Agronomy for Sustainable Development

, Volume 33, Issue 3, pp 507–517

Shallow mixing of surface soil and liquid dairy manure conserves nitrogen while retaining surface residue

Authors

    • Nutrient Management Spear Program, Department of Animal ScienceCornell University
  • Greg Godwin
    • Nutrient Management Spear Program, Department of Animal ScienceCornell University
  • Peter Barney
    • Barney Agronomic Services
  • Joseph R. Lawrence
    • Cornell Cooperative Extension of Lewis County
  • Brian Aldrich
    • Cornell Cooperative Extension of Cayuga County
  • Tom Kilcer
    • Advanced Ag Systems
  • Karl J. Czymmek
    • Nutrient Management Spear Program, Department of Animal ScienceCornell University
  • Brent Gloy
    • Department of Applied Economics and ManagementCornell University
Research Article

DOI: 10.1007/s13593-013-0141-1

Cite this article as:
Ketterings, Q.M., Godwin, G., Barney, P. et al. Agron. Sustain. Dev. (2013) 33: 507. doi:10.1007/s13593-013-0141-1

Abstract

Incorporation of spring-applied manure is known to reduce N volatilization losses and hence increase the N value of the manure. However, traditional incorporation methods are not compatible with reduced-tillage systems requiring minimum residue coverage of 30 %. Here, eight New York dairy farms participated in 2008 in a 2-year on-farm trial. This trial was designed to test the hypothesis that shallow mixing of soil involving aerator incorporation of spring-applied manure is as effective as chisel incorporation of manure in conserving manure N for corn (Zea mays, L) uptake while retaining more surface residue. The eight fields selected for this trial varied from first to third year corn after hay and had varying manure histories. All fields were subjected to a randomized complete block design with four replicates comparing surface application of manure, as control, shallow incorporation of manure with an aerator, and chisel incorporation of manure. Starter N applications were 39 kg N/ha or less, and manure application rates ranged from 51 to 112 kL/ha. Results show that shallow incorporation of manure significantly reduced soil disturbance and retained, on average, 30 % more surface residue cover than obtained with chisel incorporation. Chisel and aerator-based incorporation resulted in similar soil nitrate levels at 13 of 16 site years, suggesting similar levels of N conservation. Across all sites and years, incorporation increased silage yield by 0.9–1.5 Mg DM/ha, independent of incorporation method. Based on these results, we show that shallow mixing of soil and spring-applied manure is a suitable option for conserving N and maintaining greater surface residue coverage without compromising on yield or silage quality.

Keywords

CornForageNitrogenNutrient managementNutrient cyclingSoil conservationTillage

Abbreviations

CSNT

Corn stalk nitrate test

DM

Dry matter

ISNT

Illinois soil nitrogen test

PSNT

Pre-sidedress nitrate test

1 Introduction

Environmental concerns associated with surface application of manure and rising costs of both N fertilizer and fuel have led many dairies in New York to spring-apply and incorporate manure for corn production, taking advantage of reductions in P runoff risk, and odor and ammonia N emission (Meisinger and Jokela 2000; Quincke et al. 2007), while benefitting from the soil improvement properties of manure (Nyiraneza et al. 2009).

When full incorporation with a moldboard plow is used, much of the remaining surface residue is mixed into the soil profile, leaving very little residue on the surface (Brown et al. 1992; Shapiro et al. 2001), negatively impacting soil quality (Maguire et al. 2011; Pierce et al. 1994). Chisel plows and disks can leave behind more surface residue than moldboard plowing while reducing the number of trips across a field (Oregon NRCS 2007; Maguire et al. 2011), but such semi-aggressive tillage equipment can still result in considerable loss of surface residue (Raper 2002; Shelton 2004). Shallow mixing of the surface soil with the manure using aerators is expected to result in less disturbance of the soil and greater residue coverage (Bittman et al. 2005; Harrigan et al. 2006; Maguire et al. 2011). Such aerators (Fig. 1), either solid-tine and core configurations, can, when set at an angle, lightly cultivate the surface soil and hence partially incorporate previously applied manure (Franklin et al. 2006, 2007; Lawrence et al. 2008; Maquire et al. 2011).
https://static-content.springer.com/image/art%3A10.1007%2Fs13593-013-0141-1/MediaObjects/13593_2013_141_Fig1_HTML.jpg
Fig. 1

Photographs of the manure incorporation methods, aerator and chisel

In situations where N limits crop production, spring incorporation of manure can result in higher corn yield (Klausner and Guest 1981; Lawrence et al. 2008). In a study by Lawrence et al. (2008), shallow incorporation of spring-applied liquid dairy manure using an aerator within an hour after spreading was effective in conserving N and resulted in similar or higher corn grain yield than what was obtained after chisel incorporation of the manure. In contrast, Chen et al. (2001) reported no increase in yield as a result of aerator use before manure application on grasslands using liquid swine manure. Placement of the tillage operation (before or after manure application), aggressiveness of the tillage tool (angle), and timing of application will impact N conservation (Maguire et al. 2011), but research that quantifies this is scant.

The objectives of this study were to compare the impact of shallow incorporation (mixing) of spring-applied manure using aerator technology with that of chisel incorporation of manure and a no-incorporation control on (1) surface residue cover, (2) corn silage yield and forage quality, and (3) soil N conservation under farmer managed field conditions.

