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© 2006 Plant Management Network. The Feasibility of Winter Wheat Following Soybean in Northern Minnesota Jochum Wiersma, Assistant Professor, 2900 University Avenue, Department of Agronomy & Plant Genetics and Northwest Research and Outreach Center, University of Minnesota, Crookston 56716; Zach Fore, Regional Agronomist, Pioneer Hi-Bred, Johnston, IA 50131; and Hans Kandel, Regional Extension Educator, 251 Owen Hall, 2900 University Avenue, Crookston Regional Extension Center, University of Minnesota, Crookston 56716 Corresponding author: Jochum Wiersma. wiers002@umn.edu Wiersma, J., Fore, Z., and Kandel, H. 2006. The feasibility of winter wheat following soybean in northern Minnesota. Online. Crop Management doi:10.1094/CM-2006-1110-01-RS. Abstract Lack of a suitable previous crop and the risk of winter-kill are two main reasons why winter wheat (Triticum aestivum L.) is a minor crop in Minnesota. Soybean (Glycine max (L.) Merr.) is an excellent previous crop to hard red spring wheat in the Northern Great Plains. The objectives of this research were to determine whether (i) seeding winter wheat immediately following soybean harvest allowed for the winter wheat to get established and (ii) no-till seeding into standing soybean stubble reduced the amount of winter-kill. Winter wheat was successfully established and grown following soybean when more winter-hardy varieties were selected. No-till seeding tended to reduce winter-kill and improved spring vigor for more winter-hardy varieties, and no-till seeding improved grain yield and reduced grain protein content compared to conventional seeding. Introduction The number of acres seeded to winter wheat in Minnesota has historically been less than 1% of the hard red spring wheat (HRSW) acreage (6). Lack of a suitable previous crop and the risk of winter-kill are two main reasons why the winter wheat is a minor crop. Winter wheat offers the advantages of (i) efficient use of labor and equipment by spreading the need for labor, (ii) reducing the need for selective herbicides, and (iii) a higher grain yield potential over HRSW (7). In an economic analysis for southeast North Dakota, winter wheat showed an average return over variable costs of $82.25/acre for winter wheat compared to $66.76/acre for spring wheat over the past decade (Dwight Aakre, Department of Agribusiness and Applied Economics, NDSU, Fargo, ND) (personal communications). The risk of winter-kill can greatly be reduced if and when a snow cover can protect the dormant wheat seedling. Even a few inches of snow greatly reduce the risk of winter-kill (7,11). No-till cropping systems, that maintain as much standing stubble as possible, enhance the ability to trap snow and thus can provide the needed protection for the winter wheat (7). In addition, no-till systems offer the advantage of preserving soil moisture at seeding which enhances the odds that germination and emergence will be faster and more even. Soybean is an excellent previous crop to HRSW in the Northern Great Plains (2,8). However, winter wheat has traditionally been planted in the first half of September. At that time, the soybean crop generally has not yet matured. If soybean is to serve as a previous crop to winter wheat in Minnesota, seeding of winter wheat will need to be delayed by approximately three weeks to the last week of September or first week of October. It is unknown whether this delay in seeding will allow for enough time for the winter wheat to germinate, emerge, and harden to survive the winter period. The objectives of this research were to determine whether (i) seeding winter wheat immediately following soybean harvest allows for the winter wheat to get established and (ii) no-till seeding into standing soybean stubble will reduce the amount of winter-kill. Experimental Design To determine whether seeding winter wheat immediately following soybean harvest is a viable alternative for winter wheat production in Minnesota, an experiment was conducted in 2003 and 2004 in Plummer and Fosston, MN. In each site-year, a split-plot design with 4 replicates was used in which the tillage treatment was the main plot and three winter wheat varieties that differed in winter-hardiness were the split plot. The hard red winter wheat (HRWW) varieties ‘Tandem,’ ‘Ransom,’ and ‘Roughrider’ are rated as moderate, moderately high, and very high for winter-hardiness, respectively (10). The whole-plot dimensions were 30 by 100 ft while the dimensions of the split plot were 10 by 100 ft. The no-till plots were directly seeded with a 10-ft-wide Concord air seeder equipped with 4-inch low-disturbance shovels (Fig. 1). The tilled plots were chisel-plowed and a seedbed was prepared with a field cultivator before being seeded with the same Concord air seeder. The tillage treatments were intended to remove the standing stubble.
