Author: mem40@cornell.edu

Field-Scale Row Spacing by Seeding Rate Studies in Soybeans

Bill Cox, John Orlowski, and Phil Atkins, Department of Crop & Soil Sciences, Cornell University

Soybean acreage continues to expand in New York with many first-time growers now planting the crop. Many new growers plant soybeans with a corn planter instead of a grain drill, which has been the almost exclusive planter for soybeans in NY over the last 30 years. Also, some experienced soybean growers, who no longer plant wheat, have switched to a corn planter to save on equipment costs. In addition, some growers are purchasing new row crop planters with inter-units allowing for corn planting in 30-inch rows and soybean planting in 15-inch rows. With that in mind, we conducted field-scale row spacing by seeding rate studies in 2010 and 2011 on farms in Cayuga and Livingston Counties to evaluate soybeans planted with a drill in 7.5 inch rows vs. planting with a row crop planter in 30-inch or 15-inch rows. The Cayuga County farm was a no-till site and the Livingston County farm was a chisel tillage site. The growers performed all management practices and we took numerous measurements, of which early stand counts and yield (with a Weigh Wagon) will be presented here.

Early stand establishment at Cayuga Co. averaged about 72% (107,287 plants/150,000 average seeding rate) for the drilled soybeans in 7.5 inch rows (Table 1). In contrast, early stand establishment averaged about 83% in 30-inch rows at Cayuga Co. Likewise, drilled soybean in 7.5 inch rows had much lower stand establishment at the Livingston Co. site.  Drilled soybeans in 7.5 inch rows averaged 69% early stand establishment (103,645/150,000) compared to about 81% in 30 inch rows at the chisel tillage site. Apparently, under actual grower practices, stand establishment is much better in 30-inch rows when planted with a corn planter compared with drilled beans in 7.5 inch rows.

Poorer stand establishment for drilled beans may partially explain the yield data from these field-scale studies. Previous small-plot research at the Aurora Research Farm in the mid-1990s and in the late 2000s indicated that drilled beans yielded anywhere from 7 to 15% greater than 30-inch beans planted with a corn planter. In these field-scale studies, however, row spacing did not affect soybeans at the no-till Aurora site. At the chisel tillage site, drilled beans yielded only about 4% greater than beans in 30-inch rows, if planted at 170,000 seeds/acre (Table 1). Some wheel traffic damage from post-emergence pesticide applications may also have damaged the drilled soybeans more than the 30-inch soybeans, which could have reduced any yield advantage for drilled or narrow row soybean.

Conclusion
Row spacing had much less of an impact on soybean yield than expected in these field-scale studies. At a no-till site, row spacing did not affect yield. At a chisel tillage site, drilled soybean planted at 170,000 seeds/acre yielded about 4% more than 30-inch soybean at 130,000 seeds/acre. Apparently, growers can plant soybeans in 30-inch rows without much of a yield loss, especially in years or fields where yields are in the 50-65 bushel/acre range. At sites or in years where growth is slow and yields are low, the yield advantage for drilled soybeans may be greater than reported in this study.

Planting Soybeans….Should I Buy a Grain Drill?

John Orlowski, Bill Cox, Wayne Knoblauch, and Phil Atkins, Department of Crop & Soil Sciences, Cornell University

Soybean acreage has more than doubled in NY over the last decade. In 2000, NY growers planted about 135,000 acres of soybeans, but planted about 280,000 acres in both 2010 and 2011. More importantly, total annual value of soybeans has averaged about $145 million over the last 2 years, almost 40% of the value of all commercial vegetable crops in NY, indicating that soybeans are no longer a minor crop. Increased acreage comes from a combination of long-time growers planting more acres and new growers adding soybeans to their rotation.  Some new growers are from regions in NY where wheat is not in the rotation. Consequently, these new growers, who do not own a grain drill, are seeding soybeans with a standard row crop planter (30 inch rows).  An obvious question is should these new growers purchase a grain drill or continue to seed soybeans with a corn planter in 30-inch rows?

