Agricultural Practices for Growing Kenaf in Iowa: I. Morphology, Stem, and Fiber Yield

Abstract

Core Ideas Two kenaf cultivars were compared for stem fiber yield under combinations of planting rate, row spacing, and N fertilization rate. Tainung 2 produced greater stem fiber yield than Whitten. Nitrogen fertilization rate did not influence stem fiber yield. Stand density, core/bast fiber ratio, and basal stem diameter were influenced by three‐way interactions. ABSTRACT Kenaf (Hibiscus cannabinus L.) is a promising biorenewable resource for producing natural fibers but few studies have investigated the crop when grown in cooler climates, such as the American Midwest. The objectives of this study were to: (i) determine the agricultural practices (row spacing, seed, and N rates) leading to optimal kenaf dry matter (DM) stem and fiber yield in cultivars Tainung 2 and Whitten; (ii) evaluate stem height, basal diameter, and leaf area index (LAI) over the growing season; and (iii) assess the influence of management practices on fiber (bast and core lignocellulose) composition, and–2C, N, and total ash concentration. Kenaf cultivars Tainung 2 and Whitten were planted in Boone County, Iowa,–2in 2014 and 2015 at 247,000 or 371,000 seed ha−1, in 38‐cm or 76‐cm rows that received 0, 56, 112, 168, or 224 kg N ha−1. Stand density, core:bast fiber ratio, and basal stem diameter were influenced by three‐way interactions. Stem height at harvest was influenced by the main effects of row spacing, seeding rate, and N fertilization rate. Nitrogen fertilization did not influence stem DM yield, regardless of application rate. Kenaf is a promising multi‐purpose crop that could contribute to the natural fiber marker, as well as diversifying the landscape. Kenaf is well adapted to Iowa and can be produced with a range of management practices.

Agricultural practices for growing kenaf in Iowa: II. Fiber composition and quality

“…Previously, we reported that genotype and management practices interacted to affect kenaf stem and fiber productivity, morphology, and composition (Bourguignon et al., 2019). An important result previously reported was that N fertilization did not increase stem DM yield, regardless of how much N was applied (Bourguignon et al., 2019).…”

“…Previously, we reported that genotype and management practices interacted to affect kenaf stem and fiber productivity, morphology, and composition (Bourguignon et al., 2019). An important result previously reported was that N fertilization did not increase stem DM yield, regardless of how much N was applied (Bourguignon et al., 2019). However, it was noted that increased N fertilization rate did contribute to greater stem height and diameter during the growing season, as well as plant density at harvest, but N fertilization did not increase overall stem fiber yield.…”

“…Weather conditions were reported previously in Bourguignon et al. (2019). Briefly, most months each year were within the expected range of the 30‐year long‐term mean for temperature (Figure 1).…”

“…The study was conducted at the Iowa State University Agronomy and Agricultural Engineering Research Farm, near Boone, IA (42°01′N, 93°46′W), on a Nicollet clay loam soil (fine‐loamy, mixed, mesic Aquic Hapludoll). Detailed information on the experimental design, agronomic treatments, and field operations were provided by Bourguignon, Moore, Lenssen, and Baldwin (2019). The local air temperature and monthly cumulative precipitation were collected by a weather station (station A130209) located at the Agricultural Research Farm (ISU Ag Climate, 2014), approximately 3 km from the research site.…”

“…Two 3‐meter rows were harvested by hand in each plot on 12 November 2014 and 24 November 2015, respectively, as described in depth by Bourguignon et al. (2019). Stalk number and wet weight were determined in the field on these two rows during each harvest.…”