There is a strong connection between chemigation, fertigation and irrigation, the goal being for each plant to receive a uniform quantity of water and additive. Uniformity of application is indeed the essential factor in successful fertigation and chemigation.

Uniformity depends on several factors such as the homogeneity of water application, adjustment and use of injection equipment, compatibility between additives and application conditions, especially where wind conditions are concerned.

Pivots and linear move systems are the best sprinkler application systems, given their high potential uniformity of water distribution over large areas. Small amounts can be applied, even during rainy periods or at night under windy conditions.

Chemigation is the application of an approved chemical (fertilizer, herbicide, insecticide, fungicide or nematicide) with the irrigation water applied by the center pivot. Pesticides and other chemical must be labelled to state whether the product is approved for application in this way. Using proper chemigation safety equipment and procedures also helps the grower by providing consistent, precise and continuous chemical injection, thus reducing the amounts (and costs) of chemical applied.

Advantages of chemigation

- Uniformity of application. With a properly designed irrigation system, both water and chemicals can be applied uniformly, resulting in excellent distribution of the water-chemical mixture.

- Precise application. Chemicals can be applied where they are needed and in the correct concentrations.

- Economics. Chemigation is usually less expensive than other application methods, and often requires smaller amounts of chemicals.

- Timeliness. Chemigation can be carried out when other methods of application might be prevented by wet soil, excessive wind, lack of equipment, and other factors.

- Operator safety the operator is not in the field continuously during applications, so there is less human contact with chemical drift, and less exposure during frequent tank fillings and other tasks.

Disadvantages of chemigation

- Skill and knowledge required. Chemicals must always be applied correctly and safely. Chemigation requires skill in calibration, knowledge of the irrigation and chemigation equipment, and an understanding of the chemical and irrigation scheduling concepts.

- Additional equipment. Proper injection and safety devices are essential and the grower must be in compliance with these legal requirements.

Advantages of fertigation

Nutrients can be applied any time during the growing season according to the crop’s needs. Nutrients can be applied uniformly over the field if the irrigation system distributes water unifromly.

Groundwater contamination is less likely with fertigation because less fertilizer is applied at any given time and the application can correspond to the peak crop requirements.

Disadvantages of fertigation

Fertilizer distribution is only as uniform as the irrigation water distribution. Use pressure gauges to ensure that the center pivot is properly pressured.

Lower cost fertilizer materials such as anhydrous ammonia often cannot be used.

Fertilizer placement cannot be localized, as in banding.

Many fertilizer solutions are corrosive. Chemigation injection pumps and fittings constructed of cast iron, aluminum, stainless and some forms of plastic are less subject to corrosion and failure.

Irrigation efficiency involves the ability to minimize water losses. Such factors as loss of water from wind drift and evaporation from the soil surface and plant affect the level of efficiency. Meanwhile, another factor of irrigation efficiency is simply getting water into the soil, and controlling runoff. For mechanized irrigation, the biggest single advancement towards increasing irrigation efficiency has been mounting the sprinkler down out of the wind on drop tubes. Enabling the success of drop tubes are products that spread the water out over a wide area, even when mounted below the truss rods of a center pivot. These rotating, spinning and wobbling devices operating at low pressure have dual benefits, increased soak time and low application rates. A more complete throw pattern can give twice the soak time of fixed sprayheads.

Without sprinkler performance that can apply water at an application rate less than the infiltration rate of the soil, the efficiency gained is soon lost to runoff. Average application rate (AAR) is the rate of water application over the wetted area. It is an average value assuming uniformity within the wetted area. Pivot average application rates increase with the higher flow demands required at the outer portion of a center Pivot. By increasing the wetted throw distance of the sprinkler, AAR can be reduced to match the soil’s infiltration rate.

Instantaneous application rate (IAR) is also an important element of sprinkler performance especially for silt type soils that are prone to compaction. Instantaneous application rate (IAR) is the peak intensity of water application at a point. IAR and droplet kinetic energy are important variables in maintaining good soil intake rate throughout the season. Pivot sprinklers that produce high instantaneous application rates with high velocity, large droplets are detrimental to some soils types causing surgace damage by sealing off the soil pore space at the surface. The rate of instantaneous application for a fixed stream type sprinklers can be more than ten times the average if measured at the instant the stream hits the soil. The problem comes when some surface damage occurs, sealing off the soil pore space at the surface. The best condition for infiltration is to keep the soil surface open, and apply water using a wide applicaiton width.

