冬季咸水结冰灌溉对河套重盐碱地改良效果研究

采用田间大区试验,连续3年在河套重盐碱区开展了冬季咸水结冰灌溉试验研究,设置冬季咸水结冰灌溉(FSWI)和无灌溉对照(CK)两个处理,其中FSWI处理的灌水量为180 mm,矿化度为6.79～7.97 g·L~(–1),种植作物为青贮玉米,以分析不同处理下土壤水盐和钠吸附比(SAR)的周年动态以及对作物生长的影响,探究冬季咸水结冰灌溉对河套重盐碱地的改良效果。结果表明:与CK相比,FSWI处理显著改变了春季土壤水盐和SAR动态。0～20 cm土层,春季FSWI处理的土壤含水量显著高于CK处理,玉米苗期, FSWI处理的土壤含水量平均为24.3%,显著高于CK的21.6%; FSWI处理的春季土壤含盐量和SAR显著低于CK处理,其中, FSWI处理的土壤含盐量由灌溉前的33.86 g·kg~(–1)降低至玉米苗期的5 g·kg~(–1)以下,而CK处理土壤含盐量逐渐升高至玉米苗期的34.2 g·kg~(–1); FSWI处理土壤SAR由灌溉前的21.9降低至玉米苗期的9.86, CK土壤SAR则逐渐升高至玉米苗期的25.00。后续地膜覆盖和夏季降雨使FSWI处理的土壤含水量维持在23.0%以上,土壤含盐量保持在5 g·kg~(–1)以下,土壤SAR保持在9左右。20～40 cm土层与0～20 cm土层的土壤水盐和SAR变化趋势与表层一致,但没有表层变化剧烈。此外,随着灌溉年限的延长,同时期土壤含盐量和SAR呈逐年降低的趋势。FSWI处理玉米出苗率在70%以上,干物质产量为9～12t·hm~(–2),而CK处理由于土壤含水量较低(21.0%),并且土壤含盐量和SAR均较高,造成玉米出苗率极低,进而导致绝收。因此冬季咸水结冰灌溉改变了土壤水盐动态过程,变春季积盐为脱盐,显著降低了土壤SAR,并补充了土壤水分,保证了饲用玉米的正常种植和生长,这为该地区盐碱地改良和饲料作物种植提供了技术支持。     

Effect of labile and recalcitrant carbon on heterotrophic nitrification in a subtropical forest soil

Carbon (C) is an important factor controlling heterotrophic nitrification in soil, but the effect of individual C components (e.g., labile and recalcitrant C) is largely unclear. We carried out a C amendment experiment in which either labile C (glucose) or a recalcitrant C (cellulose and biochar) was added to a subtropical forest soil. A ¹⁵N-, ¹³C-tracing and MiSeq sequencing study was performed to investigate soil gross heterotrophic nitrification rates, carbon utilization for soil respiration and microbial biomass production and microbial composition, respectively. After 2 days, results showed a significant increase of gross heterotrophic nitrification rate in glucose (GLU) (on average 3.34 mg N kg⁻¹ day⁻¹), cellulose (CEL) (on average 0.21 mg N kg⁻¹ day⁻¹) and biochar (BIO) (on average 0.13 mg N kg⁻¹ day⁻¹) amendment in comparison with the unamended soil (CK) (on average 0.01 mg N kg⁻¹ day⁻¹; p < 0.05). The contribution of heterotrophic nitrification to total soil nitrification was significantly larger in GLU (average 85.86%), CEL (average 98.52%) and BIO (average 81.25%) treatments compared with CK (average 33.33%; p < 0.01). After 2-month amendment, the gross rates remarkably decreased in GLU (average 0.02 mg N kg⁻¹ day⁻¹), and the contribution to total nitrification (average 8.73%) were significantly lower than that in CK (p < 0.05). A decrease in the proportion of heterotrophic nitrification to total nitrification in soil was also observed in CEL (average 38.40%) and BIO (6.74%) treatments. Nevertheless, BIO amendment (compared to CK, GLU and CEL) showed the highest gross heterotrophic nitrification rate, accompanied by a notably higher abundance of specific heterotrophic nitrifiers, i.e. Trichoderma, Aspergillus and Penicillium. These results point to a stimulatory effect of C addition on soil heterotrophic nitrification in the short term, while the stimulatory impact of C amendment diminishes with the decline in easily available C. In addition, a shift of the microbial composition in the long term can possibly be sustained for longer if additional recalcitrant C is available to heterotrophic nitrifiers. The dynamic response of heterotrophic nitrification to labile and recalcitrant C in this study offered an explanation for the positive effect of plantation and plant root exudation on the process.     

