Intercropping kura clover (Trifolium ambiguum) (KC) with prairie cordgrass (Spartina pectinata) (PCG) has great potential for biofuel feedstock on marginal lands. This study evaluated the impacts of 10‐year PCG‐KC intercropping and PCG monoculture fertilized with different nitrogen (N) rates of granular urea (five treatments: PCG‐KC, PCG‐0N, PCG‐75N, PCG‐150N, and PCG‐225N) on soil biogeochemical properties: (i) in the surface soil (0‐ to 10‐cm depth) at three different sampling times during the crop growing season: spring (April, pre‐emergence), summer (June, active growth), and fall (November, post‐harvest); and (ii) at different soil depths (0–5, 5–15, 15–30, 30–45, and 45–60 cm) (only total carbon (C) and N) in fall 2021. All soil biogeochemical parameters were higher during summer as compared to spring and/or fall, except urease activity, ammonium‐N, microbial biomass C and N, and fluorescein diacetate (FDA). On average over the sampling times, PCG‐KC had significantly higher β‐glucosidase activity and hot‐water extractable organic N than PCG‐0N; but no significant difference between PCG‐KC and N‐fertilized PCG. Cold‐water extractable organic N was significantly lower than the highest N rate, but not significantly different from PCG‐0N and lower N rate treatments. Urease activity under PCG‐KC treatment was double that of PCG‐0N and PCG‐75N; FDA was higher in PCG‐KC than all monocultures. No treatment effect was found on soil total C and N, except that they decreased with depth. Overall, intercropping PCG‐KC showed some benefits in terms of promoting soil biogeochemical properties during crop growth periods, having lower residual reactive N in the soil, and maintaining biomass yield and quality on marginal lands.

中文翻译：

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草原绳草与库拉三叶草间作对土壤生物地球化学影响不大

间作库拉三叶草（三叶草) (KC) 与草原绳草 (梳状大米草) (PCG) 在边际土地上作为生物燃料原料具有巨大潜力。本研究评估了 10 年 PCG-KC 间作和 PCG 单作施用不同氮 (N) 比例的颗粒尿素施肥的影响（五种处理：PCG-KC、PCG-0N、PCG-75N、PCG-150N 和 PCG- 225N）对土壤生物地球化学性质的影响：（i）在作物生长季节的三个不同采样时间的表层土壤（0至10厘米深度）中：春季（四月，出苗前），夏季（六月，生长活跃）和秋季（十一月，收获后）； (ii) 2021 年秋季在不同土壤深度（0-5、5-15、15-30、30-45 和 45-60 厘米）（仅总碳 (C) 和 N）。所有土壤生物地球化学参数均为与春季和/或秋季相比，夏季较高，但脲酶活性、铵态氮、微生物生物量 C 和 N 以及荧光素二乙酸酯 (FDA) 除外。平均而言，在采样时间内，PCG-KC 的 β-葡萄糖苷酶活性和热水可萃取有机氮显着高于 PCG-0N；但 PCG-KC 和施氮肥的 PCG 之间没有显着差异。冷水可萃取有机氮显着低于最高施氮量，但与 PCG-0N 和较低施氮量处理没有显着差异。 PCG-KC处理下的脲酶活性是PCG-0N和PCG-75N的两倍； PCG-KC 中的 FDA 高于所有单一培养物。没有发现处理对土壤全碳和全氮有影响，只是它们随着深度的增加而减少。总体而言，间作 PCG-KC 在促进作物生长期土壤生物地球化学性质、降低土壤中残留活性氮以及维持边际土地的生物量产量和质量方面显示出一些好处。