The seeding rates were adjusted for each seed lot based on the seed count of the seed lot, the percent germination, and an expected stand loss. The desired plant population was 25 plants/ft2 and the stand loss was assumed to be 15%. The Concord air seeder was calibrated based on the calculated seeding rate for each of the three cultivars. Seed metering was controlled by the on-board Raven 750 variable rate controller (Raven Industries Inc., Sioux Falls, SD). No fertilizer was preplant broadcasted or banded with the Concord air seeder during the seeding operation. The N, P, and K were broadcasted each year just as the winter wheat broke dormancy in the spring according to soil test recommendations with a yield goal of 60 bu/acre. Weeds and early-season fungal diseases were controlled with an application of 0.5 lb ai/acre bromoxynil, 0.5 lb ai/acre MCPA, 0.063 lb ai/acre fenoxaprop-P + safener, and 2 fl oz/acre propiconazole both years. Fall emergence was recorded approximately three weeks after seeding each of the years by randomly selecting two 3.3-ft lengths of the inside 6 rows of each plot. Using the same method, a second stand count was taken in the first week of May. The percent winter-kill was calculated as the difference between the fall and spring stand counts divided by fall stand count times hundred. At the time of the spring stand count, spring vigor was estimated with visual rating with 1 equaling poor growth and 9 equaling excellent growth. To estimate the number of growing degree days for wheat (1) each fall, weather data was collected from the nearest airports. In Fosston, the nearest airport was approximately 5 miles from the field locations. In Plummer, the nearest airport was approximately 10 miles from the field locations. To estimate grain yield, the center 5 ft across the length of the plot was harvested with a small-plot combine. Harvested grain was cleaned with a Clipper Office Tester and Cleaner (Seedburo Equipment Co., Chicago, IL) and grain yield and test weight were expressed on 13.5% moisture basis as bushels per acre and pounds per bushel, respectively. Grain protein content was determined on a half-pound subsample by near infrared transmission using a Tecator Infratec 1229 Grain Analyzer (Foss North America, Inc., Eden Prairie, MN). All effects, except blocks, were considered fixed and analysis of variance was computed using Statistix 8 (Analytical Software, Tallahassee, FL). Main effects and interactions were tested using the appropriate error terms and means were separated using Fisher’s protected LSD at the 5% level of significance (5). Winter Wheat Following Soybean in Northern Minnesota In the fall of 2002, the experiments were planted on 1 October at both locations immediately following harvest of the fully mature soybean crop. The Fosston site was a Knute fine sandy loam (fine-loamy, mixed, superactive, frigid Oxyaquic Argiudolls) while the Plummer site was a Flaming loamy fine sand (sandy, mixed, frigid Oxyaquic Hapludolls). The soybean variety grown in Fosston had a 02 maturity rating and had reached full maturity at time of harvest. Likewise the soybean variety grown in Plummer had a 06 maturity rating and had reached full maturity at time of harvest. In the second year, the experiments were planted on 30 September at both locations immediately following harvest of the soybean crop at the Plummer site. The Fosston site was a Chapett fine sandy loam (fine-loamy, mixed, superactive, frigid Alfic Argiudolls) while the Plummer site was a Foldahl fine sandy loam (sandy over loamy, mixed, superactive, frigid Oxyaquic Hapludolls). Similar to the previous year, the soybean variety grown in Fosston had a 02 maturity rating and had reached full maturity. The field had been harvested on 15 September 2003. The soybean variety grown in Plummer in 2003 had a 06 maturity rating and had reached full maturity at time of harvest. Data was combined across locations but not across years as a significant year by tillage interaction was detected for winter-kill, grain yield, and grain protein content (data not shown). No-till seeding provided more surface residue (Figs. 2 and 3). Estimating the percent residue cover using the calculation method, the no-till seeding left about 35% cover while the conventional seeding method left 12% cover (9).
In each of the four site-years, the winter wheat germinated and emerged before the arrival of cold weather forced dormancy. Based on the stand counts in the fall, the initial stand reduction averaged across seeding method and varieties was 20% and 29% in 2002 and 2003, respectively (Table 1). Across environments, tillage had no effect on emergence and the initial plant population of the three cultivars (Table 1). Tandem tended to have lower initial stand than either Ransom or Roughrider (Table 2). Table 1. Comparisons of means between no-till and conventional tillage winter wheat following soybean combined across two locations in Minnesota in 2003 and 2004.
x 1 = poor, 9 = excellent. y Data of ‘Tandem’ in Plummer not included. Table 2. Comparisons of means among three winter wheat varieties planted following soybean combined across two locations in Minnesota in 2003 and 2004.
