Economic Effects of Preceding Crops and Nitrogen Application on Canola and Subsequent Barley

Transcription

1 Published October 29, 2014 Crop Economics, Production & Management Economic Effects of Preceding Crops and Nitrogen Application on Canola and Subsequent Barley Mohammad Khakbazan,* Cynthia A. Grant, Jianzhong Huang, Elwin G. Smith, John T. O Donovan, Robert. E. Blackshaw, K. Neil Harker, Guy P. Lafond, Eric N. Johnson, Yantai Gan, William E. May, T. Kelly Turkington, and Newton Z. Lupwayi ABSTRACT The rising cost of N in western Canada has created interest in alternative sources of N fertilizer. Legumes have the ability to fix N supply for subsequent crops, but knowledge of the effects of legumes on subsequent canola or barley is limited. A multi-location study was conducted from 2009 to 2011 in western Canada to evaluate the economic effects of various preceding crops (P) and N rate on subsequent canola and barley in a P canola barley rotation. Six preceding crops (field pea, lentil, faba bean, canola, wheat, and green manure [GRM] legume [faba bean]) were grown in factorial combination with five N rates (0, 30, 60, 90, and 120 kg ha 1 ) at seven sites in Alberta, Saskatchewan, and Manitoba. When the preceding crop was GRM, the net revenue (NR) of canola or canola barley was highest but insufficient to compensate for negative NR during the GRM year (2009). Canola as a preceding crop yielded the least NR for the canola and canola barley phases of the rotation. The quadratic responses of NR for canola and barley to optimal N indicated that N applied could be reduced below 120 kg ha 1 without diminishing yield at some locations in western Canada. Over the entire 3-yr crop sequence, legume preceding crops (lentil or field pea) grown for seed provided the greatest returns. The GRM improved the yield of the following crops considerably but the increased canola and barley yields were not able to alleviate the lost NR during the preceding crop phase. A primary goal of N management is to apply sufficient N to optimize the yield of non-leguminous crops. However, the optimum N application varies for different crops and depends on the effects of a P and available soil N. Inefficient N application results in economic loss and potential negative environmental impacts including nitrate leaching, emission of greenhouse gases (GHG), and surface run-off of N into local water bodies promoting aquatic eutrophication. Optimal timing and N application rates with consideration of preceding crop type helps improve profitability of crop production and nutrient use efficiency (Malhi et al., 2010). Canola (Brassica napus L.) is a major cash crop in western Canada (17.9 Tg production in 2013, Canola Council of Canada, 2014) and barley (Hordeum vulgare L.) is a commonly grown crop in rotation with canola. Knowledge of effects of legume preceding crops and fertilizer rates on canola M. Khakbazan, C.A. Grant, and J. Huang, Agriculture and Agri-Food Canada (AAFC), Brandon Research Center, 2701 Grand Valley Road, P.O. Box 1000A, R.R.#3, Brandon, MB, R7A 5Y3; E.G. Smith, R.E. Blackshaw and N.Z. Lupwayi, AAFC, st Avenue South, Lethbridge, AB T1J 4B1; J.T. O Donovan, K.N. Harker and T.K. Turkington, AAFC, 6000 C & E Trail, Lacombe, AB; G. P. Lafond; W.E. May, AAFC, P.O. Box 76, Indian Head, SK SOG 2KO; E.N. Johnson, AAFC, P.O. Box 10, Scott, SK SOK 4AO; and Y. Gan, AAFC, P.O. Box 1030, Swift Current, SK S9H 3X2. Received16 May *Corresponding author (Mohammad.Khakbazan@agr.gc.ca). Published in Agron. J. 106: (2014) doi: /agronj Copyright 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. and barley is limited. Therefore, continued research in this area remains a high priority (Chien et al., 2009). Few studies have investigated the economic response of crop yield to N application rates under goals of profit maximization. Van Tassell et al. (1996) derived the most profitable rate of N application for sugar beet (Beta vulgaris L.) production that maximized economic returns. The results indicated that optimal requirement of applied N for maximizing root yield varied for maximizing beet yield and for maximizing economic returns. Baker et al. (2004) used a modeling approach and derived profit-maximizing input rates for production of hard red spring wheat (Triticum aestivum L.) for different rates of N fertilization, grain yield, and grain protein concentration. They found that maximized net returns varied with changes in both N and wheat grain prices. Some studies have focused on the influence of preceding crops on subsequent crop yields and net revenue when legumes were the preceding crop (Stevenson and van Kessel, 1996a; Van Kessel and Hartley, 2000; Khakbazan et al., 2009a; Grant et al., 2012). Symbiotic Rhizobium bacteria in root cells of legumes can fix atmospheric N 2 for non-legume crops, thereby increasing soil organic N accretion and reducing dependence on N fertilizers. To examine the effects of pea (Pisum sativum L.) on the subsequent wheat crop, Stevenson and van Kessel (1996a) studied pea wheat and wheat wheat cropping systems at three Abbreviations: P, preceding crop; NR, net revenue; GRM, green manure; GHG, greenhouse gases; CNR, canola net revenue; BNR, barley net revenue; CBNR, average annual canola and barley net revenue; PCBNR, average annual preceding crop, canola, and barley net revenue. Agronomy Journal Volume 106, Issue

