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Nitrogen Fertilization of Maize on an Oxisol of the Cerrado of Brazil¹

Information about N management for crop production on the highly weathered, tropical Oxisols is limited. Six crops of ‘Cargill 111‘ maize (Zea mays L.) were planted on an Oxisol (Typic Haplustox, fine, kaolinitic, isohyperthermic) of the Cerrado of Brazil to 1) define the N fertilizer response curve; 2) estimate increase in N content of aboveground dry matter per unit fertilizer; 3) estimate soil N supply; 4) determine the effects of timing of application on yield and N recovery; and 5) compare conventional and S-coated urea. Treatments included sidedressed urea at 0, 60, 8O, 100, and 140 kg/ha with 20 kg/ha applied at planting and the remainder 30 days later, sidedressed urea at 100, 140, and 220 kg/ha with 20 kg/ha applied at planting and the remainder equally split and applied 20 and 60 days later, 100 kg/ha limecoated NH₁NO₃ and 140 kg/ha sulfur-coated urea. Grain and stover yields were measured for each crop and subsamples collected for N analysis. Soil samples were collected throughout the experiment and analyzed for organic N. Yield increased significantly with N fertilization. Average maximum grain yield of 6.1 metric tons/ ha resulted from ap lication of 203 kg/ha N. Recovery of fertilizer N variezwith application rate from 60% at 60 kg/ha to 35% at 220 kg/ha. A single application of fertilizer 30 days after planting produced the same yield and N recovery as split applications at 20 and 60 days. Neither Scoated urea nor lime-coated NH,NO, pro. duced greater yield or N recovery than conventional urea. Average N content of above-ground dry matter at maximum yield was 1.18%. Average uptake of soil N was 70 kg/ha/crop. There appears to be no fundamental difference in response of maize to N fertilizer between Oxisols and soils of the temperate regions.

Key Words: Soil N • Fertilizer N recovery • Sulfur-coated urea • Oxisol • Tropical soils

² Research support specialist and research associates. Agronomy Dep., Cornell Univ., Ithaca, NY 14853, respectively. Dr. Ritchey's current address: CPA Cerrados/EMBRAPA, Planaltina, DF, Brazil. Dr. Naderman's current address: Dep. of Soil Science, North Carolina State Univ., Raleigh, NC 27607.

Received for publication May 10, 1979.