Another sprinkler technological advancement is the use of dual nozzle clips. This allows two system flow rates to be used on the same machine, allowing use of lower flow rates to march Crop ET (Evapotranspiration) rates during germination, when water requirements are low.

Innovations like the 3TN Dual Nozzle clip allow irrigators to reduce Average Application Rates during germination or the early stages of a crop’s growth curve. The 3TN Dual Nozzle Clip holds a secondary nozzle, allowing quick and accurate changes of system flow rate. Lowering average application rates reduces ponding of water and potential erosion, while maintaining the integrity of the soil structure with less intense water droplets.

In an area of suplemental irrigation, like the delta region of west central Mississippi, pivots are at their best when asked to perform in a variety of summer weather conditions. The summer of 2000 provided just such an opportunity. “We saw a renewed interest in center pivot irrigation after that summer. It was hot, dry and windy from early spring until late summer,” repor Mark and Don Barger of Big D. Inc., Greenwood, Mississippi.

“The 2000 crop year was unique. Many farmers with center pivots on tight, heavy soils experienced greater yield increases than normal an greater increases than those on lighter soils using various methods of irrigation,” Don Barger explains. “Mechanized irrigation saved several cotton crops from disaster, and, in some cases, paid for the initial investment in just one season.”

During the peak of the growing season, cotton needs 2 ” to 3 ” of water each week. When rain is scarce, precise timely irrigation is essential for top yields. Irrigate too late and the crop will mature later than it should, causing problems down the road like boll rot. On average, center pivot irrigation will increase yearly cotton yields 200-300 lb./acre over dryland cotton, the Barger brothers report. This expected yield increase is often the result of maintaining good soil moisture after planting and throughout the growing season.

Increased yields also depend on center pivot reliability and a well trained and well equipped irrigation dealer. “The one thing cotton farmers don’t want is an expensive bird rest. They want a reliable center pivot and the assurance that the irrigation dealership can quickly handle any concerns.” says Don Barger. Cotton is the main crop in the Mississippi Delta, but corn, soybeans and wheat also benefit from the timely application of irrigation water. That’s because pivots can deliver irrigation water quickly and in small amounts in the spring to get crops up out of the ground and to assist with the activation of pre- and post-emergent herbicides, something flood irrigation simply can’t do. Plus, some fields with hilly, rolling ground are simply better suited to center pivots. Growers aren’t faced with the expense of land leveling required with gravity flow irrigation, either.

Mississippi growers put center pivots on dryland fields or convert flood irrigated fields to mechanized irrigation to reduce labor and to make the irrigation process easier to manage. And those may not even be the most important reasons for irrigating with center pivots. “The greatest advantage of pivot irrigation is the ability to get water to the crop quickly, when it will do the most good,” Mark explains.

“Pivots also allow growers to shut off that water quickly when rains come. That way they avoid getting too much water in the field at one time, which is always possible with gravity irrigation. You need to limit irrigation amounts in the early season. Later, when the crop is established, the crop canopy is larger and plant’s moisture needs are greater, more water can be applied. “

Cotton irrigation starts in the early spring with as little as 0.5″ of water applied soon after planting. This helps to encourage seed germination and to establish a uniform stand. Two and sometimes three applications of 0.5″ of water also helps activate crop chemicals.

A wet year like 2002 is a once in a decade event with 1982 and 1991 the only other two in recent memory.  Spring and summer growing conditions were ideal, with rain coming at just the right times.

The center pivot has opened up thousands of acres to irrigated, agronomic crops and increased production o thousands more. Farms that could not use surface methods because of topography and could not economically justify portable, side-roll or solid set sprinklers had no alternative to dry land agriculture until the advent of the center pivot.

The pivot solved the problems of topography, economics, labor and deficient water supplies. Pivots are in use in nearly every country in the world on nearly every crop and the contribution of the pivot to the world’s agriculture cannot be overestimated.