2 Table 1. Soil types and total growing season precipitation (1 Apr. 30 Sept.) and annual precipitation recorded at seven locations in western Canada from 2009 to Total precipitation Soil classification Location Canadian United States Apr. Sept. Jan. Dec. Apr. Sept. Jan. Dec. Apr. Sept. Jan. Dec. mm Brandon, MB Black Chernozem Calcic Haplocryoll Beaverlodge, AB Gray Luvisol Argic Haplocryalf Lacombe, AB Black Chernozem Typic Haplocryoll Lethbridge, AB Dark Brown Chernozem Calcic Haplocryoll Indian Head, SK Black Chernozem Vertic Haplocryoll Scott, SK Dark Brown Chernozem Calcic Haplocryoll Swift Current, SK Brown Chernozem Calcic Haplocryoll sites located in Saskatchewan, Canada. They found that subsequent grain yield of wheat was 43% greater when preceded by pea rather than wheat when averaged across sites. The increase in yield resulted from the additional N accretion in soil and from pea residue in the pea wheat rotation. Biological N 2 fixation in a cropping system is an important aspect of sustainable and environmentally friendly long-term crop production (Van Kessel and Hartley, 2000). Although much of the N 2 fixed by Table 2. Treatments analyzed for costs and net revenue in Brandon, Beaverlodge, Indian Head, Lacombe, Lethbridge, Scott, and Swift Current from 2009 to Canola (C) in 2010 Barley (B) in 2011 Treatment no. Preceding crop (P) in 2009 N rates applied N rates applied to to canola in 2010 barley in 2011 kg ha Field pea Faba bean Faba bean GRM Lentil Canola Wheat Different crops grown in 2009 were defined as preceding crop. GRM = green manure. Each treatment was replicated four times. legumes is removed at harvest, the remainder becomes available to subsequent crops as is also the case with soil organic matter or with fertilizer N (Van Kessel and Hartley, 2000). As reported by Khakbazan et al. (2009b), optimal N application rate for wheat was reduced by including field pea as the preceding crop in a pea wheat cropping sequence. Therefore, production of legume crops including field pea, lentil (Lens culinaris Medik.), chickpea (Cicer arietinum L.), common bean (Phaseolus vulgaris L.) and faba bean (Vicia faba L.) in cereal-based cropping systems is important as they potentially contribute to soil organic N accretion. Usually, faba bean, field pea, and lentil fix more N 2 than chickpea and common bean (Walley et al., 2007). In general, crop yield functions have been specified as linear across most production inputs with quadratic or logarithmic measures of particular production inputs denoting non-constant marginal physical products (Hansen, 1991). Khakbazan et al. (2011) assessed several crop yield response functions and found that the quadratic form was the most common functional form relating N input to wheat or canola yield. Gandorfer and Rajsic (2008) used an empirical quadratic model to examine economically optimal N rates for winter wheat. Determining N sufficiency and optimal use of N has important implications in terms of crop production and farm economics. Khakbazan et al. (2013) developed a regression model to determine opportunity cost of nutrient loss due to quantity of the nutrient being exported from agricultural fields. They concluded that farmers could lose up to CND$7 yr 1 ha 1 solely due to nutrients exported from their fields. This potential loss does not consider the costs to society in terms of environmental damage. To evaluate the combined effects of preceding crops and N fertilizer rates, a large, 3-yr ( ) multi-location study was conducted in a range of agro environments across western Canada. The objective of this study was to evaluate the economic effects of legume and non-legume preceding crops and N rates on costs and net revenues (NR) of canola grown the following year, barley grown after canola, canola barley portion of the rotation, and the entire P canola barley rotation. MATERIALS AND METHODS Field experiments were conducted under no-till management in 2009 through 2011 at Beaverlodge ( W, N), Lacombe ( W, N), and Lethbridge ( W, N) located in Alberta; Indian Head ( W, N), Scott ( W, N), and Swift Current ( W, N) in Saskatchewan; and Brandon (99.98 W, N) in Manitoba. These locations covered 2056 Agronomy Journal Volume 106, Issue

3 a wide range of soil types, total annual precipitation, and precipitation between 1 April and 30 September, and spanned a distance of 1600 km from east to west (Table 1). In 2009, field pea (cultivar CDC Golden), lentil (cultivar CDC Imperial), faba bean (cultivar Snowbird), imidazolinone-resistant canola (cultivar 45H73), and wheat (cultivar CDC Imagine) were sown to be harvested for seed (Table 2). Faba bean was also seeded as a GRM treatment. Legume seed was inoculated at each location. Canola and wheat, but not the legumes, were fertilized according to the soil test recommendation for N to produce an average, but not excessive yield for the location. Nitrogen was applied as urea (46 0 0) at seeding time, and was side-banded 2.5 to 7.5 cm from the seed, depending on the seeding equipment available at each location. Mono-ammonium phosphate (MAP) ( ) was applied with the seed to all crops according to the soil test recommendation for phosphorus. Weeds were controlled in each crop with imazamox (20 g a.i. ha 1 ) and Merge adjuvant (0.5% vol/vol). The GRM was sprayed at the flat pod leaf stage with glyphosate at 900 g a.e. ha 1 and clopyralid at 50 g a.i. ha 1 and mowed in the fall and the entire plant returned to the soil surface. The crops sown for seed were swathed and then the seed was harvested at maturity. After harvest, the straw of each crop was chopped and spread on the surface of the plots. These crops, seeded in 2009 at each location, provided the six crop residue treatments for the canola and barley (cultivar AC Metcalfe) experiments conducted in 2010 and 2011, respectively (Table 2). In 2010, glyphosate-resistant canola (cultivar 7255) was sown at 150 seeds m 2 across the entire experimental area on crop residues established in 2009 in each location (Table 2). In 2011, each site was sown to barley at 300 seeds m 2 (Table 2). The experiment in 2010 and 2011 was designed as a split-plot with the six crop residues established in 2009 as main plots. The subplots in 2010 and 2011 consisted of five N rates (0, 30, 60, 90, and 120 kg ha 1 ) randomized within the main plots. All 30 treatments, consisting of the factorial combination of five N rates by six preceding crops, were replicated four times each year (Table 2). Field plot sizes were 2 by 5 m at Brandon site, 3.66 by 15 m at Beaverlodge, 3.96 by m at Indian Head, 3.66 by m at Lacombe, 4.25 by 12 m at Lethbridge, 3.65 by 15 m at Scott and 2 by 14 m at Swift Current. Details of the design and methods of this experiment are further described in the agronomic companion paper by O Donovan et al. (2014). The N was side-banded as previously described. Phosphorus was applied according to the soil test recommendation as MAP with the canola and barley seed. Sulfur (0 15 kg ha 1 ) was applied as ammonium sulfate where necessary in the canola, thus the zero N plots received a small amount of N (4 18 kg N ha 1 as MAP and as much as 17 kg N