Spring wheat and canola response to nitrogen placement with no-till side band openers

Transcription

1 Spring wheat and canola response to nitrogen placement with no-till side band openers A. M. Johnston 1,5, G. P. Lafond 2, G. E. Hultgreen 3, and G. L. Hnatowich 4 1 Potash and Phosphate Institute of Canada, Suite 704 CN Tower, Saskatoon, Saskatchewan, Canada S7K 1J5 ( ajohnstone@ppi-ppic.org); 2 Experimental Farm, Agriculture and Agri-Food Canada, Box 760, Indian Head, Saskatchewan, Canada S0G 2K0; 3 Prairie Agriculture Machinery Institute, Box 1150, Humbolt, Saskatchewan, Canada S0K 4A0; 4 Agronomic Consultant, 238 Emmeline Road., Saskatoon, Saskatchewan, Canada S7J 5B6. Saskatoon Research Station Contribution Received 25 May 2000, accepted 30 August Johnston, A. M., Lafond, G. P., Hultgreen, G. E. and Hnatowich, G. L Spring wheat and canola response to nitrogen placement with no-till side band openers. Can. J. Plant Sci. 81: The development of successful no-till crop production systems has led to the practice of applying all the seed and fertilizer in a single field operation. This study was initiated to assist producers in the selection of commercially available bolt-on side banding openers. Field trials were conducted at 10 locations in Saskatchewan over a 2-yr period (1995 and 1996) to evaluate the performance of five bolt-on side band openers on the establishment and yield of spring wheat (Triticum aestivum L.) and canola (Brasica rapa L.). Trial locations were selected to provide a range of soil and environmental conditions. The openers tested included the Flexi-coil Stealth, Dutch-Vern Eaglebuster, Swede SW470, GEN 200 and Morris Edge-On. Fertilizer nitrogen (N) as urea was applied in the side band at rates of 0, 40, 80 and 120 kg N ha 1 with a side banded starter fertilizer blend of phosphorus, potassium and sulphur. When properly adjusted for individual site soil conditions at seeding, no difference was recorded between the side band openers tested in the establishment and grain yield of spring wheat. Averaged across all N rates, three of the five openers showed poor canola seedling emergence, indicating inadequate seed fertilizer separation. However, the ability of the canola crop to branch and compensate for poor crop establishment prevented any significant grain yield loss in this study. In cases where differences between openers were observed, the Flexi-Coil Stealth and GEN 200 openers provided the best crop establishment. Given the importance of crop establishment to achieving optimum grain yields, the bolt-on side band openers that provided good crop establishment should be recommended to producers. Key words: Canola, fertilizer placement, no-till, openers, wheat Johnston, A. M., Lafond, G. P., Hultgren, G. E. et Hnatowich, G. L Réponse du blé de printemps et de la navette de type canola de printemps à l épandage de l azote en localisation au moyen d organes ouvreurs de bande latérale en régime de semis direct. Can. J. Plant Sci. 81: La mise au point de systèmes satisfaisants de culture sans labour s est accompagnée de la pratique d épandre les semences et les engrais en une seule opération. L objet de nos travaux était d aider les producteurs dans le choix d ouvreurs de bande latérale amovibles actuellement sur le marché. Des essais au champ étaient conduits sur une période de deux ans (1995 et 1996) à dix emplacements en Saskatchewan pour évaluer les performances de cinq ouvreurs de bande latérale amovibles quant à l installation et au rendement du blé de printemps (Triticum aestivum L.) et de la navette de printemps de type canola (Brassica rapa L.). Le choix des emplacements d essai se voulait représentatif d un écart de conditions pédologiques et environnementales. Les ouvreurs évalués étaient le Flexi-coil Stealth MD, le Dutch-Vern Eaglebuster MD, le Swede S W470 MD, le GEN 200 MD et le Morris Edge-On MD. L engrais azoté (N), sous forme d urée, était déposé dans la bande latérale aux doses de 0, 40, 80 et 120 kg N ha -1, en même temps qu un engrais de démarrage P, K et S. En autant qu ils étaient bien réglés pour les conditions de sol à chaque endroit lors du semis, les ouvreurs ne donnaient lieu à aucune différence significative pour ce qui est de l installation et du rendement grainier du blé. Toutes doses de N confondues, trois des ouvreurs produisaient une levée insatisfaisante du canola, résultat d une mauvaise séparation semence-engrais. Toutefois l aptitude de cette culture à se ramifier et ainsi à compenser une levée médiocre a empêché tout manque à produire important de grains. Dans