Effect of form, placement and rate of N fertilizer, and placement of P fertilizer on wheat in Saskatchewan

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1 Effect of form, placement and rate of N fertilizer, and placement of P fertilizer on wheat in Saskatchewan S. P. Mooleki 1, S. S. Malhi 2, R. L. Lemke 3, J. J. Schoenau 4, G. Lafond 5, S. Brandt 6, G. E. Hultgreen 7, H. Wang 8, and W. E. May 5 Can. J. Plant Sci. Downloaded from by on 5/8/18 1 Saskatchewan Ministry of Agriculture, Agriculture Knowledge Centre, 45 Thatcher Dr. E., Moose Jaw, Saskatchewan, Canada S6J 1L8 ( patrick.mooleki@gov.sk.ca); 2 Agriculture and Agri-Food Canada, P.O. Box 124, Melfort, Saskatchewan, Canada SE 1A; 3 Agriculture and Agri-Food Canada, 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8; 4 Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5A8; 5 Agriculture and Agri-Food Canada, P.O. Box 76, Indian Head, Saskatchewan, Canada SG 2K; 6 Agriculture and Agri-Food Canada, P.O. Box 1, Scott, Saskatchewan, Canada SK 4A; 7 Prairie Agricultural Machinery Institute, P.O. Box 115, Humboldt, Saskatchewan, Canada SK 2A; and 8 Semiarid Prairie Agricultural Research Centre, P.O. Box 13, Swift Current, Saskatchewan, Canada S9H 3X2. Received 2 May 29, accepted 13 January 21. Mooleki, S. P., Malhi, S. S., Lemke, R. L., Schoenau, J. J., Lafond, G., Brandt, S., Hultgreen, G. E., Wang, H. and May, W. E. 21. Effect of form, placement and rate of N fertilizer, and placement of P fertilizer on wheat in Saskatchewan. Can. J. Plant Sci. 9: On the Canadian prairies, the one-pass seeding and fertilizing no-till system is very common. However, the close proximity of the fertilizer to the seed can cause damage to the emerging seedlings due to a combination of a salt effect and/or ammonia toxicity. Manufacturers have responded by developing openers that allow placement of seed and fertilizer in separate bands. A 3-yr study was initiated in 2 to determine the effect of nitrogen (N) form [urea (U) and anhydrous ammonia (AA)], placement [broadcast (Br), side-band (SB) or mid-row band (MRB)], timing (fall or spring) and rate (to 9or 12kg N ha 1 ), and phosphorus (P) placement (7 to 1kg P ha 1 ) on plant density, seed and straw yield, seed protein content, and N uptake of spring wheat (Triticum aestivum L.) under no-till at four sites representing different agro-ecological zones in Saskatchewan. Rate of applied N had the most dominant effect on agronomic variables, while form, placement, and timing of application of N had minor effects. Generally, SB and MRB were comparable in terms of seed yield, N uptake and seed protein content. From a practical perspective, SB and MRB could be used with equal success with either U or AA. Side banding P produced responses similar to seed-placed P, except under very dry conditions where side banding was superior. In general, placement of urea in soil in a band was more effective than broadcasting, while fall banding can be less effective than spring banding. Key words: Anhydrous ammonia, N application timing, N form, N and P placement, N uptake, protein content, urea, wheat, yield Mooleki, S. P., Malhi, S. S., Lemke, R. L., Schoenau, J. J., Lafond, G., Brandt, S., Hultgreen, G. E., Wang, H. et May, W. E. 21. Incidence du type, de la me thode de placement et du taux d application des engrais N ainsi que de la méthode de placement des engrais P sur la culture du blé en Saskatchewan. Can. J. Plant Sci. 9: Dans les Prairies canadiennes, on recourt couramment a` la technique qui consiste à semer et à fertiliser en un seul passage, sans travail du sol. Cependant, la proximite de l engrais et de la graine peut causer des dommages aux plantules, consécutivement a` la salinisation du sol ou a` la toxicite de l ammoniaque, ou les deux. Les fabricants y ont remédie en cre ant des socs permettant de placer les graines et l engrais dans des bandes distinctes. En 2, les auteurs ont entrepris une étude de trois ans pour ve rifier l incidence du type d engrais azoté (N) (ure e et ammoniac), de la me thode de placement [à la volée, en bande late rale (BL) ou en bande a` mi-rang (BMR)], du moment de la fertilisation (automne ou printemps) et du taux d application (à 9ou 12kg de N par hectare), ainsi que de la me thode de placement du phosphore (P) (7 a` 1kg de P par hectare) sur la densite du peuplement, le rendement en grain et en paille, la teneur en prote ines de la graine, et l absorption de N par le blé de printemps (Triticum aestivum L.) sans travail du sol, a` quatre sites repre sentatifs des diffe rentes écozones agricoles de la Saskatchewan. Le taux d application a l effet le plus marque sur les variables agronomiques, tandis que le type d engrais, la me thode de placement et le moment de l application n ont que des effets mineurs. En ge ne ral, les me thodes BL et BMR donnent des re sultats comparables pour le rendement grainier, l absorption du N et la teneur en prote ines du grain. Sur le plan pratique, on pourrait recourir aux deux me thodes et obtenir un succe` s identique avec de l urée ou de l ammoniac. Le placement d engrais P en bande late rale entraîne une re action similaire au placement de l engrais avec la semence, sauf par Abbreviations: AA, anhydrous ammonia; Br, broadcast; MRB, mid-row band; SB, side-band; U, urea 319

