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Split Mineral Fertilizer Application Decreases Straw Mineralization and Priming Effect in Paddy Soil

Aug 19, 2019

In paddy soil, rice straw serves as an organic amendment that releases nitrogen (N), phosphorus (P), kalium (K), and other essential nutrients upon decomposition; thus, the addition of rice straw not only increases soil organic matter (SOM) content, but also maintains soil fertility.

However, straw addition can influence greenhouse gas (GHG) emissions (mainly CH4 and CO2) in paddy soil. Studies on CO2 and CH4 emissions from paddy soils have generally focused on full fertilizer applications, which do not correspond to the application patterns used in practice.

According to rice cultivation practices in China, fertilizer application is usually split into basal and top-dressing during the early tillering stage and the mid-season, respectively. Generally, splitting fertilizer application improves N and/or P use efficiency owing to a decrease in their relative losses. Therefore, split fertilization may lead to soil C sequestration and the reduction of GHG emissions.

Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences quantified the decomposition of 13C-labeled straw and the priming effect (PE) governed by the N and P fertilizer application pattern during a 100-day experiment in a flooded soil and discovered that the split N and P addition decreased straw mineralization and priming effect of a paddy soil.

The team found that the application of split N and P fertilization along with straw addition improved microbial enzyme activity, yielding the highest positive priming effect (PE) for CO2emission. Compared with the control (no addition), split N and P application decreased the positive PE for CH4 emission. Therefore, the straw-C-derived total CO2 equivalent emission was decreased by split N and P application.

This study also showed that the application of straw combined with split N and P addition appeared to provide an optimal supply of C, N, and P for the stoichiometric microbial nutrient requirement (i.e., met the require C:N:P ratio), which most likely decreased microbial mining of nutrients from SOM and therefore decreased the PE for  CO2 emission.

In addition, P fertilizer application increased the CH4 oxidation potential and reduced the total CH4 emission. "The important implication is that the split mineral fertilizer application may be considered as an optimal soil fertility management measure to increase exogenous C source anabolism and mitigate greenhouse gas emission from the paddy field ecosystem," said ZHU Zhenke, an associate researcher in ISA.

This research was funded by the National Science Foundation of China, Natural Science Foundation of Hunan Province, Innovative Research Groups of the Natural Science Foundation of Hunan Province, the Youth Innovation Team Project of the Institute of Subtropical Agriculture, Chinese Academy of Sciences, the Hunan Province Base for Scientific and Technological Innovation Cooperation, JSPS and NSFC under the Japan-China Scientific Cooperation Program, and the Public Service Technology Centre, Institute of Subtropical Agriculture, Chinese Academy of Sciences.

The study entitled "Split N and P addition decreases straw mineralization and the priming effect of a paddy soil: A 100-day incubation experiment" was published in Biology and Fertility of Soils. 

 

Figure 1. The CO2-equivalents of  CH4 and  CO2 emission, and the amount derived from straw and SOM in different treatments at the end of incubation (Image by ISA)


Figure 2. The structural equation model (SEM) showing the effects of multiple factors on the priming effect for  CO2 and CH4  (Image by ISA)

Contact

ZHU Zhenke

Institute of Subtropical Agriculture

E-mail:

Split N and P addition decreases straw mineralization and the priming effect of a paddy soil: a 100-day incubation experiment

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