Renewable Farming

15 tons of dry cattle manure per acre lifted corn yields 40 to 50 bu./acre

We’re guesstimating that one of our mid-Iowa WakeUP clients added at least $100 per acre to his corn profit on the strips where he spread 15 tons of dry feedlot manure last spring. 

December 14, 2021 Fortunately a large feedlot is about 5 minutes away from this field, and the lot operator was willing to deliver and spread manure for $200 per hour. The combine GPS yield map below overlays strips where spreader trucks laid down the manure.

The entire field averaged 200 bu. per acre. We reason that since the manured strips yielded 250 bu. and up, it’s rational to estimate a value of 40 to 50 bu. for the manure. This organic fertility is on top of his regular NPK program. At $5.50 corn, another 40 bu. adds $220 more gross income. The grower estimates total manure cost at $100 per acre. 

Some of the $100 per acre benefit of manure this season will persist the next two or three years because of residual soil health, microbial activity for NPK conversion, and moisture holding capacity. Microbes multiplying from the manure can dissolve elemental soil nutrients like potassium and phosphorus with 10 times the power of root exudate acids.

However, the nearby feed yard hasn’t laid in any new lots of feeder cattle this fall. 600-lb. feeder steers cost $170 to $180 per hundred pounds, corn prices are $5.70 per bu. in that locality — and trucking in feeders from Plains states is hard to line up. Early December feeder cattle placement on feed is down 20% from a year ago.

This example reminds us of several conversations we had with Dr. Jerry Hatfield when he was director of USDA’s National Laboratory for Agriculture and the Environment at Iowa State University. He always encouraged enhancing soil biology with manure, cover crops and rotations including small grains and forage. His soil lab conducted several demonstrations showing Iowa corn-soybean growers that they could profit by including clovers, wheat and oats in rotation with corn and beans. The lab paid farmers to conduct the field tests for several years. 

Hatfield told us, “But when we quit paying incentives after the demonstrations proved profitability to those growers, they reverted back to alternating corn and soybeans.”

The soil lab conducted similar farm-scale trials with livestock manure, both liquid and dry. When soil biological activity soared from these applications, yields climbed too. But the fertilizer industry had instilled the notion that manure is so yesterday. Back in the 1960s, Farm Journal editor Lane Palmer ran a feature titled, Is Manure Worth Hauling? The general view of that era was that manure was a nuisance, not a viable crop nutrient.

Now, with biological farming on the ascendency, manure has again gained recognition as a rich resource.