A Study of the Growth Characteristics of Pepper (Capsicum annuum L.) Growing under Different Ammonium to Nitrate Ratios

Nitrogen forms exert significant effects on physiological and morphological characteristics of plant. In this study, the effects of ammonium, nitrate, and ammonium-nitrate on pepper plants were investigated in soil culture, as well as in solution culture. In the soil culture, 3, 4-dimethylpyrazole phosphate (DMPP) was used as a standard nitrification inhibitor to guarantee the presence of ammonium inside the soil. The results indicated that, in solution culture, when seedlings, at their early stages, were either treated with ammonium, or a portion of ammonium, plant growth parameters were severely decreased as compared with the nitrate grown plants. However, when seedlings were pretreated in nitrate for two weeks, the relative tolerance of plants to ammonium increased. Plants in soil culture had better tolerance to ammonium nutrition as compared with those grown in solution culture. This was probably due to the buffering action properties of the soil in which NH4+ is absorbed onto the soil colloids and slowly released over the time. This is further supported by better growth characteristics of plants grown in ammonium supplied soil as compared with ammonium-fed plants grown in hydroponics.