Assessing An Alfalfa Stand - Is It A Keeper?

Potential alfalfa winterkill is a good reason to walk your hay fields this spring to assess stand density and winter survival. It is important to identify winterkill problems early so that management decisions can be made.

Alfalfa winterkill can be caused by warm and cloudy fall weather, cold winter weather without adequate snow cover, flooding, persistent ice sheeting, heaving, and frequent freeze-thaw cycles. Contributing factors that can be influenced by management include the age of the stand, fertility, variety differences in fall dormancy and winter hardiness, and cutting during the critical fall harvest period.

Fall is a better time to evaluate health of alfalfa stands because it allows more lead time for spraying and planting. Obviously the impact of winter can't be determined until spring, but stands that look unhealthy in the fall don't usually improve.

Future yield potential can be estimated by looking at plants or stems per square foot, but the health of crowns and roots is extremely important. Stem counts are more accurate than plant counts, but crowns can be counted earlier in the spring. Be prepared to replace an older stand if it has less 4 plants per square foot.

Dig several plants to determine the health of the crown and root. Healthy crowns are large, symmetrical and have many shoots. Cut a root open lengthwise. Healthy roots will have a white or creamy colour inside, and are firm and resistant to pealing when scratched with your thumb nail. Dying plants will have crown and root rots with discolouration, and a spongy texture.

Check for bud or new shoot vigor. Plants with broken taproots from heaving may green up but die later. Slightly heaved plants can survive but their longevity and productivity will be reduced.

When alfalfa is about 6 inches in height you can use stems per square foot as your density measure. Stem density of 55 per square foot has good yield potential. There may be some yield loss with stem counts between 40 and 50. Consider replacing the stand if there are less than 40 stems per square foot and the crown and root health is poor.

Other considerations include forage inventories and requirements, alternate forage options, how much grass is left in the stand, rotational requirements, and weed pressure.

For more detailed information check out "Alfalfa Stand Assessment", "Forages - Making The Most With What's Left" and other articles on the OMAF Forage website at www.omafra.gov.on.ca/english/crops/field/forages.html.

Related Links

• OMAF Forage website

| Top of Page |