We conducted field scale studies in 2010 and 2011 on cooperator farms in Central (Cayuga County) and Western New York (Livingston County) in order to investigate the effect of row spacing on soybean yield using actual grower management practices.  The cooperating farmers performed all field operations including tillage, planting, chemical application and harvest. We used a Weigh Wagon to record yield and also took other measurements including stand counts, weed counts, lodging, plant height, disease incidence, and moisture at harvest.  The Cayuga Co. farm was planted no-till in both years while the Livingston Co. farm was chisel plowed in both 2010 and 2011.

Economic analysis was conducted for costs associated with purchasing a grain drill appropriate for planting 300 acres (15 ft. drill-list price $20,000), 600 acres (20 ft. drill-list price $25,500) and 1200 acres (30 ft. drill-list price $46,000) of soybeans.  The results are reported in real 2012 dollars, based on the average soybean price of $11.50/ bushel and seed cost of $52/ bag (150,000 seeds) in 2010 and 2011.

Cayuga Co.
As reported in the previous article, there were no differences in yield among the three row spacing’s. Consequently the grower at this location, who practices a corn-soybean-wheat rotation, can use either a no-till grain drill or row crop planter to plant soybean into high-residue corn conditions. If the grower switches to an exclusive corn-soybean rotation, the grower can continue to use the grain drill but not purchase a new drill once it requires replacement. Instead, the grower should only maintain a row crop planter without inter-units and plant corn and soybean in 30-inch rows.

Livingston Co.
At this location we did see differences in yield.  The drilled (7.5 in) soybeans at the recommended seeding rate of 170,000 seeds/acre showed a 2.4 bushel/acre or about a 4% yield advantage compared to 30-inch rows at a seeding rate of 130,000 seeds/acre (64.1 vs. 61.7 bushels/acre).  For this farm that already owns a grain drill, the relative profit of drilling soybeans in 7.5 inch rows at the higher seeding rate compared to planting in 30 inch rows at the lower seeding rate would be a function of the market price received for the harvested soybean crop minus the seed cost associated with the higher seeding rate.  So, if the grower paid an average price of $55/bag for seed and marketed the crop at $11.50/bushel in the 2010 and 2011 growing seasons, the farmer at this site would have realized an increase in net farm profitability of about $13.30/acre by planting with a grain drill (Table 1). If seed costs increase and prices received for the crop decrease in the future, profit will shrink (Table 1).

For farms that do not own a grain drill, should they purchase one if there is a 2.4 bushel/acre yield advantage?  We considered the annual fixed costs of owning a grain drill, including depreciation, interest, shelter and insurance. Likewise, we considered the annual variable costs of ownership, including repair costs, harvest and hauling costs and the cost of the extra seed (40,000/150,000 x $52/bag =$13.87/acre) needed to drill soybeans at 170,000 seeds/acre compared with 130,000 seeds/acre when planted with a corn planter.   The breakeven point for purchasing a grain drill to seed soybeans based on prices and costs in 2010 and 2011 and a 2.4 bushel/acre yield advantage is around 300 acres.  The grower would realize an increase in net farm profitability by purchasing a grain drill if planting 600 or 1200 acres of soybeans (Table 2). As expected the more soybean acres planted, the greater the increase in net farm profitability.

Conclusion
Our economic analyses indicate, given 2010 and 2011 seed costs and market prices and a 2.4 bushel/acre yield advantage for drilled beans, growers who own a grain drill would have reaped a profit of about $13-14/acre if seeding soybeans with a grain drill. For growers who don’t own a grain drill, buying a grain drill would be profitable at 2010 and 2011 prices, if planting more than 300 acres of soybeans.  On farms with less soybean acreage or no yield advantage, buying a grain drill does not provide an economic advantage. The net farm profitability, however, will vary significantly when the yield advantage for drilled soybeans, the price of soybean seed, and the price received by the farmer for their crop vary.

Life Cycles Affect Timing of Thistle Control in Grass Pastures

Russel R. Hahn,
Department of Crop and Soil Sciences, Cornell University

Two thistles common to New York State are bull thistle (Cirsium vulgare) and Canada thistle (Cirsium arvense). Both were introduced from Eurasia and became naturalized in Canada and the United States. Although closely related and somewhat similar in appearance, theses thistles exhibit some differences in form and have very different life cycles. These life cycle differences play an important role in timing of control measures.

