Integrating Cropping Practices to Improve Nutrient Management Plans and Ensure Environmental and Economic Sustainability in Dairy Farming Systems

Final report for OS17-103

Project Type: On-Farm Research
Funds awarded in 2017: $15,000.00
Projected End Date: 03/14/2019
Grant Recipient: Virginia Tech
Region: Southern
State: Virginia
Principal Investigator:
Gonzalo Ferreira
Virginia Tech
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Project Information

Abstract:

To reduce nutrient loading in waterbodies, farms are encouraged or mandated to develop nutrient management plans. Reducing the potential of nutrient runoff to surface water can keep nutrients above ground. We hypothesized that increasing corn planting density can be used strategically to increase N and P recycling through the soil-crop system. Therefore, the objective of this study was to evaluate the effects of corn planting density with different fertilizer rates on forage biomass yield, silage quality and digestibility, and N and P removal from the soil in a commercial dairy farm. This on-farm study was performed at a 425-cow commercial dairy farm located in Crockett, VA. During the springs of 2017 and 2018, a conventional (CONV) corn hybrid and a brown midrib (BMR) corn hybrid were planted at a theoretical seeding rate (i.e., treatments) of 60,000, 75,000, and 90,000 seeds/ha (60K, 75K, and 90K, respectively). Four plots (2.3-m wide and 25-m long) were planted for each treatment and hybrid, therefore leading to 24 plots for each field in each growing season. Also, when the crop showed 6 visible leaves (V6), all plots were split into half plots (hereafter known as subplot), and each subplot was fertilized with either 50 or 100 kg N/ha as UAN (1N and 2N, respectively). At harvesting, 10 plants were cut by hand at 15 cm above ground. Whole plants were weighed and chopped for chemical and digestibility analyses. The experiment was designed as a split-plot in a completely randomized design. All variables were analyzed using the MIXED procedure of SAS, and the statistical model included the fixed effect of year (degrees of freedom, df = 1), the fixed effect of field (df = 1), the fixed effect of treatment or planting density (fixed; df = 2), the fixed effect of corn hybrid (fixed; df = 1), the random whole-plot error (df = 72), the fixed effect of fertilization (df = 1), all 2-, 3-, 4- and 5-way interactions (df = 41), and the random split-plot or residual error (df = 72). Resulting populations were 63,200, 72,600, and 86,300 plants/ha for 60K, 75K, and 90K, respectively. Planting corn at the highest population (90K) resulted in the greatest biomass yield (21.4 Mg/ha), whereas biomass yield was similar for the intermediate (75K) and the lowest (60K) corn planting population (20.3 Mg/ha). Doubling the dosage of N fertilizer increased biomass yield only by 3.1%, and the conventional hybrid yielded 19.2% more than the BMR hybrid (22.5 vs. 18.9 Mg/ha, respectively). Planting corn at the highest population (90K) resulted in the lowest concentration of crude protein (81 g/kg), whereas the concentration of crude protein was similar for the intermediate and the lowest corn planting population (84 g/kg). Due to the negligible differences in biomass yield and crude protein concentration, the removal of N from the soil did not change by increasing corn planting population (276, 271, and 269 kg/ha for 60K, 75K, and 90K, respectively). Doubling fertilization increased N removal by 21 kg/ha. Planting corn at the lowest population (60K) resulted in the greatest concentration of P (266 mg/kg), whereas the concentration of P was similar for the intermediate and the highest maize planting population (257 and 255 mg/kg, respectively). Contrary to our hypothesis, the removal of P from the soil did not change by increasing corn planting population (55, 53, and 56 kg/ha for 60K, 75K, and 90K, respectively). Neither corn planting population nor N fertilization affected the in vitro dry matter digestibility or the in vitro neutral detergent fiber digestibility of corn silages. In conclusion, under the conditions of this on-farm study, increasing corn planting density did not increase the removal of neither N nor P from the soil.

Project Objectives:

Increasing corn planting population can substantially increase corn silage yields. Cusicanqui and Lauer (1999) reported that the greatest dry matter yields were obtained when corn plant population was increased to 98,000 plants/ha. Similarly, Ferreira et al. (2014) reported that forage yields increased linearly and by 41% when plant population was increased from 60,000 to 90,000 plants/ha. In a more recent study, Ferreira and Teets (2016) also reported higher forage yields when corn planting population was increased from 55,000 to 100,000 plants/ha. An interesting observation from the latter studies was the similar nutrient composition of the forages obtained when corn was planted at different planting populations (Ferreira et al., 2014; Ferreira and Teets, 2016).

