Determination of a Critical Nitrogen Dilution Curve for Spring Wheat
ABSTRACT
Plant-based diagnostic tools of N deficiency can be based on the concept of critical N dilution curves describing whole-plant critical N concentration (Nc; g kg−1 of dry matter [DM]) as a function of shoot biomass (W; Mg DM ha−1). This has been tested for several crops, including winter wheat (Triticum aestivum L.) but has not been tested for spring wheat. Our objectives were to determine a critical N dilution curve specific to spring wheat, to compare this curve with existing critical N dilution curves for winter wheat, and to assess the plausibility of using it to estimate the level of N nutrition. The study was conducted at six site-years (2004–2006) in Québec, Canada, with four to eight N fertilization rates (0–200 kg N ha−1). Shoot biomass and N concentration were determined on five to eight sampling dates during the growing season, and grain yield was measured at harvest. A critical N dilution curve (Nc = 38.5 W−0.57) was determined for spring wheat and was different from those reported for winter wheat. The N nutrition index (NNI = Nobserved/Nc) calculated from this spring wheat critical N dilution curve was significantly related (R 2 = 0.70; P < 0.001) to relative grain yield. This critical N dilution curve and the resulting NNI adequately identified situations of limiting and nonlimiting N nutrition and could be used to establish the N nutrition status.
P
lant-based diagnostic methods of N deficiency could be used for an a priori diagnosis aimed at optimizing fertilizer N management to increase the economic crop return and minimize potentially negative effects on the environment. The a priori diagnosis of plant N status consists of early detection of plant N deficiency to determine the necessity of applying additional N fertilizer. Another application of plant-based diagnostic methods of N deficiency could be an a posteriori diagnosis aimed at detecting limiting factors for crops within experimental trials or fields in production. Plant-based diagnostic methods of N deficiency can be based on the definition of a critical N concentration (Nc); that is, the minimum N concentration required for maximum growth (Ulrich, 1952). The concept of a critical N dilution curve based on whole-plant N concentration was developed by Lemaire and Salette (1984) for tall fescue (Festuca arundinacea Schreb.) and is represented by an allometric function: Nc = aW−b
[1]
where W is the total shoot biomass expressed in Mg dry matter (DM) ha−1, Nc is the total N concentration in shoots expressed in N. Ziadi, G. Bélanger, A. Claessens, L. Lefebvre, A.N. Cambouris, and M.C. Nolin, Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada (AAFC), 2560 Hochelaga Blvd., Québec, QC, Canada G1V 2J3; N. Tremblay, Horticulture Research and Development Centre, AAFC, 430 Gouin Blvd., St-Jean-sur-Richelieu, QC, Canada J3B 3E6; L.-É. Parent, Département des sols et de génie agroalimentaire, Faculté des sciences de l’agriculture et de l’alimentation, Université Laval, Québec, QC, Canada G1V 0A6. Received 2 July 2009. *Corresponding author (
[email protected]). Published in Agron. J. 102:241–250 (2010) Published online 3 Dec. 2009 doi:10.2134/agronj2009.0266 Copyright © 2010 by the American Society of Agronomy, 677 South Segoe Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.
