Abstract
We examined effects of SO_4^<2-> and Cl^- concentration in fertilizers on NO_3^- concentrations in spinach (Spinacea oleracea L.) and ching guang juai (Brassica chinensis L.) in the isolation floor cultivation. By combining ammonium sulfate, ammonium chloride, urea or rapeseed meal as N fertilizer and potassium sulfate or potassium chloride as K fertilizer, various treatments were prepared in this experiment. Multiphosphate was uniformly applied as P fertilizer. They were applied as basal fertilizers at the rates of 15g of N per m^2, 6.5g of P per m^2, and 12.5 g of K per m^2. The main results obtained were as follows. 1) There were no differences in yield and nitrogen uptake of spinach and ching guang juai among the treatments. Nitrate concentration in plants decreased with the increase in the amount of Cl^- applied to the soil with highly negative correlation. In contrast, there was no relationship between NO_3^- concentration in plants and the amount of SO_4^<2-> applied to the soil. These findings indicate that application of chlorides to the soil lowers NO_3^- concentration in leaf vegetables without any effect on their growth. 2) As there was no significant difference in NO_3^- concentration in plants between ammonium sulfate and rapeseed meal applications, the effect of the form of fertilizers, inorganic or organic, was concluded to be minor to that of anions in fertilizer, SO_4^<2-> or Cl^-, on NO_3^- concentration in leaf vegetables.
