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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil respiration is mediated by microbial activities, temperature, humidity and other environmental factors in soil. The increase in use of microbial organic fertilizer and drip irrigation in greenhouse production could alter soil micro-environment, particularly the rhizosphere, thereby leading to a change in soil respiration. This paper investigated the response of soil respiration to different combinations of drip irrigation amounts and microbial organic fertilizer applications. We experimentally compared three irrigation amounts 15, 18 and 21 mm – associated with three microbial organic fertilizer applications 2800, 3600 and 4400 kg/hm². The treatment with inorganic fertilizer application served as the control. In each treatment, we measured soil respiration rate and accumulated carbon emission, as well as other determinants. The soil temperature and humidity were measured following the soil respiration measurement using the delta-T sensor (delta-T company, UK); soil organic matter was measured using the potassium dichromate sulfuric acid oxidation external heating method; the activity of dehydrogenase was determined using the TTC colorimetry method; the activity of urease was determined by the phenol sodium colorimetry method; the activity of catalase was determined by the KMnO4 volumetric method. We analyzed the responsive change in soil respiration to these determinants and root biomass. The results showed that, compared to the CK, drip irrigation and microbial organic fertilization improved soil organic matter and increased the activities of dehydrogenase, urease and catalase by 11.6%-27.6%, 8.0%-27.7% and 1.8%-11.2%, respectively; the increase in urease activities was at significant level (p<0.05). The soil respiration rate was positively correlated to the root biomass, temperature and organic matter content at significant level of p<0.01, and to the enzymatic activities at significant level of p<0.05. Among all treatments, irrigating 18 mm of water and applying 4400 kg/hm² of microbial organic fertilizer produced the highest root biomass, reaching 394 g/m² 120 days after the transplanting. Overall, combining drip irrigation and microbial organic fertilization increased root biomass by 25.9%-43.4%, compared to the CK. When irrigation amount was 15 and 18 mm, the carbon emission increased significantly (p<0.05) when the fertilizer application increased from 3600 kg/hm² to 4400 kg/hm². The cumulative carbon emission peaked at 415.2 g/m² when the irrigation amount was 18 mm and the microbial fertilization was 4400 kg/hm², significantly higher than that under other treatments (p<0.05). The lowest cumulative carbon emission was from the CK, being 255.3 g/m² only. In summary, this study showed that drip irrigation and microbial organic fertilization combined to impact soil carbon emission by changing organic matter content and root biomass in the soil. Our results have important implications for improving ecological cultivation in greenhouse production. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Warming climate has been a global concern. Methane is an important greenhouse gas. Double rice cropping system in Hunan province contributes a large proportion of the national rice production. In this study, we studied the effect of agricultural managements of rice on methane emissions from double cropping paddy fields in Hunan Province, China based on Meta-analysis method. Only studies designed as side-by-side paired field experiments were included in this study. Field management practices, treatments, and controls were described in detail in each study, and the location of the experiment was provided. If seasonal accumulative CH4 emission fluxes were not directly provided, these values were calculated by multiplying time and mean CH4 emissions by the measurement period. A total of 53 published peer-reviewed papers published before 2018were obtained by reference retrieval. From them, 840 groups of data were drawn. The management measures included crop rotation, symbiosis ecosystem, tillage, nitrogen fertilizer input, organic manure and residue retention. The control and treatment groups were fallow versus winter crops, paddy-rice system versus rice-duck and rice-fish systems, conventional versus no tillage, no fertilizer-N input versus fertilizer-N input, no manure input versus fertilizer-N and manure input, and fertilizer-N input versus residue retention. Natural log of response ratio was used as the effect size in the random effect meta-analysis. Results showed that CH4 emissions from both early and late rice accounted for 97.9% of annual CH4 emissions, and more CH4 emissions from late rice was observed than that for early rice. In the double rice cropping system, adding winter crops could significantly increase CH4 emissions from double rice season by 43.88% (P < 0.05) compared to winter fallow. Moreover, the increase in methane emissions from early rice was significantly higher than that from late rice. Symbiosis ecosystem of rice (i.e., with ducks or fishes) and adopting no-till significantly decreased CH4 emissions by 37.02% and 26.84% (P < 0.05), respectively. The decrease in the emission from early rice field was much higher than that from late rice field. As for yield-scaled emission, application of N fertilizer decreased yield-scaled CH4 emissions by 40.01% (P < 0.05) mainly due to the yields increased by 73.87% (P < 0.05). Additionally, organic fertilizer application and residue retention increased 68.11% and 71.80% (P < 0.05) of yield-scaled CH4 emissions without impacting the rice yield. The results suggested adopting symbiosis ecosystem rice production or no-till along with optimized N input is conducive to balancing rice yield and CH4 emissions from fields with double rice cropping system in Hunan province. [ABSTRACT FROM AUTHOR]