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Agronomy Journal 94:321-325 (2002)
© 2002 American Society of Agronomy

CORN

Evaluation of Narrow-Row Corn Forage in Field-Scale Studies

William J. Cox*,a and Debbie J. R. Cherneyb

a Dep. of Crop and Soil Sci., Cornell Univ., Ithaca, NY 14853
b Dep. of Animal Sci., Cornell Univ., Ithaca, NY 14853

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

Received for publication April 3, 2001.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 
Some dairy producers in the northeastern USA grow corn (Zea mays L.) in narrow rows at high plant densities and N fertility. We evaluated first-year, second-year, and continuous corn in field-scale studies at 0.76- and 0.38-m row spacings at recommended densities ({approx}85000 plants ha-1) and N fertility ({approx}165 kg ha-1) and at 0.38-m spacing at high densities ({approx}100000 plants ha-1) and N fertility ({approx}225 kg ha-1) in 1998, 1999, and 2000 to determine if narrow-row corn forage requires high densities and N fertility for optimum yield and quality. Narrow-row corn at high vs. recommended densities and N fertility had similar soil NO3–N concentrations in the upper 0.3-m depth and whole-plant N concentrations at the sixth leaf stage of corn (V6) as well as similar ear-leaf N concentrations at silking in eight of the nine site-year comparisons. All treatments were above critical concentrations for soil NO3–N concentrations (>25 mg kg-1), whole-plant N concentrations (>35 g kg-1), and ear-leaf N concentrations (>25 g kg-1, except in the cool 2000 season). Consequently, narrow-row corn at high vs. recommended densities and N fertility had similar dry matter yield and quality in eight site-year comparisons. Furthermore, narrow-row corn at high vs. recommended densities and N fertility had greater residual soil NO3–N concentrations in three site-year comparisons. We recommended that dairy producers in the northeastern USA grow narrow-row corn forage at recommended plant densities and N fertility.

Abbreviations: DM, dry matter • GDD, growing degree days • IVTD, in vitro true digestibility • NDF, neutral detergent fiber


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 
SOME LARGE DAIRY PRODUCERS in the northeastern USA adopted narrow-row corn silage production in the mid-1990s. These producers, who believe that corn responds best to narrow rows under high plant densities and N, plant corn at about 125 000 plants ha-1 and fertilize at about 225 kg N ha-1 via animal waste application and previous legume crops in the rotation (Deibel, 1997). An additional benefit of growing narrow-row corn silage under high N fertility is that these large dairy producers can dispose of additional animal waste, which is often in excess on their farms. In a recent study, however, Cox and Cherney (2001) reported no row spacing x plant density x N rate interactions for corn dry matter (DM) yield and forage quality. Consequently, they recommended the same harvest plant densities (80000–85000 plants ha-1) and N fertility (165–175 kg ha-1) for corn silage at 0.38- and 0.76-m row spacings in the northeastern USA. Most narrow-row corn silage producers, however, have continued to plant at high plant densities and apply high rates of animal waste.

Roth (1996) reported a 9% corn silage yield advantage at 0.38- vs. 0.76-m row spacing in Pennsylvania. In New York, Cox et al. (1998) reported only a 4% corn silage yield advantage at 0.38- vs. 0.76-m row spacing, with no row-spacing effect on in vitro true digestibility (IVTD), neutral detergent fiber (NDF), NDF digestibility, and whole-plant N concentrations. In the same study, IVTD of corn in narrow rows had a negative linear response, NDF had a positive linear response, and NDF digestibility had a negative quadratic response to plant densities. Cox and Cherney (2001) also reported that IVTD of corn in narrow rows had a positive linear response and NDF and NDF digestibility had negative linear-plus-plateau responses (plateau of {approx}110 kg ha-1) to N rates.

We evaluated first-year, second-year, and continuous corn forage at 0.38- and 0.76-m row spacings at recommended harvest plant densities and N fertility and at 0.38-m row spacing at high harvest plant densities ({approx}100000 plants ha-1) and N fertility ({approx}225 kg ha-1) on a large dairy farm in western New York. The objective of the study was to determine if narrow-row corn required high plant densities and N fertility for optimum yield and quality. To accomplish this, we evaluated (i) soil NO3–N and plant N concentrations at different times of the growing season, (ii) DM yield, (iii) forage quality, and (iv) residual soil NO3–N concentrations under the different row spacings, plant densities, and N fertility.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 
We formed a farmer–researcher partnership (Karlen et al., 1995) to conduct field-scale studies on a dairy farm with field scale narrow-row equipment and readily available dairy manure. Field-scale studies were established on first-year, second-year, and continuous corn in 1998, 1999, and 2000 on a 600-cow (Bos taurus) dairy farm at an elevation of 550 m near Warsaw, NY (42°68' N, 78° 22' W). First-year corn followed 3 yr of alfalfa (Medicago sativa L.) in the rotation each year. Different fields were selected for second-year and continuous corn in each year, except when first-year corn in 1999 became second-year corn in 2000, to avoid confounding place in the rotation with fields. The work crew on the farm performed all field operations, including applications of dairy manure, tillage practices, planting, spraying, and harvesting. The predominant soil type in the study was a Bath silt loam (coarse-loamy, mixed, mesic Typic Fragiochrepts). Soil samples were taken from the 0.2-m depth in each field in early to mid-April of each year. Soil pH, which was measured in a 1:1 soil water suspension, ranged from 6.6 to 7.0, and soil P and K tested high at all times.

