Date of Graduation

5-2022

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Nilda Roma-Burgos

Committee Member

Andy Mauromoustakos

Second Committee Member

Te-Ming Tseng

Third Committee Member

Trenton L. Roberts

Keywords

allelopathy, crop competitiveness, cultivar selection, integrated weed management, weed interference, weed suppression

Abstract

Sweetpotato (Ipomoea batatas L.) is a low-technology, subsistence crop that enhances food and nutrition security particularly in developing nations. Weed interference with the crop can reduce sweetpotato storage root yields and product quality. Current weed management practices in sweetpotato include PRE or POST herbicides application, cultivation, mowing, or handweeding. Unlike row crops, herbicide options for sweetpotato are few; therefore, alternative weed control practices are needed. The overall objective of this research was to determine the weed suppressive ability of several sweetpotato cultivars. This research also provides information about cover crop use for weed suppression in sweetpotato production in Arkansas. Field experiments were conducted in Fayetteville and Kibler to assess the weed suppressive ability with or without full-season interference of broadleaf spp., grass spp., or sedges spp.. Data collected included leaf area index (LAI), vine length, canopy height, weed biomass, and sweetpotato yield by grade. Four sweetpotato cultivars were selected from this study and integrated with winter cover crops in a second set of field experiments conducted in Kibler and Augusta, AR. A mixed combination of cereal rye (Secale cereale L.) + crimson clover (Trifolium incarnatum L.), and winter wheat (Triticum aestivum L.) + crimson clover was compared to a fallow ground control. Data collected were vine length, canopy height, weed biomass, cover crop biomass, and sweetpotato yield by grade. ‘Heartogold’, ‘Centennial’, and ‘Stokes Purple’ were found to have allelopathic activity in greenhouse setting. These results were confirmed in the field experiments. ‘Heartogold’ was strongly weed suppressive for both grass spp. and broadleaf spp., and yellow nutsedge (Cyperus esculentus L.). ‘Hatteras’ and ‘Centennial’ significantly reduced yellow nutsedge growth. These three cultivars have short vines and upright growth. Cultivars with long vines were generally less competitive with weeds. Canopy height and LAI were not correlated with weed suppression, indicating the contribution of another factor toward weed suppression. The most weed-suppressive cultivars were not always the highest yielding. ‘Beauregard-14’ and ‘Bayou Belle-6’ performed better in fields with broadleaf or grass weeds. ‘Bayou Belle-2’, ‘Bayou Belle-6’, ‘Hatteras’, and ‘Centennial’ yielded more in fields infested with yellow nutsedge. Vine length and LAI were positively correlated with jumbo, no.1, and total sweetpotato yield. A mix of cereal rye + clover is a suitable choice for a reduced-till, organic sweetpotato system. This cover crop mixture provided a higher weed suppression compared to that of winter wheat + crimson clover and resulted in numerically higher sweetpotato yields. Altogether, this research showed that there are commercially acceptable, weed-suppressive sweetpotato cultivars and these types of cultivars should be utilized to breed cultivars for commercial production. Weed-suppressive cultivars should be used as a tool for integrated weed management to reduce weed infestation levels, which leads to better performance of herbicides in conventional production and reduced handweeding cost in either conventional or organic sweetpotato production. Furthermore, planting weed-suppressive cultivars will complement the efficacy of cover crops in reducing early-season weed infestation, providing extended weed suppression after the activity of allelochemicals from the cover crop had dissipated and the sweetpotato has established.

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