ha 1 of ammonium sulfate). The N was supplied uniformly across treatments at each location and was treated as part of the background N supply. For weed control in canola, glyphosate (450 g a.i. ha 1 ) was applied once pre-seed and once in-crop. In barley, registered herbicides were used at each location to control the variable spectrum of weeds. Seed drills with knife openers were used at all locations. The seed drills provided approximately 10% seed bed utilization with 20 to 23 cm row spacing. Canola and barley were swathed at maturity and subsequently harvested for seed. After harvest, the straw of canola in 2010 and barley in 2011 was chopped and spread on the surface of the plots. Harvested seed was cleaned and weighed and the yield was calculated based on grain moisture of 10% for canola and 14% for barley. Canola emergence in preceding field pea and lentil plots was nonexistent or extremely poor and variable at Lacombe in The reason for the poor emergence is unclear. There was some evidence that cutworm damage to canola may have been greater in plots seeded to field pea and lentil than to the other crops. Disproportionate flooding in some of the field pea plots may have also contributed to the poor canola emergence. For this reason, canola data from field pea and lentil plots at Lacombe were excluded from the statistical analysis. Economic Analysis Net revenue was defined as the income remaining after paying for all cash costs (i.e., seed, nutrients, weed and disease control, transportation, fuel and oil, repairs, crop insurance premium, miscellaneous expenses, land taxes and land investment, and interest cost on variable inputs), ownership costs on machinery and buildings (depreciation, interest on investment, and insurance and housing), and labor, as described by Zentner et al. (2002). No allowance was made for interest costs associated with land equity. Labor cost was assumed to be $20 h 1 to represent higher-skilled labor required for agricultural production. Agronomic data from the field trials, combined with price and cost data for machinery and inputs, were used to develop crop budgets. The economic analysis included all inputs used in field operations from pre-seeding through to harvest and post-harvest Table 3. Crop prices, seed costs, and seed rates applied at seven locations in the western Canada. Seed rate Crop Brandon Beaverlodge Indian Head Lacombe Lethbridge Scott Swift Current Seed price Crop product price for 2012 kg ha 1 $ kg Field pea Faba bean Lentil Canola Wheat Canola Barley Seeding rate of faba bean grown for green manure was the same as seed rate of faba bean grown for seed within a location. Agronomy Journal Volume 106, Issue

4 activities. All purchased inputs used in each treatment, including variable and fixed costs for all field operations, nutrient application, weed and disease controls, crop insurance, harvesting, storage, and transportation of saleable products, were included in the analysis. Input prices from various sources were used to represent the crop production implemented. Tables 3 and 4 provide a summary of prices and amounts of input and output. Field operation schedules and equipment used were determined for each of the crops based on practices that are followed by producers in western Canada. Farm machinery sizes and work rates were calculated based on an average farm size of 907 ha (Manitoba Agriculture Food and Rural Initiatives, 2012; Saskatchewan Agriculture, Food and Rural Revitalization, 2012). The effect on profitability and risk of the crops from participation in the Canada-provincial Crop Insurance Program were examined. Participation was assumed to be at the 70% yield coverage. The 2012 premium rates, premium discounts, and payout criteria were assumed based on Manitoba soil zone maps (Manitoba Agricultural Services Corporation, 2014). Manitoba Agricultural Services Corporation defines different soil zones based on soil productivity, climate, and the probable yield to estimate crop insurance coverage. If there was a payout, which occasionally occurred, gross revenue was adjusted to account for the insurance revenue. Crop price data were collected from various sources (Statistics Canada, 2014; Manitoba Agriculture Food and Rural Initiatives, 2013; Manitoba Agricultural Services Corporation, 2014). Input and output prices vary widely and depend on many factors. Since the objective of this study was to compare economics of different nutrient treatments, price variation would have a similar impact on all treatments; therefore, the ranking of nutrient treatments would not be affected. The net farm-gate prices for the grains (net of rail transportation and Table 4. Total rates and costs of fertilizer and pesticide applied in 3 yr ( ) at seven locations in the western Canada. Location Product Brandon Beaverlodge Indian Head Lacombe Lethbridge Scott Swift Current Product cost kg ha 1 $ kg 1 Fertilizer Urea (46 0-0) C -114 C C-140 C-218 C-168 C-196 C W -110 W W W-179 W-96 W-168 W-60 MAP ( and ) C-38 C-45.2 C-50 L -50 L-50 W-34 A W-58 W-45.2 L-50 C-45 L-34 L-48 L-49.5 A A A A-116 A-117 A-86 AS ( ) A SP ( ) A-60 A-60 A PS ( ) A-60 A Potash (0 0 60) A kg or L a.i. ha 1 $ kg 1 or L 1 a.i. Pesticide 2,4-D A Achieve A-0.20 A-0.20 A Aim A-0.02 A Axial A-0.06 A-0.06 A Bravo 500 A Bromoxynil A-1.2 A Buctril M A-0.28 A-0.60 A-0.60 A Curtail M GRM Decis A-0.15 A-0.15 A-0.55 A Frontline XL A-0.36 A Glyphosate A A-1.35 A-0.45 A-2.25 A-3.13 A-1.80 A GRM-2.50 GRM-0.90 GRM-0.90 Headline A Lontrel 360 A-0.10 GRM-0.15 GRM Maverick III A-1.80 A Prestige XC A Proline 480 SC A Refine SG A Sevin XLR A Solo A-0.02 A-0.02 A-0.02 A-0.02 A-0.02 A-0.02 A Spectrum A Nitrogen treatment rates of 0, 30, 60, 90, and120 kg ha 1 were achieved with urea of 0, 65, 130, 195, and 260 kg ha 1 for each of seven locations respectively in 2010 and Fertilizers , , , , , and applied in a small amount were not listed. C = canola; W = wheat; MAP = mono ammonium phosphate; L = legumes includes field pea, faba bean, faba bean used as green manure, and lentil; A = all crops; AS = ammonium sulfate; SP = sulfate of potash; PS = potassium sulfate; and GRM = faba bean for green manure, Products of glyphosate included Credit 45, Roundup Transorb, Ultra 2, WeatherMax, R/T 540, Vantage Plus Max II. Adjuvants were applied, but not listed Agronomy Journal Volume 106, Issue

