| Abstrakt: |
Effect of 4‐amino‐3,5,6‐trichloropicolinic acid (picloram), 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (diuron), 2‐ethylamino‐4‐isopropylamino‐6‐methylthio‐s‐triazine (ametryne), and 2,4‐bis(isopropylamino)‐6‐methylthio‐s‐triazine (prometryne) at rates from 2 to 100 ppm on nitrification of 100 ppm applied NH4‐N was studied in several soils of Puerto Rico incubated at 24C for 8 weeks. The effect was greatly dependent on the nitrifying capacity of the soils. Inhibition of nitrification by herbicides was less in soils of high nitrifying capacity than in soils of low nitrifying capacity. Picloram at 2 ppm caused a weak inhibition and at 20 to 100 ppm complete inhibition except in the soil of high nitrifying capacity. Diuron inhibited nitrification at 20 ppm and above in soils of low to intermediate nitrifying capacity. It did not affect nitrification in the soil of high nitrifying capacity even at 100 ppm. Ametryne and prometryne at 100 ppm inhibited Nitrobacterbacteria, but not NH4‐oxidizers resulting in high NO2‐accumulation. At certain times 60 to 100% of the applied NH4‐H appeared as NO2‐when prometryne and ametryne were applied at 100 ppm, respectively. Nitrite accumulated, however, only at soil pH of 6.8 and above. |