Bull Thistle Illustration
Figure 1. Bull Thistle. (Illustration Agriculture Handbook No. 366, “Selected Weeds of the United States”. 1970. Agriculture Research Service, USDA )

Bull Thistle
Bull thistle is a biennial weed that reproduces by seed only. All biennials require two growing seasons to complete their life cycle. In the first year, bull thistle germinates from seed and forms a rosette or basal cluster of leaves (see photo) with a large fleshy taproot. After overwintering in this stage, the plants complete their life cycle by forming a flowering stalk and setting seed during the second growing season. The stems of bull thistle may be 3 to 6 feet tall, are often branched, and are more or less hairy. The leaves are deeply cut, spiny, and run down the stem (Figure 1). Deep purple or rose flower heads are formed during the second growing season. These heads are 1 to 2 inches in diameter and are surrounded by numerous spiny tipped bracts. Bull thistle is found in pastures, meadows, and waste areas. Although it is an aggressive weed in these situations, it does not survive in tilled fields.

Bull Thistle Photo
Bull Thistle (photo R. R. Hahn)

Canada Thistle
Canada thistle is a perennial weed that reproduces by seeds and horizontal roots. These roots extend several
feet deep, some distance horizontally (Figure 2), and allow individual plants to live for more than two years. Canada thistle stems are grooved and are 2 to 5 feet tall with branching only at the top. The stems are somewhat hairy when mature. The leaves are smooth, somewhat lobed, and usually have crinkled edges and spiny margins (see photo). The flower heads are numerous, compact, and are borne in clusters. The lavender heads are ¾ inch or less in diameter. Male and female flowers are usually in separate heads and on different plants. As a result, some patches of this weed never produce seed. Canada thistle is found throughout the northern half of the United States. Like bull thistle, it can be problematic in pastures, meadows, and waste areas. In addition, its’ perennial nature allows it to thrive in cropland as well.

Canada Thistle Illustration
Figure 2. Canada Thistle (Illustration Agriculture Handbook No. 366, “Selected Weeds of the United States”. 1970. Agriculture Research Service, USDA)

Control Recommendations
Both of these thistles are somewhat sensitive to growth regulator herbicides (synthetic auxin/Group 4 herbicides) such as 2,4-D and Banvel/Clarity. These readily translocated herbicides are recommended for control or suppression of both species in grass pastures, however application rates and timing differ.

Weed Management
For bull thistle control, application of 3 pt/A of 2,4-D (3.8 lb/gal formulation) or 1 pt/A of Banvel or Clarity to the rosette stage in fall or early spring before the plants send up the flower stalk is recommended. For Canada thistle, the ideal timing would be during periods of active growth after weeds have reached the bud stage in mid- to late summer, but before killing frost. At this time, the plants have maximum leaf area to absorb herbicides and begin moving carbohydrates into the rootstocks. These stored carbohydrates allow the plants to survive winter and emerge again in the spring. Herbicide movement into these rootstocks is facilitated by this process. Application of 4 pt/A of 2,4-D (3.8 lb/gal formulation) or of 2 pt/A of Banvel or Clarity are recommended for Canada thistle suppression in grass pastures. Repeated applications of these herbicides would likely be needed to bring this tough weed under control.

Canada Thistle
Canada Thistle (photo R. R. Hahn)

Grazing Restrictions
With both 2,4-D and Banvel/Clarity, label instructions specify grazing and harvesting restrictions for pasture situations. Lactating dairy animals should not graze 2,4-D treated areas for 7 days following application and meat animals must be removed from 2,4-D treated areas for 3 days before slaughter if less than 14 days have elapsed since treatment. Lactating dairy animals should not graze for 7 days after treatment with up to 1 pt/A, and for 21 days after 2 pt/A of Banvel or Clarity. Meat animals should be removed from areas treated with Banvel or Clarity 30 days before slaughter. Applications made at the end of the grazing season in late summer or early fall can minimize concerns about these grazing restrictions.

