Chloride ION As Nitrification Inhibitor.

Due continued use of potassium chloride as potassium source in most crops, has been increasing accumulate of chlorine in soil and plants, especially in fertilization of perennial crops and those whose crop residues return to the soil annually. The availability of excess chloride ion triggers a number of physiological disorders in plants and microorganisms. This study aimed to evaluate the potential inhibition of chloride ion as ammonium chloride and potassium chloride in the reaction of nitrification in soil. The experiment was conducted under laboratory conditions, using sample of the surface soil of a Typic Hapludox cultivated with sugarcane. The experimental design was completely randomized with four replications and the treatments was ammonium sulfate or ammonium chloride at a dose of 100 mg kg^-1 N with potassium chloride at a dose of 100 or 200 mg kg^-1 Cl^-. We evaluated also the effect of ammonium chloride doses (130, 260 and 520 mg kg^-1 Cl^-), plus control treatment. The soil was pre-incubated for 20 days in dark condition, mean temperature of 26°C. After the pre-incubation soil moisture was adjusted to 70% of water hold capacity, the treatments were applied. Then, the samples were incubated for a period of 21 days in BOD chamber. The addition of ammonium chloride combined with potassium chloride resulted in reduction of nitrate-N concentration. The increase of chlorine concentrations in soil by providing of N-ammonium chloride doses resulted in inhibition of nitrification in soil. The increased concentration of ammonium was directly proportional to the increase in osmotic pressure. The combination of ammonium chloride with potassium chloride caused a reduction in the concentration of microbial biomass carbon, after 24 hours of application. The soil pH showed an inverse relationship with increasing concentrations of ammonium. The chloride ion was found to be a potential inhibitor of ammonium oxidation in soil.