I’ve been asked to speak about water conservation at two conferences this winter, so there’s no doubt it’s a topic on many minds. I’ve always thought that our limited groundwater supply would be a driving force in the adoption of continuous no-till in our region on irrigated acres.
Surface water irrigation is a moving target, as the levels of surface water fluctuate with the snowfall in the mountains, and precipitation during the growing season. There is also a connection between groundwater levels and surface water flow, which intertwines the two resources.
It’s very important that we stabilize groundwater levels to help maintain surface water levels in the region.
The single most important management decision we can make to conserve our irrigation water resources is the adoption of conservation agriculture on irrigated acres.
I think the goal of every producer on irrigated acres should be to reduce irrigation pumping on ground and surface water to sustainable levels or zero depletion. It’s also critically important that agriculture stays profitable while reducing the consumption of our water resources.
There will be advances in irrigation technology and crop genetics that will allow for less irrigation pumping while still producing profitable crops. These advances will be adopted by producers as they become available and should help to lower agriculture’s demand on our water resources.
The most dramatic reduction in irrigation pumping will come when producers change their management practices to adopt conservation agriculture. I’m pretty confident we could reduce our irrigation pumping by a significant amount if conservation agriculture were adopted on the majority of irrigated acres.
What’s the Definition?
So what is conservation agriculture? I like to think of conservation agriculture as a systems approach to irrigation water management. No till production practices are a part of this systems approach, but not the total package.
Conservation agriculture involves minimum disturbance of the soil, adopting dynamic crop rotations, utilizing forage/or cover crops when possible, soil moisture monitoring, and an integrated nutrient management plan to protect water quality.
I’d like to take a look at these stages for adopting conservation agriculture and show you how we’ve tried to put the total package together on our farm in Nebraska. The adoption of these practices to conserve irrigation pumping and water on our farm has been, and will continue to be, an ongoing proposition. We began by adopting no till production practices on our irrigated acres, but conserving groundwater wasn’t on our radar at the time.
In my opinion, any serious discussion about water conservation has to start with the soil. If you are going to conserve irrigation water pumping, the first order of business is to make sure your soil is performing at a high level. The soil has to be able to infiltrate the water where it falls and have the capacity to store the water away from the soil surface as much as possible.
The ability of the soil to infiltrate water at a high rate is critical to water conservation. This process starts with minimum soil disturbance and leaving the previous crop’s residues attached and on the soil surface.
I’ve had producers ask me why tilling the top 3-6 inches of the soil is so harmful, and my response is that it’s the most important part of the soil profile because it’s the entryway for water infiltration. If water can’t penetrate this layer, it can’t be stored and simply runs off the field or moves to the low parts of the field.
This top layer of soil is also the home for the majority of the soil microbes, where most of the nutrient cycling takes place as microbes consume crop residue and each other. It’s critical to have as little disturbance as possible to this upper layer of soil during crop production.
Residue from the previous crop also provides a layer of protection, or armor, for the soil surface. Water infiltration through this top layer of soil is greatly improved if the soil surface is protected by residue.
Many of you have watched the NRCS water infiltration demonstrations showing the difference in infiltration and runoff as soil with residue on the surface is compared with and bare, tilled soil. The difference in how these soils perform is dramatic: The rate of water infiltration is exponentially higher where residue is left on the soil surface.
Any tillage done to the surface will also destroy the macro pores and soil aggregates present in undisturbed soil. These macro pores are formed by roots from previous crops or by earthworms and allow for rapid infiltration of water into the soil. They also allow the moisture to move deeper into the soil profile and away from the surface.
Residue left on the soil surface also greatly lowers the amount of soil moisture evaporation during the growing and irrigating season. The amount of open pan evaporation in our area is roughly four times higher than the amount of precipitation we receive.
Lowering soil-moisture evaporation is critical to water conservation. Studies have shown that crop residue can reduce the amount of soil moisture evaporation by 3-5 inches during the growing season. That is water stored in the soil and used by the crops rather than evaporating into the air.
Hold it Together
Minimal soil disturbance also allows for the formation of soil aggregates.
These aggregates in undisturbed soil create more pore space, which improves the water infiltration and water-holding capacity of the soil. Improved soil structure from these aggregates throughout the soil profile allow for water and air to move freely through the soil profile.
Think of the soil as a lung that allows air and water to move in and out of the soil profile. There has to be this exchange of water and air as the soil-moisture conditions change during the growing season. Water can’t move into the soil unless the air moves out and vise-versa.
Using no-till crop production practices we are better able to improve the performance of our soil. Improved soil aggregation, water infiltration, water holding capacity, and leaving the previous crop’s residues on the soil surface are critical to water conservation of our ground and surface water resources.
Next time in “Part 2” I’ll discuss what other steps can be taken on the farm to safeguard precious water resources.