Studying forages Forage Field Day looks inside latest crop research
Lingle – In its sixth year, Forage Field Day brought nearly 140 people to the James C. Hageman Sustainable Agriculture Research and Extension Center (SAREC) outside of Lingle to delve into some of the big questions surrounding forage production in Wyoming.
“Often, we call alfalfa the ‘Queen of Forages,’” said University of Wyoming Extension Forage Specialist Anowar Islam, who also said alfalfa is the most important forage crop for the state and the third most valuable in the U.S., contributing $9.3 billion to the economy across the country. “Alfalfa makes a significant contribution to our state economy, with more than $216 million coming from alfalfa.”
However, Islam also noted these numbers are declining, despite high production, quality and economic return.
“We have seen a declining trend in alfalfa yield over the last two decades,” he said, hypothesizing that a decrease in available potassium is a primary contributor to this phenomenon. “From 1920, we saw an increase in yield until 1990. After that, yields flattened out.”
Islam said many factors could impact yield in alfalfa, ranging from irrigation to frequency of cutting, crop genetics and more, but one factor of particular interest that he addressed in a recent study was the soil fertility.
Potassium importance
“Alfalfa has a higher requirement of potassium for high yield, quality and stand persistence,” explained Islam, “and alfalfa takes a huge amount of nutrients, including potassium, from soils each year.”
Islam explained one ton of alfalfa can take 50 to 62 pounds of potassium from each acre of soil.
“When we see yields of six tons per acre, the crop can take out 300 to 372 tons of potassium per acre per year,” he said. “If we don’t do something to replenish our soils, there will be declining yield.”
In Wyoming, potassium deficiencies aren’t commonly seen, but Islam said, “If we don’t pay attention to this now, we may see a deficiency in the near future.”
Symptoms of potassium deficiencies include leaves that begin to turn yellow, which causes a loss of yield, reduced yield and decreased stand persistence.
“We want to develop a potassium fertility management program that improves alfalfa production and quality, while also improving the persistence of alfalfa stands,” Islam explained.
The study
Islam’s study, which was conducted with UW Graduate Student Michael Baidoo, was funded by a National Institute of Food and Agriculture (NIFA) Alfalfa and Forage Research Program Grant at SAREC.
“The same study was done at three locations because we don’t want to recommend something that only works at one location,” he said.
In the study, four rates of potassium – zero, 50, 100 and 150 pounds of K2O – were applied per acre.
“We also have two cultivars, Hi-Gest 360 and AFX 457,” Islam explained. “Hi-Gest 360 is a low lignin variety.”
He continued, “We are comparing two harvests. One harvest was a normal practice at late bud to early bloom, about 10 percent bloom. We did another harvest seven days after our normal harvest.”
Each treatment was repeated four times.
The crop was planted on Sept. 8, 2016 at a rate of 20 pounds per acre.
“Michael collected a lot of data, and there’s a lot of productivity data available,” said Islam.
From their initial study, Islam noted numerous data points were collected to analyze the productivity of both low-lignin and conventional alfalfa varieties.
“We have four cuts, and with each cut, we also did a late cut seven days later,” Islam said.
Alfalfa was harvested on May 30, July 10, Aug 18 and Sept. 29, with late cuts on June 6, July 17, Aug. 25 and Oct. 6.”
Initial results
Initial results from the study provided a solid baseline to continue their work.
“One initial result is a significant difference between the late and early harvest,” Islam said. “When we look further at the production from each cut under each cultivar, a difference can be seen.”
The third and fourth cuts yielded more productivity, as expected, and there is a significant difference in the cuts, as well, said Islam.
The highest yields were found with the Hi-Gest 360 low-lignin alfalfa with potassium applied at a rate of 150 pounds per acre. Only slightly lower in production was the AFX 360 cultivar with potassium applied at a rate of 100 pounds per acre.
“This indicates there are some genetic differences in these plants,” Islam said. “However, we must remember that this is the first year of our study, and we can’t make conclusions based on only this.”
Further, when looking that the nutritive value of the forage, there is no difference in the crude protein, acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients or relative feed value for potassium applied at zero and 50 pounds per acre.
“However, it looks at 100 pound per acre potassium numerically produced higher quality alfalfa compared to others,” Islam said. “This is a good thing.”
The amount of potassium taken out of the soil is also significantly different.
“As we get higher rates of production, we see more potassium taken out of the soil,” Islam said.
Overview
Overall, no potassium deficiency symptoms were observed, but potassium application did affected forage yield.
“We see some differences in potassium uptake,” he said. “Potassium uptake was high, indicating we have to replenish potassium in the soil. If we don’t, eventually, we might lose productivity in the future.”
Islam emphasized, “We are not making any conclusions now because this was only our first year. This study will continue for several more years to validate these results.”
Islam’s study is also being replicated at Colorado State University by Joe Brummer and at Kansas State University by Doohong Min. Islam also recognized his team of researchers, including Dennis Ashilenje, Abdelaziz Nilahyane, Saugat Baskota, Sayantan Sarkus and Chandan Shilpakar, as well as Kevin Madden and the crew at SAREC and Alforex Seed.
Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to saige@wylr.net.
