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Corn

Growth, Yield, Quality, and Economics of Corn Silage under Different Row Spacings

^a Dep. of Crop and Soil Science
^b Northwest NY Dairy, Livestock, and Field Crops Cooperative Extension
^c Dep. of Applied Economics and Management, Cornell Univ., Ithaca, NY 14853

^* Corresponding author (wjc3{at}cornell.edu)

Received for publication May 4, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Corn (Zea mays L.) silage in the northeastern USA yields more in narrow (0.38 m) than conventional (0.76 m) rows. Dairy producers, however, have considered converting from conventional to twin rows (0.19 m on 0.76 m centers) because twin rows are more compatible than narrow rows for herbicide application on glyphosate-resistant corn. Two hybrids were planted in field-scale studies in New York in 2003 and 2004 to evaluate growth, yield, quality, and economics of corn silage under conventional, narrow, and twin row production systems. Narrow rows had greater dry matter yield (17.6 Mg ha^–1) than twin (17.2 Mg ha^–1) and conventional rows (16.6 Mg ha^–1). Row spacing did not affect in vitro true digestibility. Narrow and twin rows had greater fixed and variable costs associated with equipment requirements. Partial budget analyses indicated greater expected increases in annual profit with the conversion from conventional to narrow rows for 262 ($18 201) and 525 ha ($38 317) or to twin rows for 262 ($8246) and 525 ha ($17 584) of corn silage. The use of glyphosate-resistant corn in twin rows may provide an advantage by delaying herbicide application until mid-June, thereby increasing the probability of a timely first harvest of perennial forages. Dry matter content at harvest averaged 326 g kg^–1 in narrow versus 314 g kg^–1 in twin rows, increasing the probability of corn silage harvest before a fall frost. Dairy producers should consider economics and timely harvests when considering corn silage row-spacing systems.

Abbreviations: DM, dry matter • hp, horsepower • IVTD, in vitro true digestibility

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
SOME managers of large dairy operations in the northeastern USA adopted narrow-row (0.38 m) corn silage production in the 1990s because narrow rows consistently yield 4–7% more than conventional (0.76 m) rows (Cox et al., 1998; Cox and Cherney, 2001; Cox and Cherney, 2002). One deterrent to narrow-row corn, increased corn rootworm (Diabrotica sp.) insecticide costs associated with more corn rows (Hallman and Lowenberg-DeBoer, 1999), no longer exists because of the commercial release of in-plant corn rootworm protection or the use of seed-applied insecticides. Another deterrent, mechanical damage to corn plants with postemergence herbicide application, still exists. Many dairy farmers, including narrow-row corn silage producers, are interested in the use of glyphosate-resistant corn because it may delay herbicide application to corn until after the first harvest of perennial forages (Cox and Cherney, 2005). A twin-row corn silage system would allow for the use of glyphosate-resistant corn, but it is not known if twin rows would yield and increase profit more than conventional rows.

Twin-row corn studies have mostly been limited to grain corn. Twin-row (0.3 m apart on 0.76 m centers) corn yielded 6.5% more than single-row (0.96 m) corn in an irrigated study on the Atlantic Coastal plain of the USA (Karlen and Camp, 1985). Ottman and Welch (1989) reported that twin-row (0.13 m apart on 0.76 m centers) yielded similarly to single-row (0.76 m) corn in an Illinois study. In Ontario, Canada, Ma et al. (2003) reported that twin-row (0.2 m apart on 0.76 m centers) yielded similarly to single-row (0.76 m) corn in 3 yr but yielded 11% less in an exceptionally wet and cool year. Recent field-scale research (Finck, 2003; Finck, 2004; Finck, 2005) has shown a numerical yield advantage for twin-row (0.19 m apart on 0.76 m centers) versus single-row (0.76 m) corn in many but not all comparisons in the corn belt of the USA. In a corn silage study in the Puget Sound Region of Washington, Jellum and Kuo (1990) reported that twin-row (0.3 m apart on 1.5 m centers) yielded the same as single-row (0.76 m) corn, but they did not examine silage quality in this study.

