Abstract—Since the early 1990s, U.S.
commercial fertilizer use, application rates, and management practices
have tended to change modestly from year to year, while fertilizer
prices have exhibited more variability.
Introduction
The major plant nutrients (nitrogen, phosphorus, and potassium)
are critical for maintaining crop yields but have also been associated
with the impairment
of numerous streams, lakes, and aquifers. For most U.S. crops and
in most regions, commercial fertilizer is the major source of plant
nutrients, although organic sources—such as legumes, crop
residue, and animal wastes—can also provide nutrients required
for plant growth. Commercial fertilizer is a major agricultural
input; farmers typically spend
over $10 billion annually on commercial fertilizer, although
fertilizer use and prices vary from year to year. Historically,
crop producers have used large amounts of commercial fertilizer
and organic nutrients, but the concern over run off
and leaching has prompted the promotion of nutrient
management practices that minimize nutrient loss.
The share of acres receiving fertilizer, application rates for
primary nutrients (nitrogen, phosphate, and potash), and nutrient
management practices on major field crops (corn, soybeans, wheat,
and cotton) remained fairly stable over the 1990s. However, fertilizer
prices, especially for nitrogen, have been volatile and have risen
rapidly in recent years. Despite increased fertilizer prices and
growing concern about environmental risks from fertilizer use, the
use of nutrient management practices on major crops has changed
little since the early 1990s.
Fertilizer Use Nationally and by Region
U.S. commercial fertilizer use peaked in 1981 at over 23 million
nutrient tons, but has exceeded 22 million tons seldom since then
(fig. 4.4.1). The decline in (principal crop) planted acreage since
1998 likely accounts for part of the falloff in fertilizer since
then. The mix of crops planted each year also influences aggregate
fertilizer use. Corn and wheat acreage, which consumes the most
fertilizer among all crops, has dropped since 1998, and fertilizer
use on soybeans has only partially offset the falloff.
Consumption of individual nutrients has been variable over the
last several years, although annual use through 2003 is below levels
reported in the late 1990s (fig. 4.4.2). For example, nitrogen use
dropped noticeably in 2001 and remained below 12.5 million tons
from 2000 through 2003. Annual phosphate and potash use has demonstrated
similar variability over the last several years. The regional distribution
of fertilizer use has remained stable, with the Corn Belt, Northern
Plains, and Lake States the leading regions because of high concentrations
of corn, wheat, and soybean acreage (fig. 4.4.3).
Fertilizer Use by Major Crops
The four major U.S. crops—corn, wheat, soybeans, and cotton—currently
account for about 60 percent of principal crop acreage and receive
over 60 percent of all nitrogen,
phosphate, and potash used in the United States. Corn typically
accounts for over 40 percent of all commercial fertilizer consumed,
followed by wheat (about 10 percent), soybeans (about 5 percent),
and cotton (5 percent). However, these shares vary from year to
year (and by nutrient) due to the mix of crops planted, share of
acreage treated, and application rates.
The share of acreage treated and application rates were fairly
stable over 1990-2003, although cotton exhibited greater variability
(table 4.4.1). For example, 97-98 percent of corn acres received
nitrogen fertilizer in most years (excluding the high and low years),
while phosphate was applied to 79-84 percent of the acres. Similarly,
for most crop/nutrient combinations, the amount of nutrients applied
each year varied 5 pounds or less. This relative consistency in
production practices stems from modest changes in factors like the
ratio of prices received to fertilizer prices paid by farmers, agronomic
relationships, seed traits, public policies, and producer education.
Table
4.4.1—Share of acres treated and application rates, 1990-2003,
by major crop and nutrient1
Nitrogen
Phosphate
Potash
Corn
Share
of acres treated (%)
97-98
79-84
65-73
Application
rates (lbs/treated acre)
127-136
56-59
80-84
Cotton
Share
of acres treated (%)
79-86
49-66
34-53
Application
rates (lbs/treated acre)
84-100
44-49
48-76
Soybean
Share
of acres treated (%)
13-18
21-26
25-29
Application
rates (lbs/treated acre)
22-25
47-50
76-88
Wheat
Share
of acres treated (%)
80-88
54-63
18-20
Application
rates (lbs/treated acre)
63-68
32-35
37-41
1Excludes
values for high and low years which may have been influenced
by such factors as number of States surveyed, weather, commodity
and/or fertilizer prices, etc.
Source: ERS from NASS data on Agricultural
Chemical Usage
While nutrient use, in general, has been stable since 1990, modest
trends for some crop/nutrient combinations are apparent. For example,
the share of corn acres treated with phosphate and potash declined
slightly, while the share of cotton acres treated with potash rose along with application rates. The share of wheat acres treated with
nitrogen likewise rose, as did application rates; these increases rose for wheat, which may have been due
to the decline of wheat acreage in several arid States in the Mountain
and Plains regions. Also, a significant price increase for fertilizer,
especially nitrogen, in 2001 and 2003 likely dampened nutrient use
during those years.
Fertilizer application rates vary widely by crop and nutrient,
and are influenced by yield response, climate, and fertilizer/commodity
prices (fig. 4.4.4). Among the major field crops, annual application
rates for all nutrients are typically highest for corn, but rates
vary widely for other crops and nutrients. Certain specialty crops,
like fall potatoes and rice, consume more fertilizer per acre than
the major crops, but are planted on far fewer acres.
