Great Bend Tribune
Published September 11, 2016
Agriculture and Water
If you live and/or farm in Kansas there are several givens in your life. The wind will blow; there will be heat; we all think about water and precipitation. There is either too much or too little water for us but seldom just the right amount. We are afraid to complain when it rains and storms because we all know precipitation can disappear for long periods of time. For the farmer, or rancher for that matter, adequate soil moisture for crops is the difference between staying in or going out of business. That is why the development of practical irrigation methods was so vital to farming, the beef industry, and the overall economy of Western Kansas. We will deal with water, irrigation, and water scarcity later. This week’s column takes a moment to briefly examine the role of water in plant growth and development, starting with germination.
- Adequate soil moisture is necessary for the seed to take in water and begin the processes that activate the embryo. This includes breaking down food reserves in the seed and transporting them to the embryo so the radicle, seed root, can emerge and the plant can emerge from the soil and develop leaves to supply the nutritional needs of the plant. If there is inadequate soil moisture the seed cannot germinate. Worse is when there is enough water for the seed to germinate and start to grow, then run out of moisture and the seedling dies.
- Adequate water is necessary for the plant to maintain turgor pressure. In plain English, cells need enough water for the cells to be full. When inadequate water is present due to moisture or heat stress, the plant cells cannot maintain turgor and wilt. Wilting is actually a defense mechanism to protect the plant. As long as the plant can regain turgor when conditions improve (overnight or higher humidity or lower temperatures or precipitation) the plant is okay although it may be injured. If the plant cannot recover, say overnight, it is termed the permanent wilting point and the plant cannot recover.
- Water is absorbed by the roots and transported by the xylem to the rest of the plant. This water serves several functions. It helps the plant maintain turgor pressure, cool itself, transport nutrients such as nitrogen and phosphorus for plant growth and development, and the big one – photosynthesis. Plants take radiant energy, typically sunlight, and use carbon dioxide and water to produce sugar which is a building block and energy source for the plant and its cells. The source of that water is from the soil through the roots. If water cannot move through roots throughout the plant with some leaving the plant through pores (stomata) under environmental conditions, water uptake can’t take place. This stops all the processes listed in this bullet point.
Finally, plant roots must be constantly growing to explore the soil to obtain water and nutrients. Roots cannot grow through dry soil so even if moist soil is only inches away, the root cannot grow to it. That is why irrigators hate to pull the trigger on water too early and why wet early season conditions result in a less developed roots system unable to cope when stress arrives.
Part II
Last week’s column focused on water in plants. This week features water in the soil. As always, this is simply a brief overview that covers the highlights. The water contained within plants comes from the soil and is extracted by young, actively growing roots cells. The ability of the soil to hold water and allow roots to extract it is a function of the following:
- Soil texture describes the percentages of sand, silt, and clay that make up the soil. Sand is unable to hold water while silt can hold a minor amount. Clay, because it is negatively charged attracts and hold water. The amount of water a soil can hold against gravity is a function of the amount of clay and the type of clay (there are many). As clay content increases so does the soils ability to hold water. While the soil can hold more water with more clay, less of that water is available so the plant will wilt at a higher soil moisture content. Sandier soils hold less water but a greater percentage of it is available. Clay soils dry out more slowly than lighter, less clay, soils.
- Organic matter, like clay, typically has a net negative charge and can hold many times its weight in water. So if a producer, or gardener for that matter, can increase the humus content of the soil they increase the water holding capacity of the soil. This is practical for producers while changing the soil texture is not. However, it takes careful management and times to significantly increase the humus content of soil on a large scale.
- Pore space matters also. The soil is made up of “stuff” and “not stuff.” The stuff is the mineral and organic components of the soil. The not stuff is pore, or void, space. The ideal soil for plants is approximately fifty percent of each and the half that is space should be about half air and half water. Pores also come in various sizes. Large pores allow water into the soil and for it to move downward. Small pores hold the water in the soil against gravity through capillary action and clay content. Pores also allow gas to be exchanged (plant roots need oxygen too) and plant roots to grow through. A mixture of large and small interconnected pores is best. Too many large or small pores upsets the ideal balanced.
- Finally, what is at/on the soil surface matters. Residue accumulating at the soil surface allows more water to infiltrate, serves as a vapor barrier to decrease soil water loss, and keeps the soil cooler which also decreases evaporation.
Next week will finish this series tying everything together.
Part III
So far we have focused on water in plants and water in the soil. Now let’s focus on water in the atmosphere, crop water needs, the soil, and tie it all together. It would seem, based on the last two columns that the amount of water a plant needs to produce a given amount of biomass, forage or grain, would be clear cut as would the soils ability to supply the plant’s moisture needs based on soil type, organic matter, structure, and so on. However, this is where the atmosphere and climate can throw in a monkey wrench.
If you check the literature, you will find guidelines as to how much water it takes to produce a bushel of corn or ton of hay. There are minor differences in terms of maturity and genetics but it is fairly well-established. As this is discussed, remember that water moves from the soil to the roots and out through the leaves in response to a vapor pressure gradient between the interior of the plant and the atmosphere. However, the following atmospheric/climate factors change this amount:
- Temperatures, both air and soil, affect crop water needs. Temperature determines the rate of growth and development. As you move towards the high and low extremes, development and water uptake are effected. At higher temperatures the water use of the plant increases, especially with the next two factors unless so high that the plant must shut down.
- Relative humidity of the atmosphere plays a major role in crop water needs. The higher the relative humidity, the less water needs to move through the plant to minimize stress and maintain plant growth. Even with higher temperatures, the plant is better able to function with a high relative humidity.
