地膜覆盖对北方旱地土壤水稳性团聚体及有机碳分布的影响

研究不同地膜覆盖时间对北方旱作农田土壤团聚体粒级稳定性和有机碳的影响,可为提升旱作农田生产力和保护农田环境选择合适的管理方式提供科学依据。以辽宁阜新5年秋覆膜(AP)、春覆膜(SP)和不覆膜(CK)的定位试验为研究对象,分析不同覆膜时间对0—10 cm和10—20 cm土层中2 mm、0.25—2 mm、0.053—0.25 mm和0.053 mm粒级的土壤水稳性团聚体的稳定性及有机碳的影响。结果表明,在北方旱作农田,连续5年的地膜覆盖可显著改变0—10 cm土层的土壤各级团聚体的分布、团聚体中有机碳的含量及其对土壤有机碳含量的贡献率,进而增加土壤水稳性团聚体的稳定性,而对10—20 cm土层影响不显著。与不覆膜相比,秋覆膜和春覆膜可显著提高0—10 cm土层2 mm的水稳性团聚体的含量,分别提高了36.3%、47.9%(P0.05),而对微团聚体无显著影响,说明地膜覆盖有利于提高大团聚体数量及稳定性。在0—10 cm土层,粒径2 mm团聚体有机碳含量及储量表现为秋覆膜最高,显著高于春覆膜和不覆膜处理(P0.05)。与裸地不覆膜相比,秋覆膜和春覆膜显著提高2 mm团聚体中有机碳含量对土壤有机碳的贡献率,分别提高了37%和26.1%(P0.05)。而在0—10 cm和10—20cm土层中,微团聚体中有机碳含量对土壤有机碳贡献率没有影响。在辽宁阜新土壤及种植条件下,秋覆膜处理不仅显著提高0—10 cm土壤水稳性大团聚体的含量和稳定性,还可以显著增加水稳性大团聚体有机碳含量及储量,促进有机碳的固存。

Effects of film mulching on soil aggregations and organic carbon contents in Northern dryland regions

Studying the effects of film mulching on soil aggregate stability and soil organic carbon distribution in different aggregate fractions can provide a scientific basis for exploring proper practices to improve the productivity and protect the environment in dryland farming. A long-term field experiment has been conducted in Fuxin, Liaoning province since 2012. Three treatments were carried out:non-mulching (CK), autumn plastic film mulching (AP), and spring plastic film mulching (SP). The soil aggregate and soil organic carbon (SOC)contents of different aggregates (> 2, 0.25-2, 0.053-0.25, and < 0.053 mm)in 0-10 and 10-20 cm soil layers were measured using a wet sieving method. Our results showed that long-term plastic film mulching significantly affected the soil aggregate size distribution, aggregate stability, and organic carbon content in the 0-10 cm soil layer, especially under AP while there was no significant difference among treatments in the 10-20 cm soil layer. Compared to CK, the amounts of > 2 mm water-stable aggregates under AP and SP significantly increased by 36.3% and 26.7%, respectively. However, no obvious difference was observed in micro-aggregates. These results suggested that plastic film significantly affected the stability of soil aggregates and accumulation of aggregate into macro-aggregates. The mean weight diameter value of water-stable aggregate was significantly higher in AP and SP than in CK at 0-10 cm soil layer. Compared to CK, AP and SP significantly increased the total SOC contents and SOC in the aggregates > 2 mm in size at the 0-10 cm soil layer, increased by 8.2% and 47.9% as well as 4.6% and 29.2% (P < 0.05), respectively. The contribution rate of the > 2 mm aggregate in total SOC was obviously increased by 37% and 26.1% in AP and SP (P < 0.05), respectively. However, in the 0-10 and 10-20 cm soil layers, the SOC in the micro-aggregates (0.053-0.25, < 0.053 mm)did not significantly affect the contribution rate of total organic carbon. The results indicated that film mulching promoted the accumulation of aggregates into macro-aggregates. Under the soil and planting conditions in Liaoning, Autumn plastic film mulching can improve the stability of 0-10 cm soil water-stable aggregates and increase the SOC contents of macro-aggregates, as well as further promote the sequestration of organic carbon.