Increasing forage yields while maintaining nutritional quality of the forage has major environmental implications, as there is an increased retention of nutrients above ground when increasing planting population (Ferreira and Teets, 2016). To reduce nitrogen (N) and phosphorus (P) loading in waterbodies, dairy farmers or managers are encouraged or mandated to develop nutrient management plans (Bosch et al., 2006; DCR, 2014). For dairy farming systems, there are three types of practices for reducing nutrient upload in waterbodies: 1) reducing nutrient excretion in manure, 2) reducing the amount and changing the method and/or timing of fertilizer application to reduce nutrient runoff, and 3) reducing the potential of nutrient runoff to surface water (Dou et al., 2001; Bosch et al., 2006). The use of stream buffers, conservation tillage, and cover crops are common means of reducing nutrient runoff. The purpose of these practices is to increase the utilization of nutrients, keeping them above ground, and therefore reducing the potential runoff.

As more biomass was harvested without affecting the N concentration of the biomass, the increased yield of corn for silage translated into a greater uptake of N from the soil (Ferreira and Teets, 2016). As N is one of the two nutrients for which dairy farmers need to prepare nutrient management plans, increasing corn planting population can have great relevance enhancing environmental quality of farm operations. In addition to suggesting a greater nutrient efficiency use, this outcome indicates that the potential of N runoff to surface water can be reduced by increasing planting population of corn for silage (Bosch et al., 2006).

For this study, we hypothesized that increasing corn planting population can be used strategically to increase N and P recycling through the soil-crop system (Powell et al., 2008), while increasing forage production and maintaining forage quality in dairy farming systems (Ferreira and Teets, 2016). Therefore, the objective of this study was to evaluate the effects of corn planting population with different fertilizer rates on forage biomass yield, silage quality and digestibility, and N and P removal from the soil in a commercial dairy farm.

 

Cooperators

Click linked name(s) to expand
  • Chrissy Teets (Researcher)
  • John B. Huffard

Research

Materials and methods:

1. Location, Fields, and Cultural Management

This on-farm study was performed at a 425-cow commercial dairy farm located in Crockett, VA. The study was performed in two fields. Field 1 (Dairy) is adjacent to the dairy facilities, whereas field 2 (Remote) is 1.3 km away from the dairy facilities. The distance from fields to the dairy facilities has affected the application rates of manure over the years; therefore, the fertility was quite different between fields leading to two diverse growing environments.

During the springs of 2017 and 2018, a conventional (CONV) corn hybrid (TMF17L86, Mycogen Seeds, Indianapolis, IN) and a brown midrib (BMR) corn hybrid (F2F817, Mycogen Seeds) were planted at a theoretical seeding rate (i.e., treatments) of 60,000, 75,000, and 90,000 seeds/ha (60K75K, and 90K, respectively). Four plots (2.3-m wide and 25-m long) were planted for each treatment and hybrid, therefore, leading to 24 plots for each field in each growing season. Within each field, replicates were randomly assigned for each of the three seeding rates. Corn was planted with a 6-row John Deere 1750 no-till planter (Deere & Company, Moline, IL) equipped with a pneumatic dosing machine and with rows separated by 76 cm. Each of the two corn hybrids was placed in three of the six seed hoppers of the planter. In 2017, the preceding crops for fields 1 and 2 were rye for silage and corn for grain, respectively. In 2018, the preceding crop for both fields was rye for silage. Weed and pest control was performed according to on-farm operating procedures.

Fields were also fertilized according to on-farm operating procedures. In both years, 50,000 L/ha of dairy manure slurry (0.4% N) was spread on both fields 10 days before planting, and 55 kg N/ha as urea ammonium nitrate (UAN) was injected in the soil during planting. When the crop showed 6 visible leaves (V6), all plots were split into half plots (hereafter known as subplot), and each subplot was fertilized with either 50 or 100 kg N/ha as UAN (1N and 2N, respectively).

