| 摘要 |
An improver of rhizosphere microflora contains a urea-formaldehyde condensate of formula X-(NH-CO-NH-CH2)n-Y (I), where X = H or hydroxymethyl; Y = ureido or hydroxy, and n = 4 or more. (I) stimulates growth of particularly Pseudomonas, Agrobacterium and Bacillus species, but is not metabolised by many pathogens, e.g. Rhizoctonia, Fusarium and Streptomyces scabies. (I) is usually applied at 0.5-10 (preferably 2-6) g/l of soil, optionally with a fertiliser or other soil improver. (I) is made by reacting urea and formaldehyde under alkaline conditions (preferably pH 7-8) at 20-95 [deg]C for 0.5-30 hours with mole ratio 0.8-1.3. The product of this stage (mainly dimethylolurea) is then subjected to dehydration/condensation reaction at pH 3-5 and 60-80 [deg]C for 0.5-5 hours. The product from this stage has hot-water solubility not over 0.01 g/100 g and is degraded by microbes to ammonia and/or nitrate. The condensate is extracted with water at 80 [deg]C or more, for 0.5-3 hours, then dehydrated by centrifuging to give particles of diameter 0.5-5 mm. |
