Crop diversification increases soil extracellular enzyme activities under no tillage: A global meta-analysis

Conservation agriculture with three management principles has been widely adopted to alleviate the current global agricultural soils facing threats such as soil erosion and nutrient loss. However, unclear understanding of rational crop rotation and the lack of global quantitative assessment limit our deeper insight into soil nutrient cycling under conservation agriculture. Considering the important role of soil extracellular enzyme activities (EEAs) on soil nutrient cycling, a meta-analysis with 3238 observations was conducted on the effects of no tillage (NT) and legumes incorporation into rotation system (LRS) on soil EEAs. NT significantly increased the activities of C-acquiring, N-acquiring, P-acquiring, and oxidative enzymes by 18.3%, 17.4%, 7.1%, and 14.0%, respectively, while LRS significantly increased only P-acquiring enzymes. The combination of NT and legume cultivation had no significant effect on EEAs. In contrast, crop diversity had a positive effect on the NT-induced increase in EEAs. In addition, the extent of NT-induced changes varied depending on other factors. Through further analysis, we clarified the important factors affecting NT-induced changes in EEAs, such as climatic conditions, soil properties, and agronomic practices at the experimental sites. Overall, our findings provide insights into the understanding of the mechanisms of conservation agriculture impacts on the soil nutrient cycling.     

Reclamation substantially increases soil organic and inorganic carbon stock in riparian floodplains

Journal of Soils and Sediments - In recent decades, riparian floodplains have undergone intensive reclamation worldwide, which has potential to influence soil carbon (C) accumulation. Such...     

The soil skeleton, a forgotten pool of carbon and nitrogen in soil

To evaluate the contribution of rock fragments to the soil's total carbon content, the soil of 26 sites, ranging from the Canadian Arctic to the Jordan desert, was analysed for the content of organic C and total N in both fine earth and skeleton fractions. The soils, uncultivated and cultivated, are derived from 11 parent materials: sandstone, mica-schist, granite, gneiss, basaltic pyroclastites, trachyte, dolomite, beach deposits, clay schist, marl and serpentinite. For each soil horizon the contents of fine earth and skeleton were determined by volume. Both fractions were analysed for bulk density, total and organic C and total N. Our results indicate that rock fragments contain amounts of C and N that depend on the nature of the parent material and on its resistance to the weathering processes. The C and N of both fine earth and skeleton were used to calculate the contents of these elements for three depths. At each depth, the skeleton contributes C and N to the soil depending on its abundance. We conclude that the contribution of the rock fragments to the soil C and N cannot be predicted from the soil taxa, but can from the parent material. Calculations that exclude C and N of the skeleton could lead to errors in the estimates of these two elements in soils.     

沈阳地区河岸植被缓冲带对氮、磷的削减效果研究

为充分了解河岸植被缓冲带对地表径流污染物的去除效果, 本研究选取辽宁省沈阳市两条典型河流——浑河与蒲河为对象, 研究其滨水不同河岸植被缓冲带对地表径流氮、磷污染物的削减效果。结果表明: 在6 种河岸植被带中, 人工林草地对氮的削减效果最好, 对总氮、硝态氮和铵态氮的平均削减率分别为47%、36%和31%; 人工林地对磷的削减效果较好, 平均削减率为74%; 而人工林地对氮以及人工草地对磷的削减效果较差。随长度增加, 河岸植被缓冲带对地表径流污染物的削减效果基本呈增强趋势。以上研究结果说明不同河岸植被缓冲带对地表径流中氮、磷的削减各有优点。在对遭受污染的河流进行生态修复时, 应考虑环境污染特点和地表特征, 以充分发挥河岸植被缓冲带对污染物的削减优势。     

Short-term nitrogen transformation rates in riparian wetland soil determined with nitrogen-15

