Are you recouping the cost of straw removal?

Recently, there have been a few producers who have been interested in having their fields certified for the Montana Noxious Weed Seed Free Forage program as a means to earn a little extra for the straw that is being taken off of their wheat and/or barley fields.  While most fields meet the certification standards, some do not.  While the straw that does meet certification standards is easy to justify charging a little more of a premium for, sometimes producers should take a look at what they are charging for straw and put pencil to paper to see whether or not they are recouping the cost that it takes to produce that straw and accounting for the amount of nutrients and organic matter that is leaving the field.

To help figure this out, there was an article written by Dave Franzen, NDSU Extension Soil Specialist in last year's NDSU Crop and Pest Report that addressed the issue.  It is below.  I should mention, however, that the article was written with last year's prices included, so there should be adjustments made to account for 2013 prices but it is a very good place to start.

"Wheat straw contains roughly the following N-P-K concentration-
N             0.65%
P₂O₅ 0.23%
K₂O        1.54%

There are other nutrients of course, but the economic value of them in terms of fertilizer replacement is so low that it is not practical to consider them in a removal formula.

A ton of wheat straw therefore contains:
13 lb N
4.6 lb P₂O₅
30.8 lb K₂O

Current value of N as urea is 65 cents per lb of N ($600/ton 46-0-0).  Current value of P₂O₅ in 11-52-0 (MAP), taking out the N portion of MAP is about 49 cents per lb of P₂O_5. ($650/ton MAP).  Current value of K₂O is 48 cents per lb K₂O ($580/ton 0-0-60).

Therefore, the fertilizer value of 2,000 lbs of straw is
$0.65/lb N X 13 lb N/ton straw = $8.45/ton straw
+ $0.49/lb P₂O₅ X 4.6 lb P₂O₅ /ton straw = $2.55/ton straw
= $0.48/lb K₂O X 30.8 lb K₂O/ton straw = $14.80/ton straw
The total for N/P/K for a ton of wheat straw = $25.80/ton straw.

In addition, all straw has some value in its possible production of soil organic matter. About 1/3 of residues of any kind eventually become organic matter. In 2,000 lb straw, about 667 lb of straw eventually becomes organic matter. Given about 2,000,000 lb soil in the surface 6 inches of an acre, the organic matter addition amounts to 667in the straw / 2,000,000 X 100% = 0.03% organic matter.

After 10 years of removing 1 ton straw/acre, the reduction in organic matter may amount to 0.3% compared to what the soil might have contained with all straw left in the field.

The amount of organic matter reduced in any given year is not very significant and would be very difficult if not impossible to measure. However, over a long time it is possible to estimate its value.

In comparisons of eroded soils compared to non-eroded soils by Dr. Cihacek at NDSU, yield on low organic matter (1.5%) sideslopes may be roughly half the yield in similar soils with higher organic matter (3%). If the average yield was 30 bushels of wheat per acre on the higher organic matter soils, the benefit of the additional 1.5% organic matter is-30 bu/acre X 0.5 X $7/bushel (current estimated wheat price) =  $105/acre.

The reduction due to one year removal of 2,000 lb/acre of straw would be-0.03%/1.5% X $105/year = $2.10/acre per year.

This reduction is a cost, however, in every year afterwards, not just in the yield following removal. This example makes several assumptions. Noting yield differences due to organic matter differences within specific farms on similar soil types would provide more accurate estimates from those farms.

Occasional straw removal can be overcome with aggressive residue management strategies including no-till, strip-till, conservation till, adequate N rates on other rotational crops to encourage higher residue levels and organic matter retention."