5 elevator handling costs) were taken at their respective mean values, $185 t 1, $490 t 1, $238 t 1, $290 t 1, $390 t 1, and $220 t 1 in order of barley, canola, field pea, faba bean, lentil, and wheat (Manitoba Agriculture Food and Rural Initiatives, 2013). The 2013 net farm-gate prices were also used for sensitivity analysis and to see if ranking of treatments would be affected. The 2013 net farm-gate prices were $190 t 1, $555 t 1, $280 t 1, $290 t 1, $460 t 1, and $240 t 1 for barley, canola, field pea, faba bean, lentil, and wheat. The NR was expressed in CND$ ha 1 for each crop and crop sequence. Statistical analysis was conducted using PROC MIXED in SAS (Littell et al., 2006; SAS Institute, 2008). Data was analyzed for each location with preceding crop and N rate as fixed effects and replicate as random effect variables. An additional analysis was conducted with location and the location interaction with fixed effects as random. This analysis allowed for a more generalized assessment across locations of the effects of the preceding crops and N rates on the canola and barley variables and may also increase statistical power since the overall sample size is expanded (O Donovan et al., 2014). Contrast statements were used to test for linear and quadratic responses to N rate, and regression equations describing the relationship between the dependent variable and N rate were fit based on the nature of the response at a given preceding crop type for all locations. Treatment effects were considered significant at P < 0.05, with values of P < 0.1 reported as a possible trend. Total cost, Table 5. Cost summary of canola, barley, and cropping systems over seven locations in western Canada. C (2010) B (2011) C-B ( ) P-C-B ( ) Location Variable Fixed Total Variable Fixed Total Variable Fixed Total Variable Fixed $ ha 1 Brandon 613b 228c 840c 378f 203e 582e 496d 216d 711d 467d 209d 676e Beaverlodge 580c 224d 804d 470c 269b 739c 525c 247bc 771c 481cd 228b 709d Indian Head 585c 208f 793de 441d 229d 670d 513cd 218d 731d 463d 214d 677e Lacombe 620b 262a 882b 598a 309a 908a 608a 289a 896a 552a 267a 819a Lethbridge 575cd 230c 806d 473c 268b 742c 524c 249b 774c 491c 232b 724d Scott 558d 218e 777e 551b 266b 817b 554b 242c 797bc 518b 230b 747c Swift Current 726a 238b 963a 420e 245c 665d 573b 241c 814b 568a 222c 790b Cropping sequence from 2009 to 2011 was preceding crops (P)-canola (C)-barley (B). Means followed by the same letter in a column are not significant (p > 0.05). Total Table 6. Average annual net revenue of canola, barley, and cropping systems as affected by preceding crop over seven sites in western Canada from 2009 to C (2010) B (2011) C-B ( ) P-C-B ( ) Location or preceding crop Mean ± SE n Mean ± SE n Mean ± SE n Mean ± SE n $ ha 1 $ ha 1 $ ha 1 $ ha 1 Location Brandon 405 ± 21Ca ± 5Gc ± 20Db ± 16Db 346 Beaverlodge 277 ± 15Ea ± 9Bbc ± 9Cab ± 12Cc 360 Indian Head 58 ± 17Fb ± 7Fb ± 10Eb ± 19Da 360 Lacombe 958 ± 37Aa ± 9Ac ± 32Ab ± 33Ab 233 Lethbridge 486 ± 22Ba ± 10Cd ± 15Bb ± 16Bc 360 Scott 268 ± 17Ea ± 7Ec ± 11Db ± 12Dc 358 Swift Current 340 ± 11Da ± 6Dc ± 10Cb ± 19Ed 360 Preceding crop Canola 240 ± 22Ca ± 13Bc ± 14Cb ± 17Bab 417 Faba bean as GRM 586 ± 29Aa ± 15Ac ± 20Ab ± 25Cd 420 Faba bean 373 ± 30Ba ± 14Bc ± 18Bb ± 19Ab 408 Field pea 425 ± 21Ba ± 14Bc ± 15Bb ± 13ABb 360 Lentil 442 ± 18BCa ± 14ABc ± 14 BCb ± 16ABb 360 Wheat 348 ± 28Ba ± 13Bc ± 17 BCb ± 15Bb 412 ANOVA P > F Experimental site < < < < Preceding crop < < < < Experimental site preceding crop < < < Cropping sequence from 2009 to 2011 was preceding crops (P) canola (C) barley (B). GRM = green manure. Means and standard error (SE) of seven sites followed by the same capital letter in a column are not significant (p > 0.05) and by same lower letters in a row are not significant (p > 0.05). n was the number of data observations. For Brandon and Indian Head sites 2011 barley grain yields were low due to excessive rainfall and flooding. Agronomy Journal Volume 106, Issue

6 gross revenue, and NR were calculated using E-Views software (Eviews, 2012). In regression analysis, NR of crop and cropping sequences was predicted based on the following equation: NR s = c + an + bn 2 + β 1 P 1 + β 2 P 2 + β 3 P 3 + β 4 P 4 + β 5 P 5 + e i,s = 1,2,,7 where NR s is the predicted NR in $ ha 1 in site s, N is nitrogen application rate in kg ha 1 ; c is the intercept when N = 0; coefficient a is the linear term; coefficient b is the curvature rate of parabola; β 1, β 2, β 5 are coefficients for proxy variables representing an attribute to indicate the absence or presence of effect of preceding crops, P 1, P 2, P 5 represent preceding crop faba bean, pea, lentil, canola, and faba bean GRM, and e i is the error term. Preceding crop wheat was used as a base in this regression. Proxy variables were created to correctly predict the effect of preceding crops on NR. Crop revenue functions were tested for resulting coefficient sign and level of significance, in combination with theoretical responses of crop revenue to each variable. The specification of the model was based on a number of criteria including theoretical consistency, goodness of fit measure, and prior expected signs of the coefficients. The effects of preceding crops and N rates on average annual net revenues are investigated for (i) the canola phase in 2010 (C), (ii) barley phase in 2011 (B), (iii) combined canola barley phases over (C B), and (iv) the entire P C B rotation over 2009 to 2011 (P C B). Canola and barley only include the average NR for their respective years (2010 or 2011) and C B Fig. 1. Actual (indicated by symbols) and predicted annual net revenue as affected by preceding crop and N application rates at seven locations in western Canada from 2009 to By combining preceding crop residue effects for each site and each annual net revenue category, predicted regression lines for linear or quadratic relationship between the annual net revenue and applied N rate were tested with SAS Proc Mixed procedure and p values derived from the test were presented. C = canola, B = barley, C B = canola barley, P C B = preceding crop canola barley, L = linear relationship, G = quadratic relationship and ns = no significant difference (p > 0.05) Agronomy Journal Volume 106, Issue

