Cultivar and fertilizer S rate interaction effects on canola yield, seed quality and S uptake

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1 Cultivar and fertilizer S rate interaction effects on canola yield, seed quality and S uptake S. S. Malhi and K. S. Gill 1 Agriculture and Agri-Food Canada, Research Farm, P.O. Box 1240, Melfort, Saskatchewan, Canada S0E 1A0 ( malhis@agr.gc.ca). Received 18 March 2005, accepted 3 August Malhi, S. S. and Gill, K. S Cultivar and fertilizer S rate interaction effects on canola yield, seed quality and S uptake. Can. J. Plant Sci. 86: Since canola has a high requirement for S, and canola cultivars have differences in growth rate and yield potential, a differential response of canola cultivars to soil S deficiency and S fertilization can be expected. A 3 site-year field study was conducted on S-deficient soils in northeastern Saskatchewan to determine response of four canola cultivars to S deficiency and S fertilization in terms of yield (seed and straw), seed quality (oil, protein and S concentration), and S uptake (seed and straw). Two Brassica napus L. cultivars (Quantum and AC Excel) and two B. rapa L. cultivars (Maverick and AC Parkland) were compared at 0, 5, 10, and 15 kg S ha 1 rates. Both the actual values of seed and straw yield and seed S uptake and the responses to S fertilization were greater for the B. napus than B. rapa cultivars. Optimal yield response for all the four cultivars occurred at the 10 kg S ha 1 rate, though seed quality and S uptake responded up to the 15 kg S ha 1 rate. Sulphur fertilization response was quadratic for seed and straw yield, seed oil and protein concentration, and S uptake in seed, while the response for seed S concentration and straw S uptake was inconsistent. In summary, in spite of differences in magnitude of the response of tested cultivars to S fertilization, the similar nature of the response and optimal yield at the same S rate indicated that specific S fertilization recommendations for individual canola cultivars are unnecessary. Key words: Canola cultivars, oil concentration, seed quality, S rates, S uptake, yield Malhi, S. S. et Gill, K. S Interaction du cultivar et de l engrais S et effets sur le rendement du canola, sur la qualité de ses graines et sur l absorption du S par la plante. Can. J. Plant Sci. 86: Le canola exigeant une grande quantité de S et les cultivars n ayant pas tous le même taux de croissance ni rendement potentiel, on peut s attendre à ce que les variétés réagissent différemment à un sol carencé et à l application d engrais S. Les auteurs ont entrepris une étude sur le terrain de trois années-sites sur des sols carencés en S du nord-est de la Saskatchewan en vue de préciser la réaction de quatre cultivars de canola à la carence en S et à la fertilisation S au niveau du rendement (graines et paille), de la qualité des semences (teneur en huile, en protéines et en S) et de l absorption de S (par les graines et la paille). Les auteurs ont comparé deux cultivars de Brassica napus L. (Quantum et AC Excel) et deux de B. napa L. (Maverick et AC Parkland) après application de 0, 5,10 et 15 kg de S par hectare. Le rendement grainier et en paille réel et l absorption du S par les graines étaient plus élevés chez les cultivars de B. napus que chez ceux de B. rapa, les premiers réagissant aussi davantage à la fertilisation. Le rendement optimal a été enregistré au taux de 10 kg de S par hectare pour les quatre cultivars, bien que la qualité des semences et l absorption du S réagissent aussi au taux de 15 kg de S par hectare. La réaction aux engrais soufrés est d ordre quadratique pour le rendement grainier et en paille, la teneur en huile et en protéines de la graine ainsi que l absorption du S par la graine, mais elle est inconsistante pour la teneur en S des semences et l absorption du S par la paille. En résumé, bien que l ampleur de la réaction des cultivars examinés aux engrais S varie, la réaction