2% slope with and without envelopes. Each treatment had two replications. Row rates and water table elevations were measured continuously over the four-year experiment. Data were analyzed by examining relationships between flow rate and midpoint water table elevations. An entry resistance was defined and its value calculated for 9100 observations of drain flow rate versus water table elevation midway between the drains. Results of the study showed that the effect of slope and envelope on drainage and subirrigation varied somewhat depending on field location. The fabric wrap envelope was effective in increasing subirrigation rates, but effectiveness decreased with time. Water table response to drainage was also more rapid for the envelope covered drains, in most cases, as indicated by more rapid drawdown after rainfall or subirrigation. Entry resistance was less for drains that had both envelope and slope (SE) than for any other treatment. However, resistance changed with time during the four-year experiment and head losses near the drains were high for all cases.

Cultivar and pH effects on competition for nodule sites between isolates of Rhizobium in beans

Two experiments were carried out to evaluate the effect of acidity on bean-Rhizobium competition for nodule sites. SevenPhaseolus vulgaris host cultivars differing in acid-pH tolerance were grown in sand culture, and irrigated using a sub-irrigation system and nutrient solutions of pH 4.5, 5.0, 5.5, and 6.0. A mixed inoculant of two antibiotically markedRhizobium leguminosarum bvphaseoli strains CIAT899 (acid-tolerant) and CIAT632 (acid-sensitive) was used. The acid-tolerant CIAT899 dominated CIAT632 in nodule occupancy across all cultivars and pH treatments. Although several of the varieties had previously been identified as PH-tolerant, and these cultivars performed better than those reported to be acid sensitive, all showed a marked increase in nodulation and plant development when the pH was raised from 4.5 to 6.0. The second experiment using a modified Leonard jar system varied the inoculation ratio between CIAT899 and UMR1116 (acid-sensitive, inefficient in N2-fixation) and contrasted nodulation response for the bean varieties ‘Preto 143’ (pH-tolerant) and ‘Negro Argel’ (pH-sensitive) at 3 pH treatments (4.5, 5.5, 6.5). There was a significant effect of host cultivar, ratio of inoculation, and pH on the percentage of nodule occupancy by each strain. At low pH CIAT899 had higher nodule occupancy than UM1116 in the variety ‘Negro Argel’ but had the same percentage of nodulation when the variety was ‘Preto 143’. Increasing the cell concentration of UMR1116 produced more inefficient nodules at all treatment combinations and reduced plant growth for both cultivars used.

Relating Calculated Leaf Area Index, Evapotranspiration, and Irrigation Method of Sugarcane

AbstractThe determination of the considerable amount of water used in south Florida for crop production has been time‐consuming and expensive. The Standard Class A National Weather Service pan evaporation (SPE) has been used to estimate evapotranspiration (ET), but requires crop coefficients, ET/SPE, which vary with plant development stage, season, leaf area index (LAI), yield, and irrigation method. The objective of this study was to establish relationships among ET, SPE, LAI, yield of plant and two ratoon crops of sugarcane (Saccharum spp.), and two irrigation methods. Lysimeters were used for 3 yr (1980‐1982) on a Boca fine sand (loamy, siliceous, hyperthermic Arenic Ochraqualfs). Irrigation methods were drip irrigation and subirrigation systems. Total crop seasonal ET values were 1322 mm for drip irrigation, and 1275 mm for subirrigation. The sugarcane average yield under drip irrigation (143 t/ha) was significantly higher than that under subirrigation (119 t/ha), and was linearly related to the ET. The crop coefficient is curvilinearly related to the LAI. The relationship of ET/SPE to LAI was: 0.649 + 0.185 LAI − 0.025 LAI2 (R2 = 0.77) for both irrigation methods. The relationship of ET/SPE to LAI of the second ratoon under subirrigation was: 0.599 + 0.089 LAI − 0.011 LAI2 (R2 = 0.87).

Laboratory Measurements of Head Losses From a Subirrigation Lateral

ABSTRACT Head losses were measured under controlled labora-tory conditions for a subirrigation system. It was found that contrary to previous findings there were no significant exit head losses in a subirrigation system. However, high divergent head losses were measured in the immediate vicinity of drain pipes. It appears from our study that divergent head losses might have been wrongly labelled as exit head losses in previous studies. It is probable that the clogging of drain envelopes with iron ochre or soil compaction around the drain pipe during installations with a trenchless plow might have been labelled as exit head losses. It was also found that divergent head losses were greater in a clay soil than in a sandy soil.

Rainfall probability forecasts used to manage a subdrainage-subirrigation system for watertable control

Water management of a subsurface-drainage and subirrigation system was simulated using a daily rainfall probability index ( rpi), to control the watertable depth ( wt) in the soil profile. Daily management of ‘free drainage’, controlled drainage, or subirrigation, was based upon the rpi value. The rpi was computed from the daily rainfall probability in forecasts issued by the U.S. National Weather Service. Climatic data and weather forecast records (1979–1985) for the lower Mississippi Valley were used in the DRAINMOD program to simulate daily fluctuations in the watertable. Various statistical and summation equations were used for computing the rpi. Management success was evaluated by conditions of excess and deficit soil water in the root zone, and by predicted crop yield. Using only the ‘today’ and ‘tonight’ segments of the morning (5:25 h) forecast, 75% of the significant rainfall events occurring during the growing season were successfully predicted when the rpi ≥ 0.60. Free drainage in advance of predicted storms significantly reduced the duration of excess soil water in the root zone and increased simulated maize yield 0 to 11%, when compared to controlled drainage where the water level at the drain outlet was maintained constant at a level above the drain.