7 includes the average NR over the 2-yr period ( ). The NR from the preceding crop phase (2009) is only considered in P C B, which is the average NR for the entire crop rotation over 2009 to RESULTS AND DISCUSSION Canola Cost and Net Revenue in 2010 The variable costs, fixed costs, total costs, and average annual canola net revenue (CNR) in 2010 varied from site to site (Tables 5 and 6). Total canola cost was greatest at Swift Current and least at Scott. The canola costs were the same with the exception of N fertilizer under each treatment at each site because the same input managements were applied regardless of the preceding crop (data not shown). The average CNR was higher at Lacombe and lower at Indian Head compared to other sites (Table 6), indicating that the NR was affected by different levels of soil N and different environmental conditions for crop growth. The average annual CNR was influenced by preceding crop residues (Fig. 1 and Tables 6 and 7). The interaction effect between experimental sites and preceding crop residues on average annual CNR was significant (Table 6). Average annual CNR was higher when the preceding crop was either wheat or a legume grown for seed, compared to when canola was the preceding crop (Table 7). The highest average annual CNR was obtained when faba bean GRM was the preceding crop (Fig. 2). Lentil and pea residues resulted in higher canola NR than wheat or canola residues at most sites (Tables 6 and 7). Compared to wheat residues, CNR was higher for all sites when the preceding crop was GRM, whereas CNR was lower at most Table 7. The effect of preceding crops established in 2009 on net revenue gain or loss of canola (C), barley (B), canola barley (C B) and preceding crop canola barley (P C B) compared to preceding crop wheat at seven locations in the western Canada from 2009 to P values for differences from wheat are in parentheses. Gain or loss of net revenue compared to preceding crop wheat Preceding crops Location Wheat Canola Faba bean Faba bean GRM Lentil Pea C (2010, $ ha 1 ) Brandon (0.004) 27 (ns) 156 (<0.001) 59 (ns) 83 (0.032) Beaverlodge (0.037) 6 (ns) 262 (<0.001) 70 (0.061) 63 (0.091) Indian Head (ns) 5 (ns) 301 (<0.001) 228 (<0.001) 77 (0.059) Lacombe (<0.001) 48 (ns) 311(<0.001) Lethbridge (<0.001) 98 (0.072) 262 (<0.001) 20 (ns) 68 (ns) Scott (ns) 47 ns 257 (<0.001) 80 (0.064) 68 (ns) Swift Current (ns) 122 (<0.001) 114 (<0.001) 99 (0.002) 101 (0.002) Average ( 31%) 22 (6%) 238 (68%) 93 (27%) 77 (22%) B (2011, $ ha 1 ) Brandon (ns) 23 (0.064) 26 (ns) 5 (ns) 3 (ns) Beaverlodge (ns) 44 (0.02) 135 (<0.001) 63 (0.001) 52(0.007) Indian Head 32 4 (ns) 37 (0.023) 59 (<0.001) 41 (0.011) 13 (ns) Lacombe (ns) 25 (ns) 55 (0.002) 41 (0.025) 8 (ns) Lethbridge (ns) 1 (ns) 124 (<0.001) 17 (ns) 65 (0.004) Scott (ns) 20 (ns) 35 (0.09) 18 (ns) 6 (ns) Swift Current (0.007) 3 (ns) 4 (ns) 2 (ns) 0 (ns) Average (11%) 15 (16%) 63 (67%) 26 (28%) 19 (20%) - C B ( , $ ha 1 ) Brandon (ns) 2 (ns) 91 (ns) 32 (ns) 43 (ns) Beaverlodge (ns) 25 (ns) 199 (<0.001) 66 (0.006) 57 (0.018) Indian Head (ns) 21(ns) 180 (<0.001) 135 (<0.001) 45 (0.077) Lacombe (0.06) 2 (ns) 149 (0.103) Lethbridge (0.003) 49 (ns) 193 (<0.001) 18 (ns) 66 (ns) Scott (ns) 30 (ns) 146 (<0.001) 49 (ns) 37 (ns) Swift Current (ns) 63 (0.063) 59 (0.081) 49 (ns) 50 (ns) Average (-23%) 13 (6%) 145 (65%) 58 (26%) 50 (22%) P C B ( , $ ha 1 ) Brandon (ns) 35 (ns) 122 (<0.001) 61 (ns) 57 (ns) Beaverlodge (ns) 85 (ns) 58 (<0.001) 113 (0.006) 115 (0.018) Indian Head (ns) 412 (<0.001) 22 (<0.001) 407 (<0.001) 231 (0.077) Lacombe (0.063) 12 (ns) 315 (0.103) Lethbridge (0.003) 41 (ns) 22 (<0.001) 175 (ns) 198 (ns) Scott (ns) 93 (ns) 34 (<0.001) 198 (ns) 91 (ns) Swift Current (ns) 40 (0.063) 151 (0.081) 14 (ns) 5 (ns) Average (11%) 78 (46%) 97 ( 57%) 124 (73%) 115 (68%) Gain or loss of net revenue averaged over N rates was calculated for each alternative preceding crop compared to preceding crop wheat. Positive values indicate preceding crop leading to a higher net income and negative values indicate preceding crop leading to a lower net income. P values in parentheses were derived from the F test used to compare regression lines. GRM = green manure, ns = no significant difference (p > 0.10). Value in parentheses in the same row indicates average percentage change over seven locations compared to wheat. Agronomy Journal Volume 106, Issue

8 sites when the preceding crop was canola (Table 7). Averaged across locations, the CNR compared to wheat was increased by 68, 22, and 27% when preceding crops were GRM, pea, lentil, but decreased by 31% when the preceding crop was canola (Table 7). These results are in general agreement with previous research that showed higher yields when wheat was preceded by pea, medic, or vetch rather than wheat; legumes produce N through fixation which provide benefits to the following crops (Stevenson and van Kessel, 1996b; Fischer et al., 2002). Of the legumes grown for seed as preceding crops, faba bean had the most inconsistent and least positive effects on CNR (Table 7). A significant increase in CNR following faba bean grown for seed occurred only at Swift Current, whereas there was a trend towards a loss in CNR at Lethbridge (p = 0.072). Averaged across locations, faba bean had 6% increase in CNR compared to wheat as the preceding crop (Table 7). When canola was the preceding crop, significant CNR losses occurred at Brandon, Beaverlodge, Lacombe, and Lethbridge Fig. 2. Actual annual net revenue arranged by combination of preceding crop and N application rates over seven locations in western Canada from 2009 to C = canola, B = barley, C B = canola barley, P C B = preceding crop canola barley, GRM = green manure and LSD 0.05 = Least Significant Difference (p = 0.05) Agronomy Journal Volume 106, Issue