2 Materials and methods

2.1 Site locations and experimental design

Eight farm fields were selected by county extension educators and agronomic crop consultants to represent corn production areas throughout New York. Soil types ranged from silty clay loams to gravelly loams (Table 1). In 2008, the first year of the project, five of eight sites were second year corn, two were third year corn, and there was one first year corn site. Trials consisted of three treatments: (1) surface application of manure with no incorporation, (2) surface application of manure directly followed by chisel incorporation, and (3) surface application of manure directly followed by aerator incorporation. The trials were conducted using a complete randomized block design with three (one location) or four replications (seven locations). Plot sizes varied depending on farmer equipment and ranged from 12 to 20 rows wide (76-cm rows) and 91 to 213 m long with the inner six to ten rows harvested for yield measurements. There were planter problems that impacted the entire trial area at one of the locations in 2008 (resulting in a stand density of less than 46,000 plants/ha; Site 4) but for all other locations and years, stand densities ranged from about 77,000 to 87,000 plants/ha (Table 1). Fifteen of the 16 trials were harvested for corn silage. One location (Site 6) was harvested for grain in 2008. One location (Site 8) was seeded with a winter cover crop of cereal rye (Secale cereale L.) in the fall preceding the incorporation treatments (Site 8 in 2008 and 2009).
Table 1

Site and field characteristics (soil type, rotation, initial sodium acetate extractable nitrate-N, P, and K) with manure application rates and corn stand density for 2008 and 2009

Site

County

Soil series

Corn year in rotation

Initial soil fertility in 2008a (mg kg−1)

Spreading rate (kL ha−1)

Stand density (plants ha−1)

2008

2009

N

P

K

2008

2009

2008

2009

1

St. Lawrence

Muskellunge silt loam

2

3

8

2 L

33 L

65.45

60.78

77,543

78,709

2

Columbia

Rhinebeck silt loam

3

4

2

1 L

28 L

74.80

74.80

73,302

77,966

3

St. Lawrence

Hogansburg gravelly loam

2

3

18

4 M

114 H

84.15

56.10

74,520

76,985

4

Chenango

Howard gravelly loam

3

4

12

12 H

131VH

77.61

81.81

45,927

79,408

5

Cayuga

Honeoye loam

1

2

13

15 H

175 VH

65.45

112.20

66,986

87,117

6

Lewis

Amenia loam

2

3

16

6 H

75 H

49.09

49.09

84,437

85,222

7

Clinton

Malone loam

2

3

15

6 H

45 L

84.15

84.15

76,928

77,474

8

Cayuga

Honeoye loam

2

3

11

11 H

109 VH

74.80

74.80

74,969

78,339

Extractable P and K are classified as L = low, M = medium, H = high, and VH = very high, depending on probability of an economic crop response according to Cornell University guidelines for corn management (Cornell Cooperative Extension 2013)

aSodium acetate-extractable nitrate N, P, and K (Morgan 1941)

2.2 Field management

Liquid dairy manure application rates varied from just above 49 to 112.2 kL ha−1, but at most locations the targeted 65.5–84.2 kL ha−1 were applied (Table 1). The incorporation treatments were implemented within 1 h after manure application. The depth of incorporation ranged from 0.15 to 0.2 m for aeration set at a 15° angle (maximum angle) and 0.25 to 0.35 m for chisel incorporation. Seedbed preparation took place five or more days after application to ensure ammonia volatilization from the surface-applied, non-incorporated manure. All sites were limited to 39 kg ha−1 of N applied as a banded application in the starter fertilizer with no sidedress fertilizer applications, except for one site in 2008 (Site 7) that was sidedressed with 129 kg ha−1 of fertilizer N (Table 2). At most sites, the 2008 and 2009 growing seasons were wet, and in 2009, temperatures were also cooler than normal for June and July—resulting in a lower average corn yield for New York State [15.8 Mg dry matter (DM) ha−1 in 2008 versus 14.0 Mg DM ha−1 in 2009; USDA-NASS 2010].
Table 2

The total corn crop nutrients available (N, P2O5, and K2O in 2008/2009) at eight locations in the liquid dairy manure application study

Site

Treatment

Manure nutrients available

Fertilizer

Total

N

P

K

N

P

K

N

P

K

kg ha−1 (2008/2009)

1

Surface

38/31

26/26

138/127

38/38

7/7

0/0

76/69

33/34

138/127

Incorporation

115/106

153/144

2

Surface

46/37

34/33

156/158

24/22

9/10

23/0

69/59

43/42

179/158

Incorporation

122/116

146/139

3

Surface

35/17

38/20

211/82

26/37

5/0

0/0

60/54

44/20

211/82

Incorporation

127/69

152/106

4

Surface

47/41

50/40

201/187

34/0

24/0

9/0

81/41

75/40

210/187

Incorporation

101/141

134/141

5

Surface

19/39

19/44

117/200

36/28

15/0

0/0

55/67

34/44

117/200

Incorporation

64/127

100/155

6

Surface

11/26

19/20

79/86

0/0

0/0

0/0

11/26

19 / 20

79/86

Incorporation

52/73

52/73

7

Surface

35/7

15/15

99/95

129/36

26/24

49/46

164/43

41/39

148/141

Incorporation

83/25

212/60

8

Surface

64/22

30/29

164/197

34/34

0/0

0/0

97/56

30 / 29

164/197

Incorporation

129/104

162/138

Available N from manure assumes 35 % availability of the organic N in the manure and 0 % (surface application) or 65 % availability of the ammonium-N fraction of the manure (incorporation with a chisel plow)