2. Soil Sampling and Analyses

Soil samples were collected at planting and harvesting. At planting, 20 core subsamples (0 to 20 cm) were collected in a random pattern throughout each field and composited providing 1 sample per field each year. At harvesting, due to the extreme hardness of the soil, 5 subsamples were collected from each subplot of the 60K and 90K treatments. For the latter, soil subsamples (0 to 10 cm) were collected from the center rows’ interspace using a drill with a 25.4-mm auger bit (Robert Bosch, LLC; Farmington Hills, MI).  

At arrival to the laboratory, soil samples were spread onto metallic trays and allowed to air-dry at room temperature (25°C). Once dried, crumbs’ size was reduced by crushing the soil with a mortar and pestle and sieving through a 2-mm sieve (Hogentogler & Co., Inc; Columbia, MD). The P concentration in soil was determined after extraction in Mehlich 1 solution (0.05 N HCl + 0.025 N H2SO4) as described by Maguire and Heckendorn (2011) with modifications. Briefly, 5 g of soil was placed in 50-mL capped glass tubes and 20 mL of Mehlich solution was added. After shaking for 5 minutes at a rate of 120 oscillations per minute (Eberbach 6000; St. Belleville, MI) the solution was filtered through filter paper (Whatman No. 2). The extract solution was then submitted to the Virginia Tech Soil Testing Laboratory (Blacksburg, VA) for analysis using inductively coupled plasma atomic emission spectrometry. The nitrate concentration in soil was determined after extraction in 2 M KCl solution as described by Knepel (2003).

3. Harvesting and Ensiling

Harvesting time was mainly decided by the owners of the dairy farm and occurred at early-dent stage in 2017 and at ¼ milk-line stage in 2018. For harvesting, 5 consecutive plants from the 2 center rows and at 2 randomly selected spots within each subplot (i.e., 10 plants per subplot) were cut by hand at 15 cm above ground. Whole plants were weighed and chopped with a Stanley CH2 wood chipper (GXi Outdoor Power, LLC, Clayton, NC). After mixing thoroughly, a first subsample of chopped material was collected, immediately frozen in dry ice, and stored at -20°C until analysis. A second 400- to 500-g subsample of chopped material was collected and ensiled into MR-1014 polyethylene embossed pouches (Doug Care, Springfield, CA) and double-sealed anaerobically with a FastVac vacuum sealer (Doug Care) as described by Der Bedrosian et al. (2012). No inoculants were added to enhance fermentation. Mini-silos were stored inside plastic tubs for 90 days.

4. Forage Processing and Analyses

The first subsample of fresh material was thawed and dried at 55°C in a forced-air drying oven (Freas 645, Thermo Electron Corporation, Marietta, OH) until constant weight was reached. The resulting DM concentration was used to calculate DM yield. The dried material was then ground to pass through a 1-mm screen of a Wiley cutter mill (Thomas Scientific, Swedesboro, NJ), and the concentration of P was determined (method 965.17; AOAC International, 2019).

After 90 days of fermentation, the mini-silos were opened, and the pH was determined by blending (Waring, Torrington, CT) 10 g of corn silage with 90 mL of deionized water for 5 min and immediately measuring pH with an Accumet AB 150 pH-meter (Fisher Scientific Company, Suwanee, GA). The remaining corn silage was then dried at 55°C in a forced-air drying oven until constant weight was reached and ground to pass through a 1-mm screen of a Wiley cutter mill. Ash concentration was determined after burning samples in a furnace (Thermolyne 30400, Barnstead International Dubuque, IA) for 2 h at 600°C (method 942.05; AOAC International, 2019). Crude protein concentration was calculated as percent N x 6.25 after combustion analysis (method 990.03; AOAC International, 2019) using a Vario El Cube CN analyzer (Elementar Americas, Inc., Mount Laurel, NJ). Neutral detergent fiber and ADF concentrations were determined using the Ankom200Fiber Analyzer (Ankom Technology, Macedon, NY). Sodium sulfite and α-amylase (Ankom Technology) were used for NDF analysis (Ferreira and Mertens, 2007). Acid detergent fiber and lignin concentrations were determined sequentially. After determining ADF weights, residues were incubated for 3 h in 72% sulfuric acid within a 4-L jar that was placed in a DaisyIIIncubator (Ankom Technology). Starch concentration was determined using the acetate buffer method of Hall (2009) with α-amylase from Bacillus licheniformis(FAA, Ankom Technology) and amyloglucosidase from Aspergillus niger(E-AMGDF, Megazyme International, Wicklow, Ireland). Sugars concentration was determined as total ethanol/water-soluble carbohydrates as described by Hall et al. (1999).