Drip Irrigation and Subirrigation of Sugarcane

The difference in sugarcane evapotranspiration (ET), sugarcane yield, and soil moisture content between drip irrigation and subirrigation, are compared using four lysimeters, each 5.5‐m diameter by 1.2‐m deep. Plant cane with two ratoons are grown. The results show that the soil moisture content in the profile with the subirrigation system is much greater than with the drip irrigation system. Before canopy closure of the plant cane, ET from drip irrigation is significantly lower than from subirrigation; whereas, after canopy closure for the two ratoons, the ET from drip irrigation is significantly higher than from subirrigation. Cane yield from drip irrigation is significantly higher than from subirrigation. About 95 kg and 109 kg of water are required to produce 1 kg of cane yield for drip irrigation and subirrigation, respectively.

Weather Forecasts as a Control Input for Water Table Management in Coastal Areas

ABSTRACT FOUR water table management methods were compared in computer simulations of a controlled-drainage and subirrigation system using soils and climate conditions of the Mississippi Delta region. No significant difference in the predicted relative corn yield was obtained among the four management methods when the operation for each method was adjusted to maximize yield. However, stopping subirrigation pumping whenever the rainfall probability index (RPI) exceeded 55% reduced pumping requirements for three of the methods 12 to 21% compared to the continuous subirrigation method. The optimal management of soil-water for agricultural cropland in humid, coastal areas of the U.S. often involves complex daily control of the water table because of the erratic spatial and temporal distribution of rainfall. Periods of excess and deficit soil-water conditions are common within the same growing season. Thus, water management requires both controllable drainage and irrigation facilities. A water table management system popular in the humid region, especially in the southern coastal plains, uses a subsurface draintube system for both controlled-drainage and subirrigation. Controlled-drainage permits storage of rainfall and irrigation water in the soil profile below the depth of an overflow pipe at the drain outlet. Free'' drainage to the full depth of the drainline is often needed during periods of extended or heavy rainfall to reduce the duration of excess water in root zone. During subirrigation, the water level at the drain outlet is maintained just below the overflow pipe by pumping from an external source. A sump-type structure for controlling the water level at the drain outlet for a water table management system is illustrated in Fig. 1. The check-valve, activated by a double-float, allows fast subsurface drainage during peak flow events, functioning like the two-stage weir described by Fouss, et al. (1987b). It is often necessary to pump from a sump in level and low lying topography of the coastal plains, where subsurface drainage by gravity flow is not possible. Water table management with this type of system has a high potential for achieving maximum crop production and water use efficiency if properly controlled to compensate for changes in weather conditions. The timing of changes needed in controlled-drainage and subirrigation to manage optimally the water table depth is a major problem for farmers, especially in coastal areas with fine textured soils. In the Mississippi Delta frequent occurrences of rainfall can cause large variations in water table depth because of the small, 3 to 8%, drainable soil porosity. Results from computer simulation of four management methods for water table control are presented for soils and climate conditions of the Mississippi Delta. The primary research objective was to determine the best operational parameters that efficiently utilized rainfall during the growing season without creating periods of severe excess soil-water conditions, and which minimized the need for pumping drainage and subirrigation water. Special attention was given to the potential use of rainfall probability information from the daily weather forecast as a system control input to minimize subirrigation pumping.

Measurements of Head Losses in a Subirrigation System

ABSTRACT THE head losses were measured in a subirrigation system on a sandy loam soil in southern Quebec during the Summer of 1985. The measurements included entrance head loss from a control chamber, friction head loss in drain pipes, exit head loss from perforations in the pipe and divergence head loss in the soil around drain pipes. The head losses were found to be a function of the flowrate in the subirrigation system. For the experimental setup, total head losses were found to be about 55 cm for an average water inflow of 30 L/min in the control chamber. It was found that the exit head loss from perforations in pipes is the most significant head loss in the subirrigation system. It was 75% of the total head loss in the subirrigation system.

Applications of the Numerical Method of Lines (NMOL) in Soil Hydrology

ABSTRACT Anew technique, called the numerical method of lines (NMOL), is described. It can be used to obtain numerical solutions of initial-boundary value problems in soil hydrology in a very short time. The method is very simple and does not require a strong background in advanced mathematics or computer programming. The implementation of the method does not change from problem to problem and the method is also applicable to multi-dimensional problems. A software package that implements this technique has been developed for the IBM PC or compatible computers. The technique is illustrated by solving the initial-boundary value problems in the design of drainage and sub-irrigation systems. The nonlinear Boussinesq equation is solved numerically, subject to appropriate initial and boundary conditions. Results are compared with those of Skaggs (1975, 1979). The advantages of NMOL over other conventional numerical methods are discussed.

Uncertainty Approach to Subirrigation Design

The first and second order method of analyzing uncertainty is incorporated into the design of subirrigation systems. The uncertainty in the design due to both the unsaturated and saturated hydraulic conductivity is considered. Numerical examples are given that show how the method may enable designers of subirrigation systems to estimate confidence limits on the design drain spacing.

A Method for Estimating the Steady Upward Flux from a Water Table

ABSTRACT Aconcept utilizing the Matric Flux Potential(MFLP) is proposed for estimating the steady unsaturated flow from a water table. The method is compared with the numerical and analytical solutions to the one-dimensional, unsaturated flow equation. The MFLP model agrees very closely with the numerical and analytical solutions, as well as with laboratory measurements. It also requires less computational time. The MFLP model is, therefore, suggestd for use in soil-water models and the design of subirrigation systems

Simulated Feedback-Operation of Controlled-Drainage/ Subirrigation Systems

Simulated Feedback-Operation of Controlled-Drainage/ Subirrigation Systems