Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2004
Publication Date: 12/30/2004
Citation: Sharratt, B.S., McWilliams, D.A. 2005. Microclimatic and rooting characteristics of narrow-row versus conventional-row corn in the northern US corn belt. Agronomy Journal. 97:1129-1135.
Interpretive Summary: Narrow-row corn (row spacing less than 0.76 m) has been advocated in recent years as a method to increase grain yield in the northern US Corn Belt, but speculation abounds concerning the cause of this higher yield. Findings from this study suggest that grain production of narrow-row corn equals or exceeds that of conventional-row corn because corn sown in narrow rows has a more uniform root and leaf distribution that aids in exploiting soil water, capturing sunlight, and reducing soil evaporation and soil temperatures. Based upon sound scientific information gained from this study, extension agronomists and seed companies can now recommend that farmers use narrow row corn to bolster production.
Technical Abstract: Narrow-row corn (Zea mays L.) has been advocated in recent years for bolstering production in the northern US Corn Belt, but previous studies have failed to elucidate the complexity of factors that promote the production of corn sown in narrow rows. Therefore, this study was undertaken to more clearly define those agronomic and microclimatic factors that influence grain yield of corn grown in narrow and wide conventional rows. A split plot experimental design was established near Morris, MN with row spacing (0.38, 0.57, and 0.76 m) as the main treatment and corn hybrid (Pioneer 3893 and Dekalb 412 or Dekalb 417) as the secondary treatment. Plant stands were established to achieve the same density among treatments and weeds were controlled during the growing season. Root length density to a depth of 1.5 m, crop water use, interception of photosynthetically-active radiation (PAR) by the crop canopy, near-surface soil temperature, and soil evaporation were measured over the 1996, 1998, and 1999 growing seasons. Grain yield was similar for corn grown in narrow and conventional rows in 1996 and 1998, but was 10% higher for narrow-row corn in 1999. In addition, narrow-row corn had a more uniform distribution of roots as root length density at a depth of 0-0.5 m in the intrarow and interrow was 0.64x104 and 0.65x104 m m-3 for corn grown in 0.38 m rows, 0.73x104 and 0.58x104 m m-3 for corn grown in 0.57 m rows, and 0.87x104 and 0.42x104 m m-3 for corn grown in 0.76 m rows, respectively. This more uniform root distribution likely contributed to the greater soil water extraction and crop water use by corn grown in narrow rows, but only during 1999 when corn grown in 0.38, 0.57, and 0.76 m rows extracted 150, 137, and 122 mm of soil water and consumed 494, 467, and 462 mm of water, respectively. Corn grown in narrow rows also intercepted 5 to 15% more PAR on clear days and thereby promoted cooler soils (0.5°C lower in the interrow) and suppressed soil evaporation (0.1 to 0.5 mm less on select days) during vegetative growth as compared with corn grown in conventional rows. The results of this study suggest that any yield advantage to growing corn in narrow rows may be a result of establishing a more uniform root and leaf distribution that aids in exploiting the soil water and light resources and reducing soil evaporation and near-surface soil temperatures as compared with corn grown in wide conventional rows.