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Annual Report of Progress
to the
MISSISSIPPI SOYBEAN PROMOTION BOARD
for 1996


Project Title: Determination of Profitability of Soybean Production Practices in Mississippi
Project Leader: Larry G. Heatherly
USDA-ARS Soybean Research Unit
P0 Box 343
Stoneville, MS 38776
Other Participant: Stan R. Spurlock
Dept. of Agricultural Economics
Box 9755
Mississippi State, MS 39762

Objectives

  1. Determine economically best set of production and management practices that include planting date, fall tillage, and irrigation for stale seedbed production of soybean mono-cropped and rotated cropping systems.
  2. Determine weed control practices that sustain or increase profits from stale seedbed early-planted soybean grown with and without irrigation.
  3. Determine economic benefit from irrigation, fall tillage, and rotation with rice for early-season plantings of soybeans.
  4. Determine most profitable weed control options for May planted MG V soybean varieties grown in 20-in. and 40-in. rows.

Significant Accomplishments

Experiments were conducted at Stoneville, MS in 1992, 1994, 1995, and 1996 on Sharkey clay. Row spacing was 20 in. and seeding rate was 5 seed/ft. of row in all experiments. Estimates of costs and returns were developed for each annual cycle of each exper imental unit in each experiment. Total specified expenses (direct and fixed costs, excluding costs for land, management, and general farm overhead) were calculated using actual inputs for each treatment in each year of the experiment. Direct expenses were costs for herbicides, seed, labor, fuel, repair and maintenance, hauling, and interest on operating capital. Fixed expenses were ownership costs for tractors, self-propelled equipment, implements, and the irrigation system. Costs of variable inputs and m achinery were based on prices paid by Mississippi farmers each year. Irrigation costs included the cost of an engine, well, pump, gearhead, generator, fuel tank and lines, and polypipe or flood irrigation setup. Total fixed costs of the irrigation system consisted of annual depreciation, interest on investment, and insurance. Annual depreciation was calculated using the straight-line method with zero salvage value. Annual interest charges were based on one-half of the original investment times an appropri ate interest rate for each year of the study. Insurance was estimated at 1% of the original investment. Income from each experimental unit was calculated each year using the Mississippi seasonal average soybean prices in 1992 ($5.65/bu) and 1994 ($5.60/bu ), and November price in 1995 ($6.58/bu) and 1996 ($6.80). The November soybean price was highly correlated (r = 0.983) with the seasonal average price for the 1984-1993 period. From these calculations, net returns above total specified expenses were determined for each experimental unit in each experiment each year.

WEED CONTROL FOR AND SEED YIELD AND NET RETURNS FROM EARLY-PLANTED, NON-IRRIGATED MG IV SOYBEAN

Methods

A non-irrigated study was conducted in the summers of 1994, 1995, and 1996. MG IV indeterminate soybean (RA 452 in 1994 and 1995, DK 4875 in 1996) was planted on 20 April 1994, 17 April 1995, and 10 April 1996.

Weed control treatments (WTRT) were: I) PRE broadleaf control; 2) POST broadleaf control; 3) PRE and POST broadleaf control; 4) PRE broadleaf and PRE grass control; 5) PRE broadleaf and POST grass control; 6) POST broadleaf and PRE grass control; 7) POST broadleaf and POST grass control; 8) PRE and POST broadleaf control and PRE grass control; 9) PRE and POST broadleaf and POST grass control; and 10) PRE and POST broadleaf and grass control. All treatments remained in place for the duration of the experim ent. Each WTRT had herbicides applied that were intended to minimize weed competition for that particular treatment. Herbicides used are shown in Table 1. An example of inputs are shown in Table 2 (1996 WTRT 10). All PRE herbicides were applied in 20 gal./acre of water. POST broadleaf herbicides were applied in 20 gal./acre of water, and POST grass herbicides were applied in 10 gal./acre of water. Surfactants were used in accordance with herbicide manufacturer's recommendations. POST herbicides were selected and applied to control specific weed problems that were determined on a treatment by treatment basis during the early growing season. The intention was to minimize weed competition as a factor within the constraints of each treatment in the experiment. Weed control costs calculated for each treatment included herbicides, surfactants, and their application. Soybeans were harvested on 14 Sep. 1994, 7 Sep.1995, and 9 Sep.1996.

Results - Table 3

The POST grass treatment was not needed in 1995 and 1996 (no grass present) and thus was not applied to WTRT's 5, 7, 9, and 10.

Weed infestations in all treatments at soybean maturity in all years were below 10%. Yields and net returns resulting from weed control measures in WTRT 6 (POST broadleaf, PRE grass) were the lowest. Yields and net returns resulting from weed control meas ures in WTRT's 2, 3, and 7 (all with POST broadleaf weed control) were intermediate. Yields from WTRT's I (PRE broadleaf only), 4 (PRE broadleaf and grass), 5 (PRE broadleaf/POST grass), and 10 (PRE & POST broadleaf and grass weed control) were among the highest; however, net returns from WTRT's 1 and 5 were the highest. The most expensive weed control treatments (WTRT's 6, 8, 9, and 10) were among the lowest in net returns.

In this 3-yr. study with early plantings of a MG W soybean variety that was grown in narrow rows and not irrigated, the majority of results indicates the following.

  1. When weed control measures vary greatly in expense, yield differences are a poor measure of determine feasibility of weed control inputs. Yield differences, when combined with total cost of production, show a different result than if yields or weed control costs are used alone.
  2. Weed control measures that included only PRE broadleaf control (WTRT 1) or PRE broadleaf + POST grass control (WTRT 5) resulted in one of the highest net returns. As state earlier, a POST grass application was not required in 1995 and 1996, so in essence, the weed control and subsequent weed control costs for WTRT 5 was much like that for WTRT 1.
  3. POST broadleaf + PRE grass weed control measures (WTRT 6) resulted in one of the lowest net returns.
  4. Treatments with POST grass control measures applied only when needed generally provided higher net returns than did those with PRE grass control.
  5. Other combinations of PRE and POST broadleaf and grass herbicides were erratic in their resulting net returns in this 3-yr. study.
  6. In non-irrigated early plantings of MG W varieties in narrow rows on clay soil, use of PRE broadleaf and POST grass herbicides as needed will result in the highest net returns. Any other expenditures are either unnecessary or will result in a loss of money.
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Soybeans in Mississippi
Mississippi Agricultural and Forestry Experiment Station 
Mississippi State University Extension Service
 Division of Agriculture, Forestry and Veterinary Medicine

 
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