长期施肥和秸秆还田对设施蔬菜土壤有机碳的影响

为了明确施肥和秸秆还田等措施对华北地区设施蔬菜土壤有机碳的影响，该研究以寿光设施蔬菜生产为对象，进行了连续11 a的长期定位试验，设置了对照（CK）、有机肥+秸秆还田（MS）、有机肥+优化氮肥（N1M）、有机肥+常规氮肥（N2M）、有机肥+优化氮肥+秸秆还田（N1MS）、有机肥+常规氮肥+秸秆还田（N2MS）6个处理，通过测定分析土壤有机碳含量、储量、有机物料碳转化效率、固碳速率等，探讨不同施肥和秸秆还田措施下土壤有机碳的变化规律。结果表明，施加有机肥+优化氮肥条件下，N1MS处理可以提高＞30～60 cm土壤有机碳含量，比N1M处理显著提高了40.5%（P＜0.05），而施加有机肥+常规氮肥条件下，施加秸秆的增碳效果不明显；N2M显著增加表层（0～30 cm）土壤有机碳含量（P＜0.05），比N1M处理提升47.0%；在有机肥+秸秆还田条件下，0～30 cm土层土壤有机碳随着施氮量的增加而增加，增加量大小顺序为N2MS（106.5%）＞N1MS（64.2%）＞MS（39.9%）；N2MS的土壤固碳速率在0～30和0～90 cm土层分别为1.85和3.74 t/(hm2?a)。因此，只考虑表层（0～30 cm）土壤固碳是远远不够的，应重视设施蔬菜等集约农业生产方式的深层土壤固碳。施用氮肥有利于提高有机物料转换为土壤有机碳的效率，且随着氮肥量的增加，有机物料的碳转化效率明显提高。设施蔬菜生产中，由于有机肥投入水平较高，秸秆还田转化为土壤有机碳的效率反而降低，秸秆还田和氮肥之间并未显现出对土壤有机碳的正交互作用，应进一步优化肥料和秸秆投入方式和水平，在维持蔬菜高产的前提下提高资源利用效率。

Effects of long-term fertilization and straw returning on soil organic carbon in plastic-shed vegetable production

Abstract: China has a vast acreage of cropland for plastic-shed vegetable production, in which carbon sequestration and greenhouse gas emission reduction achieved via various optimized farming practices are of great significance to the green agricultural development of the nation and of the world. In order to clarify the effects of fertilizer application and straw returning on soil organic carbon (SOC) in plastic-shed vegetable production in northern China, a long-term field experiment initiated in 2004 was conducted in Shouguang plastic-shed vegetable base. In this experiment, 6 treatments were set up to study the change rule of soil organic carbon under different fertilization and straw returning measures by measuring and analyzing soil organic carbon content, storage, carbon conversion efficiency of organic materials, and carbon fixation rate of organic matter. The treatment included control (CK), organic fertilizer + straw return (MS), organic fertilizer + optimized nitrogen (N) fertilization (N1M), organic fertilizer + conventional N fertilization (N2M), organic fertilizer + optimized N fertilization combined with straw return (N1MS), and organic fertilizer + conventional N fertilization combined with straw return (N2MS). The SOC contents and stocks at 0-30, >30-60, and >60-90 cm layers for pre- and post-experiment were monitored. The results showed that N1MS treatment could significantly increase soil organic carbon content in 30~60 cm soil layer (P<0.05), which was 40.5% higher than that of N1M treatment, while under N2M treatment, the effect of straw returning on SOC increasing was not significant. N2M treatment significantly increased the soil organic carbon content by 47.0% for 0-30 cm and 17.3% for >60-90 cm layers, compared with that of optimized N fertilization (N1M). With the application of organic fertilization and straw returning, SOC contents in the 0-30 cm layer increased with the increase of N fertilization application, and the increase of SOC content was at the order of N2MS (106.5%) > N1MS (64.2%) > MS (39.9%). In the 0-90 cm soil layer, the highest SOC stock was 115.5 t/hm2 for N2MS in 2015, followed by 110.5, 104.0, 101.7, and 98.0 t/hm2 for N2M, N1MS, MS, and N1M treatments, respectively, and all were significantly higher than those without organic fertilizer (CK). the SOC sequestration rate of N2MS in 0-30 and 0-90 cm layers was 1.85 and 3.74 t/(hm2?a) respectively, which indicated that for intensive cropping like plastic-shed vegetable production, deep-soil carbon stock should be accounted for national carbon quantification. In the 0-30 cm soil layer, the organic material carbon conversion efficiency of the scenario of conventional N fertilization was significantly higher than that of optimized N fertilization, in which N2M was 204.9% higher than that of N1M and N2MS was 130.3% higher than that of N1MS, which indicated the increase of N fertilization rate was helpful to improve the conversion efficiency of organic materials to SOC. In the 0-30?cm soil layer, the carbon conversion efficiency of organic material in N1M treatment was 35.5% higher than that in N1MS, and in N2M it was 79.4% higher than that in N2MS. In plastic-shed vegetable production, straw returning reduced the conversion efficiency of organic matter to organic carbon, and fertilizer nitrogen and straw returning have no positive interaction on organic carbon accumulation, due to the high level of organic fertilizer. In China, the carbon sequestration efficiency and carbon conversion efficiency of organic fertilizer and straw in plastic-shed vegetable production should be further improved by optimizing chemical and organic fertilizer inputs.