Jackie Lyn Guevara, & Kevin W. Frank
Abstract
A soil test interpretation philosophy (STIP) converts soil test concentration from laboratory soil analysis into nutrient recommendations. Recently, a new STIP called Minimum Levels for Sustainable Nutrition (MLSN) was introduced to provide a more sustainable approach for turfgrass fertilization. It was found effective and being adapted by turfgrass managers; however, there is a lack of peer-reviewed research on this topic. To have a better understanding about MLSN, the objective of this research was to evaluate and compare the effects of two STIP, MLSN and Sufficiency Level of Available Nutrient (SLAN), on a Penn ‘A-4’ creeping bentgrass green (Agrostis palustris Huds.) and on a mix of annual bluegrass (Poa annua) and Penncross creeping bentgrass green grown on United States Golf Association recommendation rootzone. Research was initiated in 2019 at the Hancock Turfgrass Research Center, Michigan State University. The three STIP treatments were MLSN, SLAN and a nitrogen fertilized control. Nutrient recommendation rate for each treatment were as follows: MLSN had 73.2 kg N, 37 kg P and 60.5 kg K ha-1 yr-1; SLAN had 73.2 kg N, 56.6 kg P and 222.9 kg K ha-1 yr-1; and the nitrogen fertilized control had 73.2 kg N ha-1 yr-1. These STIP plots were split into two traffic treatments: non-traffic and traffic. Turfgrass color, quality, and normalized difference vegetation index (NDVI) were measured biweekly. Soil samples were collected at 15 cm depth. Following one year of fertilizer treatments, P deficiency symptoms were only observed on nitrogen fertilized control plots. Also, SLAN had an increase of soil P and K levels, whereas MLSN retained initial soil P levels and had a decrease in soil K levels. There were no significant differences between STIP treatments for turfgrass quality, color and NDVI, whereas trafficked plots had lower turfgrass quality, color and NDVI compared to non-trafficked plots.
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