The field study continued in 2021 at the NDSU Carrington Research Extension Center with support from Northarvest Bean Growers Association to examine the response of pinto bean to row spacing and plant population. Experimental design was a randomized
complete block with split plot arrangement (whole plot = row spacings; split plot = plant populations) with four replications. The dryland trial was established with durum wheat as the previous crop on conventionally tilled Heimdal-Emrick loam soil with 4.4% organic
matter, 6.6 buffer pH, 0.29 dS/m soluble salt (0-6-inch depth), 19 ppm P, 369 ppm K, and 1.52 ppm Zn. ‘ND Palomino’ pinto bean was planted on May 26 (soil at 58 degrees F; NDAWN) in 28- and 21-inch rows, and 7-inch paired rows (centered at 28 inches) with
planting rates of 60,000, 85,000 and 110,000 pure live seed (PLS)/acre (A) to establish targeted stands of 50,000, 70,000 and 90,000 plants/acre, respectively. NDAWN monthly - rain (inches): May = 1.4; June = 1.8; July = 0.1; August = 2.6; September = 2.0; October = 3.7; and 6-month total=11.6. The trial received supplemental flood irrigation at a targeted rate of 0.9 inch/A on each of the following dates and bean growth stages: July 22, V5-R1; July 29, V5-R1; and August 13, V5-R2. The supplemental irrigation plus late-season rain (Aug 20 to Oct 20 = 7.86 inches) stimulated new plant growth and extended time to reach plant maturity. A killing frost occurred on October 20 (low of 25 degrees F). Seed was direct harvested with a plot combine on November 1.
Averaged across planting rates, plant stand was reduced with 21-inch rows compared to the other row spacings (Table; LSD 0.05)). Plant emergence, first flower and maturity were similar among rows. Canopy closure was similar between 21-inch and paired rows,
and both greater than 28-inch rows. Seed yield was greater with 21-inch rows compared to other row spacings. Bean seed yield across the trial was poor, averaging 547 lb/A, due to dry soil and high temperatures during the first half of the growing season. White mold
was not observed in the trial.
Averaged across row spacings, early season plant population was 47,050, 63,260 and 72,710 plants/A with low, medium and high planting rates, respectively. Ratio of established plants compared to planting rates: 78%=low, 74%=medium and 66%=high. The reduced percentage of established plants compared to PLS rate was partially due to marginal topsoil moisture conditions following planting. Plant development was similar among plant stands. A slight advantage with canopy closure existed with the high vs. low plant densities. Seed yield was similar between the medium and high plant populations, and 105 to 142 lb/A (18-23%) greater than yield with the low population.
Test weight was the only agronomic factor with statistical significance with the interaction of row spacing and plant population: 21-inch rows at 85,000 and 110,000 PLS/A and 28-inch rows at 110,000 PLS/A provided the heaviest test weight (54.6-55.2 lb/bu).
