Field Day Focuses Micronutrients, Irrigation

Published online: Sep 11, 2017 News Spike Jordan

Sugarbeet growers are always looking to increase their maximum yields. However, heavy applications of fertilizers and poor timing of irrigation can negatively impact their net check.

The micronutrients needed by sugarbeets and when to apply them to get maximum yields, along with soil moisture sensor field demonstrations, were the topics of a mini-field day Sept. 6 at the University of Wyoming’s James C. Hageman Sustainable Agriculture Research and Extension Center near Lingle, Wyo.

UW Extension irrigation specialist Vivek Sharma, along with Dave Alexander, owner of Saugatuck, Mich.-based Agri-Science Technologies, presented on several projects currently being tested on the sugarbeet plots at the center.

The project is in collaboration with Stoller USA to study the effect of micronutrient application on sugarbeet production, Sharma said. Understanding the timely application of micronutrients to improve seedling vigor and root growth, push row closure by increasing leaf size, and reduce the nitrogen application that result in increasing sugar percentage and tonnage at the end of the season is critical.

In this study, the team has applied different combinations of micronutrients at different beet growth stages to understand their effect on sugarbeet production, Sharma said. Alexander said he is collaborating with the University of Wyoming and contributing to experiments at the Hageman Center, hoping to find similar results as in tests he has conducted in Michigan and other parts of the country.

“We want to support our knowledge base in these applications before we ask producers to spend a dime,” said Alexander. “At the end of the day, it’s going to be all determined by what the advantage is and what the economics behind it are. We want to figure out how the economics work first so that when we go to the growers, we have something that’s real.”

The methodology is to avoid being seen as “snake oil salesman,” Alexander said.

“In today’s agriculture, you have to understand what you’re doing,” he said. “You not only have to understand the chemistry and the product, but you better know how to use it.”

And while no application will work 10 out of 10 times, Alexander said that consistency and knowledge help contribute to a greater mark of success.

“What happens when you apply nitrogen is that you increase the need for every nutrient, especially micronutrients,” Alexander said. “In particular, in high yield regimes, there are micronutrients we don’t hear about every day like cobalt, nickel and others that you would have to pull out your high school textbook to find out where it’s at.”

Alexander said different combinations of micronutrient applications can lead to greater nitrogen efficiency depending on the plant, and he is eager to see what works for sugar beets and what doesn’t.

So far, he said a combination of boron and molybdenum has been shown to help inhibit sugars from being held in the top of the plant, and moves as much of that sugar produced during the day down into the beet.

“Cold nights move sugars faster than warm nights,” Alexander said. “It’s because the absisic acid (ABA) ratchets up at nighttime, and the higher you can get that ABA, the more efficient you’re going to move all those sugars.”

Alexander said that molybdenum helps simulate a colder night in the plant by triggering an uptick of ABA.

“We don’t want to wait for a frost to occur before we top and harvest; we want it to do it during the day,” Alexander said. “However, we don’t want to be too aggressive, because if we shut the top down completely, we lose the ability to produce sugars, but if we can just add a little bit of influence, we should be able to produce sugars better.”

Another concern is late in the season, as the beet plant tries to grow more petioles, it’s devoting more energy to fully developing those leaves. That late in the game, those emerging leaves will not contribute to the overall plant. Instead, those newly formed leaves end up soaking up sugars and energy that should be going down to the beet.

Applications of plant growth regulators inhibit the growth of extra leaf petioles. Test applications, usually administered once a canopy is fully developed, have shown some degree of success; however, Alexander says the final data has not yet been collected.

Yet micronutrients are only one part of the formula, Sharma said. Knowing when to effectively schedule irrigation is crucial to efficient water management and to optimize the profitability of an irrigated operation.

“Based on the research conducted, we are confident that producers could maintain their crop yields even though irrigation levels we reduced by 20 to 25 percent for the growing season,” Sharma said. “We can produce the same amount of yield with less water, but the timing of the water is important.”

Excessive irrigation can not only leach nutrients to deeper layers but also restrict root growth. One of the important reasons not to over-water is to make sure that plants develop healthy, deep root systems early in the growing season. Most crops are very resilient to early water stress and have very little, if any, detrimental yield effects if water is a little short early in the growing season.

By making sure they only apply water based on the needs of the crop and the water storage capabilities of the soil, growers can encourage those roots to grow deep. And when the critical crop growth stages are reached (reproduction for most crops), there is a deep, healthy root system that can tap into the water stored in the lower part of the soil profile. Sharma also said when those nutrients leach into groundwater, it creates another set of environmental problems.

Sharma said sugarbeets under the right soil conditions can extend down from four to four and a half feet.

“With early excessive irrigation, the majority of the root system cannot reach to deeper layers, and the crop cannot take advantage of available water and nutrients in deeper layers,” said Sharma. “They only extract the water from those layers, meaning that only the nutrients in those layers are going to be accessible to the roots.”

Another problem with excessive irrigation is creation of an anaerobic environment in roots. Plant root systems need oxygen to remain healthy and function the way they are meant to. When water enters the soil, it does so by pushing air out. With excessive irrigation and saturated soils, roots grows in an anaerobic environment. This causes the metabolism of the entire plant to slow down, and water and nutrient uptake to decrease. Lower plant metabolism means less sugar production and eventually a lower yield.

It’s a delicate balance that takes timing, and through the effective use of moisture sensors and probes placed in a field, Sharma said using soil moisture sensors is one of the best and simplest ways to get feedback to help make improved water management decisions, to avoid over-saturation in a field (which drowns the root system and leaches out nutrients in the soil), or starving the plant of water to its permanent wilting point (at which point it will not grow anymore and die).

The soil water in the crop root zone between field capacity and permanent wilting point is available for plant uptake, Sharma said. At the start of the irrigating season, producers typically irrigate to field capacity, and the next irrigation will be made when the soil moisture deficit reaches a certain level, usually around 35 to 45 percent for many crops.

“We order the water on a weekly or two-week schedule and just irrigate,” Sharma said. “We don’t know if the water level has reached, or passed the trigger point.”

And that’s where monitoring the soil moisture content with sensors comes into play.

Different sensors are available. They vary in their working principle, installation data interpretation and price, Sharma said. All these sensors will give slightly different readings, but almost all will track moisture trend similarly. However, one cannot just rely on surface soil feel method or visual interoperation of soil for irrigation scheduling, due to the fact that evaporation of water from the first two to three inches of topsoil can give an inaccurate estimation of the actual moisture content available to the roots. The main objective of this study is to have producers adopt new technology, including soil moisture sensors, and show that these technologies result in better timing and amount of irrigation applied, water and energy saving in the process.

These sensors range from $600 to more expensive models, and some are capable for reading measurements of water levels every four inches along a four-foot tube. Technological advances are available that allow sensor data to be transmitted to computers or smartphones, thus allowing producers to see directly when and how much to irrigate.

“The idea is to see where the moisture level is and whether it has hit a trigger point or not,” said Sharma.

Sharma said they expect to begin harvesting the beets at the research center starting the week of Sept. 17, and that the study will continue into next year.

 

Source: Farm & Ranch