2 32 CANADIAN JOURNAL OF PLANT SCIENCE temps tre` s sec, ou` la premie` re me thode donne de meilleurs re sultats. Dans l ensemble, le placement d ure e en bande s ave` re plus efficace qu une application à la volée, tandis que la fertilisation à l automne donne de moins bons résultats qu une fertilisation au printemps. Mots clés: Ammoniac, moment d application des engrais N, type d engrais N, placement des engrais N et P, absorption de N, teneur en prote ines, ure e, ble, rendement Can. J. Plant Sci. Downloaded from by on 5/8/18 Proper nutrient management is critical for crop production in western Canada. It entails adopting techniques that improve the efficiency of crop utilization of nutrients and moisture while preserving the soil from degradation (Lafond et al. 1992). The two most limiting nutrients in the Canadian prairies are nitrogen (N) and phosphorus (P). Placement, timing and rate of N application are some of the factors that impact the efficient utilization of N. With the increasing adoption of reduced tillage (Johnston and Jensen 25; Lafond et al. 26), fertilizer application methods need to minimize soil surface disturbance. Although surface broadcasting involves no soil disturbance, it often results in poor nutrient utilization efficiency and crop performance. Placing fertilizer N in the soil effectively reduces volatilization and immobilization, and increases N uptake, recovery and efficiency (Malhi and Nyborg 1992; Malhi et al. 1996). As a result of the desire to increase efficiency and conserve soil and water, one-pass seeding and fertilizing systems have developed where the seed and fertilizer are applied in the same field operation in separate bands. This is because placement of high rates of N and P fertilizer in the seed row can reduce crop stand establishment and crop yields (Deibert 1993). A number of openers and toolbar configurations are available that place the fertilizer away from the seed in a separate furrow. Side-banding (SB) the fertilizer to the side and below the seed row is an efficient method of placement (Malhi and Nyborg 1992) and has been shown to increase the competition of crops against certain weeds (O Donovan et al. 1997). Johnston et al. (1997) showed that with adequate seed and fertilizer separation, crop yield of wheat increased with increasing rates of SB anhydrous ammonia (AA) and urea (U). Conversely, if seed-fertilizer separation is not maintained severe problems with crop emergence can occur (Johnston et al. 21). Furthermore, depending on the shape of the opener, SB can cause excessive soil disturbance where the seed is placed, increasing the potential for soil drying and improper seed to soil contact. A mid-row band (MRB) system can also be employed, where fertilizer is banded with an additional opener that is placed midway between every second seed opener. This ensures a safe separation of seed and N fertilizer, and allows for very low disturbance openers to be used for seed placement. However, it also requires certain fertilizers, such as phosphorus, to be placed with the seed, which can increase the potential for seedling injury. Access to nutrients soon after emergence has been shown to enhance rapid growth early in the spring (Klepper et al. 1983). Band placement of fertilizer near the seed row allows for early access by the seedling s lateral root system. The additional distance of the fertilizer from the seed row in MRB systems could potentially affect N availability early in the season, especially under dry soil moisture conditions. Information is lacking on the relative performance of SB and MRB systems under Canadian prairie conditions. Also lacking is the comparison of the effect of form of N (U or AA) under these two systems and how wheat may respond to rate of N application under various combinations of these timings and placements. The objective of this study was to determine the influence of form, placement, timing and rate of N fertilizer and phosphorus (P) placement method on plant density, seed and straw yield, seed protein content, and N uptake in seed and straw of spring wheat (Triticum aestivum L.), flax (Linum usitatissimum L.) and canola (Brassica napus L.) under different soilclimatic conditions in Saskatchewan. Previous papers discussed the effects of these factors on flax (Malhi et al. 28) and canola (Lemke et al. 29). This paper discusses the effects on wheat. MATERIALS AND METHODS Field Experimentation Field experiments were established at four locations in Saskatchewan. Experimental sites included Indian Head (Black Chernozem soil Udic Boroll), Melfort (Dark Gray Luvisol soil Mollic Cryoboralf), Swift Current (Brown Chernozem soil Aridic Boroll), and Scott (Dark Brown Chernozem soil Typic Boroll). For information on soil characteristics for each site see Lemke et al. (29). At each site, 17 treatments were arranged in a randomized complete block design (RCBD) with four replicates. Plot dimensions were 3.1 m 9.2 m with a.3 m boundary between each plot. Seed row openers were located at 25 cm spacing using a Flexi-Coil Stealth opener (Anonymous 26a) for the side-banded treatments, and Bourgault knives with Bourgault mid-row banding coulters placed between every second set of knives (Anonymous 26b) for the mid-row banded treatments. The Flexi-Coil Stealth openers placed the seed about 2.5 cm above and 2.5 cm to the side of the fertilizer, with a wing

