Influence of controlled-release urea on seed yield and N concentration, and N use efficiency of small grain crops grown on Dark Gray Luvisols 1

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1 Influence of controlled-release urea on seed yield and N concentration, and N use efficiency of small grain crops grown on Dark Gray Luvisols 1 S. S. Malhi 1, Y. K. Soon 2, C. A. Grant 3, R. Lemke 4, and N. Lupwayi 5 1 Agriculture and Agri-Food Canada, P.O. Box 1240, Melfort, Saskatchewan, Canada S0E 1A0 ( malhis@agr.gc.ca); 2 Agriculture and Agri-Food Canada, P.O. Box 29,, Canada T0H 0C0; 3 Agriculture and Agri-Food Canada, Brandon, Manitoba, Canada R7A 5Y3; 4 Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada S7N 0X2; and 5 Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada T1J 4B1. Received 26 October 2009, accepted 3 March Malhi, S. S., Soon, Y. K., Grant, C. A. Lemke, R. and Lupwayi, N Influence of controlled-release urea on seed yield and N content, and N use efficiency of small grain crops grown on Dark Gray Luvisols. Can. J. Soil Sci. 90: Field experiments were conducted on Dark Gray Luvisolic soils (Typic Cryoboralf) from 2004 to 2006 (wheat-canola-barley rotation) near, and from 2004 to 2007 (barley-canola-wheat-barley rotation) near Beaverlodge, Alberta. The aim was to compare the effects of controlled-release urea (CRU) vs. conventional urea (hereafter called urea) on seed yield and N (i.e., protein) concentration, and N use efficiency (NUE). The treatments were combinations of tillage system [conventional tillage (CT) and no tillage (NT)], and N source (urea, CRU and a blended mixture), placement method (spring-banded, fall-banded and split application) and application rate (090 kg N ha 1 ). There was no tillage fertilizer treatment interaction on the measured crop variables. Seed yield and crop N uptake and, to a lesser degree, seed N concentration generally increased with N application to 90 kg N ha 1. Fall-banded CRU or urea generally produced lower crop yield and N uptake than spring-banded CRU or urea. Split application of urea (half each at seeding and tillering) resulted in higher seed yield and N concentration in at least 3 of 7 site-years than did CRU and urea applied at a similar rate. A blend of urea and CRU was as effective as spring-banded CRU (at Star City only). Seed yield, N recovery and NUE were higher with spring-banded CRU than urea in 2 site-years, and similar to urea in other site-years. We conclude that for boreal soils of the Canadian prairies, spring-banded CRU is as effective as urea, and in some years more effective, in increasing crop yield and N recovery; however, urea split application can be even more effective in addition to having an advantage in managing risk. Key words: Controlled-release urea, Gray Luvisol, nitrogen source, nitrogen recovery, nitrogen use efficiency, tillage systems Malhi, S. S., Soon, Y. K., Grant, C. A. Lemke, R. et Lupwayi, N Influence de l ure ea` libe ration lente sur le rendement grainier et la teneur en N, et efficacite de l utilisation du N par les petites ce re ales cultive es sur des luvisols gris fonce. Can. J. Soil Sci. 90: Les auteurs ont effectué des essais sur des luvisols gris fonce (cryoboralf typique) de 2004 a` 2006 (assolement ble -canola-orge) pre` s de Star City, en Saskatchewan, et de 2004 a` 2007 (assolement orge-canolable ) pre` s de Beaverlodge, en Alberta. Ces essais sur le terrain devaient comparer l incidence de l ure e a` libe ration lente (ULL) à celle de l urée ordinaire (ure e dans le reste du texte) sur le rendement grainier et la teneur en N du grain (à savoir, prote ines) ainsi que sur l efficacite de l utilisation du N (EUN). Les traitements combinaient le re gime de travail du sol (travaille classique [TC] et non-travail du sol [NT]), la source de N (urée, ULL et mélange), la me thode de placement (en bandes au printemps, en bandes a` l automne et application fractionnée) et le taux d application (0 à 90 kg de N par hectare). Le travail du sol et l amendement n interagissent pas pour modifier les variables de la culture. En ge ne ral, le rendement grainier et l absorption de N ainsi que, dans une moindre mesure, la concentration de N dans le grain augmentent avec le taux d application d engrais N jusqu a` 90 kg par hectare. L application d ULL ou d ure e en bandes à l automne de bouche géne ralement sur un rendement et une absorption de N plus faibles que l application des meˆ mes amendements en bandes au printemps. L application fractionne e d ure e (la moitie aux semis et l autre moitie au tallage) donne lieu a` un rendement grainier et a` une teneur en N plus éleve s au moins trois années-sites sur sept, comparativement à l application d un taux identique d ULL et d ure e. Le me lange d ure e et d ULL est aussi efficace que l application d ULL en bandes au printemps (a` Star City seulement). Comparativement a` l urée, l application d ULL en bandes au printemps a entraıˆ ne une amélioration du rendement grainier, de l absorption du N et de l EUN a` deux années-sites, les re sultats étant similaires pour les autres anne es-sites. Les auteurs en concluent que dans les sols des Prairies canadiennes situe s en zone bore ale, l application d ULL en bandes au printemps est aussi efficace, voire davantage, certaines années, que celle d ure e 1 Brand name ESN TM is used for the convenience of the reader and no endorsement whatsoever of this product is intended. 363 Abbreviations: CRU, controlled-release urea; CT, conventional tillage; FB, fall-banded; NPE, N physiological efficiency; NRE, N recovery efficiency; NT, no tillage; SB, spring-banded

