Effect of nitrogen form on the growth and nitrate concentration of lettuce |
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Authors: | A Scaife M E Saraiva Ferreira M K Turner |
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Institution: | (1) National Vegetable Research Station, CV35 9EF Wellesbourne, Warwick, UK;(2) Present address: Dep. Horticultura and Floricultura, Quinta du Marques, 2780 Oerias, Portugal |
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Abstract: | Summary A pot experiment with lettuce involving three N forms each at six application levels, showed that lettuce can be grown satisfactorily
with a very low nitrate content when supplied with ammonium sulphate and a nitrification inhibitor. For plants growing on
nitrate N, the optimum midrib sap nitrate concentration as maturity approached was about 1400 mg/1 NO3-N. Large losses of mineral N were observed from the peat medium, even in the absence of plants.
A relationship is presented which would enable a lettuce grower to estimate whole-shoot nitrate concentration from a quick
test of midrib sapi.e. NO3-N (mg/kg in fresh shoot) =0.14×NO3-N (mg/l in sap).
Tipburn was worst at intermediate levels of applied N, and was less serious with pure ammonium nutrition than with nitrate. |
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Keywords: | Ammonium Critical nitrate concentration Lettuce Midrib Nitrification inhibitor Nitrapyrin Sap test |
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