March 16, 2007

Roundup Ready alfalfa must be planted by March 30, according to a recent judge's ruling in a suit brought by the Center for Food Safety and other parties regarding govenment approval of the GMO product.

Is this too early for Nebraska producers?

If you bought Roundup Ready alfalfa seed, likely at a higher price than traditional seed, you're probably concerned about being forced to plant it by March 30 and possibly putting your seed investment at risk. Consider your options: 1) plant Roundup Ready seed by March 30; 2) shift to conventional alfalfa and plant at a more typical time, or 3) forget planting alfalfa and switch to another crop.

My first reaction, which I admit is a little bit biased, is that you still should plant alfalfa. After all, you already decided that alfalfa was the best choice for your cropping system. Most weeds can be controlled with existing herbicides without using Roundup.

Potential Freeze Concerns

How likely, then, are you to suffer a stand failure by planting so early? Young alfalfa seedlings can tolerate temperatures as low as 15-20°F so early freezing usually isn't a problem. The danger of freezing actually is greater after alfalfa reaches the third or fourth trifoliate leaf stage when it's about 4 inches tall. At this stage, alfalfa begins to lose its cold tolerance and becomes susceptible to freezing. Early planted alfalfa can reach this growth stage by late April or early May, so late spring freezes sometimes injure early plantings.

Roundup Ready alfalfa sometimes may reach a susceptible growth stage a bit sooner than conventional alfalfa. While Roundup does not appear to injure tolerant plants, conventional alfalfa seedlings are injured slightly by most other herbicides usee to control seedling weeds. Thus, their development is delayed. But the injury also may make them more susceptible to cold-temperature injury, so it's difficult to know if freezing affects the different types of alfalfa differently. If you want to avoid any risk of freeze injury, plant non-Roundup Ready alfalfa in mid to late April.

Cold Soil, Plant Disease Concerns

A bigger problem than freeze damage for March-seeded alfalfa may be the length of time the seeds lie in the soil before germinating or emerging. Although alfalfa seeds can begin to germinate at temperatures as low as 35 degrees, seedling growth and development is slow until soil and air temperatures are quite a bit warmer. Such lengthy exposure to cold, damp soil increases the risk of seeds rotting or seedlings developing seedling diseases. This makes it especially important that the seed be pre-treated with a fungicide for protection from these diseases. Most Roundup Ready alfalfa seed is pre-treated. Also make sure that March-seeded alfalfa is planted on well-drained soils to minimize the risk of seedling diseases and don't till soils or plant into soils that are too wet. Otherwise you may cause soil compaction or even crusting that prevents your seedlings from emerging.

It may seem unfair to be forced to plant your alfalfa by March 30. Fortunately, most years it works fine.

Bruce Anderson
Extension Forage Specialist