Crop & Pest Report

Accessibility


| Share

Water Use in Corn and Late-season Drought Stress (08/16/18)

For much of this growing season conditions were favorable for corn growth and up until recently it looked like we were going to produce a record or near-record crop in North Dakota. Because of the lack of recent rainfall, however, corn is starting to be stressed.

Water Use in Corn and Late-season Drought Stress

For much of this growing season conditions were favorable for corn growth and up until recently it looked like we were going to produce a record or near-record crop in North Dakota. Because of the lack of recent rainfall, however, corn is starting to be stressed. Figure 1 shows the current water deficit levels for the corn crop in various parts of the state. Corn grown in red and orange colored zones very likely already are showing some symptoms of water stress. When water becomes limiting to plants the stomata close, reducing the availability of carbon dioxide within leaf, increasing the temperature of the leaf tissue, reducing photosynthesis, thereby slowing plant growth, though usually hastening crop development (meaning less biomass production and yield because of both a lower rate as well as a shorter duration of growth). The first symptoms of drought stress is leaf curling of the upper leaves. This will be followed by yellowing of lower leaves and firing of leaves along the edges. Green leaves can recover their productivity once stress has been alleviated, but desiccated leaves will not contribute to further growth.

ransom.1

The impact of drought on corn yield varies considerably depending on its timing, severity and duration. There is little impact of short periods of drought on corn growth during early vegetative stages while the greatest losses occur during pollination (Table 1). Most of the corn crop in North Dakota is probably in the milk to dough stages. Crops in these stages are somewhat less sensitive to drought than crops during pollination. Nevertheless, yield losses can be substantial if drought persists over any length of time. Newer hybrids may be somewhat more productive when stressed than indicated in the table.

Corn is a very water use efficient crop, but it is also a heavy water user. Depending on where in the state, estimated corn crop water use (using NDAWN data) for the past seven days was between 1.2 inches and 1.8 inches. Soils have the capacity to hold up to 10 inches of available moisture in the top four feet, though most will hold less (See Table 2). Unfortunately, most of the stored moisture has been depleted, as noted by the negative water balances exceeding what can be stored in the soil (Figure 1). Obviously additional rainfall is urgently needed if we are to realize the yield potential that was established earlier this growing season.

During grain filling, plants under stress are able to translocate carbohydrates stored in the stem and in leaf tissue to the grain. This helps increase grain yield beyond what might otherwise be expected. Because of the movement of carbohydrates from stalks, It is common for plants stressed during grain filling to have weak stalks. For drought stressed fields, this may be a consideration when deciding when to harvest and which fields to harvest first.

ransom.2 3 

 

 

Joel Ransom

Extension Agronomist for Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

USDA logo

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.