Jul 13, 2020, 10:00 AM
Corn is very susceptible to drought damage because the plant needs water for cell elongation and growth. Because corn cannot delay vegetative growth, there is a danger of yield loss from early drought conditions. Corn plants often roll their leaves to protect themselves from excessive moisture loss due to transpiration. Plants may roll their leaves in response to inadequate moisture, however, rolled leaves in the afternoon may not mean that corn is under drought stress. A key indicator of drought stress is when corn leaves begin to roll early in the morning and continue to stay rolled throughout the day.
Stage of Growth
Growth from emergence to V8 (eighth leaf fully emerged with a visible collar) determines the size that the plant will achieve and the size of the individual leaves. Dry weather during this period will reduce plant and leaf size. Minor reductions in leaf size will have little impact on yield while major reductions (all leaves removed from the plant) could reduce potential yields as much as 20 percent.
From V8 to V14, this is the period that determines ear size and the number of kernels set. Drought during this period will reduce ear size and potential yield.
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. As a result, it can limit yield potential.
Early season dry soils cause root tips to desiccate and stop growing. Dry soils also cause brace roots to grow along the surface rather than penetrate the soil 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.
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 K 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 help to increase drought tolerance by supporting water uptake.
Early season drought can limit yield potential because of its impact on the plant’s development processes. Extended periods of drought can result in kernel loss and yield reduction as the number of kernel rows on the ear are determined around the V7 growth stage up until one week before silk emergence.
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 percent. Yield reduction varies greatly depending on the severity and duration of the stress.