9 in 2010 (Table 7). Averaged across locations, growing canola after canola reduced CNR by 31% compared to wheat as a preceding crop (Table 7). Application of N fertilizer influenced the average annual CNR when data for all sites were combined (Table 8). The CNR increased with higher N rates from 0 to 60 kg ha 1 and then levelled off at higher rates. The response of CNR to N rate was positive at Brandon, Indian Head, Lethbridge, and Scott but tended to decline at maximum N at some sites such as Brandon and Scott (Fig. 1). At Swift Current and Beaverlodge, CNR response to N rates was not significant, whereas at Lacombe, the response of CNR to N plateaued at very low N rates (Fig. 1). In general, the shape of the CNR response to N rates was similar among preceding crops, that is, the responses to N rate tended to be parallel among the different preceding crops (Fig. 1) as expected due to the lack of a significant preceding crop by N rate interaction. Averaged across preceding crops, responses to N rate were both linear and quadratic only at Brandon and Scott, and linear at Indian Head and Lethbridge, but not significant at Beaverlodge, Lacombe, and Swift Current (Fig. 1). The linear responses suggest that CNR was not maximized at the highest N rate (120 kg ha 1 ). The linear slope values showed the CNR was more responsive to higher N rate application for some locations such as Brandon and Lethbridge (data not shown). The response of CNR to N rate was not significant at Lacombe possibly due to the relatively high initial soil nitrate N levels at this site (O Donovan et al., 2014). Malhi et al. (2010) and Grant et al. (2012) reported similar responses of barley yield to N fertilizer in linear or quadratic form. When data were averaged for the seven sites the most economical treatment for CNR was the combination of GRM residue plus application of 60 to 90 kg of N ha 1 (Fig. 2). Barley Cost and Net Revenue in 2011 Costs and net revenue, variable costs, fixed costs, total costs, and average annual barley net revenue (BNR) in 2011 significantly varied from site to site (Fig. 1 and Tables 5 and 6). The total barley cost was higher at Lacombe and lower at Brandon compared to other sites. The barley costs were the same with the exception of N fertilizer under each treatment at each site because the same input managements were applied regardless of the preceding crop (data not shown). The average BNR was higher at Lacombe and lower at Brandon and Indian Head compared to other sites, indicating that the BNR was affected by different levels of soil N and different environmental conditions for crop growth. Excessive rainfall and flooding conditions in 2011 at Brandon and Indian Head affected crop yield and in turn caused the BNR to become negative. The BNR was less affected by preceding crop residues than was CNR because barley in 2011 was 2 yr after preceding crops in 2009 and the effects of preceding crops on NR of barley had diminished over time (Fig. 1 and Tables 6 and 7). The highest average annual BNR was obtained when faba bean GRM was the preceding crop in 2009 (Fig. 1 and Tables 6 and 7). A significant increase in BNR occurred at Beaverlodge, Indian Head, Lacombe, and Lethbridge, whereas there was a trend towards an increase at Scott where GRM was preceding crop (p = 0.09). Averaged across locations, the BNR was increased by 67% for preceding crop GRM compared to preceding crop wheat (Table 7). Of the legumes grown for seed as preceding crops in 2009, a significant increase in BNR occurred for faba bean only at Beaverlodge and Indian Head, for lentil at Beaverlodge, Indian Head, and Lacombe, and for field pea at Beaverlodge and Lethbridge. Averaged across locations, the BNR was increased by 16, 28, and 20% for preceding crops faba bean, lentil, and field pea, compared to preceding crop wheat (Table 7) indicating that legume crops differ in their N 2 fixing capacities resulting in variable soil N benefits as reported by Walley et al. (2007). When canola was the preceding crop, a significant increase in BNR occurred only at Swift Current (Table 7), whereas a slight increase or loss in BNR was observed at the other sites. Studies have shown that canola as a preceding crop can be beneficial to the following crops by breaking up pest cycles and increasing the potential yield (Bourgeois and Entz, 1996; Krupinsky et al., 2004; Johnston et al., 2005; Velazco 2013). The benefits of canola as a preceding crop are largely due to canola s ability to suppress leaf spot diseases and Cochilobolus sativus spores and consequently common root rot in following cereal crops (Krupinsky et al., 2004; Velazco 2013). Averaged across locations, the BNR was increased by 11% for preceding Table 8. Average annual net revenue of canola and cropping systems as affected by N application rates over seven locations in western Canada from 2009 to C (2010) B (2011) C B ( ) P C B ( ) Nitrogen rate Mean ± SE % ± SE n Mean ± SE % ± SE n Mean ± SE % ± SE n Mean ± SE % ± SE n kg ha 1 $ ha 1 $ ha 1 $ ha 1 $ ha ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ANOVA test# P > F Linear < < < Quadratic < Cropping sequence from 2009 to 2011 was preceding crops (P) canola (C) barley (B). Seven locations include Brandon, Beaverlodge, Indian Head, Lacombe, Lethbridge, Scott, and Swift Current. Means and standard error (SE). Average net revenue percentage and standard error (SE) of nitrogen treatment rate at 0 kg ha 1. n was the number of data observations. # By combining effects of preceding crop residue and location, regression lines for linear or quadratic relationship between the annual net revenue and applied nitrogen rate were tested with SAS Proc Mixed procedure and p values derived from the test were presented. Agronomy Journal Volume 106, Issue

