Weed encroachment might reduce stocking rate and overall animal performance in grazing systems. In addition, weeds can affect soil organic carbon because of changes in primary productivity and belowground biomass compared with well managed pastures. This study assessed different levels of spiny pigweed (Amaranthus spinosus L.) encroachment on bermudagrass [Cynodon dactylon (L.) Pers.] pastures. Spiny pigweed was drilled onto bermudagrass pastures to create three levels of encroachment: weed free, medium encroachment, and high encroachment. The weed-free pastures were treated with herbicide to control weed encroachment, and the medium had strips where weeds were controlled and strips uncontrolled. The high encroachment had no weed control. Treatments (weed free, medium, and high) were allocated in a randomized complete block design. The spiny pigweed was drilled in 2020 and grazing occurred from 2021 to 2023. Soil samples were collected in October 2023 to assess soil organic carbon (C) stock by determining soil bulk density and soil C concentration in the 0- to 5- and 5- to 15-cm layers. Results indicated that weed-free and medium-encroached pastures had greater soil organic carbon stock (20.2 Mg C/ha) compared with the weed-infested pastures (17.2 Mg C/ha). Soil C concentration was similar, but soil bulk density was lower in the weed-infested pastures, affecting soil carbon stocks.

中文翻译：

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PSXIII-6 杂草侵占减少了百慕大草牧场的土壤有机碳储量


杂草侵占可能会降低放牧率和放牧系统中动物的整体性能。此外，与管理良好的牧场相比，杂草会影响土壤有机碳，因为初级生产力和地下生物量发生了变化。本研究评估了多刺猪草 （Amaranthus spinosus L.） 对百慕大草 [Cynodon dactylon （L.） Pers.] 牧场的不同程度的侵占。在百慕大草牧场上钻取多刺猪草，以产生三个级别的侵占：无杂草、中度侵占和高度侵占。无杂草的牧场用除草剂处理以控制杂草的侵占，培养基有条带，杂草得到控制的地方和不受控制的条带。高侵占区没有杂草控制。处理 （无杂草、中和高） 以随机完全区组设计分配。多刺猪草于 2020 年钻孔，2021 年至 2023 年进行放牧。2023 年 10 月收集了土壤样本，通过测定 0 至 5 厘米和 5 至 15 厘米层的土壤容重和土壤 C 浓度来评估土壤有机碳 （C） 储量。结果表明，与杂草出没的牧场 （17.2 Mg C/ha） 相比，无杂草和中度侵占的牧场具有更高的土壤有机碳储量 （20.2 Mg C/ha）。土壤 C 浓度相似，但在杂草出没的牧场中土壤容重较低，影响土壤碳储量。