University of Wyoming research explores seeding ratios for grass and alfalfaWritten by Natasha Wheeler
Basin – “If we look at the hay crop, we see it contributes $390 billion to the Wyoming economy,” noted Dhruba Dhakal, a recent PhD student working with Assistant Professor of Forage Agroecology Anowar Islam at the University of Wyoming.
Winter wheat, the second largest crop in the state, contributes about $50 million to the state’s economy.
“From this data, we can say that hay is the most important crop in Wyoming,” stated Dhakal. “Also, crops harvested as hay are one of the important components of cattle farming, and cattle farming contributes to more than 50 percent of Wyoming’s agricultural economics.”
Although many studies have explored grass and legume mixtures that may be grown for hay, producers are still challenged by the stem persistence of legumes.
“Because grass may be more competitive, if we continuously grow a grass-legume mixture, grass might choke out that legume. After three or four years, we might have only grass,” he explained.
Over the last several years, Dhakal has been studying grass-legume mixtures, looking for the best seeding ratio.
“The major objective of this research is to find out, and recommend to the forage grower, the optimum ratio of grass to legume, especially in regard to seeding proportions in the state of Wyoming,” he said.
The first objective of the study was to compare forage quality in grass-legume mixtures with different seeding ratios. The second objective investigated stem persistence, and the third objective was to determine which mixture was the most economical for the grower.
“For the first and second objectives, we conducted a field experiment using two perennial, cool-season grasses, meadow brome grass and orchard grass, and one legume, which was alfalfa,” Dhakal explained.
Nitrogen fertilizer application was also a variable in the research.
“We had in total, 16 treatments, in two locations in Wyoming – Lingle and Laramie,” he continued.
In Lingle, mixes were planted in the fall on Sept. 20, as well as in the spring on May 14. In Laramie, mixes were planted only in the spring, also on May 14.
To collect data, Dhakal commented, “We harvested our crops three to four times each year. After the clipping, we separated the grass component and alfalfa component and put them in different bags.”
Sample weights were measured directly after they were cut and also after they had been dried, to obtain dry matter weight data. The dried samples were then ground and tested for various quality measures.
Looking at data from fall planting samples in Lingle, Dhakal remarked, “The 50/50 mixture of alfalfa and meadow brome grass had the highest dry matter yield within three years. It was followed by the mixture of 50/50 alfalfa and orchard grass.”
Other samples contained different seeding ratios, including plots of 100 percent grass grown with and without applied nitrogen fertilizer.
“If we mix legumes into a 50/50 mixture, we can create an increase in dry matter weight compared to the 100 percent grass with nitrogen fertilizer as well as the 100 percent alfalfa,” he noted.
In spring planting samples from Lingle, the 50/50 mixture with orchard grass yielded the highest dry matter, and the 50/50 mixture with meadow brome grass yielded the second highest quantity. Similar results came from the Laramie data.
“From these findings, if we plant in the fall, I would prefer to plant meadow brome grass. If we are planting in the spring, we can plant either meadow brome grass or orchard grass,” stated Dhakal.
Data also showed that the 50/50 mixtures were beneficial for stem persistence, meaning that both grass and alfalfa were yielded from the crop mixture.
“Stem persistence was consistent over three years from the highest yielding mixture, which is the 50/50 mixture of alfalfa and meadow brome grass,” Dhakal noted.
Overall, he concluded that data for the first and second objectives of the study indicated a mixture of 50 percent alfalfa and 50 percent grass to be ideal.
“Our third objective was the effect on total economic return. From our 16 treatments, we selected five for this study,” Dhakal remarked.
The study included 100 percent alfalfa, 50/50 mixtures of alfalfa and meadow brome grass or orchard grass, and two mixtures of 100 percent grass, with and without added nitrogen fertilizer.
“We started the study in 2011 and finished in 2014,” he noted.
Each year, costs were evaluated based on inputs, and final yields were based on market data from the Nebraska Feed Guide and USDA.
“The highest net returns were obtained from the 50/50 mixture of alfalfa and meadow brome grass from fall planting and the 50/50 mixture of alfalfa and orchard grass from spring planting,” Dhakal stated.
In further data, the 50/50 mixtures also showed the most favorable results in regard to soil carbon, soil nitrogen and micro-biomass levels.
“From our four years of study, we can say that the 50/50 mixture may be more beneficial as compared to the nitrogen fertilized grass or alfalfa,” concluded Dhakal.
Dhruba Dhakal presented his research findings at Forage Field Day in Basin on June 11.