N transformation rates in soil from a riparian wetland that receives runoff from adjacent pastoral land were investigated in a short-term (250 min), anaerobic laboratory incubation (20°C). A joint ¹⁵N tracing-isotope dilution technique was employed that used paired incubations of labelled (99 atom % ¹⁵N) NO₃^–-unlabelled NH₄⁺ and unlabelled NO₃^–-labelled (99 atom % ¹⁵N) NH₄⁺ at three N input levels (0.4, 4 and 24 g N g^–1 soil). At each N input level NO₃^– and NH₄⁺ were added in equal proportions (0.2, 2 and 12 g N g^–1 soil). Soil and gas samples were analysed after 10, 70 and 250 min, and the fate of ¹⁵N and N transformation rates were determined for each time period; 0–10 min (phase 1), 10–70 min (phase 2) and 70–250 min (phase 3). N transformation rates for all processes except gross NH₄⁺ mineralisation were very high during phase 1. Processes favoured by aerobic conditions, NO₃^– immobilisation (0–17% NO₃^– removal, 0–8.2 g N g^–1 soil h^–1), autotrophic nitrification (~2% NH₄⁺ removal, 0.58–0.88 g N g^–1 soil h^–1) and heterotrophic nitrification (11–35 g N g^–1 soil h^–1) increased with increased N input while the anaerobic dissimilatory NO₃^– reduction to NH₄⁺ process (1–6% NO₃^– removal, 0.48–0.62 g N g^–1 soil h^–1) decreased, presumably due to the oxidising effect of higher NO₃^– inputs. Denitrification (8–78% NO₃^– removal, 3.8–9.6 g N g^–1 soil h^–1) exhibited no clear trend related to N input levels. NH₄⁺ immobilisation (39–72% NH₄⁺ removal, 15–19 g N g^–1 soil h^–1) was higher than NO₃^– immobilisation. Gross NH₄⁺ mineralisation (0.27–0.80 g N g^–1 soil h^–1) was the only process not detected in phase 1 and one of few processes measurable in phases 2 or 3.     

A global synthesis reveals more response sensitivity of soil carbon flux than pool to warming

Journal of Soils and Sediments - Climate change continues to garner attention in the public sphere. Most recognize its potential to affect global carbon (C) dynamics in the biosphere. Many posit...     

外源氮添加对土壤微生物残体积累动态的影响－基于Meta分析

微生物残体是土壤有机碳库的重要贡献者。为明确外源氮添加对土壤微生物残体积累动态的影响,本文收集整理了1980—2020年已发表的文献,共选取122组试验观测数据,利用整合分析方法（Meta-analysis）,以微生物残体标识物－氨基糖为目标组分,定量分析了不同种类和数量的外源氮添加对土壤中微生物来源细胞残体积累数量和组成比例的影响,并系统解析其主要影响因素。结果表明:外源氮添加（0 ~ 6000 kg hm?1）对微生物细胞残体的积累有显著的促进作用,并能引起土壤中真菌和细菌来源细胞残体相对比例发生明显变化。与不加氮对照相比,氮添加使土壤氨基糖总量增加27%,其中氨基葡萄糖、氨基半乳糖和胞壁酸含量分别增加22.5%、29.8%和19.0%。同时,不同种类外源氮素添加对氨基糖积累特征的影响也有所不同,表现为有机氮（如动物厩肥）比无机氮添加对氨基糖积累的促进作用更大。此外,氮添加对氨基糖的影响程度还与土壤自身的碳氮比、土地利用类型和自然降雨量等环境因子密切相关。其中是否添加碳源对微生物残体的响应有较大影响,表现为:无碳源添加会降低土壤氨基糖葡萄糖和胞壁酸对氮添加的响应,削弱了微生物残体对土壤有机质的贡献比例;而氮源同时配合碳源添加条件下,土壤氨基糖积累量显著高于单一氮源添加的处理,说明氮添加对微生物残体积累的影响存在着碳氮耦合效应。     

小麦苗期施入氮肥在土壤不同氮库的分配和去向

应用盆栽试验和15N标记技术研究了小麦苗期施入N肥后土壤不同N库的动态。结果表明 ,施肥后 28d ,作物所吸收的土壤N占总吸N量的 58.1% ,吸收的肥料N占 41.9%。作物对肥料N的利用率达到 55.3% ,N肥在土壤中的残留率为 24.3% ,损失率为 20.4%。施肥后短期以NH4+-4 N存在的肥料N占施N量的 50.5% ,随着硝化作用的进行和作物的吸收 ,土壤中的NH4+-N显著下降。NO3--N在第 7d达到高峰 ,表现为先升高后降低的趋势 ,说明施肥后在 7d以前有强烈的硝化作用发生。施肥后 2d ,以固定态铵存在的肥料N占 33.7% ,至 28d ,仅占施入N量的 2.4% ,说明前期固定的铵在作物生长后期又重新释放出来供作物吸收。在施肥后第 7d ,肥料N以微生物N存在的量占施肥量的 15.2% ;至 28d来自肥料N的微生物N也几乎被耗竭 ,仅占施N量的 2.4%。随作物生长 ,肥料N在各个土壤N库中的数量均显著下降。在其它N库几乎被耗竭的情况下 ,至施肥后 28d主要以有机N的形式残留。在不种作物的条件下 ,土壤N素的矿化量很低 ,作物的吸收作用导致土壤有机N库不断矿化 ,施入N肥后 ,土壤N素的矿化量增加 ,表现为明显的正激发效应     