Field Crops in NYS Now Have an Annual Value of about a Billion Dollars

Bill Cox, Department of Crop and Soil Sciences, Cornell University

The value of field crops has increased greatly in New York over the last 5 years led by the dramatic increase in the value of grain corn (Fig. 1). The acreage of grain corn has increased significantly, averaging about 600,000 acres from 2007-2011 compared with about 470,000 acres from 2002-2006 (NYS Ag Statistics, 2011). In addition, corn yields have averaged about 138 bushels/acre from 2007-2011 compared with about 119 bushels/acre from 2002-2006. Consequently, the value of corn for grain has averaged about $400 million from 2007-2011, slightly higher than the $385 million value of vegetable production (fresh market and processing together) in New York during the same period (NYS Ag Statistics, 2011).WCUVol22No1_article1_fig1

Additionally, the value of corn silage production averaged about $300 million from 2007-2011, slightly less than the $330 million value of fruit production during the same period (NYS Ag Statistics, 2011). Therefore, because of the dramatic increase in the value of both the grain corn and silage crops, the corn crop had an average value similar to the fruit and vegetable crop values combined from 2007-2011.

The value of soybean has also increased over the last 5 years although at a much lower value than corn (Fig.1). The acreage of soybean has increased significantly, averaging about 245,000 acres from 2007-2011 compared with 170,000 acres from 2002-2006 (NYS Ag Statistics, 2011). As with corn, the average soybean yield also increased, averaging 44 bushels/acre from 2007-2011 compared with 39 bushels/acre from 2002-2006 (NYS Ag Statistics, 2011). Consequently, the value of soybeans averaged about $120 million from 2007-2011 compared with $40 million from 2002-2006 (Fig.1).

In contrast to corn and soybean, wheat acreage has stayed relatively constant, averaging about 115,000 acres from 2007-2011, similar to acreage from 2002-2006 (NYS Ag Statistics, 2011). The average yield, however, increased to 61 bushels/acre from 2007-2011 compared with 56 bushels/acre from 2002-2006. Consequently, the wheat crop had an average value of $35 million from 2007-2011 compared with about $18 million from 2002-2006 (Fig.1). Although the value of wheat straw cannot be quantified, it likely adds an additional $15 million in value to the crop.

Likewise, it is difficult to place a value on the total forage production in New York State, which has averaged about 1.9 million acres from 2007-2011 (NYS Ag Statistics, 2011). The value of total hay (1.35 million acres from 2007-2011) averaged about $300 million from 2007-2011 compared with about $345 million from 2002-2006, one of the few field crops that has declined in value over the last 5 years (NYS Ag Statistics, 2011).

Conclusion
The value of total field crop production has increased dramatically over the last 5 years, averaging about $1 billion in 2010 and 2011, about 40% of the value of milk production in New York State (NYS Ag Statistics, 2011). Although field crops have traditionally occupied more than 90% of the crop acreage in New York, field crops have been generally seen as solely providing support to the dairy industry. The dramatic increase in the value of corn, soybean, and wheat over the last 5 years, however, should change the traditional perception of New York field crops. For example, New York traditionally has been a feed grain (corn, soybean, oats, and barley) deficit State feeding about 2 million tons annually but producing only about 1.85 million tons annually from 2002-2006 (NYS Ag Statistics, 2011). Subsequently, feed grain from the Midwest or Canada has traditionally been shipped in to support the feed demand of dairy industry. In contrast, recent feed grain production in New York averaged about 2.7 million tons annually, whereas about 1.9 million tons have been fed annually in New York from 2007-2011. New York is now a feed surplus State and field crops are now marketed to other buyers as well as to the dairy industry.

If this trend continues, NY field crops should be viewed not as an industry that solely supports the dairy industry but rather as a stand-alone industry that provides support to the dairy industry.

Impact of Clover Incorporation on Ammonium, Nitrate, and ISNT-N over Time; 4-Year Summary

Quirine Ketterings1, Greg Godwin1, Charles L. Mohler2, Brian Caldwell3, Karl Czymmek1
1Department of Animal Science, and 2Department of Crop and Soil Sciences, Cornell University, 3Department of Horticulture, Cornell University

Red clover undersown into a small grain crop is commonly used as an N source for corn in organic grain production systems. How much N should be credited to the clover green manure is unclear. In this study we addressed the following issues: (1) ammonium and nitrate dynamics over time following clover plowdown; (2) release peak for nitrate related to the above ground biomass in the clover; and (3) clover plowdown influence on the results of the Illinois Soil Nitrogen Test (ISNT), a predictor of soil N supply potential. Results from earlier years were reported in Godwin et al (2009) and Ketterings et al (2011). Here we report the 4-year summary.

