Toxicity of Decomposing Crop Residues to Cotton Germination and Seedling Growth1

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Abstract
Toxicity of un‐ionized ammonia was the primary reason for inhibited germination and reduced growth of cotton seedlings following incorporation of plant residues in a sandy loam soil. The accumulation of ammonia in toxic amounts resulted from increased soil pH and ammonium N content, whicn were proportional to the organic N content of the residues. Plant growth decreased sharply with increasing ammonia and levels above about 10 ppm were lethal.Under sterile conditions, 1:50 plant‐water extracts did not reduce germination, but with the onset of microbial decomposition, extracts of all materials were highly toxic. At concentrations above 1 :50, alfalfa extracts reduced radicle elongation even under sterile conditions, indicating the presence of a toxic constituent, possibly saponin.