3 MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 321 Can. J. Plant Sci. Downloaded from by on 5/8/18 designed to force soil into the fertilizer trench, to ensure better separation from the seed. On-row packing with V-shaped packers was done in all the treatments. Treatments were applied to the same plot every year, but the crops were rotated each year, with wheat grown on canola stubble, flax grown on wheat stubble and canola grown on flax stubble. This paper focuses on the effect of the above-mentioned treatments on spring wheat. For the effects on flax refer to Malhi et al. (28) and for the effects on canola refer to Lemke et al. (29). A blanket application of potassium sulphate was broadcast prior to seeding at all sites to ensure sufficiency of potassium (K) and sulphur (S) nutrients. The sites received P fertilizer (monoammonium phosphate) at rates of 7 kg P ha 1 at Scott and Swift Current, and 1kg P ha 1 at Melfort and Indian Head. These are typical rates used in the respective regions when producers do not resort to soil testing. Nitrogen fertilizer rates were check (no N fertilizer applied, but the P fertilizer contained 4 kg N ha 1 at Scott and Swift Current and 5 kg N ha 1 at Melfort and Indian Head), three N rates (.5x, 1.x and 1.5x, where x typical N rate). The typical rate was 8kg N ha 1 at Melfort and Indian Head, and 6kg N ha 1 at Swift Current and Scott. Typical rates referred to in this study are those typical for the areas. Phosphorus was placed with the seed in all cases, except for the SB_U treatments, where both N and P were placed together in the side-band. An additional SB_U treatment at the 1.x N rate with seedplaced P was included for comparative purposes. At Melfort, Swift Current and Scott, a check treatment seeded with the MRB implements was included, but with no N added. Spring wheat (AC Barrie in 2 and 21 and AC Eatonia in 22) was seeded at 134 kg ha 1 for Indian Head and Melfort, and 9kg ha 1 for Scott and Swift Current following recommended seeding rates for these areas. Higher seeding rates are typically used in the more moist climatic areas (Indian Head and Melfort) than in the drier areas (Scott and Swift current). The crop was no-tilled into standing stubble using a 3-m, four-tank pneumatic plot drill configured to apply either AA or U in addition to seed and P. Herbicides were used in all plots to control weeds as required using recommended rates, products and timings. Plant density was measured on 1-m row lengths from two positions in each plot 2 3 wk after emergence. Total biomass was determined at maturity on all plots by collecting two half-meter row lengths by hand from two positions in each plot. The samples were bulked, dried at568c, and weighed. Seed yield at crop maturity was determined by harvesting five rows in the centre of each plot using a plot combine. Moisture content of the seed samples was determined and the mass of all samples was normalized to a standard moisture content of 14.5%. Grab samples of straw were collected from behind the combine. The straw grab samples were dried, ground and analyzed for N content used for determining N uptake in the straw. Representative seed and straw samples were ground and analysed for total N using hot sulphuric acid-hydrogen peroxide digest to convert all N to ammonium, followed by colorimetric measurement of the ammonium (Thomas et al. 1967). To ensure quality control in analysis, a certified reference material of known N concentration was included in each batch of 4digests for comparison purposes, along with a glycine standard to check for recovery of organic N, and a blank to determine if any contamination was present in the digestion procedure. The total N (%) was multiplied by 5.7to calculate protein content (%) in seed (Williams et al. 1998). Nitrogen uptake in seed and straw was determined by multiplying seed yield or straw yield by the concentration of total N content in seed and straw, respectively. Statistical Analysis Analysis of variance was conducted over the 12 siteyears as described in previous papers (Malhi et al. 28; Lemke et al. 29). In the combined analysis, site-year, replication and their interactions with fixed factors, were considered as random effects while treatments were considered as fixed effects. For details in the structure of the ANOVA, the reader is referred to these two papers. With reference to Table 1, treatments were grouped into five groups as follows: 1. Fertilizer rate: a.. of typical rate Treatments 16, and 18. b..5 of typical rate Treatments 1, 4, 9, and 12. c. 1.of typical rate Treatments 2, 5, 1, and 13 d. 1.5 of typical rate Treatments 3, 6, 11, and Method of fertilizer application: a. Side-band (SB) Treatments 1, 2, 3, 9, 1, and 11. b. Mid-row-band (MRB) Treatments 4, 5, 6, 12, 13, and Form of fertilizer: a. Urea (U) Treatments 1, 2, 3, 4, 5, and 6. b. Anhydrous ammonia (AA) Treatments 9, 1, 11, 12, 13 and Timing of fertilizer application: a. Fall-banding (FB) Treatments 7 and 15. b. Spring side banding (SB) Treatments 1 and Phosphorus fertilizer application: a. Side-banded P (SB-P) Treatment 2. b. Seed-Placed P (SP-P) Treatment 17. Due to the complexity of this study, treatment combinations as shown above were selected to provide