Methods
We monitored ISNT-N, ammonium-N and nitrate-N levels on a weekly basis in corn crops in one management system within the Cornell Organic Grain Cropping Systems Experiment at the Musgrave Research Farm near Aurora, New York. Beginning in 2005, this experiment has compared five management systems with differing fertility and tillage regimens and two entry points into a soybean-spelt/red clover-corn rotation (http://www.organic.cornell.edu/ocs/grain/index.html). For the project discussed here we sampled the Low Input Organic System (System 2) during years when corn was grown following plowdown of a 1-yr old clover cover crop.

Actual fertility amendments and their date of application are shown in Table 1. Plots were randomly split into two rotation entry points, so that one half of each plot was a year behind in the crop rotation sequence. The plots that were sampled for N dynamics were part of Entry Point A in 2007 and 2010 and Entry Point B in 2008 and 2011.

Prior to plowing, we collected samples of above-ground clover biomass. Below-ground biomass was also sampled in 2011. The initial soil sampling round (0-8 inch depth; 12 cores per 120’ x 40’ plot) occurred prior to plowdown of the clover. The next sampling round occurred at plowdown and was followed by eight sampling rounds at weekly intervals thereafter (seven in 2011). Corn was planted in late May or early June (Table 2). On New York organic grain farms corn is generally planted in late May with the goal of planting into warm soils to achieve optimal germination without the need for seed protectants, and to allow for sufficient clover growth to support the N needs of the corn crop.

Soil samples were analyzed for ISNT-N in the Cornell Nutrient Management Spear Program (NMSP) laboratory using the enclosed griddle modification of Klapwyk and Ketterings (2005). Soil samples were also analyzed for 2 N KCl extraction of exchangeable nitrate+nitrite and ammonium as described in Mulvaney (1996). The weather patterns showed two extreme rainfall events during the sampling periods: a 2 inch plus rainfall event in week 4 after planting in 2010 and another in week 5 in 2011 (Table 3).

Results and Discussion
Clover above-ground dry biomass was 1.6, 2.4, 1.5 and 1.7 ton/acre in 2007, 2008, 2010 and 2011, respectively. In 2011 the below ground cover crop biomass was 0.6 ton/acre, about 25% of the total (above and below ground) biomass of the clover cover just prior to plowdown. The year 2007 was a drought year with low corn yield (87 bu/acre), whereas 2008 and 2010 were excellent growing years (165 bu/acre in 2008 and 160 bu/acre in 2010). Despite challenging growing condition (wet spring and fall, dry mid-summer) yield averaged 150 bu/acre in 2011.

Soil nitrate-N levels increased following clover incorporation (Figure 1). The height of the nitrate-N peak following plow-down was consistent with clover biomass over the four years: just over 60 ppm in 2007, almost 90 ppm in 2008, and about 30 ppm in 2010 and 2011 (Figure 1). Peaks in nitrate-N were measured in week 3 in 2011 and 5 or 6 in all other years. The timing of nitrate-N release from clover was well-aligned with the period of highest corn N needs in 2007 and 2008. In 2010 and 2011, the heavy rainfall in week 4 (2010) and week 5 (2011) may have leached nitrate-N. Nitrate leaching may be the cause of the relatively low nitrate release peaks in 2010 and 2011.

Soil samples were analyzed for ISNT-N as an indicator of soil N supply potential through mineralization of organic matter. Previous work has shown that the test is accurate as a predictor of soil N supply potential for corn but that soil samples should not be taken within 5 weeks after manure addition or sod turnover; these amendments create a temporary increase in ammonium-N and hence also in ISNT-N. The question remained whether incorporation of a cover crop would result in a similar restriction in timing of sampling for ISNT-N. The results of the four years of testing showed that clover incorporation did not result in an accumulation of ammonium-N and hence it is also not surprising that the ISNT-N levels remained stable over time (coefficients of variation across sampling dates were only 4.3, 2.2, 3.9, and 2.6% for 2007, 2008, 2010, and 2011, respectively). These results suggest that for the clover-based system, timing of ISNT sampling is not restricted (i.e. sampling can occur before or after clover incorporation). The comparisons of ISNT-N in 2007 and 2010 (entry point A) and 2008 and 2011 (entry point B) suggest a slow decline in ISNT-N over time under current management and yield levels (Figure 2) but additional research (more data points in time) is needed to evaluate trends.

