CORN RESPONSE TO ROW WIDTH AND PLANT-POPULATION IN THE NORTHERN CORN-BELT

There has been a trend toward narrower row width and an increase in pl ant population for corn (Zea mays L.) production in the northern Corn Belt. The impact of corn hybrid and plant population on grain yield ma y be influenced by row width. This study was designed to investigate t he relationships between row width, plant population, and hybrid at th ree Minnesota locations from 1992 through 1994, At Lamberton and Wasec a, row widths were 10, 20, and 30 in.; target populations were 25 000, 30 000, 35 000, and 40 000 plants/acre; and hybrids were Ciba 'G4372, ' DeKalb 'DK512,' and Pioneer Brand 'P3563', At Morris, the same row w idths were evaluated but the target populations were 22 000, 27 000, a nd 32 000 plants/acre and the hybrids were Northrup King 'N3624,' DeKa lb 'DK421,' and Pioneer Brand 'P3751'. At Lamberton and Waseca, the yi eld advantage for both 10- and 20-in. rows compared with 30-in, rows w as 7.2% when averaged over all hybrids and all plant populations, wher eas at Morris the yield advantage was 8.5%. Choice of hybrid influence d grain yield, and all hybrids responded similarly to change in row wi dth and change in plant population at the three locations, Grain yield s increased at Lamberton and Waseca with higher plant populations in 1 992 and 1994, but not in 1993 when yields were limited by climatic con ditions, Regression analysis of yield vs, harvest plant population sho wed yields were highest at populations at or above 35 000 plants/acre in 1992 at Lamberton and 1994 at Waseca and Lamberton, but were unaffe cted by plant populations in 1992 at Waseca and in 1993 at both locati ons, At Morris, regression analysis of yield vs, harvest plant populat ion in 1993 and 1994 showed yields were highest at plant populations o f 32 000 plants/acre, the highest plant population studied at that loc ation, Choice of hybrid and the growing season climatic conditions had a greater effect on grain moisture content at harvest, test weight, a nd ear length than row width or plant population, These data show a yi eld advantage for narrowing row widths from 30 to 20 or 10 in., and th at in some years maximum yields were obtained at harvest plant populat ions substantially higher than the current Minnesota population of 26 400 plants/acre.