Coupled effects of biochar use and farming practice on physical properties of a salt-affected soil with wheat–maize rotation

Purpose

Being carbon-rich and porous, biochar has the potential to improve soil physical properties, so does conventional farming practice. Here, a field trial was conducted to investigate the combined effects of biochar use and farming practice on the physical properties of a salt-affected compact soil for wheat–maize rotation in the Yellow River Delta region.

Materials and methods

Salix fragilis L. was used as feedstock to produce biochar in the field via aerobic carbonization at an average temperature of 502 °C, terminated by a water mist spray, for use as a soil amendment at 0, 1, 2, and 4 g kg^?1 doses (CK, T1, T2, and T3, respectively). Farming practices included rotary tillage/straw returning for wheat sowing, spring irrigation, no-tillage seeding of maize, and autumn irrigation. Both cutting ring and composite samples of the soil were collected at four stages of wheat–maize rotation (22, 238, 321, and 382 d after the benchmark date of land preparation for wheat sowing) for the determination of soil properties by established methods.

Results and discussion

Rotary tillage/straw returning reduced soil bulk density (BD) from 1.48 to 1.27 g cm^?3 (CK) and 1.14 g cm^?3 (T3) and increased saturated hydraulic conductivity (Ks) from 0.05?×?10^?5 to 0.75?× 10^?5 cm s^?1 (CK) and 1.25?× 10^?5 cm s^?1 (T3). This tillage effect on BD and Ks gradually disappeared due to the disturbance from the subsequent farming practice. Biochar use lessened the disturbance. At maize harvest, BD was 1.47 (CK) vs. 1.34 g cm^?3 (T3), and Ks was 0.06?×?10^?5 (CK) vs. 0.28?×?10^?5 cm s^?1(T3); in comparison with CK, T3 increased Na⁺ leaching by 65%, Cl^? leaching by 98%, organic carbon content by 40.3%, and water-stable aggregates (0.25–2 mm) by 38%, indicating an improvement in soil properties.

Conclusions

Biochar use and rotary tillage improved soil physical properties (BD, Ks) and favored soil aeration, water filtration, and salt leaching, which further helped the accumulation of soil organic carbon, the formation of water-stable aggregates, and the amelioration of salt-affected compact soil.

     

Spatial distribution of soil salinity and potential implications for soil management in the Manas River watershed,China

Understanding the watershed-scale spatial distribution of soil salinity and its compositions is important for soil management. Here, we present the first study on the Manas River watershed in northwest China. In this study, we took soil samples in upper 20 cm of soil from 186 locations across the watershed and measured total salt concentration (TSC), salt ion composition and soil particle size distribution (PSD). We found that on average topsoil TSC tended to increase, from 3.55 g kg⁻¹ in upstream regions to 19.40 g kg⁻¹ in downstream regions. The stoichiometric analysis showed that the equivalence ratio of soil Cl^- to SO₄²⁻ increased from 0.53 in upstream regions to 2.12 in midstream regions, and further to 3.76 in downstream regions; thus, the soil types were classified into chloride–sulfate, sulfate–chloride and chloride soils types, respectively. Additionally, proportions of small (<2 μm in diameter) and large (>2,000 μm) soil particles increased, while that of medium sizes (2–50 μm) decreased from upstream to downstream, with an increasing coefficient of variance (CV) in PSD. Taken together, watershed-scale topsoil salinity may be horizontally characterized by increased TSC and Na⁺ & Cl⁻ proportions, greater equivalence ratio of Cl⁻ vs. SO₄²⁻ and more balanced distribution of PSD along with surface water flow. Results demonstrated that soil salinity and its ions compositions showed a great variation across the watershed scale, suggesting that soil management may consider the spatial heterogeneity of saline–alkaline soil types, and our results provided scientific guidance for local soil management and restoration.     

The effect of biochar addition on N2O and CO2 emissions from a sandy loam soil – The role of soil aeration

