Yield-based management zones and grid sampling strategies: Describing soil test and nutrient variability

Alternatives such as yield-based management zones may solve problems associated with grid soil sampling while effectively describing soil test and nutrient variability. The main objective was to delineate yield-based management zones using multiyear yield data and compare them with whole-field average and grid soil-sampling methods to determine the most effective strategy for describing soil test and nutrient variability. Research was conducted in four continuous no-till fields that had varied cropping histories and yield monitor data for at least 3 yr from 1996 through 2000. Four yield-based management zone methods, (i) mean normalized yield map (MNY), (ii) coefficient of variation map (CVM), (iii) MNY X CVM, and (iv) yield region map (YRM), were evaluated. Three grid soil-sampling strategies, (i) grid cell, (ii) grid center, and (iii) grid center with kriging at two sampling distances (68 and 98 m), were also tested. Grid cell sampling consistently captured more soil test and nutrient variability than the grid center and grid center with kriging methods. Of the yield-based management zone strategies, YRM was the most effective and in all four fields explained more soil test and nutrient variability compared with the whole-field average approach. Yield region map also performed better than or similar to the 98-m grid center and 98-m grid center with kriging strategies. When the field had low soil test values, YRM was also nearly as effective in capturing nutrient recommendation variability as the 98-m grid cell method. However, compared with all other strategies, the 68-m grid cell method was the most effective way to describe soil test and nutrient variability.