Circular motion key to success

However,there are some situations in irrigated agriculture where the pivot will never work. The circular motion of the pivot is the key to much of its success. It is the most efficient path through the field because the machine is continually moving into the driest area. Additionally, the pivot point makes both the alignment and water supply fairly simple.

Unfortunately the circular path also produces the physical and biological limitations on the use of the center pivot. The end of the traveling pipeline must move completely around the perimeter of the field during each circuit, and, as the system moves, it must apply sufficient water to satisfy the needs of the crop until the system returns.

The fast moving end of the pivot must apply water at a very heavy rate to deliver enough water to the crop as it speeds past. The soil must have an infiltration rate enough to accept the water at the rate applied or the water will run off the field.

The critical factors in this situation are the Et, the daily water requirement of the crop that the pivot must supply and the IR, the infiltration rate of the soil. These factors must be in balance for the system to operate succesfully. If the Et and IR do not match, the pivot will either have to apply water too fast for the soil to absorb or, if the application rate is equal to the IR, the system will not be keeping up with the needs of the crop. Problems with center pivots begin to be seen in hot, arid climates with high pH, desert type soils. The hot, dry weather produces a high Et and consequently a high application requirement from the pivot. The desert soils are often characterized by low infiltration rates which compound the problem.

There is nothing wrong with the concept of the center pivot even in arid climates and soils. It is only the size of the system that is limited. At some point along the length of any properly designed pivot the machine will be applying exactly the amount required by the crop at exactly the rate that the soil will accept it. This is the maximum length the pivot can be under those conditions. If it is longer than this maximum, the sprinkler heads from this point out will be applying water too rapidly for the soil to absorb it.

The maximum length and therefore the area covered by the pivot are determined by the biological limit of the crop’s Et and the physical limitation of the intake rate of the soil. High Et’s and low IR’s require small systems to avoid runoff or water stress. In many arid situations, the maximum size is too small to be economically feasible.

Conditions in the mid-west can allow 1,320-ft. pivots plus corner systems to cover nearly all of a quarter section. In the humid south, pivots can be over a half mile in length and cover in excess of 500 acres. In the Central Valley of California, Arizona or parts of Saudi Arabia, the maximum length for some crops may be less than 125 ft., covering only one acre, hardly a practical system.

]]> http://www.traxcoirrigation.com/sprinkler-system-choices/feed 0 http://www.traxcoirrigation.com/maximum-length-area-of-a-center-pivot http://www.traxcoirrigation.com/maximum-length-area-of-a-center-pivot#comments Wed, 11 Jul 2012 08:05:12 +0000 Traxco http://www.traxcoirrigation.com/?p=2515 It is possible to determine the maximum length and area of a center Pivot for a certain set of conditions or to find out if an existing pivot can be used for a certain crop.

It is possible to determine the maximum length and area of a center Pivot for a certain set of conditions or, for planning purposes, to find out if an existing pivot can be used for a certain crop.

Crop requirement

Three pieces of information are necessary for the formulas in order to make the calculations. The crop requirement can be obtained from a local consultant, extension agent or university. Use the maximum value for the season which generally occurs when the crop has reached its full size and is just beginning to mature. The number will be expressed in millimeters per day.

Infiltration rate and pattern diameter of the sprinklers

Along with the crop requirement, the infiltration rate of the soil and the pattern diameter of the sprinklers on the pivot are needed. The sprinkler diameter can come from the manufacturer’s catalog or it can be measured in the field. If a field measurement is used, be sure the nozzle size and pressure are the same as the situation for which the calculation is being made.

Soil infiltration rate estimation

The infiltration rate of the soil is probably the most difficult to measure and the least accurate of the three values needed for the formula. The infiltration rate of the soil is not the same for all parts of the field nor is it even the same at one point all of the time.
It’s usually measured as the depth of water in inches that will penetrate the soil surface in an hour. The rate is high when the soil is dry and decreases as the soil wets until it reaches a constant rate. This constant is the number to be used in the calculation.

The infiltration rate can be estimated if the soil texture is known and there are none of the sodium soil problems that are often found in arid climates. The infiltration rate can be measured a number of ways. A piece of pipe at least six inches in diameter and about a foot long can be driven vertically into the ground carefully to avoid disturbing the soil surface. The end of the pipe should be at least three inches below the surface.
Fill the pipe with a few inches of water and keep the water level fairly constant for about eight hours. After the infiltration rate has reached its steady state, record the difference in water level in the pipe over a period of exactly one hour and that will be the rate to use in the center Pivot calculation. The accuracy of this procedure will be increased considerably if the pipe is placed inside a basin three feet in diameter that is also kept full of water.

