Agriculture Reference
In-Depth Information
Limiting manure application to the P needs of
the crop is one way to avoid continued accumula-
tion of P in soil and to minimize potential P runoff
and contamination of surface water. Regulations
limiting manure application to the P needs of the
crop are in place for many states in the USA, and
the federal CAFO regulations to address water
pollution call for site-specific decisions on whether
N- or P-based manure application limits are needed
to protect water quality. Also, some federal cost-
share funding is now being linked to the develop-
ment and implementation of P-based nutrient
management plans. Phosphorus-based nutrient
management regulations dramatically increase
the amount of land required to utilize manure and
likely will have a severe, detrimental effect on much
of the agricultural economy in areas of intensive
animal agriculture. The areas with excess manure
N or P are in critical need to develop and imple-
ment off-farm less expensive alternatives to land-
application of manure.
small watering areas. Either is highly effective in
reducing pollution of streams. Two streams with
extensive riparian grazing had a nearly complete
lack of woody vegetation while the bank of a
third stream with no grazing was vegetated with
a mixture of grasses, shrubs and trees (Wohl and
Carline, 1996). Of the ungrazed stream banks,
6% were eroded, but 81% of the stream banks
were eroded in grazed areas. Subsequently,
a combination of stream bank fencing, bank
stabilization and installation of rock-lined ani-
mal crossings were implemented. These changes
resulted in large reductions in total suspended
solids and in fine substrates in the two streams
that had been grazed. Exclusion of livestock
from stream banks promoted rapid re-vegetation
and stabilization of eroding areas. Reductions in
sediment load were accompanied by increased
populations of the insects (mayflies, stoneflies,
beetles, bugs and flies), worms, snails, prawns
and marron that serve as food sources for fish, as
well as improvement in fish communities.
Reduced stream-bank erosion (Kauffman
et al
., 1983) increased ground cover (Ranganath
et al
., 2009), and reduced stream concentration
of total N (Macklin, 2011) and total P (Macklin,
2011) are all reported with exclusion of live-
stock from streams. Soil and P loss were lower in
pastures where cattle were prevented from
stream-access by fencing than in grazed areas
(6-61 versus 94-266 t km
−1
year
−1
and 3-34
versus 37-122 kg km
−1
year
−1
, respectively;
Zaimes
et al
., 2008). However, fencing of every
stream to exclude cattle may not be an economi-
cal strategy (Fitch and Adams, 1998). Fencing
of riparian areas (the zone adjacent to a stream
or any other water body) is expensive, with
both installation and annual maintenance
costs. In addition, the width and route of some
streams fluctuate widely throughout the year as
rainfall varies.
Questions about the economical and mana-
gerial feasibility of fencing cattle out of streams
has led researchers to explore alternatives to
stream bank fencing. Some research indicates
that merely providing off-stream water sources
will reduce time spent in streams even without
fencing cattle out of streams (Miner
et al
., 1992;
Godwin and Miner, 1996; Sheffield
et al
., 1997).
When an off-stream watering area was made
available, the time spent near the stream by four
beef cows reduced from 60 to 15 min day
−1
during
Best management practices
The identification and implementation of solu-
tions to the generation of excess manure in con-
fined animal feeding operations are necessary to
enable such agricultural operations to thrive in
environmentally sensitive areas. BMPs are often
cost-shared (subsidized by the government or
private organizations) and are included in the
nutrient management plan that is the core of
most CAFO permits. The impacts of BMPs have
been reviewed frequently (e.g. Terry, 1993;
D'Arcy and Frost, 2001; Prokopy
et al
., 2008); a
few of these are briefly described below.
There is increasing recognition by industry
groups that cattle should be excluded from direct
access to streams and ponds because it is the
right thing to do, both environmentally and eco-
nomically. There is significant evidence that, if
allowed access to streams, animals are a direct
source of pollutants, and they reduce riparian
vegetation, which makes them vulnerable to
erosion and physical alteration of stream banks
(Kauffman
et al
., 1983; Williamson
et al
., 1996;
Wohl and Carline, 1996; Line
et al
., 2000;
Parkyn
et al
., 2003; Ranganath
et al
., 2009).
Stream fencing can refer to both the total
exclusion of livestock from streams and the use
of fences to restrict livestock to crossings and/or
