Changes in soil organic matter over 70 years in continuous arable and ley-arable rotations on a sandy loam soil in England.
Changes in soil organic matter over 70 years in continuous arable and ley-arable rotations on a sandy loam soil in England.
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DOI：
10.1111/ejss.12415
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发表时间：
2017-05
影响因子：
4.2
通讯作者：
White RP
中科院分区：
文献类型：
--
作者：
Johnston AE;Poulton PR;Coleman K;Macdonald AJ;White RP
在沙壤土上进行了70 多年的土壤有机碳固持实验，测量了土壤中大气二氧化碳的固持。这项试验最初是为了测试Leys对可耕地产量的影响。轮作3年的三叶草和三叶草(Gras + Clover)在28 年中使土壤表层25 cm的有机碳百分比(%OC)从0.98增加到1.23，但在接下来的40 年里，在全草种植的情况下，施氮(N)后几乎没有进一步增加。在这第二个时期，OC投入与损失相平衡，这表明大约1.3%的OC可能接近这次轮换的平衡含量。包括3年生的紫花苜蓿，在28 年中对有机碳的影响不大，但在接下来的40 年间，改种草 + 三叶草后，有机碳含量增加到1.24%。在20世纪70年代开始了每10年轮作一次的八年轮作(所有草都有N或草 + 三叶草)与可耕种作物的轮作，在三次轮作后，有机碳的百分比在2000年至2009年增加到约1.4%。在70 年间，有机碳在以谷物为主的全耕地轮作中从0.98%下降到0.94%，在根茎作物更多的情况下下降到0.82%。每5年施用38 t ha−1农家肥(FYM)，到20世纪60年代中期停止应用时，有机碳增加0.13个百分点。在2000-2009年间，FYM处理的土壤有机碳含量仍高出0.10%。有机碳含量的变化已用RothC-26.3和选定轮次的估计输入C模拟。在70 年间只保留了很少的有机碳输入，大部分被保留在放牧轮作中，但9 t ha−只保留了189 t ha−1。在其他轮作中，超过98%的有机碳输入损失了。尽管碳的损失很大，但在这种土壤类型上，随着草或草‰三叶草的加入或FYM的应用，有机碳每年增加4 + 是可能的，但仅限于有限的一段时间。SOC的这种增加可能有助于限制大气中二氧化碳的增加。Leys能否将大量大气中的二氧化碳封存在SOM中，并为4‰倡议做出贡献？对70 年中OC的百分比和数量的变化进行了测量和建模，并估计了OC的损失。三年生牧草或牧草 + 三叶草使有机碳增加，但仅达到当时维持的平衡水平。尽管损失巨大，但在4年‰ −1通过种植草或草 + 三叶草来封存CO2-C是可能的。
The sequestration in soil of organic carbon (SOC) derived from atmospheric carbon dioxide (CO2) by replacing arable crops with leys, has been measured over 70 years on a sandy loam soil. The experiment was designed initially to test the effect of leys on the yields of arable crops. A 3‐year grazed grass with clover (grass + clover) ley in a 5‐year rotation with arable crops increased percentage organic carbon (%OC) in the top 25 cm of the soil from 0.98 to 1.23 in 28 years, but with little further increase during the next 40 years with all‐grass leys given fertilizer nitrogen (N). In this second period, OC inputs were balanced by losses, suggesting that about 1.3% OC might be near the equilibrium content for this rotation. Including 3‐year lucerne (Medicago sativa) leys had little effect on %OC over 28 years, but after changing to grass + clover leys, %OC increased to 1.24 during the next 40 years. Eight‐year leys (all grass with N or grass + clover) in 10‐year rotations with arable crops were started in the 1970s, and after three rotations %OC had increased to ca. 1.40 in 2000–2009. Over 70 years, %OC declined from 0.98 to 0.94 in an all‐arable rotation with mainly cereals and to 0.82 with more root crops. Applications of 38 t ha−1 farmyard manure (FYM) every fifth year increased %OC by 0.13% by the mid‐1960s when applications ceased. Soil treated with FYM still contained 0.10% more OC in 2000–2009. Changes in the amount of OC have been modelled with RothC‐26.3 and estimated inputs of C for selected rotations. Little of the OC input during the 70 years has been retained; most was retained in the grazed ley rotation, but 9 t ha−1 only of a total input of 189 t ha−1. In other rotations more than 98% of the total OC input was lost. Despite large losses of C, annual increases in OC of 4‰ are possible on this soil type with the inclusion of grass or grass + clover leys or the application of FYM, but only for a limited period. Such increases in SOC might help to limit increases in atmospheric CO2. Can leys sequester significant amounts of atmospheric CO 2 in SOM and contribute to the 4‰ initiative? Changes in the percentage and amount of OC were measured and modelled over 70 years and OC losses estimated. Three‐year grass or grass + clover leys increased %OC, but only to an equilibrium level that was then maintained. Despite large losses, sequestering CO 2‐C at 4‰ year−1 by growing grass or grass + clover leys is possible.