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United States Department of Agriculture

Agricultural Research Service


item Webber, Charles - Chuck
item Roberts, B.w.
item Shrefler, J.w.
item Duthie, J.

Submitted to: Hortscience Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Adverse soil temperatures can decrease seed vigor and germination, resulting in decrease crop stands. Maximizing crop stand establishment and minimizing weed competition is essential to optimize yields. A greater understanding of the effects of temperature on crop and weed germination will enhance the development of integrated crop production and weed control lsystems that will assist in the selection of the best cultivars and herbicides for the appropriate cultural situations. The crop and weed seed responses to temperature will continue to have an increasing influence on the herbicide formulation process as new temperature controlled released herbicides are developed. Research was conducted to determine the response of six cucurbit cultivars and two pigweed species when exposed to sixteen temperatures ranging from 51 to 109F. Although the early percent germination for the watermelon cultivars was greater at one temperature range, the final optimal germination temperatures were actually lower than was first indicated. The research also showed a germination advantage for Allsweet (a diploid cultivar) through the middle to higher temperatures, and increased germination for Crimson Trio (a triploid, seedless cultivar) at two of the lower temperatures. The watermelon cultivars also germinated slower than that the other cucurbits and the pigweeds. The cantaloupe cultivars were the only cucurbits with any germination at the highest temperature, 109F. The cucumber cultivars produced the fastest and greatest seed germination, generally producing near optimum germination within 3 to 5 days. The two pigweed species exhibited the greatest variation in response to temperatures of all the seeds tested. The research demonstrated that even cultivars within a specific cucurbit crop respond

Technical Abstract: The temperature at germination can influence both the rate of germination and the final percent germination, both are important determinates of stand establishment for crops and weeds. If germination temperatures have a detrimental influence on seed vigor, the seedlings may become more susceptible to diseases and insects. Herbicides with narrow crop toxicity tolerances can also adversely affect seedlings that have decreased vigor. Therefore, a crop's response to temperature at germination is an important production consideration when selecting the cultivar, the planting date, and the pest control strategy. The objective of this research was to determine the germination response of selected cucurbits and pigweed species to temperature. Seed germination packets for six cucurbit cultivars and two pigweed species were placed in a water-bath with sixteen germination chambers. The germination chambers ranged from 51F to 109F, with an average temperature difference of 3.9F. The seeds evaluated included watermelon cultivars, (Crimson Trio and Allsweet), cantaloupe cultivars (Magnum .45 and Hales Best Jumbo), cucumber cultivars (Calypso and Dasher II), and weed species, spiny pigweed (Amaranthus spinosus), and tumble pigweed (Amaranthus albus L.). Seed germination was measured daily for the thirty-day experiment. The watermelon cultivars achieved 50% germination after 2 days, Crimson Trio at 91F and 98F, and Allsweet at 98F. Although the watermelon reached 50% germination first at these higher temperatures, maximum germination after 3 days was produced in the 82 to 91F range. The cantaloupe cultivars achieved 50% germination in 2 to 4 days at temperatures from 75 to 105F. Optimum germination temperature for

Last Modified: 05/21/2017
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