Malheur Experiment Station Information for Sustainable Agriculture

Soybean is a potentially valuable new crop for Oregon. Soybean could provide a high quality protein for animal nutrition and oil for human consumption, both of which are in short supply in the Pacific Northwest. In addition, edible or vegetable soybean production could be exported to the Orient and provide a raw material for specialized food products. Soybean is valuable as a rotation crop because of the soil-improving qualities of its residues and its N2 -fixing capability. Because of the high-value irrigated crops typically grown in the Snake River valley, soybeans may be economically feasible only at high yields.

Soybean varieties developed for the midwestern and southern states are not necessarily well adapted to Oregon’s lower night temperatures, lower relative humidity, and other climatic differences. Previous research at Ontario has shown that, compared to the commercial cultivars bred for the Midwest, plants for eastern Oregon need to have high tolerance to seed shatter and lodging, reduced plant height, increased seed set, and higher harvest index (ratio of seed to the whole plant). There is also a need to identify semi-dwarf cultivars that will grow and yield well under high seeding rates and narrow row spacing. Yields also could be increased by increasing the seeding rate from 200,000 seeds/acre to 300,000 seeds/acre if semi-dwarf lines were found adapted to local conditions.

Majid and Jolliff at OSU Corvallis identified a soybean line that would fill pods when subjected to cool night temperatures. Those lines were crossed at Corvallis with productive lines to produce OR-6 and OR-8, among others. At this point, the development moved to Ontario, OR. The later two lines were crossed at our request for several years with early-maturing, high-yielding, semi-dwarf lines by R.L. Cooper to produce semi-dwarf lines with potential adaptation to the Pacific Northwest. Selection criteria at the Malheur Experiment Station included high yield, no lodging, no shatter, low plant height, and maturity within the available growing season. In 1992, 241 single plants were selected from five F5 lines that were originally bred and selected for adaptation to eastern Oregon. Seed from these selections was planted and evaluated in 1993. A total of 18 selections were found promising and were tested further in larger plots in 1994 and 1995. From 1995 to 1998, varieties were tested using a planting rate of 300,000 seeds/acre. This report summarizes work done in 1999 as part of the continuing breeding and selection program to adapt soybeans to eastern Oregon. Some of the more promising experimental lines and some commercial lines also were tested at the Central Oregon Agricultural Research Center in Madras, Oregon in 1999.

The 1999 line evaluation trial was conducted on a Owyhee silt loam previously planted to wheat. The herbicide Dual at 1 lb ai/acre was broadcast preplant and incorporated with a bed harrow on May 9. Seed was planted on May 18 at 200,000 seeds/acre in rows 22 inches apart. Rhizobium japonicum soil-implant inoculant was applied in the seed furrow at planting. Emergence began on May 25. The crop was furrow irrigated as necessary. Eleven of the single plant selections from 1992, nine cultivars, and OR-6 and OR-8 were planted in replicated plots four rows wide by 25 feet long in 1999. The experimental design was a randomized complete block with four replicates. All plots were cut to 22 feet.

Plant height and reproductive stage were measured weekly for each cultivar. Stand counts were made in 3 feet of row in 1996, 1997, and 1999. Prior to harvest, each plot was evaluated for lodging and seed shatter. Lodging was rated as the degree to which the plants were leaning over (0= vertical, 10= prostrate). The middle two rows in each four-row plot were harvested on October 12 using a Wintersteiger Nurserymaster small plot combine. Beans were cleaned, weighed, and oven dried to determine moisture content. Dry bean yields were corrected to 13 percent moisture. Data were analyzed by analysis of variance. Means separation was determined by the protected least significant difference test. Procedures for the Madras planting were similar except the row spacing was 24 inches and lodging was rated by a different method. Soybean was planted at Madras on May 20. A killing frost occurred on September 27.

Yields for 1999 at Ontario ranged from 27 to 54 bu/acre (Table 1). All of the 1992 single plant selections had yields greater than 40 bu/acre. All of the 1992 single plant selections had less than a 1 rating for lodging (on a scale of 0 to 10), and Minnato, Lambert, Sibley, and Vinton had a lodging rating of 3 and above. All of the 1992 single plant selections reached physiological maturity in 101 days or less. Of the 1992 single plant selections, M92-225, M92-217, M92-330, and M92-350 had seed counts sufficient for the manufacturing of tofu (< 2,270 seeds/lb) in 1999 (Table 2). The cultivars M92-217, M92-330, OR-8, Evans, and Sibley had seed counts of less than 2,270 seeds per lb every year that seed counts were made. Several lines combine early maturity, comparatively high yields, no shatter, and no lodging (Table 3). The lines M92-225 and M92-237 have light hilum color and made reasonable tofu in food quality tests in 1999.

Yields of all lines dropped starting in 1995, when the planting rate was increased from 200,000 to 300,000 seeds/acre (Table 4). The drop in yield may be due to the increase in seeding rate. A higher seeding rate could lead to a plant height increase and more lodging. In 1999, the seeding rate was reduced to 200,000 seeds per acre. However, plant populations in 1996 and 1997 were not different from 1999 (Table 5). Plant populations were below the target of 300,000 plants per acre in 1996 and 1997 and 200,000 plants per acre in 1999.

In Madras in central Oregon, all the experimental lines except M92-220 matured in time for a harvestable yield (Table 6). Of the commercial cultivars, only Agassiz and Glacier matured before a killing frost. On average yields were lower and seed sizes were smaller at Madras compared to Ontario.

Table 2. Seed counts for soybean cultivars for 4 years, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

Table 5. Plant population for soybean cultivars for 3 years, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.