Soybeans: Tillage Options

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Pub 811: Agronomy Guide > Soybeans> Tillage Options

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The wide adaptation of soybeans to various tillage systems, particularly no-till, has contributed to the expansion in soybean acreage. Approximately two-thirds of the soybean crop is grown under no-till systems or with reduced tillage systems. Field experience and research trials have shown similar yields between tillage systems. Management of the tillage system used is as important as the actual system selected.

¹ Average of nine sites per year. University of Guelph (1998-2000). Trials were conducted on clay loam, silty-clay loam, silt loam and Guelph loam soil types. Spring zone-tillage conducted approximately 1 day prior to planting.
² Where the difference between two treatments exceeds 2.4 bu/acre, there is a less than 1-in-20 chance that it is due to random variation.

No-Till and Minimum Tillage

Ontario tillage research found that no-till soybean yields were similar to the fall moldboard plow in row widths of 56 cm (22.5 in.) or less and in twin rows (see Table 2-1, Soybean Yield Response Under Various Tillage Systems). Although the yields were comparable between the two tillage systems, no-till input costs were often lower and profit higher. Where single 76-cm (30-in.) rows were used, moldboard plowing produced the highest yields. When soybeans were planted in twin rows, soybean yields improved over 76-cm (30-in.) rows for all tillage systems. In this study, zone tillage showed no significant yield improvement over no-till. Some Ontario research trials have shown a small yield advantage (0.13 t/ha, 2 bu/acre) to conventional tillage over no-till. In general, there is a greater positive response to tillage in fields with a poor crop rotation compared to a rotation with fewer soybeans.

The keys to successful no-till production are to minimize compaction, manage residue and plant only when soil conditions are fit. The adoption of no-till on heavy textured soil types (clay, silty clay loam or silty clay) can be more challenging than on lighter soils. In some years, growers have experienced reduced no-till soybean yields on these soil types compared to conventional tillage. However, as demonstrated in Table 2-2, Soybean Yields for Ridgetown College, University of Guelph, 1992-2000, research on Brookston clay soils resulted in equal yields for no-till and fall moldboard tillage over the long term.

¹Values followed by the same letter are not significantly different at the 5% level.

Planting in no-till fields is often done later than in conventionally tilled fields due to wetter and cooler soil conditions. Some producers mitigate this problem with springtime minimal tillage (pre-tillage). Tillage with a one-pass coulter unit has shown a small yield benefit over straight no-till. Coulters run at the time of planting have also shown a marginal benefit if run at a depth of 9 cm (3.5 in.). Coulters operated at a depth of 3.8 cm (1.5 in.) showed no yield gain in the research summarized in Table 2-3, Soybean Yield Response to Spring Minimal Tillage (2003-05).

¹ Values based on 40 trials seeded with a JD 1560 no-till drill. Coulters run at seeding time in the row (2-cm or 0.75-in. coulters). Pre-tillage coulter unit operated 1-3 days before seeding at a depth of 9 cm (4.5 cm or 1.75 in. coulters). No coulters run on JD drill for pre-tillage treatment.
² Values followed by the same letter are not significantly different.

When soybeans follow a cereal crop, pay special attention to the management of cereal residue - beginning at harvest - to avoid problems with soybean establishment. The best action is to remove the straw and spread the chaff evenly. In research trials done at the University of Guelph, removal of the wheat straw improved seedbed conditions, stand establishment, growth and yield of no-till soybeans. The results are shown in Table 2-4, Effect of Tillage and Wheat Residue Management on Soybean Yields (1994-96). Cereal residue can form a mat that slows soil warming and drying in the spring. This can delay soybean planting, reduce soybean emergence and early growth, and lead to increased damage from slugs. Minimum tillage in the fall or spring without the need for secondary tillage improves seedbed conditions and creates looser, finer soil to improve early soybean growth, while maintaining adequate residue to reduce erosion.

It is best to avoid tillage along highly erodable knolls and slopes. In these situations, it may be sensible to use tillage only where the soil routinely remains cooler or wetter in the spring.

Note: Stubble heights were approximately 20-30 cm (10-12 in.) except for plots where stubble was cut and removed.

Soil types:
Centralia: loam, clay loam.
Wyoming: silty clay, silty clay-loam.
Soybeans were seeded with a JD 700 conservation planter equipped with a single 1.25-in. coulter. The no-till planter was equipped with tine row cleaners.

Crop Rotation Considerations

Soybeans are very responsive to crop rotation. Table 2-5, Soybean Yield Response Under Various Crop Rotations (1997-2000),summarizes the results of rotation studies conducted at Ridgetown College, University of Guelph. A rotation of soybeans, winter wheat and corn provided the greatest yield response. The continuous soybean rotation had the lowest yield. A short rotation leads to a build-up of disease and other long-term problems. Soybean cyst nematode (SCN) populations can increase rapidly, further reducing yields (see Soybean Cyst Nematode). Maintaining a 3-4-year rotation with other non-host crops will also reduce the incidence of white mould. In fields with a history of phytophthora root rot, a short rotation contributes to an increase in the severity and number of races of the disease. The repeated use of Group 2 Herbicides-ALS inhibitors will encourage the spread of Group 2-resistant weeds.

¹ These dates are for physiological maturity. Combining would be 3-10 days after these dates.

• Select a variety that requires about 100-200 heat units less than the number available in your area. Research from Ridgetown College, University of Guelph (1990-99), indicated that a variety requiring 100 CHUs less than a full-season variety advanced the maturity by an average of 5 days (range: 3-7 days). Going a further 100 CHUs less advanced the maturity 9 days compared to full-season varieties (see Table 2-6, Soybean Maturity Dates for 2,950-, 3,050- and 3,150-Heat Unit Varieties (1990-99)).
• Plant the soybean crop early, as late planting will delay wheat planting.
• The wheat planting date can be calculated using the soybean planting date and the days to maturity of the soybean variety.
• Select a full-season soybean variety if broadcasting the winter wheat into a standing crop.
• Refer to the winter wheat planting dates in Planting Dates.

For more information on soybean crop rotations and precautions under different tillage systems, see Crop Rotation.