Course: BFM 101 Biofuels Fundamentals

Breadcrumb Navigation

Reading »

Reading

(8/12)
(10/12)

(9/12)
CRP Conversion to Row Crop Production

Land Preparation – The land condition after ten or more years in CRP will be highly variable, depending on the vegetation present, the level of maintenance during the period, and the amount of animal activity in the area. Visual inspection of the land by walking or from an ATV will allow assessment of the land condition. Ideally, there will be few eroded spots, no gullies or animal burrows, and the plant stand will be uniform, with few invasive species or little woody vegetation (shrubs or cedars). This is unlikely, however; so preparation of the field for planting may take multiple tillage passes to correct these trouble spots. If the CRP land does not have a lot of rodent holes and other dangers to equipment, no tillage is recommended. If the land needs leveling or smoothing, it is best to disturb it as little as possible.

The pre-planting objectives are to kill or remove the growing vegetation, which usually includes either a warm season or cold season grass. Standing grass presents a formidable challenge to kill or remove. Timing of land preparation will have to follow NRCS guidelines so CRP vegetation is not killed or harvested in a way that violates the contract.

Killing Vegetation - Most research on conversion of CRP took place in the late 1990s before glyphosate-resistant crops were readily available. The use of glyphosate will make a no-till CRP conversion easier, and the lower cost of the chemical may make it more profitable than use of other land preparation strategies.

In order for glyphosate to kill grass, the grass must be actively growing. Depending on whether the prevailing grass is a warm or cool season species, different strategies may be needed. For warm season grasses, the ideal application time is in the summer preceding spring planting. Cool season grasses are easier to kill, and since they grow late into the fall and start growing early in the spring, they should be controlled with glyphosate in the fall, with a second application in spring if needed.

Removing Vegetation – Research on CRP in northeast Nebraska indicated there was 5 tons of mulch per acre in a brome CRP field. The mulch contained 110 lbs of nitrogen and 2700 lbs of carbon. The standing grass, when harvested for hay, yielded 1.0 ton/acre. When hayed, not much of the mulch was removed. Although mowing and removing the standing grass makes for easier fieldwork, yields were only affected slightly by the residue removal [1].

One option is to cut and hay the standing grass in mid-summer. After the grass grows back it can be sprayed with glyphosate herbicide. The following spring a row crop can be planted. Either corn or soybeans can be grown following CRP. Both of these crops can be planted no-till. In the past, no-till corn faced three challenges: weeds, seed soil contact, and nitrogen requirements. With glyphosate-resistant corn, the weed issue is not as critical

No-Till Planting Corn Following CRP -  Replacing CRP grass with a healthy corn stand can be problematic. A grass residue mulch provides a challenge to plant through, an uneven mulch will make uniform seed depth more difficult to achieve unless the mulch is moved away. Many producers have been farming no-till for an extended period of time compared to the late 1990s, therefore many producers are more experienced in setting planters to get the seed soil contact they need. This is not the situation to experiment with no-till.

Soil Nutrients – Since little plant material was removed during CRP, soil fertility levels for non-mobile phosphorous and potassium will be similar to levels at the beginning of the CRP period. A thorough soil-sampling program should be completed before planting the first crop. If any tillage will be done, an application of lime, phosphorus, and potassium would be beneficial. The main challenge will be with nitrogen management. The large amount of mulch will be high in carbon, and will take time to breakdown. In the breakdown process, nitrogen will be immobilized for a period of time.

Research in northeast Nebraska found that at least 50 lbs more nitrogen per acre was needed to achieve the most profitable yields for corn grown following CRP. This was because of two factors. First, the mulch on the soil needed nitrogen to mineralize, and therefore needed extra nitrogen to support this function. In addition, the University of Nebraska’s recommended procedure predicts nitrogen release from organic matter in the soil. Researchers conducting the studies found that the amount of nitrogen released was less than what would be released in fields that were in continuous row crop production. Reduced tillage may slow mineralization, but previous research could not document this, and so the nitrogen recommendations are the same regardless of tillage used to control CRP grasses [2].

Nitrogen Application in Former CRP Planted to Corn - The method of nitrogen application also needs to be considered. Applying a large quantity of urea-based fertilizer to the soil surface without incorporation might lead to a large amount of ammonia volatilization. Incorporation through tillage is not recommended. An alternative would be to use urea ammonium nitrate (UAN) fertilizer solution, and knife it in. The northeast Nebraska research found that the corn was nitrogen-deficient into midseason when the nitrogen was knifed in, presumably because it did not move laterally in the soil, and it took awhile for the roots to reach the nitrogen bands. It would be prudent to put selected amounts of nitrogen on with the planter, to the side of the row, thus combining broadcast and knifed-in applications.

Benefits of Soybeans as First Post-CRP Crop - Many problems associated with planting corn following CRP can be avoided by planting soybeans. Soybeans can be planted later in the season, which allows another spray of chemicals before the crop is up. This is less of a problem with the new GMO herbicide resistant varieties. Seed soil contact is not critical since soybeans are over-planted and soybeans compensate for skips better than corn. Since it will have been some time since soybeans were planted in the field, it may be wise to inoculate.  If inoculated correctly, there may be no need for nitrogen applications, and that will avoid concern about potential nitrogen losses to surface and groundwater.

Multiple Year Viewpoint – Conversion from CRP to row crops needs to be viewed over several years so that the long term benefits of the CRP are maintained, and that farming the land is profitable.

Resources provided by the eXtension Farm Energy Community of Practice at http://www.extension.org/ag+energy

(8/12)
(10/12)