A second method to estimate soil infiltration rate is to use a sprinkler, perhaps even the pivot itself if it is already in the field. Operate the sprinkler for several hours if the soil is initially dry and then find an area under the sprinkler pattern where there is water ponding due to excessive application rate. The application rate at the edge of this ponded area should be very nearly equal to the infiltration rate of the soil. Place a number of rain gauges at these edges and measure the amount of water applied in one hour which will be equal to the soil infiltration rate.

Maximum Pivot length and acres covered

Length = [3.82 x infiltration rate (in/hr) x pattern diameter (ft)] / Crop requirement (in/day)

Acres covered = Length (ft) x Legth (ft) / 13,866

The minimum field size that can economically accommodate a pivot is about 40 acres. The center pivot is one of the most successful methods of irrigation in modern agriculture. Like the other varieties of sprinkler irrigation, the pivot must be properly designed to accommodate the conditions under which it will be operated.

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To check system for presence of hazardous voltage: use voltmeter with selector switch at 600 volts (AC). Touch one probe to metal of system and other probe into the soil. Repeat test at 120 VAC.

If voltmeter shows any voltage, do not touch the system. Check main power source disconnect using voltmeter before placing your hand on the disconnect handle. If disconnect handle is safe, turn off disconnect and call for professional assistance. Lock the handle, if possible, in the ‘Off’ position to prevent someone else from turning the disconnect or system on while waiting for a qualified service-man.

If no meter is available for checking a system to see if it is ‘hot’ a possible alternative would be to quickly and lightly tap the back of your hand against a Pivot or tower leg. Physical contact in this manner with a ‘hot’ system will be felt as a ‘rippling tingle’ or ‘jolt’ but should not cause serious injury.

A ‘hot’ machine is generally not suspected until someone else has received a shock from it. A good practice to get into is to ‘back hand’ irrigation equipment everytime before you grasp onto it.

What is a ground fault?

Insulation breakdown or leak from current carrying conductors to metal, such as motors, collector rings, switches, solenoids, relays, also loose connections, etc.

An equipment ground is a low resistance continuous conductor bonded to all metal boxes, through the total system with a driven ground electrode and approved clamps at the Pivot box, pump panel, and back to the power source where it is again grounded at the transformer or generator power source.

The maximum resistance of a ground electrode (rod) shall not exceed 25 ohms. Under some sandy soil conditions, it may be impossible to have a resistance as low as 25 ohms. In that case, use another electrode (rod) at least six feet from the first rod and securely bond the two rods together with copper wire og #6 gauge or larger, never smaller.

The lower the resistance of the ground installations, the better chance you have of clearing a ground fault on the machine.

Minimum size of ground rods shall be 1/2″ x 8″, either copper clad or galvanized. Galvanized pipe is acceptable as a ground rod, but must be minimum 3/4″ inside diameter and must have approved ground rod clamp. When driving ground rods, if rocks are found above 4′ below the ground, a trench must be dug the full length of the rod and rod buried in a horizontal position just above the rocks.

A good method to check a machine for ground fault when machine is energized is to clamp a good “Tong Type” ammeter around the ground wire to see if there is any current flow to the ground. If any reading is observed, no matter how small, avoid contact with any metal parts until the supply circuit is opened.

Grounding of generators

Generator installations must be in accordance with the latest edition of the National Electric Cose. A fusable disconnect with the proper size fuses must be installed at the output of the generator to protect the generator from burning out if a short or ground fault should develop in the underground wire.

Proper wire size from the generator to the system should again be emphasized. There must be a properly sized ground wire from the generator to the system. Also, a ground rod must be installed at the generator unit.

Grounding of power supply

Grounding of any electrically driven irrigation system is mandatory. Proper grounding accomplishes a number of things:

• Protection of personnel from electrical shock
• Protection of equipment
• Confines voltages
• Provides a positive means of discharging the equipment

Equipment that is not grounded properly presents a dangerous hazard to life and equipment. In the design and installation of electrically driven pumps, irrigation systems and other ancillary electrically driven hardware, grounding considerations are critical.