河滨缓冲带植物根系和根际微生物特征及其对农业面源污染物去除效果

对河滨缓冲带常见的3种水生植物根系形态特点、活力特征及其土壤微生物群落多样性进行了研究,并对其农业面源污染物的去除效果进行了调查。结果表明,3种水生植物根系形态和活力特征具有显著差异。根系活力表现为水生鸢尾菖蒲千屈菜,与根尖数呈显著相关。同时,3种水生植物具有显著的根际效益,根际土壤微生物生物量显著高于非根际土壤;根际土壤微生物群落数量为细菌放线菌真菌;土壤微生物群落多样性指数为水生鸢尾菖蒲千屈菜,这与3种水生植物根系活力特征表现一致。3种水生植物河滨缓冲区对农业面源污染物TN、TP和CODCr的去除效果表现为水生鸢尾菖蒲千屈菜。说明不同水生植物根系结构导致根系活力不同,由此引起的土壤微生物群落多样性差异对水生植物农业面源污染物去除效果有一定影响。     

Nutrient addition and warming alter the soil phosphorus cycle in grasslands: A global meta-analysis

Journal of Soils and Sediments - Grasslands are the most extensive vegetation type in the terrestrial ecosystem and have an important role in the soil phosphorus (P) cycle. Many nutrient addition...     

岩质边坡绿化过程中人工土壤的重建

在探讨岩质边坡绿化过程中人工土壤的性质及其在土壤分类中定位的基础上,总结目前国内高陡岩质边坡生态复绿中比较常见的厚层基材型和植被混凝土型等人工土壤配置模式的优缺点,以及当前人工土壤重建的主要方法和存在问题,阐述了人工土壤重建中团粒性、保水性和保肥性等农业技术特征以及依附性和稳定性等工程技术特性的构建要点,并对岩质边坡绿化过程中人工土壤的重建进行了展望.     

华北平原不同种植制度对粮食作物氮素利用和土壤氮库的影响

冬小麦-夏玉米一年两熟是华北平原粮食作物的主要种植制度,存在氮肥利用率低、土壤氮素过量累积问题。为探索华北平原氮素高效利用的适宜种植制度,采用15N示踪技术,基于3 a田间定位试验,对一年两熟冬小麦-夏玉米的常规水氮和优化水氮、两年三熟冬小麦-夏玉米-春玉米与冬小麦-夏大豆-春玉米及一年一熟春玉米3种种植制度的作物产量、15N利用率、氮素去向和土壤氮库表观平衡进行研究。结果表明,两年三熟的冬小麦-夏玉米-春玉米产量为32 248.52 kg/hm2,分别比一年两熟和一年一熟提高22.16%和52.88%;15N利用率为33.36%,比一年一熟提高26.12%。3种种植制度的氮肥去向最高为土壤残留,其次为作物吸收和损失,两年三熟冬小麦-夏玉米-春玉米的作物吸氮量最高为151.82 kg/hm2,土壤氮库表观盈余量为21.22 kg/hm2,显著低于其他种植制度。综合分析,冬小麦-夏玉米-春玉米两年三熟在稳产高产和提高氮素利用率上具有可持续的潜力,是华北平原未来较为理想的种植制度。     

太湖地区黄泥土表层氮库变化与水稻产量间的关系研究

24年田间定位试验研究表明,长期不施肥处理和化肥PK配施处理土壤表层N呈下降趋势,而施入化肥N处理(包括化肥N、化肥NP配施、化肥NK配施、化肥NPK配施处理)N增加较缓慢,有机与无机肥结合处理土壤表层N增加迅速。以长期不施肥为对照,长期有机肥 NPK处理水稻增产最多,达35.94%。随着N肥的逐年施入,土壤表层全N含量与产量间由显著正相关关系变为相关性不显著。     

Effects of submergence frequency on soil C:N:P ecological stoichiometry in riparian zones of Hulunbuir steppe

Purpose

Hulunbuir steppe has flat terrain and wide riparian zone of rivers and lakes on it. Owing to climate change, these riparian zones are often submerged or dried. This not only results in the instability of biodiversity in these regions but also affects the soil biogeochemical cycles. Soil C:N:P ecological stoichiometry plays a vital role in predicting and understanding the balance of multiple chemicals in ecological interactions. However, few studies have examined the soil C:N:P ecological stoichiometry in riparian zones of Hulunbuir steppe under different submergence states. Our objectives were to explore whether submergence frequencies impact soil C:N:P stoichiometry and identify the key factors.

