When it comes to soil fertility, there are many pieces of the puzzle that interact and interfere with our ability to understand what is exactly going on within our soil. Plant tissue sampling, which has been widely implemented by retailers across the Midwest region, is just one way to gather insights from soil fertility efforts on fields.
Many different variables come into play when evaluating the effectiveness of plant tissue analysis – for example: timing of tissue samples, species and variety of plant, and area of the plant where the sample was taken. Among other things, there is always variability depending on the factors above, which is why it is highly recommended to view and evaluate plant tissue samples as just part of the story that will lead to increased soil fertility insights.
“Over the decades, accumulated experience has been extremely important for using plant analysis,” comments Steve Commerford, crop consultant at Commerford Agronomics and AFREC Council Member. “I utilize plant analysis in a variety of ways. One of the most effective ways in troubleshooting nutrient deficiencies. I take samples of the plants from adjacent, good and poor areas, and compare the nutrient levels between those spots in the field.”
When recommending plant tissue sampling to his clients, Commerford recognizes the importance of interpreting data correctly and understands the variability in the process depending on the factors listed above. His success with this process is largely due to looking at ratios within plants, rather than the measurements at face-value when comparing them to research-derived recommendations from retail companies or universities.
AFREC funded research, conducted by Dr. Jeff Coulter, Professor and Extension Agronomist at the University of Minnesota, dove deep into each piece of the puzzle of soil fertility, including soil pH, cation exchange, organic matter, electrical conductivity of soils by depth, fertilizer application timing and amounts, as well as soil sample tests.
The research evaluated nutrient uptake variances between two types of management systems – sustainable intensification and farmer practice. In this study, sustainable intensification was defined as a high-yield system that is also environmentally responsible. It includes a longer-season corn hybrid and a greater planting rate. Additionally, standard and advanced nutrient management were also evaluated in this study. Advanced nutrient management was outlined as phosphorus and potassium application based on grain removal and in-season N applications that align closely with N uptake in corn1.
Comparison Photos from Study
The photos above show the sustainable intensification and advanced nutrient management, but the photo on the left shows crop that had no N applied, and the photo on the right shows crop in which N applied.
To evaluate the nutrient uptake in these two management and nutrient programs, corn plant leaf tissue samples were taken during the V10 stage and evaluated for the presence of 12 main nutrients.
The key findings of this report showed among the two management practices, farmer practice verses sustainable intensification, and standard verses advanced nutrient management, corn nutrient uptake did not differ greatly between farmer-practice and sustainable intensification, but did find response in advanced verses standard nutrient management. The advanced nutrient management found the following results:
Other nutrients in this study did not show significant results. When looking at the results above, the phosphorous and sulfur uptake, in regard to corn management, are two metrics that are important and should be monitored by a grower. Iron and aluminum on the other hand, are two nutrients that are not as important to corn management and therefore further exemplify that plant tissue sampling results will give extensive information; but information must be combed through with an experienced comb to draw overarching insights that are valuable for an operation.
Additionally, over the 5-year study, the sustainable intensification and advanced nutrient management showed the following yield results:
|Agronomic Management||Fertilizer Management||5-Year Avg. Yield Difference (bu/acre)|
|FP1||Standard||Control – 0|
1 FP = Farmer Practice, SI = Sustainable Intensification
Plant tissue analysis should be used as a metric to derive these insights, but it is only one piece of the soil fertility puzzle that should be recognized and utilized, but not a tell-all practice to solve all soil fertility questions.
Dan Kaiser, University of Minnesota Extension Soil Fertility Specialist, comments on the effectiveness of plant tissue sampling as it relates to soil fertility insights:
“Tissue analysis is just one tool available to help diagnose issues. In most cases, tissue analysis was never meant to be used to direct fertilizer applications in annual cropping systems. Accurate assessment for tissue results requires some sort of positive control to be in place – you need something to compare to.”
When it comes to soil fertility, no one knows your fields better than you do. This being said, becoming a student of your soil and starting to tackle and investigate each piece of the puzzle will lead to soil fertility insights that are customized to you and your land.
Commerford recommends, “Plant analysis is a good tool to ‘look back on’ how a fertilizer program is doing and correct problems in future years. Generally, plant analysis can’t help correct problems the same growing season, because it is not possible to get most nutrients effectively into the plant in the same year.”
Soil fertility is more complex than a quick fix application of a fertilizer in a field. We encourage farmers to do their own research on their farms and not just take recommendations at face value. AFREC will continue to fund research that will bring light on issues like these and provide an opportunity for farmers to start to piece together their puzzle of soil fertility.
 Coulter, J., Dr., Vetsch, J., Murrell, S., Dr., Fixen, P., Dr. (2017). Advancing Intensive Management of Continuous Corn on Irrigated Stands (Rep.). http://mnsoilfertility.com/wp-content/uploads/2014/03/R2015-04-Final-Report.pdf
©2019 Agricultural Fertilizer Research and Education Council of Minnesota