2 364 CANADIAN JOURNAL OF SOIL SCIENCE pour ce qui est de la hausse du rendement et de l absorption du N; cependant, l application fractionne e d ure e s ave` re parfois d une efficacite supérieure, en plus de pre senter l avantage d une gestion des risques. Mots clés: Ure e à libération lente, luvisol gris, absorption de l azote, source d azote, efficacité de l utilisation de l azote, re gime de travail du sol Most soils in the Canadian prairies are deficient in N; thus high crop yields are constrained without N fertilizers. Where N fertilizers are used, their usage is more efficient if the N supply is synchronized with crop N demand, and N losses are minimized (e.g., through gaseous, leaching or runoff losses). The use of controlled-release N fertilizers, such as polymer-coated urea, which are designed to synchronize their N release pattern with crop N uptake rates, may be a step toward solving the synchrony problem. Rates of fertilizer N release and crop N uptake are largely controlled by soil moisture and temperature. The polymers used to coat the urea granules are generally durable and exhibit predictable release rates when average temperature and moisture conditions prevail (Blaylock et al. 2005). If those expected conditions are met, controlled-release urea (CRU) can improve N use efficiency by increasing N uptake and reducing the accumulation and downward movement of nitrate in soil, thus lowering the potential for N loss to the atmosphere (Blaylock et al. 2005). Such fertilizers have been assessed previously for a variety of crops (Savant et al. 1983; Nyborg et al. 1999; Shoji et al. 2001; Drost et al. 2002; Nelson et al. 2009), but their effectiveness has varied considerably among various studies and years. Zhang et al. (2000) reported that slow-release coated urea did not improve barley yield but increased protein content and reduced potential N loss compared with uncoated urea. Nelson et al. (2009) found no difference in corn grain and silage yields between coated and noncoated urea; however, coated urea reduced subsoil nitrate concentrations early in the growing season. Other researchers have observed that coated urea increased the yields of wheat (Fan et al. 2004), barley and potato (Shoji et al. 2001), and onion (Drost et al. 2002), and nutrient use efficiency (Shoji et al. 2001), but had no effect on the protein content of wheat (Peltonen and Virtanen 1994). In southern Alberta, coated and uncoated urea produced no significant differences in the seed yield and N uptake of winter wheat (McKenzie et al. 2007). These divergent experimental results suggest that: (i) CRU vary greatly in their effectiveness with field conditions, i.e., may not be beneficial under some field conditions, e.g., dry soil in southern Alberta; and (ii) some forms of CRU and its placement method may not effectively synchronize N release with crop demand. Chen et al. (2008), in a review, also found that CRU increased crop production in some but not all studies, and that its effectiveness will depend on crop, soil climate and management factors. They suggested that urea coated with a polymer, polyolefin or humic acid showed the greatest potential for use in dryland or irrigated cropping. In traditional small grain production on the prairies, N fertilizer is typically applied near seeding, while a major portion of crop N uptake occurs later in the growing season. Thus, there is a potential with CRU to increase crop N use efficiency and reduce fertilizer N loss by leaching, volatilization, and denitrification. The use of CRU for a variety of crops in the boreal region of the Canadian prairies, managed under both no-till (NT) and conventional tillage (CT), has not been welldocumented. This study was done to evaluate the effectiveness of CRU compared with conventional urea (hereafter called urea) in increasing crop yield, seed protein or N content, N recovery, and N use efficiency, and in minimizing nitrate accumulation in soil and nitrous oxide (N 2 O) gas emissions from soil to the atmosphere under NT versus CT management. Here, we report the experimental results for the Dark Gray Luvisolic soils on seed yield and N concentration, and N use efficiency. A subsequent report will deal with the dynamics and distribution of available N in the soil and N 2 O loss. MATERIALS AND METHODS A field experiment was conducted in near (lat ?N, long ?W), on a Dark Gray Luvisol (Typic Cryoboralf) clay loam soil. The soil (015 cm) contained 38 g organic C kg 1 and 3.0 g total N kg 1 soil, and had a ph of 6.3. A second experiment was conducted near Beaverlodge, Alberta (lat. 55 o 11?N, long. 119 o 32?W), also on a Dark Gray Luvisol loam to clay loam soil from 2004 to The soil to 15 cm depth contained 29 g organic C kg 1 and 3.1 g total N kg 1 soil, and had a ph of 5.8. The experiments were each a split-plot design with four replications. Conventional tillage and NT systems were assigned to the main plots; combination of two sources of N (urea and CRU) and a blend, placement methods [spring-banded (SB), fall-banded (FB), or split application (half of fertilizer spring-banded and half broadcasted at tillering)], and N rates (0 to 90 kg N ha 1 ) were applied to the subplots. Nitrogen application rates were: 0, 0.5x 1.0x and 1.5x, where the base rate x60 kg N ha 1 at Star City for all three experimental years, and at Beaverlodge, x 60 kg N ha 1 in 2004 and 2007, 50 kg N ha 1 in 2005 and 55 kg Nha 1 in The 1x rate represents the rate of N application commonly used on commercial farm fields based on typical soil test results. The N treatments were: (1) control (0 N); (2) 0.5x rate urea-sb; (3) 1x rate