All irrigation installations must meet the current National Electrical Code for electrically powered irrigation systems. Some of the items to be considered in design on installation of the system are listed below.

Properly sized grounded conductor from ground lug in control / pivot panel to ground rod(s) and to the service entrance disconnect or generator ground (including ground rod at generator)

Fused disconnects (separate from service disconnect) for each piece of electrical equipment to be operated. i.e. pump, Pivot, injector pump, etc…

Proper fusing and fuse sizing of all electrical equipment.

Installation of a slug in the grounded phase of all delta and open delta connected power transformers.

Properly fused disconnect on the output side of generator to protect the generator.

Every installation shall be of a new and unused material, shall all meet applicable sections of the current National Electrical Code and installed in a good and workmanlike manner in accordance with accepted practice.

Meet and exceed the requirements of any agency having jurisdiction over installations.

]]> http://www.traxcoirrigation.com/pivot-system-grounding/feed 0 http://www.traxcoirrigation.com/sprinkler-package-center-pivot http://www.traxcoirrigation.com/sprinkler-package-center-pivot#comments Fri, 16 Mar 2012 11:33:46 +0000 Traxco http://www.traxcoirrigation.com/?p=2334 The sprinkler package is one of the most important components on a center Pivot since it must apply the water to the crop uniformly. However, the sprinklers maintenance is often ignored and not checked.

The sprinkler package is one of the most important components on a center Pivot since it must apply the water to the crop uniformly.

However, the sprinklers and the maintenance associated with that package are often ignored and not checked. Inspecting sprinkler package on a regular basis is as important as the proper maintenance of any other equipment on the Pivot, for example, the drive train components.

A sprinkler package must be properly designed. There are many factors that go into a proper design to ensure good distribution of water and to prevent excessive runoff. Some of these factors include field slope, soil texture, crop canopy height, sprinkler pressure, sprinkler spacing and sprinkler type.

It is also important to consider management (how the package will be used during the growing season). Once the design is completed and installed in the machine, it is important to make the following checks concerning the sprinkler package. The small investment in time this takes can pay big dividends by preventing reductions in crop yields. This list of checks should be made at least annually, and some should be performed several times during the growing season.

Checking for adequate pressure ensuring that sprinklers are operating at the correct pressure is one of the most important checks. The correct sprinkler chart. An accurate pressure gauge (or make sure that the one installed is working properly).

Check the pressure at the pivot point and compare it to the value on the sprinkler chart. The pivot pressure must be measured at the top of the pivot elbow as this is the standard in the industry and can then be compared to the chart value. The actual pressure at the elbow should be equal to or greater than the chart value. There’s also to check the pressure at a location just before the last sprinkler at the end of the machine. For both of these checks, the last drive unit should be located at the highest point of elevation in the field. All sprinklers should be running, including the end gun.

If the Pivot has a corner arm, it should be fully extended and at the highest point in the field with the end gun on. End pressure is measured just before the inlet to the last sprinkler on the machine. The measured value should be equal to or greater than the pressure identified on the chart at that sprinkler location. If the Pivot is equipped with pressure regulators, the measured pressure should be at least 5 PSI higher than the regulator rating. (Example: A 15 PSI regulator should have at least 20 PSI applied at the inlet of the regulator). If the Pivot/corner is designed to operate at 20 PSI at the end of the machine and it is only operating at 15 PSI, there will be at least a 15 % reduction in water applied. Pumping conditions can change throughout the growing season. Therefore, pressure checks must be performed at least once a month.

Checklist

Proper pressure is very important. However, performing these others checks at the beginning of the season is also very important to ensure proper sprinkler package performance. There’s to start the Pivot, making sure the pressures are adequate and walk the entire machine checking for the following:

Examine the sprinkler overlap and make sure it is sufficient. The outer edge of throw of a sprinkler should reach to the adjacent sprinkler as minimum. Check for any plugged or missing sprinklers.

Prior to start up, verify that the sprinklers are placed in the right locations with the appropriate nozzle size. The sprinkler chart can be used to verify this.