Biochar application to soil has significant potential as a climate change mitigation strategy, due to its recalcitrant C content and observed effect to suppress soil greenhouse gas emissions such as nitrous oxide (N₂O). Increased soil aeration following biochar amendment may contribute to this suppression.Soil cores from a Miscanthus X. giganteus plantation were amended with hardwood biochar at a rate of 2% dry soil weight (22 t ha⁻¹). The cores were incubated at three different temperatures (4, 10 and 16 °C) for 126 days, maintained field moist and half subjected to periodic wetting events. Cumulative N₂O production was consistently suppressed by at least 49% with biochar amendment within 48 h of wetting at 10 and 16 °C. We concluded that hardwood biochar suppressed soil N₂O emissions following wetting at a range of field-relevant temperatures over four months. We hypothesised that this was due to biochar increasing soil aeration at relatively high moisture contents by increasing the water holding capacity (WHC) of the soil; however, this hypothesis was rejected.We found that 5% and 10% biochar amendment increased soil WHC. Also, 10% biochar amendment decreased bulk density of the soil. Sealed incubations were performed with biochar added at 0–10 % of dry soil weight and wetted to a uniform 87% WHC (78% WFPS). Cumulative N₂O production within 60 h of wetting was 19, 19, 73 and 98% lower than the biochar-free control in the 1, 2, 5 and 10% biochar treatments respectively. We conclude that high levels of biochar amendment may change soil physical properties, but that the enhancement of soil aeration by biochar incorporation makes only a minimal contribution to the suppression of N₂O emissions from a sandy loam soil. We suggest that microbial or physical immobilisation of NO₃⁻ in soil following biochar addition may significantly contribute to the suppression of soil N₂O emissions.     

不同生物炭对南疆盐渍土盐分离子淋洗效果的影响

为探究不同生物炭添加对盐渍化土壤盐分及离子淋洗效果的影响。采用室内土柱模拟试验,在土壤表层(0-10 cm)添加比例为0.5%的猪粪(PMB)、棉秆(CSB)和玉米秸秆(MSB)生物炭,淋洗过程分为急降(P1)、缓降(P2)和稳定(P3)3个阶段,通过测定淋洗速率、流量、累积浸出阴阳离子浓度、土壤剖面含水率和土壤剩余可溶性离子的含量来探究不同生物炭对南疆盐渍土盐分离子的淋洗效果。结果表明:与未添加生物炭处理(CK)相比,生物炭的施用能提高各阶段淋洗液的流量和淋洗速率,在电导率快速下降阶段CSB处理流量提高20%,PMB处理淋洗速率提高29%,MSB处理最先使EC值降低到5 mS/cm,但对离子的去除能力提升较小。生物炭的施用对各阶段离子淋出先后顺序有一定影响,即促进Ca²⁺、Na⁺、SO₄^2-和Cl^-淋出,抑制K⁺淋出。淋洗结束时,生物炭均能显著降低土壤残余含盐量。CSB处理可提高表层土壤保水能力,使得钠吸附比(SAR)始终保持较低水平且对土壤中残余阴离子洗脱效果最好。表明CSB处理是一种非常有潜力的土壤改良剂。研究结果可为南疆盐渍化土壤改良提供理论参考。     

Biochar amendment of chromium-polluted paddy soil suppresses greenhouse gas emissions and decreases chromium uptake by rice grain

Purpose

Soil chromium (Cr) pollution has received substantial attention owing to related food chain health risks and possible promotion of greenhouse gas (GHG) emissions. The aim of the present study was to develop a promising remediation technology to alleviate Cr bioavailability and decrease GHG emissions in Cr-polluted paddy soil.

Materials and methods

We investigated the potential role of biochar amendment in decreasing soil CO₂, CH₄, and N₂O emissions, as well in reducing Cr uptake by rice grains at application rates of 0 t ha^?1 (CK), 20 t ha^?1 (BC20), and 40 t ha^?1 (BC40) in Cr-polluted paddy soil in southeastern China. In addition, the soil aggregate size distribution, soil organic carbon (SOC) concentration of soil aggregates, soil available Cr concentration, and rice yield were analyzed after harvesting.

Results and discussion

Biochar amendment significantly reduced CO₂, CH₄, and N₂O emission fluxes. Compared to CK, total C emissions in the BC20 and BC40 treatments decreased by 9.94% and 17.13% for CO₂-C, by 30.46% and 37.10% for CH₄-C, and by 34.24% and 37.49% for N₂O-N, respectively. Biochar amendment increased the proportion of both the 2000–200 μm and 200–20 μm size fractions in the soil aggregate distribution. Accordingly, the organic carbon concentration of these fractions increased, which increased the total SOC. Moreover, biochar amendment significantly decreased soil available Cr concentration and total Cr content of the rice grains by 33.6% and 14.81% in BC20 and 48.1% and 33.33% in BC40, respectively. Rice yield did not differ significantly between biochar amendment treatment and that of CK.

Conclusions

Biochar application reduced GHG emissions in paddy soil, which was attributed to its comprehensive effect on the soil properties, soil microbial community, and soil aggregates, as well as on the mobility of Cr. Overall, the present study demonstrates that biochar has a great potential to enhance soil carbon sequestration while reducing Cr accumulation in rice grains from Cr-polluted rice paddies.

