Producer Questions prior 2009 - Alfalfa

Alfalfa

(Producer Questions prior to 2009)

We did not have enough water to keep up crop irrigation and alfalfa so after the 3rd cutting we let the alfalfa go dormant. Should we irrigate it now or just let it go until spring?

Light irrigation (one-half inch per week) during the winterization period (generally mid-Sept to mid-Oct) is desirable to assure that there is sufficient moisture in the soil prior to winter to protect roots from drying out and dying. This low amount also will not overly stimulate aboveground growth, which would reduce winterizing activity. After plants are essentially dormant (after mid-Oct), continue light irrigation as needed until freeze up to maintain surface soil moisture or, if sub soils need moisture replenishment, irrigate with more water so a reserve supply will be available in the deeper parts of the soil profile for use next summer.

When testing alfalfa/orchard grass mixed hay would an RFQ test be more appropriate than the RFV test?

In years past we have used a forage testing system that measured two different types of fiber called NDF and ADF. We used NDF to estimate how much of the hay cows would eat and we used ADF to estimate how much energy they would get from that hay. Then we combined those values to give an overall estimate of forage quality that we called RFV, which stands for relative feed value.

We've known that ADF is not as accurate as we would like for estimating energy. Grass hay and corn silage in particular often had poor energy estimates using ADF. The problem was that we had to assume that all fiber had the same digestibility. We knew that was not true, but unfortunately, there was nothing available at an affordable cost that was any better. But now there is!

New, low-cost tests finally have been developed that do a very good job of measuring digestible NDF. Animal nutritionists and forage scientists have worked together with these tests to also revise the intake and energy estimates so that results from these tests will much more accurately predict how animals will truly perform. Likewise, a new overall estimate of forage quality was developed, which is called RFQ and stands for relative forage quality.

So when you test forages in the future, look for labs that offer relative forage quality. Your numbers will be more accurate.

What is cutoff date for last cutting of alfalfa? Field was planted 1 year ago and at present regrowth is slightly less than 1/2 of mature height.

The date you take your last harvest of alfalfa affects its winter survival and next spring's vigor. Alfalfa needs about six weeks of uninterrupted growth in the fall to become fully winterized. This winterizing generally begins about three weeks before the average date of first frost. Your last harvest can occur any time before winterizing begins or after the winterizing period is over with little worry about affecting stand life. But, harvest during winterizing can be risky.

During early fall, alfalfa plants detect that the amount of sunlight each day is getting less. This tells them that winter is coming so they change their growth process to help them winterize. If you cut your alfalfa during this winterizing period, the plant begins to regrow. This reduces its ability to winterize as fully as it would if it hadn't been cut. First and foremost is to make sure your alfalfa gets a chance to grow well for a lengthy period of time in late summer to build its root nutrient reserves. This means allow at least six weeks between your previous cutting and the cut that occurs during winterization. Second, thoughtfully select fields to be cut during winterization. Avoid old, thinning fields unless you plan to rotate that field to a different crop next year. Young, healthy alfalfa fields containing varieties with good winter survival ratings are most likely to perform well even after cutting during winterization. Lastly, consider waiting until mid-October after winterization is over or plants are nearly dormant. The stress of regrowth following an extra late cutting usually is very small.

By mid-October the growing season is pretty much complete. Many folks received some late season rain and some areas have had light frosts that left alfalfa plants pretty much unaffected. So, you might have a substantial, high quality alfalfa crop remaining in your field. Alfalfa that has had at least six weeks of regrowth in mid-October since the previous cutting will have developed adequate winter hardiness for all but the most severe winters. It also has begun to go dormant naturally because of shorter days and cooler temperatures. As a result, harvest will not reduce winter reserves, nor is it likely to jeopardize stand persistence.