2.3 Manure sampling and analysis

A minimum of three manure samples were taken from the manure spreader at the time of application in each of the 2 years. Samples were kept cool while in the field and frozen upon arrival at the laboratory for later analysis. The samples were analyzed for total N (AOAC 2000a) and ammonia N (AOAC 2000b) at the DairyOne Forage Analysis Laboratory. The organic N was estimated as the difference between total N and ammonia N. Samples were analyzed for P and K content (Sirois et al. 1994), total solids (Hoskins et al. 2003), and density using a 51.5-ml standard vial (DairyOne 2007). Nutrient availability from the manure was estimated assuming 100 % availability of P and K and 35 % N available from the organic N fraction of the manure (Ketterings et al. 2003). Availability of N from the inorganic fraction was estimated assuming 0 % N conservation for the unincorporated surface application and 65 % N conservation for incorporation with a chisel plow (Ketterings et al. 2003).

2.4 Surface residue

Surface residue measurements were taken from 0 to 19 days after surface application of manure and incorporation treatment, varying by site and year due to practical limitations imposed by the large geographic distances among sites and weather in relationship to corn planting time. A 30-m rope with 0.3-m indicators (100 marks) was used to determine residue coverage (Oregon NRCS 2007). Per plot, three measurements were taken by laying the rope diagonally across the plot and counting the number of marks that had corn or sod residue, or fresh cereal rye, or weed cover underneath. The three measurements were averaged to determine the percent surface residue cover for each treatment.

2.5 Soil sampling

Soil samples were taken for soil fertility and soil nitrate assessment at a depth of 0–20 cm four times during the growing season: (1) before manure application, (2) at planting, (3) when the corn was 0.15 to 0.30 m tall (4–6 leaf stage), and (4) at harvest. In addition, 0–30-cm soil samples were taken to determine the pre-sidedress nitrate test (PSNT). The sampling depth is standard depth of sampling for soil fertility testing, while the 0–30-cm depth is required for PSNT sampling in New York (Klausner et al. 1993). Given that shallow and stony soils are common in New York, sampling to deeper depths is not practical. At each sampling time, 15 cores were taken per plot. Samples were kept cool while in the field and, upon arrival at the laboratory, placed in an oven (50 °C) to dry for a minimum of 48 h, prior to crushing to pass a 2-mm sieve. Gravimetric soil moisture was determined by weight loss of 2-mm sieved field-moist soil after drying in a 105 °C oven over night. Samples were analyzed for pHwater, organic matter by loss-on-ignition (Storer 1984), and sodium acetate extractable N, P, K, (Morgan 1941) at the Cornell Nutrient Analysis Laboratory according to methods described in Wolf and Beegle (1995). The 0–0.30-m-depth samples were analyzed for the PSNT using the Morgan extraction per standard methodology (Morgan 1941). An Alpkem automated flow analyzer (RFA/2-320; OI Corporation, College Station, TX) was used to measure the Morgan extractable NO3-N and PO4-P colorimetrically (Murphy and Riley 1962). Ammonium levels are typically low in the humid Northeast (Klapwyk et al. 2006) and were therefore not included in the measurements. Morgan extractable K was measured using a JY70 Type II ICP-AES (Jobin Yvon, Edison, NJ). The 0–20-cm-depth samples taken at PSNT time were also analyzed for the Illinois soil nitrogen test (ISNT) according to Khan et al. (2001) with the enclosed griddle modification (Klapwyk and Ketterings 2005). The ISNT has been accurate in separating fields with a high soil N supply potential from those with insufficient N supply for corn growth in studies in New York (Klapwyk and Ketterings 2006; Lawrence et al. 2009).

2.6 End-of-season corn stalk nitrate test

Fifteen stalks were sampled per plot at harvest. A 0.20-m portion was cut from each stalk 0.15 m above the ground, following protocols outlined in Binford et al. (1990). Samples were placed in a 50 °C forced-air oven for a minimum of 48 h and then ground to pass a 2-mm sieve prior to nitrate analysis. Stalks were analyzed for corn stalk nitrate test (CSNT)-N using 0.05 mol L−1 Al2(SO4)3 and a 2 mol L−1 (NH4)2SO4 ionic strength adjustor according to Wilhelm et al. (2000). A nitrate selective electrode and 710A pH/ISE meter (Thermo Scientific Orion, Waltham, MA) were used.

2.7 Corn yield and forage quality

Plots (inner six to eight rows) were harvested using the farmer’s equipment, and wet weights were determined using farm scales, portable wheel load scales or yield monitors. A well-mixed subsample was taken per plot (3–4 L volume). The subsamples were kept cool while in the field and transferred to ovens upon arrival in the laboratory for moisture determination using a 50 °C forced air oven for a minimum of 48 h. Subsamples were analyzed at the Cumberland Valley Analytical Services, Inc. laboratory in Hagerstown, MD for crude protein (CP) (AOAC 2000a); soluble protein (Krishnamoorthy et al. 1982); neutral detergent fiber (30 h, NDF30; and 48 h, NDFD) (Van Soest et al. 1991), using Whatman 934-AH glass micro-fiber filters with 1.5 μm particle retention modification; lignin (Goering and Van Soest 1970); starch (Holm et al. 1986); fat (AOAC 2006); and ash (AOAC 2000c), using 1.5 g sample weight with 4-h ash time. Estimated milk production per Mg and per hectare of corn silage was determined using Milk2006 with corn yield and DM, CP, NDF, NDFD, starch, fat, and ash as input variables (Shaver et al. 2006).