g kg−1 DM, and a and b are estimated parameters. The parameter a represents the N concentration in the total shoot biomass for 1 Mg DM ha−1, and the parameter b represents the coefficient of dilution describing the relationship between N concentration and shoot biomass. Greenwood et al. (1990) proposed two general relationships between Nc and shoot biomass: one for C3 species (a = 57.0 and b = 0.5) and one for C4 species (a = 41.0 and b = 0.5). Nevertheless, Lemaire and Gastal (1997) suggested that every species should have its own critical N dilution curve according to its histological and morphological characteristics. Species-specific critical N dilution curves have been determined for potato (Solanum tuberosum L.) (Greenwood et al., 1990; Duchenne et al., 1997; Bélanger et al., 2001), pea (Pisum sativum L.) (Ney et al., 1997), rice (Oryza sativa L.) (Sheehy et al., 1998), rapeseed (Brassica napus L.) (Colnenne et al., 1998), corn (Zea mays L.) (Plénet and Lemaire, 1999; Herrmann and Taube, 2004; Ziadi et al., 2008b), grain sorghum (Sorghum bicolor L.; van Oosterom et al., 2001), tomato (Lycopersicon esculentum Mill.) (Tei et al., 2002), annual ryegrass (Lolium multiflorum Lam.) (Marino et al., 2004), linseed (Linum usitatissimum L.) (Flénet et al., 2006), and cotton (Gossypium spp.) (Xiaoping et al., 2007). In winter wheat (Triticum aestivum L.), the parameters for this allometric function were estimated by Greenwood et al. (1990) (a = 38.6 and b = 0.33) from data obtained in Belgium and Sweden and by Justes et al. (1994) (a = 53.5 and b = 0.44) in France; the latter is widely recognized as the reference curve for wheat (Colnenne et al., 1998; Tei et al., 2002; Flénet et al., 2006; Xiaoping et al., 2007; Gislum and Boelt, 2009). During the early stages of growth, Nc takes a constant value due to the small decline of Nc with increasing shoot biomass and the lack of competition for light among isolated plants (Lemaire and Gastal, 1997). This value differs among species and was estimated at 44.0 g N kg−1 DM between 0 and 1.55 Mg DM ha−1 Abbreviations: DM, dry matter; Nc, critical nitrogen concentration; NNI, nitrogen nutrition index.
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Nitrogen Management
Noura Ziadi,* Gilles Bélanger, Annie Claessens, Louis Lefebvre, Athyna N. Cambouris, Nicolas Tremblay, Michel C. Nolin, and Léon-Étienne Parent
Table 1. Site characteristics and cropping practices. Lanoraie
2004 Ste.Victoire
2005 L’Acadie
Lanoraie
L’Acadie
2006 L’Acadie
Organic matter, % 2.04 4.27 2.23 2.68 3.38 2.40 pH (water) 5.9 6.4 6.8 5.9 7.2 6.5 Soil surface texture Clay content, %† 5 9 28 5 46 22 Silt content, %† 7 13 52 6 46 45 Sand content, %† 88 78 20 89 8 33 Soil classification‡ Typic Haplorthods Typic Humaquepts Typic Humaquepts Typic Humaquepts Typic Humaquepts Typic Humaquepts Precipitation, mm§ 550 595 439 817 630 675 Precipitation, 30-yr average, mm¶ 607 759 569 607 569 569 Temperature, °C# 16.0 17.4 18.6 17.2 19.1 19.2 Previous crop potato soybean soybean potato soybean wheat Seeding date 23 Apr 8 May 7 May 22 Apr. 9 May 10 May Fertilization†† Date 16 June 29 June 23 June 9 June 20 June 27 June Days after seeding 55 53 48 49 43 49 Harvesting date 10 Aug. 18 Aug. 17 Aug. 3 Aug. 10 Aug. 16 Aug. † Evaluated in the A horizon. ‡ Soil Survey Staff. 2006. Keys to soil taxonomy, 10th ed. USDA-Natural Resources Conservation Service, Washington DC. § Precipitation calculated from the seeding date to the harvesting date. ¶ Precipitation 30‑yr average from 1971 to 2000 (May–October). # Average temperature calculated from the seeding date to the harvesting date. †† Second N application after the application of 30 kg N ha –1 at planting.
