Dry Edible Bean Performance as Influenced by Plant Density
B.G. Schatz, S.F. Zwinger, and G. J. Endres


he impact of plant density on dry edible bean (Phaseolus vulgaris L.) production is important to growers for varied reasons. Knowledge of impacts from different densities is important to traditional growers looking to optimize yield along with those who may produce dry beans using non-traditional planting and harvest equipment. Field trials at Carrington in 1999 and 2000 evaluated the influence of different plant densities on indeterminate upright (Type II) cultivars ‘Mayflower’ navy and ‘Shadow’ black dry bean. Dry bean were planted in 7- and 30-inch row spacings and at seeding rates of 90,000, 105,000 and 120,000 plants acre-1.

The 1999 and 2000 growing seasons were favorable for dry bean production. The plentiful precipitation received in July and August of each year was well distributed and coincided with the critical reproductive growth period of dry bean in the region. The two cultivars selected had a similar response to the row spacing and seeding rates evaluated in this study. 

Although the differences were not dramatic, solid seeding dry bean in 7-inch rows caused about a 2-day delay in flowering and physiological maturity compared to beans in 30-inch rows. In 2000, planting dry beans in wide rows resulted in a higher percent stand establishment compared to solid seeding. In both years, the height to the lowest pod was significantly greater at the narrow rows compared to wide rows. This could be an important management tool for producers considering direct harvest. Row spacing affected dry bean seed yield differently in the two years of this experiment. In 1999, planting in 7-inch rows increased yields significantly (240 lbs) compared to the 30-inch spacing. Yields at the two row spacings were similar in 2000.

The impacts of seeding rate on the factors recorded in this trial were minimal. During the 2000 season, days to maturity, plant height, and seed weight were influenced by changes in seeding rate. Lower seeding rates, and the resultant lower plant populations, caused a slight delay in plant maturity. Seeding rates evaluated in this study did not affect pod height. There is an expectation by producers that increased seeding rate will promote increased pod height and thereby improve ease of direct harvest. Seed weight decreased significantly as seeding rates increased from 90,000 to 120,000 plants acre-1. This response was evident in the 2000 study, while seed weights were similar in 1999. Higher seed weights often convey enhanced quality when marketing dry beans, which is important to growers.

Seed yield was not influenced by the seeding rate treatments used in this experiment. The magnitude of seeding rate difference (30,000 plants acre-1) used in this experiment was not great. The tendency by growers and consulting agronomists has been to recommend a moderate increase in the standard seeding rate of 90,000 plants acre-1 for dry beans planted in solid or narrow row spacing. Data from this experiment indicates that this seeding rate adjustment is not necessary to optimize seed yield. Dry beans have a high degree of plasticity that allows for adjustments among the plants’ yield components to changes in density.  The data indication that a seeding rate of 90,000 plants acre-1 is sufficient to optimize yield will allow growers to conserve input costs rather than spend funds for additional seed at planting.

Further research to investigate the impact of plant densities on dry bean performance may continue in the future at the Carrington Center. These investigations would include new cultivars that are being introduced into the industry. 1

NDSU Vice President,
Dean and Director for Agricultural Affairs
NDSU Extension Service ND Agricultural
Experiment Station
NDSU College of Agriculture NDSU College of Human Development and Education