Three treatments (0.76- and 0.38-m row spacings at final plant densities of about 85000 plants ha-1 and N fertility of about 165 kg ha-1 and 0.38-m row spacing at final plant densities of about 100000 plants ha-1 and N fertility of about 225 kg ha-1) were staked out in a randomized complete block design with three replications in each field in early spring of each year. Individual plot size was 12 m wide and 225 to 400 m long. Dairy manure was analyzed each year for N, P, and K content just before manure application, which occurred around mid-March in all 3 yr. Total N of the manure ranged from 3.0 to 3.2 g kg-1, with the organic N fraction in the 1.3 to 1.5 g kg-1 range and the NH4–N fraction in the 1.5 to 1.7 g kg-1 range. Liquid manure applications were then injected at rates of 36000 to 129000 L ha-1 (except for first-year corn in the recommended N fertility treatment)—depending on N content of the manure, the year of corn in the rotation, and the N treatment—to achieve N fertility status of about 165 kg ha-1 or 225 kg ha-1 (Table 1). In New York, 65% of the NH4–N fraction of spring-injected dairy manure is considered available (Cox and Klausner, 1987). Also, 35% of the organic N fraction is considered available in the first year, 12% in the second year, and 5% in the third year. In New York, a plowed-down alfalfa crop is credited with 165 kg ha-1 of available N in the first year, 56 in the second year, and 16 in the third year (Cox and Klausner, 1987). All of the fields in the study were plowed, disked, and harrowed in late April of each year.


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  		Table 1. Manure application rates, N analysis of the manure, and N credits from previous legume crops and manure applications for recommended and high N fertility in first-year, second-year, and continuous corn on a dairy farm in western New York in 1998, 1999, and 2000.

 
Pioneer Brand ‘3523’ was planted in each field in late April in 1998 and in early May in 1999 and 2000 with a John Deere (Moline, IL) 15-row (6 m wide) narrow-row planter at a rate of about 92000 kernels ha-1 for the recommended plant density and 111000 kernels ha-1 for the high plant density treatments. Two planting passes were made for each treatment. Alternate rows were shut off and the planter adjusted for plant density when planting the 0.76-m row spacing treatment. Continuous corn fields received an insecticide at planting for corn rootworm (Diabrotica sp.) control. Different pre-emergence broadcast herbicides were used, depending on the weed history in the field, for weed control. Soil samples were taken from the 0.3-m depth at 15-m intervals along the entire length of each plot just before planting. Soil samples from each plot were pooled and mixed. Subsamples were then taken and sealed in plastic bags, placed in a cooler in the field, transferred to cardboard cartons at the end of the day, and placed in a forced-air oven that was set at 55°C. After drying to constant moisture, the samples were analyzed for NO3–N colorimetrically with an autoanalyzer (Apken Corp., Klackamas, OR).

Final plant densities were estimated at about the V6 growth stage (Ritchie et al., 1993) by counting all of the plants in the fourth and fifth rows from one of the planting passes of each treatment. Final plant densities ranged from 80000 to 85000 plants ha-1 for the recommended plant density and from 100000 to 105000 plants ha-1 for the high plant density treatment. On the same day, soil samples from the 0.3-m depth were taken at 15-m intervals from between the fourth and fifth row from the same planting pass along the entire length of each plot. The samples were processed and analyzed for soil NO3–N as described previously. Whole-plant samples were taken on the same day (V6 stage) from the fifth row, and ear-leaf samples were taken at silking from the fourth row at 15-m intervals from the same pass of each treatment. Samples were dried at 60°C in a forced-air oven and then ground in a Wiley mill. Plant N concentrations were then determined by Kjeldahl procedures (AOAC, 1990).