     

Long-term effects of land use and fertiliser treatments on sulphur transformations in soils from the Broadbalk experiment

Sulphur transformations were monitored in a unique set of arable, grassland and woodland soils from the Broadbalk Classical Experiment, which started in 1843. In an open incubation experiment with periodic leaching, 14–35 mg SO₄²⁻-S kg⁻¹ was mineralised in 28 weeks at 25°C, equivalent to 4.4–8.3% soil organic S. Cumulative amounts of S mineralised increased linearly during the 28 weeks, indicating constant rates of mineralisation. The rate of mineralisation was the greatest in the woodland soil (170 μg SO₄-S kg⁻¹ day⁻¹), followed by the grassland (120 μg SO₄-S kg⁻¹ day⁻¹) and the arable soil from the farmyard manure (FYM) plot (110 μg SO₄-S kg⁻¹ day⁻¹). Three soils from arable plots receiving different inorganic fertiliser treatments but no FYM had similar rates of S mineralisation (~70 μg SO₄-S kg⁻¹ day⁻¹). In an incubation experiment with ³⁵SO₄²⁻, addition of glucose greatly enhanced S immobilisation. In 132 days, the woodland and grassland soils immobilised more S than the arable soils, with or without glucose amendment. Immobilisation and mineralisation of S occurred concurrently, and both were stimulated by glucose addition. The results show that S mineralisation and immobilisation were influenced strongly by the type of land-use and long-term organic manuring, whereas annual application of sulphate-containing fertilisers for over 150 years had few effects on short-term S transformations.     

咸水结冰灌溉改良盐碱地的研究进展及展望

冬季咸水结冰灌溉技术是滨海区高矿化度咸水利用和盐碱地改良的有效手段,该项技术依据咸水结冰融化过程中咸淡水分离的基本原理,基于区域气候特点、土壤水盐运移规律以及作物生长发育规律,在冬季抽提当地高矿化度地下咸水对盐碱地进行灌溉,并在冬季低温作用下迅速冻结成咸水冰,春季咸水冰层融化过程中,咸淡水分离入渗,其中先融化的高矿度咸水先入渗,而后融化出的低矿化度微咸水和淡水的入渗对土壤盐分具有较好的淋洗作用,以上过程实现了春季土壤返盐期的土壤脱盐,结合春季地表覆盖抑盐措施和夏季降雨淋盐,土壤的低盐条件得到保持,保证了作物和植物整个生长期的正常生长。该项技术改变了滨海盐碱区土壤水盐运移特征,使春季土壤积盐期变为脱盐期,咸水结冰灌溉后,春季耕层土壤盐分由最初的12g×kg~(-1)迅速降低至4 g×kg~(-1)以下,脱盐率达到66%以上,实现了棉花、油葵、甜菜等作物在滨海重盐碱地中的种植,提高了柽柳、枸杞、白蜡等盐生植物和耐盐植物的扦插移栽成活率,咸水结冰灌溉当年便获得了籽棉产量3 t×hm~(-2)、油葵1.5 t×hm~(-2)、甜菜60 t×hm~(-2),以及90%以上的盐生植物和耐盐植物的扦插成活率,促进了滨海盐碱区盐碱地的开发、农业发展和生态环境建设。近年来,通过系统的研究,我们探明了咸水结冰灌溉过程中咸水冻融咸淡水分离规律,明确了咸水结冰灌溉对土壤盐分的淋洗效果,构建了冬季咸水结冰灌溉改良盐碱地技术体系,确立了冬季咸水结冰灌溉的灌溉时间、灌溉水量和水质等指标体系。本文在以上研究基础上,对盐碱地咸水利用的研究进展进行了总结,并对咸水结冰灌溉基本原理、影响因素以及土壤盐分淋洗效果等方面进行了概述,系统分析了冬季咸水结冰灌溉在盐碱地区农业生产、植被恢复以及咸水利用等方面的作用,并就其未来发展趋势进行了展望。     

Efficiency of KOH-modified rice straw-derived biochar for reducing cadmium mobility, bioaccessibility and bioavailability risk index in red soil