Take a panoramic view of each span to ensure each nozzle has a good pattern and they appear to be applying the appropriate amount of water for the area they are covering. If the soil type is similar in the field, a Pivot can be run fast over dry soil and then examine how evenly it is wetted.

Look for drops and sprinklers that may have been damaged during harvest or during the growing season. Drops that are severely bent will affect the pattern and overlap of the sprinkler.

Examine all sprinklers in operation for the following: fixed and rotating pads are not missing from the sprinkler, rotating pads are actually rotating properly, pads do not have a build-up of materials affecting their distribution pattern, impact sprinklers are rotating properly, ensure the end gun and booster pump are operating correctly.

Ensure regulators are operating properly, to make sure is not spraying out of the body. This might indicate a broken diaphragm or o-ring. The best way to check to make sure regulators are properly regulating pressure is to verify that the flow of the sprinkler matches the sprinkler chart (within 5%). Randomly select several sprinklers on each span, capture water from the sprinkler for at least 1-2 minutes in a container, measure the amount of water collected and detemine the flow rate.

]]> http://www.traxcoirrigation.com/sprinkler-package-center-pivot/feed 0 http://www.traxcoirrigation.com/new-zealand-farmers-center-pivots http://www.traxcoirrigation.com/new-zealand-farmers-center-pivots#comments Thu, 26 Jan 2012 17:31:21 +0000 Traxco http://www.traxcoirrigation.com/?p=2364 New Zealand dairy farmers are turning to mechanized irrigation to manage more cows per hectare of pasture, keeping those grasses more productive throughout the year.

]]> New Zealand dairy farmers are using center Pivots to enhance pasture grazing opportunities all 12 months of the year.

The grass is definitely greener for New Zealand dairy farmers. Many are using center pivot irrigation to further enhance one of that country’s most precious agricultural resources: pasture. According to the country’s agricultural ministry, New Zealand’s success in dairy production relies predominantly on highly productive, rotationally grazed pasture and herds of high genetic merit. The warm climate and productive pastures enable herds to graze in pasture year-round, thus avoiding the need for indoor housing and expensive feed supplements.

The country’s dairy industry, which began in 1814 with the importation of two cows and a bull, is today one of New Zealand’s most dynamic agricultural assets. Exports from what is termed “pastoral agriculture” accounted for nearly half of all goods exported from New Zealand. The dairy industry (the largest industry within the pastoral sector) accounted for nearly half of those exports. New Zealand dairy products far exceed what the country’s 4.3 million residents can consume. But the export market is strong, taking 90-95% of dairy production and selling it on the world export market as cheese, butter, milk powder, and other dairy solids.

Mechanized irrigation

More cows per hectare of pasture

Dairy farmers, always looking for more efficient milk production practices, are turning to mechanized irrigation to manage more cows per hectare of pasture, keeping those grasses more productive throughout the year.

Pasture grazing is New Zealand’s greatest agricultural asset and an inexpensive way to get nutrients into the animals. Sheep farming is still viable, but dairy cow numbers have increased dramatically, while sheep numbers have dropped. Their average yearly rainfall is 635-762 mm, enough to ensure pasture growth for much of year, but center pivot irrigation linked to rotational grazing allows them to intensively graze pasture grasses all year long… even during their winter months (june, july and august).

Dairy farmers like to allow 48 hours after irrigating before grazing a particular section. That lets the plant dry out and increases the sugar content. There is very little supplementary feeding. They monitor consumption of the grasses and any other dry matter being fed. Dairy herds need to produce large quantities of milk to be succesful, but quality is also important since pricing is also dependent on milk solid content. Farmers don’t want colored water, they want milk with good protein content; to do that they must keep the dry matter and energy content high in the pasture.

Pastures under center-Pivot irrigation

Water application rates are low, often around 6 mm, because the sandy loam soils have high infiltration rate and good drainage. Center pivots are low pressure machines (30-35 PSI at the pivot) with drops that place sprinkler heads close to the crop.

They know pasture water consumption rates (pastures are usually a mixture of ryegrass and white clover) and the soil handling capacity, so they only apply water the plant can use. Then, if it does rain, they don’t risk saturating the soils.

