Variability in Corn Yield Response to Nitrogen Fertilizer in Eastern ...

Published July 13, 2017

Soil Fertility & Crop Nutrition

Variability in Corn Yield Response to Nitrogen Fertilizer in Eastern Canada Lucie A. Kablan,* Valérie Chabot, Alexandre Mailloux, Marie-Ève Bouchard, Daniel Fontaine, and Tom Bruulsema ABSTRACT Corn (Zea mays L.) yield response to N has been found to vary spatially within a field. The objective of this study was to examine how grain corn yield response to N varies with planting date, soil texture, and spring weather across sites and years in the Montérégie region. Trials were conducted from 2002 to 2004 and 2006 to 2010, at 11 sites with 23 hybrids and four N application rates, for a total of 45 site-years. Each site-year involved five or six N rates ranging from 80–90 to 240 kg N ha–1. Grain yield response to N rates varied among site-years. Trials were separated into two groups based on optimal and late planting dates. Significant differences in grain yield among the applied N rates were observed in all of the site-years planted at optimal dates (from 8.8–14.7 Mg ha–1), and in most of those planted late (8.5–12.8 Mg ha–1). Economic optimum nitrogen rates (EONR) ranged less widely for site-years planted on optimal dates (180–237 kg N ha–1) than for those planted late (132–237 kg N ha–1). The EONR was affected by soil textural classes and rainfall. On coarse-textured soils, more N was needed to optimize grain yield in years with wet growing seasons. These results suggest that the current N recommendations for corn in Quebec should consider the variability in response associated with site-specific effects of planting date, soil texture, and weather.

Core Ideas

• A 8-yr study of corn N fertilization on high-yielding fields in Québec, eastern Canada. • Grain yield response to N rates varied among site-years. • The economically optimal N rate was affected by soil textural classes, planting date, and rainfall. • Averaged across textures, planting date, and weather, economically optimal N rate was 195 kg N ha–1. • Nitrogen applications at rates above the current N recommendation increased grain yield.

Published in Agron. J. 109:2231–2242 (2017) doi:10.2134/agronj2016.09.0511 Available freely online through the author-supported open access option Copyright (c) 2017 American Society of Agronomy 5585 Guilford Road, Madison, WI 53711 USA This is an open access article distributed under the CC BY license (https://creativecommons.org/licenses/by/4.0/)

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ontérégie is an agricultural region located in the southwestern portion of the St. Lawrence lowlands. It is one of the most important corn-producing areas in Quebec, accounting for 64% of provincial corn land area and 69% of the total amount of corn produced in the province (La financière agricole du Québec, 2015). In 2015, the average yield of corn fields in Montérégie was 11 Mg ha–1, vs. the provincial average yield of 10 Mg ha–1 (Institut de la statistique du Québec, 2015). The typical crop rotation in the region is corn– soybean. The average number of corn heat units (CHU, Bootsma et al., 2005) for this region is from 2800 to 3300 CHU. Timely planting is critical for maximizing grain corn yield. Coulter et al. (2010) demonstrated that planting dates between 21 April and 6 May in southwestern Minnesota resulted in high grain corn yield. However, when planting was delayed until 30 May, yield was only 80% of the maximum. In Canada, Fairey (1983) documented maturity and yield advantage of corn planted between late April and mid-May. This advantage is explained by the fact that the crop is able to utilize the full growing season. Nitrogen fertilization is a key component to corn production (Ruiz Diaz et al., 2008), since it often plays a major role in attaining high grain corn yield (Derby et al., 2005). Nitrogen fertilizer rates needed for corn vary largely among fields and also within fields (Scharf et al., 2002), due to variations in crop uptake demand, soil N supply, and losses from the soil. Identifying the EONR is very important in high N-demanding crops such as corn, to maximize profitability and to reduce N losses to the environment (Wang et al., 2003; Kyveryga et al., 2009). Nitrogen rate recommendations for a given field have been traditionally linked to their historical yield levels (Camberato, 2012). In fact, expected grain yield has been used as the primary independent variable for determining N fertilizer recommendations for corn (Gehl et al., 2005). However, EONR is variable and depends on many other factors, including weather conditions and crop management (Coulter and Nafziger, 2008; Nyiraneza et al., 2010), and genetics, soil landscape position, and their dynamic interactions (Tsai et al., 1992; Sogbedji et al., 2001; Miao et al., 2006). The wide range in optimum N L.A. Kablan, V. Chabot, A. Mailloux, M.E. Bouchard, and D. Fontaine, Research and Development, Crop Production Sector, La Coop Fédérée, Saint-Hyacinthe, QC J2T 5J4, Canada; T. Bruulsema, International Plant Nutrition Institute, Guelph, ON N1G 1L8, Canada. Received 13 Sept. 2016. Accepted 14 May 2017. *Corresponding author ([email protected]). Abbreviations: AWDR, abundant well-distributed rainfall; CHU, corn heat unit; EONR, economically optimal nitrogen rate; SDI, Shannon diversity index.