10 crop canola compared to preceding crop wheat (Table 7). The increase (11%) for canola as a preceding crop was lower than the increase (16 28%) for legumes grown for seed as preceding crops (Table 7); N fixing by legumes could increase the soil N level and therefore provide greater benefits to barley in Application of N fertilizer influenced the average annual BNR when data for all sites were combined (Table 8). Significant linear or quadratic responses of BNR to N rates were observed at most sites except Brandon (Fig. 1). When data for the seven sites were combined, BNR increased with increasing N rates applied from 0 to 60 kg ha 1 before levelling off, indicating that optimal N supply was 60 kg ha 1 (Table 8). When data were averaged for the seven sites the most economical treatment for BNR was the combination of GRM residue plus an N rate application of 60 kg ha 1 (Fig. 2). Average Annual Canola Barley Cost and Net Revenue The average annual variable costs, fixed costs, and total costs for production of canola in 2010 and barley in 2011, and average annual canola barley net revenue (CBNR) phases over varied from site to site (Tables 5 and 6). The average annual total cost was higher at Lacombe and lower at Brandon compared to other sites. The canola (2010) and barley (2011) costs were the same with the exception of N fertilizer under each treatment at each site because the same input managements were applied regardless of the preceding crop types (data not shown). The average annual CBNR was higher at Lacombe and lower at Indian Head, Brandon, and Scott compared to the other sites (Table 6), indicating that soil N and environmental conditions for crop growth varied among sites. As previously mentioned, excessive rainfall and flooding in 2011 at Brandon and Indian Head affected barley crop yield and resulted in lower CBNR. The CBNR was lower than CNR, but higher than BNR because canola is a high value crop and its NR expected to be higher than BNR and CBNR. Also, contribution of preceding legume crops to the immediately followed canola in 2010 was greater than contribution of legumes to barley in 2011 (Table 6). Preceding crops in 2009 influenced the average annual CBNR (Fig. 1). Similar to CNR and BNR, the highest average annual CBNR was obtained when faba bean GRM was the preceding crop in 2009 for most sites except Swift Current (Fig. 1 and Table 7). A significant increase in CBNR occurred at Beaverlodge, Indian Head, Lethbridge, and Scott, whereas there was a trend towards an increase at Swift Current (p = 0.081) and Lacombe (p = 0.103) where GRM was the preceding crop. Averaged across locations, the average annual CBNR was increased by 65% for preceding crop GRM compared to preceding crop wheat, indicating significant positive contribution of GRM to the hybrid canola and subsequent barley (Table 7). Faba bean residues, when left on the ground as GRM, provided N to the system by increasing soil residual and mineralizable N, and therefore contributed significantly to the subsequent crops canola and barley. Of the legumes grown for seed as preceding crops in 2009, a significant increase in average annual CBNR occurred for both lentil and field pea only at Beaverlodge and Indian Head. When faba bean was the preceding crop, a trend towards a significant increase in CBNR was observed only at Swift Current (p = 0.063). The increase in CBNR by legumes grown for seed as preceding crops was not significant at most sites. Averaged across locations, the CBNR was increased by 6, 26, and 22% for preceding crops faba bean, lentil, and field pea, respectively, compared to preceding crop wheat (Table 7). When canola was the preceding crop compared to wheat, the CBNR increase was negative for five of the seven sites, except for Scott and Swift Current. Of the five sites, a significant loss in CBNR occurred at Lacombe and Lethbriodge (Table 7). At Scott and Swift Current, a nonsignificant increase in CBNR was observed. Averaged across locations, the CBNR was reduced by 23% for preceding crop canola compared to preceding crop wheat (Table 7). Application rates of N fertilizer influenced the average annual CBNR and the response was generally similar to CNR and BNR (Table 8). The CBNR increased from 0 to 60 kg ha 1 N and then decreased at 120 kg ha 1. At 120 kg ha 1 N, CBNR decreased at Beaverlodge, Lethbridge, and Scott (Fig. 1). The best treatment for CBNR was faba bean GRM, but optimal fertilizer rate was dependent on location and crop type (canola or barley) ranging from 60 to 90 kg ha 1 N application (Fig. 2). The shape of the CBNR response to N rates was parallel among the different preceding crops (Fig. 1), which was expected due to the lack of a preceding crop N rate interaction effect. Averaged across preceding crops, responses of CBNR to N rate were linear or quadratic at Beaverlodge, Lethbridge, and Scott, and linear at Brandon, Indian Head, and Swift current (Fig. 1). At Lacombe, the responses to N rates were not significant. Khakbazan et al. (2011) evaluated several crop yield sufficiency functions and showed that the linear or quadratic form is the most common relationship between applied N rates and crop yields. Preceding Crop Canola Barley Cost and Net Revenue When the economic impact of the preceding crop phase (2009) was considered, higher net revenue for the entire crop system (P C B) was obtained when the preceding crops were legumes (harvested for seed) but not if grown as a GRM. This result is due to the fact that legume has strong N-fixing attributes, but if it is sown as a GRM then a negative NR will be incurred in 2009 due to the absence of revenue. However, if it is instead harvested for seed then the legume is still able to provide some N-fixing benefit to the proceeding crops while providing a positive NR during The average annual variable costs, fixed costs, and total costs for preceding crop (2009) canola (2010) and barley (2011) production in 3 yr as well as average annual preceding crop canola barley net revenue (PCBNR) varied from site to site (Tables 5 and 6). The average total cost was higher at Lacombe and lower at Brandon and Indian Head compared to other sites. The costs over seven sites were different for each of preceding crop types (data not shown). For example, the average total cost was significantly higher for canola production and lower for lentil production compared to other preceding crop productions. The average annual PCBNR was significantly higher at Lacombe and lower at Brandon, Indian Head, Scott, and Swift Current compared to the other sites, indicating that soil N and environmental 2064 Agronomy Journal Volume 106, Issue