2.8 Statistical analysis

Data were analyzed using PROC MIXED (Littell et al. 1996) of the Statistical Analysis System (SAS Institute 1998). Each field and each year were analyzed individually due to site to site variability in field management histories, soil types and weather patterns, the potential for carryover of N benefits from manure applications in 2008 into 2009, and year to year weather differences. Manure application method was considered a fixed effect and blocks as random effect. A year analysis across all corn silage sites was done with manure application method and farm as fixed effects for each of the 2 years. This analysis was repeated for sites where silage CP from corn grown on the control plots (surface applied manure) was more than 70 g kg−1 and CSNT exceeded 5,000 mg kg−1, essentially excluding locations where silage quality data indicated that N supply was not yield limiting. Where treatment effects were significant, mean separations were done using the LSMEANS procedure with TUKEY adjustment at P ≤ 0.05.

3 Results and discussion

3.1 Surface residue

Both manure incorporation methods, aerator and chisel, reduced surface residue as compared to the unincorporated treatment (Fig. 2). Chisel plow incorporation of manure on fields with more than 20 % residue cover reduced surface residue by 13–74 % (with an average reduction of 41 %). A similar study by Coulter and Nafziger (2008), who compared chisel plowing with no-till following grain corn, reported a 25–40 % reduction in surface residue cover upon chisel plowing with no or partial removal of the stover before tillage, an indication that chisel plowing can significantly reduce surface residue cover in low residue production systems.
https://static-content.springer.com/image/art%3A10.1007%2Fs13593-013-0141-1/MediaObjects/13593_2013_141_Fig2_HTML.gif
Fig. 2

Shallow mixing and incorporation of spring-applied liquid dairy manure using an aerator significantly reduced soil disturbance and retained, on average, 30 % more surface residue cover than obtained with chisel incorporation of manure

Aerator incorporation resulted in less residue disturbance than chisel incorporation when unincorporated surface residue coverage exceeded 20 % in our study. Aerator incorporation (maximum, 15° angle) reduced surface residue by 9–53 % compared to no incorporation for fields where the initial surface residue cover exceeded 20 %. The impact of aeration on surface residue will depend on the angle of the aerator. Sexton et al. (2005) measured only minimal soil disturbance of 20–22 % from aeration (no angle) with a surface residue disturbance of 18–23 % in barley stubble, stating that aeration met their low disturbance guidelines of 30 % or less. Similar results were reported by Harrigan et al. (2006) who measured a 14 % reduction in surface residue cover after passing an aerator over wheat stubble (10° angle) residue when the field was aerated using a 0° angle.

The NRCS defines conservation tillage as any system that can meet the 30 % residue cover requirement after corn planting set by the Conservation Technology Information Center Core Conservation Practices (NRCS 1999). At three sites, residue coverage on the unincorporated manure treatment plot was greater than 60 %, attributable to previous cropping history. In these locations, residue cover levels exceeding 30 % were obtained when the aerator was used to incorporate manure for first year corn after sod (Site 5, 2008), for corn silage after corn grain (Site 6, 2009), and if a cover crop was used (Site 8, 2009; poor stand in 2008), indicating potential for soil conservation with aerator incorporation if used in corn grain or after rotation into corn from sod or cover crops. Residue coverage measurements in our study were done at or after planting at 4 of 16 locations over the 2 years, while at the other locations, assessments took place before planting. It is unknown if planting impacted residue coverage, but from our results, it is clear that aerator incorporation of manure does conserve more residue than chisel plowing.

3.2 Soil N, PSNT, CSNT

Soil samples taken pre-manure application (baseline) in 2008 ranged in soil nitrate N (NO3–N) from less than 2 to over 18 mg kg−1, reflecting site to site differences, consistent also with the range in ISNT-N values for the sites (Table 3). At all but two locations, soil nitrate levels prior to manure application exceeded 10 mg kg−1. The lowest nitrate levels were measured at sites that did not have a recent manure history and were low in P and K as well (Sites 1 and 2, Table 1). In 2009, baseline nitrate levels were less than 10 mg kg−1 for five of the eight locations, while only three locations (Sites 3, 6, and 7) showed levels between 10 and 16 mg kg−1 (Table 3), reflecting the relatively cold April of 2009 for most of the sites.
Table 3

Soil nitrate levels in (0–20 cm depth) taken at four different times (baseline—i.e., pre-manure application; at corn planting; at sidedress time; and at harvest) for each site in 2008 and 2009 as impacted by manure application method (surface application without incorporation versus direct incorporation with a chisel plow or aerator)

Site

Treatment

Year

Baseline

Planting

Sidedress

Harvest

Year

Baseline

Planting

Sidedress

Harvest

  

mg kg−1 NO3–N

  

mg kg−1 NO3–N

1

Surface

2008

8.8

30.5

 

26.5

 

4.0

b

2009

7.5

20.3

 

26.3

 

11.8

 

Chisel

7.4

36.4

 

30.4

 

9.3

a

8.9

21.4

 

28.9

 