3 MALHI ET AL. * EFFECTS OF CONTROLLED-RELEASE UREA 365 urea-sb; (4) 1.5x rate urea-sb; (5) 0.5x rate CRU-SB; (6) 1x rate CRU-SB; (7) 1x rate urea-fb; (8) 1x rate CRU-FB; (9) 1x rate urea split application; and (10) 50:50 blend of urea and CRU spring-banded at 1x rate (this treatment was omitted at Beaverlodge). The CRU was a special polymer-coated ESN TM fertilizer with a N content of 44% (manufactured and supplied by Agrium, Calgary, Alberta, Canada). The study was initiated in spring 2004; thus no fall treatments were included for the 2004 growing season. Because of early arrival of wintry conditions and soil freeze-up in the fall of 2004 at Beaverlodge, no fall treatment was available for comparison for the 2005 crop year. Instead for those treatments, the N fertilizer was applied (at the intended or 1x rate) in the spring so as to maintain approximately similar levels of residual soil N as other fertilized treatments for the subsequent crop year. Fall N application was made on 2005 Oct. 20 and 2006 Sep. 19 at Beaverlodge, and on 2004 Oct. 15 and 2005 Oct. 05 at Star City. All treatments received a blanket application of 913 kg P (as triple superphosphate), and 42 kg K and 17 kg S (as potassium sulphate) ha 1 at seeding in Star City. At Beaverlodge, blanket applications at seeding were 1015 kg P ha 1 as monoammonum phosphate ( ) for all crops and, additionally, 1215 kg S ha 1 as potassium sulphate when canola and wheat were to be seeded. The plots were 3.9 m13 m at Beaverlodge, and 3.6 m7 m at Star City. The tillage and fertilizer treatments were maintained on the same plots for a 3-yr cropping cycle at Star City and a 4-yr cropping cycle at Beaverlodge. At Star City, wheat cv. AC Barrie was grown in 2004, canola cv. InVigor 2573 Liberty Link in 2005, barley cv. AC Rosser in 2006; at Beaverlodge, barley cv. AC Metcalfe was grown in 2004, canola cv. InVigor 2573 Liberty Link in 2005, wheat cv. CDC Teal in 2006, and barley cv. AC Metcalfe in An additional crop year was provided at Beaverlodge in order to have two crop years with the fall treatments. The crops were sown in mid- to late May. Plant emergence at Star City was determined about 3 wk after seeding by counting emerged plants in two 1-m lengths of crop row. At both locations, treatments that received the 1x rate of N fertilizers and the control were sampled by cutting plants in two 1-m rows at tillering (or bolting in the case of canola) and/or at anthesis for dry matter (DM) and N uptake determination. At maturity plants were cut at ground level from 1-m 2 areas for biomass, seed yield, and N uptake measurements. Seed and straw sub-samples (dried at 60 o C) were finely ground and analyzed for total N using an automated Dumas combustion analyzer. Nitrogen uptake is the product of the plant tissue dry matter and the N concentration in the tissue. Nitrogen use efficiency was calculated according to Moll et al. (1982), who defined it as the product of its two components: the N uptake (or recovery) efficiency and the N physiological (or utilization) efficiency. The N uptake (or recovery) efficiency (NRE) is defined as the ratio of above-ground N uptake to the N supply. The N physiological efficiency (NPE) is the ratio of seed yield to the above-ground N uptake. The N supply was estimated as the sum of N applied as N fertilizer and available soil N, which, in turn, was estimated as total above-ground N uptake at harvest from the check (nil N) plots (Limon-Ortega et al. 2000). Thus NUE NRE NPE, or (N uptake/n supply) (seed yield/n uptake) seed yield/n supply. Data for each year were subjected to analysis of variance (ANOVA) using the PROC GLM procedure (SAS Institute, Inc. 1990). Treatment effects and their interactions were considered significant at P For plant emergence, biomass, seed yield, seed N concentration and N uptake, N fertilizer treatment tillage interactions were not significant in almost all cases, so data for those variables were combined over the two tillage systems, unless otherwise indicated. RESULTS AND DISCUSSION The mean annual precipitation at Star City is 425 mm and the mean growing season (May to August) precipitation 244 mm. Growing season precipitation was 290 mm in 2004, 372 mm in 2005 and 220 mm in The growing season at Star City was wet in 2004 and wetter yet in 2005 (19 and 53% above-average rainfall); however, crop productivity was reasonably high in both years. In 2006, growing season conditions were nearaverage, and crop yield was very high. The mean annual and growing season precipitations at Beaverlodge are 468 and 247 mm, respectively. Growing season precipitation was 245 mm in 2004, 278 mm in 2005, 158 mm in 2006, and 233 mm in Here, the growing season was about average in 2004 and 2007, slightly wetter (13% higher rainfall) than normal in 2005, and considerably drier (36% lower rainfall) than normal in Crop growth was poor in Plant Emergence Plant emergence at, in 2004 to 2006 was not affected significantly by N fertilizer treatment (data not shown). Emergence for fertilizer treatment means ranged from 273 to 335 plants m 2 for wheat in 2004, from 144 to 187 plants m 2 for canola in 2005, and from 408 to 460 plants m 2 for barley in Plant emergence was much higher than the critical number of plants needed for optimum yield (Lafond 1994; Canola Council of Canada 1998). Plant density is considered very high for barley in These results indicate no material damage to seedling emergence from the fertilizer treatments. Tillage significantly affected (PB0.05) plant emergence in 2004 and 2005 (data not shown). In 2004, wheat plant density was higher under NT (332 plants m 2 ) than CT (309 plants m 2 ), but the opposite occurred in 2005 for canola (164 plants m 2 under NT vs. 173 plants m 2 under CT).