Cadmium (Cd) pollution in agricultural soils has exerted a serious threat due to continuous application of pesticides, fertilizers, and wastewater irrigation. The present study aimed to test the efficiency of KOH-modified and non-modified rice straw-derived biochar (KBC and BC, respectively) for reducing Cd solubility and bioavailability in Cd-contaminated soil. Cadmium-contaminated soil was incubated for 60 d with 15 and 30 g kg^-1 BC and KBC. At the end of incubation, Cd mobility was estimated by the European Community Bureau of Reference sequential extraction and toxicity characteristic leaching procedure (TCLP), while bioavailability was determined using 1 mol L^-1 NH₄NO₃ extraction. The bioavailability risk index and bioaccessibility, assessed by a simple bioaccessibility extraction test, of Cd were used to examine the potential effects of Cd on living organisms. The results indicated that application of both KBC and BC significantly increased soil pH, cation exchange capacity, nutrients, and organic carbon. The soluble fraction of Cd was significantly decreased by 30.3% and 27.4%, respectively, with the addition of KBC and BC at 30 g kg^-1 compared to the control (without biochar addition). Similarly, the bioaccessible Cd was significantly decreased by 32.4% and 25.2%, respectively, with the addition of KBC and BC at 30 g kg^-1 compared to the control. In addition, both KBC and BC significantly reduced Cd leaching in the TCLP and NH₄NO₃-extractable Cd in the amended soil compared to the control. The reduction in Cd solubility and bioaccessibility by KBC and BC may be due to significant increases in soil pH and surface complexation. Overall, KBC at an application rate of 30 g kg^-1 demonstrated positive results as soil amendment for Cd immobilization, and reduced bioaccessible Cd in contaminated soil.     

咸水冻融灌溉对重度盐渍土壤水盐分布的影响

室内咸水冰融化试验设置2个处理:7.5 g L-1咸水冰(SIW(7.5))、15 g L-1咸水冰(SIW(15)),探究了咸水冰融化过程中的水量、水质以及离子组成的变化;土柱模拟试验设置同一灌水量(150mm),4个处理:淡水直接灌溉(FW)、7.5 g L-1咸水直接灌溉(SW)、7.5 g L-1咸水冻融灌溉(SIW(7.5))、15 g L-1咸水冻融灌溉(SIW(15)),对比分析两种灌溉水质(淡水、咸水)和两种灌水方式(直接灌溉、结冰灌溉)对土壤(粉砂壤土)水盐动态的影响。结果表明:咸水冰融化过程中,初期融出水量较大,但含盐量和钠吸附比(SAR)较高,后期融出水量较小,含盐量和SAR很低;融出水的离子含量变化与电导率(EC)变化表现相同的趋势;小于3 g L-1的水的融出率分别是SIW(7.5)=25.46%和SIW(15)=32.78%。FW处理下,土壤中水盐运动持续时间较其他3个处理长,土壤导水率降低最快,灌溉水入渗完成时表层土壤含水量达到33.88%,显著高于其他处理。四种处理下,0~15 cm土层土壤的含盐量平均值分别为FW=2.32 g kg-1、SIW(7.5)=2.80 g kg-1、SIW(15)=3.87 g kg-1、SW=4.31 g kg-1。同等灌水量下,SIW(15)处理下土壤脱盐深度最浅。离子分析表明:FW和SIW(7.5)处理下,0~25 cm土壤的钠吸附比(SAR)下降明显,显著小于SW、SIW(15);然而FW处理下,土壤碱化特征最为明显。综合而言,在淡水资源缺乏而咸水资源相对丰富的地区,中度矿化度咸水结冰融水灌溉可以有效降低根层土壤盐分,满足农业生产的要求。     

Maize straw is more effective than maize straw biochar at improving soil N availability and gross N transformation rate

Soil nitrogen (N) transformation is vital in determining farmland N availability. Although many studies have investigated the effect of biochar on N retention and loss via leaching and gaseous emissions, few have determined the dynamics of gross N transformation during crop growth in long-term biochar-amended soils and compared the effect of the biochar with that of its feedstock. In this study, we conducted a five-time field measurement of soil gross N turnover rates via ¹⁵N isotope pool dilution during maize growth in 2021. Three treatments were employed, including no amendment, biochar and straw applied annually at rates of 2.63 and 7.50 t ha⁻¹, respectively, since 2013. The results showed that biochar did not change the rate of gross N mineralisation when compared with no amendment, but straw increased it by 139% in August, resulting in significantly higher cumulative gross N mineralisation than biochar and no amendment (701 vs 489 and 499 mg kg⁻¹ in 200 d). The inconsistent influence was attributed to the fact that inherent biochar-N was recalcitrant and could not be mineralized like the straw. The gross nitrification rate was decreased by 72.9% and 77.4% by biochar and straw application, respectively, in June relative to no amendment, but then it increased from July to August in the straw treatment as a result of the elevated gross N mineralisation rate. The decreased nitrification in the biochar treatment was an outcome of the synergetic effect of a low ammonium pool (−59.4%) and a high gross ammonium immobilisation rate (+263%), which was likely due to excessive fertilizer N loss and abiotic adsorption to biochar. Meanwhile, biochar amendment inhibited bacterial 16S and fungal ITS genes, as well as ureC and bacterial and archaea-amoA gene copies. In conclusion, straw is more effective than biochar at improving soil N transformation and availability in the long term.     