12.7

 

Aerator

8.4

36.5

 

34.5

 

7.9

a

7.2

25.5

 

30.5

 

13.9

 

2

Surface

2008

1.7

5.9

 

20.5

 

2.0

 

2009

2.2

21.9

b

29.0

b

0

 

Chisel

1.9

5.2

 

21.4

 

0

 

4.4

21.2

b

48.0

a

0

 

Aerator

2.7

4.9

 

24.4

 

0

 

2.2

31.2

a

39.9

ab

0

 

3

Surface

2008

16.9

34.4

b

46.0

 

18.7

 

2009

11.2

28.4

b

45.0

 

9.8

 

Chisel

18.3

48.7

a

53.9

 

26.5

 

15.7

46.8

a

57.7

 

17.3

 

Aerator

16.7

42.9

ab

45.7

 

22.8

 

12.8

36.9

ab

52.8

 

11.0

 

4

Surface

2008

10.2

14.4

b

24.5

b

12.9

 

2009

1.4

15.3

b

27.2

b

7.3

 

Chisel

12.5

32.2

a

49.4

a

17.5

 

1.5

20.9

a

42.2

a

8.3

 

Aerator

11.9

22.5

ab

31.4

ab

14.5

 

2.7

15.7

a

39.3

a

7.2

 

5

Surface

2008

12.4

33.4

 

54.4

 

18.4

 

2009

6.9

39.7

 

41 7

 

12.8

 

Chisel

11.9

39.0

 

67.5

 

24.7

 

6.7

53.3

 

53.8

 

14.0

 

Aerator

13.8

39.7

 

66.9

 

18.4

 

5.4

39.2

 

43.4

 

12.0

 

6

Surface

2008

15.9

43.0

 

57.4 b

 

.

 

2009

13.9

22.8

 

29.0

 

8.8

 

Chisel

16.2

51.5

 

72.7 a

 

.

 

12.3

28.5

 

28.9

 

10.7

 

Aerator

16.0

42.8

 

62.3 ab

 

.

 

11.8

27.9

 

29.2

 

9.7

 

7

Surface

2008

14.8

21.3

 

17.9

 

10.2

 

2009

13.5

14.9

 

21.2

 

13.2

 

Chisel

14.9

10.5

 

16.0

 

8.9

 

12.7

17.8

 

26.5

 

12.2

 

Aerator

14.3

19.5

 

14.0

 

11.0

 

13.5

17.7

 

22.9

 

12.2

 

8

Surface

2008

10.8

20.3

 

45.0

 

8.7

 

2009

6.9

19.7 b

 

17.3

 

9.3

b

Chisel

11.2

31.9

 

45.0

 

11.0

 

5.2

39.3a

 

20.4

 

14.8

a

Aerator

10.5

27.5

 

44.7

 

9.3

 

6.3

25.5 b

 

19.5

 

11.5

ab

Mean comparisons were done for each site and each year individually where the overall treatment effect was significant (α ≤ 0.05). Means followed by a different letter (a, b) within a site and year are significantly different at α ≤ 0.05

At planting, soil nitrate levels (0–20 cm depth) tended to be lower where manure was surface-applied without incorporation as compared to chisel incorporation, but means were only significantly different at three of the eight locations in each of the 2 years (Sites 3, 4, and 8; Table 3). At sidedress time, means were significantly different at two of the eight sites in each of the 2 years (Sites 4 and 6 in 2008 and Sites 2 and 4 in 2009). Soil nitrate levels at harvest were lower with non-incorporated manure only at Site 1 in 2008 and at Site 8 in 2009.

There were no significant differences in soil nitrate levels between the aerator and chisel incorporation treatments at 62 of the 64 sampling times in 2008 and 2009 combined. Only one site (Site 8) showed higher soil nitrate levels at planting with chisel incorporation than with aerator incorporation in both years of the study (Table 4). The PSNT values ranged from 10 to 58 mg kg−1 in 2008. The PSNT values suggested a potential N deficiency (PSNT ≤ 24 mg kg−1) for three sites (Sites 1, 2, and 7) when manure was surface applied and not incorporated and more than sufficient N for all other sites (Table 4). In 2009, PSNT values ranged from 10 to 50 mg kg−1. At two of the eight sites (Sites 3 and 5), the PSNT of plots where manure had been surface applied and not incorporated exceeded 24 mg kg−1, the critical value according to New York State PSNT interpretations (Ketterings et al. 2003).
Table 4

Impact of surface application of manure, chisel incorporation of manure, and aerator incorporation (shallow mixing) of manure on the Illinois soil nitrogen test (ISNT), pre-sidedress nitrate test (PSNT), and end-of -season corn stalk nitrate test (CSNT) for eight sites in 2008 and 2009

Site

Treatment

Year

ISNT

PSNT

CSNT

Year

ISNT

PSNT

CSNT

    

mg NO3-N kg-1

  

mg NO3-N kg-1

1

Surface

2008

346

22.6

b

191

 

2009

372

20.2

 

419

 

Chisel

354

28.0

ab

1095

 

395

22.8

 

879

 

Aerator

383

32.8

a

840

 

378

21.9

 

1029

 

2

Surface

2008

211

9.7

 

124

ab

2009

211

20.9

b

120

 

Chisel

208

17.0

 

363

a

217

33.5

a

151

 

Aerator

219

13.0

 

108

b

222

29.4

ab

109

 