Materials and methods

Four study sites were selected along the Hui river in Hulunbuir steppe, and three plots of different submergence frequencies, high (HF-sub, 5 to 7 times per year), moderate (MF-sub, 2 to 3 times per year), and low (LF-sub, unflooded or flooded once per year), were selected for each study site. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), their ecological stoichiometric ratios (soil C:N, N:P, and C:P), soil ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^?-N), available phosphorus (AP), soil pH, electrical conductivity (EC), soil moisture content (SMC), soil bulk density (SBD), porosity, and hardness were measured and analyzed.

Results and discussion

The results indicated that soil C:N:P ecological stoichiometry was notably affected by submergence frequency across the four study sites (P?<?0.05). SOC, TN, TP, and their stoichiometric ratios changed regularly with the submergence frequency change, whereas their trends were inconsistent at different drainage basins. Soil C:N decreased with the decrease in submergence frequency but kept in a narrow scope, whereas the N:P and C:P were changed greatly under different submergence frequencies. Further analysis found that these significant variations in N:P and C:P were mainly due to the changes in soil TP which suggested there might be a P limitation in the riparian zones. The results of redundancy analysis (RDA) and path analysis indicated that soil AP and NO₃^?-N were the key indirect factors affecting soil C:N:P ecological stoichiometry under different submergence frequencies, and SMC was an indirect factor.

Conclusions

We demonstrated that the soil C:N:P ecological stoichiometry was significantly affected by the submergence frequency in the riparian zones of Hulunbuir steppe. Soil N:P and C:P were more susceptible to change than C:N under different submergence frequencies. If the contents of soil AP and NO₃^?-N were appropriate, soil C:N:P ecological stoichiometry will be more beneficial to regulating the cycle and balance of soil nutrient elements in the riparian zones, which can promote the riparian zones to provide better ecological functions.

     

Effects of different continuous fertilizer managements on soil total nitrogen stocks in China: A meta-analysis

Soil total nitrogen is critical for crop productivity and related to agricultural managements. However, the effects of different fertilizer applications on soil total nitrogen storage are not well understood. To quantify soil total nitrogen storage under different fertilizer management practices and explore the effects of climate, soil texture, experimental duration, and cropping system on soil total nitrogen storage in China, we conducted a meta-analysis of 67 fertilizer management strategies from experiments conducted over a period of at least three years. This meta-analysis included 854 observations of changes in soil total nitrogen stock(TNS) under no fertilizer application(control, CK), chemical fertilization with nitrogen, phosphorus, and potassium(CF), CF plus straw retention(CFS), and CF plus manure addition(CFM) relative to initial soil TNS. The CFM and CFS treatments increased soil TNS, and the CFM treatments increased soil C/N ratio the most. The longer the experimental duration, the greater the increase in soil TNS in the CF, CFS, and CFM treatments.Soil texture and crop type significantly affected the changes in soil TNS. The experimental duration, initial soil TNS, soil C/N ratio, and cropping system had significant linear correlations with the change in soil TNS. Temperature and precipitation were not correlated with soil TNS. Results of random forest modeling indicated that the most important factor affecting changes in soil TNS was experimental duration(positive correlation), followed by initial soil TNS(negative correlation). The CFM treatments had the largest increase in soil TNS under various conditions. We recommend promoting CFM to improve soil fertility in farmlands globally.     