4 366 CANADIAN JOURNAL OF SOIL SCIENCE Early and Mid-season Crop Growth Response Shoot DM at the tillering (or bolting in the case of canola) growth stage was increased by up to 160% at Star City and 37% at Beaverlodge by urea and CRU applied at the 1x application rate (data not shown). The DM production increase was higher with spring than fall fertilizer application, with urea showing a bigger difference between time of application than did CRU. At Star City, shoot DM averaged 14% higher with urea- SB relative to CRU-SB. The lower growth response to CRU is attributed to the higher availability of urea N early in the season. There was no significant effect of tillage system on biomass production at the two growth stages. Shoot N accumulation among the treatments at tillering and anthesis (Table 1) followed a similar pattern to that of shoot DM at tillering (and anthesis). On all sampling occasions, shoot N uptake was higher when fertilizer N was applied at seeding than in the previous autumn. At Star City in 2005 and Beaverlodge in 2007, shoot N uptake was 2425% higher with CRU-SB than urea-sb. Above-average rainfall early in those growing seasons may have favourably influenced N availability from CRU relative to urea, which, due to its higher solubility, may be at greater risk of gaseous and leaching losses in wet soil. In 2006, at both locations, urea-sb resulted in higher shoot N uptake at tillering than did CRU-SB, probably due to lower availability of CRU-N during the drier than normal growing season. In other years with both samplings at tillering and anthesis, this difference in N uptake was not evident, suggesting that the lag in N availability with CRU-SB in 2006 was due mainly to dry soil. Fall N application resulted in higher N uptake with CRU than with urea at Star City, and in similar N uptake at Beaverlodge (Table 1). At Beaverlodge in 2006 (a dry year), N uptake at anthesis was 35% higher under NT than CT, probably because of better soil moisture conservation under NT during drought (data not shown) (Soon and Arshad 2005). Our results indicate that early in the growth period, a lag in available N was evident with CRU-SB under dry soil compared with urea-sb; however, no difference was noted between the treatments under normal or wet soil conditions. Seed and Straw Yield Seed and straw yields of wheat, canola and barley generally increased with increasing rate of N fertilizer to 90 kg N ha 1 (data shown only for seed yields, Figs. 1 and 2). The only exception was in 2006 at Beaverlodge when a small yield response was observed up to 55 kg N ha 1 rate. Wheat yield response to N input was low that year due to drought. Seed yield response of all three crop types to N application appeared to follow a linear or quadratic relationship. Seed and straw yields with 90 kg N ha 1 or 1.5x application rate were times greater than the zero-n control at Star City, and times greater at Beaverlodge. At Beaverlodge, CRU-SB increased seed yield compared with urea-sb during 2 yr (Fig. 2) with a yield advantage of 4% in 2005 and 10% in 2007 (mean of 0.5x and 1x N rates). At Star City, yields from CRU-SB and urea-sb were similar except in 2005, when CRU-SB resulted in 10% higher yield (1x rate only) than urea-sb. Wet soil conditions at both locations early in the 2005 growing season likely led to some denitrification and leaching losses from N applied as urea at seeding whereas release of CRU-N was delayed and its loss minimized. At both locations, fallbanded CRU or urea was generally inferior to springbanded CRU or urea except in 2006 at Beaverlodge when drought most likely reduced the effectiveness of both fertilizer forms regardless of time of application. At Beaverlodge in 2007, fall-banded urea or CRU was even less effective than the half rate of spring-banded urea or CRU in increasing seed yield. The poor result with fall Table 1. Effect of form and timing of application of urea fertilizers on crop N uptake at the tillering or anthesis stage of growth at Star City, Saskatchewan, and Fertilizer treatment z 2004 Anthesis (wheat) 2005 Anthesis (canola) 2006 Tillering (barley) 2005 Anthesis (canola) 2006 Tillering(wheat) 2007 Anthesis (barley) N uptake in shoot, kg N ha 1 Control (zero-n) Urea SB at 60 kg N ha CRU SB at 60 kg N ha Urea FB at 60 kg N ha CRU FB at 60 kg N ha SEM y 3.02** 3.77** 2.05** 2.02** 4.86** 3.72** z CRU, controlled-release urea; SB, spring banding; FB, fall banding application. N application rates at Beaverlodge were 50 kg N ha 1 in 2005, and 55 kg N ha 1 in y SEM, standard error of mean. Associated error degree of freedom was 12 when three treatments were compared, and 24 when five treatments were compared. **Denotes significant treatment effects by F test at P50.01.

