Published in Agron. J. 96:281-284 (2004).
© American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
PRODUCTION PAPER
Utility of Interseeded Winter Cereal Rye in Organic Soybean Production Systems
Kurt D. Thelen*,
Dale R. Mutch and
Todd E. Martin
Dep. of Crop and Soil Sci., Michigan State Univ., East Lansing, MI 48824-1325 and Kellogg Biol. Stn., 3700 E. Gull Lake Drive, Hickory Corners, MI 49060-9516
* Corresponding author (thelenk3{at}msu.edu).
Received for publication March 14, 2003.
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ABSTRACT
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Soybean [Glycine max (L.) Merr.] growers using organic production systems have predominately been limited to mechanical cultivation for weed control. Interseeded cover crops such as winter cereal rye (Secale cereale L.) have been used in conventional soybean production systems in conjunction with herbicides to reduce tillage and cultivation operations. The objective of this study was to determine if high soybean planting populations in drill-planted (19-cm row) systems or a single mechanical cultivation in row-planted (76-cm row) systems could facilitate the use of interseeded rye in organic soybean production systems. Interseeded winter cereal rye decreased soybean grain yield in 2 of 3 yr in the drill-planted system by 22 and 17%, respectively, and in all 3 yr of the row-planted system by 23, 27, and 23%, respectively. Moisture stress from the interseeded rye was a predominate factor in soybean grain yield reduction. In 2000, the soybean planting population was inversely correlated with late-season biomass of interseeded rye. However, during the drier years of 2001 and 2002, increasing soybean planting density did not significantly reduce late-season biomass of interseeded rye. The interseeded rye reduced late-season weed biomass in both the drill-planted and row systems in 2001. Removal of the interseeded rye with mechanical cultivation in the row system when the soybean was at the V4 growth stage was ineffective in 2000 but increased soybean grain yield by 1142 and 746 kg ha–1, respectively, in 2001 and 2002. These results suggest that some means of controlling winter cereal rye growth is necessary for effective management across a range of precipitation levels.
Abbreviations: DAP, days after planting
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INTRODUCTION
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ORGANIC GROWERS typically rely on tillage for weed control in soybean production systems. Disadvantages with crop systems that rely on tillage include increased erosion risk (Edwards et al., 1993; McGregor et al., 1999), loss of soil structure, decrease in soil organic C levels (Studdert and Echeverria, 2000), and increases in machinery and fuel costs (Lu et al., 1999). Weil et al. (1993) found that mineralizable N decreased with increasing intensity of tillage in five Maryland cropping systems.
Spring-planted winter cereal rye, interseeded with soybean, has been identified as a possible alternative weed control method in conventional soybean production systems. Unlike fall-planted winter cereal rye, spring-planted winter cereal rye remains vegetative and does not rapidly elongate (Ateh and Doll, 1996). The less aggressive growing pattern of spring-planted winter rye makes it more appealing as an interseeded cover crop than fall-planted winter rye. Conceivably, a high soybean planting density could be used to further reduce the competitive effect of the interseeded winter cereal rye.
The use of cereal rye in field cropping systems has many advantages, including increased surface residue for erosion control (Kessavalou and Walters, 1997), reduced soil compaction (Raper et al., 2000), and suppressed weed emergence (Blum et al., 1997). In conventional soybean production systems, the availability of herbicides to control the interseeded rye affords the grower a management option in the event that the rye becomes too competitive with interseeded soybean. The objective of this study was to determine if interseeding winter cereal rye in the spring with soybean is a viable management practice in organic drilled and row-planted soybean production systems.
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MATERIALS AND METHODS
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Field research was conducted at the W.K. Kellogg Biological Station in Hickory Corners, MI. The soil is a mixture of Kalamazoo (fine-loamy, mixed, mesic Typic Hapludalfs) and Oshtemo (coarse-loamy, mixed, mesic Typic Hapludalfs) sandy loams. The depth of the Ap horizon is 20 to 25 cm, and pH ranged from 6.3 to 6.8. The experimental fields are certified organic by the Organic Crop Improvement Association (OCIA Int., Lincoln, NE). Corn (Zea mays L.) was the previous crop each year.
