Temporal effects of nitrogen application rate on soil biomass production and nitrogen uptake efficiency of red pepper under elevated atmospheric CO₂and temperature

Abstract

To investigate temporal effects of nitrogen application rate on soil biomass production and nitrogen uptake efficiency of red pepper (Capsicum annuum L. cv. Manitta) under elevated atmospheric CO2 and temperature, the plant receiving nitrogen fertilizer in the rate of 180 and 360 kg N ha-1 was grown for 120 days after transplanting (DAT) in the pot within CO2- and temperature-controlled glass chamber. Each chamber consists of four units: ambient CO2 and temperature, elevated CO2 and ambient temperature, ambient CO2 and elevated temperature, elevated CO2 and temperature. Additional inputs were applied with the same amount at 60 DAT. All treatments were triplicate. Plant and soil samples were collected at 40, 80, 120 DAT. At 40 DAT dry mass was significantly increased by elevated CO2 and temperature for N2. For N1, the elevated temperature increased dry mass, while it was suppressed under elevated CO2. At 80 DAT, there was only significant CO2¡¿N interaction. At 120 DAT, elevated CO2 decreased significantly dry matter. At 40 DAT elevated CO2 increased total nitrogen contents significantly for N1 and N2 to 15%. However effect of elevated temperature was insignificant on total N. At 80 DAT, total nitrogen of plant was reduced by 13% regardless of temperature for N1, but for N2 total nitrogen increased. At 120 DAT, for ambient temperature, elevated CO2 significantly reduced total nitrogen by 30 and 20% at N1 and N2, while elevated CO2 and temperature reduced total nitrogen by 39 and 41% for N1 and N2. The trend of nitrogen derived from urea and nitrogen derived form soil influenced by CO2 and temperature was similar to that of total nitrogen. Elevated CO2 influenced similarly on the dry mass of stem and root. As the fertilization of nitrogen increased, dry mass due to elevated CO2 showed great increment. The response to elevated temperature was also similar. In contrast, the response of nitrogen in stem and root at each sampling was not similar. During the plant growth, although N contents of stem increased but after 80 DAT decreased regardless of CO2, under elevated CO2 high N contents was observed. However N contents of root under elevated CO2 increased successively and was higher that of root than under ambient CO2. In the end elevated CO2 reduced dry mass and N contents of leaf and fruit significantly. The elevation of temperature under elevated CO2 condition reduced dry mass and N contents of fruit and leaf. And similar response same as response to fruit and leaf was also observed for fertilizer efficiency. The elevation of CO2 concentration significantly increased 2M KCl non-extractable N from 18 to 47%. Elevated temperature didn¡¯t affect 2M KCl non-extractable N significantly, except for 40 DAT. Nitrogen deficiency due to enhanced immobilization and stimulated plant growth under elevated CO2 can induce leaf senescence. Because nitrogen released from senescing leaves was more remobilized into vegetative parts than reproductive part, we suggested that sink demand of vegetative parts for nitrogen increased.