MLSN Guidelines: what they are, and how to use them

The presentation explains the MLSN guidelines and answers questions about their development and use. The MLSN guidelines work like this.

1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below the MLSN guideline.

2. Estimate future use of those elements, and make sure that amount can be supplied by the soil, while still keeping the soil above the MLSN guideline.

3. If the soil doesn't have enough to do that, then apply enough of that element as fertilizer to keep the soil above the MLSN guideline.

Transcript

1. MLSN Guidelines What they are, and how to use them Micah Woods Chief Scientist Asian Turfgrass Center www.asianturfgrass.com 6 May 2015 a TurfNet webinar
2. MLSN in 10 minutes MLSN is an acronym for Minimum Levels for Sustainable Nutrition. This is a method for the interpretation of soil nutrient analyses.
3. MLSN answers the 2 questions of soil testing 1. Is this element required as fertilizer? 2. If it is required, how much?
4. More specifically… One can express the quantity of an element required as fertilizer as Q. a + b − c = Q where, a is the quantity of the element used by the grass b is the quantity of the element required in the soil c is the quantity of the element present in the soil Q is the quantity of the element required as fertilizer
5. MLSN is a value for b amount needed a + b − amount present c = fertilizer requirement Q a is a site-specific use estimate, b is the MLSN guideline, and c is the soil test result.
6. a, www.paceturf.org/journal/climate
7. b
8. Using MLSN 1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below the MLSN guideline.
9. Using MLSN 1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below the MLSN guideline. 2. Estimate future use of those elements (a), and make sure that amount can be supplied by the soil, while still keeping the soil above the MLSN guideline (b).
10. Using MLSN 1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below the MLSN guideline. 2. Estimate future use of those elements (a), and make sure that amount can be supplied by the soil, while still keeping the soil above the MLSN guideline (b). 3. If the soil (c) doesn’t have enough to do that, then apply enough of that element as fertilizer (Q) to keep the soil above the MLSN guideline.
11. As an example for K a + b − c = Q
12. As an example for K a + b − c = Q In ppm, a = 100, b = 37, c = 70.
13. As an example for K a + b − c = Q In ppm, a = 100, b = 37, c = 70. amount needed 100 + 37 − amount present 70 = fertilizer requirement 67
14. As an example for K a + b − c = Q In ppm, a = 100, b = 37, c = 70. amount needed 100 + 37 − amount present 70 = fertilizer requirement 67 Convert between 3-dimensional (ppm) and 2-dimensional (ex. g m-2, or lb 1000 -2) based on rootzone depth and soil bulk density. For a 10 cm deep rootzone with bulk density of 1.5 g cm-3, 1 g m-2 equals 6.7 ppm, and 1 lb 1000 -2 equals 33.5 ppm. Using that conversion, Q of 67 ppm is a K requirement of 10 g m-2 or 2 lb 1000 -2.
15. estions?
16. Is there continued field sampling or any plans to be er regionalize the sampling for possibly di erent MLSN numbers for di erent regions or possibly between di erent soil types (ex. USGA vs. Native Soil)? MLSN is dynamic in that we systematically add data and review the guidelines. The Global Soil Survey is an ongoing project to gather more data. No immediate plans for regionalization, basically because of lack of data, and scope of project. Note, however, that while b is constant, a is infinitely site-specific and c is both soil and site-specific.
17. What soil testing method(s) should we utilize to determine the nutrient levels in the bank prior to making fertilizer applications to correct deficiencies (if any)? We used the Mehlich 3 extraction for the development of the MLSN guidelines.
18. What about the correlation with other testing methods. I have years of soil test data, but unfortunately these used a di erent extraction method (I believe ammonium acetate). Is there a reliable and accurate way to convert the values from other extraction methods to Melich 3? There are some conversion equations that can be used. Any conversion will introduce some error, but with a bit of e ort one can make useful estimates.
19. Soil paste extracts? yes or no? No. Soil paste extracts, or saturated paste extracts – these are for assessing soil salinity. Not a good test for determining how much fertilizer should be applied.
20. Why not regionalization? WOW‼ I simply CANNOT wrap my head around the thought of not considering soil types and or regionalization for nutrient recommendations‼ So are you saying that sand has the same nutrient holding ability as a rich sandy loam I agree that it seems counterintuitive to make nutrient recommendations with guidelines (b) that admi edly do not consider soil type or region. But by thinking about the a and c of the equation used to get Q, there is infinite regionalization. These are adjusted for: grass species desired growth rate site soil conditions time of year site climate