An economic analysis is necessary to fully evaluate the adoption potential of new technology. Hallman and Lowenberg-DeBoer (1999) reported that narrow-row grain corn production has potential economic advantages in the northern Corn Belt. Cox et al. (1998) reported that the conversion from conventional (0.76 m) to narrow-row (0.38 m) corn was profitable for dairy producers in the northeastern USA who plant 160 ha or more of corn silage. To the best of our knowledge, no economic studies have evaluated the conversion from conventional or narrow to twin-row corn silage production. The objectives of this study were to evaluate (i) final plant densities and early growth; (ii) yield and quality; and (iii) relative economics of corn silage in conventional (0.76 m), narrow (0.38 m), and twin rows (0.19 m apart on 0.76 m centers).

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Farmer-researcher partnerships (Karlen et al., 1995) were formed to conduct field-scale studies on a 950-cow (Bos taurus) dairy farm at an elevation of 550 m near Warsaw, NY (42°68' N lat; 78°22' W long). Owners of the dairy farm, who adopted narrow-row corn silage in the mid-1990s, plant about 265 ha of corn silage with a 15-row Kinze (Williamsburg, IA) planter. Owners of the neighboring dairy farm leased a 9.1-m wide Precision Drill (Great Plains, Salina, KS) in 2003 to compare its performance with their 12-row planter for planting 525 ha of corn silage. In 2003 and 2004, field-scale studies were established in a 20-ha field that had a predominant soil type of Bath silt loam (coarse-loamy, mixed, mesic Typic Fragiochrepts) on third- and fourth-year corn, the final 2 yr of the typical 4-yr corn and 4-yr perennial forage rotation used on dairy farms. Soil tests in 2003 and 2004 indicated a pH in the 7.0 range and high values of P and K.

Employees on the dairy farm performed most field operations, including manure applications, tillage practices, planting narrow and conventional-row corn, pesticide spraying, and harvesting. Approximately 100 000 L ha^–1 of dairy manure (3.0–3.2 g kg^–1 of total N with 1.4–1.5 g kg^–1 in the organic fraction and 1.5 g kg^–1 of NH₄-N) were injected into frozen soil in early March of both years. The goal was to achieve an N fertility status of about 180 kg ha^–1, including N credits from previous manure applications and the previous alfalfa crop. The field was moldboard plowed in early May of both years and cultipacked the day before planting.

Medium-round kernels of two hybrids (Pioneer brand 36N70 and Mycogen brand 3681FQ) were planted on 18 May 2003 and 13 May 2004 at 86 500 kernels ha^–1 under three row spacings (0.76, 0.38, and 0.19 m twins centered at 0.76 m) in a randomized, complete-block design in a split-plot arrangement with four replications. Row spacings were main plots, and hybrids were subplots. The 0.76 and 0.38 m treatments were planted with the 15-row Kinze planter (alternate rows shut off for the 0.76 m spacing). The twin-row treatment was planted with the Precision Drill. A single pass was made for each hybrid with each planter (6 m for the Kinze and 9.1 m for the Precision Drill), which maintained adequate border area between plots at harvest. Soil insecticide was not used in 2003, but no visible corn rootworm damage was observed. In 2004, each hybrid was treated with the seed-applied insecticide, clothianidin [(E)-1-(2-chloro-1,3-thiazol-5-ymethyl)-3-methyl-2-nitroguanidine], at 1.25 mg a.i. kernel^–1. Pre-emergence herbicides were applied shortly after planting, and virtually no weeds were observed when final plant densities were determined.

Final plant densities were estimated at the eighth leaf stage (V8) (Ritchie et al., 1993) by counting all the plants along the entire 350-m length in rows 3 through 7 in the conventional and narrow-row plots and in rows 5 through 9 in the twin-row plots. On the same day, four plants were harvested every 35 m, starting at 10 m, along the entire plot length for a total of 40 plants per plot. The samples were dried at 60°C in a forced-air dryer to constant moisture. Dry matter (DM) accumulation for each treatment was estimated on a per area basis, based on dry weight and final plant densities.