similaire et le rendement optimal au même taux de fertilisation laissent croire que la formulation de recommandations spécifiques à chaque cultivar pour la fertilisation S serait superflue. In the Canadian prairies, about 5.5 million ha of land is under canola production, with majority of this area in the Parkland region (Statistics Canada 1999). Approximately 4 million ha of the agricultural soils are deficient in S for optimum crop yield, and substantially greater areas are potentially S deficient (Bettany et al. 1982; Doyle and Cowell 1993). Because of high S requirements (Grant and Bailey 1993; Jackson 2000), canola is more prone to S deficiency than cereals (Mills and Jones 1996). In recent years, many canola producers in the Parkland region have experienced substantial losses in seed yield, apparently due to severe S deficiency. In earlier studies, canola has responded readily to S fertilization when grown on S-deficient soils (Nyborg et al. 1974; Ukrainetz 1982; Janzen and Bettany 1984; Nuttall et al. 1987). 1 Present address: Innovation Consulting Ltd., B Avenue, Edmonton, Alberta, Canada T5L 5A1. Mots clés: Cultivars de Canola, teneur en huile, qualité des semences, taux de fertilisation S, absorption du S, rendement 91 Crop yield response to S fertilization on S-deficient soils depended on soil type, with significant increase on coarse-textured soils but not on medium-textured soils (Ridley 1972). The response of different cultivars of the Brassica species to S fertilization in controlled conditions and some field studies has been inconsistent (Wetter et al 1970; Aulakh et al. 1980; Nuttall et al. 1987; Asare and Scarisbrick 1995; Ahmad et al. 1998; Ahmad and Abdin 2000). Since B. napus and B. rapa canola cultivars differ in their growth rate, yield potential, rooting system, and genetics, a potential exists for canola cultivars to differentially respond to S fertilization. Consequently, the objective of this study was to compare the relative response of selected canola cultivars to S fertilization on S-deficient soils. MATERIALS AND METHODS A 3 site-years field study was conducted in 1999 and 2000 on S-deficient Gray Luvisol (Boralfs) soils in northeastern

2 92 CANADIAN JOURNAL OF PLANT SCIENCE Table 1. Some characteristics of soils for the different site-years in northeastern Saskatchewan Site-year Great Group z Depth (cm) Texture Organic matter (%) ph (1:2 water) SO 4 -S (mg kg 1 ) NO 3 -N (mg kg 1 ) Tisdale 1999 Gray Luvisol 0 15 Sandy loam Tisdale 2000 Gray Luvisol 0 15 Sandy loam Archerwill 2000 Gray Luvisol 0 15 Sandy loam z Based on Canadian Soil Classification System. Saskatchewan (Table 1). The average (30-yr) growing season precipitation and mean daily temperature for this area are 21, 41, 62, and 67 mm and 2.2, 10.6, 15.5, and 17.6 C for May, June, July, and August, respectively. Near average precipitation and temperature conditions prevailed during the crop growing seasons of the experimental site-years. Sixteen treatments consisting of four S rates (0, 5, 10, and 15 kg S ha 1, as K 2 SO 4 ) and four cultivars (Quantum and AC Excel Brassica napus L; Maverick and AC Parkland B. rapa L.) were applied in a randomized complete block (RCB) design with four replications. Plot size was 1.8 m 7.5 m, and each plot received a blanket application of 120 kg N, 30 kg P and 20 kg K ha 1. All fertilizers were broadcast on soil surface just prior to seeding, followed by a rotovation to incorporate the fertilizers into the 0 10 cm soil. A double-disc press drill was used to seed canola at 17.8-cm row spacing and 9 kg ha 1 planting rate. Data were recorded on yield, total S concentration, S uptake, and seed protein and oil concentration. Seed yield was determined by harvesting an area 1.25 m wide and 7.0 m long with a plot combine, and straw yield was calculated from hand harvested samples collected from two 1-m long rows in each plot. Oven dry (60 o C) samples were analyzed for oil, total N and