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Bruce Burdick
1109 S. Birch St.
Albany, MO 64402
660-726-5610
Email: BurdickB@missouri.edu

Hundley-Whaley Center phone
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CULTURAL PRACTICES FOR SOYBEANS COMPARED (MSMC-3)

Objective: To compare thirteen conventional soybean weed control treatments and to determine their profitability.

Summary: The treatments in this study were changed in 2001. This year's test provided data that indicates that producers who choose conventional soybean varieties have numerous options for effective and economic weed control. A banded postemergence application of a broad spectrum herbicide during the first cultivation of wide-rowed soybeans can result in low out-of-pocket weed control costs along with high soybean performance.

The data from the two previous years (1999-2000) of experimentation suggest that major efforts to reduce weed control input costs on conventional varieties of soybeans resulted in lower net returns if weed pressure was high and if the weeds were not controlled. The bottom line is that early emerging weeds must be controlled or crop yield will suffer.

The data also suggested that farmer-saved seed of higher yielding varieties, where "saving" can be done legally, provides a higher net return than the same soybean genetics purchased at a higher price as a registered variety from a commercial company. The two-year data also suggested that one of the commonly used public varieties would not perform as well as one of the better commercially available varieties.

Experimental Treatments: Treatments were changed in 2001 to reflect changes in production of conventional soybean varieties. The 2001 treatments are in Table 1 below.

Methods: A more detailed listing of the inputs that went into the treatments are in Table 2 below.

Herbicide rates were:

The post herbicides, and the rates used, were chosen based on weeds present and weed size when the plots were scouted.

The study was designed as a split plot experiment with six replications. Plot size was 12' wide and 30' long. Gylling's Agriculture Research Manager 6.1 was used to design and analyze the study.

Prairie Brand 3550 was used in the 2001 experiment. The soybeans were planted at 200,000 seeds per acre. Treatments 1-9 were planted in 36" wide rows using a John Deere vacuum type, MaxEmerge planter. Treatments 10-13 were planted with a Tye drill with 10" row spacing. Planting date was May 25. The seedbed was conventionally tilled prior to planting and the soil was moist and mellow at planting time.

A John Deere RM4 four-row crop cultivator was used to cultivate the plots that called for cultivation in the study protocol. Two cultivations were made to treatments 2 & 8. One cultivation on June 26 and the other on July 13. Treatment 5 was cultivated one time only on June 26 and treatments 3 & 9 were cultivated one time only on July 13.

All herbicide treatments were applied with a C-Farmal equipped with a 12' wide, front-mounted boom. Tee Jet 11002 flat fan nozzles were spaced 18" on the boom to make pre-emergence and broadcast post emergence applications. TeeJet 8002E nozzles were used to make the banded application to treatment 2. The herbicide carrier was water. The spray solution was propelled through the nozzles with compressed air. Nozzle pressure was 35 p.s.i.

The pre-emergence treatments were made on May 25. The Mpost only treatments were made on June 26 to weeds that ranged in size from 2" tall to 16" tall and that were rated moderate to heavy in pressure. The Mpost treatments that followed a pre-emergence treatment were made on July 3 to weeds that ranged from 4-18" tall and were rated light in pressure.

The spring was mildly wet in 2001, followed by a summer that was relatively dry.

Weed control ratings were taken June 27, July 20 and August 3. The plots were harvested on October 26.

Results: Weeds present in the untreated plots were giant foxtail, lambsquarters, common waterhemp, sunflower and cocklebur. The pre-emergence Gauntlet treatment did a good job of controlling most of the weeds in the plots.

The end-of season ratings were taken on August 3. The soybeans were 30-40 inches tall. The dominant weed was sunflower. Table 3 shows end-of-season weed control and crop yields for the treatments.

Discussion: This year's data suggest that soybean producers who desire to grow conventionally bred soybeans do have many options for successful weed control. Of the 13 treatments in the trial, nine provided soybean yields that were statistically non-significant from the top yielding treatment. Eight of the treatments provided an economic return that was statistically non-significant from the treatment with the highest economic return.

There were some surprising differences in the test. When drilled and wide-rowed treatments with the same pre-emergence weed control treatment were compared (T4 & 10), the wide rowed soybeans performed significantly better than the drilled soybeans (44 verses 33 bu/acre).

Cultivation timing did impact overall weed control and profitability of production. The pre-emergence Gauntlet treatment (T4) yielded 44 bu/acre. The June 26 cultivation made to the beans with the same pre treatment (T5) yielded 46 bu/acre, and the July 13 cultivation made to the same pre treatment (T6) yielded 52 bu/acre. While not statistically significant, the pre Gauntlet followed by the July 13 cultivation was the most profitable treatment (see Table 4).

Producers who have the necessary labor and equipment, and who need to reduce soybean production costs, might consider the wide-rowed beans with a banded mid-post application of a broad-spectrum herbicide (T2). The out-of-pocket cost for herbicides was reduced to $7.30 per acre, and the soybeans performed well (49 bu/acre).

The two top yielding (54 bu/acre) treatments in the study were the ones that received both a pre-emergence and a mid-post herbicide application (T7 & 12).

There was no indication that two cultivations, one on June 26 and another on July 13, were more advantageous for final weed control or crop yield than one cultivation on July 13 when soybeans were grown in wide rows and when Gauntlet was used as a pre-emergence herbicide (T8 & 9).

The pre-emergence application of Gauntlet to drilled soybeans did not provide a satisfactory method of weed control (T10).

1. Cultivation cost of $7.00 (adjusted rate) from 1997 Custom Rate for Farm Services in Missouri - G302 (revised 3/98).
2. Total cost here is the cost of weed control which included a $5.00 per application charge for each application. Herbicide values based on 2001 survey of north Missouri dealers.
3. Based on a value of $5.00/bushel selling price (selling price + LDP)
4. The amount left to pay for all expenses after weed control expenses have been paid
5. Banded application - 1/3 amount of herbicide used. Plus $3.00 application charge for cultivation application of treatment