The entire lengths of rows 2 through 13 in narrow, rows 2 through 7 in conventional, and rows 3 through 9 in the twin-row plots were harvested with a New Holland (New Holland, PA) self-propelled forage harvester equipped with a 4.5-m-wide rotary head in late September of both years when whole plant DM contents of both hybrids averaged about 310 g kg^–1. The forage harvester blew the corn silage into one of three trailing trucks, which were previously tared for weight. After each pass, each truck was weighed on permanent platform scales, and the silage was dumped at the edge of a nearby bunker silo. Before the silage was packed in the bunker silo, 20 grab samples (5000 g) were taken from throughout the silage pile to estimate DM content and in vitro true digestibility (IVTD). The harvest samples were immediately sealed in plastic bags, driven to a Cornell Research Farm, weighed, dried at 60°C in a forced-air drier until constant moisture, and weighed again. The harvest samples were ground sequentially through hammer and Wiley mills. Samples were repeatedly passed through a splitter until reduced to 50 g and further ground through a cyclone mill (Udy Corp., Ft. Collins, CO) fitted with a 1-mm screen. Samples (0.5 g) were analyzed by wet chemistry for IVTD according to stage 1 of the procedure described by Marten and Barnes (1980).

Row spacing and hybrid were considered fixed, and replications and years were considered random effects in the analysis of variance. Combined analyses across years and separate analyses within years were conducted for plant densities, DM accumulation at the V8 stage, DM content at harvest, DM yield, and IVTD using General Linear Model procedures of the SAS statistical package, version 7.0 (SAS Institute, 1998). The Bartlett test, which tested for homogeneous variances across years at = 0.05, indicated homogeneous variances for all variables. The effects of the combined analyses were considered significant at = 0.05. Fisher's protected LSD (P = 0.05) was used to separate means when main effects tested significant.

A partial budget approach was used to estimate the expected change in annual profit in an average future year for both farms and to determine the feasibility of the purchase of a new corn planter. Consequently, the expected change in profit was estimated for converting from conventional to twin-row, from conventional to narrow-row, and from narrow to twin-row spacing for farms that produce 262 and 525 ha of corn silage, the only row crop produced on both farms. The analyses accounted for added annual fixed costs that included depreciation (straight line), interest to reflect the opportunity costs of capital, insurance, and housing, associated with the purchase of a new corn planter, the use of a different tractor for planting (if necessary), and the purchase of a new forage head for harvesting (if necessary). We used manufacturers' suggested list prices obtained from local agricultural implement dealers to estimate ownership and operating costs of a new 12-row Kinze Twinline Planter (Model 3600), a 23-row (narrow) Kinze Twinline planter (Model 3600), a 9.1-m wide Great Plains Precision Drill (Model 3N-3010P), a 215-hp John Deere (Moline, IL) tractor (Model 8320) to pull the Precision Drill, a 170-hp John Deere tractor (Model 8120) to pull the Kinze planters, a six-row New Holland rotary corn silage harvester head (Model R1450) to harvest narrow-row corn silage, and a six-row New Holland conventional width corn silage harvester head (Model 360N6) to harvest conventional and twin-row corn silage. We assumed that both tractors were part of the farm businesses' current machinery complement. Annual variable costs included labor, fuel, lube, repair, and maintenance costs of equipment where appropriate (ASAE, 2000). All other management inputs in this study were similar across row spacings and are expected to remain similar, so variable costs were associated only with equipment changes and hauling and silo filling of different corn silage yields. Expected changes in income were generated from average corn silage yields for each row-spacing treatment and average corn silage price ($82 Mg^–1) in New York for 2003 and 2004 (New York Agric. Stat. Service, 2004). All dollar values for income and cost items are expressed in real terms as current 2004 dollars. The expected changes in profit reflected differences in total net income (increases or decreases) and differences in costs (increases and decreases) for the two dairy farms in this study for a future average year.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Weather conditions were remarkably similar across growing seasons. Precipitation measured at the dairy farm from May through September totaled 513 mm in 2003 and 509 mm in 2004. Precipitation in July totaled 109 mm in both years. Temperatures at the nearest weather station in Warsaw, NY averaged 18.8°C in July 2003 and 18.6°C in July 2004. Both hybrids reached the R1 growth stage in late July of both years. The major differences between growing seasons occurred in August, with 152 mm of precipitation and average temperatures of 20.2°C in 2003 and 47 mm of precipitation and average temperatures of 17.0°C in 2004. Nevertheless, DM yields averaged essentially the same in 2003 (17.3 Mg ha^–1) and 2004 (17.1 Mg ha^–1).