4 322 CANADIAN JOURNAL OF PLANT SCIENCE Can. J. Plant Sci. Downloaded from by on 5/8/18 Table 1. Treatment combinations applied at each of the four experimental sites in Saskatchewan No. Treatment Fertilizer/ placement/time Ratio of typical N rate z Placement of P fertilizer y 1 Urea P side-band.5 SB 2 Urea P side-band 1.SB 3 Urea P side-band 1.5 SB 4 Urea mid-row-band.5 SP 5 Urea mid-row band 1.SP 6 Urea mid-row band 1.5 SP 7 Urea fall band 1.SP 8 Urea spring broadcast 1.SP 9 AA side-band x.5 SP 1AA side-band 1. SP 11 AA side-band 1.5 SP 12 AA mid-row band.5 SP 13 AA mid-row band 1.SP 14 AA mid-row band 1.5 SP 15 AA fall band 1.SP 16 Check (side-band). SP 17 Urea side-band 1.SP 18 Check (mid-row-band). SP z Typical N rate: Indian Head and Melfort8kg N ha 1 ; Swift Current and Scott6kg N ha 1. y SBside-banded P, with N; SPSeed-placed P. x AAanhydrous ammonia. answers to specific questions (Nogueira 24; Grant et al. 23) and analysed using Proc Mixed Procedure of SAS software (Littell et al. 1996) with the Kenward- Rodger degree of freedom method (Kenward and Roger 1997). Differences were declared significant using the Tukey-Kramer Test at a.5 level (Sall et al. 25). Homogeneity of residuals was tested using Levene s test (Littell et al. 26). Normality was tested using Proc UNIVARIATE in SAS software (SAS Institute, Inc. 24). The Shapiro-Wilk W test was used in testing the normality (Shapiro and Wilk 1965). Homogeneity of residuals and normality were found to be acceptable. Linear and quadratic effects of rate of N applied in different forms and placements were determined by Total monthly precipitation (mm) polynomial contrasts. Note that MRB check was only included at Melfort, Swift Current and Scott. Hence, at Indian Head, treatment 16 was used as a check for both SB and MRB trend comparisons. Significance in the text refers to PB.5. RESULTS AND DISCUSSION Weather Conditions For detailed information on weather conditions, refer to Malhi et al. (28) or Lemke et al. (29). Due to several references to moisture conditions in discussing these results, precipitation information is provided in Fig. 1. Response to N Rate To provide an overview of crop response to N rate, and describe the nature of that response, trend lines were fitted to levels of each crop parameter at the four rates of N (x,.5x, 1.x and 1.5x) used. The significance of the linear and quadratic fit of each trend line was then tested and the results are summarized in Table 2. In 7 out of 12 site-years, increasing rate of N as urea (U) or anhydrous ammonia (AA), and placed in a SB or MRB showed no effect on plant density of wheat (Fig. 2). In the remaining 5 site-years where differences were observed, increases in plant density were observed as the rate of N increased with MRB_U in 3 site years and with SB_U in 1 site-year. Only one site (Scott in 2) showed a decrease in plant population with N rate and SB_U. Averaged over all site-years, increasing the rate of SB_U and SB_AA had no effect on plant density (Table 2, Fig. 3). On the other hand, MRB_U had a quadratic increase in plant density, while MRB_AA resulted in a linear increase in plant density. Other studies have shown that increasing rates of N can increase the risk of damage to seedlings but seldom increases the number of seedlings (Deibert 1993; Johnston et al. 1997; Malhi and Gill 24). Results of this study show that the overall risks between SB and MR, regardless of N forms or rates, are low. Under good soil moisture conditions (e.g., Indian Head, May June July Aug May June July Aug May June July Aug May June July Aug Indian Head Melfort Swift Current Scott Year Average Fig. 1. Total monthly precipitation at Indian Head, Melfort, Swift Current and Scott in 2, 21 and 22, and 3-yr average.

5 MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 323 Table 2. Analysis of variance for response of wheat to rate, form and placement of N fertilizer at Indian Head (IH), Melfort (MF), Swift Current (SC) and Scott (ST) in 2, 21 and 22, and average of 12 site-years IH MF SC ST IH MF SC ST IH MF SC ST Averaged over 12 site-years Can. J. Plant Sci. Downloaded from by on 5/8/18 Plant count SB_U L * NS NS * NS NS NS NS NS * NS NS NS Q NS NS NS NS NS NS NS NS NS NS NS NS NS SB_AA L NS NS NS NS NS NS NS NS NS NS NS NS NS Q NS NS NS * NS NS NS NS NS NS NS NS NS MRB_U L NS NS NS NS NS * NS NS NS ** NS NS * Q NS NS NS * NS NS NS NS NS * NS NS ** MRB_AA L NS NS NS NS * NS NS NS NS NS NS NS ** Q NS NS NS NS NS NS NS NS NS NS NS ns ns Seed yield SB_U L *** *** NS *** *** ** NS NS *** NS *** NS *** Q *** ** NS NS * NS NS NS ** NS * NS ** SB_AA L *** *** NS *** ** ** NS NS ** * *** * *** Q ** ** NS * * NS NS NS * NS * NS Ns MRB_U L *** *** NS *** ** NS NS NS ** NS *** ** *** Q *** NS NS * * NS * NS * NS * NS ** MRB_AA L *** *** * *** ** ** NS NS *** NS ** NS *** Q * NS NS NS NS * NS NS * NS NS NS Ns Straw yield SB_U L * *** NS * NS * NS NS ** * * NS *** Q NS ** NS NS NS ** NS * NS NS NS NS ** SB_AA L NS *** NS ** NS * NS NS * NS ** ** *** Q NS NS NS NS NS NS NS NS NS NS * NS * MRB_U L NS * * ** NS * NS NS ** NS *** NS *** Q NS NS NS NS NS NS NS NS NS NS * NS Ns MRB_AA L NS *** * * NS ** ** NS ** NS *** * *** Q NS ** NS NS NS NS NS NS NS * NS NS * Seed protein SB_U L ** *** * *** * *** *** *** *** NS *** NS *** Q NS *** NS ** NS ** NS * ** NS ** NS Ns SB_AA L ** *** NS ** * *** *** *** *** NS ** * *** Q NS NS NS *** NS NS *** NS NS * ** NS Ns MRB_U L NS *** ** NS * ** *** *** *** NS *** * *** Q NS * NS ** NS NS ** * NS NS * NS Ns MRB_AA L NS *** ** * NS *** *** *** *** NS *** ** *** Q NS NS NS ** NS NS NS NS NS NS ** NS Ns N uptake in seed SB_U L *** *** NS *** *** *** NS ** *** NS *** NS *** Q ** * NS NS * NS NS * *** NS NS NS * SB_AA L *** *** NS *** ** *** NS * *** * *** * *** Q ** * NS *** NS * NS NS * NS NS NS Ns MRB_U L *** *** * *** *** * NS *** *** NS *** * *** Q ** NS NS NS NS NS ** NS * NS NS NS * MRB_AA L *** *** * *** ** *** * *** *** NS ** NS *** Q * NS NS NS NS * NS NS NS NS NS NS Ns N uptake in straw SB_U L *** ** * * NS ** ** * *** * ** NS *** Q NS NS NS NS NS ** NS NS ** NS NS NS * SB_AA L *** ** NS *** NS ** * NS * * ** NS *** Q ** NS NS NS NS NS * NS NS NS NS NS Ns MRB_U L NS ** NS ** * ** * NS ** NS *** NS *** Q NS NS NS NS NS NS NS NS NS NS NS NS Ns MRB_AA L NS ** * ** NS ** *** * ** ** *** NS *** Q NS NS NS NS NS NS NS NS NS ** * NS Ns z SBside banded; MRBmid-row banded; Uurea; AAanhydrous ammonia; Llinear; and Qquadratic. *, **, ***Significant at P5.5, P5.1 and P5.1 levels, respectively; NS, not significant at P5.5.