5 MALHI ET AL. * EFFECTS OF CONTROLLED-RELEASE UREA 367 Seed yield, Mg ha : Wheat SEM= ; Canola SEM= : Barley SEM= Urea, fall CRU, fall Urea, fall CRU, fall Fertilizer N, x base rate Fig. 1. Seed yields of (a) wheat in 2004, (b) canola in 2005 and (c) barley in 2006 at, as influenced by the form, rate and method of application of urea fertilizer. Although not all data points are shown to reduce cluttering, the range is displayed in the data shown. A base rate of 1.0x for all 3 yr is 60 kg N ha 1. application is probably attributable to loss of fertilizer N between its application and sowing time. Split application of urea tended to produce near maximum seed yields except at Star City in 2004 and Beaverlodge in At the latter location, drought most likely rendered the second half of urea application ineffective. Dry soil in 2006 at Beaverlodge probably resulted in residual CRU that augmented crop yield response to fertilizer treatment in This possibility is supported by high nitrate content in the surface soil at seeding and anthesis in 2007 (personal communication, Y. K. Soon). The 50:50 blend of CRU and urea was almost as effective as spring-banded CRU or split application of urea (only at Star City, data not shown). Straw DM response to individual N fertilizer treatments was usually similar to seed yield response with few exceptions (data not shown). Seed yield of wheat at Star City in 2004 was higher under CT (3.93 Mg ha 1 ) than NT (3.71 Mg ha 1 ); this was probably due to cold weather, which could result in restricted early root development under NT relative to CT. In 2006 at Beaverlodge, seed yield was higher under NT (1.79 Mg ha 1 ) than CT (1.43 Mg ha 1 ) most probably because NT conserved soil moisture. Tillage treatments had no measurable effect on crop yields in other site-years and no influence on fertilizer N effects, i.e., there was no tillage fertilizer treatment interaction on yield. Seed N Concentration Seed N concentration (SNC, i.e., protein concentration) was usually higher in N-fertilized treatments than in the zero-n control (Table 2). At Star City in 2005, and at Beaverlodge in 2004, 2006 and 2007, seed N concentration increased greatly with increasing rate of N application (data not shown for 2004, Beaverlodge). The form of urea used had relatively little effect on seed N concentration at either location. Time of N application had little effect on SNC at Star City; however, at Beaverlodge, fall application resulted in lower SNC than did spring application. Split application of urea produced higher SNC in canola (in 2005, both locations) and barley (2004, Beaverlodge; data not shown) than did other N treatments at the same application rate. Therefore, split N application can be an effective means to increase seed protein content under some growth period conditions such as above-normal seasonal rainfall. Nitrogen application split between planting and flowering has been found to result in higher grain N content than did N fertilizer entirely applied at seeding (Strong 1982). Tillage had little effect on SNC and did not influence the fertilizer treatment effects (data not shown). Low seed N concentration at Star City in 2006 is attributed to dilution of N concentration by exceptionally high crop biomass. The previously noted high stand density for barley resulted in much biomass and competition for available N, resulting in low N concentration in plant parts. Nitrogen Uptake in Seed and Straw Similar to the seed yield response to N application, seed N uptake generally increased with increasing N rate to 90 kg N ha 1 or 1.5x rate at both locations (Table 3). Trends for N uptake in straw were usually similar to those for seed N uptake (Table 4). Significant

6 368 CANADIAN JOURNAL OF SOIL SCIENCE : Barley SEM= : Canola SEM= Seed yield, Mg ha Urea,spring : Wheat SEM=0.086 Urea, fall Fertilizer N, x base rate differences in seed N uptake among N treatments (at 1x rate) were evident in 2005 and 2006 at Star City, and in 2004, 2005 and 2007 at Beaverlodge (data not shown for 2004). Seed and straw N uptake among N treatments generally followed a similar trend to crop yield response, i.e., the differences in N uptake can be attributed mostly to DM production (Figs. 1 and 2). Seed N uptake at 1.0x N application rate (nominally about 60 kg N ha 1 ) at both locations was typically highest, depending on the year, with spring-banded urea or CRU, or split urea application (including 2004 at Beaverlodge with split urea application, data not shown). Nitrogen uptake in the seed was lower for fall-banded than spring-banded treatments. Seed and total shoot N uptake tended to be similar for spring-banded CRU and urea treatments except at Star City in 2005 and Beaverlodge in 2007 when CRU was superior to urea. A blend of CRU and urea resulted in similar seed N uptake as CRU. We note that the effectiveness of CRU-SB relative to urea-sb on shoot N accumulation at tillering or anthesis was maintained through maturity during wet or normal : Barley SEM=0.127 Urea, fall CRU, fall Fig. 2. Seed yields of (a) barley in 2004, (b) canola in 2005, (c) wheat in 2006, and (d) barley in 2007 at, as influenced by the form, rate and method of application of urea fertilizer. Although not all data points are shown to reduce cluttering, the range is displayed in the data shown. A base rate of 1.0x is: 60 kg N ha 1 for 2004 and 2007, 50 kg N ha 1 for 2005, and 55 kg N ha 1 for growing seasons (Table 1 vs. Table 3). In the dry year (2006 at both sites), shoot N uptake was higher in the urea-sb treatment at tillering but not different from the CRU-SB treatment at maturity. This can be attributed to a lag in available N with the CRU-SB treatment during early crop growth under drier than normal conditions. Tillage system had no effect on N uptake except at Beaverlodge in 2006 when both seed and straw N uptakes were higher under NT than CT (not shown; total N uptake, 45.9 kg ha 1 under NT vs kg ha 1 under CT). The difference is attributed mostly to the difference in dry matter accumulation since the N concentrations were not different. There was no tillage fertilizer treatment interaction. Nitrogen Use Efficiency and its Components Nitrogen use efficiency (NUE) and N recovery efficiency (NRE) decreased with increasing rate of N application at both locations (data not shown). This N rate dependent decrease in NUE, previously also noted by