les cas où il y avait des différences dues aux ouvreurs, c est le Flexi-coil Stealth MD et le GEN 200 MD qui procuraient la meilleure installation. Vu l importance de la densité de peuplement pour l obtention de rendements grainiers optimaux, la préférence des producteurs devrait être dirigée vers les ouvreurs qui ont fourni les meilleurs taux de levée. Mots clés: Canola, épandage en localisation de l engrais, semis direct Conservation tillage, or no-till, seeding systems have seen rapid adoption on the Canadian prairies over the past few years. The census of agriculture reported that 28% of all annual crop land in Alberta, Saskatchewan and Manitoba was seeded without preseeding tillage in 1996 (Statistics Canada 1996). This expansion can be attributed largely to 191 the development of seeding equipment capable of providing good seed to soil contact under heavy residue conditions and a reduction in the cost of nonselective herbicides used in place of tillage for weed control. The majority of producers adopting no-till seeding systems are interested in a onepass seeding and fertilizer application, requiring the modi-

2 192 CANADIAN JOURNAL OF PLANT SCIENCE Table 1. Location, year, soil characteristics, residual soil nitrate-n, seeding date, soil moisture and growing season conditions for bolt-on side band opener study in Saskatchewan Spring soil NO 3 -N (kg ha 1 ) to 60 cm Seeding date Spring soil Growing Location Year Soil zone and texture Wheat Canola (month/day) moisture z conditions y Indian Head 1995 Black Chernozem Heavy Clay NC NC 30 May 1 June 35.3 average Melfort 1995 Black Chernozem Clay Loam May 29.4 good Tisdale 1995 Dark Gray Luvisol Clay May 26.3 poor Watrous 1995 Dark Brown Chernozem Clay Loam May 28.4 average Yorkton 1995 Black Chernozem Clay Loam June 27.8 poor Indian Head 1996 Black Chernozem Indian Head Heavy Clay June 30.5 good Melfort 1996 Black Chernozem Clay Loam May 33.0 good Tisdale 1996 Dark Gray Luvisol Clay May 26.9 poor Regina 1996 Dark Brown Chernozem Heavy Clay NC NC 1 3 June 29.6 good Watrous 1996 Dark Brown Chernozem Clay Loam May NA average z Soil moisture (%) in surface 0.10 m at seeding. y Growing conditions: good no significant moisture or temperature stress during growing season; average some moisture or temperature stress; poor both moisture and temperature stress during growing season. NC = not collected. NA = not available. fication of fertilizer rates or seeding openers to safely apply fertilizer with or away from the seed. Previous research with fertilizer placement at seeding has identified site-specific conditions that should be considered (Deibert 1994; Harapiak 1994). While the concept of crop production without preseeding tillage as an effective means of conserving both soil and moisture has been well established, the design of seed fertilizer openers that meet a wide range of field, soil moisture and crop residue conditions encountered has been a limitation to the successful adoption of one-pass seeding and fertilizer application (Frye and Lindwall 1986). Producers expect that any single seeding opener is adapted to all conditions; however, field experience has shown this not to be the case. Where clay and silty clay soil textures are found, the retention of moisture under surface crop residues can often result in excessive soil disturbance by many openers. This results in uneven seedbed conditions, particularly when using openers that side band the fertilizer at seeding. When soil flow around the openers is influenced by moisture conditions, there is a possibility that the placement of seed and fertilizer in distinctly separate bands may be jeopardized. It has been suggested that the evaluation of seeding openers should be focused on crop establishment and early season plant development as this can influence crop yield potential (Chevalier and Ciha 1986). Compared with broadcast applications, fertilizer placement under the surface residue of no-till fields and below the seed can effectively reduce fertilizer N immobilization and increase N uptake, recovery and efficiency (Carter and Rennie 1984; Malhi and Nyborg 1992). Spring crops have been shown to respond with rapid growth when they have access to nutrients soon after emergence (Klepper et al. 1983). Band placement of fertilizer, particularly phosphorus, near the seed row allows for early access by the seedling lateral root system. Placement of high rates of N fertilizer in the seed row can reduce crop stand establishment and crop yields (Deibert et al. 1985; Deibert 1993). While increasing the spread between seed