Nutrient cycling and greenhouse gas emissions from soil amended with biochar-manure mixtures

Integrating biochar into cattle diets has recently emerged as a potential management practice for improving on-farm productivity.Yet,information concerning the cycling of biochar-manure mixtures is scarce.A 70-d incubation experiment was conducted within two surface(0–15 cm)Mollisols with contrasting textures,i.e.,sandy clay loam(Raymond)and clayey(Lethbridge),to evaluate the effects of biochar(3 Mg ha^-1)on cumulative greenhouse gas(GHG)emissions and related fertility attributes in the presence or absence of cattle manure(120 Mg ha^-1).Five treatments were included:i)non-amended soil(control,CK),ii)soil amended with pinewood biochar(B),iii)soil amended with beef cattle manure(M)(manure from cattle on a control diet),iv)soil amended with biochar-manure(BM)(manure from cattle on a control diet,with pinewood biochar added at 20 g kg^-1of diet dry matter),and v)soil amended with B and M at the aforementioned rates(B+M).A total of 40 soil columns were prepared and incubated at 21℃and 60%–80%water-holding capacity.On average,total CO₂fluxes increased by 2.2-and 3.8-fold under manure treatments(i.e.,M,BM,and B+M),within Raymond and Lethbridge soils,respectively,relative to CK and B.Similarly,total CH4 fluxes were the highest(P<0.05)in Raymond soil under B+M and BM relative to CK and B,and in Lethbridge soil under M and BM relative to CK and B.In Lethbridge soil,application of BM increased cumulative N₂O emissions by 1.8-fold relative to CK.After 70-d incubation,amendment with BM increased(P<0.05)PO_4-P and NO_3-N+NH_4-N availability in Raymond and Lethbridge soils compared with B.A similar pattern was observed for water-extractable organic carbon in both soils,with BM augmenting(P<0.05)the occurrence of labile carbon over CK and B.It can be concluded that biochar,manure,and/or biochar-manure have contrasting short-term effects on the biogeochemistry of Mollisols.At relatively low application rates,biochar does not necessarily counterbalance manure-derived inputs.Although BM did not mitigate the flux of GHGs over M,biochar-manure has the potential to recycle soil nutrients in semiarid drylands.     

聚丙烯酰胺改性生物质炭对盐碱化土壤盐分洗脱的影响

为了提升生物质炭对滨海盐碱土壤盐分的洗脱效率,以海兴县盐碱土为研究对象,利用聚丙烯酰胺(PAM)、小麦秸秆生物质炭(BC)、黏土矿物(M)等材料制备聚丙烯酰胺改性生物质炭(PAM-BC),通过室内模拟淋溶试验研究对比不同环境材料对盐碱土盐分的洗脱效果。结果表明,相比于CK处理,PAM、BC和PAM-BC、CaSO₄(CS)处理均显著增加土壤盐分洗脱量,其中PAM-BC处理下增幅最高,达到12.3%。进一步对淋洗液中主要盐分离子分析,添加PAM-BC显著促进土壤Na⁺和Cl^-的洗脱,增幅分别为11.0%～27.3%和17.8%～42.3%。主成分分析表明,PAM-BC增强对主要盐分离子的洗脱效果。土柱淋溶结束后,PAM-BC添加处理土壤全盐量比其他处理显著降低6.0%～16.7%。此外,土壤水分特征曲线表明,添加PAM-BC提升盐碱土壤的保水性。研究结果可为聚丙烯酰胺改性生物质炭应用于滨海盐渍化土壤的降盐改土提供理论依据。     

Long-term effects of bone char and lignocellulosic biochar-based soil amendments on phosphorus adsorption–desorption and crop yield in low-input acidic soils