A g ro n o my J o u r n a l • Vo l u m e 10 9, I s s u e 5 • 2 017

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rates observed across corn experiments (213 site-years) in the United States suggests the need to adjust N rates by year and location (Dhital and Raun, 2016). Soil texture is another important factor that influences EONR. In a study conducted in Québec, Ziadi et al. (2013) demonstrated that EONR was higher in clay soil than in fine sandy loam soils. The average EONR across years was 181, 161, and 125 kg N ha–1 for clay, clay loam, and fine sandy loam soils, respectively. Furthermore, Chivenge et al. (2011) showed that N response was higher in clay soils than in loam or sandy soils. Tremblay et al. (2012) also showed that corn response to added N was significantly greater in fine-textured soils than in medium-textured ones. These authors demonstrated that abundant and well-distributed rainfall (AWDR) enhanced N response. Under conditions of high air temperatures during the period from 30 d before to 10 d after side-dressing, responses to applied N were found to be higher for fine-textured soils when seasonal rainfall is abundant and well-distributed throughout the season (high AWDR). Tremblay et al. (2012) concluded that taking into account rainfall pattern and soil texture to determine optimal N rates could lead to improved crop profitability and reduced environmental impacts. The impact of these factors, however, has not been documented specifically for the Montérégie region. There is a need to refine N recommendations compared to the current standard N recommendation (170 kg ha–1, CRAAQ, 2003), and to develop specific recommendations for different soil types in this region. The objective of this study was therefore to examine how grain corn yield response to N varied according to date of planting, soil texture, and rainfall across years and sites in Montérégie region. MATERIALS AND METHODS Site Description Field experiments were conducted from 2002 to 2004 and 2006 to 2010, on high-yielding fields located at La Coop Research farm in Saint-Hyacinthe and farmers’ fields, for a total of 11 sites. All fields were located within a 10-km radius (45°35¢33²–45°40¢42², 72°50¢53²–72°56¢5²). At the beginning of the experiment, soil texture was analyzed at each site with a composite of surface soil (0–15 cm) using the Bouyoucos hydrometer modified method with soil sedimentation after the addition of a dispersing agent (Bouyoucos, 1962). Soil textures were grouped into three categories based on clay content, using the approach of Ziadi et al. (2013). When the clay content was ≤200 g kg–1 the soil was referred to as fine sandy loam; when the clay content was >200 g kg–1 but ≤400 g kg–1 the soil was referred to as clay loam; and when the clay content was >400 g kg–1, the soil was referred to as clay (Table 1). Four fields with soils mostly of clay textural class were located on the research farm. Two fields with clay soils, three fields with fine sandy loam and two fields with loam textural class were located on farmers’ land and managed by the research farm. Because of the limited size of the sample and based on the approach of Tonitto et al. (2006), clay and clay loam were grouped in a fine-textured soil category and fine sandy loam was considered as coarse texture. A total of 45 site-years were managed, five in 2002, 14 in 2003, three in 2004, nine in 2006, six in 2007, four in 2008, and two in both 2009 and 2010. 2232

Crop Management and Fertility Fields that had not received any manure applications the previous 5 yr and worked with annual fall moldboard plow tillage were retained. Crop management details for each site including hybrids used, required CHUs for each hybrid, planting dates and previous crops are presented in Table 2. The N treatments applied are described in Table 3. Starter fertilizer applications were banded at planting, including 40 to 50 kg N ha–1 as ammonium nitrate, and P and K fertilizers according to the soil test, as per CRAAQ recommendations (CRAAQ, 2003). The rest of the N fertilizer for each N treatment was either broadcast and incorporated before planting corn, or applied as urea ammonium nitrate (32%N) (UAN) at sidedress and injected at 5 cm when corn was at V3 to V5 growth stage (Table 3). The experimental design at each site-year was a randomized complete block with four replications. Each experimental plot was four rows (3 m) wide and 7 m long. Trials consisting of multiple hybrids (Table 2) were planted in 76 cm row spacing with a seeding rate of 79,000 seed ha–1. Herbicides were used for weed control and applied before corn emergence or soon after emergence. Grain corn yield was determined by harvesting the two center rows from each plot after maturity. Yields were calculated on a basis of 155 g kg–1 moisture content. Rainfall Data and Related Parameters The monthly rainfall from May to September and the 30-yr average rainfall were recorded at the La Providence weather station, which is located within 10 km from the research farm (45°36¢59² N, 72°57¢15² W). Two rainfall parameters were retained for this study. May and June rainfall was considered for the site-years with N applied at pre-plant, while AWDR was considered for the site-years with N applied at sidedress (Tremblay et al., 2012). The AWDR was defined as: AWDR = PPT × SDI where PPT is the cumulative precipitation and SDI the precipitation evenness (Shannon diversity index). More details are presented in Tremblay et al. (2012). Data Analysis Since the period between late April and mid-May represents the optimum planting period for corn in this region (La financière agricole du Québec, 2015), the data were separated into two groups according to the planting dates. The first group contains trials with planting dates between late April and mid-May. The second group contains trials with planting dates after mid-May. Differences in grain yield among treatments were analyzed for all data using SPSS version 24. A two-way ANOVA was performed within each of the 45 site-yr. When the F test for the N fertilizer rate effect was significant (P < 0.05) for a site-year (37 of 45 site-years), five response models (Quadratic, Quadraticplateau, Mitscherlich, Linear-plateau, and Spherical plateau) were fit to data using the Crop Nutrient Response Tool V 4.5 (Bruulsema, 2015). Ultimately, the quadratic-plateau model was chosen for most of the site-years, since it showed the best fit to the data in these trials and in other response trials reported in the literature (Cerrato and Blackmer, 1990; Bélanger et al.,

Agronomy Journal • Volume 109, Issue 5 • 2017

Table 1. Description of study sites. Site ID

Year

Location

Sand† Silt Clay Organic matter ------------------------------------------------------------------------------------------------ g kg–1 ------------------------------------------------------------------------------------------------