x 1 = poor, 9 = excellent. y Single location data. In 2002, the first killing frosts (defined as a minimum air temperature below 28°F) occurred 5 and 13 October in Fosston and Plummer, respectively. In 2003, the first killing frost occurred 1 October at both locations. Despite these low temperatures, the winter wheat emerged. The number of growing degree days (GDD) accumulated by the end of October was approximately 160 GDD in 2002 and 400 GDD in 2003. No appreciable GDD were accumulated past 1 November in either year. Bauer et al. (1) reported that about 180 GDD were needed for seedling to emerge with the first leaf about half of its eventual length extended (Haun growth stage 0.5), and another 130 to 143 GDD were needed to reach one-and-one-half leaf (Haun growth stage 1.5). This is in agreement with the observations made when fall stand counts were taken; in 2002 seedlings had just emerged, while in 2003 the seedling were approaching the 1.5 leaf stage. Using Bauer et al. (1) GGD model with a base temperature of 32°F, analysis of the long-term weather records at both location showed that between 1970 and 2000, an average of approximately 220 GDD were accumulated when planting on 1 October. Planting two weeks earlier on 15 September, more than doubled the average number of GGD (data not shown). Further analysis showed that in approximately 45% of the years between 1970 and 2000, less than 180 GDD were accumulated, compared to 0% when planting occurred two weeks earlier. In 24% of the years between 1970 and 2000, more than 323 GDD were accumulated after 1 October. No-till seeding reduced winter-kill compared to conventional seeding, as the plant population was approximately 1.6 plants/ft2 higher in the spring stand evaluations across varieties. The lack of a tillage by cultivar interaction indicates that all varieties tested benefited equally from the increase in the amount of residue in the no-till treatment. There was, however, a significant cultivar by environment interaction observed (data not shown). This interaction can be explained by the disproportionate increase in winter-kill observed for the variety Tandem in Plummer in 2004. Spring vigor scores tended to be higher for the no-till seeding method (P = 0.103). Similar to the percent winter-kill, the more winter-hardy cultivars Roughrider and Ransom benefited more from the no-till seeding method. Fowler and Gusta (4) reported that a delay in seeding past the optimum window resulted in a decrease in winter-hardiness. The delay in seeding in this experiment did not result in such a large decrease in winter-hardiness that the amount of winter-kill interfered with the yield potential of the crop. Fowler et al. (3) reported that considerable yield compensation will take place if winter-kill occurs. With stands ≥ 65% of the optimum stand, no yield reduction was observed. In one of four site-years Tandem, the moderate winter-hardy variety, showed more than 80% winter-kill and no grain yield data was recorded. No-till seeding yielded a higher grain yield in both years of the experiment when combined across locations (Table 1). Simultaneously, grain protein content was lower for the no-till method. The lower grain protein content may be explained by (i) the higher grain yield and (ii) a reduction of the amount of available N due to more surface residue. Conclusion The delay in seeding from the recommended timeframe in this experiment did not result in such a large decrease in winter-hardiness of Roughrider or Ransom that the amount of winter-kill interfered with the yield potential of the variety. Tandem, the moderate winter-hardy variety showed more than 35% winter-kill at two site-years and no grain yield was recorded for one of those two site-years. Winter wheat was successfully established and grown following soybean when more winter-hardy varieties were selected. Winter wheat varieties with a winter-hardiness rating of moderately high to very high, as reported in the Minnesota Variety Trials Results (10), likely fit this cropping system. The delay in planting is not without risk, as analysis of weather records show that in nearly half the years, less than 180 GDD are accumulated after 1 October. No-till seeding tended to reduce winter-kill and improved spring vigor for more winter-hardy varieties. No-till seeding improved grain yield and reduced grain protein content compared to conventional seeding. Literature Cited 1. Bauer, A., Fanning, C., Enz, J. W., and Eberlein, C. V. 1984. Use of growing-degree days to determine spring wheat growth stages. Ext. Serv. Bull. 37. ND State Univ., Fargo, ND. 2. Berglund, D. R., and Helms, T. C. 2003. Soybean production. Ext. Serv. Bull. A-250 (Revised). ND State Univ., Fargo, ND. 3. Fowler, D. B., Gusta, L. V., Bowren, K. E., Crowle, W. L., Mallough, E. D., McBean, D. S., McIver, R. N. 1976. Potential for winter wheat production in Saskatchewan. Can. J. Plant Sci. 56:45-50. 4. Fowler, D. B., and Gusta, L. V. 1977. Influence of fall growth and development on cold tolerance of rye and wheat. Can. J. of Plant Sci. 57:751-755. 5. McIntosh, M. S. 1983. Analysis of combined experiments. Agron. J. 75:153-155. 6. Minnesota Agricultural Statistics Service. 2003. Minnesota Agricultural Statistics. MN Dept. of Agric., St. Paul, MN. 7. Peel, M. P., and Riveland, N. 1997. Winter wheat production in North Dakota. Ext. Serv. Bull. 33. ND State Univ., Fargo, ND. 8. Peel, M. P. 1998. Crop rotations for increased productivity. Ext. Serv. Bull. 48. ND State Univ., Fargo, ND. 9. Shelton, D. P., Smith, J. A., Pala, P. J., and Kanable, R. 1995. Estimating percent residue cover using the calculation method. Nebguide 93-113. Univ. of Nebr., Lincoln, NE. 10. University of Minnesota. 2003. Minnesota variety trial results (MP108-2003). Univ. of Minn. Agric. Exp. Station, Univ. of Minn., St. Paul, MN. 11. Worzella, W. W., and Cutler, G. H. 1941. Factors affecting cold resistance in winter wheat. Agron. J. 33:221-230. |
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