Iowa Farmer Today

The future development of cellulosic-based ethanol might help farmers increase their soil quality.

The more diverse the crop rotation, the better the soil quality, Doug Karlen, a research soil scientist with USDA’s ARS National Soil Tilth Laboratory in Ames, says in a study published in a 2006 Agronomy Journal.

“It (this study) lays the foundation why we need to move to a more diverse landscape,” he says.

Karlen says a rotation that includes three years of a forage crop was the best rotation he studied in four long-term crop rotation studies performed at three locations — Northern Research Farm near Kanawha, Iowa State Universtiy’s Northeast Research Farm near Nashua, and Lancaster Agricultural Research Station near Lancaster, Wis.

He says the rotations that included forages improved soil quality by allowing more water infiltration and reducing the amount of N leaching.

A continuous-corn rotation had the lowest soil-quality rating and profitability over 20 years at the all the locations, Karlen notes.

He says deep roots from the forages are one of the reasons for the increased water infiltration. That also results in less water runoff from the field and as well as the amount of nutrient runoff as well.

The reduced water runoff from forage rotations also could result in less peak flows for streams. That could mean less soil erosion along stream banks as well.

With help from Mike Duffy, ISU ag economist, Karlen was able to calculate which rotation was the most profitable or had the smallest lost. They used costs of production from Duffy and other sources.

The income used actual yields from the study and the prices at the time from the National Agriculture Statistics Service. They did not include organic premiums or governmental payments.

“We took out the subsidies,” Karlen says.

Almost all the rotations had a loss when figuring profit levels without government payments. In one interesting note, the continuous-alfalfa rotation from Lancaster, Wis., had a high loss of $52.61 per acre despite having a good soil-quality index.

In the paper, Karlen and authors explain the loss was a result of lower-than-expected yields possibility because of a low-test for K.

Their soil-quality test did not include K soil tests.

Four rotations returned a profit.

At the Kanawha site, the corn, oats with legume seeding and two years of meadow returned $9.71/acre.

At Nashua, the corn-soybean rotation returned a profit of 81 cents/acre, and the continuous soybean rotation returned $16.99/acre. At Lancaster, the corn-soybean rotation returned $18.21/acre.

The continuous-corn rotation at all three sites had the largest loss at all three locations.

At Kanawha, they figured the rotation lost $93.89/acre. The rotation had a loss $64.75/acre at Nashua and $57.87/acre at Lancaster.

The study was conducted before the increases in the commodity prices seen in the past couple years. However, Karlen says the relative profitably should remain close to the same because while corn prices have increased, so have other commodities, such as soybeans, wheat and hay. The increase in commodity prices in the past couple years is a result from increased ethanol production throughout the country.

Karlen says the development of cellulosic ethanol could increase prices for forage. That could allow farmers to increase profits while improving their soil quality.