21. I’ll ask myself a question. Can you explain how the guidelines were developed? Sure. I’ll use potassium (K) as an example.
22. Guideline development process: the raw data 0 100 200 300 400 500 0 1000 2000 3000 3721 soil samples from good turf K (ppm)
23. Data organized into a histogram K (ppm) Frequency 0 100 200 300 400 500 0 100 300
24. Remember, all the samples are from good turf, like this
25. I am curious about the definition of good turf. What are the characteristics of good turf? For the MLSN samples, which all come from professionally-managed turf areas, the good turf is from areas that the professional turf manager identifies as performing well at the time the sample was collected. It is the inverse of bad turf or problem areas identified by a professional turf manager.
26. With an overlay of probability density K (ppm) Frequency 0 100 200 300 400 500 0 100 300 density
27. A gaussian (normal) model doesn’t fit well K (ppm) Frequency 0 100 200 300 400 500 0 100 300 density normal
28. A log-logistic distribution fits the data much be er K (ppm) Frequency 0 100 200 300 400 500 0 100 300 density normal log-logistic
29. Probability of the sample being below x 0 100 200 300 400 500 0.0 0.4 0.8 K (ppm) Cumulative probability data
30. Model is very close to the data 0 100 200 300 400 500 0.0 0.4 0.8 K (ppm) Cumulative probability data model
31. Identify a MLSN for K at cumulative probability of 0.1 0 100 200 300 400 500 0.0 0.4 0.8 K (ppm) Cumulative probability model
32. Fertilizer is recommended to keep the soil above MLSN K (ppm) Frequency 0 100 200 300 400 500 0 100 300
33. Would you elaborate on the potassium trial conducted by Rutgers where winterkill was more severe on poa plots that had less than 50 ppm of K? In the trial at Rutgers, there is a K deficiency in plots not supplied with K. Where K has been supplied, the winter damage was not evident, and anthracnose is reduced. If the MLSN approach were implemented on those trials, enough K would be supplied to eliminate the deficiency.
34. How do you convert a soil report results from lbs/ acre to ppm to see if one’s numbers are above or below the MLSN requirements? You divide lbs/acre by 2 to get ppm, assuming the samples are from a 6” (15 cm) depth. You should be ge ing results in ppm which is what the lab machines measure. Any lb/acre or lb/1000 or kg/ha reporting is a calculated number from the ppm result.
35. Can I also assume that you also do not consider that some irrigation water can act as a stripper? That’s correct. If there are no salts in the water, then there won’t be anything in the water to exchange with ions in the soil, and it won’t act as a stripper. And one would not be leaching the soil if the water doesn’t have salt in it. If the water does have salt in it, then the ions in the water will exchange with the ions on exchange sites in the soil, to some extent, with the tendency being more adsorption of divalent cations (Ca2+, Mg2+) in the soil and more monovalent cations (K+, Na+) in solution.
36. What are your thoughts on nutrients being tied up in the soil This is an unnecessary complication. One measures nutrient availability by doing a soil test and interpreting the soil test to determine if a nutrient is required as fertilizer.
37. Was the work done to develop the MLSN done at 4 or 6 inches? Also, what if you have specified to your lab that the samples were taken at a 4” depth? The samples for the development of MLSN were from 4 inches (10 cm). The lab should report ppm units back to you, which are independent of soil depth; if the lab reports lb/acre or kg/ha, they will have calculated that based on the sample depth you provided them.
38. Once you are above those levels, you just need to maintain it to that point? The numbers that I have are well above those levels, therefore I would not need to apply Ca, P, Mg or K. Just a straight N product, since the other nutrients are not lacking in the soil makeup? How does one do that in a natural or organic program in which many products contain small amounts of P and K with the N application? That’s correct. And I would do that as best as I could, trying to use products with low amounts of P and K. Really I would try to avoid P completely if the soil had enough.
39. I would like to see info included about soil health testing ...My thoughts are that we as turfgrass managers leave behind the biological leg of the stool and rely on the physical, and chemical legs exclusively and that the real MSLN could be improved upon and may be lowered based on soil health. Good point. There are some intriguing new tests for assessing soil biology or “soil health.” But these tests su er from the same problem as conventional soil chemical guidelines – how can one interpret the results for turfgrass? With tests of soil health, I’m optimistic about being able to make recommendations in the future, but at present it would just be guessing.
40. More information available at: www.turfnet.com/topic/7024-mlsn-questions-for-upcoming- webinar/ www.blog.asianturfgrass.com/fertilizer/ www.paceturf.org www.gcsaa.org/gcm-magazine/2014/january/gcm-january- 2014-just-what-the-grass-requires www.facebook.com/mlsnturf