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Comparative Toxicity of Nitrapyrin and 6‐Chloropicolinic Acid to Radish and Cucumber under Different N Nutrition Regimes 1
Author(s) -
Sander Diane J.,
Barker A. V.
Publication year - 1978
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1978.00021962007000020019x
Subject(s) - phytotoxicity , ammonium , shoot , chemistry , raphanus , agronomy , toxicity , nitrification , horticulture , nitrogen , biology , organic chemistry
Nitrapyrin, 2‐chloro‐6‐(trichloromethyl)pyridine, is a nitrification inhibitor used to maintain fertilizer N in the ammonium form in order to reduce leaching and denitrification losses of N from soil. Nitrapyrin and its metabolite, 6‐chloropicolinic acid, are phytotoxic, and ammonium injury to plants is frequently greater when nitrapyrin is added to the soil. The objectives of this study were to investigate the phytotoxicity of nitrapyrin and 6‐ chloropicolinic acid under different N nutrition regimes (15 meq/liter of NO 3 ‐N. NH 4 ‐N, or NH 4 ‐N with pH buffering to 7 with CaCO 3 ) and to see if either compound affected the phytotoxicity of ammonium ions. Radish ( Raphanus sativus L. ‘Cherry Belle’), and cucumber ( Cumumis sativus L. ‘SMR‐18’), were grown in sand culture in a greenhouse. Plant nutrients and the inhibitors (10 ppm) were supplied in solution, and CaCO 3 was mixed with the sand. Radishes were uninjured by nitrapyrin or 6‐chloropicolinic acid. Ammonium‐N (15 meq NH 4 ‐N/liter) nutrition produced toxicity symptoms in radish and decreased root yields. Buffering of pH partially corrected the ammonium toxicity to roots and fully corrected it for shoots. Nitrapyrin and 6‐chloropicolinic acid restricted cucumber growth. Visible symptoms of nitrapyrin toxicity appeared as constricted zones on the stem base and as white areas on petioles of first true leaves. Toxicity of 6‐chloropicolinic acid appeared as curling on younger leaves and marginal burn on older ones. Cucumber growth was restricted by ammonium‐N nutrition. Buffering of pH corrected the toxicity of ammonium‐N and picolinic acid but not that of nitrapyrin.