F.A.Q
Irrigation 101
Q. WHAT ARE THE DIFFERENT TYPES OF IRRIGATION?
A. The primary type of irrigation system in Texas is the center pivot irrigation system, with approximately 23,000 center pivots in Texas. Drip irrigation in vegetable and orchard production, as well as solid set sprinklers and traveling guns are also irrigation systems found in Texas.
Q. HOW DO IRRIGATION SYSTEMS WORK?
A. Irrigation systems supply supplemental water to plants either by spraying/sprinkling water from above onto plants and soil (overhead irrigation); by dripping water from a tape or tube onto the soil surface adjacent to plants (drip irrigation); or by dripping water from a drip tape that is buried in the plant root zone (subsurface drip irrigation or SDI). Center pivot irrigation systems are a common type of overhead irrigation found widely in the state of Texas for row-crop ag irrigation.
Q. HOW DO CENTER PIVOT IRRIGATION SYSTEMS WORK?
A. A center pivot system is essentially a large pressurized water supply pipe that mechanically moves in a circular fashion across an ag field. The main pipe is divided into “spans” which are supported by “towers” with drive motors and the pipe is anchored at the center of the circle – hence the name “center pivot” systems. The span pipes, often 14-16 feet above the soil, are fitted with sprinklers either directly in the pipe itself or suspended below the main pipe on “drop hoses” to get the sprinkler closer to the soil and plants. The sprinklers release the water that falls from above and wets the soil and supplies the plant roots. They are powered by electricity or diesel fuel.
Q. HOW DO DRIP IRRIGATION SYSTEMS WORK?
A. With drip irrigation, water is slowly provided to the area adjacent to the roots of the plant, usually by a network of pressurized lateral lines, drip tape or tubing, and finally, drip emitters. Drip irrigation can have the drip tape or tubing on the soil surface or could be buried drip tape in the root zone (subsurface drip irrigation).
Q. HOW MUCH WATER DO CROPS USE?
A. The amount of water crops use depends on the crop, variety, and growth stage.
Q. WHEN SHOULD I IRRIGATE?
A. If irrigating a plant, you would want to irrigate when the soil moisture in the plant's root zone has been used up by the plant such that there isn't enough moisture left to keep the plant growing optimally.
Q. WHAT IS THE BEST TIME OF DAY TO IRRIGATE?
A. Nighttime is the best time to irrigate to reduce water loss from evaporation.
Q. WHERE DOES IRRIGATION WATER COME FROM?
A. Our irrigation water comes from the ground or from surface water. Ground water comes from aquifers. Surface water comes from lakes, rivers, ponds, streams, etc.
Q. WHY DO WE IRRIGATE?
A. Irrigation is the best risk management tool to safeguard against unpredictable rain patterns and drought.
Q. WHAT DOES IT COST TO IRRIGATE?
A. Irrigation costs can vary greatly. For urban lawn, landscape or garden irrigation, the cost to irrigate is driven by the price of water provided by the local water purveyor. For ag irrigation, the source is usually not a water purveyor but is instead from a ground water or surface water source with a pump of some sort powered by electricity, diesel or LP gas. In the case of ag irrigation, the “cost” is related to the energy cost involved in pumping/moving the water from the source to the irrigation system. UGA Extension estimates the cost at $7 per acre-inch of irrigation water applied when using electricity for the pump.
Rules of Irrigation
Q. HOW IS IRRIGATION MONITORED. MEASURED, AND REGULATED IN Texas?
A. The water resources in Texas are managed primarily by the Environmental Protection Division (EPD). The state "Texas manages water resources in a sustainable manner to support the state's economy, to protect public health and natural systems, and to enhance the quality of life for all citizens."
Q. DO I NEED A PERMIT TO IRRIGATE?
A. Not in Texas. In Texas you do need a permit from the Environmental Protection Division (EPD) for an ag water withdrawal if the pump involved in the withdrawal point is capable of pumping 100,000 gallons per day.
Q. I'VE HEARD THERE'S BEEN A SUSPENSION PUT INTO PLACE ON ANY NEW AGRICULTURAL WELLS IN SOUTHWEST Texas, IS THAT TRUE? WHAT DOES THAT MEAN?
A. This is true. In July of 2012, Texas EPD issued a suspension of any new permits for ag water withdrawals (or change in current withdrawal permits) fora a large region of southwest Texas emcompassing the lower Flint River basin area. This affects permits related to the Upper Floridan Aquifer ground water AND surface water in the more southern reaches of the suspension, and relates to permits using surface water in the more nothern reaches of the suspension area. It means that if you need a permit for an ag water withdrawal, you must look for other water sources.
