Abstract
Abstract
Carrots are a challenging crop to produce because the plants are slow to emerge and their early growth limits their tolerance to biotic and abiotic stresses, including those imposed by mechanical cultivation. In field studies conducted in Holt, Michigan, in 2021 and 2022, we evaluated the effects of carrot seed grading and using a sequence of in-row mechanical cultivation methods on carrot survival, weed mortality, and yield. We tested two key hypotheses: 1) carrots grown from large seed size fractions (LS carrots) would have greater root anchorage force and height than those grown from small seed size fractions (SS carrots) and hence greater tolerance to uprooting and burial imposed by finger weeders (FW) and hilling disks (HD); and 2) alternating in-row cultivation tools with these mechanisms of action (HD-FW) would reduce carrot mortality and improve weed management efficacy relative to continued use of a single tool (FW-FW). At the time of the first cultivation, LS carrots had greater anchorage force and height than SS carrots in both years, and greater tolerance to cultivation (lower mortality) in one of two years. The HD-FW cultivation sequence provided improved weed control efficacy and carrot yield than the FW-FW sequence in one of two years. However, when cultivation occurred early, the ability of the tools to kill weeds without killing or injuring crops was low regardless of seed size, and all treatments required supplemental hand weeding. When crops were cultivated later, no differences in carrot mortality based on seed size were detected. LS carrots exhibited a 17% to 23% increase in yield compared with SS carrots, regardless of the cultivation tool used. These results suggest that more intensive seed grading coupled with cultivation tools and settings that target weed burial can enhance profitability of carrot production.