pH

1

2002

Sainte-Rosalie 1

0

398

602

47

6.7

2

2002

Sainte-Rosalie 1

0

398

602

47

6.7

3

2002

Sainte-Rosalie 1

0

398

602

47

6.7

4

2002

Sainte-Rosalie 1

0

398

602

47

6.7

5

2002

Sainte-Rosalie 1

0

398

602

47

6.7

6

2003

Sainte-Rosalie 2

167

315

518

37

6.0

7

2003

Sainte-Rosalie 2

167

315

518

37

6.0

8

2003

Sainte-Rosalie 2

167

315

518

37

6.0

9

2003

Sainte-Rosalie 2

167

315

518

37

6.0

10

2003

Sainte-Rosalie 2

167

315

518

37

6.0

11

2003

Sainte-Rosalie 2

167

315

518

37

6.0

12

2003

Sainte-Rosalie 2

167

315

518

37

6.0

13

2003

Sainte-Rosalie 2

167

315

518

37

6.0

14

2003

Sainte-Rosalie 2

167

315

518

37

6.0

15

2003

Sainte-Rosalie 2

167

315

518

37

6.0

16

2003

Sainte-Rosalie 2

167

315

518

37

6.0

17

2003

Sainte-Rosalie 2

167

315

518

37

6.0

18

2003

Sainte-Rosalie 2

167

315

518

37

6.0

19

2003

Sainte-Rosalie 2

167

315

518

37

6.0

20

2004

Sainte-Rosalie 2

167

315

518

37

6.0

21

2004

Sainte-Rosalie 2

167

315

518

37

6.0

22

2004

Sainte-Rosalie 2

167

315

518

37

6.0

23

2006

Saint-Hyacinthe 1

340

170

490

35

7.5

24

2006

Saint-Hyacinthe 1

340

170

490

35

7.5

25

2006

Saint-Simon 2

640

200

160

30

6.2

26

2006

Saint-Simon 2

640

200

160

30

6.2

27

2006

Saint-Simon 2

640

200

160

30

6.2

28

2006

Saint-Simon 2

640

200

160

30

6.2

29

2006

Saint-Simon 2

640

200

160

30

6.2

30

2006

Saint-Hyacinthe 1

340

170

490

35

7.5

31

2006

Saint-Hyacinthe 1

340

170

490

35

7.5

32

2007

Saint-Hyacinthe 2B

170

290

540

30

6.4

33

2007

Saint-Hyacinthe 2B

170

290

540

30

6.4

34

2007

Saint-Simon 9B

734

120

146

30

7.1

35

2007

Saint-Simon 9B

734

120

146

30

7.1

36

2007

Saint-Hyacinthe 2B

170

290

540

30

6.4

37

2007

Saint-Simon 1

734

120

146

30

6.2

38

2008

Saint-Hyacinthe 4B

200

330

470

26

7.3

39

2008

Saint-Hyacinthe 4B

200

330

470

26

7.3

40

2008

Saint-Simon 2

554

200

246

25

6.6

41

2008

Saint-Simon 2

554

200

246

25

6.6

42

2009

Saint-Hyacinthe 8B

197

230

573

30

7.7

43

2009

Saint-Hyacinthe 8B

197

230

573

30

7.7

44

2010

Saint-Hyacinthe 4B

235

380

385

34

7.5

45

2010

Saint-Simon 10A

655

110

235

23

6.8

† Surface soil (0–15 cm) properties at the beginning of the experiment at 11 sites in Montéregie region.


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Table 2. Crop management information from 2002 to 2004 and 2006 to 2010. Site ID

Year

Cultivars

1

2002

Elite 85P57

Hybrid CHU†

Planting date

Previous crop

2800

25 May

Flax

2

2002

Elite 60T06

2600

25 May

Flax

3

2002

Elite N24-B9

2725

25 May

Flax

4

2002

Elite 70T40

2800

25 May

Flax

5

2002

Elite 67M78 LL

2650

25 May

Flax

6

2003

Elite 60T06

2600

31 May

Soybean

7

2003

Elite 60T06

2600

31 May

Soybean

8

2003

Elite 60T06

2600

31 May

Soybean

9

2003

Elite 60T06

2600

31 May

Soybean

10

2003

Elite 85P57

2800

22 May

Soybean

11

2003

Elite 60T06

2600

22 May

Soybean

12

2003

Elite 70T40

2800

22 May

Soybean

13

2003

Elite 67M78 LL

2650

22 May

Soybean

14

2003

Elite 60T06

2600

22 May

Soybean

15

2003

Elite 70T40

2800

22 May

Soybean

16

2003

N29A2

2800

22 May

Soybean

17

2003

N3030Bt

2850

22 May

Soybean

18

2003

N16N7

2600

22 May

Soybean

19

2003

N25J7

2700

22 May

Soybean

20

2004

Elite 85P57

2800

12 May

Soybean

21

2004

Elite 60T06

2600

12 May

Soybean

22

2004

Elite 70T40

2800

12 May

Soybean

23

2006

Elite 46T06

2300

2 June

Corn

24

2006

Elite 20T16

2400

2 June

Corn

25

2006

Elite 85P57

2800

31 May

Corn

26

2006

Elite 25T17 RR

2650

31 May

Corn

27

2006

Elite 44S22 RR

2900

31 May

Corn

28

2006

N25J7

2700

31 May

Corn

29

2006

N23F7

2675

31 May

Corn

30

2006

N16M1

2600

2 June

Corn

31

2006

N16N7

2600

2 June

Corn

32

2007

N23F7

2675

6 May

Corn

33

2007

N33E1

2850

6 May

Corn

34

2007

N23F7

2675

9 May

Corn

35

2007

N33E1

2850

9 May

Corn

36

2007

Elite 25T18RR

2700

6 May

Corn

37

2007

Elite 25T18RR

2700

9 May

Corn

38

2008

Elite 25T19RR

2600

2 May

Wheat

39

2008

Elite 15W19RR

2850

2 May

Wheat

40

2008

Elite 25T19RR

2600

11 May

Wheat

41

2008

Elite 15W19RR

2850

11 May

Wheat

42

2009

Elite 25T19RR

2600

27 April

Corn

43

2009

Elite 15W19RR

2850

27 April

Corn

44

2010

Elite 19A30RR

2700

5 May

Wheat

45

2010

Elite 19A30RR

2700

5 May

Corn

† CHU, Corn heat units for each hybrid.