7 MALHI ET AL. * EFFECTS OF CONTROLLED-RELEASE UREA 369 Table 2. Seed N concentration of wheat, canola and barley as affected by N source, and rate, time and mode of application at, and Fertilizer treatment z 2004 (wheat) 2005 (canola) 2006 (barley) 2005 (canola) 2006 (wheat) 2007 (barley) Seed N concentration (g N kg 1 ) Control (zero-n) Urea SB at 30 kg N ha Urea SB at 60 kg N ha Urea SB at 90 kg N ha CRU SB at 30 kg N ha CRU SB at 60 kg N ha Split at 60 kg N ha Urea FB z at 60 kg N ha CRU FB z at 60 kg N ha Blend at 60 kg N ha SEM y 0.46** 0.54** 0.32* 0.35** 0.63** 0.68** z CRU, controlled-release urea; SB, spring banding; FB, fall banding application. N application rates at Beaverlodge were multiples of 25 kg N ha 1 in 2005, and 27.5 kg N ha 1 in 2006 (instead of multiples of 30 kg N ha 1 ). y SEM, standard error of mean. The error mean square degree of freedom was 54 for Star City and 48 for Beaverlodge when fall application treatments were present, and 42 for Star City and 36 for Beaverlodge when fall application treatments were absent. *, **Denote significant treatment effects by F test at P50.05 and P50.01, respectively. Moll et al. (1982), was mostly due to the lower crop recovery of applied N as N application rate was increased. Here we confine our results and discussion to the N application rate typically used in commercial farm fields (1x rate or about 5060 kg N ha 1 ). Springapplied N fertilizers consistently resulted in higher NUE than fall-applied fertilizers (Table 5). Fertilizer N treatments varied with the year. No treatment effect on NUE was evident at Star City in 2004 and Beaverlodge in 2004 and Nitrogen use efficiency was higher in the CRU-SB than urea-sb treatment at Star City in 2005 and Beaverlodge in 2007 (Table 5). Split application of urea had a higher NUE than urea-sb in 2005 at Star City and Beaverlodge. At Beaverlodge, urea split application also resulted in higher NUE than CRU-SB in 2005; however, the results were reversed in The blended mixture also resulted in similar NUE as CRU-SB. Our results showed that NUE was higher with CRU-SB than urea-sb in 2 siteyears of 7, and it was mostly similar between CRU-SB and split application of urea. Spring-banded CRU resulted in higher NRE than urea-sb in 2 of 7 site-years (Star City in 2005 and Beaverlodge in 2007). The two treatments produced similar NRE in the other 5 site-years. Split N application resulted in higher NRE than did CRU-SB at Table 3. Nitrogen uptake in seed at harvest of wheat, canola and barley as affected N source, and rate, time and mode of application at Star City, Saskatchewan, and Treatment (N source/rate) z 2004 (wheat) 2005 (canola) 2006 (barley) 2005 (canola) 2006 (wheat) 2007 (barley) Seed N uptake (kg N ha 1 ) Control (zero-n) Urea SB at 30 kg N ha Urea SB at 60 kg N ha Urea SB at 90 kg N ha CRU SB at 30 kg N ha CRU SB at 60 kg N ha Split at 60 kg N ha Urea FB z at 60 kg N ha CRU FB z at 60 kg N ha Blend at 60 kg N ha SEM y 4.31** 1.94** 2.20** 4.04** 2.20** 3.04** z CRU, controlled-release urea; SB, spring banding; FB, fall banding application. N application rates at Beaverlodge were multiples of 25 kg N ha 1 in 2005, and 27.5 kg N ha 1 in 2006 instead of multiples of 30 kg N ha 1. y SEM, standard error of mean. The error mean square degree of freedom was 54 for Star City and 48 for Beaverlodge when fall application treatments were present, and 42 for Star City and 36 for Beaverlodge when fall application treatments were absent. **Denotes significant treatment effects by F test at P50.01.

8 370 CANADIAN JOURNAL OF SOIL SCIENCE Table 4. Nitrogen uptake in straw at harvest of wheat, canola and barley as affected by N source, rate, time and mode of application at Star City, Saskatchewan, and Treatment (N source/rate) z 2004 (wheat) 2005 (canola) 2006 (barley) 2005 (canola) 2006 (wheat) 2007 (barley) Straw N uptake (kg N ha 1 ) Control (zero-n) Urea SB at 30 kg N ha Urea SB at 60 kg N ha Urea SB at 90 kg N ha CRU SB at 30 kg N ha CRU SB at 60 kg N ha Split at 60 kg N ha Urea FB at 60 kg N ha CRU FB at 60 kg N ha Blend at 60 kg N ha SEM y 2.85** 1.29** 0.64** 2.19NS 0.50** 0.82** z CRU, controlled-release urea; SB, spring banding; FB, fall banding application. N application rates at Beaverlodge were multiples of 25 kg N ha 1 in 2005, and 27.5 kg N ha 1 in 2006 instead of multiples of 30 kg N ha 1. y SEM, standard error of mean. The error mean square degree of freedom was 54 for Star City and 48 for Beaverlodge when fall application treatments were present, and 42 for Star City and 36 for Beaverlodge when fall application treatments were absent. **Significant treatment effects by F test at P50.01; NS, not significant. Table 5. Nitrogen use efficiency (NUE), N recovery efficiency (NRE), and N physiological efficiency (NPE) of wheat, canola and barley as affected by form, time and mode of urea applied at 60 kg N ha 1 at, and Fertilizer treatment z 2004 (wheat) 2005 (canola) 2006 (barley) 2005 (canola) 2006 (wheat) 2007 (barley) NUE [kg seed (kg N) 1 ] Urea SB at 60 kg N ha CRU SB at 60 kg N ha Split at 60 kg N ha Urea FB at 60 kg N ha CRU FB at 60 kg N ha Blend at 60 kg N ha SEM y 1.51NS 0.69** 1.14** 1.30** 1.11NS 1.28** NRE [kg N (kg N) 1 ] Urea SB at 60 kg N ha CRU SB at 60 kg N ha Split at 60 kg N ha Urea FB at 60 kg N ha CRU FB at 60 kg N ha Blend at 60 kg N ha SEM 0.059NS 0.030** 0.027** 0.047** 0.027** 0.034** NPE [kg seed (kg N) 1 ] Urea SB at 60 kg N ha CRU SB at 60 kg N ha Split at 60 kg N ha Urea FB at 60 kg N ha CRU FB at 60 kg N ha Blend at 60 kg N ha SEM 1.02NS 0.66** 1.94* 0.95NS 1.02** 1.39** z CRU, controlled-release urea; SB, spring banding; FB, fall banding application. N application rate at Beaverlodge was 50 kg N ha 1 in 2005, and 55 kg N ha 1 in y SEM, standard error of mean. The error mean square degree of freedom was 30 for Star City and 24 for Beaverlodge when fall application treatments were present, and 18 for Star City and 12 for Beaverlodge when fall application treatments were absent. *, **Significant treatment effects by F test at P50.05 and P50.01, respectively; NS, and not significant.

