DECISIONS ABOUT FERTILIZING PASTURES
Food and Resource Economics Department
University of Florida
Gainesville, Florida 32611
Questions about how much fertilizer to use on pastures don't seem all
that tough, at first. After all, only three pieces of information are
necessary: (1) the amount of beef produced in response to fertilizer levels,
(2) the cost of the fertilizer applied, and (3) the price of the cattle sold.
Then apply fertilizer until the value of the beef produced is equal to the
cost of that much fertilizer.
But the pavement ends and the west begins when we try to estimate how
much beef can be grown with a given.amount of fertilizer. There are all
sorts of little thorny problems about soil types, grass species, past grazing
and fertilization history, and cattle management practices that make it hard
to figure out. Then there is the weather: the only thing we know for sure
is that we'll never get the right amount of rain at the right time.
And it is just as tough to figure out what cattle prices are going to
be. Recently, of course, cattle prices have been disastrous, so net incomes
to cattle operations have been low, and as a result, the amount of money
available for next year's fertilizer has been reduced.
So what seems like a simple question "How much fertilizer should I use
this year?" turns out to be a really tough one. In fact, there really isn't
a general answer. Here's why. The cattle business is a slow changing, low
profit kind of business. One of the most important things influencing the
amount of fertilizer necessary is how many cows are being grazed on the
pastures. In practice, stocking rates are determined by long run cattle
performance on a ranch, based on handling the cattle and the pastures pretty
much the way it was done last year. Making short-run shifts in cow-herd
numbers can ruin a rancher. So the short-run problem has been to fertilize
in such a way that the existing cow herd can be maintained, because selling
off part of the cow herd is like the Alaskan sled-dog racer who got caught in
a storm and had to eat some of his dogs. He couldn't go as far, as fast,
when the weather cleared.
But cattlemen are cutting back, it seems to me (although the January 1,
1983 inventory indicated the Florida cow herd increased by 75,000 head). They
are trying to grow more of their necessary nitrogen with legumes; they are
searching for the minimum amounts of fertilizer necessary to keep their
pastures in relatively healthy condition, so that when they do fertilize they
will get the response they seek. And they are trying to make more effective
use of native range.
All those moves are supported by a realistic look at what the future
likely has in store for cattle prices and nitrogen costs. There have only
been a couple of years in the last 10 or so when cows covered total costs,
and I see small hope for anything different in the future. And natural
gas price deregulation bodes ill for nitrogen prices.
Research over a lot of years supports a basic strategy of basing cow-
herd numbers on the tough forage times. Going way back, Jones et al.
reported that native and improved pastures, used in combination,supplement
each other. Winter feed supply was greatly increased by deferred grazing,
resulting in an increase in herd productivity.
Anderson and Hipp (Table 1) budgeted 1,000 cow herds under varying
intensities of land and fertilizer use, and found that (without considering
land taxes) the native range situation had the highest total return. A mix
of native and improved pastures was almost identical to the irrigated
situation with grass-clover pastures. The all-improved grass pastures
(which therefore had the heaviest reliance on fertilizer) had the lowest
returns of any operation budgeted.
Research also supports more emphasis
that clover and grass pastures yielded the
here, as did Koger et al. at Gainesville.
information for establishing legume pasture
on legumes. Peacock et al. found
best results in grazing trials
Prevatt and Mislevy have developed
But legumes are fickle, as Hodges et al. noted in 1953.
to get forage is to fertilize grass when it is warm and fixing
producers will keep some grass pastures in order to get forage
The surest way
to rain, and
when they need
To help make the fertilizer use decision, two things would be nice:
More information on how best to manage low levels of fertilizer use. And
calves that sold for a dollar or more a pound would not make the fertilizer
use decision any more precise, but would sure make it less painful.
*Table 1. A comparison of land use, estimated costs and returns and measures
of efficiency for five 1000 cow-calf her situations on flatwoods
soil in Florida.
Item 1 2 3 4 5
Acres of irrigated pasture 1,200 500
Acres of non-irrigated
improved pastures -- 1,000 2,000 1,000
Acres of native range -- -- 4,000 15,000
Total acres 1,200 1,500 2000 5,000 15,000
Return to land and management $11,026 9,394 3 857 11,426 16,571
Measures of Efficiency
Pounds of beef sold/acre 326 261 167 58 14
Pounds of beef sold/cow 392 392 334 292 206
Percent of calf-crop 90 90 85 85 73
Acres/cow 1.20 1.50 2.00 5.00 15.00
Fertilizer and lime
expense/cow $ 24.10 31.47 30.30 20.58
Feed cost/cow $ 14.18 14.18 16.43 12.10 13.76
Labor cost/cow $ 12.73 11.40 11.76 9.46 9.09
Cash cost/cow $ 76.46 78.79 69.70 54.76 34.22
land) $503.34 503.31 486.97 374.92 281.20
Return to land and
management/cow $ 11.03 9.39 3.86 11.43 16.57
Return to land and
management/acre $ 9.19 6.26 1.93 2.28 1.10
Source: Anderson, C.L. and T.
S. Hipp, Requirements and Returns for 1,000
Cow Beef Herds on Flatwood Soils in Florida, Circular 385 (April
Anderson, C.L. and T.S. Hipp. 1972. Requirements and returns for 1,000 cow
beef herds on flatwood soils in Florida. Fla. Agr. Ext. Cir. 385.
Hodges, E.M. et al. 1953. Pasture irrigation. Fla. Agr. Exp. Sta. Ann. Rept.
Jones, D.W. et al. 1960. Year-round grazing on combination of native and
improved pasture. Fla. Agr. Exp. Sta. Eul. 554A.
Koger, M. et al. 1970. Production response and economic returns from five
pasture programs in North Central Florida. Fla. Agr. Exp. Sta. Bul. 740.
Peacock, F.M. et al. 1976. Forage systems, beef production and economic
evaluations, South Central Florida. Agr. Exp. Sta. Bul. 783.