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Table 3. Nitrogen rate at planting and N rate at pre-plant or at sidedress, for N response trials (2002–2004, 2006–2010). At-planting N Additional N N Source for Timing of Application Site ID Year (Ammonitrate) with variable rates variable rates† variable rates date –1 ------------------------------------------------------- kg ha ------------------------------------------------------1

2002

50

30, 70, 110, 150, 190

UAN

Sidedress

2 July

2

2002

50

30, 70, 110, 150, 190

UAN

Sidedress

2 July

3

2002

50

30, 70, 110, 150, 190

UAN

Sidedress

2 July

4

2002

50

30, 70, 110, 150, 190

UAN

Sidedress

2 July

5

2002

50

30, 70, 110, 150, 190

UAN

Sidedress

2 July

6

2003

50

30, 70, 110, 150, 190

Ammonitrate

Sidedress

27 June

7

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

27 June

8

2003

50

30, 70, 110, 150, 190

Urea

Sidedress

27 June

9

2003

50

30, 70, 110, 150, 190

Urea + Agrotain

Sidedress

27 June

10

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

11

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

12

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

13

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

14

2003

50

30, 70, 110, 150, 190

Urea

Pre-plant

9 May

15

2003

50

30, 70, 110, 150, 190

Urea

Pre-plant

9 May

16

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

17

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

18

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

19

2003

50

30, 70, 110, 150, 190

UAN

Sidedress

20 June

20

2004

40

40, 80, 120, 160, 200

Urea

Preplant

12 May

21

2004

40

40, 80, 120, 160, 200

Urea

Pre-plant

12 May

22

2004

40

40, 80, 120, 160, 200

Urea

Pre-plant

12 May

23

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

7 July

24

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

7 July

25

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

6 July

26

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

6 July

27

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

6 July

28

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

6 July

29

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

6 July

30

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

7 July

31

2006

40

40, 80, 120, 160, 200

UAN

Sidedress

7 July

32

2007

40

40, 80, 120, 160, 200

UAN

Sidedress

11 June

33

2007

40

40, 80, 120, 160, 200

UAN

Sidedress

11 June

34

2007

40

40, 80, 120, 160, 200

UAN

Sidedress

8 June

35

2007

40

40, 80, 120, 160, 200

UAN

Sidedress

8 June

36

2007

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

6 May

37

2007

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

6 May

38

2008

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

2 May

39

2008

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

2 May

40

2008

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

11 May

41

2008

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

11 May

42

2009

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

27 April

43

2009

40

50, 80, 110,140, 170, 200

ESN

Pre-plant

27 April

44

2010

50

40,70,100, 130, 160, 190

ESN

Pre-plant

5 May

45

2010

50

40,70,100, 130, 160, 190

ESN

Pre-plant

5 May

† UAN, urea-ammonium nitrate solution (32–0–0); ESN, environmentally smart nitrogen.


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2000; Mullen et al., 2010; Schmidt et al., 2011). The linear-plateau was used to estimate the EONR for 6 of 37 site-years, where it fit better than the quadratic-plateau. The quadratic-plateau model was defined by Eq. [1] and [2]: Y = A + BX + CX2 when X < B/–2C

[1]

otherwise Y = A + B2/–2C + B2/4C

[2]

where Y is the grain yield (kg ha–1) and X is the rate of N application (kg ha–1); A (intercept), B (initial slope), C (curvature). The linear-plateau model was defined by Eq. [3] and [4]: Y = A + BX when X < (C – A)/B

[3]

otherwise Y=C

[4]

where Y is the grain yield (kg ha–1) and X is the rate of N application (kg ha–1); A (intercept), B (slope), C (plateau yield, kg ha–1). The EONR is defined as the rate at which the last increment of added N generated a yield equal in value to that of the added N (Deen et al., 2015). The EONR was calculated by taking into account the price ratio between fertilizer (1.20 CAN$ kg–1 of N) and corn (0.23 $ kg–1). A descriptive statistics analysis was calculated where EONR was considered a dependent variable, and independent variables were soil texture, planting date, and rainfall. The relationship between these parameters was also evaluated using subgroup combinations.

RESULTS AND DISCUSSION Planting Date, Corn Yield Response, and Economically Optimal Nitrogen Rate As weather permitted, 17 site-years were planted between late April and mid-May and 28 site-years were planted after mid-May (Table 2). In 2004 and from 2007 to 2010, corn was planted during the optimal planting window in Montérégie, between 27 April and 12 May. Delayed corn planting from 22 May to 2 June was observed for the years 2002, 2003, and 2006. Grain yield response to increasing N rates varied across the site-years. A two-way ANOVA revealed that fertilizer N improved grain yield in all of the 17 site-years planted between late April and mid-May. Observed average grain yield for those site-years ranged from 8.8 to 14.7 Mg ha–1 (Table 4). The year 2008 showed the highest average yield (Site-year 39) and the lowest yield was observed in 2004 on Site 21. Considering the site-years where corn was planted after mid-May, a significant effect of fertilizer N was observed on 20 out of 28 site-years (Table 5). Average grain yield ranged from 8.5 to 12.8 Mg ha–1. The highest average yield was observed on the Site-year 17 in 2003, and the lowest yield was observed in 2002 on the Site-year 5. Site-years planted between late April and mid-May yielded higher than site-years planted after mid-May (11.4 compared to 10.3 Mg ha–1). This is consistent with the results of Lauer et al. (1999) who reported that grain corn yields decreased with later planting date. In our study, the increase in yield between the two groups of site-years could be explained by the planting date (Mullen et al., 2010), but other parameters such as soil types, hybrids and weather conditions may be involved (Almaraz et al., 2008; Ziadi et al., 2013; Tremblay et al., 2012; Woli et al., 2016).

