Above average rainfall, large number of fires throughout the region, increased temperatures, stress leading to leaf loss and pest pressure have all contributed to alfalfa quality issues in the western United States in 2016. Emily Glunk, Montana State University, explained how these issues impacted the 2016 alfalfa crop during Alfalfa U in Dodge City, Kansas.
“Normally you would expect the more rain the better,” Glunk said.
However, above average rainfall limited sunlight on the crop, and increased the amount of splashing onto the leaves. Fires also impeded sunlight, and increased ash content on the crop.
Glunk said increased shading leads to increased leaf drop, which, when combined with increased temperature, significantly reduced alfalfa quality and yield in 2016.
“Leaf drop is critical because with alfalfa about 70 percent of the nutrients are contained in the leaves,” Glunk said. “Protein, energy and readily digested carbohydrates are all going decrease as leaf drop increases.”
Impact of ash
Fires not only added to the decrease in sunlight, but increased the amount of ash on forage plants in 2016. According to Glunk, ash decreases overall forage quality. An increase in ash content above that which occurs naturally in the forage plant is likely from dirt contamination caused by soil splashing, mechanical harvesting or storage. Alfalfa contains about 8 percent ash naturally.
“On average, ash can take the place of nutrients such as energy, protein and even some of the vitamins on a 1:1 basis,” Glunk said. “If you increase ash by 0.1 percent, you are potentially decreasing digestible nutrients by 0.1 percent.”
Alfalfa containing a significantly higher ash content has reduced palatability. Alfalfa with an ash content of 8 percent and relative feed quality rating of 164 will produce 2,826 pounds of milk per ton, whereas alfalfa with 15 percent ash and a 147 RF will produce around 2,362 pounds of milk.
One way to decrease ash content is by paying attention to cutter bar height when harvesting alfalfa. Although cutting closer to the ground can increase yield, it can also decrease quality by increasing ash content. The optimum height for harvesting all forages is 2.5 to 3 inches. This height is the best trade off between yield and quality.
“The closer we get to the ground we lose about five points in relative feed value per inch because it is picking up more ash,” Glunk said.
The hay rake you use also impacts ash content. Rotary rakes and mergers were found to have the lowest ash potential. Rotary rakes and mergers are generally PTO or hydraulically powered.
Wheel rakes have the highest potential for increasing ash content in forage because they are ground-driven.
Doug Rich can be reached at 785-749-5304 or firstname.lastname@example.org.