Averaged across plots, the pre-sidedress nitrate test (PSNT) results were 20, 29, 16, and 17 ppm where clover had been plowed down in 2007, 2008, 2010, and 2011, respectively. There was a strong correlation between clover above-ground N pool prior to plow down and PSNT in this study (PSNT (ppm) = 4.9 + 0.14 * Npool (lb N/acre); R2 = 0.94). Additional data points are needed before conclusions can be drawn about the use of above ground N pool as a predictor of PSNT-N and the impact of weather on the predictions.

The weekly sampling and the PSNT results of the clover systems suggest that the clover supplied a considerable amount of N. Application of 1900 lb/acre of 4-5-2 poultry manure compost in addition to the plowed down clover in the same experiment showed no yield increase in 2007-2010 (Caldwell et al., 2011) or 2011 (data not yet published), suggesting that in each of the four years, the nitrate-N released from clover decomposition was sufficient to meet the needs of the corn, despite the <21 ppm PSNTs in 2007, 2010, and 2011.

Summary and Conclusions
Clover incorporation greatly increased the amount of available N for the following corn crop. Decomposition of the clover resulted in nitrate peaks 5-6 weeks after incorporation, well-aligned with N needs of the corn and showing that clover plowdown is an excellent choice for providing N to corn in organic and conventional production systems. Clover decomposition did not result in ammonium-N accumulation. This study needs to be duplicated at other locations but results to date indicate that a clover cover crop can supply sufficient N. although actual N supply will vary depending on the biomass produced and mineralization conditions. The study also showed that ISNT sampling for assessment of soil N supply is not restricted in time where clover is a main source of N fertility.

References

  1. Caldwell, B, C.L. Mohler, Q.M. Ketterings and A. DiTommaso (2011). Yield and profitability during and after transition in the Cornell organic grain cropping systems experiment. What’s Cropping Up? 21(2): 7-11.
  2. Godwin, G., Q.M. Ketterings. C.L. Mohler, B. Caldwell, and K.J. Czymmek (2009). Impact of clover incorporation and ammonium nitrate sidedressing on ammonium, nitrate, and Illinois Soil Nitrogen Test dynamics over time. What’s Cropping Up? 19(3): 12-15.
  3. Ketterings, Q.M., G. Godwin, C.L. Mohler, B. Caldwell, and K.J. Czymmek (2011). Impact of clover incorporation and ammonium nitrate sidedressing on Illinois Soil Nitrogen Test dynamics over time 3-year summary What’s Cropping Up? 21(2): 1-4.
  4. Klapwyk, J.H., and Q.M. Ketterings (2005). Reducing laboratory variability of the Illinois soil N test with enclosed griddles. Soil Sci. Soc Am. J. 69: 1129-1134.
  5. Mulvaney, R.L. (1996). Nitrogen-Inorganic Forms. In Methods of soil analysis. Part-3- Chemical Methods. SSSA, Inc., ASA, Inc. Madison, WI. P. 1123-1184.

CNMSPAcknowledgments
This work was supported by the USDA Organic Research and Extension Initiative, the New York Farm Viability Institute, and funds from the Cornell Experiment Station. We thank Kreher’s Poultry Farms for donating compost. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

Recommended Seeding and Side-Dress N rates Provide Close to Optimum Grain Corn Yields in 2010 and 2011

Bill Cox and Phil Atkins, Department of Crop and Soil Sciences, Cornell University

