High rates of N loss have been observed from N fertilizers applied directly on the surface in no‐till corn ( Zea mays L.) production systems. Field experiments were conducted at four locations over a three‐year period to determine what effects N source and N placement had on N losses in both no‐till and conventional till corn production systems. Soils used were: Stoy loam, an Aquic Hapludalf; Clermont silt loam, a Typic Ochraqualf; Avonberg silt loam, an Aeric Fragiaqualf; Chalmers silty clay loam, a Typic Argiaquoll; and Lyles fine sandy loam, a Typic Haplaquoll. Nitrogen sources used were anhydrous ammonia (NH 3 ), urea‐ammonium nitrate solutions (UAN), solid urea and solid ammonium nitrate (NH 4 NO 3 ). Placement variables used were injection of NH 3 and UAN 20 cm below the soil surface and broadcasting UAN, urea and NH 4 NO 3 on the soil surface with no incorporation. Nitrogen rates used were 0 and 165 kg N/ha. Injecting NH 3 , or UAN below the surface resulted in consistently higher corn grain yields than applying UAN, NH 4 NO 3 or urea directly on the soil‐residue surface. Percent N in leaf and grain also reflected an increase in N use efficiency with subsurface N placement. Percent N in leaf was significantly higher where NH 3 or UAN were injected as compared to UAN or urea surface applied.
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Mengel et al. (1982) studied this question.