Guest Emily J, Palfreeman Lucy J, Holden Joseph, Chapman Pippa J, Firbank Les G, Lappage Martin G, Helgason Thorunn, Leake Jonathan R
Plants, Photosynthesis and Soil, School of Biosciences, The University of Sheffield, Sheffield S10 2TN, UK; ADAS Boxworth, Battle Gate Road, Cambridge CB23 4NN, UK.
Plants, Photosynthesis and Soil, School of Biosciences, The University of Sheffield, Sheffield S10 2TN, UK.
Sci Total Environ. 2022 Dec 15;852:158358. doi: 10.1016/j.scitotenv.2022.158358. Epub 2022 Aug 29.
Conventional arable cropping with annual crops established by ploughing and harrowing degrades larger soil aggregates that contribute to storing soil organic carbon (SOC). The urgent need to increase SOC content of arable soils to improve their functioning and sequester atmospheric CO has motivated studies into the effects of reintroducing leys into long-term conventional arable fields. However, effects of short-term leys on total SOC accumulation have been equivocal. As soil aggregation may be important for carbon storage, we investigated the effects of arable-to-ley conversion on cambisol soil after three years of ley, on concentrations and stocks of SOC, nitrogen and their distributions in different sized water-stable aggregates. These values were benchmarked against soil from beneath hedgerow margins. SOC stocks (0-7 cm depth) rose from 20.3 to 22.6 Mg ha in the arable-to-ley conversion, compared to 30 Mg ha in hedgerows, but this 2.3 Mg ha difference (or 0.77 Mg C ha yr) was not significant). However, the proportion of large macroaggregates (> 2000 μm) increased 5.4-fold in the arable-to-ley conversion, recovering to similar abundance as hedgerow soils, driving near parallel increases in SOC and nitrogen within large macroaggregates (5.1 and 5.7-fold respectively). The total SOC (0-7 cm depth) stored in large macroaggregates increased from 2.0 to 9.6 Mg ha in the arable-to-ley conversion, which no longer differed significantly from the 12.1 Mg ha under hedgerows. The carbon therefore accumulated three times faster, at 2.53 Mg C ha yr, in the large macroaggregates compared to the bulk soil. These findings highlight the value of monitoring large macroaggregate-bound SOC as a key early indicator of shifts in soil quality in response to change in field management, and the benefits of leys in soil aggregation, carbon accumulation, and soil functioning, providing justification for fiscal incentives that encourage wider use of leys in arable rotations.
通过犁地和耙地种植一年生作物的传统耕作方式会破坏有助于储存土壤有机碳（SOC）的较大土壤团聚体。迫切需要提高耕地土壤的有机碳含量以改善其功能并封存大气中的二氧化碳，这促使人们研究在长期传统耕地上重新引入牧草的效果。然而，短期牧草对土壤有机碳总量积累的影响一直存在争议。由于土壤团聚可能对碳储存很重要，我们研究了在种植三年牧草后，从耕地转变为草地对始成土土壤的影响，包括土壤有机碳、氮的浓度和储量及其在不同大小水稳性团聚体中的分布。这些数值以树篱边缘下方的土壤为基准。与树篱土壤中30 Mg/ha相比，从耕地转变为草地后，土壤有机碳储量（0 - 7厘米深度）从20.3 Mg/ha增加到22.6 Mg/ha，但这2.3 Mg/ha的差异（或0.77 Mg C/ha·年）并不显著。然而，在从耕地转变为草地的过程中，大型大团聚体（> 2000微米）的比例增加了5.4倍，恢复到与树篱土壤相似的丰度，促使大型大团聚体内的土壤有机碳和氮近乎平行增加（分别增加5.1倍和5.7倍）。在从耕地转变为草地的过程中，大型大团聚体中储存的土壤有机碳总量（0 - 7厘米深度）从2.0 Mg/ha增加到9.6 Mg/ha，与树篱下的12.1 Mg/ha不再有显著差异。因此，与整体土壤相比，大型大团聚体中的碳积累速度快三倍，为2.53 Mg C/ha·年。这些发现突出了监测与大型大团聚体结合的土壤有机碳作为土壤质量响应田间管理变化而转变的关键早期指标的价值，以及牧草在土壤团聚、碳积累和土壤功能方面的益处，为鼓励在轮作中更广泛使用牧草的财政激励措施提供了依据。
