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This article in AJ

  1. Vol. 96 No. 1, p. 26-33
     
    Received: May 3, 2003
    Published: Jan, 2004


    * Corresponding author(s): apmallar@iastate.edu
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doi:10.2134/agronj2004.2600

Comparison of Uniform- and Variable-Rate Phosphorus Fertilization for Corn–Soybean Rotations

  1. David J. Wittry and
  2. Antonio P. Mallarino *
  1. Dep. of Agron., Iowa State Univ., Ames, IA 50011

Abstract

Variable-rate (VR) technology can be used to vary fertilization rates within a field. The objective of this study was to compare VR and uniform-rate (UR) P fertilization for corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations. Grid soil sampling (0.2- to 1.7-ha cells), differential global positioning systems (DGPS), and grain yield monitors were used in strip trials established on six fields (12 site-years). Three replicated P fertilization treatments were a control (no P) and a single application of the P requirement of the 2-yr rotation based on soil-test P (STP) using UR or VR. Measurements were plant dry weight (DW), P concentration (PC), and P uptake (PU) when crops were 15 to 20 cm tall; grain yield; and STP after crop harvest. Phosphorus increased grain yield (P ≤ 0.05) of five crops, and the fields had initial mean STP ≤ 16 mg kg−1 (Bray-P1 or Mehlich-3). Phosphorus increased plant DW, PC, and PU of five, six, and seven crops, respectively. Within each field, yield responses were observed only in areas with STP < 20 mg kg−1 and (or) areas with Clarion soil (fine-loamy, mixed, mesic, Typic Hapludoll). The responses of plant DW, PC, and PU were not related to STP or soil series. The fertilization method did not influence (P ≤ 0.05) crop responses to P. However, VR fertilization resulted in better P fertilizer management because it applied 12 to 41% less fertilizer and reduced STP variability compared with the traditional UR fertilization method.

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