Although the addition of biochar has been shown to reduce the phosphorus (P) adsorption capacity of soil, quantitative evidence of this has mainly been provided by incubation experiments and it is therefore essential to conduct long-term field trials to draw general conclusions. It is largely unknown whether bone char has a greater effect than lignocellulosic biochar on P adsorption–desorption processes and crop yield. The aim of this study was to determine the long-term (8 years) effect of bone char and biochar on P adsorption–desorption and crop yield in low-input acidic soils. The results showed that bone char decreased the maximum P adsorption capacity (Q_m) by 10% and increased the desorption capacity (D_s) by 150% compared with the control (i.e. without a soil amendment). The desorption ratio was highest for the bone char treatment (10.3%) and three times more than the control. Plant-available P was seven times greater under bone char than the control. There was no variation in adsorption–desorption characteristics, desorption ratio and plant-P available content between bone char and lignocellulosic biochar treatments. The average yield increment following the application of bone char and biochar was 1.7 and 1.4 Mg ha⁻¹ for maize and 1.8 and 1.9 Mg ha⁻¹ for soya bean, respectively. Despite the low application rate (4 t ha⁻¹ year⁻¹), these findings demonstrated that the long-term application of bone char and biochar-based amendments enhanced P availability in low-input cropping systems, mainly by altering the P adsorption and desorption capacity of soils.     

Responses of the soil nematode community to management of hybrid napiergrass: The trade-off between positive and negative effects

An orthogonal experiment (form L₁₆(4⁵)) was used to investigate how the soil nematode community (density, diversity, and faunal structure) and soil health were affected by hybrid napiergrass management. The experiment included four levels of the each of the following main factors: nitrogen fertilization, cutting frequency, cutting intensity, and irrigation. The soil nematode community was affected more by nitrogen fertilization and irrigation than by cutting frequency and cutting intensity. Hybrid napiergrass develops a large root system and the carbon stored in the roots might have buffered any adverse effects of cutting on soil nematodes in the present study. The responses to fertilization indicated that fertilization had both positive and negative effects on the soil community and that the net effect depended on the level of fertilization. Additional water applied in irrigation was detrimental to soil nematode communities in that it might reduce the oxygen content of soil and also increases the potential for the leaching of nutrients from soil. Additionally, we suggest that moderate N fertilization (460 kg ha⁻¹ yr⁻¹), moderate irrigation (one time yr⁻¹ during the dry season), and cutting (three times per year at 20 cm height) will maintain soil health and provide substantial hybrid napiergrass yields.     

Effects of biochar addition on greenhouse gas emissions during freeze–thaw cycles in a black soil region,Northeast China

As global warming intensifies, the soil environment in middle to high latitudes will undergo more extensive and frequent freeze–thaw cycles (FTCs), which will significantly affect the carbon and nitrogen cycles of soil ecosystems and aggravate greenhouse gas (GHG) emissions. Biochar can increase soil organic carbon storage and mitigate climate change. To effectively control GHG emissions, soil supplemented with biochar at different application rates (0%, 2%, 4% and 6% [w/w]) under different numbers of FTCs (0, 3, 6, 9, and 12) was selected as the research object. The soil GHG emission characteristics in different experimental treatments and their relationships with soil physical and chemical properties were determined. Our results showed that N₂O and CO₂ emissions were promoted during FTCs, with values of 3.13–50.37 and 16.22–135.50 μg m⁻² h⁻¹, respectively. The order of N₂O and CO₂ emissions with respect to biochar application rate was as follows: 2% > 0% > 4% > 6%. CH₄ emissions were negative during FTCs, varying from −1.62 to −10.59 μg m⁻² h⁻¹, and negative CH₄ emissions were promoted by biochar. Correlation analysis showed that N₂O, CO₂ and CH₄ emissions were significantly correlated with pH, soil moisture and soil organic matter (SOM), total nitrogen (TN) and ${\mathrm{NH}}_4^{+}$–N contents (p < .01). The conceptual path model demonstrated that GHG emissions were significantly influenced by FTCs, moisture, SOM and biochar application rate. Our results indicate that the effects of FTCs on GHG emissions were greater than those of biochar application. Biochar application rates of 4% or 6% should be considered in the future to reduce soil GHG emissions in the black soil region of Northeast China. Our results can help provide a theoretical basis and effective strategy to reduce soil GHG emissions during FTCs in seasonally frozen regions.     

Effect of straw biochar application on soil carbon,greenhouse gas emissions and nitrogen leaching: A vegetable crop rotation field experiment

Intensive vegetable crop systems are rapidly developing, with consequences for greenhouse gas (GHGs) emissions, nitrogen leaching and soil carbon. We undertook a field trial to explore the effect of biochar application (0, 10, 20 and 40 t ha⁻¹) on these factors in lettuce, water spinach and ice plant rotation. Our results show that the 20 and 40 t ha⁻¹ soil treatments resulted in the SOC content being 26.3% and 29.8% higher than the control (0 t ha⁻¹), respectively, with significant differences among all treatments (p < .05). Biochar application caused N₂O emissions to decrease during the lettuce and water spinach seasons, by 1.5%–33.6% and 12.4%–40.5%, respectively, compared the control, with the 20 t ha⁻¹ application rate resulting in the lowest N₂O emissions. Biochar also decreased the dissolved nitrogen (DN) concentration in leachate by 9.8%–36.2%, following a 7.3%–19.9% reduction in dissolved nitrogen in the soil. Similarly, biochar decreased the nitrate (NO₃⁻) concentrations in leachate by 3.9%–30.2%, following a 3.8%–16.7% reduction in the soil nitrate level. Overall, straw biochar applied at rate of 20 t ha⁻¹ produced the lowest N₂O emissions and N leaching, while, increasing soil carbon.     