total S in seed, and total S in straw. Oil concentration was determined using crude fat method [Association of Official Analytical Chemists (AOAC) 1990]. Total S was determined by digestion of samples in nitric acid-hydrogen peroxide and measuring its concentration in the digest by ICP-AES (Huang and Schulte 1985). Total N was determined by sample digestion in nitric acidhydrogen peroxide and detection of N by thermal conductivity using a CNS combustion analyzer (AOAC 1995). Protein concentration was calculated by multiplying the total N by 6.25 (Williams et al. 1998). The response of each cultivar to S rate was assessed with regression using RSREG procedure in SAS (SAS Institute, Inc. 1993). As the trend of the response for most parameters to S fertilization in the 3 site-years was similar, so results are presented as means of all site-years. Observed values, estimated lines and regression equations of the measured parameter means for each cultivar as a function of S rate are presented in the figures. The significance of linear and quadratic components of the regression equations is given in Table 2. RESULTS AND DISCUSSION As the typical response of crop parameters to fertilizer application for most nutrient deficiency situations in soil is quadratic in nature, quadratic regression equations and the observed values of the measured parameters for each cultivar are presented. For the response of measured parameters of the tested canola cultivars with increase in S rate, there was an improvement in the R 2 values with the use of quadratic regression over linear regression in many cases. The values of linear and quadratic components of the total R 2 values are given in Table 2 and the total R 2 values with the significance level are presented in each figure. Seed and Straw Yield Magnitude of the seed yield response to S fertilization was different for each cultivar and thus the differences in seed yield produced by different cultivars varied with S rate (Fig. 1a). Increase in seed yield with application of 5 kg S ha 1 was 608, 243, 143 and 174 kg ha 1 for Quantum, AC Excel, Maverick and AC Parkland, respectively. Corresponding seed yield increase with increase in S rate from 5 to 10 kg S ha 1 was 256, 230, 179 and 181 kg ha 1. But the change in seed yield with increase of S rate from 10 to 15 kg S ha 1 rate was relatively small (from 28 to 64 kg ha 1 ) and did not show a consistent trend. Response of seed yield to 15 kg S ha 1 rate was higher for B. napus cultivars (837 kg ha 1 for Quantum and 538 kg ha 1 for AC Excel) than B. rapa cultivars (380 kg ha 1 for Maverick and 401 kg ha 1 for Parkland). Relatively greater response to S fertilization for B. napus cultivars than B. rapa cultivars translated into larger seed yield differences between the two groups of cultivars at higher S rates. For example, Quantum produced 160 and 560 kg ha 1 more seed yield than Parkland at 0 and 15 kg S ha 1, respectively. Thus, B. napus cultivars could be considered more efficient (seed yield per unit of applied S) user of S fertilizer than B. rapa cultivars. For all four cultivars, seed yield increase was greater from first increment of 5 kg S ha 1 compared with second or third increments (Fig. 1a). Averaged across cultivars, successive 5 kg S ha 1 rate increments resulted in seed yield increase of 293, 211 and 36 kg ha 1. Thus, seed yield increased mainly up to 10 kg S ha 1, and 10 kg S ha 1 appeared to be an optimum rate for these canola cultivars to correct the S deficiency at these S-deficient site-years. However, the amount of S fertilizer required for optimum seed yield will depend on soil type (i.e., the extent of soil supplies of available S, texture and organic matter content) and environmental conditions (Ridley 1972, 1973; Hamm et al. 1973; Harapiak 1980; Beaton and Soper1986; Doyle and Cowell 1993). Straw yield of all cultivars increased with S fertilization, and maximum value was obtained at 10 kg S ha 1 (Fig. 1b).

