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David Davis
21262 Genoa Road
Linneus, MO 64653
Phone: 660 895-5121
FAX: 660 895=5122
Email:
DavisDK@missouri.edu
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GRAZING MANAGEMENT AFFECTS MANURE DISTRIBUTION
BY BEEF CATTLE
P.R. Peterson and J.R. Gerrish1
Abstract
Livestock excrement is a valuable source of soil nutrients for pasture. Our objective was
to examine the influence of grazing system design and landscape features on manure
distribution by beef cattle. Grazing systems with 3, 12, and 24 paddocks were rotationally
stocked with Gelbvieh X Polled Hereford cows, their Angus-sired calves, and yearling
steers for 2 years in northcentral Missouri. Stocking rates for the 3-, 12-, and 24-paddock
systems averaged 2.7, 2.2, and 1.7 acres per cow/calf pair equivalent, respectively, from
April through November. Each system treatment included one cell with water available
in every paddock and another cell with lane access to water. Manure distribution was
monitored on selected paddocks in each cell. Lane access to water resulted in a 13% loss
of manure off of paddocks in a 32-acre, 24-paddock cell. Grazing cells with frequent
rotations and minimal landscape variation within individual paddocks resulted in the most
uniform manure distribution over the entire pasture.
Introduction: Livestock excrement represents a valuable, recyclable source of soil
nutrients on pasture because 60-95% of the nutrients consumed by grazing livestock pass
through the digestive tract (Wilkinson and Lowrey, 1973). Dalrymple et al. (1994)
attributed 979 lb/acre of added pasture growth and 95 lb/acre of added beef production to
cattle excrement deposited on pasture. Shade and watering locations are sites of P and K
accumulation in pastures because cattle tend to camp and loaf, and thus defecate and
urinate, in these areas (West et al., 1989; Gerrish et al., 1993; and Mathews et al., 1994).
Grazing system design parameters such as level of paddock subdivision (rotation
frequency), stocking rate, and water accessability may influence the uniformity of return
of nutrients to pasture via cattle excrement. The objectives of this experiment were to 1)
quantify the proportion of beef cattle manure deposited in water-access lanes, 2) determine
the impact of cattle rotation frequency and landscape features on manure distribution on
individual paddocks and 3) simulate manure distribution on entire grazing cells.
Materials and Methods: A grazing experiment was conducted for 2 yr at the University
of Missouri-Forage Systems Research Center on mixed cool-season grass/legume swards.
Grazing systems with 3, 12, and 24 paddocks were rotationally stocked with Gelbvieh X
Polled Hereford cows, their Angus-sired calves, and yearling steers. Stocking rates for
the 3-, 12-, and 24-paddock systems were as follows: 2.0, 1.6, and 1.25 acres per
cow/calf pair equivalent, respectively, from mid-April through mid-July; and 3.3, 2.7, and
2.1 acres per cow/calf pair, respectively, from mid-July through November (1 yearling
steer = 0.7 cow/calf pair). This resulted in 9 to 18 cow/calf pairs and 11 to 20 yearling
steers per grazing cell. Each of the system treatments included one grazing cell with water
available in every paddock and another cell with lane access to water. Detailed sampling
of manure distribution was performed in one, three, and three paddocks of each of the 3-,
12-, and 24-paddock cells, respectively, in 1993 and 1994. Paddocks to be sampled were
subdivided into 60 to 75 square grids. Paddock size varied from 1.3 acres in the 24-paddock cells to 14 acres in the 3-paddock cells. Grid size thus varied from about 900 ft2
to about 7000 ft2 depending upon paddock size. Counts of manure piles deposited were
obtained in a checkerboard fashion using the grids immediately after each grazing period.
A defecation event resulting in a minimum ground coverage of 25 in2, whether in one spot
or scattered, was counted as 1 manure pile for this experiment.
The number of piles deposited on the paddocks per head per day for each grazing
period was calculated based upon the percentage of the paddock area counted and the
number of animal unit days per grazing period. Each animal over 400 lbs was considered
to be 1 animal unit for this experiment. The difference in piles per head per day deposited
on paddocks of grazing cells with the same paddock number but varying in water
accessability was attributed to manure deposited in lanes in the lane-access-to-water cells.
Sampled paddocks were replicated to simulate entire grazing cells by assigning the manure
distribution obtained in sampled paddocks to unsampled paddocks in the respective cells.
This assignment was based upon similarity in landscape features when possible; otherwise,
assignment was random. Contour maps were then constructed for these simulated cells.
Results and Discussion: Table 1 illustrates the effect of water location on manure
distribution. Lane access to water resulted in an average of 13% loss of manure off of the
paddocks in the 24-paddock system. At current costs of commercial fertilizer, this would
be equivalent to US$910 of fertilizer nutrients per year for a 100-cow herd. In addition,
this experiment was conducted on grazing cells of about 32 acres, and sampled paddocks
never required more than about 700 ft of lane travel from the paddock gate to water.
Greater distances would likely be incurred in a commercial-sized grazing cell and would
probably result in greater nutrient loss in lanes. No consistent, significant loss of manure
in water-access lanes was detected in the 12-paddock systems (data not shown) probably
because cattle never had to travel more than 450 ft of lane from sampled paddock gates to
water in our system design. In contrast, a significant loss of manure (avg. of 22%) was
observed in the 3-paddock system with lane access to water. In addition to requiring 750
ft of lane travel from the paddock gate to the water tank, the sampled paddock had a tree-lined ditch that held water through much of the grazing season. This was an attractive
camping site for cattle, and likely contributed to some of the manure loss attributed to the
lane in the 3-paddock system.
