摘要: 为探究马铃薯与玉米复合种植对化感物质积累与细菌群落结构的影响，分析轮作、间作缓解连作障碍的机制，本研究以马铃薯连作、玉米连作、马铃薯||玉米间作、马铃薯-玉米轮作第8年的土壤为对象，利用GC-MS测定土壤中化感物质含量，并采用Illumina Miseq高通量测序技术对土壤细菌16Sr DNA V4-V5区域进行测序，分析土壤中细菌多样性和群落结构的变化，并对化感物质和优势菌属进行相关性分析。结果表明：玉米连作和马铃薯连作会导致化感物质的积累，玉米连作土壤积累了更多的油酸、亚油酸、花生酸、木焦油酸等脂肪酸，马铃薯连作土壤积累了更多的硬脂醇、二十烷醇等脂肪醇类物质。轮作降低了大部分化感物质的积累，间作降低的化感物质种类相对轮作较少。不同种植方式下土壤细菌群落结构发生了显著变化，相对于连作，间作和轮作Ace指数和Chao指数显著升高。在门水平上，轮作土壤放线菌丰度显著高于马铃薯连作土壤，间作土壤拟杆菌门丰度显著低于玉米连作土壤，两种连作土壤中酸杆菌门丰度都较轮作显著升高。在属水平上，一些有益细菌如节杆菌属、溶杆菌属等在复合种植土壤中相对丰度更高。通过相关性分析发现土微菌属、小梨形菌属与脂肪醇类物质呈显著正相关，黄杆菌属、溶杆菌属、微杆菌属等与脂肪酸类物质呈显著负相关。马铃薯与玉米复合种植降低了化感物质在土壤中的积累，从而抑制了土壤细菌丰度的降低，提高了有益菌属丰度，消减了连作障碍。
摘要: Both Kenya and China are facing great challenges in feeding their populations; this is particularly problematic in Kenya, where the population will be projected to increase by 1.4 times from 2018 to 2100. Food production has been greatly improved in China, but it still lags behind in Kenya. In this study, we systematically compared the changes in agricultural resources and crop/livestock productivity, as well as their relationships with the resource input levels and agricultural production structure, to try to provide insights into reducing food insecurity and poverty in Kenya. Our results revealed that Kenya had 2-3 times more natural resources, such as cropland, grassland, and annual precipitation, per capita than did China in the 1960s, which was similar to the daily food energy and protein supply. Currently, Kenya still has higher natural resources per capita, but has lower food security and quality when compared to China. This is due to the continued rapid increase in crop and livestock productivity regarding energy and protein production in China. From 1961 to 2017, crop protein productivity increased by 44% in Kenya, while in China it increased by 282%. Our results showed that crop and livestock productivity positively correlated with the input of fertilizers, concentrate feeds, machinery, and pesticides, as seen in China. Meanwhile, the structure of crop and livestock production also showed a large impact on the changes in productivity, such as the harvest area of vegetables/fruits to the total harvest area and the ratio of monogastric animals for livestock production. Overall, both agrochemicals and structure have strong impacts on the increase in productivity, and these could be potential options in Kenya to improve productivity due to the low input of resources into crop and livestock production.