Golf Course Management

JAN 2014

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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Micah Woods, Ph.D. Larry Stowell, Ph.D. Wendy Gelernter, Ph.D. Just what the grass requires: Using minimum levels for sustainable nutrition Good turf performance can be achieved at lower nutrient levels. In 2012, we introduced the minimum levels for sustainable nutrition (MLSN) as an alternative to conventional soil nutrient guidelines (7). Conventional guidelines are epitomized by the low, medium, high and very high classifcation scheme described in the third part of the "Clarifying Soil Testing" series published in GCM 10 years ago (1). In light of recent trends in reduced inputs and increased sustainability, and taking newly published data into account, the conventional approach requires scrutiny and signifcant revision. Conventional guidelines are not only complex, they are also relatively static, without regular or systematic updates. However, regular updates seem like a good idea, because many research projects suggest that high-quality turf can be produced at levels below the conventional guidelines (2,3,4,6,8). As an alternative to the conventional guidelines, the MLSN guidelines are an attempt to identify not the optimum levels for soil nutrients, but rather the minimum levels of soil nutrients at which we can be confdent of good turf performance. You may have seen the same thing yourself: high-quality turf with no problems, growing in a soil classifed as low in one or more essential elements. The question then arises, if the soil is lacking in these elements, why is the grass performing so well? Adding a nutrient may change the soil test result to move the level up to a desired range, but if the nutrient addition has no effect on the grass performance, is it necessary? 132 GOLF COURSE MANAGEMENT 01.14 How to use the MLSN guidelines at your facility The MLSN guidelines (Table 1) take a new approach to soil test guidelines. Turfgrass managers will have two questions about fertilizer application, and the MLSN guidelines answer both of them. The frst question is, "Does this element need to be applied as fertilizer?" As a follow-up to the frst question, one also needs to ask, "If this element is required, how much should be applied?" To answer the frst question, simply com- pare the MLSN guideline value for an element to the soil test level for that element. If the element is below the MLSN guideline, or if the estimated use of that element will drop the soil to the MLSN guideline during the course of the growing season, then that element should be applied. If the element, as measured by the soil test, is above the MLSN guideline, and if estimated use of that element during the growing season will keep the soil above the MLSN guideline, then that element is not required as fertilizer. In experiments with creeping bentgrass at Cornell University, a wide range of soil potassium levels were established in these research plots, but no beneft to applied potassium was observed even when the soil potassium levels were well below the conventional guidelines. Photos by Micah Woods

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