Row Spacing, Hybrid, and Plant Density Effects on Corn Silage Yield and Quality

Considerable interest exists in New York for narrow row corn (Zea mays L.) silage production because farmers, who converted from 30- to 15-in. row spacing, report yield increases of 3 to 4 tons/acre. We evaluated eight hybrids at densities of 18 000, 24 000, 30 000, 36 000, and 42 000 plants/acre in 1994, 1995, and 1996 to compare yield, quality, and economics of corn silage production at 15- and 30-in. row spacings. When averaged across years, hybrids, and densities, corn silage yielded 24.9 tons/acre at 15 in. and 23.9 at 30 in. row spacing. Row spacing × hybrid and row spacing× plant density interactions did not exist. When averaged across years, hybrids, and row spacings, maximum economic yields occurred at about 39 500 plants/acre. In vitro true digestibility (IVTD), however, had a 0.1% decrease and neutral detergent fiber (NDF) had a 0.13% increase per 1000 plant/acre increase. Consequently, estimated maximum economic milk yield occurred at about 35 000 plants/acre. Partial budget analyses indicated that farmers who produce 200 acres of corn silage might expect a slight loss in annual net farm income (−$696) with the conversion from 30- to 15-in. row spacing. Farmers, who produce 400 and 800 acres of silage, might expect modest ($3116) and significant gains ($11 624) in annual net farm income, respectively. We have initiated field-scale trials on a dairy farm to further assess the potential for narrow row corn silage production in New York. Research QuestionConsiderable interest exists in New York for narrow row corn silage production because silage producers, who have converted from 30- to 15-in. row spacing, report 3 to 4 tons/acre greater yields. Narrow row corn silage producers in New York plant at 45 000 to 50 000 kernels/acre because on-farm observations suggest that corn responds best to 15-in. rows under high populations. Unfortunately, limited documented research exists on the yield, quality, and economics of corn silage production under narrow rows and high populations. Objectives of this study were to: (i) compare yield and quality characteristics of corn silage production at 15- and 30-in. row spacings, (ii) determine whether row spacing × hybrid interactions exist for yield and quality, (iii) determine whether row spacing × plant density interactions exist for yield and quality, and (iv) evaluate the economics of converting from 30- to 15-in. row spacings in New York. Literature SummaryRecent narrow row corn research reported about a 4% average grain yield response to narrow rows with no spacing by plant density interaction. Grain corn, however, had about an 8% average yield response to narrow rows in northern latitudes. No recent published research has evaluated corn silage yield and quality characteristics under narrow rows. Studies in the late 1960s and early 1970s reported inconsistent yield responses to narrow rows. A study in Georgia reported greatest silage yields under narrow rows and high densities at one site, but under wide rows and low densities at another site. A study in New York reported that row spacing did not affect silage yields and that a hybrid × row spacing interaction did not exist. A study in Virginia, however, reported that one hybrid yielded best under narrow rows and high densities, whereas another hybrid yielded best under wide rows and low plant densities. Study DescriptionEights hybrids, 100 to 112 d in relative maturity, were evaluated at plant densities, of 18 000, 24 000, 30 000, 36 000, and 42 000 plans/acre under 15- and 30-in. row spacings at Aurora, NY, in 1994, 1995, and 1996. The experimental design was a randomized complete block in a split-split-block arrangement with hybrids as main plots (110 by 20 ft.), row spacings as sub-plots (110 by 10 ft.), and plant densities as sub-subplots (22 by 10 ft.). Individual hybrids were harvested over a 15-d period at about 65% whole plant moisture. A six-plant sub-sample was used to estimate whole plant moisture, grain content, in vitro true digestibility (IVTD), neutral detergent fiber (NDF), NDF digestibility, and crude protein (CP). The Milk90 spreadsheet estimated yield of milk per acre based on the yield and quality data. Regression analyses estimated silage yield, IVTD, NDF, NDF digestibility, CP, and milk yield responses to plant density at both row spacings in each year of the study. A partial budget approach, which accounted for total annual variable and fixed costs, associated with the purchase of new planters and forage harvesters, silage yield, and price data, estimated the expected change in net farm income in an average future year for converting from 30- to 15-in. row spacing on a fann that produces 200, 400, and 800 acres of corn silage. Applied QuestionsHow does 15- vs. 30-in. row spacing affect yield and quality of corn silage? When averaged across hybrids and plant densities, 15- vs. 30-in. row spacing increased silage yields by 1.5 tons/acre in 1994 and 1996, but did not affect silage yields in 1995. When averaged across years, 15- vs. 30-in. row spacing yielded 1 ton/acre or 4.2% greater. Row spacing did not affect silage quality characteristics in any year of the study. Should plant density be adjusted for row spacing when planting corn silage? When averaged across hybrids, silage yields had quadratic responses to plant densities under both row spacings in each year of the study. Row spacing × plant density interactions did not exist for yield and quality characteristics in any year of the study. Based on the yield data, corn silage producers in New York should plant at the same density under 15- and 30-in. spacings. When averaged across years, hybrids and row spacings, maximum economic silage yields occurred about 39 500 plants/acre. Maximum economic milk yields, however, occurred at about 35 000 plants/acre because silage quality decreased as plant densities increased. Are hybrids affected by row spacing? Hybrids affected silage yield and quality characteristics in all years of the study. Hybrid × row spacing interactions did not exist for yield and quality characteristics in any year of the study. Apparently, none of the hybrids in this study were better adapted than other hybrids to narrow rows. When averaged across years, hybrids varied in IVTD and NDF by 3.4 percentage units, NDF digestibility by 5.2 percentage units, and CP by 0.7 percentage units. Differences in silage quality characteristics among hybrids were consistent across years, despite different growing conditions. What are the economics of converting from 30- to 15-in. row spacing? The purchase of a new corn planter and forage harvester for 15- vs. 30-in. row spacing had greater initial capital costs and subsequent annual fixed and repair costs. The added income, associated with greater silage production, at 15- compared with 30-in. row spacing did not offset the added total costs on a farm that produces 200 acres of corn silage. The added income at 15- compared with 30-in. row spacing exceeded added costs by about $3000 on a farm that produces 400 acres of corn silage. Other potential costs, however, associated with narrow row corn silage production, such as greater soil insecticide use for corn root-worm control because of more rows in 15-in. row spacing, could exceed $3000, thereby nullifjing the potential profit for 15-in. row spacing on farms that produce 400 acres of corn silage. The added income at 15- compared with 30-in. row spacing exceeded added costs by about $11 500 on a farm that produces 800 acres of corn silage production. We recommend that corn silage producers, who grow about 600 acres or more of corn silage, should consider converting fiom 30- to 15-in. row spacing as a possible way to improve economic performance.