Two separate experiments were conducted. One experiment investigated a drill-planted system using 19-cm row spacing, and the second experiment involved a row-planted system using 76-cm row spacing. The experimental design for each study was a randomized complete block with four replications. The treatment design in each study was a two-factor factorial. In the drill-planted system, the first factor was soybean planting density (444600, 889200, and 1333800 plants ha–1), and the second factor was the presence or absence of interseeded winter cereal rye. In the row-planted system, the first factor was whether or not row cultivation was used, and the second factor was the presence or absence of interseeded rye. Plot size in the 19-cm-row drill system was 46 by 3 m, 34 by 3 m, and 15 by 3 m in 2000, 2001, and 2002, respectively. In the 76-cm-row system, plot size was 46 by 5 m, 34 by 5 m, and 15 by 5 m, respectively, in 2000, 2001, and 2002. In both systems, the interseeded winter cereal rye treatments consisted of 125 kg ha–1 rye (‘Wheeler’, Michigan Agric. Exp. Stn., East Lansing, MI) planted with a drill in 19-cm row widths the same day the soybean was planted. In the row-planted experiment, row cultivation (Model 183 cultivator, Case Int., Racine, WI) was conducted on the indicated treatments when the soybean was approximately at the V4 growth stage.
The soybean variety used was ‘NK 19-T19’. In each year of the study, all plots were rotary-hoed (Model 181MT, Case Int., Racine, WI). Consistent with local organic practices, the rotary hoeing occurred 7, 12, and 21 d after planting (DAP) in 2000; 9, 19, and 25 DAP in 2001; and 11, 13, and 19 DAP in 2002. Planting dates were 7 June, 20 May, and 30 May for 2000, 2001, and 2002, respectively. In all experiments, no herbicides were used, and management was consistent with certified production requirements (OCIA Int., Lincoln NE).
Late-season weed, soybean, and rye biomass weights were taken all 3 yr of the study, with the exception of the row-planted experiment in 2000 when biomass measurements were not taken. In 2001 and 2002, an additional early-season measurement of dry weight biomass was made on 27 June 2001 and 17 July 2002. The late-season weed, soybean, and rye biomass samples were taken on 18 Aug. 2000, 20 Aug. 2001, and 13 Sept. 2002. Plant biomass was determined by hand-clipping plants at ground level from one, four, and two quadrants per plot in 2000, 2001, and 2002, respectively. Quadrant sizes were 0.35 m2 for soybean and 0.37 m2 for weed in the 19-cm-row width soybean plots. In the 76-cm-row soybean plots, quadrant sizes were 0.37 m2 for weed and 0.46 m2 for soybean. Plants were separated, weighed, and placed in a forced-air dryer until a constant weight was observed. The dry plant material was then reweighed to calculate total dry matter. Soybean was harvested with a plot combine (Winterstieger Nurserymaster, Zentrale, Austria) from the center 1.2-m transect of each plot, and yield was adjusted to 13% moisture. All data were analyzed with analysis of variance (ANOVA) using the PROC GLM procedure in the SAS Statistical Software Package version 8.2 (SAS Inst., 2002). Mean separation between variables was obtained by Tukey's Least Significant Difference Test. Effects were considered significant at P < 0.05.
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RESULTS AND DISCUSSION
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Drill-Planted System
Interseeded winter cereal rye had a significant effect on soybean yield and early- and late-season soybean biomass in both 2001 and 2002 (Table 1). Evaluation of the main effects (Table 2) shows that the presence of interseeded rye reduced soybean yield by 22 and 17% in 2001 and 2002, respectively, when averaged across the three levels of soybean planting densities. However, the presence of rye did not affect soybean plant density at harvest. In 2000, the interseeded rye did not affect soybean yield or biomass; however, increasing soybean planting population did reduce late-season rye biomass. This may be associated with the higher precipitation levels during the 2000 growing season (Table 3), which may have diminished the competitive effect of the interseeded rye. This result suggests that in years with normal to below-normal precipitation levels, competition from interseeded rye in a drill-planted soybean system may reduce the grain yield potential of soybean despite the limited effect on soybean plant density at harvest. This is consistent with the findings of Ateh and Doll (1996), who reported reduced soybean vigor when interseeded with rye. These results also support the concept proposed by Stanislaus and Cheng (2002), who reported on the utility of a cover crop that self-destructs in response to an environmental cue. This type of cover crop self-destruction trait could eliminate the competitive effect of the cover crop yet still maintain the advantages associated with less tillage and low inputs of an organically farmed system.
