滴灌和微生物有机肥对设施土壤呼吸的耦合作用及机制

为研究滴灌水分和微生物有机肥对设施土壤呼吸的影响及耦合作用机制,设计不同灌溉定额(15、18、21 mm)和不同微生物有机肥施用量(2 800、3 600、4 400 kg/hm2)处理,以传统化肥处理为对照,观测滴灌和微生物有机肥协同作用下土壤呼吸速率、累计碳排放量等指标,分析土壤呼吸与土壤温度、湿度、有机质含量、酶(脱氢酶、脲酶和过氧化氢酶)活性及根系生物量之间的互动响应关系。结果表明:滴灌-微生物有机肥处理有利于提高土壤有机质含量和酶活性,土壤脱氢酶、脲酶和过氧化氢酶活性分别提升11.6%～27.6%、8.0%～27.7%和1.8%～11.2%,其中滴灌和微生物有机肥相结合对脲酶活性的影响达到显著(p0.05)水平;土壤呼吸速率与根系生物量、土壤温度和有机质含量呈极显著(p0.01)正相关,与土壤酶活性呈显著(p0.05)正相关。该研究证明了滴灌和微生物有机肥对土壤碳排放有显著的耦合效应,滴灌和微生物有机肥耦合主要通过改变土壤有机质含量和根系生物量,对土壤呼吸产生影响。

Coupling effect and mechanism of drip irrigation and microbial organic fertilization on soil respiration in greenhouse

Abstract: 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.