The entire lengths of the 11 center rows (4.2 m) in the 0.38-m treatments and the center six rows (4.6 m) in the 0.76-m treatment in the nonsampled pass were harvested with a narrow-row chopper in mid- to late September when the whole-plant samples averaged about 300 g kg-1 DM. The chopper blew the silage into trucks, previously tared for weight, and the trucks were then weighed on platform scales on the farm. Immediately after harvest, we harvested single plants at 15-m intervals from an unharvested row from the harvest pass of each plot. The plants were immediately chopped in the field with a small gasoline-powered chopper, sealed in plastic bags, weighed, and dried at 60°C in a forced-air oven until constant moisture. Soil samples from the upper 0.3-m depth were taken at the same 15-m intervals and analyzed for NO3–N as described previously.

The plant samples were ground sequentially through hammer and Wiley mills. Samples were then passed through a splitter, reduced to 50 g, and further ground through a cyclone mill (Udy Corp., Fort Collins, CO) fitted with a 1-mm screen. Samples (0.5 g) were analyzed by wet chemistry for whole-plant NDF, according to procedures by Van Soest et al. (1991), and Kjeldahl N (AOAC, 1990). Samples (0.25 g) were also analyzed for IVTD according to Stage 1 of the procedure described by Marten and Barnes (1980). Samples were incubated for 48 h at 39°C in 5 mL of buffered rumen fluid containing 20 mL of the Kansas State buffer supplemented with 0.5 g L-1 urea [(NH2)2CO]. Following fermentation, residues were analyzed for NDF to determine NDF digestibility. The NDF digestibility was calculated as [(1 - NDF residue at 48 h/initial residue) x 100].

Years were considered random and sites (first-year, second-year, and continuous corn) fixed in the combined analysis of variance (ANOVA) model. A mixed model was used to analyze the data with general linear model (GLM) procedures using the SAS statistical software package (SAS Inst., 1990). The Bartlett test, however, indicated nonhomogeneous variances for all soil NO3–N and DM yield data. Consequently, only the analyses for each site within a year are presented for soil NO3–N and DM yield data. Although plant N and forage quality data had homogeneous variances, we present the analyses for each site within a year as well as the combined analyses for those data. Means among treatments for all measurements were separated by Fisher's protected LSD (P = 0.05).


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSION
 REFERENCES
 
Weather conditions differed markedly across growing seasons (Table 2). The 1998 growing season can be characterized as warm and wet, especially during the spring and early summer, with a total of 538 mm of precipitation and 1349 growing degree days (GDD) from May through September. The 1999 growing season can be characterized as warm and dry, especially during the spring and early summer, with a total of 404 mm of precipitation and 1351 GDD from May through September. The 2000 growing season can be characterized as wet and cool, especially during late spring and early summer, with a total of 623 mm of precipitation and 1168 GDD from May through September. The different weather conditions across years probably contributed to the nonhomogeneous variances for the soil NO3–N and DM yield data.


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  		Table 2. Monthly precipitation and growing degree days (GDD, 30–10°C) from May through September at Warsaw, NY, in 1998, 1999, and 2000.

 
The 0.38-m row spacing treatment at high vs. recommended plant densities and N fertility had greater soil NO3–N concentrations in the upper 0.3-m soil depth at planting and at the V6 stage in only one of nine site-year comparisons (Table 3). Soil NO3–N concentrations at the V6 stage for all treatments averaged about 50 mg kg-1 or greater, more than twice the critical concentration for optimum corn yields in New York (Klausner et al., 1993). Ma et al. (1999) reported that in eastern Canada, low mineral N losses occur from the rooting zone during the growing season in soils that receive repeated applications of dairy manure. The soils in this study have received dairy manure applications for decades, so low mineral N losses apparently occurred on these soils during the growing season, even in the wet springs of 1998 and 2000, which contributed to high soil NO3–N concentrations at the V6 stage for all treatments.


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  		Table 3. Soil NO3–N concentrations at planting, the sixth leaf stage (V6), and immediately after harvest in first-year, second-year, and continuous corn at 0.76- and 0.38-m row spacings at recommended plant densities and N fertility and at 0.38-m row spacing at high plant densities and N fertility on a dairy farm in western New York in 1998, 1999, and 2000.

 
Corn at 0.38-m row spacing and high vs. recommended plant densities and N fertility had similar whole-plant N concentrations at V6, ear-leaf N concentrations at silking, and whole-plant N concentrations at harvest in either eight or nine of nine site-year comparisons (Table 4). Whole-plant N concentrations at the V6 stage for all treatments ranged from about 37 to 46 g kg-1, well above the 35 g kg-1 critical concentration for optimum corn yield (Jones and Eck, 1973). Likewise, ear-leaf N concentrations at silking in all treatments ranged from about 25 to 28 g kg-1 in 1998 and 1999, at or above the critical concentration of 25 g kg-1 for optimum corn yields under high-yielding conditions (Dara et al., 1992). Ear-leaf N concentrations, however, ranged from about 22 to 25 g kg-1 in 2000, despite abundant soil NO3–N concentrations at the V6 stage and precipitation. Apparently, the very cool conditions in July of 2000 limited N uptake, which resulted in low ear-leaf N concentrations in all treatments.