9 MALHI ET AL. * EFFECTS OF CONTROLLED-RELEASE UREA 371 Beaverlodge in 2004 and 2005, but lower NRE in 2007 (data not shown for 2004). The blended mixture of urea and CRU produced similar effects as CRU-SB. Nitrogen recovery was lower with fall than spring application of N fertilizer in all 4 site-years with fall N application treatments. Noellsch et al. (2009) found higher N recovery with CRU than urea in low-lying landscape positions during 1 of 2 years when cumulative seasonal rainfall was lower (365 vs. 463 mm). The nitrogen utilization or physiological efficiency (NPE) reflects the effectiveness of assimilated N on seed production, and is probably influenced more by genotype and environment than management (Isfan 1990). There was little difference in NPE between urea-sb and CRU- SB (Table 5). At Star City, NPE was lowest with split N application in 2005 and with the blended mixture in There was no effect of fertilizer treatment on NPE in 2 of 7 site-years (data not shown for Beaverlodge in 2004). The range in NRE values, averaged over years with significant N treatment effects, was 1.42-fold compared with a 1.16-fold range in NPE values. Therefore, N treatments had a greater influence on NRE than NPE. Tillage effects on NUE or its components appear to be manifested when soil moisture conditions were wetter or drier than normal. At Star City, in 2005 which had a much wetter than normal growing season, NRE was higher while NPE was lower under NT compared with CT (Table 6). The NUE components compensated for each other with the result that there was no measurable difference in NUE (data not shown for NUE). In 2006 when soil moisture conditions at Star City were drier than normal during crop growth, NUE was higher under NT than under CT (Table 6). Similarly, at Beaverlodge in 2006, when growing season rainfall was 36% below the 30-yr mean, NRE were significantly higher under NT than CT although NUE was only slightly higher (P0.065). Generally drier soil under CT than NT probably resulted in lower crop growth and N uptake in dry years. However, in no instance was there a tillagefertilizer N interaction, i.e., the tillage effect was similar for both CRU and urea. IMPLICATIONS AND CONCLUSIONS Tillage system had no influence on crop response to CRU or urea, implying that crop response to the form of urea and its mode of application was largely independent of the tillage system used for soil management. Seed yield and N uptake generally increased with increasing rate of applied N (to 90 kg N ha 1 ). Seed yield and N uptake were mostly lower with fall-banded urea and CRU than with spring-banded urea and CRU, suggesting probable loss of fertilizer N between its soil application in late autumn and seeding the following spring. Compared with urea, applied in spring, CRU resulted in 10% higher crop yields, and in higher N recovery, in 2 of 7 site-years. In those years soil moisture conditions were either wetter than or about normal. Split urea application with half banded at sowing and half broadcast-applied at tillering (or bolting when canola was grown) produced the highest crop yields (and high N recovery) in 3 site-years when applied at commercial rates, but was ineffective one year when drought impaired the effectiveness of the second dose of fertilizer. Split urea application can be a superior risk management method, since growing season conditions are typically evident by the tillering/bolting growth stage, at which time the decision to proceed with extra N fertilizer application can be made. At the one location where it was used, the 50:50 blend of CRU and urea applied at sowing generally produced similar seed yield and NUE as CRU and urea. Seed N concentration was increased most by split application of urea in 4 yr (typically wet or normal ones) but was not affected by the form of urea used. Therefore, split urea application appears to have some advantages over the use of CRU or urea. The lower yield and NRE with urea is believed to be due to higher gaseous or leaching loss of N as compared with controlled-release urea. The findings suggest that spring-banded CRU can increase seed yield and N recovery relative to spring-banded urea on Dark Gray and Gray Luvisolic soils under normal to slightly wetter soil conditions. The main consideration for farmers will be the higher cost of CRU relative to urea; however, a blended mixture of CRU and urea was mostly as effective as CRU at the one site where the Table 6. Effect of tillage on components of nitrogen use efficiency at, and Tillage system 2005 NRE y [kg N (kg N) 1 ] 2005 NPE y [kg seed (kg N) 1 ] 2006 NUE y [kg seed (kg N) 1 ] 2006 seed yield [Mg ha 1 ] 2006 NUE [kg seed (kg N) 1 ] 2006 NRE [kg N (kg N) 1 ] Conventional No tillage SEM x (3 DF) 0.014* 0.31* 0.54* 0.087* 0.56NS 0.013* z Data are averages of different N sources and application rates and methods. y NRE, N recovery efficiency; NPE, N physiological efficiency; NUE, N use efficiency. x SEM, standard error of mean. *Significant tillage effects by F test at P50.05; NS, not significant.

