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Phosphorus Response of Corn on an Oxisol as Influenced by Rates and Placement¹

ABSTRACT

Phosphorus deficiency and high P sorbing capacities are a major limitation to intensive cropping of many soils in the Cerrado area of Central Brazil. A field study comparing rates and placement of P for corn (Zea may L.) was conducted to determine initial and long-term P fertilization requirements. Rates of broadcast P were 70, 140, 280, and 560 kg P/ha and banded rates were 35, 70, and 140 kg P/ha. In addition, combination treatments of 140 or 35 kg P/ha broadcast and banded rates of 35 kg/ha per crop were used.

Broadcast treatments gave greater yields than band treatments at the same rates for the first crop. At the end of four crops, however, total yields and P uptake were very similar for broadcast and band treatments in which the same total amount of P had been applied. Marked residual effects were observed with the higher rates of broadcast P.

A greenhouse study was conducted in which a given amount of P was mixed with varying proportions of the total soil volume. Corn growth and P uptake were a function of both the concentration of P in the portion of the soil fertilized and the percent of the total soil volume that was fertilized. These results tend to explain the increase with time in relative yields of the banded treatments.

The best method for applying P to these high adsorbing soils appears to be an initial broadcast application of 140 kg P/ha and a band application of 35 kg P/ha to each crop. This treatment maintained the available soil P at the critical soil test level and produced 80 to 85% of the maximum yield.

¹ Paper no. 5696 of the Journal Series of the North Carolina Agric. Exp. Stn., Raleigh, NC 27650. This research was supported by the Agency for International Development under contract ta-C-1236 and was conducted in cooperation with the Department of Agronomy, Cornell University and CPAC/EMBRAPA, Brasilia, Brazil.

² Former Graduate Research Assistant, North Carolina State Univ. (now Assistant Soil Scientist, Dep. of Agronomy & Soil Science, Univ. of Hawaii); Professor, Dep. of Soil Science, North Carolina State Univ.; Coordinator, Project of Resource Utilization, CPAC, Brasilia, Brazil; and former Research Associate, Cornell Univ. (now Assistant Professor, Dep. of Soil Science, North Carolina State Univ.), respectively.

Received for publication July 25, 1978. Accepted for publication November 29, 1978.