When soil conditions are conducive to a 90% plant establishment rate, we currently recommend seeding rates of 30,000 kernels/acre for grain corn on silt loam soils in New York, based on small-plot studies at the Aurora Research Farm from 2003 to 2005 and field-scale studies from 2006 through 2010 (What’s Cropping Up?, Vol. 21, No.1, p.4-5).The results from the studies in the 2000s are similar to a 1991-1993 study in which nine hybrids (released in the late 1980s or early 1990s) also had optimum yield at 30,000 kernels/acre (What’s Cropping Up?, Vol. 4, No.2, p.3). Recent hybrid releases, however, have been selected at higher plant populations and lodge less because of the Bt corn borer trait. Consequently, there is a general belief that recent hybrid releases require higher seeding rates than hybrid releases from the late 1980s and early 1990s. In addition, new hybrid releases may respond more positively to N fertilization so there is also a general belief that new hybrid releases planted at high rates with high N fertilization will “really kick it out”. Most of our studies in the 2000s were conducted at recommended side-dress N rates so perhaps that is the reason why our results do not validate the general belief that high seeding rates (~35,000 kernels/acre of higher) are required for optimum yield in NY. On the other hand, most corn seed is now treated with soil-applied insecticide/fungicide, which results in greater stand establishment today. Consequently, the higher plant establishment rate may offset the need to plant new hybrid releases at higher seeding rates. We completed a 2-year hybrid by seeding rate by side-dress N rate study (small-plot) in 2011 to determine if new hybrid releases respond more positively to higher seeding rates at higher side-dress N rates.

We evaluated two hybrids with the Bt corn borer trait (DKC51-86 and P0125XR) at four seeding rates (25,000 to 40,000 kernels/acre) and two side-dress N rates (the recommended side-dress N rate of 100 lbs/acre for corn following soybeans and a high side-dress N rate of 150 lbs/acre) in small plot research at the Aurora Research Farm in 2010 and 2011. About 25 lbs of N/acre were also applied in the starter so a total of 125 and 175 lbs of N/acre was applied in this study. The planting date was 30 April in 2010 and 10 May 2011 and corn was side-dressed with the two N rates at the 4th leaf stage (V4).

Plant establishment rate averaged 87% for the DEKALB hybrid and 79% for the Pioneer hybrid in 2010 and about 90% for both hybrids in 2011. When averaged across years, hybrids did not influence yield so results have been averaged across hybrids. The quadratic regression equation predicted maximum yield at about 35,000 kernels/acre in 2010, a year with record yields in NY and at the experimental site (Fig.1). The quadratic equation, however, typically overestimates maximum values as evidenced by only a 1.5% yield difference between the 30,000 kernel/acre (295 bushels/acre) and the 35,000 kernel/acre seeding rate (299 bushels/acre). In 2011, a year with very dry June and July conditions, regression analyses indicated no response to seeding rate (Fig.1).When averaged across years and hybrids (Fig.1), yields were virtually the same at seeding rates of 30,0000 (239 bushels/acre), 35,000 (239 bushels/acre), and 40,000 kernels/acre (240 bushels/acre).

Of equal importance, there was no difference in yield between N rates (Fig. 1). Also, there was no difference between hybrid by seeding rate by side-dress N rate interaction in either year of the study or when averaged across years (Fig.1). This indicates that optimum yields were achieved for both hybrids in both years at the 30,000 kernel/acre seeding rate at the recommended side-dress N rate when corn follows soybeans. No further yield increase was observed at the higher seeding rates in the presence of higher N rates.

Conclusion
Once again, the recommended seeding rate of 30,000 kernels/acre resulted in close to optimum yield in a year with the highest yield on record (2010) and in a year with the second driest July on record (2011) in the presence of recommended or elevated N rates when corn follows soybeans. Nevertheless, almost all grain growers plant at higher seeding rates so we question whether this seeding rate response is consistent across different soil types and farming operations in NY. Consequently, Geoff Reeves, an MS student with our program at Cornell, initiated field-scale studies in 2011 on four farms evaluating two hybrids at four seeding rates (25,000 to 40,000 kernels/acre) in the major corn grain regions of NY. We have two studies in western NY (twin-row corn in Orleans County and 30-inch rows in Livingston County) and two studies in central NY (20-inch rows in Cayuga County and 30-inch rows in Seneca County). We evaluated stand establishment, lodging, yield, moisture, and test weights in 2011. We will collect the same data again in 2012 and Geoff will conduct a partial budget analyses to determine optimum economical seeding rates for grain corn across different soil types and farming operations in NY.