Table 4. Corn N response parameters at the 17 site-years planted before 15 May. Planting Analysis of Site ID Year date variance Mean yield CV a‡ b kg ha–1 Mg ha–1 20 2004 12 May ** 10.5 9 4236 67.0509 21 2004 12 May * 8.8 15 3346 52.5458 22 2004 12 May ** 9.2 13 3510 53.7263 32 2007 6 May ** 10.8 4 4545 71.8024 33 2007 6 May ** 11.6 4 4722 74.8055 34 2007 9 May ** 11.0 6 4278 71.4880 35 2007 9 May ** 11.6 3 4360 72.0051 36 2007 6 May ** 10.2 4 4180 63.6820 37 2007 9 May * 10.1 6 4166 59.2368 38 2008 2 May ** 13.5 3 9400 37.8853 39 2008 2 May ** 14.7 2 10622 38.2393 40 2008 11 May ** 12.7 4 5103 74.7482 41 2008 11 May ** 13.8 3 6077 81.7936 42 2009 27 Apr. ** 10.8 5 3711 46.2418 43 2009 27 Apr. ** 11.3 5 4631 41.0399 44 2010 5 May ** 12.3 3 7231 54.0134 45 2010 5 May ** 10.6 8 5098 35.4099

c –0.152 –0.102 –0.101 –0.183 –0.175 –0.163 –0.147 –0.151 –0.130 –0.072 –0.076 –0.157 –0.192 12429 13983 –0.130 11959

R2 0.90 0.96 0.98 0.999 0.96 0.94 0.97 0.94 0.996 0.98 0.95 0.98 0,93 0.94 0.98 0.99 0.99

EONR† kg ha–1 200 227 237 180 196 201 225 190 205 222 213 219 197 189 228 185 194

Yield at EONR Mg ha–1 11.6 10.0 10.6 11.6 12.7 12.1 13.1 10.8 10.9 14.3 15.3 14.0 14.7 12.4 14.0 12.8 12.0

* Significant at the 0.05 probability level. ** Significant at the 0.01 probability level. † EONR, economic optimum nitrogen rate. For Site-years 42, 43, and 45, EONR was estimated with the linear-plateau model because the quadraticplateau did not fit. ‡ a, b, c represent the intercept, initial slope, and curvature, respectively, for quadratic-plateau and intercept, slope, and maximum yield for linear plateau.

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The EONR for the site-years planted before mid-May ranged from 180 to 237 kg N ha–1 (Table 4). All of the EONR were greater than the current N recommendation for the province of Quebec (170 kg N ha–1; CRAAQ, 2003) (Fig. 1a). Considering the site-years planted after mid-May, the EONR ranged from 132 to 237 kg N ha–1 (Table 5). Nine site-years had EONRs lower than the current N fertilizer recommendation for corn in Quebec (170 kg N ha–1; CRAAQ, 2003), which represented 45% of the sites, whereas 11 site-years (55%) showed EONR values above the Quebec recommendation (Fig. 1b). All of the EONRs of site-years planted on optimum dates were higher than the provincial current N recommendation of 170 kg N ha–1 compared to 55% of the site-years planted later than 15 May. This suggests that an optimum planting date tends to increase EONR. Knapp and Reid (1981) and Mullen et al. (2010) have reported that late-planted corn (late May–early June) in New York had lower grain yields and lower N fertilizer requirements than corn planted in late April/early May. The increase in EONR above the current provincial N recommendation also means that the average yield potential for this group of site-years

exceeds the provincial average for which the current recommendations were developed by CRAAQ. Our study therefore suggests that there is a tendency for fields with high yield potential in the Montérégie region to require N fertilization above the regional recommendation to achieve their full yield potential. Nyiraneza et al. (2010) studied the soil and crop parameters related to corn N response in Quebec and found that EONR values ranged from 73 to 235 kg N ha–1 in 2007 and from 48 to 200 kg N ha–1 in 2008. In their study, 46 and 29% of the site-years had EONRs greater than the current provincial N recommendation in 2007 and 2008, respectively. The wider range of EONR obtained by these authors is probably due to the fact that this study was done over many regions (7) in Québec with different climate conditions, with CHU from 2000 to 3000. This represents more widely varying conditions and fields with different yield potential than are prevalent in the Montérégie region. In our study, all of the sites had narrower CHU varying, from 2873 to 3383. Only high yield potential fields were used (from 8.5 to 14.7 Mg ha–1), vs. average provincial yields ranging from 7.5 to 9.3 Mg ha–1 for the 2002 to 2010 period (Institut de la statistique du Québec, 2015).

Table 5. Corn N response parameters at the 28 site-years planted after 15 May. Planting Analysis Site ID Year date of variance Mean yield CV a‡ kg ha–1 Mg ha–1 1 2002 25 May ** 10.1 6 3747 2 2002 25 May ns§ 8.8 16 3 2002 25 May * 9.0 8 2934 4 2002 25 May * 9.6 6 4681 5 2002 25 May ns 8.5 11 6 2003 31 May ** 9.0 4 4085 7 2003 31 May ns 9.1 7 8 2003 31 May ns 9.0 4 9 2003 31 May * 8.9 4 4112 10 2003 22 May ** 12.0 4 5402 11 2003 22 May * 9.9 8 4040 12 2003 22 May * 10.4 6 8356 13 2003 22 May ** 10.0 4 4783 14 2003 22 May ** 10.1 7 9068 15 2003 22 May ** 10.4 4 9207 16 2003 22 May ** 12.5 5 5613 17 2003 22 May ns 12.8 3 18 2003 22 May ** 10.6 6 6511 19 2003 22 May ns 11.4 8 23 2006 2 June ** 9.8 2 7128 24 2006 2 June ** 9.3 4 4864 25 2006 31 May ns 11.7 9 26 2006 31 May * 11.5 6 4250 27 2006 31 May ** 11.9 5 4268 28 2006 31 May ** 11.3 8 4027 29 2006 31 May ** 11.4 8 3945 30 2006 2 June ns 9.1 4 31 2006 2 June * 8.6 2 3707