Row spacing and hybrid did not affect plant densities, and a row spacing x hybrid interaction did not exist (Table 1). Twin-row corn, planted with a Precision Drill, has had lower plant densities when compared with conventional rows in other field-scale studies because of less firming above the seed with the Precision Drill (Finck, 2003) and because the planting meter nipped the tips of some seeds in the planting operation (Finck, 2004). Frequent rains in May (113 mm in 2003 and 203 mm in 2004) maintained wet soil conditions after planting, which may have mitigated potential emergence problems with use of the Precision Drill. Final plant densities were close to optimum for corn silage yield and quality in narrow and conventional rows under growing conditions in the northeastern USA (Cox et al., 1998).

Narrow-row corn had 12 g kg^–1 greater DM content at harvest compared with conventional- and twin-row corn (Table 2). The hybrid 36N70 also had 14 g kg^–1 greater DM content than 3681FQ, and there was no row spacing x hybrid interaction. Dairy producers who have bunker silos should begin corn silage harvest at DM contents of about 310 g kg^–1 (Cox and Cherney, 2005). A 12 g kg^–1 greater DM content would allow dairy producers to begin corn silage harvest about 3–4 d earlier if harvest begins in late September in New York. A 3- to 4-d earlier harvest is an advantage in the northeastern USA where frost or wet soil conditions are threats in late September or early October. If dairy producers in the northeastern USA converted from narrow- to twin-row corn, they would lose the potential advantage of beginning and ending corn silage harvest 3–4 d earlier.

Dairy producers evaluate silage quality in addition to DM yield when selecting the best management practices for corn silage production. Row spacing and hybrid did not affect IVTD in this study, and there was no row spacing x hybrid interaction (Table 2). Previous studies have reported similar IVTD concentrations and overall silage quality between conventional- and narrow-row corn silage (Cox et al., 1998, Cox and Cherney, 2001; Cox and Cherney, 2002; Widdicombe and Thelen, 2002). Apparently, the conversion from conventional- to twin-row corn silage does not affect silage quality.

Changes in fixed and variable costs in our partial budget analyses were associated with differences in initial capital and operating costs for equipment requirements for conventional-, twin-, and narrow-row corn silage systems (Tables 3 and 4). For example, the Precision Planter, which costs $83 000 (compared with $62 000 for the 12-row Kinze planter), required a 215-hp tractor that costs $18 000 more than a 170-hp tractor for planting. Likewise, narrow-row corn silage requires a rotary harvesting head, which costs $18 000 more than a conventional harvesting head. Consequently, twin- and narrow-row corn silage systems incur greater annual equipment costs (ownership and operating) compared with conventional-row systems.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Only a limited number of dairy producers in New York have converted from conventional- to narrow-row corn silage, despite economic analyses that indicate expected increases in profit (Cox et al., 1998). Potential mechanical damage to corn with the use of postemergence herbicides or during the occasional sidedress N application in very wet springs explains, in part, the limited adoption to date. Skip-row planting, which would leave two 0.76-m gaps for tractor wheels on a wide-boom sprayer, could alleviate the mechanical damage problem in narrow-row corn silage but at some loss in DM yield.

Twin-row corn, which is compatible with postemergence herbicide and sidedress N applications, also resulted in an expected increase in profit when compared with conventional-row corn. Based on the economic analyses reported here, however, narrow-row corn silage can provide a greater expected increase in profit than twin-row corn silage. In addition to economic analyses, dairy producers will likely consider the management of the overall farm operation, including the potential for a more timely first harvest of perennial forages with the use of glyphosate-resistant corn in twin rows. On the other hand, narrow-row corn silage dries down more rapidly than twin-row silage, allowing for an earlier harvest, which could result in greater silage yields and quality in cool years with early fall frosts. Dairy producers must consider a number of factors before deciding on a row spacing system for corn silage. Managers of the dairy farm in this study that produced 525 ha of corn silage purchased the Precision Drill after the 2003 growing season and planted twin-row corn, 50% of which was glyphosate resistant in 2004. The manager of the dairy farm that produced 262 ha of corn silage kept the narrow-row Kinze planter and applied pre-emergence herbicides on all the corn silage in 2004.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Cox, W. J. Articles by Cherney, J. H. Search for Related Content PubMed Articles by Cox, W. J. Articles by Cherney, J. H. Agricola Articles by Cox, W. J. Articles by Cherney, J. H. Related Collections Economics Maize Production Agriculture