10 372 CANADIAN JOURNAL OF SOIL SCIENCE comparison was available, indicating that the cost factor can be reduced. Another effective N management tool is split application of urea, although the cost of the second application has to be reckoned compared with the potential benefits, which are management of risk associated with mid-summer drought and potentially higher seed protein content. Whether the perceived environmental benefit of CRU is real and measurable also has to be considered in addition to its higher cost: this aspect will be dealt with in a subsequent report. ACKNOWLEDGEMENTS The authors thank GAPS and ETAA programs of AAFC for financial assistance: D. Leach, S. Neighbour, K. Fidyk, K. Hemstad-Falk, C. Nielsen and D. Schick for technical help. We acknowledge Agrium for supplying the fertilizer. Blaylock, A. D., Binford, G. D., Dowbenko, R. D., Kaufmann, J. and Islam, R ESN, controlled-release nitrogen for enhanced N efficiency and improved environmental safety. Pages in Z. Zhu, K. Minami, and G. Xing, eds. 3rd Intern. nitrogen conference, contributed papers Oct Nanjing, China. Science Press USA Inc., Monmouth Junction, NJ. Canola Council of Canada Canola production centre 1998 Report. Pages CCC, Winnipeg, MB. Chen, D., Suter, H., Islam, A., Edis, R., Freney, J. R. and Walker, C. N Prospects for improving efficiency of fertilizer in Australian agriculture: a review of enhanced efficiency fertilizers. Aust. J. Soil Res. 46: Drost, D., Koening, R. and Tindall, T Nitrogen use efficiency and onion yield increased with a polymer-coated nitrogen source. Hortic. Sci. 37: Fan, X. L., Li, F. M., Liu, F. and Kumar, D Fertilization with a new type of coated urea: evaluation for nitrogen efficiency and yield in winter wheat. J. Plant Nutr. 27: Isfan, D Nitrogen physiological efficiency index in some selected spring barley cultivars. J. Plant Nutr. 13: Lafond, G. P Effects of row spacing, seeding rate and nitrogen on yield of barley and wheat under zero-till management. Can. J. Plant Sci. 74: Limon-Ortega, A., Sayre, K. D. and Francis, C. A Wheat nitrogen use efficiency in a bed planting system in northwest Mexico. Agron. J. 92: Malhi, S. S. and Lemke, R. L Tillage, crop residue and N fertilizer effects on crop yield, nutrient uptake, soil quality and greenhouse gas emissions in a second 4-yr rotation cycle. Soil Tillage Res. 96: McKenzie, R. H., Bremer, E., Middleton, A. B., Pfiffner, P. G. and Dowbenko, R. E Controlled-release urea for winter wheat in southern Alberta. Can. J. Soil Sci. 87: Moll, R. H., Kamprath, E. J. and Jackson, W. A Analysis and interpretation of factors which contribute to efficiency of nitrogen utilization. Agron. J. 74: Nelson, K. A., Paniagua, S. M. and Motavalli, P Effect of polymer coated urea, irrigation, and drainage on nitrogen utilization and yield of corn in a claypan soil. Agron. J. 101: Noellsch, A. J., Motavalli, P. P., Nelson, K. A. and Kitchen, N. R Corn response to conventionak and slow-release nitrogen fertilizers across a claypan landscape. Agron. J. 101: Nyborg, M., Malhi, S. S., Solberg, E. D. and Zhang, M. C Influence of polymer-coated urea on mineral nitrogen release, nitrification, and barley yield and nitrogen uptake. Commun. Soil Sci. Plant Anal. 30: Peltonen, J. and Virtanen, A Effect of nitrogen fertilizers differing in release characteristics on quantity of storage protein in wheat. Cereal Chem. 71: 15. SAS Institute, Inc SAS/STAT user s guide. Version 6, 4th ed. Vol. 2. SAS Institute, Inc., Cary, NC. Savant, N. K., James, A. F. and McClellan, G. H Urea release from silicate- and polymer-coated urea in water and a simulated wetland soil. Fert. Res. 4: Shoji, S., Delgado, J., Mosier, A. and Miura, Y Use of controlled release fertilizers and nitrification inhibitors to increase nitrogen use efficiency and to conserve air and water quality. Commun. Soil Sci. Plant Anal. 32: Soon, Y. K. and Arshad, M. A Tillage and liming effects on crop and labile soil nitrogen in an acid soil. Soil Tillage Res. 80: Strong, W. M Effect of late application of nitrogen on the yield and protein content of wheat. Aust. J. Exp. Agric. Anim. Husb. 22: Zhang, M., Nyborg, M., Malhi, S. S. and Solberg, E. D Yield and protein content of barley as affected by release rate of coated urea and rate of nitrogen application. J. Plant Nutr. 23: