Irrigation Water—Handle With Care!
by Cindy Dvergsten,
There is no doubt that awareness and creativity are essential to whole ranch planning and management, and this is especially true with our capacity to manage irrigation water in as sustainable manner as is possible.
Irrigated pasture and hay land provide critical
winter hay reserves and spring grazing to ranchers who depend on
other lands for summer pasture. Many types of wildlife also depend
on irrigated pastures. Irrigation is essential for enterprises such as grass finished meat products,
crops, market
gardens, pasture-based dairies, vineyards, and orchards. Rapid
population growth in the Western states puts intense demand on
a limited water supply. Like many producers, we do not take for granted the right to
use irrigation water at our farm in Southwest Colorado.
We find that practicing irrigation water management brings us
closer to the land as we strive to make every drop of water and
every square foot of land count toward enhancing life, providing
food for our community and building
soil.
The Art of Irrigation
An experienced irrigator is as much an artisan as they are a technician. Not only must they understand the technical workings of the system they work with, a good irrigator must develop a keen understanding of plant, water, and soil relationships. Other key considerations in irrigation water management include the efficiency of your delivery system, soil type, climate, irrigation water quantity and quality, crop needs, labor and available money. Knowing when to irrigate, how much water to apply, and how deep to irrigate is central to planning for effective water use.
In mountain states, many irrigation systems rely on earthen canals and field ditches to get water to the pasture or hay field. Irrigators use tarps to create dams in ditches in order to direct water into a field and shovels to fine tune the spread of water across the field. The more uneven the pasture, the more effort it is to get a good distribution of water. In these situations, irrigation water management is impossible without experienced labor yet, it is difficult to find an artisan irrigator these days.
Improved water conservation is possible using more efficient systems such as pressurized sprinklers or gated pipe and replacement with pipelines, which may save considerable labor as well. Nonetheless, even the most efficient irrigation systems require good irrigation water management.
Observing the land through the four ecosystem processes helps us to evaluate the effects of irrigation, which like any other tool can be over or under applied. The following symptoms are common indicators of over irrigation:
Water Cycle
1)
Presence of a high water table that hinders root development;
2)
Artificial wetlands;
3) Unplanned runoff, soil erosion, and
sedimentation of ponds, ditches and streams;
4) Surface waters
polluted from herbicides, salts, and fertilizer leaving the field;
and
5) Soils impervious due to loss of soil structure.
Mineral Cycle
1)
Soils stay saturated and may smell like a swamp due to anaerobic
conditions;
2) Salts accumulate on the soil surface; and
3)
Nutrients are lost due to leaching.
Community Dynamics
1)
Water-loving plants like cattails, chicory, willows, and ragweed
appear where they normally do not grow;
2) Increase in
shallow-rooted plants with a decrease in deep-rooted plants such as
alfalfa;
3) A root bound sod forms;
4) Decreases in earthworm
activity.
Energy Flow
1)
Production is low;
2) Forage quality is poor; and
3) There is a
general lack of response to other tools of management including a
poor return on labor and money.
Applying too little water leads to its own set of problems indicated by wilted, stunted or dying plants; increased plant spacing and bare soil; decreasing organic matter content; a lack of response to fertilizer application; increases in drought tolerant plants and annual forbs, decreased earthworm activity and low production. Early warning monitoring techniques include frequent evaluation of soil moisture conditions and crop needs.
Know Your Soils & Plants
As with grazing planning, irrigation water management is a matter of adjusting the length of time and frequency water application. To avoid over irrigation, apply water at a rate no greater than what the soil can take in. The intake rate is calculated as inches per hour. Heavy soils take water in more slowly, whereas sandy soils take water in more rapidly. Apply water only long enough to fill the rooting zone to full capacity. If the soil holds salts, enough water needs to be applied to carry the salts down below the root zone, but not so much to cause deep percolation.
Calculate the frequency of irrigation based on the needs of the plants measured as inches of water consumed by the plant over a period of time; and the available water holding capacity of the soil measured as inches of water per foot of soil. Total water holding capacity may be higher than the available water because very fine particles of soil hold water so tightly plants cannot extract it.
Plant needs vary by type of plant, stage of growth, and climatic conditions. Plants use water for transpiration while some is lost to evaporation. Calculating the evapo-transpiration rate or ET rate, is one way to estimate water use by crops. Plants demand more water in dry, windy conditions, where the evaporation and transpiration rates are high, and less water when there is effective rainfall. Likewise, rapidly growing plants will demand more water than those that are mature or dormant. Current ET rate calculations are available in from most University Extension Agents.
Completing the Feedback Loop
Advanced planning and irrigation scheduling is important to achieving desired outcomes. By staying on top of what is happening in the field with irrigation and grazing we are able to enhance productivity of the land and performance of the animals.
We use the Holistic Management® Grazing Plan and Control Chart to schedule irrigations. Steps three and four in the Aide Memoire for Holistic Grazing Planning suggest that we consider all management concerns that affect the whole grazing cell we are working with and record livestock exclusion periods. Since irrigation is essential to productivity and affects nearly every other activity, we plan it first.
To begin with, we determine when we normally begin to irrigate and then plan the number of irrigations and length of time per irrigation for each field. We use a light blue colored pencil to show planned irrigations and dark blue to show the actual irrigations as they occur. This practice has helped us coordinate grazing with irrigation in a manner that maximizes management of both.
Achieving a high degree of efficiency and effectiveness with irrigation water management demands close early warning monitoring of field moisture conditions and making adjustments as necessary. We monitor the depth of irrigation and soil moisture content on a daily, weekly or as needed basis to make adjustments for unpredictable climate and field conditions. While there are many high-tech methods available to monitor soil moisture, we find that simple field tests are sufficient for most irrigated pastures.
Generally, it is best not irrigate unless soil moisture, climatic conditions, and crop needs indicate irrigation is necessary. Most forage crops do well when the next irrigation is deferred until 40-50 percent of the available soil moisture remains. Letting the upper portion of the soil profile dry out allows for aeration and deep rooting.
Before irrigation, we estimate soil moisture by feel and appearance using a visual guide available from the NRCS (Program Aid Number 1619.) Soil moisture typically is sampled at one-foot increments down to the rooting depth. The feel and appearance of soil varies with texture and moisture content and with practice, an irrigator quickly estimates soil moisture conditions to an accuracy of about 5 percent.
After irrigation, we simply push a soil probe into the soil until it will not go any further. This tells us the depth we have filled the soil to field capacity. Steel rods with a ball tip work well as probes in soils that are free of impediments. In rocky or stony soils, using an auger or shovel is necessary to determine depth of irrigation.
Do not irrigate deeper than what the type of crop requires and soil moisture situation dictates. Most forage crops take 40 percent of their moisture from the top 25 percent of the rooting zone and lesser amounts from lower portions. For this reason, and because of evaporation, the soil surface will be drier than deeper levels. It is most desirable to wet the full rooting zone. However, in very hot dry conditions, you may only be able to keep the upper root zone moist. However, prolonged shortage of water in the lower root zone will affect plant performance.
To prevent over compaction, we remove grazing animals during irrigation and keep them off for two to three days afterwards, or until the surface as dried. The sooner the irrigation starts after grazing, the sooner the forage will begin to recover (provided field tests show a need for water). We have found electric fencing is an invaluable tool when managing grazing around irrigation since there are many options available to accommodate irrigation and holistic grazing practices.
Labor and Water Savings
Labor considerations are a major concern for most producers. Planning irrigations out ahead of time allows us to see the big picture and plan our time effectively. We are better able to mesh the demands of irrigation with our schedule in way that enhances our quality of life. This is important to my husband who works a full time job in addition to moving the irrigation pipe on our pasture. He enjoys starting the day off with fresh air and exercise, but does not like to be out in the field late in the evenings. Likewise, I plan time to irrigate the market garden and orchard to fit with my schedule.
Planning in advance and practicing irrigation water management along with holistic grazing has allowed us to reduce the amount of irrigation water we use by approximately 15%, increase in the productivity of deep-rooted perennial grasses and reduce the amount less productive shallow rooted grasses and forbs. Deep root grasses tolerant dry spells better should we run out of irrigation water in a dry season.
The manager must carefully test options for improving irrigation water management toward their holistic goal. As difficult as it may be to justify training an irrigator only to see her move on in a couple months, it is also difficult to justify the expense of installing irrigation systems such as side-roll sprinklers that require less labor. I encourage people to pay careful attention to their marginal reaction for labor and money, their managerial effectiveness, and quality of life issues as well as land health and productivity.
Managers Keith and Wendi at Rocking J Ranch who in their first months of practicing Holistic Management, have recently tested options concerning irrigation water management and labor. Like many managers they believe that if they work hard enough, they can do it all – manage yearlings on the gain, finish steers on grass for local and distant markets, cut hay, build fence, train interns, home school children and irrigate. The thought of hiring labor seemed crazy because after all, it was too expensive, or so they assumed. A paradigm shift occurred when, with their holistic goal in hand, they penciled out the option to hire a laborer to irrigate.
They identified resource conversion as their weak link with irrigation water management being their point of focus. Using the Holistic Management testing guidelines, they soon realized that the time Keith spent on irrigating had a low marginal reaction. This time, they figured, would realize a higher return on his time if it were spent managing yearlings to achieve high rate of gain while improving pasture quality and more importantly if it were spent recreating with his family. “His being frazzled and working long hours was causing our quality of life to suffer”, says Wendi of Keith who added, “Not only that, but neither the irrigation nor the grazing were being managed very well.”
Keith calculated the cost of hiring an experienced irrigator to be about $1600. This would free up at least 100 hours for Keith to spend quality time with his children and focus on managing stock density to achieve high level of animal performance. Computing the return for a higher rate of gain on yearlings plus the value of harvesting an additional 100 tons of forage from his irrigated fields, Keith figured he could pay for the irrigator and increase ranch income by $7000.00.
Keith and Wendi noted that writing everything out on paper and using the Holistic Management testing guidelines helped them see beyond their assumptions. Finding a suitable irrigator has been a challenge. They realize now, the importance instilling a sense of ownership in their labor force and are working on action plan to make recruitment and retention of high quality labor just as much a part of their management program as the cattle are. They are excited about improving their quality of life while also improving the land, increasing their income and building community.
Final Notes
Local irrigation practices vary widely, and there are many concerns regarding irrigation system design that go beyond the scope of this article. For more information on soils, irrigation system design, and climatic data contact your local Natural Resource Conservation Services (NRCS) or University Extension Agent.
Managing irrigated pastureland involves an intricate application of the tools of management to achieve a high quality of life, prosperity, healthy land, and strong communities. Taking time to observe and evaluate plant, soil and water relationships is enjoyable and enhances our ability as agricultural producers. It is rewarding for my husband and myself to see happy animals enjoying healthy land supported by our wise use of precious water resources, and to be able to market these values to our community.
this article is copyrighted © by Cindy Dvergsten. Permission must be requested in writing for use of this article by contacting Whole New Concepts LLC.
