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Why conserve nutrients?

Doug VanOrnum Published on 20 March 2013

Imagine what our landscape must have looked like, not really all that long ago. Tens of millions of bison roamed the American plains in clusters so large one could have seen them from space.

These immense, grand herds would devastate each valley they came through. A flowering meadow would turn into a moonscape overnight. If a valley was lucky, it would see a full year or more before the bison returned, so it could attempt to recover from such an onslaught.

Nomadic early Americans, of course, greatly depended upon these herds for their livelihood and followed them wherever they went. They brought their families and shelters with them – the entire community was mobile.

They would hunt and kill only what they needed, consume all that was consumable, make sure the entirety of the animal was used respectfully one way or another and celebrate the animal’s sacrifice, in part by giving thanks to the herd.

Times have certainly changed. Now we house our own (much smaller) numbers of milking and beef cattle in one place (whether in barns or fenced parcels of land), provide all of their food/nutrient needs and proactively collect and redistribute their wastes.

As stewards of both the herd and the land needed to support them, like the early Americans, today’s farmers also have the important responsibility to conserve and re-use everything they can. Most critically, the nutrients brought onto the farm must be collected and redistributed safely from the farm.

“Historically, dairy farmers have been all about sustainability,” says Marie Audet, co-owner of Blue Spruce Farm in Bridport, Vermont, “even before that was a popular little ‘buzzword.’

We care about our environment. It’s not only possible to protect our water supply and put out a quality product – it’s imperative.

“Fifty years ago everybody was contributing to ‘phosphorus in the lake.’ Well, society is evolving. Dairy farming is evolving. Farmers have to look to a future – by 2050 – of increasing our food production by 70 percent to feed this growing population. That happens with innovative, sustainable, creative ideas and technology.”

Farmers have long devised and practiced methods to do just that. For example, to conserve nitrogen (that would otherwise volatize and be lost to the atmosphere), instead of spreading manure wastes onto the ground, many farmers inject it into the soil.

Aeration is one of these methods, where numerous holes are poked into the ground prior to manure application. The holes give the manure greater opportunity to soak into the ground.

Farmers know that lower ground temperatures also reduce nitrogen volatility. By injecting when the soil is cool (less than 50 degrees), additional nitrogen can be conserved.

Application of nitrogen to a growing crop mid-season, just exactly when the crop can use the nitrogen, is another common practice. By providing plant-ready nutrients when the plant needs it, total nutrient consumption is optimized and crop yield can also increase.

Audet continues, “We capture all the nutrients on our farm. We’re regulated and watched, and we measure … it’s a scientific process; it’s not just ‘shoot from the hip.’ The whole idea with this type of fertilization … is to keep the nutrients where they’re needed, right where the plants are.

“I want people to know it’s not just us – every size farm is adopting sustainable practices,” she says.

‘Green manure’
Some farmers temporarily bind the nitrogen left over from a previous crop in a fast-growing “catch crop,” such as radishes and rye – so the N doesn’t wash down into the soil (leach) or volatize to the atmosphere. When the crop is later tilled back into the soil, it releases the nitrogen (and also provides desired organic matter).

Anaerobic digester
Even after manure has been successfully land-applied and with the proper coverage, there is still significant opportunity for nutrient loss. It can take a long time for bacteria in the soil to break down nutrients into an inorganic, plant-ready state.

Anaerobic digesters are another important nutrient management solution for some farmers because, in part, it does the job of converting those nutrients into a “plant-ready” state. Once the digested liquid is subsequently land-applied, crops are able to immediately absorb and begin to make use of those nutrients.

Blue Spruce Farm also employs a digester (in part) to enhance its nutrient management capabilities. “We capture all the manure,” Audet says. “All of the wastewater – everything that happens on this farm – and we redirect it to [become] a whole bunch of value-added products.”

Protecting our waterways
Most farms have waterways winding through and around their farmland. Blue Spruce is no exception. “We also keep [nutrients] away from any possible streams, so that if there is a water event and we do get some rain, it’s not going to go anywhere.

It’s going to stop right where it is and that’s our whole intent. Historically, we didn’t know any differently [but then believed], the most efficient use of our farmland was to use every square inch. We don’t do that anymore. We know better.

So what have we done? All this marginal land on our farm and on most farms in our state is grown back into forest – serving as natural buffers. If it rains or if some nutrients escape, [the nutrients] have a place to land way before it gets to a stream.”

Nutrient supplies are not infinite
Phosphorus (P) is a relatively rare nutrient found in the earth’s crust. Many do not realize that P is not a renewable mineral – P cannot be synthesized, and global supplies of P, like oil, are finite.

Large amounts of P are lost each year from fields through erosion and runoff, and some experts fear we will face a critical shortage of P within the next 30 to 50 years.

Therefore, a farmer’s vigilance in preventing runoff, in addition to keeping our waterways clean, could also contribute toward ensuring that adequate supplies of P will be available for generations to come.

Progress
“We didn’t always do it right. We’re not perfect today. But we are doing more every day. We are capturing the nutrients. We understand that we can’t just let them go ‘at will.’

What I’d like to say to folks who claim that the model of dairy farming today is inconsistent with a ‘clean lake’ is, ‘Come to a Vermont farm and look for yourself.’ We are driven to do the right thing. Because we have a lot of pride.” PD

VanOrnum is with the business development R&D department of DVO Inc .

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Doug VanOrnum
Business Development, R&D
DVO, Inc.

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