Effect of alkalinity in irrigation water on selected greenhouse crops /
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| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2005]
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Abstract: | Bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) are the most important ions that determine alkalinity. When the carbonates accumulate in a growing medium, the growing medium solution pH reaches levels that cause plant growth inhibition, which is caused primarily by the transformation of soluble forms of Fe into insoluble forms.The general objective of this research was to provide information about the limits of tolerance to alkalinity in ornamental plants, and to study the interaction of ions such as ammonium (NH₄⁺) and nitrate (NO₃⁻) on the response of plants to alkalinity, as well as the effect of the counter-ions potassium (K⁺), sodium (Na⁺), cesium (Cs⁺), ammonium (NH₄⁺) and rubidium (Rb⁺). The maximum SPAD index was estimated to occur at 0 mM of NaHCO₃ in chrysanthemum, mini-rose, and hibiscus 'Bimini Breeze' and 'Mango Breeze'. For vinca it was set at 2.64 mM. A 15% decrease from the maximum SPAD index was considered the threshold to declare the toxic concentration of NaHCO₃, which was calculated based on the maximum SPAD index predicted by the models. The toxic concentration of NaHCO₃ was set at 4.1, 1.1, 6.7, 3.1, and 6.3 mM of NaHCO₃ in chrysanthemum, mini-rose, vinca, and hibiscus 'Mango Breeze' and 'Bimini Breeze', respectively. Hibiscus 'Bimini Breeze' was considered tolerant to alkalinity, due to increased Fe-reduction capacity and acidification of the growing medium. In the hydroponic experiment, results showed that the NH₄⁺:NO₃⁻ ratio altered the response of sunflower plants to alkalinity. Sunflower plants grew better in solutions containing 5 mM NaHCO₃ prepared with a 0.25:0.75 NH₄⁺:NO₃⁻ ratio. This was possible due to the reaction of NH₄⁺ with the HCO₃⁻, which reduced its buffering capacity. The response to HCO₃⁻-induced alkalinity was modified by the counter-cation of HCO₃⁻. In bean plants, at low-to-intermediate levels of Na⁺ and HCO₃⁻ induced approximately same growth decrease. At high concentration, Na⁺ induced a decrease on shoot growth that exceeded the toxic effects of HCO3-. Thus, the toxic effect of Na⁺ is higher than that of HCO₃⁻ when its concentration is high. Rubidium was extremely toxic at concentrations of 7.5 mM. |
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| Item Description: | "Major Subject: Horticulture" Title from author supplied metadata (automated record created on Nov. , 09:45:50.) Vita. Abstract. Electronic resource. |
| Format: | Mode of access: World Wide Web. System requirements: World Wide Web access and Adobe Acrobat Reader. |
| Bibliography: | Includes bibliographical references. |