Abstract
We investigated the effects of combining ammonium nitrogen (NH4+－N) and nitrate nitrogen (NO3－－N) in the ratios of 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100 on growth and root system development of alfalfa. Dry weight increased with ammonium nitrogen content in water culture. Length of lateral roots was greater in the ammonium 100% treatment, whereas no difference was observed among the ammonium 50%, 25%, and 0% treatments. Specific root length of the taproot showed similar values regardless of the mixture ratio of ammonium nitrogen or nitrate nitrogen. Specific root length of lateral roots showed variable results from no significant difference to significant difference with variable p-values between treatments depending on collection dates and no clear trend. Alfalfa absorbed more ammonium ions than nitric acid ions. These results showed that alfalfa attains superior growth and root system development in water culture with an increase in ammonium nitrogen content.
