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Title: Salinity and Alkaline pH in Irrigation Water Affect Marigold Plants: II. Mineral Ion Relations

Author
item VALDEZ-AGUILAR, LUIS - University Of California
item Grieve, Catherine
item Poss, James
item Layfield, Donald

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., Layfield, D.A. 2009. Salinity and Alkaline pH in Irrigation Water Affect Marigold Plants: II. Mineral Ion Relations. HortScience. 44(6):1726-1735.

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. This report is a companion paper to one describing the response in terms of yield and quality of three marigold cultivars grown in greenhouse sand cultures to irrigation with recycled 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 are also useful in landscape settings. 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. Ionic content of leaves and stems was determined. Aesthetic quality of the flowering stems remained high regardless of treatment. The primary reason for this observation was due to a mechanism that prevents the toxic ion, sodium, from being transported to the leaves where the ion would undoubtedly cause tissue injury and death. Uptake of essential micronutrients, such as copper and zinc, was slightly reduced at the higher pH level, but the concentrations in the leaves and stems were adequate to meet the plants nutrient requirements.

Technical Abstract: Scarcity of water of good quality for landscape irrigation is of outmost importance in arid and semiarid regions due to the competition with urban population. This is forcing the use of degraded waters with high levels of salinity and high pH, which may affect plant establishment and growth. The objective of the present study was to determine the effect of irrigation with saline water with and without pH control on the mineral ion relations of three marigold cultivars: ‘Flagstaff’, ‘Yellow Climax’, and ‘French Vanilla’. Treatments were five salinity levels with electrical conductivities (EC) = 2, 4, 6, 8, and 10 dS/m, and two pH levels: 6.4 and 7.8. Plants of ‘French Vanilla’ and flowering stems of ‘Flagstaff’ and ‘Yellow Climax’ were harvested at flower maturity. Leaves of the taller cultivars, ‘Flagstaff’ and ‘Yellow Climax’ were collected separately from the main axis and from the lateral stems while in ‘French Vanilla’ leaves were composited. Concentrations of macro-nutrient, micronutrients, sodium and chloride in leaf and stem tissues were determined. The three marigold cultivars were strong calcium accumulators and this response was more evident at the lower pH level. Leaf-magnesium increased as salinity increased. Leaves on the lateral branches were stronger potassium-accumulators than those on the main stem. Potassium concentrations in leaves of marigold irrigated with waters at pH 6.4 tended to decrease as salinity increased. Marigold seems to possess an efficient sodium-exclusion mechanism which restricts sodium accumulation in the leaves. Patterns of total-phosphorus accumulation in leaf tissues were not consistent over the range of salinity treatments. Among the micronutrients, iron and manganese tended to be partitioned to the younger, rather than the older leaves, whereas the reverse was true for copper and zinc. Despite the reduction in growth, the aesthetic value of the cultivars was not detrimentally affected by application of saline waters with EC’s as high as 8 dS/m.