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

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CULTURAL PRACTICES FOR SOYBEANS COMPARED (MSMC-3)

Objective: To compare the value of various soybean production inputs in order to answer the question ACan I reduce or eliminate crop input costs without hurting crop yield?"

Summary: The data from two years of experimentation suggest that major efforts to reduce weed control input costs results in lower net returns if weed pressure is high and they are not controlled. Weeds must be controlled or crop yield will suffer.

The data also suggests 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 suggests that one of the commonly used public varieties will not perform as well as one of the better commercially available varieties.

Experimental Treatments: Twelve treatments were selected for the study. The variables included seed source and method of weed control, including cultivation. The seed used included the private brand Northrup King NKS 43B5, public variety Maverick and Afarmer-saved@ seed. The Afarmer saved@ seed was from a 1999 field of beans planted to Registered NKS 43B5.

1. PPI Treflan followed by Epost Galaxy followed by one cultivation (treatments 1,3 and 5)
2. PPI Treflan followed by Epost Galaxy and no cultivation (treatments 7, 9 and 11)
3. PPI Treflan followed by two cultivation's as needed (treatments 2, 4 and 6)
4. PPPI Treflan with no other weed control (treatments 8, 10, and 12)

Methods: 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.

Soybean seed was secured from a local Gentry county dealer. Soybeans were planted at the rate of 196,000 seeds per acre in 36" wide rows on May 11 using a John Deere vacuum type, max-emerge planter.

A John Deere RM4 row crop cultivator was used to cultivate the plots that called for cultivation in the study protocol. Two cultivations were made to treatment 2, 4 & 6. One cultivation on June 1 and the other on June 22. Treatment 1, 3 & 5 were cultivated once on June 22. Weed presence was velvetleaf, giant foxtail and common cocklebur. The foxtail and cocklebur pressure was heavy in the plot area. Velvetleaf pressure was moderate. All herbicide treatments were applied with a C-Farmal rigged with a 12" wide, front-mounted boom. Tee Jet 11002 flat fan nozzles were spaced 18" on the boom. The spray solution was propelled through the nozzles with compressed air. Nozzle pressure was 35 p.s.i.

All plots received a PPI treatment of Treflan applied on May 11, at the rate of 1 quart per acre, which was incorporated twice with a 10' wide, mounted John Deere tandem disk with 20" blades. The second incorporation was made at right angles to the first incorporation.

A "mid-post" application of Galaxy was made to treatments 1, 3, 5, 7, 9 and 11 on June 7. The Galaxy rate was 1 quart per acre along with 1.25% v/v of crop oil concentrate in 20 gallons of spray solution per acre. The soybeans were at V2 growth stage and cockleburs were from just emerged to six inches tall on June 7.

The spring and late summer weather was very dry in 2000. A late-June, three day rain resulted in 3 ¼ inches of precipitation. This rainfall resulted in saturated surface soils for a 4-5 day period.

In-season weed control ratings were taken June 22 and July 11. An August 31 rating was taken to show end-of-season weed control.

2000 Results: The end-of-season weed control ratings are shown below in Table 1. The yield for each of the treatments is shown in Table 2. Table 3 and 4 shows an economic analysis of the nine of the twelve treatments in the study. The treatments without any post activity for weed control were excluded from the economic analysis due to the poor soybean yields.

Discussion: Tables 1 and 2 show that a weed control treatment consisting of PPI Treflan followed by a mid-post application of Galaxy followed by cultivation was necessary for the best weed control and highest yield in the wide-row planted soybeans in this study.

The PPI Treflan, followed by two cultivation's, provided the second best grassy weed control and the second highest soybean yield in the study.

The PPI Treflan followed by Galaxy without cultivation treatments provided good broadleaf weed control but poor giant foxtail control. Weed control ratings taken forty days after planting showed that Treflan alone was controlling only 60-80% of the giant foxtail in the plots. These plots, without broadleaf weed competition, allowed the giant foxtail to thrive and become one of the most limiting factors in the production of soybeans. The lack of giant foxtail control resulted in low soybean yield.

The data in Table 3 show that the most profitable weed control and soybean variety system in the experiment was the one using the least expensive soybean variety along with the PPI Treflan followed by Epost Galaxy and 1 cultivation. The economic data has not been adjusted for statistical significance.

Table 4 illustrates a big difference in economic returns from the Treflan followed by Galaxy, without cultivation, treatments between 1999 and 2000. The primary difference is due to the giant foxtail competition to the soybeans in 2000. Giant foxtail pressure in the 1999 plots was relatively low and Treflan provided better control of the grass during that year. The lack of cultivation in these treatments suggest that this is the riskiest method to use, as the return is highly dependent upon what conditions get "the luck of the draw" for that year. Of course, another conclusion would suggest the importance of scouting to identify pest problems. In this case, scouting would have suggested that a follow-up grass control treatment was needed.

Outreach: These plots were shown and discussed at the 2000 Hundley-Whaley Farm Field Day and Tour. The results of the first year were also included in the Field Day report. The data will be shared with producers at the area soybean producers meeting in Maryville in February of 2001.

Future plans: This is the second year of a planned three-year study. I do not believe we need to repeat this study as-is for one more year. Instead, I propose that we use the last year to economically analyze the following conventional weed control treatments. Only one soybean variety will be used.

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