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Saturday, January 20, 2018

Mitigating the harm dairy causes to the environment

We are having a debate in New Zealand for and against irrigation.  It really boils down to a debate on our national dairy herd.  With irrigation, you can put cows on land that otherwise would not support them.  Our dairy herd can then increases and with it the pollution of our environment.

True, there are some concerns about the irrigation itself but the main concern is that it allows the increase in our national dairy herd and with it increased pollution.

To come out for or against irrigation  may be good for radio sound bites but as with most cases in the affairs of man, the devil is in the details.Clearly we need irrigation for our farmers to fill in the gaps left by nature. Even in the best areas, there are periods without rain.  A farmer needs reliable inputs to be able to run his business.

On the other hand, equally clearly, if we can not find ways of farming that preserve our environment then the crude sledge hammer method of reducing herds and restricting where they can graze must be taken.  The question is;

 Can we have dairy herds and not pollute.

The answer may be yes for some areas and no for others and will depend, to quite a large extent, on the details of how we farm.

The core of the problem is to be able to apply the waste output of the cows back on to the  land a) in a way, b) in a concentration and c) at the right time such that it constitutes a valuable fertilizer, is taken up by the pasture plants, and hence is not an environmental pollutant. If this can be done, dairying is no longer a source of pollution.

Throughout history, societies that trashed their soils, declined and disappeared.  One factor in trashing soils is not returning nutrients to the soil that are extracted.  And....in so far  as is possible, nutrients must be returned in an organic form that benefits the soil organisms.  Quite clearly, the urine, manure and spilt milk from a dairy herd constitutes a valuable resource for the enhancement of the soil.

That is not to say that chemical fertilizer should not be used but as you will see, much less of them can be used if farming methods are tweaked.

If farming remains a process of plow, add chemical nutrients, sow the seeds and irrigate then our soils will degrade, wash to the sea, pollution will be rampant and we will go the way of many previous societies that mined their soils  instead of farming them.

It takes a lot more 'smarts' to farm in a way that improves the soil, reduces  inputs, increased water infiltration,  and leaves you with a much better farm to pass on to your children or to sell at retirement than when you started.  What is not generally realized is that you can do this while improving your bottom line and your resilience to weather and  price fluctuations.

Let's look at some of the tools we have available.

Riparian Zones
Fencing off streams and encouraging the growth of trees, shrubs and grasses between the fence and the stream is a great help.  Not only does it stop the cows from entering the stream and urinating and defecating into it but the roots of the vegetation of the riparian zone take nutrients from the water table which is slowly flowing toward the stream.

However, it has been reported that 70% of the nutrients entering the streams comes from the very small feeder streams and ditches.  It is simply not possible to fence off every little feeder stream. We need some other measures in the pasture.

Composting Barns
Composting barns use deep layers of wood shavings or coarse saw dust as bedding and the cows are allowed (not forced)  to bed down there at night.  They also have free access to the barn to escape inclement weather.  The bedding is stirred mechanically every day, keeping it aerobic.  It has been found that cows prefer such an environment to bed down in, even choosing it ahead of a straw-lined byre.  The composting process produces heat which reduces the feed needed by  the cows and a rich compost eats up pathogens.  The compost captures all the nutrients from the waste of the cows including N and S which in an anaerobic system  go off as the gases NH3 and H2S.

The bedding can be applied to the fields at the correct concentration and correct time which most benefits the soil and the pasture plants and hence causes no pollution.  Some research needs to be done on what portion of the effluent of a cow is released while in such a barn compared to what proportion is released out on the pasture*.  Do they mainly urinate and defecate at night or in the day,,,, while they are grazing or when they are chewing their cud.  this would give an indication of how much of the nutrient stream can be captured by a composting barn.

*Great job for some long suffering masters student

Bio-Gas Generators.
At long last a farm in Southern New Zealand is using the waste produced in the milking shed* to generate bio-gas.  The biogas is use  to produce electricity. The waste heat from the motor which drives the generator is used to heat the water used in the milking shed.  This combination, utilizing the waste heat from the motor that powers the generator, makes for a very efficient system, energy wise.  The effluent from the biogas generator contains almost all the nutrients in the waste stream since mainly C and H have been taken off as biogas (and some of the S).   As with compost-bedding the effluent remaining after extracting the biogas, can be applied to the fields when and in what concentrations most benefits the pasture and hence least pollutes the environment. Excess electricity is sent to the grid for an added income stream and/or excess biogas can be used in the house and farm.

*More work for that long suffering student.

Managing the Pasture
We have now removed a portion of the waste stream with a)Riparian zones, b) compositing barns and c)biogas generators.  Let's see what we can do out on the pasture.  There is a fantastic book by David R Montgomery called Growing A Revolution; Bringing back our soils.  In it he describes visiting farmers all over the world who have independently come up with a way of farming.  The methods they use would be familiar to any farmer before the advent of cheap chemical fertilizers but each method is updated in light of modern knowledge. Farming this way results in an improved bottom line, slashed pollution to the environment, reduced farming costs, increased infiltration of rain, continually improving soils  and as a bonus sequesters significant amounts of carbon in the soils.

It has become to be known as Conservation Agriculture.


It also, due to the greatly increased organic content of the soil, results in the capture of much of the Nitrogen when a cow urinates. The urine is soaked up by the organic material giving the soil organisms time to scavenge the nitrogen.

Of course, it also results in the sequestration of considerable carbon in the soil.

Before we go off half cocked and reduce one of our most valuable industries, we must pay attention to the details.  Farming can not be allowed to degrade our environment but there are farming methods which address this problem.  What is great is that these methods can improve the bottom line of the farmer and his resilience to weather and fluctuating prices for his products while at the same time making him the darling of the greens.  The devil is in the detail.

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