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Table 2. Soybean yield as affected by soybean planting density and interseeded winter cereal rye in a 19-cm drill-planted system. Effect of soybean planting density is averaged across rye treatments, and effect of rye planting is averaged across all soybean planting densities.
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Table 3. Annual precipitation levels at the W.K. Kellogg Biological Station compared with 30-yr means (1971–2000).
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Soybean planting density did not affect early-season weed biomass and affected late-season weed biomass in only year 2000 of the study (Table 1). Even though the soybean planting density effect on weed biomass was statistically significant in 1 out of 3 yr, treatment effects shown in Table 4 indicate a trend for decreased weed biomass at higher soybean plant populations. Soybean planting density, however, significantly affected grain yield in all 3 yr of the study. Increased soybean planting density consistently resulted in higher grain yield (Table 4). The two soybean planting density levels of 889200 and 1333800 plants ha–1 are greater than those generally recommended for conventional herbicide-based management systems (Ennin and Clegg, 2001). However, the favorable yield response to high soybean planting density levels in this study is consistent with results reported by Holshouser and Whittaker (2002). They found a soybean plant density of only 208000 plants ha–1, adequate for maximum yield at a site subjected to a brief stress period. However, a soybean plant density of more than 600000 plants ha–1 was required for maximum yield when the site was subjected to more severe drought stress. These results demonstrate that under conditions of high plant competitiveness, such as the system evaluated in this experiment utilizing narrow-row organic production and interseeded rye, a high soybean planting density is required to maximize yield.
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Table 4. Early- and late-season biomass, plant density at harvest, and grain yield of soybean in a drill-planted (19-cm) system, as affected by soybean planting density and interseeded winter rye.
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Row-Planted System
In the 76-cm-row plant system, the interseeded rye adversely affected soybean yield in all 3 yr of the study (Table 1). In 2001 and 2002, the interseeded rye significantly reduced early-season soybean biomass. However, the interseeded rye only reduced late-season soybean biomass in 2001. This result may also be attributed to rainfall patterns. During the 2002 growing season, 111 mm of rainfall was recorded during the month of July compared with 34 mm in July 2001. The additional rainfall in July of 2002 may have facilitated soybean plant recovery from the initial rye competition. The initial competition in 2002, however, was severe enough to reduce soybean yield. Yields were greater than those recorded in 2001 when less than one-third of the 2002 rainfall was recorded (Table 5). Similar to the drill-planted system, the interseeded rye did not affect soybean plant density at harvest.
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Table 5. Early- and late-season biomass, plant density at harvest, and grain yield of soybean in a row-planted (76-cm) system, as affected by mechanical cultivation and interseeded winter cereal rye.
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Cultivation in the row-planted system improved soybean yield in 2001 and 2002 but did not affect yield in 2000 (Table 6). This result may be attributable to the higher precipitation levels during the 2000 growing season when there was adequate moisture to minimize competition from interseeded rye and weeds. The yield benefit from cultivation was more pronounced in 2001, which as stated previously was characterized by a very dry mid–growing (July) season. During 2001, cultivation significantly increased late-season soybean biomass and reduced late-season biomass of interseeded rye and weeds. In 2002, when low rainfall in June was followed by adequate precipitation in July, cultivation significantly increased early-season soybean biomass and decreased early-season rye and weed biomass. The competitive advantage of soybean over rye was apparent during the dry month of June 2002. Cultivation was associated with greater soybean biomass early in the 2002 growing season. With the above-normal July 2002 rainfall, however, regrowth of rye and late-emerging weeds negated the early-season competitive advantage from cultivation. The early-season effect of cultivation was sufficient to improve soybean yield over plots where no mechanical weed control was used.
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Table 6. Soybean yield as affected by mechanical cultivation and interseeded winter cereal rye planting density in the 76-cm row-planted system. Effect of cultivation is averaged across rye treatments, and effect of interseeded winter cereal rye is averaged across cultivation treatments.