Yield at EONR Mg ha–1 11.5

b

c

R2

60.3604

–0.116

0.91

57.0811 43.3713

–0.128 –0.080

0.88 0.98

199 233

9.2 10.4

71.0380

–0.242

0.92

134

9.5

68.3378 83.2500 72.0991 12.8225 53.2796 12.4721 9.1150 83.2500

–0.232 –0.244 –0.203 11398 –0.114 –0.019 11279 –0.230

0.98 0.93 0.91 0.97 0.98 0.65 0.97 0.99

134 159 162 237 208 166 227 168

9.1 12.5 10.4 11.4 10.9 10.6 11.3 13.1

39.7107

–0.077

0.94

218

11.5

29.6961 57.7814

–0.072 –0.177

0.98 0.89

165 146

10.1 9.5

75.0421 82.2205 51.4844 77.0085

–0.163 –0.191 13054 –0.168

0.93 0.84 0.98 0.88

212 199 175 211

12.8 13.1 13.1 12.7

70.8026

–0.245

0.70

132

8.8

EONR† kg ha–1 234

* Significant at the 0.05 probability level. ** Significant at the 0.01 probability level. † EONR, Economic optimum nitrogen rate. For the site-years 12, 15, and 28, EONR was estimated with the linear- plateau model because the quadratic-plateau did not fit. ‡ a, b, c represent the intercept, initial slope, and curvature, respectively, for quadratic-plateau and intercept, slope, and maximum yield for linear-plateau. § ns, not significant.


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Fig. 1. The frequency distribution of economically optimal N rate for (A) planting date between late April and mid-May (17 site-years) and (B) late-planted corn (20 site-years).

Table 6. Relationship between economic optimum nitrogen rate (EONR) and soil texture. Soil Year texture No.† EONR‡ Min. Max. kg ha–1 2002 Fine 3 222 ± 19.9 199 234 2003 Fine 10 181 ± 38 134 234 2004 Fine 3 221 ± 19.1 200 237 2006 Fine 3 147 ± 16.1 132 165 2006 Coarse 4 199 ± 17.2 175 212 2007 Fine 3 189 ± 8.1 180 196 2007 Coarse 3 210 ± 12.7 201 225 2008 Fine 4 213 ± 11.1 197 222 2009 Fine 2 208 ± 28.2 188 228 2010 Fine 2 190 ± 6.4 185 194 Total Fine 30 193 ± 32.7 132 237 Coarse 7 204 ± 15.4 175 225 Total 37 195 ± 30.3 132 237 † No., number of site-years for each soil texture. ‡ Mean ± standard deviation. Range or confidence intervals for EONR were estimated with a descriptive statistics analysis.

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Estimated grain yield at EONR in this study ranged from 10.0 to 15.3 Mg ha–1 for corn planted between late April and mid-May and from 8.8 to 13.1 Mg ha–1 after mid-May. The highest grain yield at EONR (15.3 Mg ha–1) was obtained with 213 kg N ha–1 on corn planted before mid-May. After mid-May, the highest yield at EONR (13.1 Mg ha–1) was reached with 168, 175, and 199 kg N ha–1 (three sites). Corn planted between late April and mid-May was more responsive to N than corn planted after midMay. Mullen et al. (2010) studied corn response to fertilizer N in a 2-yr study, as affected by planting date and hybrid. They observed that in 1 of the 2 yr, corn planted in early May was more responsive to applied N than corn planted in early June. A similar observation was also reported by Eckert and Martin (1994), indicating that delayed planting reduced yield in each site-year, and almost always reduced the quantity of N required to obtain optimum yield. Late planting can decrease the EONR, but the year-to-year variability in N demand cannot be ignored (Mullen et al., 2010). Economically Optimal Nitrogen Rate as Affected by Soil Textural Class Most site-years (N = 30) were located on fine-textured soils with some on coarse-textured soils (N = 7) (Table 6). The EONR of fine-textured soils varied across the years with a minimum and Agronomy Journal • Volume 109, Issue 5 • 2017

maximum of 132 and 237 kg N ha–1, respectively. For coarsetextured soils, the minimum and maximum EONR were 175 and 225 kg N ha–1, respectively. Fine-textured soils sometimes have lower N requirements than coarse-textured soils and Quebec fertilizer recommendations reflect this. However, other reports from Canada have found that the opposite occurs (Tremblay et al., 2012; Ziadi et al., 2013). Although both soil texture and planting date influence EONR, few reports have examined both effects together. Table 7 shows the effects of soil texture and planting date classes on EONR. For both soil texture categories, the EONR tended to be lower for late planting than early planting. In fine-textured soils, early planting

required an additional 22 kg N ha–1 to obtain optimum yield compared to late planting. These findings corroborate those of Eckert and Martin (1994), who demonstrated that N needed to achieve maximum yield varied from 0 to 205 kg N ha–1 for early planted corn, and from 0 to 175 kg N ha–1 for late-planted corn. This could be explained by the fact that delayed planting reduces the corn capacity to respond to greater N rates. Mullen et al. (2010) hypothesized that late-planted corn requires less N because the soil was significantly warmer when the corn plant was at early growth stages and the mineralization of organic matter at that time decreased the need for N supplementation.

