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Title: Salinity and Alkaline pH of Irrigation Water Affect Marigold Plants: I. Growth and Shoot Dry Weight Partitioning

item Grieve, Catherine
item Poss, James

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2009
Publication Date: 10/1/2009
Citation: Valdez-Aguilar, L.A., Grieve, C.M., Poss, J.A. 2009. Salinity and Alkaline pH of Irrigation Water Affect Marigold Plants: I. Growth and Shoot Dry Weight Partitioning. HortScience. 44(6):1719-1725.

Interpretive Summary: Competition among agricultural and urban users for high-quality water supplies has increased as the population increases. One environmentally-sound approach for conserving these dwindling water resources is the capture and reuse of degraded, often saline, wastewaters for crop production. Growers of high value cut flower crops have traditionally used high-quality waters in order to avoid jeopardizing quality and yield of the marketable product. However, little quantitative information is available in the literature that would guide growers in the selection of cut flower species which could be produced with recycled, saline waters. This report describes the response of three marigold cultivars to saline irrigation waters: Cultivar ‘French Vanilla’ (Tagetes patula) is a short-statured bedding plant, cultivars ‘Flagstaff’ and ‘Yellow Climax’ (T. erecta) produce tall flowering stems, highly valued in the florists’ market and also useful in landscape settings. Plants were grown in greenhouse sand tanks. Ten irrigation water treatments were imposed: five salinity levels with electrical conductivities (EC) = 2, 4, 6, 8 and 10 dS/m and two pH levels 6.4 and 7.8. Quality of the flowering stems was evaluated on length and diameter of the main plant axis, number of flowers, diameter of the terminal flower, and vase life. Plant injury due to salinity was slight and observed only on older leaves. ‘Yellow Climax’ was the most salt tolerant of the cultivars tested, producing acceptable cut flowers even at moderately high (8 dS/m) salinity levels. Salinity effects on the quality components of ‘Flagstaff’ and ‘French Vanilla’ were reduced to such a degree that these cultivars can be recommended for saline landscape sites, but not for commercial production using saline recycled waters.

Technical Abstract: Marigold, is one of the most popular annual ornamental plants. Both the short-statured cultivars (Tagetes patula L.) and the taller cultivars (T. erecta L.) are used as container plants, in landscape and garden settings. Tagetes erecta varieties make excellent cut and dried flowers for the florists’ market. This study was conducted to evaluate the response of the T. patula ‘French Vanilla’ and two T. erecta ‘Flagstaff’ and ‘Yellow Climax’ to irrigation with saline water with and without pH control. Marigold plugs were transplanted in greenhouse sand tanks and established for one week under nonsaline conditions. Ten treatments were then applied with electrical conductivities (EC) of 2, 4, 6, 8 and 10 dS · m-1 and pH levels of 6.4 and 7.8. Growth of all three cultivars decreased in response to irrigation with saline waters at pH 6.4, and the effect was even greater at higher pH. Compared to the non-saline controls, ‘French Vanilla’, exhibited a 20 to 25% decrease in plant height, leaf dry mass (DM), and total shoot DM when irrigated with 4 dS • m-1 water. However, the number of flowering shoots per plant, and the diameter and number of flowers from the lateral shoots were not significantly affected until the EC of the irrigation water exceeded 8 dS • m-1. Growth of ‘Flagstaff’ and ‘Yellow Climax’ also decreased as salinity increased. Total shoot DM of the tall cultivars decreased by 30% and 24%, respectively, in response to the 4 dS • m-1 treatment, but additional salt stress had no further effect on DM production. Salinity tended to shorten internode length, creating more compact shoots, however, all marigold cultivars were rated as moderately sensitive to salinity. These attractive, compact plants show great promise as bedding or landscape plants in salt-affected sites provided that the pH of the soil solutions remains relatively acidic.