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Northcentral
Don't let nutrient deficiencies and depleted soils creep up on you. Many people
are unaware of the quantities of phosphorus (P) and potassium (K) removed from
the field with a crop harvest. The most recent USDA reports of average U.S.
yields for alfalfa, corn, wheat, and soybeans are 3 tons/A, 137 bu/A, 42 bu/A,
and 38 bu/A, respectively. Considering these crops and yield levels, using
coefficients published by PPI, corn and alfalfa remove the most P per acre,
at 60 and 52 lb P2O5/A, respectively.
Soybeans come in third at 31 lb P2O5/A.
Wheat is fourth, with a U.S. average removal of 21
lb P2O5/A. By far, K removal from fields is highest
with alfalfa, at an estimated U.S. average of 209
lb K2O/A.
Soybeans come in a distant second, removing
an average of 53 lb K2O/A. Average K removal by corn
and wheat follow with an estimated 40 and 15 lb K2O/A,
respectively.
Because the actual amounts of P and
K removed can vary with different conditions and
yield levels, it is best to take a few grain or forage
samples and have them analyzed to determine nutrient
content.
Combine this knowledge with yield records
to calculate how much P and K are being removed from
your fields. Attention paid to this aspect of nutrient
management will help prevent nutrient deficiencies
and depleted soils from catching you unaware.
Northeast
Cool and wet weather in the month of May delayed both
emergence and planting of corn and soybeans. The rains,
however, were not sufficient to recharge groundwater
in drought-stricken southeast Pennsylvania. The cool weather has favored growth
of forage grasses and cereal crops, but the earlier swings in temperature have
resulted in some variable fields. First-cut forages contain a higher-than-usual
ratio of grass to forage. Remember that potassium (K) helps maintain the percentage
of legumes, and that following first cut is a great time to apply.
Cool weather means delayed release of nitrogen (N) from manures and previous
crop residues. A soil nitrate test at this time will be very helpful in determining
the availability of soil N for corn. Tests in Ontario are indicating that this
year's nitrate levels are slightly lower than average, and that manure N credits
may not be as high as expected. Results vary strongly from field to field,
however, so do the test yourself.
Northern Great Plains
As grain legumes, field peas are capable of fixing most of their own nitrogen
(N). However, the crop is a heavy user of phosphorus (P) and potassium (K). Peas
remove at least 0.62 lb P2O5/A of and 0.64 lb K2O/A in the seed. Many farmers
in western Canada receive conflicting messages on the benefit of fertilizing
peas. Given the large area of soils that test less than 20 parts per million
(ppm) of P in western Canada, the possibility that field pea yields may be limited
by a P deficiency is a concern.
To help agronomists working with farmers address the issues of P management
in field peas, Dr. Adrian Johnston, Western Canada Director with PPI/PPIC,
has worked with researchers to summarize the findings of two research projects.
Both of these projects, which involved a large number of field trials, concluded
that soils testing less than 27 lb P/A (14 ppm) had a 50 percent chance of
responding to P fertilization. Crop responses were recorded with P rates as
high as 60 lb P2O5/A, however, the majority of responsive trials achieved maximum
yield with 30 lb P2O5/A. This regional summary will help guide Certified Crop
Advisers (CCAs) who are helping their farm clients optimize the use of inputs
in field pea production.
Great Plains
Much of the western and southern portions of the Great Plains region remain under
drought conditions. According to the Palmer Drought Index, eastern Colorado and
western Kansas are in an extreme to moderate drought. Much of western Oklahoma
and the Texas Panhandle, Coastal Bend, and Rio Grande Valley also remain dry.
These areas will need rain soon to produce respectable dryland yields. Moisture
conditions in the remainder of the region are near normal.
As the season progresses remember that in-season
fertilization of soybeans can be a profitable practice under conditions of
high yield potential. The soybean is a nutrient dense, high protein seed.
Consequently, nutrient requirements for high yield soybean production are
rather high. One bushel of soybeans contains more than 3.5 lb nitrogen (N),
0.9 lb P2O5, and 1.3 lb of K2O. Adequate phosphorus (P) and potassium (K)
fertility are essential in high yield soybean production. Additionally, supplemental
late season N fertilizer may significantly improve soybean yields in high
yield environments. Past research has shown that the period of peak N demand
in soybean production is during pod fill, or growth stages R1 to R6. Fixed
N alone may not be sufficient to meet the crop's need during this period.
Therefore, supplemental soil N may be necessary for maximum soybean yield.
Research in Kansas has shown that where other factors such as water and P
and K fertility are not limiting, application of N during the period of peak
demand (pod fill) significantly increased soybean yield in six out of eight
site years. The average yield increase from 20 lb N/A was about 7 bu/A… enough
to boost profit by over $25/A.
Midwest
A complete nutrient management plan for a cropping system must include the needed
nutrients for all of the crops in the rotation. As the crop mix changes, adjustments
will be needed to be sure all crops are "well-fed".
The 2001 PPI Soil Test Summary Update report showed
a large percentage of samples analyzed by North American
commercial and public soil testing laboratories were
indicating phosphorus (P) and potassium (K) levels
below the optimum, indicating a need to increase fertilizer
applications to maintain productivity. Part of this
deficit can be attributed to changes in crop rotation
that have resulted in accelerated removal of nutrients
from the soil, with no compensatory changes in fertilizer
application.
Many of the low or medium tests are likely from within
fields that are well-managed on a field-average basis,
but include areas that are below optimum. As long as
field-average recommendations are followed, these areas
will not be corrected, because applications of fertilizer
will be insufficient to build soil tests. Only with
site-specific management can corrective applications
be made.
Figure 1 shows the K requirement
for an Indiana field under site-specific management,
using management zones based on soil type and yield
levels. Field average soil tests showed no K was
needed, but when zone management was used, the same
recommendation procedure called for an additional
10 tons of 0-0-60 needed on the 140 acre field. This
represents the missed opportunity for yield…and fertilizer sales…under
field-average management. Site-specific management
can help capture these profit opportunities for even
well-managed fields. Realizing that potential increase
depends upon making a commitment to invest the time
and money to gather the information and to formulate
and implement the improved management plan.
Figure 1. Potassium recommendations for an Indiana
field under zone management.
Southeast
Wet and cool conditions persisted in the western half
of the region, while drought prevented timely planting
in some states in the eastern half. In parts of the Mississippi
delta, soybeans were replanted because of heavy rains.
Thrips, grasshoppers, and other insects stressed cotton
and soybeans. Intended corn plantings in some areas were
shifted to soybeans because of unfavorable planting weather.
The contrasting moisture conditions in the west and east also affected pasture
growth and fertilization. Hay was being mowed and baled where timely rains
were received. Soil moisture remains short to very short in much of the eastern
half of the region, even where some rains have fallen recently.
Some corn and sorghum fields were being irrigated in the western half of the
region. Cotton was being irrigated in some fields in Georgia to assist with
stand establishment.
Midseason nitrogen (N) is being applied to rice. Corn and cotton fields are
being side-dressed in many areas.
Wheat harvest has begun, and some soybeans are being planted behind wheat.
Soybean emergence is continuing in several states. Wheat yields appear to be
down somewhat in the eastern portion of the Southeast region, but not drastically.
Fruit crops and truck crops appear in fair to good
condition. Several good rains in the Florida citrus area have helped improve
the crop condition. According to the Florida ag statistics service, "Rainfall
curtailed the harvesting of some crops for a day or two. Tomato harvesting
is very active in the Quincy area. Watermelon picking is very active in the
northern Peninsula and Panhandle, as weather permits. Supplies of most vegetables
are declining rapidly as harvesting moves to northern states. Other vegetables
and melons available include potatoes, cantaloupes, okra and very light supplies
of squash, cucumbers, eggplant, and peppers."
Peanut acreage was all planted in Alabama, Georgia, Florida, and North Carolina
by early June and is generally rated in good condition.
In general, crop conditions across the southeast are rated as:
pastures and hay meadows
• fair to good
soybeans
• fair tending toward good
cotton
• fair to good, with most field beginning to square (set flower buds)
rice
• generally good, but some fertility problems (zinc deficiency, poor tillering,
possibly related to inadequate phosphorus nutrition) appearing in some fields
Crop conditions are generally improving with warmer temperatures, where soil
moisture is adequate. Framers and their advisers should be watching crop development
closely, to detect any potential nutrient shortages. If deficiency symptoms
are detected before too far into reproductive growth, there is still reasonable
opportunity to apply nutrients like N, potassium and sulfur (in the sulfate
form).
Because temperatures are warmer now, growers will need to be sure they use
best management practices for incorporation of urea and urea-containing fertilizers
to minimize the risk of ammonia loss. Rainfall or irrigation within about two
days after application can help to reduce the risk of ammonia loss. The risk
of loss is likely greater in no-till and pastures where significant crop residues
may be present on the soil surface.
West
The western United States produces a wide variety of high-yielding, excellent
quality crops. This diversity has aided growers in avoiding the full impact of
the economic downturn experienced for many commodities over the past number of
years. None-the-less, many growers are affected and there continues to be considerable
concern about the agricultural economy entering 2002. In sharp contrast to the
2001 season, the supply of available water for irrigation and hydroelectric power
appears to be much improved. Winter rains and snow are running above normal.
Cost of electricity has declined as additional power plants have come on-line.
Fertilizer management issues of current concern continue to include efficiently
managing nitrogen (N) inputs, both inorganic and organic, to avoid nitrate
accumulation below the rooting zone. Improved soil test procedures and in-season
application techniques are being evaluated and promoted by the research community.
The Salinas Valley has been a focal point of such studies in California. Related
to the growing dairy and other animal industries in the west, there is concern
about manure management related to excessive accumulation of phosphorus (P
loading) in the soil as well as N. The Natural Resources Conservation Service
(NRCS) has implemented P management guidelines for large CAFOs (confined animal
feeding operations) utilizing primarily the P-Index concept in most western
states. Guidelines for California were completed at the end of 2001 and are
currently being field-tested.
Increasing acreage is moving to low pressure irrigation systems (drip or micro-sprinkler)
for trees, vines and vegetables which meter water and fertilizer very efficiently.
This is in response to cost of water, likelihood of limited future supplies,
and environmental (leaching) issues. Continued research is needed to determine
how to maximize the positive interactions between nutrients and different irrigation
systems. Regulations were recently implemented in California to govern content
of metal contaminants in P and micronutrient fertilizers. The metal contaminants
being regulated are cadmium (Cd), arsenic (As), and lead (Pb). Washington state
implemented similar regulations several years ago.
Some western dealers have initiated site-specific fertilizer management programs.
However, these programs are still in their infancy compared to the Midwest.
Progress is slowed by the diversity of crops in the west and the continuing
tight economy. Grain, potato, and tomato harvesters utilizing yield monitors
are currently in commercial use.
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