and fertilizer in the seed row with cultivator sweeps reduces this stand damage, it results in higher soil disturbance, greater loss of plant-available water (Brandt 1992; Lafond et al. 1992) and increased weed growth (Kirkland 1993). This study was initiated to determine the effect of five commonly used, commercially available, no-till bolt-on side banding openers and various N rates on spring wheat and canola establishment and grain yield when grown under a range of environmental conditions in Saskatchewan. MATERIALS AND METHODS Five side banding bolt-on openers were compared under direct seeded conditions at five locations in both 1995 and 1996 in the Dark Brown, Black and Gray soil zones of Saskatchewan (Table 1). Trial locations were selected to provide a range of soil textures and climatic conditions. The openers evaluated in the study were all single side band types (not paired row), and included: 1) Flexi-coil Stealth, 2) Dutch-Vern Eaglebuster, 3) Swede SW470, 4) GEN 200, 5) Morris Edge-On (Fig. 1). These openers were selected because they were the most commonly used by

3 JOHNSTON ET AL. CROP RESPONSE TO NO-TILL SIDE BAND OPENERS 193 Fig. 1. Bolt-on side band openers a) Dutch-Vern Eaglebuster ; b) GEN 200 ; c) Flexi-Coil Stealth ; d) Morris Edge-On Mount ; and e) Swede SW 470. farmers at the time of the study. With the exception of the Swede, all of the openers placed the seed to the side and above the fertilizer, which was located in the center of the shank. In contrast, the Swede opener placed the seed in the center of the shank and the fertilizer to the side. With the exception of the GEN 2000 opener, a seed brake (air release on delivery tube immediately before the opener) was used with each opener to reduce seed velocity immediately above the opener and minimize seed bounce due to air velocity. Use of the seed brake with the GEN 2000 opener resulted in plugging with seed. All seeding was conducted at approximately 7 km h 1 using a 3.0-m plot seeder with 0.3 m row spacing. On-row packing was achieved using 30 cm framemounted pneumatic packing wheels on the back of the seeder, adjusted to pack over top of the seed row with a down pressure of 50 kg per wheel. The target seeding depths for the study were 50 mm or less for wheat and 25 mm or less for canola. Adjustments prior to the seeding operation insured that each opener achieved a similar seeding depth. Plots were 3.0 m by 15.2 m in size. Fertilizer nitrogen (N) was side band applied at rates of 0, 40, 80 and 120 kg N ha 1, using urea (46-0-0). In addition, all plots received a side band application of 25 kg P 2 O 5 ha 1 as mono-ammonium phosphate, 11 kg K 2 O ha 1 as potassium chloride and 11 kg SO 4 -S ha 1 as ammonium sulphate. Actual N rates were adjusted for the N in the mono-ammonium phosphate and ammonium sulphate. The canola (Brasica rapa) cv. Maverick and spring wheat (Triticum aestivum L.) cv. Pasqua were seeded at 6.7 and 134 kg ha 1, respectively. The canola seed was treated with a seed fungicide/insecticide and blended with an equal amount of granulated insecticide (5% carbofuran). Weeds were controlled at each test location using a variety of herbicides. Soil water ( m; gravimetrically) and soil nitrogen ( m) were determined immediately prior to seeding. Crop establishment was measured by counting the number of seedlings in 2 rows 1 m at d post-emergence. At the four- to six-leaf stage, a total of 20 spring wheat seedling samples were collected from four locations in each plot for determination of seeding depth (distance from seed to chlorophyll) and Haun leaf stage (Haun 1973). At harvest, seed yield was determined by harvesting an area of 19 m 2 with a small plot combine. Seed protein was determined by NIR for seven of the 10 test locations, while data were not collected at the remaining three locations. Experimental design was a factorial arrangement of the five openers and four N rates with four replicates. The canola and wheat trials were analyzed as separate experiments. Data from locations were combined and analyzed using GLM (SAS, Institute, Inc.1985). Main effect differences in openers were evaluated using LSD 0.05, while N response main effects were evaluated using orthogonal contrasts. RESULTS AND DISCUSSION Trial Environmental Conditions Soil moisture conditions at seeding were good at all trial locations (Table 1). Residual soil N levels were high at sev-