5. Dry Matter and Neutral Detergent Fiber Digestibility

The Institutional Animal Care and Use Committee of Virginia Tech approved all procedures involving dairy cows for collecting rumen contents (Protocol DASC 15-234). The 30-h in vitro apparent DM digestibility (IVDMD), in vitro true DM digestibility (IVTDMD), and in vitro NDF digestibility (IVNDFD) were determined using a DaisyIIrotating jar in vitro incubator (Ankom Technology) following the procedures described by Ferreira and Mertens (2005). A composited inoculum was prepared with rumen fluid and rumen solids collected from 3 rumen-cannulated lactating cows (2 Holstein and 1 Jerseys) that were fed a diet containing (DM basis) 37.6% corn silage, 5.4% pearl millet silage, 3.8% alfalfa hay, and 53.2% concentrate mix. The concentrate mix contained corn grain, soybean meal, brewers’ grains with solubles, soy hulls, and a mineral plus vitamin mix.

6. Biomass Yield, Kernel Development, and Stem Width

Standing plants were counted when the crop showed 2 visible leaves (V2). For this, the number of plants within a 13.2-m row was counted in 2 adjacent rows. This procedure was performed in each of the 48 subplots from each of the fields. The single plant biomass (DM basis) multiplied by the number of standing plants were used to determine DM yield.

At harvesting time, kernel lines per ear and kernels per line within an ear were counted for two randomly selected plants within a representative area for each of the 48 subplots from each field. To determine the number of lines per ear, lines were counted at the mid portion of the ear (Rossini et al., 2012). To determine the number of kernels per line, kernels were counted in two opposite kernel lines within the ear. At harvesting time, also, stem width was measured for two randomly selected plants within a representative area for each of the 48 subplots from each field. Stem width was measured placing a digital caliper below the node of the ear-bearing phytomer.

7. Statistical Analysis

The experiment was designed as a split-plot in a completely randomized design. All variables were analyzed using the MIXED procedure of SAS (SAS version 9.3, SAS Institute Inc., Cary, NC). The statistical model included the fixed effect of year (degrees of freedom, df = 1), the fixed effect of field (df = 1), the fixed effect of treatment or planting density (fixed; df = 2), the fixed effect of corn hybrid (fixed; df = 1), the random whole-plot error (df = 72), the fixed effect of fertilization (df = 1), all 2-, 3-, 4- and 5-way interactions (df = 41), and the random split-plot or residual error (df = 72). The 5% least significant difference (LSD) between treatment means was calculated as the product of the standard error of the difference by the value for a probability of 0.05 with 72 df (Snedecor and Cochran, 1989).

Research results and discussion:

1. Biomass Yield

Resulting populations were 63,200, 72,600, and 86,300 plants/ha for 60K, 75K, and 90K, respectively. Planting maize at the highest population (90K) resulted in the greatest biomass yield (21.4 Mg/ha), whereas biomass yield was similar for the intermediate (75K) and the lowest (60K) maize planting population (20.3 Mg/ha; Table 1). Different than in previous studies (Ferreira et al. 2014; Ferreira and Teets, 2016), where high planting population increased DM yields substantially, in this study the increase in biomass yield at the highest planting population was only 5.4%.  Given that plant weight was inversely related to planting population (Table 1), the greatest yield for 90K was attributed mainly to the larger number of plants rather than to plant biomass. The larger number of plants for 75K was not sufficient to compensate the substantially greater weight observed for plants for 60K (281 and 323 g/plant, respectively; Table 1).

Doubling the dosage of N fertilizer increased biomass yield only by 3.1% (Table 1). The minor increase in biomass yield is likely related to a greater plant weight attributed to the larger number of kernels in the plant and a bigger stover fraction (Table 1).    

The conventional hybrid yielded 19.2% more than the BMR hybrid (22.5 vs. 18.9 Mg/ha, respectively). The greater biomass yield for the conventional hybrid is attributed to a greater plant weight related to the larger number of kernels in the plant and the bigger stover fraction (Table 1).

Table 1. Biomass yield, dry matter (DM) concentration, kernel counts, and stem with of corn for silage as affected by year, field, hybrid, planting population, and fertilization.

