Get the Most Out of Your Fertilizer

As the weather starts to warm up, farmers everywhere are getting restless to start work in the field. Putting seed in the ground is at the top of the to-do list for a majority of farmers at this point in time. In the spring it is easy to put other aspects of a cropping system to the side. One of the most important inputs in any cropping system is fertilizer. Producers should have a plan for nutrient management before the seed goes into the ground. However, due to unexpected events, the initial plan may change throughout the growing season. It is important to have a backup plan in case this happens.

When planning for nutrient management, it is helpful to analyze the four R’s of nutrient management. The four R’s refer to the right source, right rate, right time, and right place. Sticking to the four R’s allows producers to utilize their inputs more efficiently, while minimizing their environmental impact.

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Right Source

The right fertilizer source can vary based on the crop, crop rotation, tillage, and soil characteristics. The fertilizer needs to meet the nutrient needs of the crop. Fertilizers can come in solid and liquid forms. Each form has its own benefits. Nutrients in liquid fertilizers are dissolved, or suspended, in water and are readily available to the plant at the time of application. Liquid fertilizers are great for side dressing or starter applications. Dry fertilizers are excellent for preplant applications. Controlled release nitrogen fertilizers can be used in wet fields that are prone to denitrification, leachable soils, and areas that will need a constant nitrogen supply. Blended fertilizers allow producers to fine tune their nutrient inputs by controlling the levels of nitrogen (N), phosphorus (P), and potassium (K) in the blend. Blends must be properly mixed and handled to ensure a uniform application.

Right Rate

Choosing the right fertilizer rate can save the producer money on input costs and decrease the amount of nutrients leaving the soil through runoff and leaching. Yield and nutrient intake are directly related. The goal is to provide the crop with enough nutrients to produce an economic yield. For corn, nitrogen rates are typically based off of potential yield. Generally, corn requires 0.7-1.0 lbs. of nitrogen per acre to produce one bushel of grain. Tissue tests and canopy sensing technology are relatively new ways to assess plant health and nitrogen needs during the growing season. These technologies allow producers to adjust nitrogen rates more precisely and get the most benefit from their input. Phosphorus and potassium rates can be determined by analyzing soil samples and nutrient removal from grain and biomass.Unlike nitrogen, phosphorus and potassium persist in the soil and levels can be built up over several years. If the P and K reserve levels are adequate, the nutrient coming into the field should not exceed the nutrients leaving the field as yield.

Illinois Agronomy Handbook
Image Credit: University of Illinois Extension


Right Time

Nutrients should be applied when plants will utilize them the most. Timing of application plays a bigger role for nitrogen than phosphorus or potassium due to denitrification. All or a majority of the nitrogen for the growing season can be applied before planting. This ensures that all the nitrogen that the corn plant needs is in the field. However, there is a higher risk of losing nitrogen to denitrification during wet conditions when all the nitrogen is applied at one time. Nitrogen application can be split throughout the growing season to decrease nutrient loss. With a split application, a majority of the nitrogen is applied preplant and the rest is applied when the corn plant reaches V8 and is taking in nutrients at a higher rate. The first application acts as a buffer to protect the producer from adverse weather events that can delay the second application. The benefit of a split application is the ability to adjust nutrient rates based on real time field and plant conditions.

Right Place

Fertilizer must be placed near the root system in order for crops to fully utilize the nutrient inputs. Broadcast application followed by tillage will put the nutrients deeper in the soil profile near the root zone. Starter fertilizer is placed directly in the seed bed and provides nourishment for the young plant as soon as it germinates. Sidedress applications place nutrients in the root zone or next to the base of the plant, which allows the plant to access readily available nutrients when it needs them the most. Placing fertilizer below the soil surface dramatically decreases nutrient loss from erosion, runoff, and volatilization. For a no-till system, fertilizer injection is the best option due to crop residue preventing soil contact for surface applied fertilizers.

 Learn more about the 4R Nutrient Stewardship Here


About the Author:

My name is Tanner Carlson and I am from Roseville, Illinois. I am a graduate of Monmouth-Roseville High School and I am currently a senior at WIU majoring in Agriculture Science and minoring in Agronomy. In addition to my education at WIU, I have an A.A.S. in Agribusiness Management from Black Hawk College.


One thought on “Get the Most Out of Your Fertilizer

  1. mjhouston

    I enjoyed reading your blog, considering my background of a family farm. I have hear of the 4 R’s previously, but never understood fully in depth about each one. It is nice to know how many options you actually have when in comes down to the wire on choosing how to apply your fertilizer and what form.


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