in winter wheat cultivated in France (Justes et al., 1994) and at 57.0 g N kg−1 DM between 0 and 1.0 Mg DM ha−1 in C3 species (Greenwood et al., 1990). Spring wheat is widely grown in Canada mainly because winter wheat is highly susceptible to winter damage. However, a critical N dilution curve has never been determined for spring wheat. Although they are of the same species, winter and spring wheat differ morphologically, and it is unclear whether or not their critical N dilution curves are similar. Our objectives were: (i) to determine a critical N dilution curve specific to spring wheat, (ii) to compare this curve with existing critical N dilution curves for winter wheat, and (iii) to assess the plausibility of using this critical N dilution curve to estimate the level of N nutrition in spring wheat. Materials and Methods Site Description and Treatments A field experiment was conducted at six site-years in Québec, Canada: Lanoraie (45°57ʹN, 73°19ʹW) in 2004 and 2005; Ste. Victoire (45°55ʹN, 73°06ʹW) in 2004; and L’Acadie (45°17ʹN, 73°20ʹW) in 2004, 2005, and 2006. Site characteristics and cropping practices are presented in Table 1. The soil analysis methods used are reported in Ziadi et al. (2008a). Precipitation and temperature data were collected at three Environment Canada weather stations: at L’Assomption (45°48ʹN, 73°25ʹW) for the Lanoraie sites, at Fleury (45°48ʹN, 73°00ʹW) for the Ste. Victoire site, and at L’Acadie (45°17ʹN, 73°21ʹW) for the L’Acadie sites. The cultivar ‘AC Barrie’, a recommended spring milling wheat cultivar in Québec, was used at all sites. The planting and fertilization dates were site specific (Table 1). At Lanoraie and Ste. Victoire, eight N treatments were used: six split applications of 0, 40, 80, 120, 160, and 200 kg N ha−1, with 30 kg N ha−1 surface-broadcast at seeding and the rest at the elongation stage of development (except for the 0 kg N 242
ha−1 treatment); one conventional treatment consisting of a split application of 120 kg N ha−1, with 60 kg N ha−1 at seeding and 60 kg N ha−1 at the end of the tillering stage (referred to as 120c kg N ha−1); and one saturated treatment consisting of a single application of 120 kg N ha−1 at seeding (referred to as 120s kg N ha−1). At L’Acadie, four N treatments were used: split applications of 0, 30, 70, and 110 kg N ha−1 in 2004 and of 30, 60, 90, and 120 kg N ha−1 in 2005 and 2006, with 30 kg N ha−1 surface-broadcast at seeding and the rest at the elongation stage of development (except for the 0 kg N ha−1 treatment). Ammonium nitrate was used at seeding, whereas calcium ammonium nitrate was used for the second application of N fertilizer, which was surface broadcast by hand. At seeding, P and K fertilizers were applied according to soil analysis and local recommendations (Centre de référence en agriculture et agroalimentaire du Québec, 2003). Thus, 15 kg P ha−1 and 10 kg K ha−1 in 2004 and 22.5 kg P ha−1 and 22.5 kg K ha−1 in 2005 and 2006 were surface-broadcast. At each site, the treatments were arranged in a randomized complete-block design with four replicates. At Lanoraie and Ste. Victoire, the plot size was 10 × 10 m, compared with 6 × 10 m at L’Acadie. The seeding rate was 150 kg ha−1 and a row spacing of 0.15 m was used. Sample Collection and Analysis Shoot biomass was sampled weekly for 8 wk at all three sites