 

Biomass,

Mg DM/ha

DM,

g/kg

Plant Weight,

g DM/plant

Kernels,

1/plant

Stem Width,

mm

Year

 

 

 

 

 

   2017

18.7b

291b

253b

452b

16.2b

   2018

22.6a

297a

317a

497a

18.7a

   LSD1

0.7

4

9

19

0.5

Field

 

 

 

 

 

   Dairy

21.6a

294

302a

493a

18.0a

   Remote

19.8b

295

268b

456b

16.9b

   LSD

0.7

4

9

19

0.5

Hybrid

 

 

 

 

 

   CONV

22.5a

307a

313a

540a

18.1a

   BMR

18.9b

282b

257b

411b

16.7b

   LSD

0.7

4

9

19

0.5

Population

 

 

 

 

 

   60K

20.3b

295

323a

502a

18.6a

   75K

20.3b

295

281b

460b

17.2b

   90K

21.4a

293

249c

461b

16.5b

   LSD

0.9

5

11

23

0.7

Fertilization

 

 

 

 

 

   1N

20.4b

294

281

465b

17.0b

   2N

21.1a

295

288

483a

17.9a

   LSD

0.6

4

9

17

0.5

1 Least significant difference.

a,b Means with different superscripts differ (P < 0.05).

2. Silage Quality and Nutrient Removal

Planting density affected the concentrations of crude protein, neutral detergent fiber, acid detergent fiber, lignin, and P (Table 2), although the magnitudes of these changes were of minor nutritional or productive implications. Contrary to this, planting density did not affect the concentrations of ash, starch, and sugars (Table 2). Planting maize at the highest population (90K) resulted in the lowest concentration of crude protein (81 g/kg), whereas the concentration of crude protein was similar for the intermediate and the lowest maize planting population (84 g/kg; Table 2). Due to the negligible differences in biomass yield and crude protein concentration, the removal of N from the soil did not change by increasing corn planting population (276, 271, and 269 kg/ha for 60K, 75K, and 90K, respectively; P > 0.41). Doubling fertilization increased N removal by 21 kg/ha, which translates into an extraction efficiency of 42.2% for the incremental applied N.

Planting maize at the lowest population (60K) resulted in the greatest concentration of P (266 mg/kg), whereas the concentration of P was similar for the intermediate and the highest maize planting population (257 and 255 mg/kg, respectively; Table 2). Contrary to our hypothesis, the removal of P from the soil did not change by increasing corn planting population (55, 53, and 56 kg/ha for 60K, 75K, and 90K, respectively; P > 0.21).

Table 2. Chemical composition of corn silages as affected by year, field, hybrid, planting population, and fertilization.

 

Ash,

g/kg

CP,

g/kg

NDF,

g/kg

ADF,

g/kg

ADL,

g/kg

Starch,

g/kg

Sugars,

g/kg

P,

mg/kg

Year

 

 

 

 

 

 

 

 

   2017

38a

84a

345a

221a

12b

240b

74a

233b

   2018

34b

82b

324b

191b

15a

369a

24b

286a

   LSD1

1.5

1.2

8.7

4.6

0.8

12.2

6.4

8

Field

 

 

 

 

 

 

 

 

   Dairy

38a

82b

323b

201

14

319a

41b

302a

   Remote

35b

84a

346a

212

14

290b

58a

217b

   LSD

1.5

1.2

8.7

4.6

0.8

12.2

6.4

8

Hybrid

 

 

 

 

 

 

 

 

   CONV

33b

77b

341a

212

17a

306

53a

239b

   BMR

39a

89a

327b

201

10b

304

45b

280a

   LSD

1.5

1.2

8.7

4.6

0.8

12.2

6.4

8

Population

 

 

 

 

 

 

 

 

   60K

37

84a

322b

202b

13b

312

48

266a

   75K

36

84a

341a

206ab

14a

302

50

255b

   90K

36

81b

340a

210a

14a

300

49

257b

   LSD

1.8

1.5

10.6

5.6

0.9

15.0

7.9

10

Fertilization

 

 

 

 

 

 

 

 

   1N

36

81b

333

207

14

305

49

264a

   2N

36

85a

335

205

14

305

49

255b

   LSD

1.1

1.2

8.1

4.4

0.8

10.6

5.1

8

1 Least significant difference.

a,b Means with different superscripts differ (P < 0.05).