Q. HOW LONG WILL THAT SUSPENSION LAST?
A. The suspension can go on indefinitely. The director of EPD reviews the conditions in the region each November and decides if the suspension should continue.
Soil Moisture Sensors
Q. WHAT ARE SOIL MOISTURE SENSORS?
A. Soil moisture sensors are electronic devices that are installed in the soil profile, usually in the plant’s root zone, and provide the user with information related to the amount of soil moisture available to the plant. The information might be provided in terms of “percent soil water” or could be a measure of soil water tension in “kiloPascals” or “centibars”.
Q. WHAT ARE THE DIFFERENT TYPES OF SOIL MOISTURE SENSORS?
A. A multitude of commercial sensors exit on the market, and fall into to two primary categories: tensiometric and volumertric (or capacitance). Capacitance probes use special capacitor related sensors to measure the volume of what in the total volume of soil-- a soil parameter called the dielectric permittivity. Tensio metric soil moisture sensors measure "matric water potential" or soil water tension. This is the amount of energy ('suction') that a plant's roots must exert to extract soil water.
Q. HOW DO SOIL MOISTURE SENSORS HELP WITH WAER MANAGEMENT?
A. The purpose of a soil moisture sensor is to monitor soil moisutre status, which allows the farmer to prevent plant stress by maintaining soil moisutre at optimal levels . Soil moisture sensors allow you to determine if there is adequate soil moisture for the crop, if the soil is drying or if the soil is very dry.
Q. HOW DO I INSTALL A SOIL MOISTURE SENSOR?
A. Each sensor or probe type requires an appropriate installation method. In general, soil moisture sensing equipment must be installed in the soil with good sensor to soil contact. If using individual sensors, a hole must be opened to the depth of interest and then the sensor is installed and soil back-filled into the hole using either a soil-water slurry or a soil-only approach. For probes, a hole is opened up deep enough for the entire probe length and to the depth of interest in the soil. Similarly, after the probe is installed, soil is back-filled into the hole using either a soil-water slurry or a soil-only approach. Some probes are now installed with a dry install where the hole is opened to nearly the exact dimensions of the probe which is then pressed into the hole, requiring no back-fill.
Q. CAN I LINK MY SOIL MOISTURE SENSOR TO MY PIVOT TO IRRIGATE WHEN DRY?
A. From what we understand, currently you cannot link your soil moisture sensors to your center pivot to automatically start the pivot based on soil moisture status. Manufacturers certainly offer the ability to read soil moisture sensors through their control panels, but not automatically start a system. Drip irrigation offers this option.
Q. HOW MANY SENSORS SHOULD BE INSTALLED IN A FIELD?
A. If your field is highly variable, it would be good to install sensors in 2 to 4 sites in the field to give you information on soil moisture status in the difffent soil zones in the field. If cost is a major factor or if your field has a single, uniform soil (we rarely see this), then you could install a sensor system in a single location in your field.
Center Pivot Irrigation
Q. WHAT'S THE DIFFERENCE BETWEEN A HIGH PRESSURE IMPACT SPINKLER AND A LOW PRESSURE SPRAY TYPE SPRINKLER? WHY ARE LOW PRESSURE SPRAYS ON DROPS MORE WIDELY USED TODAY?
A. Sprinklers actually deliver water from the center pivot irrigation systems to the soil and crop. High pressure impact spinklers are designed to operate at relatively high pressure and send water out over a large wetted area, in smaller water droplets, from a release point at the top of the center pivot-- 14 to 16 feet above the soil. The high release point and small droplets are a recipe for water losses-- from evaporation, from wind drift, etc. Conversely, low pressure spray-type sprinklers on drop hoses are sprinklers mounted on the end of hoses that suspend the sprinkler far below the center pivot pipe, but still well above the soil and crop. These sprinklers are designed to operate at very low pressure and thus the water is delivered over a smaller wetted area in larger droplets-- thus much less losses from evaporation and/or wind drift.
Q. WHAT IS AN END GUN?
A. An "end gun" is a large irrigation sprinkler designed to apply a large amount of water over a large araea. It is often mounted on the end of a center pivot irrgiation system to extend the wetted area beyond the physical end of the center pivot pipe to water more crop area.