3

Surface

2008

357

49.5

 

8171

 

2009

374

47.2

 

5654

 

Chisel

378

48.0

 

9845

 

362

51.0

 

8209

 

Aerator

373

42.5

 

8134

 

371

49.7

 

8068

 

4

Surface

2008

301

24.7

b

2858

b

2009

317

23.2

b

250

b

Chisel

334

46.3

a

6392

a

341

41.7

a

1150

a

Aerator

320

26.9

b

3545

b

328

31.4

ab

635

ab

5

Surface

2008

216

40.5

 

6131

 

2009

229

38.8

 

2240

b

Chisel

227

50.0

 

6903

 

236

44.7

 

4287

a

Aerator

223

50.5

 

6458

 

238

38.9

 

2848

ab

6

Surface

2008

466

57.9

 

2535

 

2009

489

18.4

 

227

 

Chisel

472

57.8

 

2751

 

477

18.2

 

332

 

Aerator

471

57.9

 

1795

 

487

17.2

 

200

 

7

Surface

2008

355

12.5

 

30

 

2009

314

19.8

 

52

 

Chisel

351

12.8

 

9

 

296

14.5

 

48

 

Aerator

363

13.0

 

21

 

307

9.7

 

50

 

8

Surface

2008

243

36.4

 

5432

 

2009

250

14.9

b

1126

b

Chisel

239

42.6

 

8167

 

237

21.8

a

3407

a

Aerator

245

40.5

 

4516

 

247

16.7

b

1330

b

A PSNT <21 mg kg−1 is nitrate deficient and PSNT ≥25 mg kg−1 is nitrate sufficient; CSNT <250 mg kg−1 indicates additional N was needed, 250–750 mg kg−1 indicates N was marginal, 750–2,000 mg kg−1 indicates N was optimal, >2,000 mg kg−1 indicates N was available in excess of crop needs. Mean comparisons were done for each site and each year individually where the overall treatment effect was significant (α ≤ 0.05). Means followed by a different letter (a, b) within a site and year are significantly different at α ≤ 0.05

Chisel incorporation of manure resulted in significantly higher PSNT than for aerator incorporation at one location in 2008 (Site 4) and another location in 2009 (Site 8). At these two locations, the aerator incorporation resulted in values no different from the PSNT results of surface-applied manure. There were no differences in PSNT between aerator and chisel plots at any of the other locations.

The 2008 CSNT results ranged from 9 to almost 10,000 mg NO3–N kg−1. At five locations that year, CSNT results suggested excess N (>2,000 mg kg−1; Table 4). These were the same five locations with PSNTs exceeding 24 mg kg−1. In 2009, CSNT samples ranged from approximately 50 to 8,000 mg kg−1. That year two of the eight sites were classified as excessive in N supply based on CSNT results and consistent with the PSNT data (Sites 3 and 5). In general, CSNT results were considerably lower in 2009 than in 2008. There were no significant differences in CSNT between chisel and aerator incorporation at 13 of the 16 site years, while at the remaining three site years, chisel incorporation resulted in significantly higher CSNT, consistent with the higher PSNT values for the chisel incorporation treatment at two of these three sites.

3.3 Corn yield, forage quality, and N conservation

There were no significant yield differences between plots where manure was shallowly mixed with soil using the aerator and plots where manure had been incorporated with a chisel plow (Table 5). In 2008, the two incorporation treatments resulted in significantly higher yields than the surface application at three of the eight locations, while at several other locations a similar trend was seen. Across all locations, an average yield increase of 0.8 Mg ha−1 was obtained with incorporation of manure, independent of the method of incorporation. In 2009, there were no significant yield differences among the incorporation treatments and surface application for any of the individual sites, but across all sites, incorporation of manure resulted in a significant 0.9 Mg ha−1 increase in yield.
Table 5

Corn silage yield (DM, dry matter), forage quality (crude protein, soluble protein, neutral detergent fiber (NDF), 48-h digestibility of NDF (NDFD), lignin, and starch), and milk production estimates for 2008 and 2009 at each site as impacted by surface application of liquid dairy manure, chisel incorporation of manure, and aerator incorporation (shallow mixing) of manure

Site

Treatment

Dry matter yielda

Crude protein

Soluble protein

NDF

NDFD

Lignin

Starch

Milk per Mg

Milk per hectare

Mg DM ha−1

 

mg  kg−1 DM

mg  kg−1 NDF

 

mg  kg−1 DM

kg  Mg−1

kg  ha−1

2008

1

Surface

13.6

b

59

 

16

 

463

 

680

 

33

 

307

 

1,417

 

23,449

b

Chisel

15.2

a

64

 

17

 

454

 

666

 

34

 

305

 

1,411

 

26,037

a

Aerator

15.2

a

64

 

16

 

451

 

670

 

34

 

311

 

1,416

 

26,210

a

2

Surface

16.1

 

62

 

18

 

364

 

667

 

25

 

416

 

1,504

 

29,347

 

Chisel

15.8

 

66

 

18

 

385

 

655

 

27

 

392

 

1,482

 

32,057

 

Aerator

17.3

a

67

 

18

 

338

 

671

 

23

 

443

 

1,534

 

32,275

 

3

Surface

16.2

 

71

 

20

 

445

 

624

 

32

 

318

 

1,363

 

26,799

 

Chisel

15.8

 

73

 