6 324 CANADIAN JOURNAL OF PLANT SCIENCE Indian Head Plant density m Can. J. Plant Sci. Downloaded from by on 5/8/18 Melfort Swift Current Scott Plant density m 2 Plant density m 2 Plant density m x.5x 1.x 1.5x SB_U SB_AA Melfort and Swift Current in 2) N rate generally had no detrimental effect on plant density. Therefore, by and large, applying U or AA in a side-band or mid-row band is generally safe for spring wheat over a wide range of moisture conditions. Response of seed yield to increasing N rate was comparable among different combinations of placement and N form (Table 2, Fig. 4). Seed yield responses to N were more linear than quadratic, indicating that N was still limiting at these locations, even at the 1.5x rate. Under dry conditions (21 at Swift Current and Scott, and 22 at Melfort and Scott), there were no N responses observed on seed yield. The general lack of seed yield response to N rate at Swift Current under.x.5x 1.x 1.5x MRB_U.x.5x 1.x 1.5x MRB_AA Fig. 2. Effect of rate form and placement of N fertilizer on plant density of wheat at Indian Head, Melfort, Swift Current and Scott in 2, 21 and 22. normal precipitation (2) was attributed to high levels of mineral N in the soil, as indicated from the relatively high seed yield in the zero-n check treatment (Fig. 4). The only noticeable difference in effect among the four combinations of N fertilizer placement and form was at Scott in 2. At this site-year, the linear increase in yield with SB_U was stronger than the linear increase with MRB_AA. Averaged over site-years, increasing N rate resulted in linear to quadratic increase in seed yield with SB_U and MRB_U, and linear increase with SB_AA and MRB_AA (Fig. 3). With respect to straw yield, no response to increasing rate of N was observed in 6 of the 12 site-years (Table 2, Fig. 5) and these were mainly associated with dry

7 MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 325 Can. J. Plant Sci. Downloaded from by on 5/8/18 Plant density m 2 Straw yield (kg ha 1 ) N uptake in seed (kg N ha 1 ) conditions either in May (e.g., Melfort and Scott in 22) or throughout the season (e.g., Indian Head, Swift Current and Scott in 21). Under these conditions, straw yields were mainly between 1 and 2 kg ha 1, and as low as 5 kg ha 1 (Scott in 22). At Scott in 2, straw yield at all the rates was higher with side banding compared with mid-row banding, suggesting that under dry conditions, N fertilizer applied in a MRB may get stranded resulting in lower straw yields. Averaged across site years, a linear to quadratic response to increasing N rate was observed for all the four combinations of N fertilizer placement and form. Under dry conditions where no N response on seed yield response was observed (e.g. Melfort, Swift Current and Scott in 21, and Melfort and Scott in 22, Fig. 4) linear increases in seed protein contents were observed (Fig. 6). At other site-years where N responses on seed yield were observed, linear to quadratic responses on seed protein concentration were observed. At Melfort and Scott in 2 and Swift Current in 22, the typical initial decline in seed protein content with increasing N rate and then an increase with higher rates was observed x.5x 1.x 1.5x SB_U MRB_U Seed yield (kg ha 1 ) Seed protein (%) N uptake in straw (kg N ha 1 ) x.5x 1.x 1.5x SB_AA MRB_AA Fig. 3. Effect of rate form and placement of N fertilizer on wheat averaged over all site-years. (Selles and Zentner 21; Selles et al. 26; Farrer et al. 26). No differences among the four combinations of N fertilizer placement and form were observed for seed protein content in this study. Averaged over site-years, seed protein increased linearly with N rates. Response of N uptake in the seed and straw to increasing rate of N was similar to that of seed and straw yields, respectively. Differences in N uptake in the seed and straw largely mirrored differences in seed and straw yields, respectively (Table 2). With regard to statistical differences, a few were noted between seed yield and N uptake in the seed, and between straw yield and N uptake in the straw. Generally, when averaged over all site-years, N uptake, both in the seed and in the straw, increased linearly with increasing N rate for all form and placement combinations. Some quadratic trend was observed for SB_U and MRB_U for N uptake in the seed and for SB_U for N uptake in the straw. The response of wheat to increasing N rate in this study indicated the significance of soil moisture in N management. In earlier field research in Saskatchewan, Henry et al. (1986) noted that in the semi-arid prairies,

8 326 CANADIAN JOURNAL OF PLANT SCIENCE Can. J. Plant Sci. Downloaded from by on 5/8/18 Indian Head Melfort Swift Current Scott Seed yield (kg ha -1 ) Seed yield (kg ha -1 ) Seed yield (kg ha -1 ) Seed yield (kg ha -1 ) x.5x 1.x 1.5x SB_U SB_AA grain yield is mainly a function of available water and that grain yield response to N rate is greater as available water in soil increases. In another Saskatchewan study, Campbell et al. (25) reported that water accounted for 575% of the variation in grain yield. This was also true for straw yield given the strong association between straw dry matter and seed yield (Campbell et al. 25). Effect of N Form and N Placement Averaged over N form, method of N fertilizer placement had no effect on plant density, seed yield, straw yield,.x.5x 1.x 1.5x MRB_U.x.5x 1.x 1.5x MRB_AA Fig. 4. Effect of rate form and placement of N fertilizer on seed yield of wheat at Indian Head, Melfort, Swift Current and Scott in 2, 21 and 22. seed protein and N uptake in seed or straw when averaged over the 12 site-years (Tables 3, 4 and 5). Similarly, averaged over method of N fertilizer placement, form of N had no effect on these crop variables when averaged over the 12 site-years. Only one to 3 siteyears exhibited differences between SB and MRB, or between urea and AA on these crop variables. Under very dry conditions in May (Indian Head in 21, and Melfort and Scott in 22), SB reduced plant density more than MRB. Only 1 site-year (Scott in 2) exhibited a difference in seed yield between SB (2,335