Prices of Major Fertilizer Products
Since 1990, the primary fertilizer products purchased by farmers
have exhibited much different nominal
price patterns (fig. 4.4.5). Potash prices, in the form of potassium
chloride (KCl), have been stable. A major source of phosphate, diammonium
phosphate (DAP), has demonstrated much more price variability—peaking
in 1995 at near-record levels, declining steadily through 2002, then rising again in 2003 and 2004. Nitrogen product prices, such as those for
anhydrous ammonia, have shown the greatest volatility during the
last several years—a spike in 1995, a fall to historically
low levels by 1999 and 2000, record-high prices in 2001, followed
by a large decline in 2002 and recovery in 2003. Fertilizer markets
are influenced by trade, raw material prices, and planted acres.
Potash is largely an imported product, whereas the United States
exports large amounts of phosphate; both of these markets are influenced
by international demand and supply factors. Natural gas is the primary
raw material for nitrogen fertilizers, comprising 75 percent or
more of their cost of production. During 2001 and 2003, nitrogen
fertilizer prices rose dramatically in concert with natural gas
prices. In response to higher prices in the United States, nitrogen-based fertilizer
imports have increased significantly in recent years.
While most economic studies indicate that farmer response to fertilizer
price changes is fairly inelastic (i.e., relatively unresponsive
to price changes), farmers can make some adjustments in fertilizer
use when faced with dramatically higher prices. Shifting to a crop
that needs less fertilizer, reducing application rates, and adopting
improved nutrient management practices are all options. When the
2001 ARMS
asked corn producers how they responded to higher nitrogen fertilizer
prices, about one-third reported that most of their nitrogen had
been contracted at a pre-determined price, so they were not affected
by increased fertilizer prices. Another 11 percent reported reducing
application rates or changing nutrient management practices. The
remaining producers, who did not change their nutrient use or management,
tended to operate smaller farms and use less nitrogen per acre.
Nutrient Management Practices for Major Crops
The use of nutrient management practices in crop production can
have economic and environmental implications (2003
AREI and Agricultural
Chemicals and Production Technology Briefing room). For example,
using soil tests to assess the need for additional commercial fertilizer
or manure applications can reduce fertilizer costs and losses to
the environment. Applying nitrogen inhibitors to delay the release
of nitrates from ammonium fertilizers until later in the growing
season may reduce nitrate leaching. If nitrogen fertilizer products
are broadcast, incorporating the product into the soil may reduce
nitrogen losses through volatilization. Applying nitrogen at strategic
times (i.e., split applications), such as after planting when crop
demand is greatest, may reduce the risk of nitrogen loss through
leaching or volatization.
In general, ARMS data indicate
that the use of most nutrient management practices has remained steady from year to year
for the major crops. Between 1996 and 2000, soil testing was
conducted
on 40-50 percent of the acres planted to corn and cotton—the
crops with the largest fertilizer use per acre. On soybeans and
wheat, only about 30 percent of the planted acreage was soil tested.
No clear soil-testing trends were reported for any of these crops.
Similarly, with the possible exception of winter wheat and corn,
nitrogen management practices, such as fall application, split
application,
and incorporation of broadcast materials, showed little consistent
change over time. The share of corn acres with all nitrogen broadcasted
without incorporation declined from about 15 percent to 9 percent
between 1996 and 2000. The share of winter wheat acres with split
nitrogen application increased, as did non-incorporated broadcast
acres. Nitrogen inhibitors were used on 7-9 percent of U.S. corn
acreage from 1996 to 2000, but were used on less than 2 percent
of other major crops. As with the share of acres treated and application
rates, nutrient management practices tend to change little from
year to year.
Programs and Regulations That May Affect Fertilizer Use
and Management
Nitrogen and phosphorus have been identified as major
contaminants of U.S. surface and ground water (See AREI
Chapter 2.2). The U.S. Geological Survey (1999) estimates that about
90 percent of nitrogen and 75 percent of phosphorus contaminants
originate from nonpoint sources, with the remainder from point sources.
Agricultural point sources include livestock operations, while nonpoint
sources include fertilizers and animal waste applied to cropland.
Given the concerns over water quality, a number of voluntary and
nonvoluntary programs have been promulgated to address agricultural
nutrient use and management. Most Federal programs are directed
at encouraging producers to alter cropping or nutrient application
practices. These programs range from nutrient use regulations affecting
producers of large confined animal operations to voluntary cost-sharing
and educational/technical assistance programs available to all producers.
Livestock producers who meet the criteria for a Concentrated Animal Feeding Operation (CAFO)
must formulate a nutrient management plan for animal waste disposal
that includes recordkeeping, and in certain cases, limits on the
application of other sources of nutrients, such as commercial fertilizer.
The Environmental Quality Incentives Program (EQIP) and the Conservation
Security Program (CSP) provide cost-sharing to producers who adopt
environmentally friendly practices, including a nutrient management
plan. Such plans focus on managing the amount, source, placement,
and timing of fertilizers and animal manure to minimize
pollution on cropland. Other Federal programs include Conservation
Compliance, which reduces nutrient losses associated with soil erosion,
the Conservation Reserve Program (CRP), retired over 34
million acres of environmentally sensitive cropland under 10 to 15-year contracts, and Conservation
Technical Assistance (CTA). More recently, the Conservation
Reserve Enhancement Program (CREP) and the Wetland Reserve Program
(WRP) have been implemented to remove environmentally sensitive
land from crop production (i.e., buffers, filter strips and wetlands). (See
AREI Chapters 5.1, 5.2,
5.3, and 5.4.)
References
Association of American Plant Food Control Officials (2003). Commercial Fertilizers, University of Kentucky, Lexington,
KY.
U.S. Geological Survey (1999). The Quality of Our Nation's Waters: Nutrients and Pesticides. U.S. Geological Survey Circular 1225.
