Jay Norton, a soils specialist with he University of Wyoming Cooperative Extenstion Service says that farmers with unharvested sugar beets from 2009 have to veer away from standard operations to deal with possible nutrient shortages, crop disease issues and blockage of irrigation systems caused by leaving much of the biggest Big Horn Basin sugar beet crop ever in the ground.

What looked to be one of the best years ever for sugar beet farmers quickly turned into a big headache last fall when a combination of an early freeze and yields that overwhelmed processing capacity prevented harvest of more than 30 percent of the crop in the Big Horn Basin.

The result is that each acre of unharvested beets has more than 10,000 pounds of sugar in the soil. This will have a huge impact on soil fertility as populations of microscopic organisms – soil microbes – expand to decompose the beets. The abundant, sugar-derived energy source creates a shortage of other nutrients, especially nitrogen, which the microbes rapidly take up and make unavailable to crops. Later in the season, when the sugar source runs out, the microbes themselves will decompose and release available nitrogen.

So, farmers can expect shortages of nitrogen and possibly phosphorus early in the season followed by an increase later; exactly the opposite of what is needed to produce malting barley, the most common crop alternated with sugar beet.

Fortunately, the situation last fall is a fairly rare occurrence. Unfortunately, this means there is little research-based information about the best way to manage the unharvested beet ground. Fact sheets from sugar beet production areas in the Midwest and Canada provide some experience-based information we can interpret to our region.

Tillage

Chiseling and disking to chop up the beets in the fall would have been a good idea, but most farmers held out hope for harvesting until it was too late for tillage. At this point, most information suggests that beets would be best left in the ground. Although farmers with furrow-irrigated ground don’t have the option of no-till, they should try to limit deep tillage that will dig the beets out. Pulling them to the surface will slow decomposition and plug furrows and ditches.

Soil Fertility

Remember, most of the fertilizer put on the sugar beets last spring is still in the soil because it wasn’t removed with the crop; it’s tied up in the decaying beets and in the microbes doing the decomposition. Microbes react to temperature and moisture in much the same way crops do so rapid microbial growth, decomposition and nutrient uptake will occur with the first warm temperatures. Then the microbial biomass will “turnover” and release available nutrients to crops during June and July.

According to recommendations from American Crystal Sugar Company, each ton of unharvested beets with green tops will tie up about 5 to 6 pounds of nitrogen per acre, and each ton with yellow tops will tie up about 2 pounds of nitrogen per acre. Some farmers were expecting 35- to 40-ton beets, so microbes will tie up from 70 to 240 pounds of nitrogen per acre as they decompose the unharvested roots.

Phosphorus and potassium needs may be less than normal for crops following unharvested sugar beets. Fields that typically test low for phosphorus may need extra phosphorous as a starter, but, since last year’s phosphorous application was not removed with harvested beets, it will be released as the beets decompose.

Crop Selection: Plant Beans

Information from the Midwestern U.S. and Canada recommends soybeans as the ideal crop to follow unharvested sugar beets. In the Big Horn Basin, dry beans have many of the same characteristics as soybeans and may be the best choice. Beans are planted relatively late, so they would miss part of the big nutrient grab during rapid decomposition of the sugar beets. They do not have large nitrogen requirements, so they shouldn’t require any extra fertilizer application. They will benefit from the release of nitrogen and phosphorus in mid-summer, but that release should come early enough to not delay maturity of dry beans.

Malting barley and other early-planted small grains will suffer from nitrogen shortage because they require most of their nitrogen early in the season. American Crystal Sugar Company recommends adding 25 to 30 pounds of extra nitrogen per acre to maintain yields, but, if temperatures warm early this spring, decomposition may tie up even the added nitrogen for a while. Also, even if yields can be maintained by adding nitrogen early, the quality of malting barley will suffer from nitrogen becoming available later in the season and increasing protein content.

Corn is also planted early and requires adequate nitrogen early in the season, so it will be affected by decomposing beets. Recommendations are for an extra 30 to 50 pounds per acre of nitrogen. Corn would benefit from and would take up much of the late-season nitrogen released during microbial biomass turnover.

Sunflower may be a good choice because it is planted later so it may not suffer yield loss because of tied up nitrogen, although it may require some extra nitrogen to maximize yield. Its deep roots will take up and recycle nutrients released later in the season.

Alfalfa and clover could also be good choices because of low nitrogen requirements and deep roots that would capture and utilize nutrients released later in the season. Grass, on the other hand, would be difficult to establish in the low-nitrogen conditions early in the growing season.

Other Considerations

Some sugar beets may survive the winter and bolt this season if allowed. With the prevalence of Roundup Ready beets, Roundup or other glyphosate-based herbicides will not be helpful for management of resprouting beets. Shallow pre-plant tillage may help control resprouting beets. If a row crop such as beans, corn or sunflower is planted, in-crop cultivation will also help. Many herbicides typically used for these crops will also help suppress resprouting beets. If resprouting beets are a problem this spring, contact Abdel Mesbah, director of the Powell Research and Extension Center, or Andrew Kniss, assistant professor in the Department of Plant Sciences at the University of Wyoming College of Agriculture and Natural Resources, for crop-specific herbicide recommendations. Mesbah can be reached at (307) 754-2223 or sabah@uwyo.edu, and Kniss can be contacted at (307) 766-3949 or akniss@uwyo.edu.

Diseases like rhizoctonia could be an issue with all the microbial activity occurring but would be difficult to predict. Farmers should closely watch growth of crops following unharvested beets for early detection of disease issues.

If the beets survive the winter more or less intact, digging them up for use as animal feed may be profitable. According to an article from the Ontario Ministry of Agriculture, whole beets can be fed to livestock. They have similar energy and slightly less protein than corn or cob meal. The beets can be stored easily in piles in cold temperatures but should be used before warmer days in March. An article from North Dakota describes how sugar beets can be ensiled to create quality feed with slightly less energy than corn or barley silage. Beets should be run through a tub grinder, forage harvester or even run over on the ground to break them up and then mixed with dry hay or straw at 5 tons of chopped beets to 1 ton of hay or straw to get a moisture content of about 60-70 percent. 

We plan to track nutrient availability and crop performance in some unharvested sugar beet fields under several different management approaches this season. Hopefully, this will give us some information tailored to the Big Horn Basin next time farmers have to leave sugar beets unharvested.
 

Jay Norton is the soils specialist with the University of Wyoming Cooperative Extension Service and an assistant professor in the Department of Renewable Resources in the UW College of Agriculture and Natural Resources. He can be contacted at (307) 766-5082 or Jnorton4@uwyo.edu.

Source: UW-Posted by Russell Nemetz