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Treat the patient, not the lab test

We all know friends or have heard the stories of people who are not well, and visit a doctor, only to be told “Sorry, there is nothing wrong with you.”

A quote from Arden Andersen I have really appreciated is “treat the patient, and not the lab test.”

We need to do the same for our crops. when a crop is susceptible to disease or insects, and the lab reports seem to be perfect, the lab reports are obviously not reflecting reality well.

In these cases, you treat the crop, and not the lab reports. This is particularly a problem when relying on soil analysis. To such a degree that I can safely say there is no correlation between nutrients reported on most soil reports and actual crop absorption.

Treat the crop, not the lab report.

2020-03-16T14:04:12-05:00February 19th, 2020|Tags: , , |

Don’t guess when you can measure

I attribute much of our rapid learning and our track record of success at Advancing Eco Agriculture to one foundational principle. Don’t guess about anything you can measure.

Growers learn about the successes we have had reducing disease and insect pressure with specific nutrient combinations, and immediately ask the question “How much of these minerals do I need to apply to get these results?”

If we were to answer this question blind, with no data, the only reasonable recommendation is to err on the high side and make sure our recommendations are generous, otherwise, they might not work. Quite likely, the grower ends up applying products beyond what is actually needed for success. For sound recommendations that are the least expensive, and the most effective, you need good data.

A second question that gets asked almost immediately, “How much does a test cost?”

When this question gets asked to determine whether we can ‘afford’ to conduct a test, it must surely rank as one of the most shortsighted agronomy questions.

A much better question is, “How much does it cost to apply a quart of product you don’t need on a block or field?”

The biggest limiting factor in many fields is the excesses of products growers apply. This costs twice, once when you pay for the product the crop didn’t need, and again in reduced yields and quality.

Bottom line, use plant sap analysis on a consistent basis through the entire plant growing period so you know intimately what is happening with nutritional integrity. To do any less is shortsighted, penny wise and pound foolish, as the saying goes.

Don’t guess. Test.

2020-03-16T14:02:29-05:00February 10th, 2020|Tags: |

Why we don’t use Horiba meters to measure nutrients in plant sap

Laboratory leaf sap analysis has given us remarkable insights into plant nutrition. We have learned a great deal about nutrient interactions and plant nutrient absorption of different products and in different environments, and have become champions of sap analysis. 

Occasionally I am asked how we might use the Horiba meters to measure sap contained nutrients in the field, rather than submitting them to a lab.  

I don’t consider Horiba meters to be a viable option if we really want to manage plant nutrition properly. Here are a few reasons why: 

  1. We need to know the levels of many more than four or five nutrients. Knowing the levels of only nitrate, potassium, calcium, sodium, pH, EC, and Brix doesn’t begin to approach the thoroughness of data needed to make informed decisions about nutrient management. For example, manganese influences potassium absorption, and boron influences calcium absorption, to a significant degree. Trying to manage the macronutrients without knowing the levels of the trace minerals promises to be an exercise in frustration and mismanagement.
  2. Nitrate is only one of many possible forms of nitrogen contained within a plant. In a healthy plant with proper protein synthesis, upwards of 80% of the nitrogen will be in the form of enzymes – complete proteins, which don’t register at all on a nitrate meter. It is possible to have a crop with abundant levels of total nitrogen and record a non-detect nitrate on a Horiba nitrate meter. With lab-based sap analysis, nitrate, ammonium, and total nitrogen are all measured separately. Our goal is to have abundant total N, with nondetectable levels of ammonium and nitrate. A goal that we achieve quite regularly.
  3. In many cases, (not always) in-field analysis with the Horiba meters is conducted on the sap contained within the petiole, rather than in the leaf. Yet, we know the petiole is a nutrient and water transport pipeline, and nutrient levels in the petiole sap can fluctuate by as much as 30-40% at different periods during each 24-hour photocycle. With what other analytical methods would we accept a possible 30+% error margin? None, of course. We can reduce this margin of error by collecting samples at the same period of each day, but this doesn’t resolve the challenge that the nutrients contained within the petiole don’t always reflect what is present in the leaf.

In –  lab analysis of leaf sap overcomes all of these challenges. This is why we only use the sap analysis from Crop Health Labs.

 

2020-03-16T13:52:03-05:00January 10th, 2020|Tags: , |

Manage-able data for soil nutrients

Data collection is only useful if you can use it to make management decisions. ‘Manage-able’ data in other words.

