Grasses of the Urochloa genus have been widely used in crop-livestock integration systems or as cover crops in no-till systems such as in rotation with maize. Some species of Urochloa have mechanisms to reduce nitrification. However, the responses of microbial functions in crop-rotation systems with grasses and its consequence on soil N dynamics are not well-understood. In this study, the soil nitrification potential and the abundance of ammonifying microorganisms, total bacteria and total archaea (16S rRNA gene), nitrogen-fixing bacteria (NFB, nifH ), ammonia-oxidizing bacteria (AOB, amoA ) and archaea (AOA, amoA ) were assessed in soil cultivated with ruzigrass ( Urochloa ruziziensis ), palisade grass ( Urochloa brizantha ) and Guinea grass ( Panicum maximum ). The abundance of ammonifying microorganisms was not affected by ruzigrass. Ruzigrass increased the soil nitrification potential compared with palisade and Guinea grass. Ruzigrass increased the abundance of N-fixing microorganisms at the middle and late growth stages. The abundances of nitrifying microorganisms and N-fixers in soil were positively correlated with the soil N–NH 4 + content. Thus, biological nitrogen fixation might be an important input of N in systems of rotational production of maize with forage grasses. The abundance of microorganisms related to ammonification, nitrification and nitrogen fixing and ammonia-oxidizing archea was related to the development stage of the forage grass.

中文翻译：

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综合种植系统中微生物氮循环基因丰度受覆盖作物种类和发育阶段的影响

Urochloa 属的草已广泛用于作物-牲畜整合系统或作为免耕系统中的覆盖作物，例如与玉米轮作。某些种类的 Urochloa 具有减少硝化作用的机制。然而，微生物功能在禾本科作物轮作系统中的反应及其对土壤氮动态的影响尚不清楚。本研究中，土壤硝化潜力和氨化微生物、总细菌和总古细菌（16S rRNA基因）、固氮细菌（NFB、nifH）、氨氧化细菌（AOB、amoA）和古细菌（AOA、 amoA ) 是在用红豆草 (Urochloa ruziziensis)、栅栏草 (Urochloa brizantha) 和几内亚草 (Panicum maximum) 栽培的土壤中进行评估的。氨化微生物的丰度不受红枣的影响。与栅栏和几内亚草相比，Ruzigrass 增加了土壤硝化潜力。Ruzigrass 在生长中期和后期增加了固氮微生物的丰度。土壤中硝化微生物和固氮剂的丰度与土壤N-NH 4 + 含量呈正相关。因此，生物固氮可能是牧草玉米轮作生产系统中氮的重要输入。氨化、硝化、固氮和氨氧化古菌相关微生物的丰度与牧草的发育阶段有关。土壤中硝化微生物和固氮剂的丰度与土壤N-NH 4 + 含量呈正相关。因此，生物固氮可能是牧草玉米轮作生产系统中氮的重要输入。氨化、硝化和固氮及氨氧化古菌相关微生物的丰度与牧草的发育阶段有关。土壤中硝化微生物和固氮剂的丰度与土壤N-NH 4 + 含量呈正相关。因此，生物固氮可能是牧草玉米轮作生产系统中氮的重要输入。氨化、硝化、固氮和氨氧化古菌相关微生物的丰度与牧草的发育阶段有关。