Amaranth Seedling Emergence as Affected by Seeding Depth and Temperature on a Thermogradient Plate¹

Abstract

Seedling emergence studies are normally conducted in growth chambers, greenhouses, or field plots and require much space, equipment, and time when several factors are considered. Amaranth (Amaranthus spp.) is a new crop in the United States that often exhibits inadequate field emergence because of environmental constraints. Two seedlots, one white seeded and one black seeded, from the same population of Amaranthus hypochondriacus L. were assessed for emergence index and percentage emergence in a peat‐sand medium over a range of temperatures and seeding depths using a modified thermogradient plate. Seed color produced no difference in emergence, but significant differences in emergence were caused by temperature, seeding depth, and temperature × depth interaction. A predictive response surface shows expected amaranth seedling emergence index at temperatures between 15 and 42°C and seeding depths between 13 and 51 mm. Highest amaranth emergence index and percentage emergence on the thermogradient plate occurred from the 13‐mm seeding depth and at temperatures between 24 and 34°C; these data suggest field emergence may be satisfactory with soil temperatures between 18.5 and 24°C.

The biology of Canadian weeds. 130. Amaranthus retroflexus L., A. powellii S. Watson and A. hybridus L.

“…The highest emergence percentages of A. retroflexus under field conditions in southern Ontario were observed approximately 10 d after rainfalls of 10 mm or more (Moore et al 1994). Most seedlings of the three Amaranthus species emerge from the top 2.5 cm of soil (Weaver and McWilliams 1980;Webb et al 1987;Oryokot et al 1997a). Weaver et al (1988) found that emergence of A. powellii under controlled environment conditions was greater from a depth of 1.5 cm than on the soil surface at 15/10°C or 20/15°C, but the reverse was true at 35/30°C.…”

“…In non-dormant seeds, the minimum temperature required for germination is normally between 8-12ºC; optimum temperatures are between 25-40ºC, and maximum values reach Weaver and Thomas 1986;Wiese and Binning 1987;Webb et al 1987;Matsuo and Kubota 1993;Ghorbani et al 1999). Weaver (1984) and Weaver and Thomas (1986) found that, in general, alternating temperatures at 35/20ºC and a 14h photoperiod gave better germination percentages in A. retroflexus, A. powellii and A. hybridus than alternating temperatures at 24/12ºC and continuous darkness.…”

Optimal planting date, row width, and critical weed-free period for grain amaranth and quinoa grown in Ontario, Canada

“…Their study concluded that when grown at 20°C and exposed to a 12 h photoperiod, grain amaranth could mature in less than 70 d. In Slovenia, Bavec and Mlaker (2002) had highest yields when grain amaranth was sown in May at soil temperatures of >12°C, and a photoperiod of at least 14 hours. On average, soil temperatures at seeding should be at least 15°C to ensure consistent seed germination and seedling emergence (Webb et al 1987;Aufhammer et al 1998). In the U.S., grain amaranth was precision seeded at 300 000 plants ha…”

The performance of Amaranthus cruentus and Celosia argentea as affected by varying sowing depths

“…They showed that the delay in emergence due to heat stress tended to be greater with increasing depth of sowing. Webb et al (1987) on the other hand reported that sowing Amaranthus deeper than 13cm delayed and decreased emergence and that soil crusting or lack of moisture could adversely affect seedling emergence with increased sowing depth.…”

“…This limitation often restricts the depth from which an amaranth seedling could emerge. Webb, et al, (1987) reported that seeding as deep as 2.5cm should be practical in friable soils if seeding rates are adjusted to compensate for reduced percent emergence associated with depth of sowing. Mayer and Polkajoff-Mayber (1975) also reported that emergence could be influenced by soil type since soil, strength has an important type of effect on the ability of roots to penetrate into the soil especially through clods or firmly structured layers.…”