4 194 CANADIAN JOURNAL OF PLANT SCIENCE Table 2. Probability levels and main effect means for canola and wheat response to bolt-on side banding openers from a combined analysis over 10 locations in Saskatchewan in 1995 and 1996 Canola Wheat Plant stand Seed yield Seed protein z Plant stand Haun stage Seeding depth Seed yield Seed protein Location (Loc) ** y ** ** ** ** ** ** NS Opener (Op) NS NS NS NS NS NS NS NS N Rate (N) ** ** * * NS * ** ** Opener N ** NS NS NS ** NS NS NS Loc Opener ** ** NS ** ** ** NS NS Loc N rate * ** ** NS NS ** ** ** Loc Op N NS NS NS NS NS NS NS NS CV Opener (seedlings m 2 ) (kg ha 1 ) (%) (seedlings m 2 ) (Haun) (mm) (kg ha 1 ) (%) Flexi-Coil Morris Gen Swede Dutch LSD 0.05 NS NS NS NS NS NS NS NS N rate (kg ha 1 ) SE N rate contrasts Linear ** ** ** ** NS ** ** ** Quadratic NS NS NS NS NS NS NS NS Cubic NS NS NS NS NS NS NS NS z Seed protein values are a mean of seven trials. Data were not collected at Indian Head in 1995 and 1996, or at Regina in y Levels of probability indicated by *, ** and NS are significant at P = 0.05, P = 0.01 and not significant, respectively. eral of the locations and as a result influenced the grain yield response to added N. Seeding of the trials required several days and rainfall extended this period at Watrous in Growing conditions were average to good at seven of the 10 test locations, with the Tisdale site in 1995 and 1996 and Yorkton in 1995 reporting poor growing season precipitation. Wheat Response to Opener and N Rate Increased rates of side banded N reduced wheat seedling numbers; however, the reduction amounted to only 4% when averaged across all trials (Table 2). This supports previous reports by Johnston et al. (1997) showing that increased rates of either urea or anhydrous ammonia in the side band reduced wheat seedling numbers. Differences in seedling stands among locations were large, given that all trials were seeded using the same seeder, seed lot and seeding rate (Table 3). A dry seedbed in 1995 at Watrous, Melfort, Tisdale and Yorkton resulted in poor seedling stands. Rain immediately prior to seeding at Indian Head improved wheat seedling emergence at this location in These results illustrate the impact that soil moisture conditions at seeding can have on seedling emergence and potentially final grain yield. Wheat seedling development, as influenced by opener design and N rate, was assessed by determining Haun stage of the seedling at the four- to six-leaf stage of development (Haun 1973). A significant (P < 0.05) opener by N rate interaction for Haun stage revealed that, while most openers showed no effect or a gradual improvement with increasing N rate, leaf numbers declined for the Morris opener (Fig. 2). While the differences between N rates were minor, there was a definite trend to delayed wheat seedling development as side banded N rate increased. However, the relatively poor performance of the GEN 2000 opener at Melfort and Watrous in 1995, where delayed seedling development was recorded, should be noted. In general, the effect of opener and N rate were minor on early wheat seedling development, as measured by Haun stage. Depth of seeding was determined on the seedlings collected for Haun stage evaluation. Reduced seeding depth was associated with increased N rates (Table 2); however, the impact of increasing N rate on seeding depth seemed to be site and year specific (Table 3). At Melfort and Yorkton in 1995, and at Indian Head and Regina in 1996, increasing N rate resulted in emerged seedlings coming from a shallower seeding depth. All other locations showed no difference in seeding depth as N rate increased. Given the reduction in seedling numbers with increasing N rate, it would appear that those seeds well separated from the N band, and in turn closer to the soil surface, were the ones that emerged for evaluation (Deibert et al. 1985; Deibert 1993). This could explain some of the variations in Haun

5 JOHNSTON ET AL. CROP RESPONSE TO NO-TILL SIDE BAND OPENERS 195 Table 3. Wheat seedling stand, Haun stage, seeding depth and seed yield response to opener and N rate by location for bolt-on side band openers at 10 locations in Saskatchewan in 1995 and 1996 Indian Indian Head-95 Melfort-95 Tisdale-95 Watrous-95 Yorkton-95 Head-96 Melfort-96 Regina-96 Tisdale-96 Watrous-96 Opener Seedlings (plants m 2 ) Flexi-Coil Morris Gen Swede Dutch LSD Opener Haun stage Flexi-Coil Morris Gen Swede Dutch LSD Opener Seeding depth (mm) Flexi-Coil Morris Gen Swede Dutch LSD N rate (kg ha 1 ) SE N rate (kg ha 1 ) Seed yield (kg ha 1 ) SE N rate (kg ha 1 ) Seed protein (%) 0 NC NC 13.2 NC SE NC = data not collected. stage recorded between openers. Significant (P < 0.05) interactions were recorded between both opener and