Abstract:
Abstract: Rice (Oryza sativa L.) is the main grain crops in China, and it has a very important strategic significance in the development of grain production and agriculture. Oxygen is an important environmental factor in paddy field ecosystem, which can affect the plant nitrogen metabolism and soil nitrogen transformation, and often plays a limiting role in rice growth and development. An experiment was conducted to reveal the effects of aeration methods on soil redox potential, nitrogen transformation in soil and nitrogen utilization of rice with Zhongzheyou 1 (lowland rice), IR45765-3B (deep-water rice) and Zhonghan 221 (upland rice) as materials in China National Rice Research Institute located at Hangzhou City, Zhejiang Province, China. There were four treatments, calcium peroxide application (T1), micro-bubble aerated water irrigation (T2), topsoil moist irrigation (T3) and water-logging (control CK). Split plot design was used with different aeration treatments as the main plots and cultivars as the sub-plots. The plots area was 2.6 m2 and repeated 3 times randomized complete block design. The results showed that the aeration methods significantly improved soil redox potential (Eh). Soil redox potential under the condition of the three aeration methods was higher than that of control. Oxygen enrichment in paddy field promoted the nitrification of soil nitrogen. The soil nitrification intensity and urease activity of T1, T2, and T3 were significantly higher than that of CK at tillering stage and full heading stage. In contrast, the denitrification intensity of T1, T2, and T3 were remarkably lower than that of CK. The oxygen enrichment treatments could affect the uptake of rice nitrogen differently. N accumulation amounts of the three rice cultivars were considerably higher in T1 and T2 than in CK at jointing, full heading and full ripe stage, while it was substantially lower than that of CK in T3. At full ripe stage, total N accumulation amounts of Zhongzheyou 1, IR45765-3B and Zhonghan 221were increased by 21.2%, 13.2% and 17.0%, respectively, in T1 as compared with control, and increased by 14.3%, 6.9% and 9.1%, respectively, in T2. However, it was 11.5%, 13.4% and 13.4%, respectively, lower than that of control in T3, with considerable differences between treatments (P<0.05). Compared with control, the grain yield and harvest index of T1 and T2 were greatly increased. But their nitrogen grain production efficiency had no significant difference compared with CK. However, nitrogen biomass production efficiency and nitrogen grain production efficiency in T3 were considerably higher than that in control. Different aeration methods resulted in the differences of N harvest index among cultivars. The results indicated that application of calcium peroxide and micro-bubble aerated water irrigation effectively improved the redox state of paddy soil. They not only increased rice yield significantly, but also strengthened soil nitrification. Therefore, it reduced nitrogen loss, in turn increased N accumulation and N harvest index of rice. Based on the results, the application of calcium peroxide as complementary fertilizer and micro-bubble aerated water irrigation are able to reduce the loss of nitrogen and increase the utilization rate of nitrogen in rice, which is beneficial for the high yield and sustainable development of rice.