干湿交替下氮肥施用对土壤有机氮库转化的影响

水旱轮作条件下频繁的干湿交替显著影响了土壤氮素转化。为了明确干湿交替下氮肥施用对土壤有机氮库转化的影响,采用室内培养的方法,研究模拟淹水、干旱、水改旱、旱改水条件下,氮肥施用对土壤有机氮库动态变化的影响,以期为水旱轮作体系氮肥合理施用提供理论支撑。结果表明,氮肥施用能够显著提高土壤酸解态总氮含量,不同水分条件下土壤酸解态总氮含量无明显差异,但对酸解态总氮各组分含量产生显著影响。模拟淹水条件下酸解态氮主要以酸解铵态氮和未知态氮形式存在,分配比例分别为40.2%和33.7%,而模拟旱地条件下主要以氨基酸态氮和未知态氮形式存在,分配比例占到了40.7%和31.5%。经水分条件转换后,各种水分条件下土壤酸解铵态氮和氨基酸态氮含量均出现降低,水改旱条件下土壤氨基糖态氮含量显著提高,而旱改水条件下未知态氮含量显著提高。在整个培养阶段,土壤铵态氮与酸解铵态氮存在极显著的正相关,具有相似的变化规律。综上所述,氮肥施用到水田初期有利于提高土壤铵态氮和酸解铵态氮含量,随后这两种氮组分逐渐分解转化,而氨基糖态氮含量逐渐提升,氨基糖态氮是水旱轮作体系中肥料氮素的重要“中     

微立地因子植被恢复法在汶川地震植被重建中的应用

“5·12”汶川大地震造成的滑坡、泥石流、崩塌等地质次生灾害使当地的植被毁坏严重,微立地因子植被恢复法适用于地震灾区复杂的立地条件植被重建。在研究灾区植被破坏类型的基础上,将损毁植被的坡面划分为岩质边坡、土质边坡、土石边坡3种类型,并对不同坡面进行微立地因子类型划分,针对不同立地条件选择适宜植被恢复技术,促使灾区尽快植被重建,并为微立地因子植被恢复法的完善提供重要依据。     

Excessive nitrogen application decreases grain yield and increases nitrogen loss in a wheat–soil system

Abstract

Excessive use of nitrogen (N) fertilizers in wheat fields has led to elevated NO₃-N concentrations in groundwater and reduced N use efficiency. Three-year field and ¹⁵N tracing experiments were conducted to investigate the effects of N application rates on N uptake from basal and topdressing ¹⁵N, N use efficiency, and grain yield in winter wheat plants; and determine the dynamics of N derived from both basal and topdressing ¹⁵N in soil in high-yielding fields. The results showed that 69.5–84.5% of N accumulated in wheat plants derived from soil, while 6.0–12.5%and 9.2–18.1% derived from basal ¹⁵N and top ¹⁵N fertilizer, respectively. The basal N fertilizer recovery averaged 33.9% in plants, residual averaged 59.2% in 0–200 cm depth soil; the topdressing N fertilizer recovery averaged 50.5% in plants, residual averaged 48.2% in 0–200 cm soil. More top ¹⁵N was accumulated in plants and more remained in 0–100 cm soil rather than in 100–200 cm soil at maturity, compared with the basal ¹⁵N. However, during the period from pre-sowing to pre-wintering, the soil nitrate moved down to deeper layers, and most accumulated in the layers below 140 cm. With an increase of N fertilizer rate, the proportion of the N derived from soil in plants decreased, but that derived from basal and topdressing fertilizer increased; the proportion of basal and top ¹⁵N recovery in plants decreased, and that of residual in soil increased. A moderate application rate of 96–168 kg N ha^?1 led to increases in nitrate content in 0–60 cm soil layer, N uptake amount, grain yield and apparent recovery fraction of applied fertilizer N in wheat. Applying above 240 kg N ha^?1 promoted the downward movement of basal and top ¹⁵N and soil nitrate, but had no significant effect on N uptake amount; the excessive N application also obviously decreased the grain yield, N uptake efficiency, apparent recovery fraction of applied fertilizer N, physiological efficiency and internal N use efficiency. It is suggested that the appropriate application rate of nitrogen on a high-yielding wheat field was 96–168 kg N ha^?1.     

腾格里沙漠植被重建对土壤呼吸的影响

植被重建是防止和控制沙漠化的有效措施之一。为探讨腾格里沙漠植被重建对土壤呼吸的影响,利用Li-6400-09土壤呼吸室于2007年观测了1989年建立的植被重建区和流沙区土壤呼吸差异,并采用根系隔离法区分了植被重建区的土壤基础呼吸和根际呼吸。结果表明,植被重建18a显著影响了该区土壤CO2的释放过程,总土壤呼吸速率由流沙区的CO20.107±0.008μmolm-2s-1显著增加到植被区CO20.483±0.033μmolm-2s-1,而且出现了较为明显的季节波动。植被重建不但导致根际呼吸速率增加,而且影响了土壤基础呼吸速率。此外,植被重建区灌木的缀块状分布格局和养分的空间异质性导致了土壤呼吸的空间差异。