Remote sensing-informed variable-rate nitrogen management of wheat and corn: agronomic and groundwater outcomes

• Published in: Agronomy journal Vol. 98; no. 2; pp. 327 - 338
• Main Authors: Hong, N, White, J.G, Weisz, R, Crozier, C.R, Gumpertz, M.L, Cassel, D.K
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy 01-03-2006
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; corn; crop management; crop rotation; fertilizer application; fertilizer rates; Fundamental and applied biological sciences. Psychology; Glycine max; grain yield; groundwater contamination; nitrogen; nitrogen fertilizers; nutrient uptake; nutrient use efficiency; precision agriculture; Remote sensing; soybeans; Triticum aestivum; wheat; Zea mays; North Carolina; Nitrogen fertilization; Monocotyledones; Variable; Zea mays; C4-Type; Cereal crop; Remote sensing; Triticum; Gramineae; Agronomy; Angiospermae; Spermatophyta; Ground water
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2005.0154

In-season, site-specific, variable-rate (SS) N management based on remote sensing (RS) may reduce N losses to groundwater while maintaining or increasing yield and N fertilizer-use efficiency. We compared in-season, RS-informed N management applied on a uniform, field-average (FA) or SS basis with the current uniform best management practice (BMP) based on "Realistic Yield Expectations" (RYE) in a typical 2-yr southeastern U.S. coastal plain rotation: winter wheat (Triticum aestivum L.)-double-crop soybean [Glycine max (L.) Merr.]-corn (Zea mays L.). Compared with the RYE-based BMP, RS-informed SS management achieved: (i) a maximum of 2.3 mg L(-1) less groundwater NO3-N after 2001 wheat due to 39 kg ha(-1) less fertilizer N and a 25% greater harvest N ratio (N in grain or forage/total N applied); (ii) 370 kg ha(-1) more 2002 corn grain with 32 kg ha(-1) greater N applied, similar harvest N ratio, and 37 kg ha(-1) greater surplus N; (iii) 670 kg ha(-1) more 2003 wheat grain associated with 14 kg ha(-1) greater fertilizer N, 27% greater harvest N ratio, and 9 kg ha(-1) less surplus N. Excepting one corn FA treatment that received excessive N, RS-informed management produced equal or greater economic returns to N than RYE, and less surplus N for wheat. Treatments produced enduring effects on groundwater [NO3-N] consistent with agronomic results, but small relative to temporal [NO3-N] fluctuations that were positively correlated with water table elevation. To assess N management in leaching-prone soils, frequent, periodic groundwater monitoring during and after the cropping season appears essential.