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The significant rye x cultivation interaction for late-season rye biomass in 2001 (Table 1) may be attributed to the increased competitiveness of the rye that year, which resulted in greater rye biomass in the uncultivated plots. Similarly, because the rye was very competitive to both weeds and soybean in 2001, the significant rye x cultivation interaction for late-season weed biomass is a result of the compounded effect of the interseeded rye plus cultivation. In the absence of either practice, weed biomass was very high, reflecting the lack of competition from rye, and conversely, in the presence of cultivation and rye, late-season weed biomass was reduced.
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CONCLUSIONS
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Interseeded winter cereal rye decreased soybean yield in 2 of 3 yr in a 19-cm drill-planted system and in all 3 yr of the 76-cm row-planted organic soybean system. In the year that the interseeded winter cereal rye did not reduce soybean yield in the drill-planted system (2000), above-average precipitation was recorded during the growing season, suggesting that moisture stress was a predominant factor in the observed soybean grain yield reduction in 2001 and 2002. In 2000, increasing soybean planting populations were inversely correlated with late-season rye biomass. However, during the drier years of 2001 and 2002, increasing soybean planting density did not significantly reduce late-season rye biomass. The interseeded rye reduced late-season weed biomass in both the drill-planted and row systems in 2001. Removal of the interseeded rye with mechanical cultivation in the row system resulted in an increase in soybean yield. This result suggests that some means of terminating the interseeded rye is necessary for effective management across a range of precipitation levels. In 76-cm-row organic soybean production systems, mechanical cultivation would be an approved practice for terminating rye growth. However, in 19-cm drill-planted systems, new technology that meets the regulatory criteria for organic production is needed to effectively terminate the interseeded rye and alleviate moisture stress–related concerns.
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REFERENCES
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- Ateh, C.M., and J.D. Doll. 1996. Spring-planted winter rye (Secale cereale) as a living mulch to control weeds in soybean (Glycine max). Weed Technol. 10:347–353.
- Blum, U., L.D. King, T.M. Gerig, M.E. Lehman, and A.D. Worsham. 1997. Effects of clover and small grain cover crops and tillage techniques on seedling emergence of some dicotyledonous weed species. Am. J. Altern. Agric. 12:146–161.
- Edwards, W.M., G.B. Triplett, D.M. Van Doren, L.B. Owens, C.E. Redmond, and W.A. Dick. 1993. Tillage studies with a corn–soybean rotation: Hydrology and sediment loss. Soil Sci. Soc. Am. J. 57:1051–1055.[Abstract/Free Full Text]
- Ennin, S.A., and M.D. Clegg. 2001. Effect of soybean plant populations in a soybean and maize rotation. Agron. J. 93:396–403.[Abstract/Free Full Text]
- Holshouser, D.L., and J.P. Whittaker. 2002. Plant population and row-spacing effects on early soybean production systems in the Mid-Atlantic USA. Agron. J. 94:603–611.[Abstract/Free Full Text]
- Kessavalou, A., and D.T. Walters. 1997. Winter rye as a cover crop following soybean under conservation tillage. Agron. J. 89:68–74.[Abstract/Free Full Text]
- Lu, Y.C., B. Watkins, and J. Teasdale. 1999. Economic analysis of sustainable agricultural cropping systems for Mid-Atlantic States. J. Sustainable Agric. 15:77–93.
- McGregor, K.C., R.F. Cullum, and C.K. Mutchler. 1999. Long-term management effects on runoff, erosion, and crop production. Trans. ASAE 42:99–105.
- Raper, R.L., D.W. Reeves, E.B. Schwab, and C.H. Burmester. 2000. Reducing soil compaction of Tennessee Valley soils in conservation tillage systems. J. Cotton Sci. 4:84–90.
- SAS Institute. 2002. SAS/STAT user's guide. Version 8.2. SAS Inst., Cary, NC.
- Stanislaus, M.A., and C.L. Cheng. 2002. Genetically engineered self-destruction: An alternative to herbicides for cover crop systems. Weed Sci. 50:794–801.
- Studdert, G.A., and H.E. Echeverria. 2000. Crop rotations and nitrogen fertilization to manage soil organic carbon dynamics. Soil Sci. Soc. Am. J. 64:1496–1503.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
