Just what the grass requires

This presentation is about using the MLSN guidelines for soil test interpretation. The approach described in this presentation ensures the grass will be supplied with "just what it requires", while ensuring a buffer of untouched nutrients remains in the soil. I used these slides for my presentation in Tavira at the Portugal Greenkeepers Association congress.

Transcript

1. Just what the grass requires: using and understanding the MLSN guidelines for nutrient recommendations Micah Woods November 9, 2017 Chief Scientist Asian Turfgrass Center www.asianturfgrass.com
2. Two questions 1. Is this element required as fertilizer? 2. If it is required, how much should I apply?
3. Two questions 1. Is this element required as fertilizer? 2. If it is required, how much should I apply? To answer those questions, we need to know how much is used by the grass and how much can be supplied by the soil.
4. T o a n s w e r t h o s e f u n d a me n t a l q u e s t i o n s , w e n e e d t o e s t i ma t e 3 q u a n t i t i e s c r e e p i n g b e n t g r a s s S h a n g h a i , C h i n a
5. T o a n s w e r t h o s e f u n d a me n t a l q u e s t i o n s , w e n e e d t o e s t i ma t e 3 q u a n t i t i e s c r e e p i n g b e n t g r a s s S h a n g h a i , C h i n a
6. T o a n s w e r t h o s e f u n d a me n t a l q u e s t i o n s , w e n e e d t o e s t i ma t e 3 q u a n t i t i e s c r e e p i n g b e n t g r a s s S h a n g h a i , C h i n a
7. T o a n s w e r t h o s e f u n d a me n t a l q u e s t i o n s , w e n e e d t o e s t i ma t e 3 q u a n t i t i e s c r e e p i n g b e n t g r a s s S h a n g h a i , C h i n a
8. T o a n s w e r t h o s e f u n d a me n t a l q u e s t i o n s , w e n e e d t o e s t i ma t e 3 q u a n t i t i e s c r e e p i n g b e n t g r a s s S h a n g h a i , C h i n a
9. a, b, and c • a is a site-specific estimate of plant use. • b is the amount we want to ensure remains in the soil after the plant use is accounted for. This is a minimum we don’t want to drop below. You can think of it as a reserve amount in the soil. This is the MLSN guideline level. • c is the amount actually present in the soil. This is the soil test result.
10. a, site-specific estimate of plant use
11. What affects growth? Growth is a function of photosynthetic light, plant water status, temperature, and a nutrient index.1 This can be represented as the environmental productivity index (EPI). 1Each of these factors can be represented by an index that takes a value from 0 to 1. Thus, the EPI will also have a value in the range of 0 to 1. The nutrient index is primarily a function of leaf N content.
12. What affects growth? Growth is a function of photosynthetic light, plant water status, temperature, and a nutrient index.1 This can be represented as the environmental productivity index (EPI). (light)(water)(temperature)(nutrient) = EPI 1Each of these factors can be represented by an index that takes a value from 0 to 1. Thus, the EPI will also have a value in the range of 0 to 1. The nutrient index is primarily a function of leaf N content.
13. Light, Samui Island, Thailand
14. Light, Samui Island, Thailand
15. Light, Fukuoka, Japan
16. Quantum light meter
17. Water, Thailand
18. Temperature, Iceland
19. Nutrient – progressive K deficiency
20. Growth = nutrient use
21. Simplified EPI   XXX X (light)  XXX X (water)(temperature)(nutrient) = EPI
22. Law of the minimum? “In terms of Liebig’s Law of the Minimum, nitrogen is usually the element in shortest supply, and therefore applying nitrogenous fertilizers has a large impact on plant growth. The reason that nitrogen, of all the elements, is so often limiting to growth is simply that plants require a great deal of it.” Jonathan Silvertown in Demons in Eden: The Paradox of Plant Diversity.
23. Not like this
24. 3 ways to get a number for growth 1. Estimate from clippings.
25. 3 ways to get a number for growth 1. Estimate from clippings. 2. Estimate from N applied.
26. 3 ways to get a number for growth 1. Estimate from clippings. 2. Estimate from N applied. 3. Estimate from temperature.
27. 10 15 20 25 1 2 3 4 5 6 7 8 9 10 11 12 Month Average temperature Faro
28. 0.00 0.25 0.50 0.75 1.00 1 2 3 4 5 6 7 8 9 10 11 12 Month Cool season GP Faro Monthly Growth Potential
29. 0 1 2 3 1 2 3 4 5 6 7 8 9 10 11 12 Month Estimated N use (g m2) Faro
30. b, amount to ensure remains in the soil
31. 1. The conventional way – low, medium, & high classification
32. 1. The conventional way – low, medium, & high classification 2. Conventional guidelines are broken
33. 1. The conventional way – low, medium, & high classification 2. Conventional guidelines are broken 3. The MLSN guidelines address these problems
34. The conventional way – low, medium, & high classification
35. The conventional way GCSAA GCM Magazine, January 2004
36. List of ranges • low • medium • high
37. “Low range: a high probability (80-100%) that applying the nutrient will elicit a growth response.”
38. “Medium range: approximately a 50% chance of getting a plant growth response …; if supplemental fertilizer is not applied, growth will probably be limited, especially as the season progresses.”
39. “High range: little or no crop response is expected from applying the particular nutrient.”
40. Conventional guidelines are broken
41. What’s the objective of turfgrass management? Royal Bangkok Sports Club, Thailand
42. Adjusting the growth rate The Old Course, St. Andrews
43. “The fundamental principle of successful greenkeeping is the recognition of the fact that the finest golfing grasses flourish on poor soil and that more harm is done by over-, rather than underfertilizing.” – Alister MacKenzie
44. Turfgrass management, or agronomy?
45. “In some cases, turfgrasses have been placed in a ‘high’ P and K requirement category, while pasture grasses were in a ‘low’ category. This decision was based on economics, not agronomics. The cost of fertilization was not considered of primary importance for turf.” – Carrow, Waddington, and Rieke
46. And grass is often grown in sand
47. “Turfgrass researchers continue to improve the soil testing recommendations, but that type of research is time consuming and expensive. It is also worth noting that every time a researcher conducts one of these studies, they tend to find that the levels required are lower than what we previously thought – meaning that ‘low potassium’ you got on your last soil test report might be optimum down the road.” – Doug Soldat
48. The MLSN guidelines address these problems
49. “I recommend you compare your results with PACE Turf’s Minimum Levels for Sustainable Nutrition [MLSN] guidelines ... the minimum levels published by PACE are drastically lower than many traditional soil test interpretations, and likely more accurate.” – Doug Soldat
50. The MLSN guidelines address these problems
51. c, the amount actually in the soil
52. Using MLSN
53. Let’s make sure we have enough beer
54. 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 kept in the soil c is the quantity of the element present in the soil Q is the quantity of the element required as fertilizer
55. For more, please see www.asianturfgrass.com or @asianturfgrass on Twitter.