Submitted to: Society of Nematology Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2006
Publication Date: July 31, 2006
Citation: Zasada, I.A. 2006. Understanding how soil properties affect the ability of organic amendments to suppress plant-parasitic nematodes [abstract]. Journal of Nematology. 38:303. Technical Abstract: The influence of soil properties on the efficacy of nematicides has always been an important consideration in their use. The role which soil chemical and physical conditions determine the fate, availability and exposure levels to nematodes of compounds derived from organic amendments deserves equal consideration. Hydroxamic acids are the chemically active component of rye cover crops implicated in nematode suppression. They are formed in soil after incorporation of plant material and the enzymatic degradation of parent compounds. The partitioning coefficients of these compounds in three soil types were determined. Availability and exposure times in soil varied with soil type. Similarly, the influence of soil conditions upon the nitrogen cycle is an important consideration when utilizing nitrogenous amendments for nematode management. Ammonia is present at high soil pH, whereas low soil pH encourages the formation of nitrous acid. Both compounds are lethal to nematodes. Meloidogyne incognita was exposed to a biomineral soil amendment with or without urea supplementation under varying conditions of temperature. Significant formation of ammonia and nematotoxicity were achieved only when high soil pH was present. Incubation temperature also had a strong influence on ammonia accumulation with the amendment being more effective in producing ammonia and killing the nematode at higher temperatures. The formation of nitrous acid in a diverse set of soil types was evaluated; sand and low organic matter content soils were the best candidates from promoting nitrous acid availability. The use of organic amendments for nematode management is a complex process requiring an understanding of the transformation and generation of active compounds and how soil conditions regulate exposure levels of the compounds. Consistent and reliable nematode suppression with organic amendments will be achieved only through an understanding of these complex processes.