Center Pivots are sectioned into different wedges. Fenders constructed from plastic coated metal tubing extending on both sides of each tower to direct electric fencing beneath the tires. This allows the pivot to move from one grazing area to another easily and without labor in the field… a pasture management concept used succesfully in Brazil for several years to produce grass-fed beef cattle under Pivots.

Dairy farmers aren’t the only ones using mechanized irrigation. Both linears and Pivots are being used succesfully in the production of vegetable crops like peas, carrots, potatoes and cabbage, as well as cereal crops. Center Pivots are programmed to make a complete circle every 48 hours applying 6 mm of water. Mild weather year-round and relatively low evapotranspiration rates make longer machines a suitable choice in many situations. For the New Zealand dairy farmer, raising grass is by far the best feed option.

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It can easily be fitted to any make of center-Pivot. Wheel track furrows have for many years been a problem with center Pivot irrigation in certain types of soil.

When tracks are deeper than 100 mm there’s a risk of damaging the tower structure when wheels are forced to follow deep wheel furrows. Center pivot often get stuck in furrows where water tend to gather, softening the track even more. During spraying, cutting and harvesting operations deep tracks cause problems as well.

How does it work?

With new installations, it becomes a preventative action as the two adjustable and perfectly angled disc wheels cut the soil, pushed out by the tyres, back onto the track preventing furrows from forming. It can be adjusted to form a slight ridge, keeping water from standing in the tracks.

With installations where deeper tracks already exists, the discs can be adjusted deeper by putting more tension on the adjustable spring, filling the furrow with every rotation.

Features

It can fit all makes of center Pivots. It has an adaptor plate fitted between the gearbox and gearbox mounting plate.

Although equiping all the drive units in a multi tower machine would make life easier, in less severe conditions units can easily be moved from one tower to the next by simply buying adaptor plates for all the towers and rotating the unit between towers by using the simple pin assembly, and thereafter re-adjusting the spring.

It’s not necessary to equip all center pivots with it. In less severe conditions, one set that fully equip a center pivot can be rotated regularly between the other center Pivots.

If the problem is happening only in one tower, one unit can be used on a permanent basis.

To reverse the center pivot, the unit must be simply swung up against the tower leg.

A speciality vegetable facing proce pressure from imports, malanga is nevertheless a significant part of the cropping program in Florida (USA). We are going to focus on the experience of a second generation farmer in South Florida who has grown malanga all his life, beginning at the side of his father. For a few years they irrigated with overhead big guns. Now they have center Pivots and linears that take the place of 60 overhead rigs. They get the job done a lot quicker, and the savings in their irrigation labor costs is phenomenal. With Pivots they need one man, one machine and one pump, so they save a lot of money.

Growers are impressed with the way linears and center Pivots apply water in all weather conditions. Whether it’s warm and calm like it usually is in the fall, or hot and breezy like it can be in the spring and summer, there’s virtually no water wasted. They can irrigate 24-hours a day all year long if that’s what the crop needs. That’s particularly important with malanga, which takes a year or more to reach maturity. That’s why malanga growers must irrigate throughout the hot, dry and windy summer months in South Florida.

A tropical crop which originated in Central and South America, malanga has also been grown for centuries in Cuba and Puerto Rico. South Florida’s diverse population assures a steady local demand for this root vegetabke with large green leaves that can measure more than 2′ across. Edible tubers which form in the soil at the base of the plant are harvested, processed and added to recipes much like potatoes. And like potatoes, malanga has a distinctive starchy taste, yet with its own unique flavor.

Malanga is relatively easy to grow if it’s possible to control the stubborn grasses with herbicides and some hand labor. As the crop matures and fills out, grasses present less of a problem. Malanga growers irrigate about once a week starting soon after planting and continuing all year long, depending on weather conditions.

Planting to harvest takes around 12 months, sooner with sandier soils, longer with heavy clay. With a Pivot on sandy soils, a farmer could harvest in as little as 10 months, applying about 1.5″ of water per pass.

The farmer in question runs the center Pivot 36 hours at 30% to cover 123 acres of malanga. An adjacent field of sweet corn is irrigated at 60% for an application rate closer to 0.75″ per pass. They rotate malanga with corn so they have two crops under irrigation at all times. Their system pumps 1500 GPM so it takes 36 hours for each water application on malanga, 18 hours for corn.