Table 7. Relationship between economic optimum nitrogen rate (EONR), planting date, soil texture, and rainfall. Yield at Subgroup† No.‡ EONR§ Min. Max. EONR Mg ha–1 kg ha–1 All planting dates, all textures and all weather 37 195 ± 30.3 132 237 11.8 ± 1.7 Subgroup for planting date Early 17 206 ± 17.3 180 237 12.7 ± 1.6 Late 20 186 ± 35.9 132 237 11.1 ± 1.5 Subgroup for texture Fine texture 30 193 ± 33.6 132 237 11.6 ± 1.8 Coarse texture 7 204 ± 15.4 175 225 12.6 ± 0.9 Subgroup for combined texture and planting date Fine texture, early planting 14 205 ± 18.4 180 237 12.8 ± 1.7 Fine texture , late planting 16 183 ± 38.9 132 237 10.6 ± 1.3 Coarse texture, early planting 3 210 ± 12.9 201 225 12.0 ± 1.1 Coarse texture , late planting 4 199 ± 17.2 175 212 13.0 ± 0.4 Subgroup for combined texture and rainfall Fine texture, High May + June rainfall 8 206 ± 16.7 185 228 14.0 ± 1.0 Fine texture , Low May +June rainfall 6 207 ± 27.3 166 237 10.9 ± 0.6 Fine texture , High AWDR 5 164 ± 25.6 132 196 10.5 ± 1.6 Fine texture , Low AWDR 11 190 ± 39.6 134 237 10.8 ± 1.3 Coarse texture , High May + June rainfall 0 – – Coarse texture , Low May + June rainfall 1 – – Coarse texture , High AWDR 6 204 ± 16.9 175 225 12.9 ± 0.5 Coarse texture , Low AWDR 0 – – Subgroup for combined planting date, soil texture and rainfall Early planting, fine texture, High May + June rainfall 8 206 ± 17.0 185 228 14.0 ± 1.0 Early planting, fine texture, Low May + June rainfall 4 214 ± 22.1 190 237 10.8 ± 0.7 Early planting, fine texture, High AWDR 2 188 ± 11.3 180 196 12.2 ± 0.8 Early planting, coarse texture , High May + June rainfall 0 – – – – Early planting, coarse texture , Low May + June rainfall 1 – – – – Early planting, coarse texture, High AWDR 2 213 ± 17.0 201 225 12.6 ± 0.7 Late planting, fine texture, Low May + June rainfall 2 197 ± 43.1 166 227 11.1 ± 0.6 Late planting,fine texture, High AWDR 3 148 ± 16.6 132 165 9.5 ± 0.6 Late planting, fine texture, Low AWDR 11 190 ± 39.6 134 237 10.8 ± 1.3 Late planting, coarse texture, High AWDR 4 199 ± 17.2 175 212 13.0 ± 0.4 Subgroup for combined planting date, timing of N fertilization and rainfall Early planting, pre-plant, High May + June rainfall 8 206 ± 16.7 185 228 14.0 ± 1.0 Early planting, pre-plant, Low May + June rainfall 5 212 ± 19.5 190 237 10.8 ± 0.6 Early planting, sidedress, High AWDR 4 201 ± 18.6 180 225 12.4 ± 0.7 Late planting, pre-plant, Low May + June rainfall 2 197 ± 43.1 166 227 11.1 ± 0.6 Late planting, sidedress, High AWDR 7 177 ± 31.6 132 212 11.5 ± 2.0 Late planting, sidedress, Low AWDR 11 190 ± 39.6 134 237 10.8 ± 1.3

Min.

Max.

8.8

15.3

10 8.8

15.3 13.5

8.8 10.9

15.3 13.5

10 8.8 10.9 12.7

15.3 13.1 13.1 13.5

12.5 10 8.8 9.1

15.3 11.6 12.7 13.1

12.1

13.5

12.5 10 11.6 – – 12.1 10.6 8.8 9.1 12.7

15.3 11.6 12.7 – – 13.1 11.5 10.1 13.1 13.5

12.5 10.0 11.6 10.6 8.8 9.1

15.3 11.6 13.1 11.5 13.5 13.1

† AWDR, abundant well-distributed rainfall. ‡ No., number of site-years in each subgroup. § Mean ± standard deviation. Range or confidence intervals for EONR were estimated with a descriptive statistics analysis.


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Table 8. Monthly growing season precipitation. Year May June July Aug. Sept. Total ---------------------------------------------------------------------------------------- mm ---------------------------------------------------------------------------------------2002 153 92 56 44 98 443 2003 94 56 102 129 76 457 2004 78 73 263 69 69 552 2006 208 132 89 161 76 666 2007 72 58 123 98 100 451 2008 79 88 142 178 74 561 2009 123 112 139 71 64 510 2010 33 161 117 76 104 491 30 yr† 84 95 102 100 84 465 † 30 yr (1984–2014) based on La Providence weather station (45°36¢59² N, 72°57¢15² W).

For late-planted corn, EONR was slightly lower on finetextured soils (183 kg N ha–1) compared to coarse-textured soils (199 kg N ha–1). In an optimal planting window, both textural classes presented similar EONR, which is greater than provincial recommendations from CRAAQ. This result suggests that in the optimal window, additional N is needed to optimize corn grain yield on both fine- and coarse-textured soils. These results contrast those of Tremblay et al. (2012), who reported that corn is more responsive to N fertilization in clayey soils. Sogbedji et al. (2001) observed that EONRs were minimally affected by field variability from drainage class, but strongly affected by annual fluctuations as a result of varying early season weather. Economical Optimal Nitrogen Rate as Impacted by Interaction of Planting Date, Rainfall, and Soil Texture It has been reported that rainfall amounts observed in May right before N fertilizer applications and in June just after N applications are the most interesting, because fertilizer nitrate content is subject to mobilization by water (Kyveryga et al., 2011). Another reason for interest is the fact that the few days before and right after the N application, rainfall has a positive effect on N response (Herlihy and O’keeffe, 1987; Tremblay et al., 2012). May and June rainfall was also used because of pre-plant treatments. May and June 2009 were considerably wetter (236 mm) than normal, while the years 2004 and 2007 were drier than normal for these 2 mo (151 and 130 mm, respectively) (Table 8). The 2010 growing season accumulated the least precipitation in May. Rainfall in June 2009 and 2010 Table 9. Shannon diversity index (SDI) and abundant well-distributed rainfall for site-years receiving sidedress N applications. Site-year Year SDI AWDR‡ groups† mm i 2002 0.57 56 ii 2003 0.64 84 iii 2003 0.60 56 iv 2006 0.69 151 v 2007 0.76 118 † (i) Site-years 1, 3, and 4; (ii) Site-years 6, 8, and 9; (iii) Site-years 10, 11, 12 13, 16, and 18; (iv) Site-years 23, 24, 26, 27, 28, 29, 30, and 31; (v) Site-years 32, 33, 34, and 35. ‡ AWDR, abundant well-distributed rainfall.

