GIBBON, Minn. – Author Charlie Swindoll said that life is 10 percent what happens to us and 90 percent how we react. When asked if they had 90 percent control over crop yield, farmers at the Beck’s field day event answered with a resounding “no.”
“We don't have 90 percent control over yield, but I will argue this point, yield is 50 percent environment and 50 percent how we react to it,” said Eric Wilson, field agronomist with Beck’s, speaking at the field day about mitigating crop stress.
This was the second year for the Beck’s field day in Gibbon at the AgRevival research station. Throughout the day, attendees could ride through the research test plots, reviewing the many different Practical Farm Research (PFR) tests that Beck’s has been working on in conjunction with AgRevival.
Attendees could also listen to different educational presenters, including Scott Beck, president of Beck’s Hybrids, as well as Wilson’s talk on crop stress.
“Any given year, we have two types of crop stressors. The first one I'm going to mention is biotic, those are your living things,” said Wilson. “Weeds, insects, disease, nematodes, things that have a heartbeat and are living, those are biotic stress factors.”
Biotic stressors tend to be things growers can actively control. There are traits, chemicals and treatments to mitigate and stop weeds, insects and disease pressures.
The second type of stress crops experience is abiotic or from non-living things.
“Those are the things that we have seemingly less control over, environment, temperature, light, water, fertilizer availability, so on and so forth,” he said. “Those big three are what I'm going to focus on, water, nutrition and light.”
Water is crucial to every aspect of a plant’s growth, development and function. It takes 25 gallons of water to grow one pound of corn biomass.
“Nutrient uptake, re-mobilization, protein synthesis, enzyme activation – everything involves water,” he said. “As farmers, we’re a little bit ‘Goldilocks’ about it, not too much, not too little, we want it just right, for good reason.”
Too much water and plants don’t develop roots. The soils become saturated, forcing out oxygen and the roots cannot breathe or take up nutrients properly.
Too little water favors root growth, to a point. In drought conditions, all the plant’s energy is pushed towards growing roots to find water. Eventually, the plant’s leaves start to shrivel or in the case of soybean, turn upside down, to conserve water. Plant growth and development is hindered.
When the leaves shrivel or turn over, photosynthesis slows down or stops.
“Photosynthesis is maximized at higher temperatures – about 80-85 degrees,” Wilson said. “When we get it 86 and above, we've got to spend more water to maintain a cooler cellular temperature.”
Corn and soybean plants go about photosynthesis in two very different ways, with the corn plant being more efficient.
Soybeans operate C3 photosynthesis pathway and corn have a C4 pathway. The major difference is that corn plants can take in carbon dioxide and store it in bundle sheath cells. This allows the plant to close stomates during high temperatures or dry conditions, conserving water.
Soybeans cannot store CO2 and must keep their stomates open to constantly bring in more to maintain photosynthesis.
When the stomates are open, the plant is more likely to lose water.
In either case, too much or too little water, the plants cannot take up nutrients. Even if all the fertility is there and available, if there is no water, the roots cannot take it in. If there is too much water, the environment lacks the needed oxygen to allow for nutrients to be absorbed and the plants begin to look nutrient deficient.
“How about light stress? Do you think crops can become light stressed?” asked Wilson. “I would probably say ‘limited’ is actually a better term. Say, you have a cloudy day, it's not necessarily hurting anything, but we're just not being as productive as we could be.”
Evidence suggests that soybeans can become more light stressed than corn. Research done in the 1930s and 1940s used sheet metal to increase the amount of sunlight being shown on plants.
Corn plants continued to improve as more light was provided while soybean plants maximized production at about 50 percent light intensity and then started to slow down.
This is why early planting, row spacing, and population are crucial to soybeans. Physiologically speaking, soybeans are not as efficient as corn when it comes to water and light usage.
“We're actually limited on the length of our growing season for soybeans because they're not as efficient. It’s important to get them out early with good canopy closure. We want to harvest as much light as we possibly can,” he said.
In the end, many of the decisions made by growers around water, nutrition and light become situationally important. Depending on the year and the weather, certain inputs may pay off better than others.
“We can be proactive, but we have to react, especially in years when the environmental stress is very high,” said Wilson. “The little things we do matter, and those management decisions you make in-season matter and we have just as much control as the environment.”