A couple of years back, we learned about "carbon ranching" at the Quivira Coalition conference, and decided to experiment with adding compost to selected areas of our pasture. Carbon ranching, building up soil carbon, is supposed to enrich the soil, increase forage yields, and enhance water retention. Makes you feel good too, as it pulls carbon out of the atmosphere and helps reduce the planet’s greenhouse gas burden.
First, we needed some baseline data. We sent some soil samples to Kinsey labs, which gave us the percent humus. More samples were taken by Professor Richard Conant at Colorado State University, to measure carbon content. I’m not quite sure of the relationship between humus and carbon, but from these baseline figures, we’ll be able to know whether carbon and humus are going up or down after several years of soil treatments.
Second, we applied a thin layer (1/4 inch) of compost in three strips 100 feet wide and 2600 feet long on our West Bottom pasture in Big Valley. Alternating strips received no compost. The compost was largely vegetative in nature, heavy on Carbon, lower on Nitrogen. We’ll take more soil samples in future years to see if the compost made a difference in soil carbon storage.
In the meantime, we took some vegetation samples later that same year (2012) to see whether the compost increased forage yields in the short run. I cut all the grass (mostly brome) and alfalfa within two randomly tossed quarter-meter squares within the composted and non-composted strips. Twenty-two samples in all. These samples were dried and weighed at CSU. The results: Compost increased forage yields by 10% on the South end and 17% on the North end of the pasture.
So far, so good. Does the compost also increase water retention in the soil? We have no way to measure this, but we can say we’ve used a lot less irrigation water in 2013 than in 2012. That’s mostly because we had some good late spring snows and robust thunderstorm activity in June and July, 2012. But the compost may have helped too.
In addition to the three strips applied in 2012, we composted 33 additional acres on the upper east side of the big pivot, 17 additional acres on the east side of the small pivot, 17 additional acres on the southwest side of the big pivot. On the east side, a commercial compost made up of organic dairy manure and vegetative matter was applied. The west side application was of our own making – two year old horse manure mixed with wood chips.
Whatever the cause, hay yield (tons per acre) jumped 72.9 percent in 2013 over 2012. We got more hay in one cutting in 2013 than we did in two cuttings in 2012. The increase was higher in composted areas than in non-composted areas. Note, however, that much of the increase was due to added precipitation, and the first cutting in 2012 was done June 5 whereas in 2013 it was done June 18, giving 13 extra days of growth in 2013.
More Forage, Less Hay
Don’t get me wrong. Our objective is not to make more hay. In fact, we want to get along with as little hay as possible. Compost is expensive. Hay is expensive, whether you grow it yourself or buy it. The more forage that goes directly into cows bellies instead of being cut, dried, raked, baled, hauled, hauled again, and fed, the better off we are, profit-wise.
That’s why we’ll be giving "windrow grazing" a shot this fall and winter. We’ll cut some of our mature forage, but instead of baling it, we’ll rake it into windrows and let the cows have at it small sections at a time. Hopefully, a new growth spurt will fill in the areas between the windrows, giving our herd a double dose of good forage when the time comes.
We’re also experimenting with grazing as a way to increase soil fertility and forage production. We’re moving our 60 pairs of cow-calves every other day to a new paddock, leaving plenty of time for the plants to fully recover. We call it recovery grazing. It’s supposed to stimulate plant growth and spread fertilizer all over the pasture. More forage, less hay. We’re also subjecting some weedy areas to a technique called “mob grazing.” But that’s another story.