9 MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 327 Indian Head Straw yield (kg ha -1 ) Can. J. Plant Sci. Downloaded from by on 5/8/18 Melfort Swift Current Scott Straw yield (kg ha -1 ) Straw yield (kg ha -1 ) Straw yield (kg ha -1 ) x.5x 1.x 1.5x SB_U SB_AA kg ha 1 ) and MRB (2,7 kg ha 1 ). This may be attributed to low utilization of MRB fertilizer under dry conditions as precipitation at this site-year was below normal in May and June. With regard to combinations of form and method of N placement, 8 of the 12 site-years showed no significant effect on plant density (Table 3). Six of these eight siteyears had normal to near normal precipitation during May. The 4 site-years where differences were observed had dry to very dry conditions in May (Indian Head in 21 and 22, Melfort and Scott in 22). Although the results were not consistent, MRB_AA seemed to have the least reduction in plant density compared with other.x.5x 1.x 1.5x MRB_U.x.5x 1.x 1.5x MRB_AA Fig. 5. Effect of rate form and placement of N fertilizer on straw yield of wheat at Indian Head, Melfort, Swift Current and Scott in 2, 21 and 22. combinations of form and method of placement of N fertilizer. This was also reflected in the combined analysis over the 12 site-years. The lower plant densities on SB compared with MRB systems under very dry soil conditions in our study are in agreement with other research showing that under moisture limiting conditions, ammonia forming N fertilizers can be detrimental to the seedlings if placed near the seed (Deibert 1993). It may be that the SB configuration did not provide adequate separation between the N fertilizer and seed, or there was poor sealing of the space between seed and N fertilizer rows because the soil was too dry. Alternatively, there may

10 24. Scott Swift Current Melfort Indian Head Seed protein (%). Seed protein (%). Seed protein (%). Seed protein (%). 328 CANADIAN JOURNAL OF PLANT SCIENCE Can. J. Plant Sci. Downloaded from by on 5/8/ x.5x 1.x 1.5x SB_U.x.5x 1.x 1.5x SB_AA MRB_U.x.5x 1.x 1.5x MRB_AA Fig. 6. Effect of rate form and placement of N fertilizer on seed protein content of wheat at Indian Head, Melfort, Swift Current and Scott in 2, 21 and 22. have been more moisture loss in the seed row and/or poor seed to soil contact due to the additional soil disturbance caused by the SB openers. However, the fact that plant density was largely unaffected by fertilizer N rate (Table 2, Fig. 2) tends to argue against the suggestion that lower plant densities on SB compared with MRB was related to poor separation between the fertilizer and the seed. Despite challenging (dry) conditions encountered at seeding time during much of this study, target plant densities (minimum of 15plants m 2 ) were met on both SB and MRB systems. There was a trend for lower plant densities on SB relative to MRB, indicating a higher risk of not meeting this target for the SB system. However, when differences in plant density were noted they did not correspond to differences in seed yield.

11 Can. J. Plant Sci. Downloaded from by on 5/8/18 Table 3. Effect of placement method and form of N fertilizer on plant density and seed yield of wheat at establishment in 2, 21 and 22 at Indian Head (IH), Melfort (MF), Swift Current (SC) and Scott (ST) in Saskatchewan Factors z IH MF SC ST IH MF SC ST IH MF SC ST Average over 12 site-years Number of plants per m SB U b ab 244 c ab 221 b AA b a 28ab b 222 b MRB U a b 267 bc a 226 b AA a ab 33 a a 239 a SE12 HSD32 SE3 HSD1 SB b b b 221 MRB a a a 232 SE9 HSD21 SE7 HSD14 U b 255 b AA a 292 a SE9 HSD21 SE4 HSD seed yield kg ha SB U 2352 a a 2164 a b a a AA 2168 b b 1968 b b a ab MRB U 224 ab a 219 ab ab a ab AA 2196 ab c 1886 b a b b SE66 HSD183 SE33.4 HSD1 SB a MRB b SE11 HSD29 SE36.4 HSD81 U a AA b SE134 HSD324 SE43.3 HSD95 z SBSide-banded, MRBMid-row banded, UUrea, and AAAnhydrous ammonia. x Means followed by the same letter in the same column and dependent variable are not different at a.5 level of significance using Tukey-Kramer Test. HSDTukey-Kramer s Honestly Significant Difference. MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 329

