MANURE IS WORTH MORE THAN YOU THINK

For three straight years we have run an experiment looking at the effect of dairy manure on a corn silage field here at Miner Institute. The study was done in collaboration with the Cornell Nutrient Management Spear Program and has received funding from the Northern New York Agricultural Development Program. We started by applying 13 tons/acre of composted cow manure in strips slightly wider than our corn chopper head. From there, we split each strip into six different sections where we applied different nitrogen rates ranging from 0 to 200 units per acre. This gave us the ability to record data for the yield response to manure as well as nitrogen fertilizer.

In the initial year of testing we saw a whopping 4.6 ton/acre yield advantage for the strips that received manure (35% DM adjusted). This was estimated to translate into a net return of about $209/acre just from the manure – not bad for something that the cows give you for free!

We continued to monitor the site for two more growing seasons without applying additional manure but still applying six different nitrogen rates. In year two, we saw a net return of $152/acre from the manure at the most economic rate of nitrogen. While this isn’t quite as much as in the application year, it’s a testament to the fact the solid dairy manure takes multiple years to break down in the soil. The third year of monitoring brought a calculated net return of $99/acre for the manured strips. This comes to a total net return of $460/ace for that single manure application over the course of three years.

To put this in perspective, this means that the composted cow manure we hauled up to that 60-acre field was worth almost $30,000 in terms of future crop yield. I’ve tested lots of different products at Miner Institute that claim to boost crop yield, but none compared to the predicted value of manure to an acre that needs it.

All too often manure is seen primarily as a waste product, an inconvenience, and a liability. Check the price of bulk compost at a local garden center, and you will quickly realize that if you were buying that instead of manure, you’d have one hefty bill to pay.

As with most things, you can have too much of a good thing… Areas that have received heavy manure rates, year after year, are unlikely to benefit that much from additional manure. The field we conducted this research on was one of the farthest ones from the farm. While it did have a history of manure application, it has lower nutrient levels and has received much less manure than many of our fields over the years. Get the manure to the fields that need it, and it will make you money. If you don’t have enough manure to cover most of your fields every year, consider giving some of the closer fields a break from manure and targeting fields that are farther away.

Commercial fertilizer is only a partial substitute for manure since manure contains all the essential plant nutrients, carbohydrates, and beneficial microbes, all working together to help build a healthy soil environment. That’s why even the highest rate of nitrogen in our study could not compete with a moderate rate of nitrogen plus manure. In Texas, they call oil “black gold”. Rather than manure, perhaps “brown gold” is what we’ve got around here…

̶ Allen Wilder

wilder@whminer.com