Xu Lijun, Li Da, Wang Di, Ye Liming, Nie Yingying, Fang Huajun, Xue Wei, Bai Chunli, Van Ranst Eric
Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China.
Department of Grassland Research, Baicheng Institute of Animal Husbandry, Baicheng, China.
Front Plant Sci. 2022 Sep 29;13:985864. doi: 10.3389/fpls.2022.985864. eCollection 2022.
Grassland is the primary land use in China but has experienced severe degradation in recent decades due to overgrazing and conversion to agricultural production. Here, we conducted a field experiment in northeastern Inner Mongolia to test the effectiveness of sown pastures in lowering the grazing pressure on grasslands and raising the quality of marginal soils. Alfalfa and smooth bromegrass monocultures and mixture were sown in a marginal cropland field in Hulunber in June 2016. Biomass productivity, soil physicochemical, and biological properties were monitored annually from 2016 to 2020. The results showed that the marginal cropland soil responded consistently positively to sown pastures for major soil properties. Soil organic carbon (SOC) and total nitrogen (TN) increased by 48 and 21%, respectively, from 2016 to 2020 over the 0-60 cm soil depth range. Soil microbes responded proactively too. The soil microbial biomass C (SMBC) and N (SMBN) increased by 117 and 39%, respectively, during the period of 2016-2020. However, by the end of the experiment, the soil of a natural grassland field, which was included in the experiment as a control, led the sown pasture soil by 28% for SOC, 35% for TN, 66% for SMBC, and 96% for SMBN. Nevertheless, the natural grassland soil's productive capacity was inferior to that of the sown pasture soil. The average aboveground biomass productivity of sown pastures was measured at 8.4 Mg ha in 2020, compared to 5.0 Mg ha for natural grassland, while the root biomass of sown pastures was averaged at 7.5 Mg ha, leading the natural grassland by 15%. Our analyses also showed that the sown pastures' biomass productivity advantage had a much-neglected potential in natural grassland protection. If 50% of the available marginal cropland resources in Hulunber under the current environmental protection law were used for sown pastures, the livestock grazing pressure on the natural grasslands would decrease by a big margin of 38%. Overall, these results represent systematic empirical and analytical evidence of marginal cropland soil's positive responses to sown pastures, which shows clearly that sown pasture is a valid measure both for soil rehabilitation and biomass production.
草原是中国主要的土地利用类型，但近几十年来，由于过度放牧和转为农业生产，草原经历了严重退化。在此，我们在内蒙古东北部进行了一项田间试验，以测试人工草地在减轻草原放牧压力和提高边际土壤质量方面的有效性。2016年6月，在呼伦贝尔的一块边际农田中播种了苜蓿和无芒雀麦的单作及混作。从2016年到2020年，每年监测生物量生产力、土壤理化性质和生物学性质。结果表明，边际农田土壤对人工草地的主要土壤性质反应始终呈积极态势。在0至60厘米土壤深度范围内，2016年至2020年期间，土壤有机碳（SOC）和全氮（TN）分别增加了48%和21%。土壤微生物也积极响应。2016年至2020年期间，土壤微生物生物量碳（SMBC）和氮（SMBN）分别增加了117%和39%。然而，到试验结束时，作为对照纳入试验的天然草地土壤的SOC比人工草地土壤高28%，TN高35%，SMBC高66%，SMBN高96%。尽管如此，天然草地土壤的生产能力低于人工草地土壤。2020年，人工草地地上生物量生产力平均为8.4吨/公顷，而天然草地为5.0吨/公顷，同时人工草地根系生物量平均为7.5吨/公顷，比天然草地高15%。我们的分析还表明，人工草地的生物量生产力优势在天然草地保护方面具有一个被严重忽视的潜力。如果根据现行环境保护法，将呼伦贝尔市50%的可用边际农田资源用于种植人工草地，天然草地的牲畜放牧压力将大幅降低38%。总体而言，这些结果代表了边际农田土壤对人工草地积极反应的系统实证和分析证据，清楚地表明人工草地是土壤修复和生物量生产的有效措施。