12 Can. J. Plant Sci. Downloaded from by on 5/8/18 Table 4. Effect of placement method and form of N fertilizer on straw yield and seed protein content of wheat in 2, 21 and 22 at Indian Head (IH), Melfort (MF), Swift Current (SC) and Scott (ST) in Saskatchewan Factors z IH MF SC ST IH MF SC ST IH MF SC ST Average over 12 site-years Straw yield (kg ha 1 ) SB U 7617 a 5218 a ab 3896 a 3733 ab AA 715 ab 5439 a a 3124 b 3724 b MRB U 681 c 449 b b 3759 ab 4364 a AA 6722 b 4971 a b 3314 ab 446 ab SE229 HSD636 SE1 HSD32 SB 7316 a 5328 a a MRB 642 b 451 b b SE283 HSD683 SE128 HSD281 U AA SE267 HSD648 SE8HSD Seed protein content (%) SB U a a b 18.5 a ab 2.6 ab 17.6 AA b a a 17.3 bc b 2.5 ab 17.4 MRB U a a ab 17.6 b a 2.2 b 17.5 AA ab b b 16.8 c ab 21.1 a 17.3 SE.3 HSD.8 SE.1 HSD.4 SB a MRB b SE.3 HSD.8 SE.1 HSD.2 U a AA b SE.4 HSD.9 SE.1 HSD.3 z SBSide-banded, MRBMid-row banded, UUrea, and AAAnhydrous ammonia. x Means followed by the same letter in the same column and dependent variable are not different at a.5 level of significance using Tukey-Kramer Test. HSDTukey-Kramer s Honestly Significant Difference. 33 CANADIAN JOURNAL OF PLANT SCIENCE

13 Can. J. Plant Sci. Downloaded from by on 5/8/18 Table 5. Effect of placement method and form of N fertilizer on seed N uptake and straw N uptake of wheat in 2, 21 and 22 at Indian Head (IH), Melfor (MF), Swift Current (SC) and Scott (ST) in Saskatchewan Factors z IH MF SC ST IH MF SC ST IH MF SC ST Average over 12 site-years Seed N uptake (kg N ha 1 ) SB U 69.7 a a 64.a 61.8 a 37.4 ab ab 63.7 ab a a AA 63.6 b b 54.2 b 55.3 b 37.6 ab b 64.8 a a bc MRB U 66. ab a 59. ab 55.5 b 33.8 b ab 6.4 ab a ab AA 64.b ab 42.9 c 49.1 c 39.6 a a 58.6 b b c SE2.HSD5.7 SE.9 HSD2.9 SB MRB SE3.6 HSD8.6 SE1.1 HSD2.3 U a a AA b b SE3.9 HSD9.4 SE1.2 HSD Straw N uptake (kg N ha 1 ) SB U 38.1 a 29.1 a 22.2 a 21.5 b 18.7 a 55.7 b a ab a AA 31.6 b 29.3 a 15.5 b 27.3 a 15.9 ab 52. b b ab ab MRB U 27.5 bc 22.b 22.3 a 18.2 b 17.5 ab 61.a ab b ab AA 26.5 c 25.5 ab 2.6 a 19.5 b 13.6 b 53.3 b ab a b SE1.6 HSD4.5 SE.8 HSD2.3 SB 34.8 a MRB 27.b SE2.5 HSD6. SE1.HSD2.2 U a AA b SE2.2 HSD5.3 SE.8 HSD1.8 z SBSide-banded, MRBMid-row banded, UUrea, and AAAnhydrous ammonia. x Means followed by the same letter in the same column and dependent variable are not different at a.5 level of significance using Tukey-Kramer Test. HSDTukey-Kramer s Honestly Significant Difference. MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 331

14 Can. J. Plant Sci. Downloaded from by on 5/8/ CANADIAN JOURNAL OF PLANT SCIENCE In fact, averaged over the 12 site-years, MRB_AA resulted in lower seed yield than SB_U. Similar effects were observed for N uptake in the seed and straw. In general, these results indicate that for spring wheat, SB and MRB systems using either urea or AA perform equally well with regards to plant stand, N uptake, seed yield and seed protein content, even in southwest Saskatchewan where AA is not typically used. Broadcast versus Side-banding Urea Contrast analysis indicated a significant reduction in plant density with side-banded urea (SB_U) compared with broadcast urea (Br_U) and when averaged over the 12 site-years (Table 6). Only at 3 site-years (Indian Head and Melfort in 21, and Indian Head in 22) were differences observed. However, this did not translate into reduced seed yield. Instead, when averaged over the 12 site-years, SB_U exhibited a higher seed yield (1754 kg ha 1 ) than Br_U (164 kg ha 1 ), but only for 2 of the site-years (Scott in 2 and Swift Current in 22). This may be attributed to higher than normal precipitation in these site-years (Fig. 2). Averaged over the 12 site-years, no differences in straw yield were observed between Br_U and SB_U. Differences were only observed in 1 site-year (Indian Head in 21) where SB_U exhibited a higher straw yield than Br_U (428 kg ha 1 vs 3149 kg ha 1 ). Overall, no difference in seed protein content was observed between Br_U and SB_U (Table 6). However, for 3 of the 12 site-years, differences were observed. At Swift Current in 2 and at Scott in 21, SB_U resulted in higher seed protein content than Br_U, while at Swift Current in 21, SB_U resulted in lower seed protein content than Br_U. Averaged over the 12 siteyears, seed N uptake was higher with SB_U than with Br_U, while no difference in straw N uptake was observed between SB_U and Br_U. In 3 site-years (Swift Current and Scott in 2, and Swift Current in 22) SB_U exhibited higher N uptake in the seed than Br_U. In 1 site-year (Indian Head in 21) higher N uptake in the straw was observed with SB_U than with Br_U (23.kg N ha 1 vs kg N ha 1 ). Under dry conditions in the spring (e.g., Indian Head and Swift Current in 21, and Indian Head in 22), SB is more likely to reduce plant density than Br. However, SB is more effective than Br in enhancing seed yield and N uptake in seed. These observations are consistent with earlier findings that banding N is superior to broadcasting (Malhi and Nyborg 1992; Grant et al. 21). However, under very dry conditions seedling establishment may be reduced on SB compared to Br. This may be as a result of failure to effectively seal the gap between the seed and the fertilizer. Effect of Timing and Form of N Application Except for plant density, no other plant variable exhibited differences in response to either fall or spring banding of either urea or AA (Table 7). However, a siteyear by treatment interaction indicates the need to look at individual site-years. When averaged over site-year, SB with either U or AA resulted in a lower plant density than with fall banding. However, only 2 site-years exhibited a significant reduction in plant density with spring SB_U as compared with FB_U, and only 3 siteyears showed reductions in plant density with spring SB_AA as compared with FB_AA. Averaged over site-years, no differences in seed yield, straw yield, seed protein content, and N uptake in the seed or in the straw were observed between U and AA when banded either in the fall or in the spring. The only 2 site-years where differences in seed yield were observed were at Swift Current in 2 and 22. In 2 at Swift Current, total precipitation during the first 3 mo was above normal, while August was very dry. Under these conditions FB_AA out-yielded SB_AA, but no yield differences were observed between FB_U and SB_U. This may be attributed to wet conditions at the time of seeding, which may lead to poor sealing of the furrow and loss of gaseous ammonia with spring SB_AA. In 22, precipitation was well below normal in May (Fig. 1). This may have allowed spring side-banded U and AA to yield better than fall banded U and AA due to positional advantage of applied N under dry conditions. Averaged over site-year, no differences in straw yield were observed between U and AA when banded either in the fall or spring. However, for 5 site-years, differences were observed. At 4 of these site-years, straw yield was higher with spring application. At Scott in 2, FB_U resulted in higher straw yield than SB_U (Table 7). While no differences in seed protein were observed between FB_U and SB_U, 5 of the 12 site-years exhibited differences between FB_AA and SB_AA, four of which exhibited higher seed protein content with FB_AA. Our results suggest that in general, U or AA can be fall banded with equal success, but the occasional disadvantage may be encountered with FB_AA compared with FB_U. For example, some ammonia losses may occur in the fall because the anhydrous ammonia injection channel does not seal well under dry soil conditions sometimes encountered after harvest. Effect of Phosphorus Fertilizer Placement No differences in the plant variables measured were observed between seed-placed P (SP-P) and side-banded P (SB-P) when averaged over the 12 site-years (Table 8). A look within site-years showed no differences were observed for all site-years on seed yield and N uptake in the seed or straw. Only at 2 site-years were differences in plant density observed due to P placement, but the effects were not the same, with SP-P exhibiting higher plant density in 1 site-year and lower in the other. With regard to straw yield, only 1 site-year (Swift Current in 2) exhibited a difference between SB-P (668 kg ha 1 ) and SP-P (6948 kg ha 1 ). At 2 site-years, seed protein content was higher with SP-P than with SB-P.

