HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Smyth, T. J. Articles by Cravo, M. S. Search for Related Content PubMed Articles by Smyth, T. J. Articles by Cravo, M. S. Agricola Articles by Smyth, T. J. Articles by Cravo, M. S.

Phosphorus Management for Continuous Corn-Cowpea Production in a Brazilian Amazon Oxisol

Dep. of Soil Sci., North Carolina State Univ., Raleigh, NC 27695-7619
EMBRAPA/UEPAE de Manaus, Manaus, Amazonas, Brazil

^* Corresponding author.

Although Oxisols occupy extensive areas in the Amazon, few studies have addressed their fertilizer P requirements for sustained, long-term crop production. This field study was conducted to evaluate initial and long-term responses to P rates and placement by corn (Zea mays L.) and cowpea (Vigna Unguiculata L.) when grown in annual rotation during five consecutive years in a Xanthic Hapludox (clayey, kaolinitic, isohyperthermic) near Manaus, Brazil. Effects on yields of sole broadcast P rates of 0, 22, 44, 88 and 176 kg ha^–1 in split-plot combination with subplot banded P rates of 0, 11, 22 and 44 kg ha^–1 were evaluated over 11 total crops. Banded P at 11 kg ha^–1 was applied to every crop and rates of 22 and 44 kg P ha^–1 were only applied to the initial eight and four crops, respectively. Residual effect of broadcast P, as measured by both yields and Mehlich 1 soil P, were greater at high rates. Although cowpea yields were increased up to the highest band rate, no response in corn yields were observed beyond the rate of 22 kg P ha^–1. At equal amounts of applied P, banded P provided greater yields than broadcast P during the initial crops. Total corn and/or cowpea yields, after 11 crops, were similar for all broadcast and band combinations at equal amounts of total applied P. The absence of a cumulative yield difference among placement methods indicated that banded placement of 22 and 44 kg P ha^–1 to corn and cowpea, respectively, would be the best method of applying P to sustain long-term crop production under the manual tillage practices used in the region.

Received for publication March 23, 1989.