Figures 1 to 3 represent simulated contour maps of 2 years of manure accumulation
on grazing systems that had water available in individual paddocks. Figure 1 simulates
a 32-acre, 3-paddock rotational system with an average grazing period of 10-20 days. The
manure distribution observed on the sampled paddock was replicated to simulate the entire
cell, inverting the distribution when necessary to maintain proper orientation with water
tanks. Greatest manure accumulation was near water and the tree, and a zone of lesser
accumulation (<20 piles per 500 ft2) was observed between about 650 and 900 ft east of
water. Cattle were frequently observed to be under the tree even when the temperature
was cool and comfortable. We surmise that when cattle were loafing in the back third of
the paddock, they were attracted to the tree. Thus most of the area in the back third
received less manure return and would likely become depleted of soil fertility if cattle
removed nutrients from that area through grazing. Figure 2 simulates a 32-acre, 12-paddock system with a grazing period of 2-6 days. Paddocks monitored in this cell were
#2, 6, and 10. Paddock #10 had no striking landscape features. Despite a zone of greater
accumulation close to water, manure distribution was quite uniform over the majority of
that paddock. In contrast, paddock #2 had a draw that frequently held water running
diagonally through it. The wetness of the draw resulted in cattle loafing on the slopes to
either side of the draw and thus greater manure accumulation in those areas. Since the 3
paddocks sampled in this cell represented 3 distinct landscapes, assignment of distributions
obtained to unsampled paddocks in the cell was done based upon similarity in landscape
features (eg. the draw in paddock #2 continued through paddocks 5, 8, 9, and 12; thus its
distribution pattern was used for all of these paddocks). Figure 3 simulates a 32-acre, 24-paddock system with a grazing period of 1-2 days. Distributions obtained in sampled
paddocks of this cell were not distinctly different due to landscape features, so assignment
to unsampled paddocks in this cell was random. About 95% of the cell received 40-60
piles per 500 ft2. The increasing concentration of manure piles observed with increasing
paddock subdivision (avg. of 21, 27, and 46 piles per 500 ft2 for the 3-, 12-, and 24-
paddock cells, respectively) can be explained largely by the corresponding increases in
stocking rate. Despite the presence of a gradient of manure accumulation toward water
in all systems, the steepness of the gradient in the 24-paddock cell was less than that in the
12-paddock cell, and considerably less than that in the 3-paddock cell. However,
landscape differences somewhat confound comparisons among cells. Our findings concur
with those of Morton and Baird (1990) who reported greater aggregation of dung patches
when sheep grazed a paddock for 4 days as compared to 1 day. In contrast, Mathews et
al. (1994) reported no advantage of rotational stocking over continuous stocking for
improving uniformity of K return via cattle excrement. However, moveable shade and
waterers used in their experiment favored greater uniformity of excretal return than would
be expected under typical continuous stocking situations.
In summary, a significant loss of manure off of pasture occurred when cattle were
forced to travel a lane to access water. In addition, as rotation frequency increased and
landscape variation within a paddock decreased, the uniformity of manure distribution on
individual paddocks and entire grazing cells was improved.
Literature Cited:
Dalrymple, R.L., R. Stevens, T. Carroll, and B. Flatt. 1994. Forage production benefits from nutrient recycling via beef cattle and how to manage for nutrient recycling in a grazing cell. p.269-273. In American Forage and Grassland Council Proc. Lancaster, PA. 6-10 March 1994.
Gerrish, J.R., J.R. Brown, and P.R. Peterson. 1993. Impact of grazing cattle on distribution of soil minerals. p.66-70. In American Forage and Grassland Council Proc. Des Moines, IA. 29-31 March 1993.
Mathews, B.W., L.E. Sollenberger, P. Nkedi-Kizza, L.A. Gaston, and H.D. Hornsby.
1994. Soil sampling procedures for monitoring potassium distribution in grazed pastures. Agron. J. 86:121-126.
Morton, J.D., and D.B. Baird. 1990. Spatial distribution of dung patches under sheep grazing. N.Z. J. Agric. Res. 33:285-294.
West, C.P., A.P. Mallarino, W.F. Wedin, and D.B. Marx. 1989. Spatial variablity of soil chemical properties in grazed pastures. Soil Sci. Soc. Am. J. 53:784-789.
Wilkinson, S.R., and R.W. Lowrey. 1973. Cycling of mineral nutrients in pasture ecosystems. p.247-315. In G.W. Butler and R.W. Bailey (ed.) Chemistry and biochemistry of herbage. Vol. 2. Academic Press, New York.
Table 1. Manure piles deposited per head per day on paddocks in
grazing systems differing in paddock number,
water accessability, and landscape features (2 yr avg).
Month
------------------------------------------------------------
System May June July Aug Sept Oct AVG
-----------------------------------------------------------------------------
----------------- manure piles/head/day --------------------
24-paddock, 12.9 12.3 14.1 9.9 10.7 8.5 11.4
water in
24-paddock, 10.7 11.3 12.0 7.4 9.7 8.0 9.9
lane
.............................................................................
% lost in lane 17 8 15 25 9 6 13
-----------------------------------------------------------------------------
3-paddock, 10.0 10.9 8.4 7.1 --- 7.2 8.7
water in, 1 tree
3-paddock, 8.3 7.6 6.2 6.2 --- 5.5 6.8
lane, ditch
with trees
.............................................................................
% lost in 17 30 26 13 --- 24 22
lane, ditch with trees
1Assistant Professor, Plant Science Department, Macdonald Campus of McGill University,
Ste-Anne-de-Bellevue, Quebec, Canada H9X 3V9; and Research Assistant Professor, University of Missouri-
Forage Systems Research Center, RR1 Box 80, Linneus, MO 64653, respectively.
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