Fall Fertilization Strategies

Minimizing yield-limitations caused by crop nutrient deficiencies is top of mind for soil testing and fertilizer decision makers every autumn. Collecting soil samples after harvest is a good place to start. There are several ways to collect soil samples, from random sampling (collecting multiple cores from different areas of the field and creating a composite) and grid sampling (based upon GPS location) to zone sampling (based upon delineated management zones). There are pros and cons to each method.

Types of Soil Sampling

•  Random
Pro:
Inexpensive and easy to collect
Con: Lack of site-specific information. No variability in measurement. Possible bias due to extreme variation.

•  Grid
Pro:
Site-specific variable-rate capable. Possible to conduct at multiple resolutions.
Con: Expensive. Technologically advanced. Labor intensive.

•  Zone
Pro:
Based on intuitive information (yield maps, soil map, topography). Easy to collect. Variable-rate capable.
Con: Can be expensive based on the number of zones. Assumes soil-based yield limiting factors are uniform across zones.

The soil test report is only as good as the sample provided to the lab for analysis, so no matter the approach — ensure soil samples are administered correctly. Collect samples to the same depth when creating a composite, ensure adequate sample volume to accurately represent average soil nutrient levels, and mix composites thoroughly before collecting samples and depositing to soil bags. These are critical first steps along the nutrient management decision chain.

After submitting the samples to a reputable lab and receiving the results, the next step in the decision chain is to determine which nutrients and what quantity should be applied to ensure that soil levels maximize productivity. The natural place to start is to evaluate the soil pH level. Make certain that soil pH falls within optimum ranges for the crops to be grown. In general, legumes require a slightly higher soil pH to maximize production than grasses. If your soil pH level is below the optimum range, your soil may require neutralization.

When applied to soil, lime neutralizes soil pH, but is among the most expensive soil applications to be made in a single production year. Since adding lime to the soil can be critical to maximizing crop yields next spring, the expense should be considered a good investment.

Soil pH readings only indicate whether or not lime is needed, but lab-conducted buffer pH or lime index tests will determine how much lime is required to optimize soil pH. These tests will also determine the quality and lime grind fineness appropriate for application to fields. University specialists and local experts familiar with lime quality are the best consultative resources for lime application.

Evaluating P And K Levels

Table 1
Grain and stover/straw nutrient removal rates for common agricultural crops.
Crop Grain*  Stover/Straw*
P2O5
removal
  K2O
removal
P2O5 removal   K2O
removal
 
Corn
 
0.38
lb/bu
 
 
0.27
 
 0.16
 lb/ton
 
 
 1.10
Soybeans 0.84   1.30  8.80    37.00
Barley 0.40   0.32  —    —
Canola 0.91   0.46  —    —
Wheat
 
0.60
 
 
lb/bale
0.34
 
 3.30
 
 
 
 24.00
 
Cotton 14.00   19.00  —    —
*-IPNI      

After assessing lime needs, evaluating phosphorus (P) and potassium (K) levels is essential to determine the soil’s ability to supply nutrient levels throughout growing season.

P is required to ensure adequate energy for crops and is critical to the formation of genetic material as the crop grows and develops. K is essential for drought tolerance, multiple enzyme reactions and crop disease resistance. As different crops have different critical P and K soil test levels, lab results will also reveal information about where test results are relative to crop needs.

P and K behavior in soil is dramatically different than mobile nutrients like nitrogen (N) as they can actually be built up in most soils. While this tendency can result in fertilization for more than one crop year, it does not mean continual crop production without nutrient replenishment should be the norm. This is an unsustainable practice that can dramatically decrease crop productivity.

Significant depletion of P and K levels can also be quite costly when attempting to bring soil test levels back in line for crop production, as equivalent or greater levels of these nutrients will have to be applied to see a noticeable reserve accumulation in the soil.

Beyond Soil Testing

Other factors can also be monitored to determine how much fertilizer will be required to maintain P and K soil test levels. Crop removal can either be monitored in a site-specific manner with the use of a yield monitor, or by simply monitoring and logging load weights when delivering grain. All that is required is a crop yield estimate to provide insight into the amount of P and K removed from the soil.

Crop P and K removal can be estimated using crop yield and crop removal values from Table 1 above. For example, a 200-bushel corn crop, where only grain is removed, will remove 76 (200 x 0.38) and 54 (200 x 0.27) pounds of P2O5 and K2O per acre, respectively. Corn and wheat growers who remove stover and straw, respectively, must make sure an estimate of nutrient removal in the stover/straw is included when determining the total P and K removed. Estimates of stover and straw tonnage, as a function yield, are provided in Table 2.

Table 2
Stover/Straw yiuelds based upon grain yields and an assumed harvest index of 0.55 for corn and wheat.
Crop Grain yield,
bu/acre
Stover/Straw yield,
ton/acre
Corn 150 3.4
Corn 200 4.6
Wheat 60 1.5
Wheat 90 2.2

Fall N Application Considerations

N applications planned for this fall also require consideration. Soil temperatures should be below 50°F to minimize conversion of supplied ammonia to nitrate. The same guideline surrounding soil temperature also applies to the application of DAP or MAP. Recent research has shown a significant amount of the N supplied with MAP, DAP or ammonium sulfate may be unrecoverable in the next corn crop-based on soil temperature and rainfall pattern in early spring. Nitrification inhibitors are more likely to reduce N loss in fall-applied systems because fall N application has the highest N loss potential. The use of N in the fall should therefore be considered.

Remember — the key to optimizing crop production is ensuring adequate nutrient availability. Spending a little time evaluating soil test reports and determining crop nutrient removal when making fertilizer decisions will go a long way in ensuring favorable production for years to come.

Leave a Reply

Fertilizer Stories

Aerial view of the West Fertilizer explosion site
FertilizerFertilizer Companies Blame City For West, TX, Explosion
August 6, 2014
El Dorado Chemical Co. and CF Industries contend the city failed to properly train the first responders and had insufficient protocols in place to battle the April 17, 2013, blaze at West Fertilizer Co. that triggered the explosion. Read More
FertilizerThe Fertilizer Institute: New President, Renewed Energy
February 3, 2014
Chris Jahn relishes the opportunity to lead the organization through the challenging times ahead. Read More
FertilizerA New Cycle For Fertilizer Demand
January 2, 2014
Changes in the corn market could have a major impact on the crop nutrients sector in 2014, say experts. Read More
FertilizerOSHA Hammers West Fertilizer With Over $100K In Fines For April Explosion
October 10, 2013
The Occupational Safety and Health Administration is fining the parent company of the West Fertilizer plant, Adair Grain Inc., $118,300 for 24 violations. Read More

Trending Articles

ManagementExpert To Discuss Farmland Value, Rent At Farm Science Review
August 18, 2014
While cropland values in Ohio increased in the past two years, they have remained flat in 2014, declining in some cases, according to an Ohio State University agricultural economist. Read More
EquipmentAdvance Your Technology IQ At MAGIE
August 13, 2014
The Midwest AG Industries Exposition (August 20-21) is the place you need to be to see, study and evaluate how new advances in the equipment, operations, crop protection and fertility sectors can help your business prosper. Read More
HerbicidesScouting Key To Next Season’s Soybean Herbicide Program
August 12, 2014
When growing soybeans, growers need to think ahead to stay one step ahead of weeds. That means examining weed threats and evaluating which herbicides work best. Read More
StewardshipMichigan Agriculture Leaders On Toledo Water Ban: We Want To Be Part Of The Conversation
August 8, 2014
Leaders of Michigan agricultural organizations said Thursday that the government should not have a “knee-jerk reaction” based on last weekend’s water ban in Toledo due to fertilizer run-off in Lake Erie. Read More
CropLife 100BRANDT Acquires Lemon Ag Services
August 4, 2014
The acquisition of Lemon Ag fits BRANDT’s aggressive corporate strategy of providing superior agronomic advice and services for customers in central Illinois. Read More
Eric SfiligojThe Resurgence Of Crop Protection
August 4, 2014
Plenty of new offerings over the next few years should see a rebirth for the crop protection products category in terms of market share. Read More

Latest News

Crop InputsBASF Is Betting On A Bright Agricultural Future
September 1, 2014
The crop protection products giant is gearing up for a busy time in agriculture by investing in both product production and development over the next couple of years. Read More
Eric SfiligojAn Erie Feeling For Ag
September 1, 2014
Plenty of water issues have been in the news lately, including the continuing drought in California. Read More
CropLife 100Pinnacle Acquires California-Based Retailer
August 29, 2014
Pinnacle Agriculture Holdings will acquire Kerman Ag Resources, Inc., which will operate under Pinnacle's Performance Agriculture brand. Read More
Allied Cooperative Grain Plant
ManagementArcadia Co-op To Merge With Allied Cooperative
August 28, 2014
Allied Cooperative has announced that members of Arcadia Co-op voted in favor of a merger with Allied Cooperative, paving the way for the consolidation which will be effective on December 1, 2014. Read More
InsecticidesBioinsecticide VENERATE Now Registered In California
August 27, 2014
Marrone Bio Innovations' VENERATE is a new tool to help California growers control crop-damaging insect pests, fight the development of insect resistance and reduce pesticide residues on fruits and vegetables. Read More
CropLife 100Two Iowa-Based Ag Co-ops To Merge
August 27, 2014
The Board of Directors and management of United Western Coop, Missouri Valley, IA has completed a merger with Heartland Co-op, West Des Moines, IA, effective September 1, 2014. Read More
FertilizerKoch Expands AGROTAIN Nitrogen Stabilizer Portfolio
August 26, 2014
Koch Agronomic Services, LLC has added two new innovative nitrogen stabilizers to the AGROTAIN product family – AGROTAIN ADVANCED and AGROTAIN DRI-­MAXX. Read More
Seed/BiotechDuPont To Build Two Seed Treatment Centers
August 26, 2014
DuPont has announced construction on two state-of-the-art centers dedicated to developing and testing seed treatment formulations, applications and seed handling techniques in an important step toward bringing new solutions to growers. Read More
Seed/BiotechLoveland Products Acquires A Controlling Interest In Ag…
August 26, 2014
Loveland Products, a subsidiary of Agrium , has announced the company has acquired a controlling interest in Agricen, a Dallas-area agricultural biotechnology company delivering biochemical-based products for efficient and sustainable plant nutrition. Read More
StewardshipUp Close Look At The 2014 Environmental Respect Award W…
August 25, 2014
The 2014 Environmental Respect Award winners were honored recently at the 24th annual event in Wilmington, DE. Read More
Eric SfiligojAg Science Rejection Carries Consequences
August 25, 2014
As innuendo and fear dog the regulatory process, agriculture can’t get the new tools it needs to combat world hunger. Read More
LegislationFarmers Dismayed As New Farm Bill Dumps Direct Payments
August 25, 2014
The threatened end of cash subsidies to the nation’s row crop farmers dates back through at least the last two iterations of national agriculture policy legislation. Read More
MAGIE 2014 ShowStopper
EquipmentJohn Deere Again Wins MAGIE ShowStopper Award
August 25, 2014
For the second consecutive year, John Deere was honored at the Midwest AG Industries Exposition (MAGIE) for its new R4045 sprayer. Read More
CropLife 100GROWMARK CEO To Retire
August 22, 2014
GROWMARK chief executive officer Jeff Solberg has announced his retirement effective September 15, 2014. Read More
InsecticidesDuPont’s Prevathon Approved For Dry Beans
August 22, 2014
DuPont Prevathon insect control powered by Rynaxypyr has received EPA registration for foliar use on dry bean crops, including dried shelled peas and beans. Read More
ManagementNCGA DuPont New Leaders Program Enters Sophmore Season
August 20, 2014
The National Corn Growers Association and DuPont are pleased to announce the second year of the NCGA DuPont New Leaders Program. Read More
FungicidesVerdesian Links Up With Mitsui, Hokusan
August 20, 2014
Mitsui Chemicals Agro, Inc., and Hokusan Co., announced the signing of an exclusive licensing agreement allowing Verdesian Life Sciences global access to its patented technology for suppressing mycotoxin contamination in wheat and barley. Read More
SprayersUniversity Of Illinois Introduces New Spray App
August 18, 2014
University of Illinois Extension has released a new smartphone app for making sprayer-related calculations. Pesticide Spray Calculator, or Spray Calc, Read More