Soil analysis is still somewhat of an imprecise science. If you disagree, split a soil sample, send it to different labs and observe the results. This doesn’t mean we shouldn’t conduct soil analysis. It does mean we should understand what we are getting, and know the difference between the various extraction methods. 

I credit much of our success in our agronomy work at Advancing Eco Agriculture to the fact that we avoid guessing about anything we have the capacity to measure. We look at soil nutritional profiles, irrigation water quality where that is relevant, and actual plant absorbed nutrients through sap analysis. 

Our approach to soil analysis has continued to evolve. A decade ago, we would run an ammonium acetate extraction in early fall, August – September time frame, and saturated paste extraction every two weeks during the crop production season. You get an education really quickly about fertilizer performance when you measure what is happening in the soil with plant available nutrients every two weeks. 

After the development of reliable plant sap analysis in the lab, we replaced the biweekly saturated paste samples with biweekly sap analysis. After all, the plant is the final report card, and it can tell us precisely what it is finding abundant or missing, regardless of the soil levels. 

Sap analysis informed us rapidly that there is very little correlation between the presence of nutrients in the soil and actual absorption by the crop. In fact, in the case of some nutrients such as iron and manganese, there is zero correlation. (for reasons of soil redox, dysfunctional biology, and more.)

As a result of constantly learning and improving our understanding of what is happening with the soil’s nutritional profile, I would suggest that growers should collect at least three different types of soil samples to understand what is happening with soil nutrients.

  1. A ‘geochemical assay’ type soil analysis that measures the total mineral content within the profile. This will be the assay that shows in black and white the tens of thousands of pounds of phosphorus and potassium, and the hundreds of pounds of manganese and other trace minerals contained within many soils. Minerals that biology can tap into over time. Several samples should be pulled at different depths. One sample should be as deep as the A horizon, the topsoil layer, or as deep as the upper mass of roots generally reach. Usually somewhere in the neighborhood of 6-12 inches. A second sample should be collected immediately below the first, down to a depth of 24-36 inches, the B horizon. These samples only need to be collected once, to give us evidence of what reserves we have to work with, or not. If there is no molybdenum, selenium, cobalt, vanadium, or some of the other ultra trace elements showing up, crops will benefit from adding some. This type of sample can be run through AGAT Labs, and possibly others.
  2. A more familiar ‘CEC’ analysis with ammonium acetate or Mehlich III extraction. Mehlich III or Olsen extraction are preferred for phosphorus, Bray extraction can be unreliable in some soil types. We typically use a Mehlich III extraction for all the nutrients across the board. With this analysis it is also valuable, I would suggest necessary, to measure cobalt, selenium, molybdenum, and nickel as a standard, at least on some fields. We typically conduct this analysis in late summer/early fall, every year on high value crops, and every few years on broad acre commodity crops. 
  3. An organic acid, ‘H3A’ or Haney analysis to identify the nutrients the soil is capable of releasing in the coming growing season. We have just begun including this test as a standard, and are still learning it’s ins and outs. We are experimenting with both spring and fall samples, but it makes sense to me to collect these samples in the spring to most accurately identify what is happening closest to the crop season. 

When you collect all three of these samples, you can form an accurate perception of what is really going on with your soils mineral profile, and the resources you have available to work with. Now you can make informed decisions about nutrients actually need to be applied, and what you can tap into from the soil reserves. 

Saturated paste tests are still a very useful tool for special situations. Very sandy soil, a fast-growing crop such as spinach, muck soils, and in artificial media are all places where saturated paste tests give us valuable information. They are not the right decision-making tool to determine soil amendments though. Their biggest strength is also their biggest weakness. Their strength is they show you what is available the next few weeks. Their weakness is that they only show you what is available the next few weeks. 

I am still looking for a microbial assay that gives us ‘manage-able’ data. This is a bit of a challenge, because we need an assay that both identifies the presence of a species or group, AND the degree of presence. It is not enough to know that we have both pseudomonas and fusarium species. We need to know that we have enough of the right pseudomonads to suppress possibly infectious fusarium.

PFLA tests are ‘interesting’ but we haven’t figured out yet how to make the data manage-able. Non-actionable means we don’t run them very often. 

A topic for another post is the importance and usefulness of qualitative in field soil analysis such as water infiltration and agreggate stability tests.

 

2020-03-16T13:44:36-05:00December 27th, 2019|Tags: , , |
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