The Relationship of Chloride and Sulfate Ions to Form of Nitrogen in the Nutrition of Irish Potatoes1
- M. E. Harward,
- W. A. Jackson,
- J. R. Piland and
- D. D. Mason2
A greenhouse experiment using sand cultures was conducted to study the role of chloride and sulfate anions in the nutrition of Irish potatoes when different forms of nitrogen were used. The experiment consisted of two series, the first in which all N was supplied as NO3- and the second in which both NH4+ and NO3- were present. Treatments within each series consisted of plants receiving different amounts of sulfate and chloride. The initial solution concentrations of all ionic species except NH4+, NO3-, Cl-, and SO4= were the same for each treatment.
Two distinct foliar symptoms associated with treatments were observed. The first, a tip burn associated with high SO4= treatments, was more severe when NH4+ was present than when NO3- was the only source of N. The second, characterized by rolling of the leaves, was obtained only with Cl- treatments in the presence of NH4+. This was not observed when NH4+ was used in the absence of Cl- or when NO3- was added in the presence of either Cl- or SO4=.
Increasing Cl- and decreasing SO4= concentrations in the presence of NH4+ resulted in marked reduction in the yield of fibrous roots. Additions of Cl- generally resulted in decreases in the percentage of dry matter in the tops and this effect was more pronounced in the presence of NH4+. In the NH4NO3 series, reductions in chlorophyll content resulted from increased supply of Cl- and simultaneous decrease of equivalent amounts of SO4=. No change in these pigments was obtained in the NO3- series. The mineral content of the potato leaves was affected both by form of N and by Cl- and SO4= concentrations. The Cl- content of the leaves was markedly increased in the presence of NH4+.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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