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). As crop consultants, we must consider these processes and encourage their expression. This can be accomplished through proper nutrient management.
Certain key nutrients are intimately involved in plant-water relations. Last month’s article highlighted potassium and calcium. There are two other nutrients that 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 which can access a larger volume of soil water. That is why desert plants have such deep roots (Figure 1).
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.
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.