Q. SHOULD I CONTROL MY END GUN?
A. You should have working controls for your end gun that sprays water over areas that you don't want to water. That could include preventing water from being sprayed on roadways, adjacnet forest land, houses, even adjacent farm land that isn't yours.
Q. CAN I CONTROL MY PIVOT SYSTEM REMOTELY?
A. Absolutely! With today's advanced technologies, in particular SmartPhones, you can add technology to your center pivot control panel that enables you to control the system remotely from your iOS or Android SmartPhone.
Q. WHEN SHOULD I RETROFIT MY SYSTEM, AND WHEN SHOULD I REPLACE?
A. If your center pivot is in good working order other than the actual sprinklers, then consider replacing the sprinklers with new ones once the sprinklers and their impact pads are worn – usually 5-10 years depending on your water quality. Similarly, if your center pivot is fitted with inefficient impact sprinklers, consider retrofitting to more efficient low pressure spray-type sprinklers on drop hoses. However, you should consider replacing the entire system if the center pivot itself (control panel, gear boxes, drive lines, tires, mainline pipe, support structure) is worn, rusted, or damaged beyond its useful life.
Smart Irrigation
Q. WHAT IS SMART IRRIGATION?
A. Smart Irrigation is the right amount of water in the right place at the right time to optimize growth and efficiency. Efficiency refers to the amount of water pumped that is utilized by the crop.
Q. WHAT IS IRRIGATION SCHEDULING?
A. Irrigation scheduling is a technique that involves determining how much water is needed and when to apply it to the field to meet crop demands.
Q. WHAT IS VRI?
A. VRI stands for Variable Rate Irrigation. Most agricultural fields are highly variable, meaning multiple osil types, elevation changes, and non-cropped areas. VRI allows farmers to apply customized rates of water based on indivaual management zones under the pivot according to soil and crop needs. This improves water use efficiency and and decrease run off and nutrient leaching.
Q. WHAT IS VFD?
A. VFD stands for Variable Frequency Drive. VFD units control the speed at which an electric motor spins an irrigation pump. It monitors line pressure to keep your line presure at the right level. If you have a center pivot that has an end gun that is controlled over non cropped areas or VRI controls that turn on/off sprinklers, a VFD can help prevent pressure spikes when flow is lessened.
Q. ARE THERE SMARTPHONE APPS THAT WILL HELP ME DETERMINE WHEN TO IRRIGATE?
A. There are several Smart Irrigation app for both iOS and Android for several agricultural crops,. Each app generates irrigation recommendations for it's specific crop according to thei particular characteristics and phenology of that crop. One of the most useful features of the app is the ability to receive notifications when irrigation is needed, rain events are observed in the field, and approaching phenological stages.
Urban Irrigation
Q. WHEN CAN I IRRIGATE MY LAWN?
A. Irrigation on your lawns and lanscapes is permitted between 4 p.m. and 10 a.m. On average, lawns need about one inch of water per week.
Q. WHAT ARE SOME TOOLS I CAN USE TO IMPLEMENT SMART IRRIGATION AT HOME?
A. There are lots of tools that allow homewowners to use Smart Irrigation practices in their lawns and landscapes. This can be as sohpisticated as rain sensors and soil moisture sensors connected to your sprinkler system, or something as simple as a rain guage that can allow you to make more informed watering decisions.
Q. WHAT HOME IRRIGATION SYSTEM IS BEST FOR ME?
A. Tailor your irrigation system to your plant needs for the most efficient water use. While rotor or spray sprinklers may be best for turf and large areas, drip irrigation is best in garden beds.
Q. WHAT ARE SOME CONSIDERATIONS WHEN PLANNING MY LANDSCAPE FOR MAXIMUM IRRIGATION EFFICIENCY?
A. Plant choice is of the upmost importance! Select turfgrass and plants that are well adapted to the climate, and group plants with similar sun exposure and water needs to increase efficiency. You may also consider the plant functionality, such as incorporating an herb or vegetable garden. Adding organic matter to the soil and mulching landscaped areas are also some planning considerations that can impact water efficiency.
Q. I WANT TO LEARN MORE ABOUT BEING A SMART IRRIGATOR AT MY HOME. WHAT SHOULD I DO?
A. There are lots of ways you can get involved and learn more about Smart Irrigation in your own landscapes and lawn. Your local extension office is a great resource for learning more and planning your landscape. You can also take the My Drop Counts pledge-- a statewide campaign to commit to Smart Irrigation at home-- at mydropcounts.org.