- As you can guess for Kansas, wind also plays a role. The higher the wind speed as a rule, the greater the rate the plant will move water through the roots, stems, and leaves into the atmosphere.
- The relative effects of these factors is a function of plant growth stage, soil moisture, and soil texture.
- Putting these factors together – high temperatures, lower humidities, and wind – results in the plant needing more water to produce a bushel of grain or ton of forage than where these factors are more favorable. So on average, it takes more water to produce a bushel of corn in Southwest Kansas than in the Northeast part of the state.
- Where do conditions tend to lead to more stress through temperature, humidity, and wind? The areas which tend to receive less precipitation and have higher water loss rates from the soil. If you look at the average precipitation across the state it is highest in the southeast and decreases as you move north and west, from around forty inches to twelve to fifteen inches. A map of irrigation allocations is the reverse of the precipitation map which makes sense from a crop growth standpoint, results in the problems faced today with groundwater depletion.
Next week’s column ties this all together.
Part IV
Today, we will attempt to tie the last three weeks together into the issues facing agriculture and water for Western Kansas. The idea with these columns is to briefly try and link together the factors creating the dilemma for crop production in Western Kansas and what it all means. To review briefly:
- Plants needs water for a variety of functions from photosynthesis and nutrient movement to maintaining cell turgor and growth.
- Water for the plant is extracted from the soil by roots for transport throughout the plant.
- The ability of the soil to take in water, hold it, and provide it for plant use is a function of the soil type, organic matter, structure, and depth. These also determine the rate that plants can extract water for use.
- The climate and weather determine actual plant water needs. Relative humidity, temperature, and wind either increase or decrease the water needs of the plant and its level of stress. Lower humidities, higher wind speeds, and higher temperatures increase the amount of water needed for a given level of crop production.
- Irrigation allocations increase as average precipitation decreases. In Kansas irrigation allocations increase from east to west, mirroring increased plant water needs.
For a more detailed explanation, see the previous three articles. In English, plant water usage is higher in the western half of the state due to climate. Most, not all, of the state’s irrigators rely on groundwater from the Ogallala.
The easiest way to view the Ogallala is as a checking account. It had a starting balance accumulated over thousands of years. Like any checking account there are deposits and withdrawals. As long as the total amount of deposits exceeds the total amount of withdrawals, life is good. However, if you withdraw more money than you are putting in, your balance declines. You are running a deficit or in groundwater terms, depletion. You can continue to withdraw more money than you deposit but eventually the money is gone, your account balance is zero so there are no more withdrawals, and the only money you have is what you bring in at any given time. So what can you do?
- Replenish your account by depositing funds. Meaning you quit withdrawing and make deposits only.
- Spend only what you have on hand. Trim your expenses to meet your income.
- Find new sources of income.
- Find more efficient ways to use your income.
- If we can’t find a way to handle this debt, we go out of business.
We are that person dealing with a bank account where we have withdrawn more than we have taken in for decades. Next week, how can we manage this problem?
Conclusion
The past four columns have provided a brief overview of the water dilemma Western Kansas faces with the Ogallala aquifer. Let’s put that dilemma in simple terms.
- The advent of center pivot irrigation created an agricultural revolution. However, remember at most about 20% of acreage is irrigated. This allowed for large scale, high yielding corn production.
- Millions of bushels of corn allowed for the development of a large scale feedlot and meatpacking industry. This allowed cities such as Dodge and Garden City to thrive.
- Even with the corn we produce, it isn’t typically enough to supply feedlots.
- Agriculture is the single largest consumptive user of groundwater. Other uses are minor in comparison. This usage includes more than simply watering crops. Cities, think Wichita and Hays are laying claim to their fair share of groundwater for human and industrial use.
- The overall dilemma is what to do to manage this challenge while maintaining the agricultural industry and population.
So what can be done? This has been a topic of much discussion, especially during the worst of the drought. Without taking sides, what is possible if not practical? This doesn’t include what is already underway legislatively such as the five-year total usage.
- Certain areas such as Stafford County, could likely be managed to allow sustainable irrigation due to various geologic factors. That however, doesn’t mean business as usual.
- Some areas have already reached the point where depletion has resulted in the end of center pivot irrigation. This has resulted in the return of dryland acreage.
- Where overhead irrigation is still practical but groundwater levels are in steep decline, use the most efficient irrigation systems possible. Have the government cost share switching over to subsurface drip irrigation and/or to have irrigated land retired.
- Increased research and development by the public and private sector on improving the water usage of current crops and examining potential new crops. Especially those crops as they could relate to the feedlot industry.
- Increase research on alternatives to corn for feedlot operations.
- Retire farmland in the most critical areas back to native grasses and grasses adapted to the region. Use this land for grazing and increase the percentage of beef produced using forage.
- Continue to increase the efficiency of beef production and the water use efficiency of all phases of agricultural production.
- For residential areas, provide incentives for homeowners to increase water use efficiency in all phases of domestic water use. For example, more water efficient toilets and showers. Mandate and help homeowners move away from high water use lawns.
- This has been saved for last. Build a pipeline from the eastern U.S., likely from Lake Michigan to Kansas and then a distribution system to Western Kansas. The cost is estimated in the billions of dollars. It will cost producers money, a lot of money to use this water. Eastern states and Canada have grave concerns and legal claims to this water.
The real question is “Can the western half of the state cope with this dilemma?” The answer is of course yes. The challenge is how and what impacts it will have.