3 MALHI AND GILL CULTIVAR AND S RATE EFFECTS ON CANOLA 93 Table 2. The linear and quadratic components of the R 2 values for the regression equations to test the response of different canola cultivars to S fertilization rate Quantum AC Excel Maverick AC Parkland Parameter Linear Quad Linear Quad Linear Quad Linear Quad Seed yield (kg ha 1 ) Straw yield (kg ha 1 ) Oil concentration in seed (g kg 1 ) Protein concentration in seed (g kg 1 ) Total S concentration in seed (mg kg 1 ) Uptake of S in seed (kg ha 1 ) Uptake of S in straw (kg ha 1 ) Uptake of S in seed + straw (kg ha 1 ) Straw yield at different S rates was also greater for B. napus cultivars (range of 2500 to 3801 kg ha 1 for Quantum and 3106 to 3983 kg ha 1 for AC Excel) than for B. rapa cultivars (range of 2260 to 2921 kg ha 1 for Maverick and 2021 to 2898 kg ha 1 for Parkland). When data were averaged across cultivars, change in straw yield was 624, 208, and 117 kg ha 1 with first, second and third 5 kg S ha 1 additions, respectively. Like seed yield, the data showed a tendency for relatively greater straw yield values by B. napus cultivars compared with B. rapa cultivars, but S rate for maximum straw yield was almost similar for all cultivars. Overall, seed and straw yield data showed that both actual values and response to S fertilization for seed and straw yield were generally greater for the B. napus cultivars compared with B. rapa cultivars. This indicated that the extent of fertilizer-s-induced increase in seed yield varied with cultivar type. However, yield of all cultivars generally responded up to the same S rate of 10 kg S ha 1, which suggests similar S fertilizer requirements for optimum seed yield from each cultivar. In earlier studies, different Brassica cultivars have also shown diversity in actual yield and response to fertilization (Wetter et al. 1970; Nuttall et al. 1987; Asare and Scarisbrick 1995). In northwestern Saskatchewan, a significant nutrient cultivar interaction and a significant response of seed yield was obtained for four cultivars; and yield response showed a trend of Torch (B. rapa) > Regent (B. napus) > Candle (B. rapa) > Midas (B. napus) for most of the treatments with and without S (Nuttall et al. 1987). However, a significant and almost similar increase in seed yield of B. rapa (Candle and Torch) and B. napus (Tower and Midas) cultivars was obtained in northeastern Saskatchewan (Nuttall et al. 1987). Wetter et al. (1970) found the application of S caused increased seed yield in 1 of the 2 years for all Brassica species at one location, where seed yield of B. napus cultivar was greater than B. rapa, B. juncea, and B. hirta cultivars. No effect of S application was observed for any of the species at another location (Wetter et al. 1970). For two B. napus cultivars in the United Kingdom, yield response to 80 kg S ha 1 was 18.1% for dry matter and 1.6% for seed for the cultivar Ariana, and by 6.5% for dry matter and 6.2% for seed for the cultivar Susana (Asare and Scarisbrick 1995). Ahmad et al. (1998) stated that S fertilization increased leaf area index, photosynthesis rate, and biomass accumulation rate of both B. juncea (Pusa Jai Kisan) and B. rapa (Pus Gold) cultivars, and it increased their seed yield by 130 and 146%, respectively. Also, B. juncea accumulated more biomass than B. rapa; and maximum leaf area index, photosynthesis rate, and biomass accumulation were attained at 60 and 45 days after seeding for B. juncea and B. rapa cultivar, respectively (Ahmad et al. 1998). Seed Quality Averaged across S rates, oil concentration in seed was 382, 392, 382, and 372 g kg 1 in Quantum, AC Excel, Maverick and Parkland, respectively. Oil concentration in canola seed increased with S fertilization and maximum oil concentration was achieved at 10 or 15 kg S ha 1 rate (Fig. 2a). Maximum increase in oil concentration in seed was 35, 27, 32 and 28 g kg 1 for Quantum, AC Excel, Maverick and AC Parkland, respectively. Oil concentration of tested cultivars thus showed similar response to S rate and did not suggest a need for different rate of S fertilization on these S-deficient soils. Protein concentration in seed was also different for the four cultivars and increased with S rate (Fig. 2b). Averaged across S rates, protein concentration in Maverick was lower than in Quantum. Also, Maverick had the lowest protein concentration among the four cultivars at all four S rates. The tested cultivars did not show any trend for differences in response to S fertilization. Averaged across cultivars, protein concentration tended to increase in response to S fertilization and maximum protein concentration was observed at 15 kg S ha 1. Protein concentration thus showed a tendency to increase with S fertilization up to 15 kg S ha 1, with almost similar response for the four cultivars. The differences in S concentration between cultivars were not consistent (Fig. 2c). Total S concentration of canola seed generally increased somewhat similarly with the S rate for all four cultivars. Generally, there was less increase in S concentration with the first 5 kg S ha 1 increment compared with the second and third increments, unlike the oil and protein concentrations in seed. The increase in seed S concentration of Quantum, averaged across 3 site-years, was 392, 633, and 425 mg kg 1 with the first, second and third 5 kg S ha 1 increment, respectively. Corresponding values were 150, 508, and 575 mg kg 1 for AC Excel, 200, 608, and 367 mg kg 1 for Maverick, and 458, 558, and 508 mg kg 1 for

4 94 CANADIAN JOURNAL OF PLANT SCIENCE Fig. 1. Seed and straw yield of four canola cultivars as a function of S rates in northeastern Saskatchewan (mean of 3 site-years; the source of seed yield is Malhi et al. (2005).

