Tillage systems and seed dormancy effects on common waterhemp (Amaranthus tuberculatus) seedling emergence

Abstract

Understanding weed seedling emergence patterns is important for successful implementation of many weed management strategies. Identifying the sources of variation of emergence patterns could greatly improve our ability to predict emergence timing. Differences in seed dormancy levels between populations or biotypes are usually not considered when studying seedling emergence of many weed species despite evidence that dormancy levels can affect weed seedling emergence patterns. We studied the importance of seed dormancy on seedling emergence patterns of common waterhemp using three biotypes (Ames, Everly, and Ohio) that differed in dormancy regulation and level (5, 26, and 87% germination, respectively) and three tillage systems (no-tillage, chisel plow, and moldboard plow) in 2004 and 2005. Seedling emergence was at least four times greater under no-tillage than under chisel or moldboard plow conditions. Fewer seedlings emerged in moldboard plow than in other tillage systems. Furthermore, seedling emergence occurred in no-tillage over a longer period than in chisel and moldboard plow. In no-tillage the largest emergence events occurred at the end of June, whereas in other tillage systems most emergence occurred during May and the first week of June. Among biotypes, differences in number of emerged seedlings were more evident than differences in emergence timing. For Everly and Ohio biotypes, the number of emerged seedlings was the same between chisel and moldboard plow plots. For the Ames biotype, in 2004, the number of emerged seedlings was 25-fold higher in chisel plow than in moldboard plow, and the emergence pattern in no-tillage was longer and peaked later than in the other tillage systems. However, these results were not observed in 2005. Overall, we did not observe consistent differences in seedling emergence patterns among biotypes, which suggested that under field conditions, other factors can compensate for differences in seed dormancy levels.

Review: Microsite characteristics influencing weed seedling recruitment and implications for recruitment modeling

“…The varying response to temperature in biotypes exists in other weed species including waterhemp [Amaranthus tuberculatus (Moq.) Sauer] (Leon and Owen 2006) and redroot pigweed (Weaver and Thomas 1986).…”

Differentiation of Life-History Traits among Palmer Amaranth Populations (Amaranthus palmeri) and Its Relation to Cropping Systems and Glyphosate Sensitivity

“…For example, previous studies demonstrated that populations of tall waterhemp [Amaranthus tuberculatus (Moq.) Sauer], a dioecious weed species, have evolved different mechanisms to control seed dormancy and germination (Leon et al 2006a(Leon et al , 2006b, and these differences affected seedling emergence patterns depending on tillage system (Leon and Owen 2006). Furthermore, Bond and Oliver (2006) found differences in leaf traits among Palmer amaranth accessions collected throughout the southern United States and proposed that these might be ecotypes, but their research did not address the causes of those differences.…”

Weed Problems, Ecology, and Management Options in Conservation Agriculture: Issues and Perspectives

“…Thus, soil disturbance is minimized and crop residues remain on the top soil (Putte et al, 2010). Hence, it is not just an elimination of ploughing; it involves the development of a combination of agroecologically sound management practices (Han et al, 2013), changes in soil processes, lower soil temperature, and high soil moisture (Addae et al, 1991;Blevins and Frye, 1993;Leon and Owen, 2006), which could influence the ecosystem services, and the biodiversity too (Palm et al, 2014). Although, the environmental consequences of adopting CT (Holland, 2004) have been widely discussed, the slow pace of growth due to weed menace is a cause of concern.…”