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Potassium Application and Cutting Schedules Can Improve Alfalfa Productivity – Part IV

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By Anowar Islam, University of Wyoming Extension

In my last few articles, I discussed requirements of potassium in alfalfa, utilization of potassium in alfalfa for its growth and yield and factors such as soil and plant factors that affect potassium uptake in alfalfa. Today, I will wrap up my discussion on potassium and cutting schedules affecting potassium uptake and productivity of alfalfa.

As I discussed earlier, potassium is a major macronutrient and its requirement in alfalfa is very high. Potassium contributes to the productivity of alfalfa through enhancing plant metabolism and improving plant stress response and regulation of water loss. 

To realize complete benefits of potassium, some agronomic management practices such as cutting schedules should be considered seriously for alfalfa production systems.

Potassium and cutting schedules

The time of cut is crucial for maximizing yield, quality and stand longevity of alfalfa. This is especially important because of the trade-off between forage yield and quality of alfalfa. As a result, cutting times can influence uptake of potassium in alfalfa. 

In general, frequently cutting alfalfa at an early time lowers root reserve and vigor of the plant prior to the next cut. High quantities of potassium are absorbed by the plant to boost the metabolic processes and facilitate the translocation of photosynthates in its root and crown to accelerate growth until future cuts. 

On the other hand, in frequently late cutting times, the root reserve is reduced moderately in the plant with a decline in its vigor. Consequently, moderate quantities of potassium are absorbed by the plants to boost regrowth rate for satisfactory plant growth until the next cut.

These traits were observed in an ongoing study at the James C. Hageman Sustainable Agriculture Research and Extension Center near Lingle. The uptake of potassium by alfalfa has great impact on the productivity of alfalfa. There was a positive relationship between potassium uptake and alfalfa forage yield.

Results from the study suggest cutting schedules play a major role in determining the amount of potassium required by alfalfa to optimize growth and yields. 

Alfalfa fertilized with high amounts of potassium, 150 pounds potassium [K2O] per acre, at early cutting, late bud to the early 10 percent bloom stage, and with moderate amounts of potassium, 100 pounds potassium [K2O] per acre, at late cutting, seven to 10 days after early cut, schedules resulted in high potassium uptake by alfalfa. 

This trait eventually produced high forage yields of 6,350 versus 6,185 pounds per acre, in respective potassium application rates. This indicates delaying cut for a few days in alfalfa reduces the requirement of potassium for high forage yields and vice versa. 

The study will continue for a few more years. However, based on three years of observations, it is encouraged alfalfa growers should consider cutting schedules when making decisions on potassium fertilization for sustaining high yield in the longer term.

Please keep an eye on my future writings of updated results of potassium and cutting effects on alfalfa productivity.

Anowar Islam is a professor and the University of Wyoming Extension forage specialist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or mislam@uwyo.edu.

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