Analysis of daily dynamics of soil respiration rate in greenhouse vegetable fields

As an important component of ecosystem carbon (C) budget, soil respiration is critical for soil-plant C cycle. As an entirely different cropping system, greenhouse vegetable system is characterized as excessive nutrient input, intensive land use, high temperature and high humidity and airtight environment. All of these factors have considerable influence on soil respiration rate and C cycle. With increasing greenhouse vegetable production in China, CO₂ emission in greenhouse vegetable systems can not be ignored in the whole agricultural production system. In addition to studies of seasonal variations of soil respiration rate in greenhouse vegetable fields, understanding daily variation characteristics of soil respiration rate can enhance the estimation of the effects of CO₂ emission on the environment and crop growth in greenhouse vegetable system. Thus this study investigated the driving factors and characteristics of daily dynamics of soil respiration rate under different organic manure and N (nitrogen) fertilizer inputs in a greenhouse vegetable field. The infrared gas analyzer (IRGA)-closed chamber technique was used to analyze greenhouse vegetable conditions in 2009 2010 in Shouguang City, Shandong Province. Four measurements were taken to determine daily variations in soil respiration rate during the main growth period. The results showed that the application of organic manure and wheat straw significantly improved soil respiration rate, especially in the treatments with high N fertilizer where the soil respiration rates were highest. Although some differences existed in soil respiration rate among different treatments in different seasons, daily dynamics of soil respiration rate were similar for all the treatments. With rising temperature, soil respiration rate increased steadily and the highest soil respiration rate occurred 14:00 17:00, which was later than the highest temperature. Also with rising temperature, CO₂ increased steadily. High temperature and CO₂ concentration inhibited soil respiration rate in greenhouse vegetable fields. Based on the four measurements over the study period, soil respiration rates during 8:00 11:00 a.m. were similar to daily average rates. This suggested that soil respiration rate during 8:00 11:00 a.m. could be used to estimate CO₂ emission in greenhouse fields. Fertilization, temperature and near-ground CO₂ concentration were the main driving factors of the daily dynamics of soil respiration rate. Optimal regulation was critical for reducing CO₂ emission and enhancing sustainable development of greenhouse vegetable production in China.