THE INFLUENCE OF THE pH OF A CULTURE SOLUTION ON THE RATES OF ABSORPTION OF AMMONIUM AND NITRATE NITROGEN BY THE TOMATO PLANT

Abstract

The rates of absorption of NH4-N and of NO3-N by tomato cultured in nutrient solutions were shown to be affected by (a) pH of media, (b) age of plants, (c) prior cultural exposure. Progressively greater quantities of NH4-N were absorbed with increasing pH values 4.0, 5.0, 6.0, 7.0, but in case of NO3-N, rates decreased progressively with above increasing series, save in the case of pH 4.0 where rate was less than at pH 5.0. Comparison of the maximum rates of absorption of the two forms of nitrogen at various pH values and at different ages of plant showed NH4-N intake greater than that of NO3-N in young plants. In older plants, rate of absorption of NO3-N was greater than that of NH4-N for corresponding pH values. Transference of plants from a high to a low pH or vice versa retarded absorption of nitrate, but in case of ammonium results obtained conformed to effect of pH as above noted.