3. In Vitro Digestibility

Neither corn planting population nor N fertilization affected IVDMD (Table 3). Even though differences existed for IVTDMD among different planting populations (Table 3), these differences are minor and lack biological significance. Nitrogen fertilization did not affect IVTDMD. Finally, neither corn planting population nor N fertilization affected IVNDFD (Table 3).

Table 3. Digestibility coefficients of corn silages as affected by year, field, hybrid, planting population, and fertilization.

 

IVDMD

IVTDMD

IVNDFD

Year

 

 

 

   2017

0.909a

0.852a

0.580a

   2018

0.770b

0.825b

0.443b

   LSD1

0.009

0.010

0. 019

Field

 

 

 

   Dairy

0.791

0.839

0.525

   Remote

0.788

0.838

0.498

   LSD

0.009

0.010

0. 019

Hybrid

 

 

 

   CONV

0.765

0.815

0.457

   BMR

0.814

0.862

0.566

   LSD

0.009

0.010

0.019

Population

 

 

 

   60K

0.793

0.841ab

0.504

   75K

0.792

0.844a

0.526

   90K

0.783

0.831b

0.505

   LSD

0.011

0.012

0.023

Fertilization

 

 

 

   1N

0.789

0.840

0.517

   2N

0.790

0.836

0.506

   LSD

0.009

0.010

0.018

1 Least significant difference.

a,b Means with different superscripts differ (P< 0.05).

Participation Summary
1 Farmer participating in research

Educational & Outreach Activities

1 Journal articles
1 Published press articles, newsletters
9 Webinars / talks / presentations
1 Workshop field days
1 Educational video is under development. We anticipate producing and releasing the video in September 2019.

Participation Summary

150 Farmers
100 Ag professionals participated
Education/outreach description:
  • Journal articles.
    • One manuscript related to the subject was already published in Journal of Dairy Science.
    • A second manuscript with the results of this report will be submitted for publication to Animal Feed Science and Technology (June 2019).
  • Presentations
    • 2017 Texas Hispanic Farmer and Rancher Conference (McAllen, TX)
    • 2017 NRCS & DEQ Nutrient Management of Animal Operations (Blackstone, VA)
    • 2018 Virginia State Feed Association Conference and Nutritional Management Cow College (Roanoke, VA)
    • 2018 Purina Sales Training (Blacksburg, VA)
    • 2018 American Dairy Science Association (Knoxville, TN)
    • 2019 Area Dairy Conference (Amelia, VA)
    • 2019 Area Dairy Conference (Harrisonburg, VA)
    • 2019 Mid-Atlantic Nutrition Conference (Baltimore, MD)
    • 2019 American Dairy Science Association (Knoxville, TN) – ABSTRACT ALREADY ACCEPTED
  • Field Day
    • Field Day/Workshop: “Harvesting practices for maximum corn silage quality.” (Amelia, VA).
  • Press Articles and Newsletters
    • “Hitting the corn plant density sweet spot.” Hay & Forage Grower 33(2):24.

Learning Outcomes

2 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key changes:
  • Effect of corn planting density on forage yields.

  • Effect of corn planting density on forage P and N concentration.

  • Based on the data from this study, the collaborating farm decided what hybrid to use for his farm on a regular basis. This outcome was a priority of the collaborating farm.

Project Outcomes

2 Farmers changed or adopted a practice
2 Grants received that built upon this project
2 New working collaborations
Project outcomes:

We hypothesized that increasing corn planting density would increase the removal of N and P from the soil. Contrary to this hypothesis, under the conditions of this on-farm study, increasing corn planting density DID NOT increase the removal of neither N nor P from the soil. Even though the data from this project challenges our hypothesis, from another dataset we have seen that N and P removal can be increased by increasing corn planting density. We attributed this discrepancy to the different responses of biomass yields between studies. It seems that the response is intimately related to the response of dry matter yield. With this inconclusive information, we cannot affirm that this project has affected the environmental sustainability as we anticipated. 

Recommendations:

This is the third study performed by our team on this topic. Also, this was the first time we did not see a substantial increase in biomass yield in response to increased corn planting population. During year 1 there was some evidence of drought stress and, also, corn was harvested relatively early. We are quite confident that crop maturity harvesting is a critical determinant of the response of biomass yield to increased corn planting population. By all means, we will continue advancing in this are to increase economic and environmental sustainability of dairy farms.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.