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Assess the benefit of using management zones versus grids for sampling

Feb 19, 2014

Question: We have done 2.5 acre grid samples the last two years and spread fertilizer with the grids. Can I move out to 10-acre grids and get average and get the same results? We are in the southeast part of Georgia.

Answer: I would not let a grid establish how I pulled the samples.  I would look for any information I can get for how the field yields to start with.  However the field yields is how it should be sampled.  I like to lay soil types down first and then the yield maps and aerial imagery of fields over my soil maps to refine the zones.  I always respect my soil types and then subdivide those soil types down into zones based on water drainage, water availability and crop growth. Instead of looking at 2.5-acre or 10-acre grids, I would look at your yield maps.  If you don’t have yield maps in cotton and peanuts, I would look at aerial imagery (NDVI) as well as thermal imagery to help me define how the field yields. Take the high, medium and low yields in the field – that’s how it should be mapped out and sampled so you have a better picture.  Your yield map and soil test map should correlate. Granted, yield maps in corn are easy to get, while cotton and peanuts may be a lot harder to do. If that’s the case, I would rely on NDVI or thermal imagery to help me have a good map, and then I would sample it by management zones not grids.  A management zone can vary in size.  Some might be 10 acres in size and others as small as 2 acres.  Let soil type, topography, fertility and yield history separate the field out into management zones.  By that I mean, for example, with corn if I have one area making 220 bushel/acre consistently and another area making 150 bushel/acre, those are two separate management zones. If you know how that field yields, that’s how it should be tested.

How to Navigate Zone Management

Every risk has its reward. With zone management, the reward is higher yields and profitability. How to navigate zone management decisions to realize the benefits of variable-rate technology over time.


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Chris Barron of Carson and Barron Farms in Rowley, Iowa, has spent the past few months planning and preparing his crew to test the zone management waters


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