Periodic Response of Soybean Yields and Economic Returns to Long-Term No-Tillage

NT will reduce soybean grain yields and economic returns, particularly during the first few years of adoption. Farmers have been encouraged to adopt no-tillage (NT) because Soybean grain yield response to NT systems depends of its positive environmental effects compared with other conservation tillage systems. Nevertheless, poor crop performance under NT manmainly upon soil drainage and previous crop characterisagement has been reported in both shortand long-term experiments. tics (Dick and van Doren, 1985; Guy and Oplinger, This study was conducted on six different soils (a poorly drained 1989). In general, well-drained soils, crop rotation, and Taintor soil near Burlington, a moderately well-drained Kenyon soil more southern latitudes provide significant benefit to near Nashua, a well-drained Clarion soil near Newell, a well-drained NT soybean production compared with poorly drained Galva soil near Sutherland, and a well-drained Nira soil and a poorly soils, continuous cropping, and northern latitudes (Grifdrained Kalona soil near Crawfordsville) in Iowa during 1978 to 2001. fith and Wollenhaupt, 1994). Chase and Duffy (1991), Soybean [Glycine max (L.) Merr.] response to long-term NT managein a 10-yr Iowa tillage study, reported that NT and MP ment was evaluated by 5-yr periods and on the average over the entire produced similar soybean grain yields in a corn–soybean study in terms of grain yields and economic returns. The design of rotation on a moderately well-drained and moderately the field experiments was a randomized complete block or split plot. Eight tillage systems, including NT, moldboard plow, chisel plow, permeable loam soil. Brown et al. (1989) found that ridge tillage, alternative tillage, reduced tillage, field cultivation, and soybean grain yields did not differ between NT and MP tillage-plant were investigated in a corn (Zea mays L.)–soybean rotawhen averaged over an 8-yr tillage study on a silt clay tion. Differences between NT and other tillage systems in both soyloam soil in Iowa. In two 3-yr tillage studies in Wisconbean grain yields and economic returns remained the same over the sin, NT and MP produced similar soybean grain yields entire period of each study, ranging from 8 to 15 yr. No-tillage generon silty loam soils in a corn–soybean or corn–soybean– ally had less than 5% yield decrease and equal or greater economic wheat (Triticum aestivum L.) rotation (Meese et al., returns compared with other tillage systems on well-drained soils 1991; Lund et al., 1993). However, West et al. (1996) during each 5-yr period and when averaged over the entire study. reported an 8% reduction in soybean grain yields under Therefore, economic returns favor the adoption of NT for soybean NT compared with MP in a corn–soybean rotation averproduction from both shortand long-term perspectives for welldrained soils in Iowa. aged over a 20-yr study on a poorly drained silty clay loam soil in Indiana. McIsaac et al. (1990) found, in a 9-yr tillage study on a poorly drained soil in Illinois, that NT soybean grain yields were less than yields with C tillage systems, in general, offer proother tillage systems. Delayed crop growth and developnounced advantages over moldboard plow (MP) ment and increased difficulties in soil and pest managein conserving soil and water, sustaining soil productivity, ment have been cited as the cause for less-than-desirable and reducing labor and energy requirements (Unger or inconsistent soybean yield performance under NT and McCalla, 1980; Conserv. Tillage Inf. Cent., 1983). management. No-tillage possesses a greater advantage than other conThe magnitude of economic returns for various tillage servation tillage systems because it results in less soil systems is the most important evidence of the viability disturbance and greater residue coverage on the soil and superiority of one tillage system over another. Acsurface. ceptance of NT for soybean production compared with No-tillage production for all crops has almost doubled MP and other conservation tillage systems depends in the United States during the last decade. In 2002, more on its profitability than just grain yields. Soybean nearly 20% of cropland was planted under NT (Conserv. profitability depends on the revenue (soybean grain Technol. Inf. Cent., 2003). Although 33% of soybean yields price for soybean grain) and total production fields in the United States were under NT management cost. In general, NT systems have reduced costs of labor, in 2002, which is greater than the NT corn percentage fuel, and machinery inputs but increased costs of pesti(18%), there is still a potential to increase NT soybean cides and increased management to maintain or increase acreages. Even with the stated advantage of NT, some yields. Economic returns for NT compared with other notable difficulties remain that have hampered the adoptillage systems vary with many factors, such as managetion of NT practices for soybean production (Nowak, ment practices, crop rotation, and labor costs (Duffy 1983). One of the main concerns is the perception that and Hanthorn 1984; Chase and Duffy, 1991). Liu and Duffy (1996) found that NT resulted in greater ecoDep. of Agron., Iowa State Univ., Ames, IA 50011-1010. Received 16 June 2003. *Corresponding author ([email protected]). Abbreviations: AL, alternative tillage; CP, chisel plow; FC, field cultiPublished in Agron. J. 96:723–733 (2004).  American Society of Agronomy vation; MP, moldboard plow; NT, no-tillage; RDT, reduced tillage; RT, ridge tillage; TP, tillage-plant. 677 S. Segoe Rd., Madison, WI 53711 USA