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Fertilizer and Soil Nitrogen Use by Corn and Border Crops in a Strip Intercropping System

Pioneer Hi-Bred International, Johnston, IA, 50131-0256
Dep. de Suelos, Fac. de Agronomia, Montevideo, Uruguay

Richard M. Cruse and Matthew M. Harbur

Dep. of Agronomy, Iowa State Univ., Ames, IA 50011

^* Corresponding author (ghaffarzm{at}phibred.com)

Corn (Zea mays L.) has greater yield potential when strip-intercropped than when monocropped, but this potential may be compromised by a failure to understand how N requirements change with row position and the possible N competition of adjacent crops. A four block, completely randomized, split-plot experiment was conducted on a Haig loam soil (fine, smectitic, mesic Vertic Argiaquolls) in southern Iowa, to determine crop utilization of N fertilizer pointinjected into corn rows. Nitrogen fertilizer uptake was evaluated in (i) corn rows injected with labeled N fertilizer; (ii) corn rows adjacent to the injected rows; and (iii) plants at the edge of the adjacent soybean [Glycine max (L.) Merr.J and oat (Avena saliva L.)-alfalfa (Medicago saliva L.) strips. Main treatments consisted of three tillage systems: conventional tillage (CT), reduced tillage (RT), and no-till (NT). Subplot treatments consisted of point injection of ^l5N-enriched NH₄NO₃ (67 kg N ha^–1) in-row at three row positions within the corn strips. Grain and stover yield, Kjeldahl N, and isotope composition of plant materials were determined. Corn yield and labeled-N recovery differed with tillage to the extent that tillage affected early and total season moisture availability. Labeled-N recovery in labeled rows did not differ with row position. Labeled-N recovery in unlabeled rows or crop borders was typically less than 5% of that recovered by labeled rows. Nitrogen is primarily recovered by the row to which it is applied; therefore, row-by-row precision applications seem to be an appropriate management tool.

Received for publication September 17, 1997.