15 Can. J. Plant Sci. Downloaded from by on 5/8/18 Table 6. Effect of broadcast (BR_U) and side-banded (SB_U) urea on plant performance of wheat in 2, 21 and 22 at Indian Head (IH), Melfort (MF), Swift Current (SC) and Scott (ST) in Saskatchewan Treatment z Trt no. IH MF SC ST IH MF SC ST IH MF SC ST Average over 12 site-years Plant density Number of plants per m Br U a y 275 a 17a a a SB_U b 248 b 125 b b b SE21 HSD41 SE9 HSD17 Seed yield kg ha Br_U b b b SB_U a a a SE174 HSD344 SE73 HSD147 Straw yield kg ha Br_U b SB_U a SE427 HSD843 SE152 HSD35 Seed protein content % Br U b a 16.7 b SB_U a b 18.9 a SE.4 HSD.8 SE.2 HSD.5 Seed N uptake kg N ha Br_U b 51.5 b b b SB_U a 65.a a a SE5.5 HSD1.9 SE2.3 HSD4.6 Straw N uptake kgnha Br_U b SB_U a SE3.6 HSD7.1 SE1.3 HSD2.6 z Br_UBroadcast urea; SB_USide-banded urea. All treatment received the recommended N rate of 8kg ha 1 at IH & MF and 6kg ha 1 at SC and ST. y Means followed by the same letter in the same column and grouping are not different at a.5 level of significance using Tukey-Kramer s Honestly Significance Difference (HSD). MOOLEKI ET AL. * N AND P FERTILIZER MANAGEMENT EFFECTS ON WHEAT 333

16 Can. J. Plant Sci. Downloaded from by on 5/8/18 Table 7. Effect of banding N fertilizer (urea and AA) in the fall or spring on plant performance of wheat in 2, 21 and 22 at Indian Head (IH), Melfort (MF), Swift Current (SC) and Scott (ST) in Saskatchewan Treatment z Trt no. IH MF SC ST IH MF SC ST IH MF SC ST Average over 12 site-years Plant density Number of plants per m FB_U SB_U FB_AA SB_AA SE427 HSD843 SE152 HSD35 Seed yield kg ha FB_U SB_U FB_AA SB_AA SE21 HSD41 SE9 HSD17 Straw yield kg ha FB_U SB_U FB_AA SB_AA SE21 HSD41 SE9 HSD17 Seed protein content % FB_U SB_U FB_AA SB_AA SE21 HSD41 SE9 HSD17 Seed N uptake kg N ha FB_U SB_U FB_AA SB_AA SE21 HSD41 SE9 HSD17 Straw N uptake kg N ha FB_U SB_U FB_AA SB_AA SE21 HSD41 SE9 HSD17 z FBfall-banded; SBside-banded; Uurea; and AAanhydrous ammonia. All treatment received the recommended N rate of 8kg ha 1 at IH & MF and 6kg ha 1 at SC and ST. a, b Means followed by the same letter in the same column and grouping are not different at a.5 level of significance using Tukey-Kramer s Honestly significance difference (HSD). 334 CANADIAN JOURNAL OF PLANT SCIENCE