Corn Production as Affected by Daily Fertilization with Ammonium, Nitrate, and Phosphorus

Abstract

Manipulation of N fertilization to control NH+4/NO-3 ratios in the soil can affect corn (Zea mays L.) growth and yield. Field study of these effects, however, has been difficult to conduct because nitrification of NH+4 and/or NO-3 leaching often occurs during the growing season. The objectives of this 4-yr field experiment were to investigate the effects of daily fertilization with various N sources and P on corn growth and yield. Pioneer 3343 was fertilized with solutions of urea (U), NH4Cl, Ca(NO3)2(CN), or U + CN (1:1 N ratio) with and without a solution of H3PO4. Solutions were applied to the root zone with a porous pipe subirrigation system. Nitrogen sources caused changes in KCl-extractable soil NH+4 and NO-3. Dry matter accumulation was not affected by N source at any stage of corn development. The effects of N source on N uptake, P uptake, and root growth varied by year, showing no consistent superiority of any of the N sources used. Corn yield was larger when NO-3 was included as an N source (CN or U + CN) than when only U was used in 1991. In the next two years, yield was not affected by N source; in the last year, NH+4 (U or NH4Cl) increased yield compared with CN. There was little correlation between yield and root growth, N uptake, or P uptake. Overall, no clear difference for maximizing corn growth and yield was observed between NH+4, NO-3, or the mixture NH+4 + NO-3.