5 MALHI AND GILL CULTIVAR AND S RATE EFFECTS ON CANOLA 95 Fig. 2. Oil, protein, and total S concentration in seed of four canola cultivars as a function of S rates in northeastern Saskatchewan (mean of 3 site-years).

6 Fig. 3. Uptake of S in seed, straw and seed + straw of four canola cultivars as a function of S rates in northeastern Saskatchewan (mean of 3 site-years). 96 CANADIAN JOURNAL OF PLANT SCIENCE

7 MALHI AND GILL CULTIVAR AND S RATE EFFECTS ON CANOLA 97 Parkland. A relatively larger increase in seed yield with the first than the second and third increments of 5 kg S ha 1 was considered responsible for the comparatively smaller increase in S concentration with the first 5 kg S ha 1 increment compared with the second and third increments. Results from earlier studies (Wetter et al. 1970; Nuttall et al. 1987; Grant et al. 2003) have also shown diversity in actual values and response to S fertilization for oil, protein, and S concentrations in seed of Brassica species and cultivars, which support our findings. In a 4-yr study in northeastern Saskatchewan, a B. rapa (Candle) and a B. napus (Regent) cultivar had significant and similar increase in oil, protein and S concentrations in seed from S fertilization of one soil, while Candle had less protein, S and oil concentration in seed than Regent on two other soils (Nuttall et al. 1987). In another study in the Parkland region, oil concentration showed a trend of B. hirta (Moench.) < B. juncea B. rapa < B. napus, and the decline in oil concentration with S fertilization was greater for B. napus (25 g kg 1 ) than for B. rapa (18 g kg 1 ) cultivar, even though the decrease due to S fertilization was less than the approximately 45 g kg 1 higher oil concentration in B. napus than in B. rapa (Wetter et al. 1970). In the same study, seed protein concentration in all tested Brassica species was not influenced in 2 yr and increased for two species (B. napus and B. rapa) in another year. Protein concentration showed a trend of B. hirta > other Brassica species (Wetter et al. 1970). In India, Ahmad and Abdin (2000) observed generally lower oil concentration in a B. juncea (Czern. & Coss) cultivar (Pusa Jai Kisan, from 420 to 481 g kg 1 and averaged 448 g kg 1 ) than in a B. rapa cultivar (Pusa Gold, from 461 to 512 g kg 1 and averaged 488 g kg 1 ). The application of 60 kg S kg N ha 1 increased oil concentration of B. juncea and B. rapa by 60 and 51 g kg 1, respectively. Protein concentration in both cultivars was similar and increased with S application until a maximum was reached at 40 kg S ha 1. Total S concentration in B. juncea and B. rapa cultivars was different at all the tested S rates, and ranged from 5300 to 8000 mg kg 1 (average 6900 mg kg 1 ) and from 6200 to 9000 mg kg 1 (average 7900 mg kg 1 ), respectively (Ahmad and Abdin 2000). Application of 60 kg S ha 1 at another location in India increased oil concentration by 12% for yellow mustard, B. rapa, and by 16% for mustard, B. juncea (Aulakh et al. 1980). Protein and oil concentration tended to be greater for the B. napus cultivar Susana than for Ariana in a UK study (Asare and Scarisbrick 1995). As in the present study, in spite of the differences in response to S fertilization, there was no clear support for different fertilizer S rate recommendation in these studies. Uptake of S in Seed and Straw Sulphur uptake in seed and its response to S fertilization depended on cultivar, and the differences in S uptake in seed of tested cultivars varied at different S rates (Fig. 3a). Increase in S uptake with application of 5 kg S ha 1 was 1.86, 0.66, 0.40 and 0.54 kg ha 1 for Quantum, AC Excel, Maverick and AC Parkland, respectively. The corresponding increase with increase in S rate from 5 to 10 kg S ha 1 was 1.60, 1.20, 0.94 and 0.80 kg ha 1, but, the change in S uptake with increase in S rate from 10 to 15 kg S ha 1 rate did not show a consistent trend with respect to cultivars. Thus, the average response of S uptake in