11 conditions for crop growth varied among sites. Similar to CNR, BNR, and CBNR, the PCBNR was consistently higher at Lacombe than the other sites (Table 6). The average annual PCBNR was significantly influenced by preceding crops (Fig. 1 and Tables 6 and 7). In contrast to CNR, BNR, and CBNR, the lowest average annual PCBNR was obtained when GRM was the preceding crop in 2009 for most sites (Fig. 1 and Table 7). A significant loss in PCBNR occurred at Brandon, Beaverlodge, Lethbridge, and Scott, whereas there was a trend towards a decrease at Lacombe (p = 0.103) and Swift Current (p = 0.081) where GRM was the preceding crop. Averaged across locations, the PCBNR was decreased by 57% for preceding crop GRM compared to preceding crop wheat (Table 7). In spite of positive yield and economic contribution of GRM to canola production in 2010 and barley in 2011, the benefits were not enough to compensate for the loss of revenue for GRM production in 2009 (O Donovan et al., 2011). Of the legumes grown for seed as preceding crops in 2009 compared to wheat, an increase in PCBNR occurred only at Indian Head when preceding crop was faba bean, lentil, and field pea and at Beaverlodge when preceding crop was field pea. In contrast, a significant loss in PCBNR was observed at Beaverlodge when preceding crop was lentil. Averaged across locations, the PCBNR was increased by 46, 73, and 68% for preceding crops faba bean, lentil, and field pea, compared to preceding crop wheat (Table 7), indicating that legume crops grown for seed were more economical than faba bean grown for GRM. When canola was the preceding crop as compared to wheat, the PCBNR was increased only at Lethbridge (Table 7) and an increased trend occurred at Lacombe (p = 0.063). Averaged across locations, the PCBNR was increased by 11% for preceding crop canola compared to preceding crop wheat (Table 7). The increase (11%) for canola as preceding crop was lower than the increase (46 to 73%) for legumes faba bean, lentil, and field pea grown for seed as preceding crops (Table 7), indicating significant N fixing capacities of legumes and positive contribution to the yield of subsequent crops canola and barley. When sites and preceding crop effects were combined, the response was linear and the PCBNR increased with N application (Table 8). The shape of the PCBNR response to N rates was parallel among the different preceding crops (Fig. 1) consistent with the lack of a significant preceding crop N rate interaction effect. Canola and barley preceded by field pea, lentil, or faba bean GRM accumulated greater amounts of N when compared to canola and barley being preceded by canola or wheat (O Donovan et al., 2014). Based on the combination of higher seed yield and similar or higher protein concentrations harvested after the legume crops, a conclusion can be made that leguminous crops (in this case pea, lentil, and faba bean GRM), provide significant N benefit to succeeding crops (O Donovan et al., 2014). However, if benefits were solely due to differences in N supply then the difference in economic gains after legume vs. non-legume crops would be greatest at low N application rates and decrease as rate of N application increased. Such interactions between preceding crop and N rate were only observed for barley yields in 2011 at Lacombe and Beaverlodge (O Donovan et al., 2014). Averaged across preceding crops, responses of PCBNR to N rates were linear at Brandon, Beaverlodge, Indian Head, and Lethbridge. At Scott, a trend towards a linear response occurred (p = 0.062), whereas at Lacombe and Swift Current, the responses of PCBNR to N rates were not significant (Fig. 1). There was not a significant quadratic response of PCBNR to N rates observed at the seven sites (Fig. 1). Khakbazan et al. (2009b) reported that with the increase in rate of N fertilizer application, the cumulative net revenues significantly decreased with pea wheat cropping sequence. The lack of positive yield responses to N application was due in part to initially high soil N levels accumulated by pea as the preceding crop in the crop rotation. Overall, the treatment of legume crop residues resulted in the best average annual NR compared to preceding crops canola or wheat (Fig. 2). The predicted annual average PCBNR shown in Fig. 1 is based on estimated NR for 2010 and 2011 for different N application rates and actual NR in 2009 because no N treatments were applied in Combining actual NR in 2009 with estimated NR in 2010 and 2011 resulted in curves in Fig. 1 to be less smooth than estimated CNR, BNR, and CBNR. Treatment responses to price changes were evaluated using 2013 farm-gate prices but the ranking of preceding crop in terms of effect on the following crops and N rate management remained the same; therefore, additional results are not reported. SUMMARY AND CONCLUSIONS Results from an enterprise analysis of seven sites in western Canada show that annual CNR, BNR, CBNR, and PCBNR are more profitable when the preceding crop is lentil or field pea vs. wheat or canola. Average annual CNR, BNR, and CBNR were greatest when the preceding crop was faba bean GRM; however, NR was not enough to compensate for loss of income during the GRM production year and thus the PCBNR was least for faba bean GRM. The effects of preceding crop residues on NR diminished over time from canola in 2010 to barley in Over the 3-yr crop rotation, field pea and lentil as preceding crops generally performed better than wheat and canola as preceding crops. Averaged across locations, growing canola as preceding crop resulted in the lowest CNR and CBNR and should be avoided. Results of this study revealed that responses of NR to N rates were mainly linear and quadratic for most locations. The quadratic responses of NR for canola and barley to optimal N indicated that N applied could be reduced below 120 kg ha 1 without diminishing yield at some locations in western Canada. For a linear response the NR was not maximized at the highest N rate (120 kg ha 1 ), while for a quadratic response the NR maximized between 60 and 90 kg ha 1 depending on location and crop type (canola or barley). Therefore, growers could reduce the amount of N applied to canola and barley at some locations in western Canada without diminishing net returns. ACKNOWLEDGMENTS The authors acknowledge the funding for this study provided by the Canola Science Cluster and Agriculture and Agri-Food Canada Sages project. Technical assistance provided by Jennifer Zuidhof, Mike Svistovski, Ray Smith, David Bancur, Gary Winkleman, Duaine Messer, Dean James, Larry Michielsen, Patty Reid, Elizabeth Sroka, Ravindra Ramnarine, Greg Semach, Irene Murray, Randall Brandt, Lorne Nielsen, Arlen Kapiniak, Derek Hunt, and Nathan Berry is greatly appreciated. Agronomy Journal Volume 106, Issue