Soil Nutrients Missing? 5 Steps for Getting Back on Track

    Corn crop landscape. Photo: Bill Griffith

    Nutrients are disappearing from our soils. While the past several years have seen impressive crop yields — the downside of the story is an increase in nutrient removal.

    The International Plant Nutrition Institute (IPNI) reports that the percentage of soils below the critical nutrient level, a key measurement in evaluating soil productivity, increased from 47% in 2005 to 55% in 2010.

    With nutrient balance levels declining nationwide, it’s imperative for farmers to be vigilant and identify deficiencies in their crops. An an example, Iowa, a state with an intensive production history in soybeans and corn, has a huge example of nutrient loss, where potassium balance has decreased a staggering 434% since 1975. Potassium removal trends increased 35% and fertilizer sales decreased 7% in the state during that period.

    Identifying nutrient issues and putting an operative plan in place to address them is a big task for farmers. Robert Mullen, Director of Agronomy for PotashCorp,  has developed a  5-step process to help get deficient crops back on track. He advises that if your fields have a proven history of micronutrient issues, skip to step 5 and get the applications started.

    Step 1: Visual Assessment

    The first part in this process involves getting in the field to identify the exact problem areas. When in the field, nutrient deficient crops can often be identified by discoloration of the crop. Generally, chlorosis, or yellowing within the leaf, is a key symptom of nutrient deficiencies and can signal crops with poor health. For example, a manganese deficiency in soybean plants will be visible in the upper part of the canopy in the new growth of the plant, but the leaf veins will retain their green color. Sulfur will also cause chlorosis, or a pale green color, in the new growth.

    Step 2: Soil Testing

    It’s important to note that testing soil for for nutrient deficiencies, also known as field diagnostics, is different than collecting soil information to maintain a fertility program. When testing soils to maintain a fertility program, farmers should focus on collecting enough samples to represent their entire farm. A good rule of thumb is to collect 15 to 20 soil cores from across a given area to represent a composite sample. During the diagnostic soil testing process, farmers should collect about 10 to 15 samples from both the unaffected and affected soil areas to get a full representation of their fields.

    Step 3: Conduct a Plant Tissue Analysis

    The plant tissue analysis process is similar to diagnostic soil testing, as farmers should collect samples from both the unaffected and affected areas. Two key times to collect samples are early in the season and midseason. When collecting early in the season, Dr. Mullen advises farmers to collect the entire plant. When collecting midseason, farmers should collect the uppermost leaves in broadleaves and collect leaves right next to where the ears develop in corn, to get an accurate representation of the plant’s health.

    Step 4: Analyze Historical Information

    During this step farmers should consider that there is a chance some of their crops won’t show any symptoms, but the fields will produce yields that are lower than predicted. This is an indication of hidden hunger, which can be fixed by paying close attention to the soil test results.

    Step 5: Prescribe Corrective Course of Action

    After conducting steps one through four, you may arrive at a simple corrective course of action that will take care of the issues you’re experiencing. However, if farmers still aren’t sure where the problem lies, Dr. Mullen suggests taking an educated guess and applying strips within the fields to see what takes care of the problem.

    Some issues can be taken within the current growing season, such as micronutrient deficiencies that can be treated with a foliar application fertilizer. However, if dealing with macronutrient issues you will need to wait and make applications after harvest to satisfy the crops’ demand.

    It’s important to note that after conducting this process there is a chance not every problem will be solved, but these five-steps will help get your yields back on the right track.

    Click here to view this video more info on the 5-step program.

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