Submitted to: European Conference on Precision Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 16, 2003
Publication Date: June 15, 2003
Citation: Sadler, E.J., Camp Jr, C.R., Evans, D.E., Millen, J.A. 2003. Spatial variation of n fertilizer response in the southeastern usa coastal plain. In: Proceedings of 4th European Conference on Precision Agriculture, Wageningen Academic Press, Wageningen, The Netherlands. p. 603-608 (CDROM). Technical Abstract: Within the southeastern USA Coastal Plain, spatial variation in grain yield may justify site-specific management. Two experiments examining yield in response to irrigation and N for maize were conducted during 1999-2001 using center pivots modified to independently irrigate and fertigate 9 x 9 m plots. Under one pivot (CP2), we examined irrigation and N fertilizer response functions for twelve soil map units in a typical field, emphasizing soil variation and irrigation response. Under another (CP1), we examined the same responses on the predominant soil, emphasizing N response. N response was calculated as R = (YhiN - YloN) / (Nhi - Nlo), where Y is yield (kg/ha), N is N rate (kg/ha), and hi and lo indicate the specific N treatment. Under CP2, R ranged from -47 to 39 kg/kg in 1999, from -22 to 60 kg/kg in 2000, and from -30 to 50 kg/kg in 2001. Negative values suggested that N was not the yield-limiting factor. Spatial variation of R under CP1, on the more-uniform soil, was less but not negligible. In both cases, the response surface showed distinct spatial patterns. The challenge is to explain the causes and incorporate them into precision agriculture recommendations.