in 2004, for 5 wk at Lanoraie and 2 wk at L’Acadie in 2005, and for 4 wk at L’Acadie in 2006, using a 0.28 × 0.72 m quadrat in each plot. The sampling dates are presented in Table 2. Whole plants were cut at ground level and weighed fresh, and subsamples of approximately 500 g were collected for DM determination and laboratory analysis. Subsamples were dried at 55°C in a forced-draft oven for 3 d, ground to pass through a 1-mm screen in a Wiley mill, and stored at room temperature until laboratory analysis. As described by Isaac and Johnson (1976), a mixture of sulfuric and Agronomy Journal • Volume 102, Issue 1 • 2010
Table 2. Wheat shoot biomass on different sampling dates at six site-years. Sampling Days after dates seeding Lanoraie 2004
0
30
40
60
70
Applied N, kg ha−1 80 90 110 120
-----Shoot biomass, Mg DM ha–1#--– – – – – – 3.34 2.76 4.39 5.14 5.88 4.87 5.34 5.64 6.01 5.06
160
F 200 120c‡ 120s§ prob. LSD¶
– – – 3.09 4.49 4.50 3.72 5.89
– – – 3.97 4.21 5.46 5.20 5.61
– 1.04 2.89 4.14 4.71 6.09 6.27 6.03
0.21 1.19 3.07 4.43 4.87 5.91 6.67 6.49
ns‡‡ † ** *** ** † ** **
0.42 0.58 0.61 1.15 1.96 1.52 1.58 0.09 0.31 0.51 0.57 0.94
19 May 3 June 14 June 22 June 30 June 5 July 12 July 19 July
27 42 53 61 69 74 81 88
0.16 0.67 1.38 2.06 2.52 3.04 3.10 3.25
0.20 0.80 2.30 – – – – –
–†† – – 3.13 4.10 4.54 4.27 4.63
0.21 – – – – – – –
Lanoraie 2005
30 May 7 June 14 June 21 June 28 June
39 47 54 61 68
0.28 0.57 1.02 1.85 2.49
0.31 0.81 – – –
– – 1.48 2.22 3.54
0.33 – – – –
– – 1.20 2.02 3.54
– – 1.29 2.26 3.95
– – 1.55 2.34 3.56
– – 1.63 2.32 3.40
– 0.99 1.94 3.19 5.12
0.39 1.18 2.02 3.76 5.33
† ** ** *** ***
Ste-Victoire 2004
25 May 15 June
18 39
0.16 0.91
0.15 0.92
– –
0.17 –
– –
– –
– –
– –
– 1.00
0.16 1.06
ns ns
22 June 29 June 7 July 14 July 22 July 26 July
46 53 61 68 76 80
1.49 2.39 3.28 3.75 3.70 5.33
1.82 2.62 – – – –
– – 3.29 3.73 4.60 4.91
– – – – – –
– – 3.27 4.70 4.90 5.23
– – 3.41 5.24 5.40 5.42
– – 3.44 4.23 4.93 5.03
– – 3.55 4.30 4.38 5.51
1.84 2.62 3.72 4.91 6.79 5.30
2.22 2.31 4.47 6.07 6.21 6.57
ns ns ns † ** ns
21 June 30 June 9 July 14 July 21 July 30 July 5 Aug. 10 Aug.
46 55 64 69 76 85 91 96
0.19 0.35 0.87 1.73 2.95 4.31 3.23 3.66
0.19 0.62 1.27 2.19 4.41 5.63 5.38 5.69
29 June 6 July
52 59
L’Acadie 2004
L’Acadie 2005 L’Acadie 2006
4.34 5.44
– 0.62 1.30 2.71 4.72 5.18 6.38 4.45
– 0.45 1.63 2.62 4.13 4.85 4.98 4.58
ns † * ns ns ns * ns
5.07 5.74
3.42 5.73
4.36 6.22
* ns
3.40 4.91 4.87 4.91
4.12 4.14 5.90 4.14
ns ns ns ns
1 July
53
2.69
3.26
6 July 13 July 24 July
58 65 76
4.04 5.85 4.04
4.25 6.45 4.25
1.53 1.47
0.22 0.42
1.93 0.93
* F statistic significant at the 0.05 probability level. ** F statistic significant at the 0.01 probability level. *** F statistic significant at the 0.001 probability level. † F statistic significant at the 0.10 probability level. ‡ 120c, conventional fertilization of 60 kg N ha –1 at seeding and 60 kg N ha –1 at the tillering stage. § 120s, saturated treatment of 120 kg N ha –1 applied at seeding. ¶ LSD, least significant difference. # DM, dry matter. †† Because of the split application of N, shoot biomass data are not presented for all treatments on the first sampling dates except for 0 and 120s kg N ha –1 and are presented only on the first sampling dates for the N applications (30 and 60 kg N ha –1) at seeding. ‡‡ ns, means not significant at P = 0.10.
