Effects of N-applications and photosynthesis of maize ( Zea mays L.) on soil respiration and its diurnal variation

Abstract

In order to understand the relationship of soil respiration to N-applications and photosynthesis, a soil pot experiment of planting maize with two N-applications was conducted. During the trumpeting stage, maize plants were shaded for three days and soil respiration was sampled by static chamber method and measured by gas chromatography. A clear diurnal cycle of soil respiration rate (SRR) showed a single peak curve in which the rate crested at about 14:00 during a day-night period and the daily average SRR was very close to that between 18:00 and 21:00. The SRR increased with soil N-application and the measured average SRR in three days was 29% higher in high N-application (HN, 300mg∙kg^−1 of N) than that in low N-application (LN, 150mg∙kg^−1 of N). The shaded plants significantly decreased the SRR and its diurnal variation. The soil respiration within the first, second and third day-night decreased to about 21%, 50% and 65%, respectively compared with the un-shaded plants. Under non-shading treatments, the exponential relativity of SRR was significantly dependent on temperature but not on time, while in shaded plants, it was significantly dependent on both temperature and shading time, with the relative coefficient to shading time significantly higher than that to temperature. In summary, soil N-application could increase the soil respiration, while the shaded plants not only decreased the SRR and its diurnal variation but also altered the relationship between the SRR with temperature, thus the soil respiration during maize growth was mainly derived from the recent photosynthates. Photosynthesis, together with temperature, are the key factors controlling the diurnal variation of soil respiration.

Key words： soil respiration; diurnal variation; N-application; shading plant; photosynthesis; temperature