The experts are saying we are in La Niña, but coming out of the wettest April in Oklahoma’s history, it does not seem like it right now. But as we all know, those involved in agriculture, the droughts are just around the corner, the rainfall will most likely stop, and soon we will be praying for rain. So, we should ask ourselves how well we can capture and store the water we receive when it rains for our trees and crops later in the year when the watering spout turns off.

Many of us may not consider how our management can impact the water we capture and store in the soil. However, management in the orchard can have a significant influence on the success we have with water management. This is true in both irrigated and dryland orchards. As managers, we must consider the water cycle in our soil/orchards. The water cycle is one of the ecosystem processes that, as managers, we have influence over, and to be successful, we should understand it and strive to improve it. The water cycle moves on, above, and through the soil profile. The water cycle involves precipitation (rainfall or irrigation), condensation (from the plants), evaporation (from surface water bodies and soil), transpiration (from the plants), runoff, and infiltration.

As managers, we should ask ourselves,

One of the best ways to answer this question is to look at the surface of our orchards after an irrigation or rainfall event. Does the water infiltrate into the soil, pond on the surface, or run off the orchard? If the water is ponding or running off the orchard, we are losing this water. Ideally, we would like all the water on our property to infiltrate the soil profile. High organic matter (OM) and higher water holding capacity will help keep this moisture in the soil so the trees can use it longer in the season.

Additionally, this captured water can percolate deeper into the soil, helping to recharge the aquifer (helping with spring flow and streams). In the central Great Plains region, it is estimated that our soil only captures 20-40% of the rainfall that falls when it rains. We call this ‘effective rainfall’. That means that when we get a 2-inch rainfall or apply a 2-inch irrigation event, we only capture 0.4 – 0.8 inch of that water. To increase water infiltration, we must have a functional water cycle.

  The answer to improving the water cycle is following the soil health principles. One of the easiest and cheapest ways to improve the water cycle is to ensure the soil is protected and covered (with forage/grasses). When the soil is left bare, the soil temperature increases, and typically, the soil surface will crust over. Crusted soil will restrict water from permeating it and result in runoff. When the soil is covered, there is less water loss to evaporation, the soil is kept cooler, and water infiltration is increased. With actively growing forages/grasses left taller and growing, greater root systems and deeper penetration below ground are ensured, increasing water infiltration. All these deep roots create channels for the water to move into and through the soil. If you have diverse forage species, diverse root structures (deep, short, taproots, large, small, etc.) help move the water into the soil. To have a good root structure, plants must be allowed to mature and photosynthesize, pumping carbohydrates into the root system that increases root size. As plants produce more carbohydrates, some of these are released from the roots as exudates that feed the microbes in the soil. To achieve good channels in the soil and high amounts of exudates from the roots, the plants must be fully photosynthesizing (allowed to grow and mature). Therefore, managing your forage is essential.

When managing forage/grass, allowing it to grow and mature is important. I know this goes against traditional thoughts on orchard floor management, keeping the orchard floor mowed short. Considering the water cycle, allowing the forage/grasses to grow and keeping them tall as long as possible is better. Taller grasses use less water than short grasses. Taller forage/grass keeps the soil cooler, resulting in less evaporation from the soil. Some research has shown that shorter grasses have as much as 87% more evaporation than taller grasses. Keeping that in mind, if we allow the vegetation in our orchards to grow and not mow as often, we reduce the amount of water lost to evaporation. Plus, with taller forage/grasses, we can infiltrate more water into the soil. Taller grass, when mowed, can increase organic matter in the soil. Having higher organic matter will result in greater water holding capacity. An increase of 1% in organic matter will hold an additional 20,000 gallons of water per acre. Therefore, if we could increase our organic matter to greater than 3% or 4%, that is over 2-to-3-acre inches of water available to your crop.

As a manager, we can improve the water cycle within our orchard. An improved water cycle can significantly impact production and tree growth and save you money, especially if you irrigate your orchard. If you increase the effective rainfall, the precipitation that infiltrates the soil, by 50% or more on your property and double your organic matter, how much more water would you have for your plants? If you are irrigating, how much money would you save by not having to irrigate as much?

The water cycle and the energy flow (power of the sunlight that drives photosynthesis) are the most critical ecosystem processes in our orchards, because they directly impact the nutrient cycle. You must have a functioning water cycle to increase the energy flow (more leaves to capture the sunlight). It takes water to grow plants, and plants (root systems) to improve water infiltration. Over the years working in pecans, I have observed numerous orchards with a broken water cycle. Going into an orchard with a good functional water cycle is rare. But we can continually improve the water cycle on our property.