While using some form of cultivator to control weeds between the rows is a fairly common practice in sweet corn production, controlling weeds within the row by cultivating is a more risky maneuver. Ideally, the method and timing of in-row cultivation are such that weeds are controlled before they can compete with the crop. In-row tillage in the early stages of crop development also tends to cause less crop damage. Multiple passes of the cultivator may be required to deal with weed flushes, but each pass adds to costs and also increases cumulative damage to the crop.
LeBlanc and associates (HortTechnology 2006 16: p. 583-589) looked at crop damage and yields of sweet corn after a rotary hoe was used for in-row weed control at various intervals after seeding. A rotary hoe (Fig.1). (Yetter Inc.) set to cultivate to a depth of 2″ was used to cultivate within the crop rows from 1 to 4 times, beginning prior to crop emergence and running through until the crop reached the 6th leaf stage. They found that a single pass of the rotary hoe was safe in terms of crop damage and yields, irrespective of what stage the crop was at when the tillage event occurred. However, multiple passes with the rotary hoe resulted in increasing levels of crop damage that were reflected in reduced crop stand, delayed maturity and reduced yields. Unfortunately, the study did not address how the relative efficacy of weed control was influenced by the timing of cultivation and the number of passes used.
Source: LeBlanc et al. 2006. HortTechnology 16: 583-589