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.
As a bonus and possibly the most important consideration, applying organic material such as the manure of cattle to our soils preserves the soil organisms on which we depend for fertile soils.
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 NH
3 and H
2S.
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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