N rate with trial location. When considered across locations, the Swede opener was found to have the shallowest seeding depth, while the Dutch and Flexi-Coil openers had the deepest seed placement (Table 3). While the Dutch opener showed the deepest seed placement in most years, it was found to be placing seed the shallowest at the Regina and Indian Head heavy clay soil sites in These results indicate that once set, some openers were easier to maintain at the desired seeding depth. Nitrogen rate, and its interaction at the various trial locations, were the only factors influencing seed yield (Table 2). Despite opener and N rate effects on seedling establishment, plant densities were not reduced enough to affect seed yield. While increased N rate increased wheat seed yield in all trials, the response ranged from a low of 17% with high residual N at Melfort in 1995, to a high of 141% at Regina in 1996 (Table 3). This variability in N rate response across trial locations was principally due to soil residual N levels; however, it was also confounded by growing season conditions (Table 1). Seed protein showed a positive response to increasing N rate, with an average 2.6% increase in wheat protein between the check and 120 kg N ha 1 rate (Table 2). A significant interaction between trial location and N rate for seed protein was recorded, reflecting the variability in the range of response recorded (Table 3). While seed protein for

6 196 CANADIAN JOURNAL OF PLANT SCIENCE the check ranged by only 1.5% between trials, the combined influence of residual soil N and environmental conditions resulted in protein with the highest N rate ranging by 2.7%. Canola Response to Opener and N Rate Canola seedling emergence showed a larger effect of both opener and fertilizer N rate than was recorded with spring wheat (Fig. 3). Increasing N rate reduced canola seedling stand by 15%, with the main effect reduction due mainly to the Morris, Swede and Dutch openers. These plant stand reductions indicate inadequate seed and fertilizer separation, with stand reductions of 30, 25 and 19% for the Morris, Swede and Dutch openers, respectively. Increasing N rate with the Flexi-Coil and GEN 200 openers had little or no effect on canola seedling establishment, indicating good seed fertilizer separation. A significant (P < 0.05) location by opener and location by N rate interaction was recorded for seedling stand, a reflection of large variability between the openers at the trial locations (Tables 2 and 4). As an example, while the Morris opener performed poorly on average across locations, it provided equivalent canola seedling emergence to the Flexi-Coil opener at five of the 10 trial locations. Where the Morris opener s performance was poorer (Yorkton in 1995, and Indian Head, Regina, Tisdale and Watrous in 1996), the impact on seedling stand was large. With the exception of Yorkton in 1995 and Watrous Fig. 2. Mean wheat Haun stage in response to bolt-on side band opener and N rate at 10 locations in Saskatchewan in 1995 and Fig. 3. Mean canola seedling emergence in response to bolton side band opener and N rate at 10 locations in Saskatchewan in 1995 and in 1996, increasing N rate resulted in a 10 25% decline in canola seedling stand. These results indicate that for evaluation of the bolt-on openers, seedling counts were a better indicator of adequate seed to fertilizer separation in canola than spring wheat. Canola seed yield showed a 38% yield increase with increasing side banded N rate (Table 2). When considered across locations, the yield response to N ranged from no response at Melfort in 1995 to a 218% increase at Regina in 1996 (Table 4). Only at Melfort in 1995, with high soil residual N (Table 1) was there no seed yield response to fertilizer N recorded. Seed yield response varied with opener type at five of the 10 trial locations (Table 4). While the Flexi-Coil opener had either the highest yield, or was grouped with the openers showing the highest yield, there were no other consistent responses with the remaining four openers. The branching nature of the canola crop allowed the inferior crop establishment of the Morris, Swede and Dutch openers to compensate and provide similar final seed yields. Canola seed protein showed a positive linear response to increased N rate when considered across trial locations (Table 2). A significant (P < 0.05) interaction with location revealed that at six of the seven trials increased N rate increased canola seed protein, while at Melfort in 1995, we recorded a decline in seed protein (Table 4). While yields

