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

FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
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

Trending Articles

Crop InputsPlatform Specialty Products To Acquire Arysta LifeScience
October 20, 2014
Once the acquisition is complete, Platform Specialty Products will combine Arysta LifeScience with previously acquired companies Agriphar and Chemtura Crop Solutions. Read More
Seed/BiotechMonsanto Offers New Support For Ferguson, Area Communities
October 8, 2014
Monsanto Co. has committed $1 million in new support for several collaborative efforts in Ferguson, MO, and surrounding communities in North St. Louis County. Read More
Seed/BiotechUnapproved Genetically Modified Wheat Found In Montana
October 3, 2014
USDA reports that one year after discovery of Monsanto's unapproved wheat in a single Oregon field disrupted U.S. wheat export sales, the GMO wheat has again been found in Montana. Read More
Equipment2014 Product Of The Year Voting
September 19, 2014
The deadline to vote for the 2014 CropLife IRON Product of the Year is October 31. Please cast your vote today to help us determine the winner. Read More
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
CropLife 100CHS To Build $3 Billion Fertilizer Plant In North Dakota
September 5, 2014
The fertilizer plant in Spiritwood will be the single largest investment in CHS history, as well as the single largest private investment project ever undertaken in North Dakota. Read More

Latest News

StewardshipFlorida’s 4R Advocate Keeps Improving
October 24, 2014
Florida farmer Alan Jones uses the 4R principles of nutrient stewardship as the core of his fertility program, which allows him to maximize production and keep costs in check. Read More
Seed/BiotechMonsanto Named One Of The World’s Best Multinational …
October 23, 2014
Monsanto ranked No. 8 in the world’s largest annual study of workplace excellence that identifies the top 25 best multinational companies in terms of workplace culture. Read More
Crop InputsArysta Hires Former Agri-Chem, CPS Employee For Delta S…
October 23, 2014
New Territory Sales Manager Mark Peel’s primary role will focus on working with growers regarding fungicides in Louisiana, Mississippi, Arkansas and Tennessee. Read More
CropLife 100GROWMARK Announces Appointments In Plant Food Division
October 22, 2014
GROWMARK, Inc. has announced the three key staff changes in its Plant Food Division. Read More
CropLife 100GROWMARK Appoints New VP Of Finance And Risk Management
October 22, 2014
Wade Mittelstadt has been named GROWMARK Vice President, Financial and Risk Mangement, effective December 1, 2014. Read More
FungicidesEPA Approves BASF In-Furrow Corn Fungicide
October 22, 2014
Field trials show Xanthion In-furrow fungicide provides more rapid emergence, extended residual control and improved seedling health than untreated crops. Read More
EquipmentAgraScout App Available At No Cost To Universities
October 21, 2014
AgraScout, a fast and easy to use mobile crop scouting app, is now available at no cost to University students, Read More
LegislationNew Farm Bill Program To Provide Relief To Farmers Affe…
October 21, 2014
The USDA has implemented a new Farm Bill initiative that will provide relief to farmers affected by severe weather, including drought. Read More
ManagementGreenfield Scholars Program Aims To Sustain Agronomy Wo…
October 21, 2014
The program encourages talented students to study agronomy, crop and soil sciences while cultivating networks to develop the necessary workforce to sustain the profession. Read More
Paul SchrimpfPrecision Ag: Taking It To The Hill
October 21, 2014
A new coalition took the good news message of precision agriculture to Washington, DC, last month. Read More
ManagementUSDA Awards $18 Million In Small Business Research Gran…
October 21, 2014
The grants will provide high quality, advanced research and development that will lead to technological innovations and solutions for American agriculture. Read More
FertilizerCF Industries Terminates Merger Discussions With Yara I…
October 21, 2014
CF Industries Holdings and Yara International have terminated their discussions regarding a potential merger of equals transaction. Read More
Seed/BiotechSyngenta Ranked A Top 10 Biotech Employer For Third tim…
October 20, 2014
Syngenta ranked in the top 10 among the world’s top biotech employers, according to an annual survey conducted by Science magazine. Read More
CropLife 100Wheat Growers Break Ground For New Facility At Kennebec
October 20, 2014
Wheat Growers has broke ground for a state-of-the-art shuttle loader grain handling, fertilizer and agronomy facility in Kennebec, SD. Read More
FertilizerVerdesian Life Sciences Signs Agreement With Los Alamos…
October 20, 2014
Verdesian Life Sciences has signed a licensing agreement with Los Alamos National Laboratory to develop and market LANL’s latest nitrogen enhancement technology for plants. Read More
MicronutrientsStoller Group Announces Groundbreaking At New Office Bu…
October 20, 2014
Jerry Stoller, founder and president of Stoller Group, announced the groundbreaking at the site of the company’s future headquarters in Read More
Crop InputsBioSafe Systems Opens New Production Facility In Nevada
October 20, 2014
BioSafe Systems has completed construction of a state-of-art production facility in Sparks, NV, for its line of activated peroxygen products. Read More
Crop InputsPlatform Specialty Products To Acquire Arysta LifeScien…
October 20, 2014
Once the acquisition is complete, Platform Specialty Products will combine Arysta LifeScience with previously acquired companies Agriphar and Chemtura Crop Solutions. Read More