20

 

413

 

624

 

31

 

351

 

1,398

 

26,787

 

Aerator

16.5

 

73

 

19

 

427

 

662

 

32

 

336

 

1,378

 

27,783

 

4

Surface

10.0

 

63

 

16

 

482

 

637

 

36

 

294

 

1,347

 

16,227

b

Chisel

11.9

a

68

 

16

 

456

 

621

 

34

 

327

 

1,359

 

19,640

a

Aerator

11.7

a

67

 

17

 

448

 

620

 

33

 

328

 

1,368

 

19,406

a

5

Surface

21.7

 

72

 

18

 

372

 

634

 

30

 

365

 

1,469

 

38,609

 

Chisel

21.2

 

72

 

18

 

376

 

633

 

30

 

359

 

1,458

 

37,713

 

Aerator

21.2

 

71

 

18

 

383

 

640

 

31

 

353

 

1,457

 

37,639

 

6†

Surface

6.9

b

.

 

.

 

.

 

.

 

.

 

.

 

.

 

.

 

Chisel

88

a

.

 

.

 

.

 

.

 

.

 

.

 

.

 

.

 

Aerator

9.3

a

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

7

Surface

93.

 

60

 

17

 

404

 

689

 

27

 

367

 

1,492

 

16,704

 

Chisel

10.1

 

61

 

17

 

405

 

686

 

27

 

368

 

1,489

 

18,238

 

Aerator

10.6

 

59

 

16

 

389

 

675

 

26

 

391

 

1,500

 

19,320

 

8

Surface

16.6

 

74

 

20

 

451

 

764

 

23

 

311

 

1,475

 

29,811

 

Chisel

17.0

 

77

 

21

 

449

 

777

 

24

 

315

 

1,488

 

30,681

 

Aerator

16.9

 

74

 

20

 

454

 

770

 

24

 

311

 

1,482

 

30,535

 

All

Surface

14.8

b

66

b

18

 

428

a

671

 

29

 

341

 

1,438

 

25,925

b

Chisel

15.5

a

69

a

18

 

424

a

668

 

30

 

346

 

1,442

 

27,259

a

Aerator

15.7

a

68

ab

18

 

407

 

668

 

29

 

352

 

1,447

 

27,570

a

2009

1

Surface

14.7

 

69

 

16

 

440

 

738

 

24

 

347

 

1,497

 

26,644

 

Chisel

14.6

 

73

 

16

 

439

 

740

 

25

 

353

 

1,509

 

26,742

 

Aerator

14.6

 

76

 

17

 

442

 

74.1

 

2.4

 

34.6

 

1,495

 

26,533

 

2

Surface

8.9

 

59

 

16

 

397

 

700

 

24

 

406

   

16,175

 

Chisel

10.0

 

58

 

14

 

398

 

686

 

25

 

402

 

1,482

 

17,932

 

Aerator

10.4

 

56

 

15

 

387

 

677

 

24

 

422

 

1,491

 

18,817

 

3

Surface

15.5

 

80

 

20

 

395

b

774

 

21

 

378

a

1,513

a

28,548

 

Chisel

15.7

 

78

 

19

 

408

ab

791

 

21

 

357

b

1,503

ab

28,668

 

Aerator

16.2

 

81

 

20

 

424

a

787

 

22

 

344

b

1,500

b

29,551

 

4

Surface

9.2

 

74

b

15

b

534

 

617

 

35

 

261

 

1,292

 

14,420

 

Chisel

11.1

 

83

a

16

ab

534

 

615

 

36

 

260

 

1,249

 

16,839

 

Aerator

10.6

 

81

a

17

a

527

 

609

 

35

 

263

 

1,264

 

14,875

 

5

Surface

19.5

 

69

 

15

 

429

 

603

 

30

 

399

 

1,363

 

32,334

 

Chisel

21.0

 

71

 

15

 

430

 

601

 

31

 

394

 

1,360

 

34,742

 

Aerator

20.1

 

70

 

15

 

438

 

601

 

32

 

388

 

1,349

 

32,976

 

6

Surface

13.4

 

70

 

18

 

473

 

649

 

32

 

291

 

1,382

 

22,558

 

Chisel

14.3

 

69

 

18

 

474

 

664

 

31

 

294

 

1,399

 

24,282

 

Aerator

14.9

 

70

 

18

 

477

 

651

 

32

 

285

 

1,381

 

24,972

 

7

Surface

6.7

 

63

 

16

 

455

 

790

 

22

 

271

 

1,439

 

11,628

 

Chisel

7.3

 

65

 

17

 

446

 

787

 

22

 

283

 

1,464

 

12,975

 

Aerator

7.6

 

64

 

17

 

452

 

788

 

23

 

267

 

1,431

 

13,288

 

8

Surface

17.9

 

71

 

19

 

388

 

660

 

27

 

378

 

1,497

 

32,529

 

Chisel

19.3

 

73

 

19

 

398

 

657

 

29

 

362

 

1,482

 

34,640

 

Aerator

18.7

 

71

 

19

 

392

 

652

 

28

 

373

 

1,481

 

33,760

 

All

Surface

13.2

b

69

 

17

 

439

 

691

 

27

 

342

 

1,435

 

23,115

 

Chisel

14.1

a

71

 

17

 

437

 

693

 

27

 

338

 

1,432

 

24,574

 
 

Aerator

14.0

a

71

 