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exceeded the long-term average. Since the N application in 2002, 2003, and 2006 was done late, between 20 June and 7 July, and most of the sites received a sidedress application, we have considered the AWDR index to better evaluate the effect of rainfall on applied fertilizers. The SDI varied from 0.57 to 0.76 and AWDR ranged from 56 to 151 mm (Table 9). In years 2002 and 2003, sites experienced suboptimal rainfall, with AWDR varying from 56 to 84 mm. The highest AWDR was observed in 2006. In fine-textured soils, the EONR with high rainfall in May and June (206 kg N ha–1) was similar to low rainfall at the same period (207 kg N ha–1), and was lower for high AWDR (164 kg N ha–1) than for low AWDR (190 kg N ha–1) (Table 7). The impact of planting date category along with soil texture and rainfall were also assessed. The early planting/fine texture/ May + June rainfall subgroup showed a similar EONR for high and low rainfall (206 and 214 kg N ha–1, respectively). These results contrast those of Tremblay (2004), who reported that dry years are characterized by a poor response to N fertilization, with a greater response observed in wet years. van Es et al. (2005) also demonstrated that N response was greater in finer-textured soils in years with wet springs. Frequent rain situations tend to promote soil moisture, which increases the likelihood of leaching or denitrification, and therefore increases crop response to N fertilization. However, high May + June rainfall increased yield by a factor of 1.3. When corn was planted late on fine-textured soils, high AWDR gave lower EONR (148 kg N ha–1) than low AWDR (190 kg N ha–1). Our data suggest that AWDR classes have an inverse effect on finetextured soils (i.e., high AWDR gives a lower EONR than low AWDR). Subgroups for combined planting date, timing of N fertilization, and rainfall showed that in the optimal planting window with pre-plant application, no difference was found between high and low rainfall (Table 7). However, yield at EONR was 30% higher with high May + June rainfall. For late planting EONR was slightly higher for low AWDR than for high AWDR with sidedressing. During wet growing seasons, the EONR for sidedressed corn was raised by 24 kg ha–1 for early planting vs. late planting. This analysis indicated that soil texture, planting date, and precipitation affected the EONR. During wet spring, responses to N fertilizer were more pronounced for sidedress application on coarse-textured soils over fine ones. In years where corn was planted late, N response was also greater in coarse-textured soil with high rainfall. This suggests that on coarse-textured soil, Agronomy Journal • Volume 109, Issue 5 • 2017

additional N is needed to optimize grain yield in years with wet growing season due to considerable losses from leaching. It has been reported that sandy soils are the most vulnerable to nitrate loss, with large losses occurring primarily from leaching. Our findings confirmed those of Scharf (2015), who reported that fertilizer N loss is usually irregular during wet weather and results in a high optimal N rate. Other studies have demonstrated that corn yield response to fertilizer N in North America appears to be affected by the total precipitation during June and July and temperatures during July and August (Bondavalli et al., 1970; Jeutong et al., 2000). In the Montérégie region, Almaraz et al. (2008) demonstrated that May precipitation and July temperature were strongly associated with yield variability in corn fields, and these climatic factors explained more than half of this variability. SUMMARY AND CONCLUSION In this 8-yr (45 site-years) study of corn N fertilization rates on high-yielding fields, it was observed that grain yields and EONR varied across site-years. Overall, optimal planting window increased grain corn yields compared to late planting. Averaged across textures, planting date, and weather, EONR was 195 kg N ha–1, which is above the current N recommendation for this region (170 kg N ha–1). The EONR was affected by soil textural classes, planting date and rainfall. The average EONR was 193 and 204 kg N ha–1 for fine-textured soil and coarse-textured soil, respectively. On coarse-textural soils, additional N was needed to optimize grain yield in years with wet growing seasons. However, same EONRs were obtained for early planting in fine-texture soils whatever spring rainfall. Response to fertilizer N was higher for early planted corn combined with wet conditions. The results from our study indicated that N rate guidelines may need to be increased for the optimal planting window, and should be based on soil texture and weather conditions. REFERENCES Almaraz, J.J., F. Mabood, X. Zhou, E.G. Gregorich, and D.L. Smith. 2008. Climate change, weather variability and corn yield at a higher latitude locale; southwestern Quebec. Clim. Change 88:187–197. doi:10.1007/s10584-008-9408-y Bélanger, G., J.R. Walsh, J.E. Richards, P.H. Milburn, and N. Ziadi. 2000. Comparison of three statistical models describing potato yield response to nitrogen fertilizer. Agron. J. 92:902–908. doi:10.2134/agronj2000.925902x Bondavalli, B., D. Clover, and E.M. Kroth. 1970. Effects of weather, nitrogen and population on corn yield response. Agron. J. 62:669–672. doi:10.2134/agronj1970.0002196200620005003 8x Bootsma, A., S. Gameda, and D.W. Mckenny. 2005. Potential impacts of climate change on corn, soybean and barley yields in Atlantic Canada. Can. J. Soil Sci. 85:345–357. doi:10.4141/S04-025 Bouyoucos, G.J. 1962. Hydrometer method improved for making particle size analysis of soil. Agron. J. 54:464–465. doi:10.2134/agr onj1962.00021962005400050028x Bruulsema, T.W. 2015. Crop nutrient response tool. Int. Plant Nutrition Inst., Guelph, ON. http://nane.ipni.net/article/NANE3068 (accessed 25 Feb. 2016).

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