Effects of planting date and variety on yield and quality of snap bean (Phaseolus vulgaris L.) in Oklahoma
Richmond, Jessica M.
Citations
Abstract
Although numerous studies have evaluated snap bean (Phaseolus vulgaris L.) pod yield from once-over harvest systems and pod quality at progressing maturities in a given harvest season, few have evaluated yield and pod quality in different seasons of production within the same year and fewer still have evaluated yield and quality from pods harvested at the same pod maturity successively from the same plants. The aim of this study was to determine if snap bean yield or pod quality (pod color and sugar accumulation) differed between plants harvested multiple times in spring and fall planting seasons in north central Oklahoma. Nine snap bean cultivars, including seven green podded and two yellow podded cultivars, were chosen for field production in spring and fall production seasons of 2022 and 2023. Sequential harvest of pods from the same plants and at the same relative stage of pod development occurred weekly for a three week period. Pod yield, pod tristimulus color, and pod sugar concentration were measured. Total pod yield pooled across seasons and years was lower for ‘Sybaris’ at about 4,100 kg ha⁻¹ than for six of the other cultivars whose yield ranged from 7,000 to 8,600 kg ha⁻¹. While pod yield typically increased from 900 to 1,300 kg ha-1 in the first weekly harvest to 3,500 to 3,700 kg ha⁻¹ by the last weekly harvest in the spring season, during the fall season it either decreased in 2022 from 1,900 kg ha⁻¹ in the first weekly harvest to 690 kg ha⁻¹ by the last weekly harvest or remained the same in fall of 2023 at 2,600 to 3,000 kg ha⁻¹ at each weekly harvest, with the decrease in yield in fall, 2022 likely due to sub-optimal low temperatures during pod development. Tristimulus pod color differentiated yellow-podded from green-podded cultivars and while some differences in hue and chroma were evident within snap bean pod color groups, each cultivar maintained its color properties at each harvest across seasons and years of the study. We observed a decrease in total pod sugar concentration from the first to the last harvest from 145.5 to 107.2 mg gm⁻¹, for glucose from 48.4 to 33.0 mg gm⁻¹ and for fructose from 90.7 to 52.0 mg gm⁻¹. We also observed an apparent increase in sucrose concentration from 9.2 to 21.9 mg gm⁻¹ from the first to last pod harvest. Decreasing total and monomeric sugar concentrations, coupled with increasing sucrose concentration, have been documented for overmature snap bean pods which were deemed less desirable due to lower perceived sweetness. In terms of sugar concentration, later harvested snap bean pods in a successive harvest system, even though they were harvested at the same relative stage of maturity as earlier harvested pods, resembled over-mature pods from a once-over harvesting system, perhaps indicating that snap bean plant age influenced pod sugar concentration in a similar manner to pod age.