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selenious acids was used to mineralize 0.1-g samples of dried and ground wheat. Nitrogen was quantified with an automated continuous-flow injection analyzer using the method 13-107-06-2-D (QuikChem 8000; Lachat Instruments, Loveland, CO). Grain yield was determined in each plot using a plot combine (NM-Elite; Wintersteiger, Ried, Austria) on a 10-m2 (6.7 × 1.5 m) area located in the middle of each plot. The grain was dried at 55°C until the weight stabilized, and the grain yield was adjusted to 14% moisture. Data Analysis Shoot biomass data for each sampling date, site, and year were subjected to ANOVA using PROC GLM of SAS (SAS Institute, 2004), and the LSD values were presented when the treatment effect had a P value ≤0.10. Nitrogen concentration data and SEM values were reported previously (Ziadi et al., 2008a). The determination of a critical N curve requires the identification of data points for which N does not limit shoot growth or is not in excess. These data points correspond to a N rate above which shoot biomass does not significantly increase. We used the procedure proposed by Greenwood et al. (1990) to identify these data points; another procedure was suggested by Justes et al. (1994), but it requires a much larger data set than that available in our study. For each site-year and sampling date, the significantly highest shoot biomass (P ≤ 0.05) obtained with any rate of N fertilization and the corresponding N concentration were identified and selected. In cases where the highest shoot biomass was obtained with two or more N rates, the lower rate was selected. These data points were then used to determine the relationship between critical N concentration and shoot biomass using an allometric function. Data points not retained for establishing the parameters of the allometric function were used to test the validity of the critical curve. These data points were characterized as representing limiting and nonlimiting N conditions using a method similar to that of Greenwood et al. (1990). Sampling dates were not used to test the validity of the critical N dilution curve if the ANOVA indicated no significant (P > 0.10) differences among the N application rates (Table 2). For the remaining sampling dates, treatments were classified using the LSD test. Treatments with significantly (LSD0.05) lower shoot biomass were considered to be limiting, whereas treatments with significantly higher shoot biomass were considered to be nonlimiting. Treatments were not selected if their shoot biomass was classified in more than one group. The N nutrition index (NNI) of the crop at each sampling date was determined by dividing the N concentration of the shoot biomass by Nc, an approach previously used for tall fescue (Bélanger et al., 1992), timothy (Bélanger and Richards, 1997), potato (Bélanger et al., 2001), and corn (Ziadi et al., 2008b). The relative yield was calculated as the ratio of the grain yield obtained for a given N rate to the highest grain yield across the N application rates; relative yield values were reported previously (Ziadi et al., 2008a). The relative yield was expressed as a function of NNI, and the linear-plateau function was estimated using SAS (SAS Institute, 2004). Results and Discussion Shoot Biomass and Nitrogen Concentration Shoot biomass during the growing season ranged from 0.16 to 6.79 Mg DM ha−1, depending on the N application rate, sampling date, site, and year (Table 2). The N application rate affected shoot biomass throughout the growing season, although this effect was 244
not always statistically significant. Nitrogen fertilization significantly increased grain yield at all site-years except at L’Acadie in 2005. Grain yields are presented in Ziadi et al. (2008a). Nitrogen concentration in the shoot biomass decreased during the growing season, and a higher N application rate generally resulted in a higher plant N concentration (Fig. 1). A decrease in N concentration with time, or with advancing maturity, was reported for corn (Plénet and Lemaire, 2000; Ziadi et al., 2008b), potato (Bélanger et al., 2001), timothy (Bélanger and Richards, 1997, 1999), and wheat (Justes et al., 1994). This decline in N concentration with time, or with increasing biomass, is attributed to a decrease in the fraction of total plant N associated with photosynthesis in relation to a concomitant increase in the N fraction of structural and storage constituents (Caloin and Yu, 1984; Lemaire et al., 1992; Lemaire and Chartier, 1992; Bélanger and Gastal, 2000). Nitrogen concentrations varied from a maximum of 36.3 g kg−1 DM (L’Acadie, 9 July 2004) to a minimum of 6.0 g kg−1 DM (Ste. Victoire, 26 July 2004) for shoot biomass ranging from 1.6 to 7.0 Mg DM ha−1. For a similar range of shoot biomass, Justes et al. (1994) reported N concentrations of approximately 10 to 60 g N kg−1 DM for winter wheat grown with different N application rates in France. Determination of a Critical Nitrogen Dilution Curve Parameter Estimation Among all site-years, only 16 sampling dates out of 35 met the previously defined statistical criteria (Table 3). Each of these sampling dates provided a critical point of N concentration for a given shoot biomass. Two critical points corresponded to a shoot biomass of