17

 

440

 

689

 

28

 

336

 

1,424

 

24,320

 

Season average yields were based on corn silage yields only. Mean comparisons were done for each site and each year individually and across all sites. Means followed by a different letter (a, b) within a site (or for all sites together) are significantly different at α ≤ 0.05

aCorn was harvested for grain in 2009 at farm 6 versus silage for all other sites and years

In 2008, manure application method did not impact silage quality for any of the sites (Table 5). Differences in milk per hectare estimates reflected silage yield differences only. In 2009, surface application resulted in a reduction in CP for one of the eight locations, while at another location, a slight reduction in NDF was measured. A slight reduction in starch was measured at one of the sites for the incorporation treatments, with significant mean differences in milk production per Mg of silage for aerator incorporation in comparison to surface application. These forage quality differences did not significantly impact the overall milk production estimates per hectare for 2009.

The 2 years showed very different growing conditions. The 2009 growing season was characterized as cold and wet. The 2008 growing season allowed for higher yields due to warmer and less saturated conditions. These seasonal differences are reflected in soil nitrate, CSNT, and yield data. For example, across all sites and treatments, silage yield averaged 1.6 Mg ha−1 less in 2009 than in 2008. The PSNT results did not necessarily reflect the wetter 2009 season as a considerable amount of precipitation occurred after sampling for PSNT.

The lack of a yield response at several individual sites indicates N was not limiting production, and this was confirmed by PSNT, CP, and CSNT levels. When the three sites that had CP levels of 70 g kg−1 or higher and CSNT over 5,000 mg kg−1 were excluded from the average yield calculation across sites, yield with surface application of manure averaged 12.2 Mg ha−1, versus 13.7 Mg ha−1 for aerator or chisel incorporation. This 1.5-Mg ha−1 yield difference was once again independent of incorporation method, further supporting the hypothesis that shallow mixing is equally effective in conserving N as chisel plowing and that incorporation results in a yield increase where N is limiting production. Despite the weather-impacted lower yields in 2009, a similar trend was seen that year: without the four sites that had CP levels of 70 mg kg−1 or higher that year, yields averaged 12.6 Mg ha−1 with surface application without incorporation versus 13.4 and 13.5 Mg ha−1 for chisel and aerator incorporation, respectively. These yield results are consistent with data reported by Lawrence et al. (2008) that showed no yield penalty for shallow incorporation with an aerator as compared to chisel plowing of spring-applied manure in 2 of 3 years in the study, with higher yield with aerator incorporation than with chisel plow incorporation in the third year of the study, a dry planting season. Few studies on application methods have been done with corn, but the literature includes several studies with grass. Consistent with our results, Bittman et al. (2005) reported an overall yield increase of 4.4 % for tall fescue (Festuca arundinacea Schreb.) and orchardgrass (Dactylis glomerata L.) when liquid dairy manure was surface banded directly over aeration slots compared to just surface banding manure. In contrast, Chen et al. (2001) did not report a grass yield difference due to aeration before swine manure application. The differences seen in these two studies may be attributed to the degrees of tillage angle as Bittman et al. (2005) utilized a 2.5° angle for aeration to reduce soil disturbance and yield losses in comparison to a 15° aeration angle utilized by Chen et al. (2001) to maximize manure infiltration. The latter could have resulted in stand damage, offsetting a potential yield response due to greater manure N use efficiency. The corn study by Lawrence et al. (2008) and our eight-farm study were conducted by spreading liquid manure before aeration at a 15° angle so as to incorporate the manure quickly and to provide better mixing of the manure with the surface soil. The results indicate that such shallow mixing after manure spreading conserved N as compared to leaving manure on the surface.

4 Conclusions

Shallow incorporation of manure resulted in greater surface residue conservation compared to chisel incorporation with no measurable impact on soil compaction. Manure N conservation was similar for both incorporation treatments and resulted in a 0.9–1.5 Mg ha−1 yield increase across all sites. The additional N from manure incorporation did not increase corn yields where N supply was already sufficient as illustrated by a CSNT of 5,000 mg kg−1 or higher and CP levels of 70 mg kg−1 or higher for corn grown on plots where manure had not been incorporated. We conclude that shallow incorporation of manure is a suitable alternative to chisel incorporation in reduced tillage systems for reducing N volatilization from manure and maintaining surface residue cover.

Acknowledgments

The authors thank Anne Place, Kevin Dietzel, Chie Miyomoto, Patty Ristow, Sarah Wharton, Eun Hong, Hillary Bundick, John Weiss, and Sanjay Gami for their help with data collection in the field and in the laboratory. We thank Peg Cook (Cooks Consulting) for help with field history data collection and cooperating producers Jake Ashline (Miner Institute), Darren McIntyre (Wyndamar Farms), Dave Fisher (Mapleview Dairy LCC), Dan Chambers (Chambers Farm LCC), Brian Chittenden (Dutch Hollow Farm LCC), Martha and Richard Place (Hohl Acres), Neil and Greg Rejman (Sunnyside Farm, Inc), and Bill Kilcer (Winnstott Farm) for working with us on the trials and donating time and equipment to the project. This project was funded by grants from the New York Farm Viability Institute (NYFVI), Northern New York Agricultural Development Program (NNYADP), in-kind contributions by Cornell Cooperative Extension, the College of Agriculture and Life Science, the consultants and the farmers.

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