Insights
At a conference in North Dakota, meteorologist Daryl Ritchison described current weather patterns earlier this year to a crowd of farmers saying: “ weather is a non-linear, chaotic system. X does not equal Y in weather. No one thing causes another. (1)” Here in Pennsylvania, this rings true. Extreme rain events followed by the unforeseen dry spells and extreme heat days, only to follow a dragged out winter into the spring, has become normal here and disrupts farmer’s plans for planting, planned chemical passes, or foliar feeding and topdressing. This type of weather puts more pressure on crops and increasingly cuts into the grower’s bottom line. According to Dr. James Done, the Willis Research Fellow at the National Center for Atmospheric Research (NCAR), business losses in the mid-atlantic region due to weather increased threefold between 1985-2015(2).
Credit:James Done
At the time of writing this, planting 22’ across the country is just starting for some and wrapping up for others. In the midwest, some areas were hit with extreme drought. Others, with too much rain and hail. On top of this, the northern part of the midwest experienced a nasty series of tornadoes. Fortunately for Pennsylvania farmers, cooler than normal conditions have been the main restraint to getting in the field. Even so, some experts and growers in the mid-atlantic region are very concerned with the effect weather is currently having and going to have on crop production in the future. Researchers with the Penn State Extension released a report detailing the effect increased temperatures could have on corn cropping processes in the area(3). They suggest that by 2050 farmers in the mid-atlantic region will have to adapt new processes such as irrigation than their southern and western peers have used for years. This would expose corn crops here to a new level of stress.
You can pinpoint the main stages when yield potential is determined in corn to 4 periods in the growing cycle. The first stage where yield potential is impacted occurs during crop emergence. The success or failure of your crop to germinate and start its life cycle will determine the number of plants available to hold ears. About a third way through the vegetative stages, all parts of the corn plant are developed and prepared to produce grain. The plant at this stage is known as being a ready “factory.” Here at v6-v10, the number of rows per ear are locked in. The next big stage where yield is determined is at the end of vegetative growth, around V18. Here the number of kernels per ear and overall ear size is determined. The demands for plant nutrients and water from the crop is at its max at this time. By the start of the reproductive stages at R1, the crop’s potential grain weight per ear is set(4).
Cold, wet planting conditions
The old adage goes “you only have 100% yield potential with the seed sitting in the bag” or something like that. As soon as a new crop is planted, it can face pressure from cold and wet soils. If conditions are on the wetter side, this opens up potential issues with root blight or pests. If this doesn’t kill the plant outright, these issues will slow your crop growth creating more chances for your crop to face yield reducing stressors over a longer growing period. Corn expert Bob Nielsen of Purdue University reminds farmers that large daily swings in temperature can impact emergence as much as overall cold soils(5). Even if your crop is only slowed down, you can see yield loss with uneven emergence. Illinois extension researchers found corn delayed by 1 week can reduce yields by 10%.
Flooding and high water saturation
As your crop gets past emergence, too much water or wetness can create huge issues for yield potential. Flooding and ponding will have a bigger impact on corn earlier on in the vegetative stages then later on. Standing water in the field is problematic for multiple reasons. First, it can directly damage the physiology of a corn plant in the vegetative stage. Even if the corn plant makes it through without direct physical damage, potential nitrogen loss can lower yields. Iowa State researchers tested the impact of corn temporarily flooded at V6 with high and low soil nitrogen rates. The corn with high levels of soil nitrogen experienced a 6-8% yield loss. Corn grown in the low nitrogen soil had a 15-30% yield loss(6). Ohio State research suggests knee-high corn can survive for about four days with ponding. Yield losses of 10% begin around 48 hours into those conditions(7).
Drought
Drought stress is a concern throughout the lifecycle of your corn crop. Bob Nielson breaks down the ways drought impacts yield potential in early corn crops: “So, potential grain yield reduction due to early season dryness can result from (1) outright loss of plant population due to death, (2) loss of potential kernel numbers before pollination (i.e., ovule formation), and/or (3) & (4) loss of surviving kernels after pollination (i.e., abortion of young kernels) or decreased kernel weight during grain fill due to smaller plants (smaller “factories”) and inadequate photosynthetic “output”(8).” Later on, drought stress really affects your corn crop as reproduction begins and the plants start to silk. On average, growers can expect a daily yield loss average of 6.8% per day of drought stress during pollination(9).
Wind and Hail
Stress from wind is most likely to occur in the late vegetative stages when the crop is tall but still lacks deep brace roots for support. However, this does not mean yield will be impacted very much. Iowa State suggests a loss of 2-6%. When the crop is more mature, especially
around those reproductive stages, the impact to yield is higher. During those stages, Iowa state estimates yield losses of up to 30%(10). A lot of factors go into the potential for lodging other than wind. These include high plant population, soil moisture extremes, nutrient deficiencies and imbalances, insect pressure, poor planting conditions, and hybrid susceptibility(11).
Corn crops are fortunately resilient to hail damage early on(12). The growing point of a corn plant remains underground until that V6 stage around sidedressing, so any damage to the early leaves or stem will not impact yield much. Moving forward in development, you need to consider four areas of damage: yield loss from stand reduction, from defoliation, from direct ear damage, and from bruising or stalk damage. Most researchers suggest losses are greater later on in development. After V10, it is estimated that a 1:1 ratio exists for stand losses and yield losses(13).
Good planting practices
The faster your crop is up and out of the ground, the shorter those plants are exposed to the environment before grain is in your bin or silage stored. The stronger and more resilient your plants, the more pressure they can take before cutting into yield. Using best practices that will give your early crops a strong, healthy start goes a long way. This begins at planting. Making sure you are at a good depth, have good seed-to-soil contact, and watching for compaction will go a long way. This may mean finding ways to manage
residue. Adding in-furrow products and starters is also a great way to give yourself an insurance policy against your planting conditions, especially if things get colder or wetter. Remember to use a seed safe product when looking to put fertilizer in-furrow. Choosing a hybrid that works on your ground and the conditions you grow in is always helpful too.
Work on drainage
Corn guru Bob Nielson, who was quoted earlier in this article, continues to provide wisdom in a quote given to agriculture.com back in 2012: “Young corn plants do not like soggy soils, and nobody seems to be working on corn hybrids that do.(14)” Anything that is going to help your soil manage extreme rains and ponding will go on to reduce water stress on your corn. This means reducing your tillage and building a good residue cover if you are still running conventional methods. Incorporating cover crops can help store water over longer periods of time that can help with drought stress later on. As you build up your soil structure and reduce erosion, it will handle the environment better. It is also important to recognize when you have fields that are more susceptible to flooding and ponding and take steps to incorporate drainage into them.
Scout your crops
Walking your crops frequently to check how they are doing during those sensitive growing stages where yield is determined is a way to get ahead of potential issues in the works. With excess wetness, you have more pressure from insects and diseases. This is where foliar fungicides can pay off if the issue is caught with enough time to do a chemical pass.
What am I doing to adapt to new, disruptive weather conditions?
How am I prepared to protect my crop through sensitive growing stages?
How can I strengthen my crops early on to fight stress later?
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