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  		Table 4. Whole-plant N at the sixth leaf stage (V6), ear-leaf N at silking, and whole-plant N at harvest in first-year, second-year, and continuous corn at 0.76- and 0.38-m row spacing at recommended plant densities and N fertility and at 0.38-m row spacing at high plant densities and N fertility on a dairy farm in western New York in 1998, 1999, and 2000.

 
Corn at 0.38-m row spacing and high vs. recommended plant densities and N fertility had similar DM yields in eight of nine site-year comparisons (Table 5). The lack of response by corn in narrow rows to high plant densities and N fertility is consistent with a previous small-plot study in which animal manure was not the N source (Cox and Cherney, 2001). Surprisingly, corn at 0.38- vs. 0.76-m row spacing at recommended plant densities and N fertility yielded greater in only two of nine site-year comparisons, which is not consistent with previous small-plot research (Cox et al., 1998). Corn at 0.38-m row spacing and high plant densities and N rates did have greater DM yields in four of nine site-year comparisons compared with corn at 0.76-m row spacing. Nevertheless, dairy producers should not grow narrow-row corn forage at high plant densities and N rates, unless forage quality is significantly improved, because of the lack of DM yield response by narrow-row corn to high plant densities and N fertility.


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  		Table 5. Dry matter (DM) yield of first-year, second-year, and continuous corn at 0.76- and 0.38-m row spacings at recommended plant densities and N fertility and at 0.38-m row spacing at high plant densities and N fertility on a dairy farm in western New York in 1998, 1999, and 2000.

 
Corn at 0.38-m row spacing and high vs. recommended plant densities and N fertility had similar IVTD, NDF, and NDF digestibility in all site-year comparisons (data not shown). Cox and Cherney (2001) reported that IVTD concentrations of corn at 0.38-m row spacing showed a positive linear response and NDF a negative linear-plus-plateau response to increased N fertility. In contrast to N fertility, IVTD concentrations of corn at 0.38-m row spacing showed a negative linear response and NDF a positive linear response to increased plant densities (Cox et al., 1998). Apparently, the offsetting responses of IVTD and NDF to increased N fertility and plant densities resulted in similar forage quality characteristics between the 0.38-m treatments. Corn at 0.38- and 0.76-m row spacing and recommended plant densities and N fertility also had similar forage quality characteristics, which is consistent with previous research (Cox et al., 1998).

Corn at 0.38-m row spacing and high vs. recommended plant densities and N fertility had greater soil NO3–N concentrations after harvest in three of nine site-year comparisons (Table 3). As expected, the 0.76- and 0.38-m row spacings at recommended plant densities and N fertility had similar soil NO3–N concentrations after harvest in all site-year comparisons. Ma et al. (1999) reported that in eastern Canada, large amounts of mineral N are lost to the environment over the winter when high rates of dairy manure are applied. Undoubtedly, most of the residual soil NO3–N can potentially be lost to the environment in the northeastern USA because it has similar climatic conditions as eastern Canada and a preponderance of shallow soils (Magdoff, 1991). In this study, precipitation ranged from 20 to 23 cm from October through March at the experimental site on soils with a fragipan at the 0.6-m depth, so undoubtedly most of the residual soil NO3–N was lost to the environment.


   CONCLUSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
REFERENCES
 
Narrow-row corn at high vs. recommended plant densities and N fertility did not improve yield or quality in field-scale studies on a large dairy operation in western New York. Furthermore, high residual soil NO3–N concentrations were observed in narrow-row corn at high plant densities and N fertility in three of nine site-year comparisons. Consequently, we recommend that dairy producers in the northeastern USA grow narrow-row corn at recommended plant densities ({approx}85000 plants ha-1) and N fertility ({approx}165 kg N ha-1). Cox and Cherney (2001), who reported that narrow-row corn at high vs. recommended plant densities and N fertility did take up 17 more kg N ha-1, suggested that dairy producers with excess animal waste production could add slightly more N above the recommended rate to narrow-row corn. Based on DM yields and whole-plant N concentrations, narrow-row corn at high vs. recommended plant densities and N fertility took up 8 more kg N ha-1 in first-year corn, 16 more kg N ha-1 in second-year corn, and similar amounts of N in continuous corn. Consequently, we conclude that dairy producers who have excess animal waste on the farm can add 10 to 15 kg N ha -1 above the recommended rate on first- and second-year corn only.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 




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This Article
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