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On-Farm Soil Variability in New Mexico Cotton

Robert Flynn


 
ABSTRACT

Acceptability of variable rate fertilizer practices in New Mexico will only occur if the need for such technology can be proven. The first approach is to define zones or quantify soil nutrient variability through grid sampling. Three cotton fields were chosen in 1998 and 1999 to evaluate spatial variability using a 700 to 800 foot grid divided into 100' increments. Nitrate-N, phosphorus, potassium, pH, organic matter, and electrical conductivity were measured for each grid point and analyzed with ArcView Spatial Analyst. All samples for phosphorus measured below moderate levels while all points for potassium were above critical levels. Nitrate-N, however, was the most variable for all three fields in 1998 and suggests a potential need for further evaluation. In order for a producer to be 95% confident in lab results, anywhere from 4 to 48 sub-samples would be required for a composite sample depending on the field and parameter in question.



Reprinted from Proceedings of the 2000 Beltwide Cotton Conferences pp. 1444 - 1445
©National Cotton Council, Memphis TN

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Document last modified Saturday, Jun 17 2000