7 JOHNSTON ET AL. CROP RESPONSE TO NO-TILL SIDE BAND OPENERS 197 Table 4. Canola seedling stand and grain yield response to opener and N rate by location for bolt-on side band openers at 10 locations in Saskatchewan in 1995 and 1996 Indian Indian Head-95 Melfort-95 Tisdale-95 Watrous-95 Yorkton-95 Head-96 Melfort-96 Regina-96 Tisdale-96 Watrous-96 Opener Seedlings (plants m 2 ) Flexi-Coil Morris Gen Swede Dutch LSD N rate (kg ha 1 ) SE Opener Seed yield (kg ha 1 ) Flexi-Coil Morris Gen Swede Dutch LSD N rate (kg ha 1 ) SE N rate (kg ha 1 ) Seed protein (%) 0 NC NC 20.5 NC SE NC = data not collected. were generally the highest at the Melfort location, we are at a loss to explain the decline in seed protein at this site. At Yorkton, under similar soil residual N levels, a slight increase in seed protein and seed yield with increasing N rate was recorded. CONCLUSION The development by manufacturers, and selection by producers, of bolt-on side band openers for direct seeding or no-till seeding is critical to ensuring precise seed and fertilizer placement in one-pass seeding and fertilizing systems. When properly adjusted for individual site soil conditions at seeding, all of the openers evaluated in this research were found to provide adequate seedling stands and had no effect on final seed yield of wheat. However, with canola and its higher sensitivity to fertilizer N placement, we found large differences in the affect of opener design on crop establishment. The canola seedling establishment data indicated that the Flexi-Coil and GEN 200 single side band openers provided the best crop establishment across a range of N rates. The branching nature of canola compensated for the inferior crop establishment with the Morris, Swede and Dutch openers, resulting in few seed yield differences at harvest. Where differences between openers were observed, the Flexi-Coil and GEN 200 opener provided the best crop establishment. Given the importance of crop establishment to achieving optimum grain yields and better competitiveness against early weed growth, the bolt-on side band openers that provide good crop establishment and consistent long-term performance with physical wear should be selected by producers. Consistent performance of one-pass seeding and fertilizing openers becomes particularly important when high rates of N are used, especially when the N is applied as urea or anhydrous ammonia. Brandt, S. A Zero vs. conventional tillage and their effects on crop yield and soil moisture. Can. J. Plant Sci. 72: Carter, M. R. and Rennie, D. A Crop utilization of placed and broadcast 15 N-urea fertilizer under zero and conventional tillage. Can. J. Soil Sci. 64: Chevalier, P. M. and Ciha, A. J Influence of tillage on phenology and carbohydrate metabolism of spring wheat. Agron. J. 78:

8 198 CANADIAN JOURNAL OF PLANT SCIENCE Deibert, E. J Spring wheat response to seed spreader patterns and deep band fertilizer placement with an air seeder. J. Prod. Agric. 6: Deibert, E. J Fertilizer application with small grain seed at planting. EB-62, NDSU Extension Service, North Dakota State University, Fargo, ND. Deibert, E. J., Lizotte, D. A. and Bock, B. R Wheat seed germination as influenced by fertilizer rate, fertilizer source, and spreader type with one-pass pneumatic seeding-fertilizing. North Dakota Farm Res. 42 (6): Harapiak, J.T Evaluating fertilizer management options. Pages in 37th Annual Manitoba Soil Science Meeting, 4 5 January Dept. of Soil Science, University of Manitoba, Winnipeg, MB. Haun, J. R Visual qualification of wheat development. Agron. J. 65: Johnston, A. M., Lafond, G. P., Harapiak, J. T. and Head, W. K No-till spring wheat and canola response to side banded anhydrous ammonia at seeding. J. Prod. Agric. 10: Kirkland, K. J Weed management in spring barley (Hordeum vulgare L.) in the absence of herbicides. J. Sustainable Agric. 3: Klepper, B., Rasmussen, P. E. and Richman, R. W Fertilizer placement for cereal root access. J. Soil Water Cons. 38: Lafond, G. P., Loeppky, H. and Derksen, D. A The effects of tillage systems and crop rotations on soil water conservation, seedling establishment and crop yield. Can. J. Plant Sci. 72: Frye, W. W. and Lindwall, C. W Zero-tillage research priorities. Soil Tillage Res. 8: Malhi, S.S. and Nyborg, M Placement of urea fertilizer under zero and conventional tillage for barley. Soil Tillage Res. 23: SAS Institute, Inc SAS user s guide. Statistics. Version 5. SAS Institute, Inc., Cary, NC. 957 pp. Statistics Canada Census of Agriculture: Saskatchewan highlights. [Online] Available: