With plant sap analysis we use a technique we call differential testing. By measuring the old and new leaves separately, we can observe how the plant is self-regulating nutrient movement
Plant Sap Analysis as a Driver of Regenerative a Agronomy
John Kempf | Advancing Eco Agriculture
A core tenet of regenerating the health of any organism is “first, do no harm.” This foundational principle permeates through the more nuanced practices of soil health management, including minimizing tillage, shielding soil from exposure, and curbing the use of synthetic fertilizers and pesticides detrimental to soil microbial life.
Despite its sound ecological principles, the notion of reducing fertilizer and pesticide applications can evoke discomfort among farmers. What is the possible risk of yield loss and reduced profitability when fertilizers are removed? Conventional wisdom often suggests an inevitable dip in yields during the initial 3-5 years of transitioning to regenerative agriculture, with the promise of eventual recovery as soil health improves.
However, the expectation of a negative J-curve yield trajectory during transition reflects an idealistic rather than a practical approach to agronomy. A yield reduction at any phase is a reflection of poor agronomic management. It is reasonable to expect immediate yield and quality improvements while concurrently reducing synthetic inputs. Achieving this outcome requires wise agronomic decision-making based on data, not intuition.
Sap Collection Protocols
We first began testing plant sap analysis at AEA after we observed discrepancies between traditional plant tissue analysis and actual field observations. There was no consistent correlation with disease and insect resistance, which the scientific literature indicated should be present. There was also no consistent correlation with yield and quality.
Our standard sap collection protocol on many crops is to collect samples every 14 days on representative fields throughout the growing season. Collecting samples continuously through the season is an incredibly revealing exercise, as we get to observe nutrient movement within the plant and understand seasonal patterns of nutrient availability from the soil, and nutritional requirements from the crop.
With plant sap analysis we use a technique we call differential testing. By measuring the old and new leaves separately, we can observe how the plant is self-regulating nutrient movement, and whether it is using the oldest leaves on the plant as a nutrient source (inadequate soil supply) or as a nutrient sink (abundant soil supply).
The Benefits of Sap Analysis
Sap analysis differs from tissue analysis in that fresh plant leaves have the sap extracted in the lab for nutrient assessment, in contrast with tissue analysis, which measures the total nutrient content contained within the leaf structure. This process allows for earlier detection of nutrient deficiencies –up to 21 to 28 days ahead of tissue analysis and 35 to 42 days before visible symptoms manifest, depending on the speed of crop growth and the severity of the deficiency.
We have also been able to correlate the presence of specific pests or diseases with specific nutritional profiles, allowing us to accurately predict disease and insect susceptibility weeks into the future. As you can imagine, this is an incredibly empowering tool since it also means we now understand how to adjust plant nutritional profiles with in-season nutritional applications to reverse susceptibility. We can prevent and reverse disease and insect pressure with nutrition management effectively and with precision.
A valuable aspect of consistent sap analysis is the ability to understand precisely what nutrients the soil, in its current state of health, can deliver to the crop. We no longer need to guess how much fertilizer needs to be applied or how much we can safely reduce. The crop can tell us with a high degree of accuracy and advanced notice to make necessary course corrections without harming yield and crop performance.
Sap analysis serves not only as a real-time nutritional adjustment tool but also informs future nutritional strategies. As we observe nutrient movement through the course of a season, it is common to observe sudden changes at specific stages of crop development. Perhaps potassium levels drop off sharply during the grain fill stage, and we discover that our potassium applications are not timed correctly and need to be applied later. Or maybe calcium amendment applications are being applied too late and need to be applied earlier, so the product release curve matches the crop demand curve.
The approach we recommend is to apply minimal quantities of fertilizer at planting, in conjunction with robust microbial inoculants and stimulants, and then be prepared to make later applications in season based on measured crop need. We often recommend beginning the season with as little as 10-20 units of nitrogen, for example, and then observing what the data tells. It is common to see this initial nitrogen application, combined with microbial-delivered nitrogen, maintain a crop’s nitrogen at abundant levels until the grain fill stage, which is a surprise to many growers.
Insights from Sap Analysis
Since integrating plant sap analysis in 2011, we've gleaned invaluable insights into nutrient interactions and plant nutrition within biological systems. Plants are the ultimate report card, eliminating guesswork regarding soil capabilities and instilling confidence in nutrient management decisions.
We have learned that most fruit and vegetable quality problems result directly from excessive nitrogen and potassium levels applied at the wrong time. We have learned that many growers are applying the right things but at the wrong times to produce the best crop responses. We have learned that excessive levels of nitrogen and potassium that are applied at the wrong time create a substantial yield drag, which is the exact opposite of what most of us would expect.
Most importantly, we have learned that we can reduce inputs significantly with very low risk while increasing yields. This gives us a viable pathway to regenerative agriculture, wherein reducing external inputs translates into immediate economic benefits instead of yield setbacks. By harnessing the power of plant sap analysis, we unlock regenerative agriculture's full potential, harmonizing ecological stewardship with economic prosperity.
John Kempf is an entrepreneur, speaker, podcast host, leading crop health consultant and designer of innovative soil and plant management systems. He founded Advancing Eco Agriculture and serves as the Chief Vision Officer and Executive Board Chair. https://advancingecoag.com/plant-sap-analysis/
The content & opinions in this article are the author’s and do not necessarily represent the views of AgriTechTomorrow
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