Data of the biomass production and forage quality (nutritive value) of 13 different tepary bean genotypes managed at four different cutting heights and three different cutting dates. The data was collected during 2020 and 2021 to compare cutting management of tepary bean with forage soybean.
The study occurred at the Oklahoma and Central Plains Agricultural Research Center, El Reno, OK (35◦ 34’ N; 98◦ 2’ W, 414 m a.s.l.). Total rainfall was 340 mm in 2019 and 271 mm in 2020. No supplemental irrigation was applied. Weedy grasses were controlled with Clethodim 2EC throughout the growing season at a rate of 231.5 g a.i. ha-1).
The study began June 10th 2020 and lasted 90 days. The study was replicated June 10th 2021 and lasted 90 days.
Biomass was harvested from 0.5 m row lengths at 30-, 45-, or 90-day (end of season) intervals and at heights of 5, 10, or 15 cm above ground level to determine biomass production and regrowth ability. The 90-day interval was cut at 5 cm only and served as a control.
Subsampling occurred 3 times for the 30 day, 2 times for the 45 day, and once for the 90 day. The 3–30-day samplings were summed to compare to the 90-day cutting. Likewise, the 2–45-day samplings were summed to compare to the 90-day cutting.
Fresh weight of biomass was determined for clipped biomass, samples were dried at 60 ◦C for 72 hr, re-weighed to define dry matter, and subsequently ground to a 2.0 mm particle size for laboratory analysis using a Thomas Scientific Wiley Mill (Swedesboro, NJ, USA). The ground particles were thoroughly mixed and ~50g were scanned with a benchtop NIR (Unity Scientific Spectra Star XT with UCal calibration software, Westborough, MA, USA), and measures of forage quality [acid detergent fiber (ADF), in vitro True Digestibility (IVTD), neutral detergent fiber (NDF), total nitrogen content (N), total digestible nutrients (TDN), and a TDN:CP ratio] were evaluated. The benchtop NIR was validated with wet chemistry each year using approximately 10% of the samples. Occasionally, due to reduced plant growth, replications were combined to determine the forage quality of a genotype.
Collected biomass (gm-2) was converted to Mgha-1). Data were analyzed with the Proc GLIMMIX procedure in SAS Studio 3.8. Genotype, cutting management (cutting height and cutting interval), and their interactions were considered fixed effects while the intercept of the linear predictor was considered a random effect with year as the subject (level).
During the 90-day period from June to September, some genotypes of tepary bean provided greater amounts of biomass and forage quality than Laredo (forage soybean). The optimal management regime for tepary bean for forage was noted for one end of season (90-day) harvest as this was the best combination of biomass accumulation and forage nutritive value (forage quality).
Breeding efforts to improve the forage characteristics and agronomic performance of tepary bean are required. Studies to determine the optimal planting rate/density are needed to refine and expand the use of tepary bean as an alternative forage.