不同措施对河套灌区重度盐渍土改良效果

为了探究不同灌溉模式施加不同改良剂对河套灌区重度盐渍土的改良效果,设置秸秆深埋(SL)、石膏+有机肥(SF)、对照(CK)3个处理,对河套灌区重度盐渍土土壤盐分在0-70 cm剖面上的分布特点进行研究。结果表明:不同灌溉模式,SL和SF处理在0-15 cm土层均有效降低土壤pH,随改良时间延长改良深度增加pH持续降低,有一定的长效性,滴灌SL与SF处理pH较CK分别下降0.35,0.49,黄灌下降0.42,1.33,对30-70 cm土层影响较小。SF处理碱化度第2年下降达43%,SL处理为40%,滴灌更利于碱化度降低。从抑制盐分积累来看,SL与SF处理能有效抑制盐分0-15 cm土层聚集,黄灌SL与SF处理较CK分别下降13.60%,7.70%,滴灌分别下降31.60%,6.90%,SL处理抑盐效果较显著。土壤盐基离子表明,不同灌溉模式,SL与SF处理均显著降低0-15 cm土层Na~+与HCO_3~-的含量,滴灌降低比例高于黄灌,随着改良时间延长效果越显著,15-70 cm土层无明显变化。石膏加有机肥的施入提高0-70 cm土层SO_4~(2-)、Ca~(2+)及Cl~-的含量。通过对比分析,对河套灌区重度盐渍土治理而言,秸秆深埋和石膏+有机肥均能有效抑制重度盐渍土土壤积盐,有效降低pH及碱化度。整体来看,滴灌模式下石膏+有机肥改良效果优于秸秆深埋。     

不同矿化度微咸水灌溉冬小麦对下季作物产量和周年土壤盐分平衡的影响

冬小麦夏玉米一年两熟是环渤海低平原主要粮食作物种植模式,该区淡水资源匮乏,但浅层微咸水相对丰富,在降水较少的冬小麦生长季,适当利用微咸水代替淡水灌溉对维持冬小麦稳产高产有重要作用。冬小麦季实施微咸水灌溉后土壤盐分累积如何影响下季作物夏玉米生长以及对土壤周年盐分平衡影响,是微咸水能否长期安全利用的关键。为探究上述问题,于2015—2019年连续4年在环渤海低平原中国科学院南皮生态农业试验站进行冬小麦季不同矿化度微咸水灌溉定点试验,共设置含盐量为1 g·L~(-1)淡水(F)、3 g·L~(-1)微咸水(S3)、4 g·L~(-1)微咸水(S4)、5 g·L~(-1)微咸水(S5) 4个梯度,在拔节期灌水1次,灌水量均为70 mm;另以生育期不灌水作为对照(旱作, CK)。结果表明,不同矿化度微咸水灌溉处理间冬小麦产量没有显著差异,但平均比CK显著增产31.6%。同时,冬小麦生长季微咸水灌溉均增加了收获时1 m以上土层的含盐量,并随灌溉水含盐量增加而增加;对1 m以下土层含盐量影响不明显。夏玉米播种时灌溉70 mm淡水不仅解决了土壤墒情不足问题,并可使0～20 cm土层盐分控制在1 g·kg~(-1)以下,保证夏玉米出苗和群体建立,对夏玉米产量没有显著影响。经过夏季降雨的淋洗, S3、S4和S5处理0～40cm土层含盐量降低幅度超过30%,深层土壤含盐量变化不明显,1m以上土层可以实现周年盐分平衡。本研究表明冬小麦-夏玉米一年两季种植,冬小麦耐盐能力较强的特征使其生育期可以通过不大于5g·L~(-1)的微咸水灌溉维持稳产,在保证夏玉米出苗水进行灌溉的条件下,夏玉米季通过雨季降水淋盐维持0～1m主要根层土壤不发生明显积盐过程,可实现长期微咸水灌溉下土壤和作物安全。