Maximizing Water Use Efficiency with Nutrient Management
Lack of water is becoming one of the leading challenges in agriculture and food production. Water scarcity is expected to intensify as droughts become more frequent and severe. As water availability becomes more scarce, growers are required to meet production and yield demands with less and lower quality water.
Plants have evolved specific adaptations, both internally and externally, to take up, utilize, and conserve water. These adaptions are physiological processes that allow plants to maximize their own water use efficiency (WUE). Proper nutrient management can encourage the expression of these processes.
Certain key nutrients are intimately involved in plant-water relations. The two nutrients most discussed in this regard are potassium and calcium. Potassium is essential to the maintenance of the osmotic potential of tissues. By adjusting the potassium concentration, plants can move water into and out of cells, including guard cells surrounding stomata (Figure 1).
Potassium is also necessary for maintaining xylem flow and turgor-driven cell expansion. A deficiency will result in reduced cell size, leaf area, and overall plant turgor. Conversely, plants supplied with plant-available potassium at the correct time are more drought resistant. More potassium is needed for drought resistance than is needed for optimal yields. That requires a stronger rate of soil-applied potassium, and regular foliar applications of low-salt, plant-available potassium.
Calcium also plays a role in plant-water relations as it is essential to cell membrane stability. Calcium stabilizes membranes which avoids leakage of solutes from cells. For these reasons, during periods of drought and high heat, it is especially important to supply calcium. Foliar applications of a high-quality calcium product are most useful under conditions of low soil water because calcium will not move up the plant without water. These should be applied before and during periods of high heat to help water-stressed plants maintain functioning membranes.
The next two nutrients are less discussed in relation to plant-water management, but also very important. The best way plants can continue to thrive under drought conditions is with an extensive root system that can access a larger volume of soil water. That is why desert plants have such deep roots (Figure 2).
Phosphorus is the nutrient most closely linked to improved root growth. Soil applications of phosphorus before periods of water stress may help expand root access for a more resilient crop.
Although zinc is most known for its roles in chlorophyll formation and disease resistance, it also improves the activity of antioxidants. Zinc-related antioxidant enzymes protect membrane lipids from reactive oxygen species that can cause electrolyte leakage. Applications of zinc during drought can improve membrane stability via a reduction in oxidative stress.
Along with these key nutrients, agriculture technology has revealed certain naturally derived products which improve WUE in crops. Often referred to as biostimulants, they can be applied with nutrients to improve the plant’s ability to continue producing a desirable yield under low water conditions. Some of these products can actually increase the number of stomates and roots, two plant parts directly related to WUE.
Finally, humic acids are an additional useful tool for improving WUE. Unlike other biostimulants, these do not act inside the plant. Instead, they improve soil structure in the root zone, which improves water holding capacity.
In summary, nutrient management that maximizes water use efficiency should focus on four techniques:
- Strong applications of soil and foliar potassium throughout the season
- Foliar applications of calcium before and during periods of high heat
- Soil applications of phosphorus and zinc before drought conditions
- Applications of biostimulants and humic acids which target periods of water stress
Because of drought and water issues, the mandate for higher WUE will certainly continue. We will need to find ways to obtain the same high yields, but with far less water. By focusing on key nutrients at the right time, applied with proven biostimulants, we can improve crop WUE and achieve resiliency in a time of challenge.
FBSciences’ Product Recommendations
K-Surge™ will provide a safe and effective source of foliar potassium to improve water uptake and stomate function, which is essential to reducing heat and moisture stress. The addition of molybdenum and boron provides complementary and synergistic benefits to the utilization of potassium.
BounceBack® Foliar is a foliar heat stress reliever that provides highly available and mobile calcium, seaweed, and specific antioxidants. This reduces respiration rates, prevents cellular damage, delays senescence, and improves recovery during periods of heat stress, and can be tank-mixed with practically any foliar application and is compatible with most pesticides.
FBS Humate Plus™, FBSciences’ highly concentrated and efficient 19% humic acids product that improves water retention in the soil and water mobility within the plant, improving the water use efficiency of crops even in poor quality soils with low organic matter.
Transit Foliar® and Transit Soil® add another layer of protection from heat and drought and will help the plant through stress events and provide the energy necessary to maintain the seed, fruit, or nut crop. Transit Foliar will help reduce ethylene and lower leaves senescenceing. It also helps with rooting, increased chlorophyll, nutrient uptake, and movement.
Marschner, Horst. Marschner’s mineral nutrition of higher plants. Academic press, 2011.
Umair Hassan, Muhammad, et al. “The critical role of zinc in plants facing the drought stress.” Agriculture 10.9
(2020): 396.
Written by Steve Easterby, Agronomist, FBSciences Inc.
