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What Happens to Corn During Early Season Drought

Categories: GROWING, CORN
FFigure 1. Corn leaf rolling as result of early drought stressigure 1. Corn leaf rolling as result of early drought stress

​​​​​​Compared to stress during pollination and grain fill, drought stress during the vegetative growth stages is generally less detrimental to yield. However, early drought stress can reduce yield because of its impact on plant growth and nutrient uptake.

Plant Growth
Leaf rolling occurs when turgor (water) pressure is lost in the leaf’s cells due to a lack of water (as shown in Figure 1). Leaf rolling conserves water by decreasing the surface area of the leaf exposed to sunlight and reducing transpiration. However, it also reduces photosynthesis, which can decrease plant growth and development, and as a result, can limit yield potential.

Root Growth
Soil moisture is essential for proper root growth. Early season drought can cause root tips to dry out and stop growing. Dry soils also cause brace roots to grow along the surface rather than penetrate the soils which leads to standability issues later in the season. The decrease in root growth limits the surface area available to collect nutrients and water from the soil. If moisture availability doesn’t improve, overall plant growth can also be compromised.
Poor root development and brace roots growing on the soil surface due to dry soil conditions.​​​​​​​

Nutrient Uptake
Dry soils may temporarily reduce available nutrients in the soil solution. Potassium (K) is vital to several plant functions, including water and nutrient uptake and stalk health. Dry soils can exacerbate the plant’s inability to uptake potassium due to reduced physical mobility and root interception of K. Deficiency symptoms start on the plant’s older leaves and can be identified by yellowing or firing on the leaf margins. Generally, drought will have less of an impact where K availability is adequate in the soil. Adequate K levels within the plant will also help to increase drought tolerance by supporting water uptake.​​​​​​​

Potassium deficiency in corn.​​​​​​

Effect on Yield
Extended early season drought can limit yield potential because of its impact on the plant’s development processes. The number of kernel rows on the ear are determined around the V6 growth stage, while potential number of kernels are determined from approximately the V7 growth stage up until one week before silk emergence. As a result, extended periods of early drought can reduce the maximum number of potential kernel formation leading to potential yield reduction. Corn leaves that are rolled up for a couple of days likely won’t see significant yield loss, but corn that’s rolled up for the majority of a two-week period may see yield losses up to 20%. Extended early season drought under extremely dry conditions can even lead to plant death. Yield reduction varies greatly depending on the severity and duration of the stress.

Figure 2. Corn water demand by growth stage.

Overall, yield loss from early season stress can occur, although as Figure 2 illustrates, the highest demand for water doesn’t occur until the plant begins to shift from vegetative growth stages to reproductive growth stages. Drought stress at or near pollination will result in the most severe losses from lack of water availability.

Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

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