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An illustration of John Kempf

Guest article: Unlocking regenerative agriculture’s potential with plant sap analysis

June 20, 2024

Editor’s note: 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.

The views expressed in this article are the author’s own and do not necessarily represent those of AgFunderNews.

A core principle of regenerative agriculture is “first, do no harm” by minimizing practices detrimental to soil life such as tillage, exposure, and synthetic inputs. However, reducing fertilizers and pesticides can raise concerns about yield loss and profitability among farmers. The expectation of an initial yield dip during the three- to five-year transition period reflects an idealistic rather than practical agronomic approach. Immediate yield and quality improvements while reducing synthetic inputs are achievable through data-driven decision-making.

Sap collection protocols

At Advancing Eco Agriculture (AEA), we began plant sap analysis after observing discrepancies between traditional tissue analysis and field observations regarding disease, insect resistance, yield, and quality. Our standard protocol involves collecting sap samples every 14 days from representative fields throughout the growing season to observe nutrient movement patterns and crop requirements.

We use a “differential testing” technique, measuring old and new leaves separately to understand how the plant self-regulates nutrient movement and whether it is using the oldest leaves as a nutrient source (inadequate soil supply) or sink (abundant supply). This allows us to detect potential deficiencies before they manifest visibly.

Image credit: iStock

Benefits of sap analysis

Sap analysis differs from tissue analysis by extracting and assessing fresh leaf sap nutrients, allowing earlier detection of deficiencies up to 21-28 days ahead of tissue analysis and 35-42 days before visible symptoms, depending on growth rate and severity. This early warning system enables timely corrective action. We can correlate specific pests or diseases with nutritional profiles, predicting susceptibility weeks in advance and adjusting nutritional applications to prevent and reverse pressure effectively and precisely.

For example, sap analysis helped a cherry grower increase fruit size and profitability by $1,600 per acre by simply stopping potassium applications at the wrong time. Consistent sap analysis reveals what nutrients the current soil health can deliver to the crop, eliminating guesswork on fertilizer needs and safely reducing amounts without harming yield and performance. This data-driven approach avoids the over-application of inputs.

Sap analysis is a real-time adjustment tool and informs future nutritional strategies by observing nutrient movement changes at specific crop development stages to optimize timing. For instance, it may show that potassium and phosphorus levels tank during early grain fill, indicating these nutrients should be applied later rather than at planting.

Improving crop quality and yields

In addition to reducing input costs, sap analysis can boost crop quality and yields. A nectarine grower saw sap analysis reveal that while soil tests showed high calcium and low iron levels, the sap analysis indicated the opposite: low calcium and excessive iron inside the plant. This biological insight allowed corrective nutrient applications to improve crop performance.

Another example is with tomato crops, where traditional tissue tests suggested manganese deficiency, prompting foliar manganese sulfate applications. However, sap analysis revealed the manganese was not being absorbed by the plants. Switching to a chelated, reduced form of manganese based on the sap data immediately improved manganese uptake and plant response.

These examples demonstrate how sap analysis provides a more accurate picture of the plant’s internal nutrient status and needs than conventional soil and tissue tests alone. By aligning nutrient management with the plant’s ability to access and utilize nutrients, yields and quality can be optimized while reducing excess inputs.

Image credit: iStock

Reducing environmental impact

This precision nutrient management increases yields while reducing environmental impact. A grower in Shropshire, UK was able to cut disease control costs by using sap analysis to fine-tune crop nutrition and improve plant health.

By growing healthier plants in healthier soil, fungicide inputs are reduced. Sap analysis allows monitoring nutrient levels like nitrogen forms (ammonium, nitrate, total N), electroconductivity, sugars, and pH – good indicators of overall plant health. Ensuring adequate nutrition while avoiding excess can minimize disease and pest attraction.

Insights and approach

Since integrating sap analysis in 2011, we’ve gained invaluable insights:

  • Most fruit/vegetable quality issues result from excessive nitrogen and incorrect potassium timing.
  • Growers often apply the right inputs but at suboptimal times for the best responses.
  • Excessive nitrogen/potassium levels applied incorrectly create substantial yield drag, contrary to expectations.
  • Inputs can be significantly reduced with low risk while increasing yields.

Our recommended approach is to apply minimal fertilizer at planting with robust microbial inoculants, then make later applications based on measured crop needs. For example, only 10-20 units of nitrogen combined with microbial-delivered nitrogen can maintain abundant levels until the grain fill stage. This precision nutrient management increases yields while reducing environmental impact.

By growing healthier plants in healthier soil fungicide inputs can be reduced. By harnessing sap analysis, regenerative agriculture can unlock its full potential, harmonizing ecological stewardship with economic prosperity through data-driven nutrient management that reduces inputs without sacrificing yields.

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