seed to 15 kg S ha 1 fertilization rate was generally higher for B. napus cultivars (3.60 kg ha 1 for Quantum and 2.53 kg ha 1 for AC Excel) than B. rapa cultivars ( 1.73 kg ha 1 for both cultivars). Relatively more S uptake in seed and its response to S fertilization for B. napus cultivars than B. rapa cultivars translated into larger differences between the two groups of cultivars at higher S rates. For example, Quantum had 0.54 and 2.40 kg ha 1 more S uptake in seed than Parkland at 0 and 15 kg S ha 1, respectively. As observed earlier for seed yield, B. napus cultivars could be considered more efficient (S uptake in seed per unit of applied S) user of S fertilizer than B. rapa cultivars. For all four cultivars, response of S uptake in seed to S fertilization was generally observed up to 15 kg S ha 1 and the nature of response was not consistent for cultivars (Fig. 3a). Averaged across cultivars, three successive 5 kg S ha 1 rate increments resulted in increase of S uptake in seed by 0.87, 1.06 and 0.36 kg ha 1, respectively. Thus, unlike seed yield, S uptake in seed generally increased up to 15 kg S ha 1. Uptake of S per kg of seed increased with increasing S rate, with maximum at the 15 kg S ha 1 rate. The S uptake ranged between g S kg 1 seed for Quantum, g S kg 1 seed for AC Excel, g S kg 1 seed for Maverick and g S kg 1 seed for AC Parkland. The B. napus cultivars tended to have more S uptake per unit of canola seed than B. rapa cultivars. Response of S uptake in straw to S fertilization did not show a consistent influence of cultivars (Fig. 3b). Uptake of S in straw generally increased with S fertilization, with exception of the decline in S uptake at 5 or 10 kg S ha 1 in some instances, and the maximum uptake was obtained at 15 kg S ha 1. Averaged across cultivars, S uptake in straw also increased up to 15 kg S ha 1 rate. Uptake of S in seed + straw reflected the combined effects of S uptake in canola biomass (Fig. 3c). As the amount of S uptake was relatively less for seed compared to straw, seed + straw data generally reflected the nature of S uptake data for straw. Overall, there were some differences in S uptake in seed + straw between cultivars, but all cultivars responded up to 15 kg S ha 1 rate. Thus, different S fertilization rate for each cultivar is not needed. CONCLUSIONS On S-deficient soils, response to S fertilization was relatively greater for seed yield than straw yield. The B. napus cultivars (Quantum and AC Excel) showed greater seed and straw yield, and S uptake in seed compared with the B. rapa cultivars (Maverick and Parkland). The response to S fertilization was generally quadratic for seed and straw yield, oil and protein concentration in seed, and S uptake in seed, while the nature of the response for S concentration in seed and S uptake in straw was not consistent. Generally, all cultivars had near maximum seed and straw yield at 10 kg S ha 1, while near maximum oil, protein, and S concentrations

8 98 CANADIAN JOURNAL OF PLANT SCIENCE in seed, as well as the S uptake in seed and straw, were observed at 15 kg S ha 1. Overall, even though the response to S fertilization was greater for the B. napus than B. rapa cultivars, the findings did not indicate any need for a different fertilizer S rate for each cultivar to maximize yield on these S-deficient soils. ACKNOWLEDGEMENTS The authors thank D. Leach, K. Fidyk and K. Hemstad-Falk for technical help; and Mr. S. Brandt and Dr. A. M. Johnston for internal review of the manuscript. Ahmad, A. and Abdin, M. Z Interactive effect of sulphur and nitrogen on the oil and protein concentrations and on the fatty acid profiles of oil in the seeds of rapeseed (Brassica campestris L.) and mustard (Brassica juncea L. Czern. and Coss.). J. Agron. Crop Sci. 185: Ahmad, A., Abraham, G., Gandotra, N. and Abrol, Y. P Interactive effect of nitrogen and sulphur on growth and yield of rapeseed-mustard (Brassica juncea L. 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