Offsetting global CO2 emissions by restoration of degraded soils and intensification of world agriculture and forestry

Increase in atmospheric concentration of CO₂ from 285 parts per million by volume (ppmv) in 1850 to 370 ppm in 2000 is attributed to emissions of 270 ± 30 Pg carbon (C) from fossil fuel combustion and 136 ± 55 Pg C by land‐use change. Present levels of anthropogenic emissions involve 6·3 Pg C by fossil fuel emissions and 1·8 Pg C by land‐use change. Out of the historic loss of terrestrial C pool of 136 ± 55 Pg, 78 ± 12 Pg is due to depletion of soil organic carbon (SOC) pool comprising 26 ± 9 Pg due to accelerated soil erosion. A large proportion of the historic SOC lost can be resequestered by enhancing the SOC pool through converting to an appropriate land use and adopting recommended management practices (RMPs). The strategy is to return biomass to the soil in excess of the mineralization capacity through restoration of degraded/desertified soils and intensification of agricultural and forestry lands. Technological options for agricultural intensification include conservation tillage and residue mulching, integrated nutrient management, crop rotations involving cover crops, practices which enhance the efficiency of water, plant nutrients and energy use, improved pasture and tree species, controlled grazing, and judicious use of inptus. The potential of SOC sequestration is estimated at 1–2 Pg C yr⁻¹ for the world, 0·3–0·6 Pg C yr⁻¹ for Asia, 0·2–0·5 Pg C yr⁻¹ for Africa and 0·1–0·3 Pg C yr⁻¹ for North and Central America and South America, 0·1–0·3 Pg C yr⁻¹ for Europe and 0·1–0·2 Pg C yr⁻¹ for Oceania. Soil C sequestration is a win–win strategy; it enhances productivity, improves environment moderation capacity, and mitigates global warming. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of crop residue incorporation on soil organic carbon and greenhouse gas emissions in European agricultural soils

Soil organic matter (SOM) improves soil physicochemical and biological properties, and the sequestration of carbon in SOM may mitigate climate change. Soil organic carbon (SOC) often decreases in intensive cropping systems. Incorporation of crop residues (CR) may be a sustainable management practice to maintain the SOC levels and to increase soil fertility. This study quantifies the effects of CR incorporation on SOC and greenhouse gas (GHG) emissions (CO₂ and N₂O) in Europe using data from long‐term experiments. Response ratios (RRs) for SOC and GHG emissions were calculated between CR incorporation and removal. The influence of environmental zones (ENZs), clay content and experiment duration on the RRs was investigated. We also studied how RRs of SOC and crop yields were correlated. A total of 475 RRs were derived from 39 publications. The SOC increased by 7% following CR incorporation. In contrast, in a subsample of cases, CO₂ emissions were six times and N₂O emissions 12 times higher following CR incorporation. The ENZ had no significant influence on RRs. For SOC concentration, soils with a clay content >35% showed 8% higher RRs compared with soils with clay contents between 18 and 35%. As the experiment progressed, RR for SOC concentration increased. For N₂O emissions, RR was significantly greater in experiments with a duration <5 yr compared with 11–20 yr. No significant correlations were found between RR for SOC concentration and yields, but differences between sites and study durations were detected. We suggest that a long duration of crop residue incorporation is a win‐win scenario under a continental climate. We conclude that CR incorporation is important for maintaining SOC, but its influence on GHG emissions should be taken into account as well.     

Functional dependencies of soil CO2 emissions on soil biological properties in northern German agricultural soils derived from a glacial till

Agricultural soil CO₂ emissions and their controlling factors have recently received increased attention because of the high potential of carbon sequestration and their importance in soil fertility. Several parameters of soil structure, chemistry, and microbiology were monitored along with soil CO₂ emissions in research conducted in soils derived from a glacial till. The investigation was carried out during the 2012 growing season in Northern Germany. Higher potentials of soil CO₂ emissions were found in grassland (20.40 µg g^?1 dry weight h^?1) compared to arable land (5.59 µg g^?1 dry weight h^?1) within the incubating temperature from 5°C to 40°C and incubating moisture from 30% to 70% water holding capacity (WHC) of soils taken during the growing season. For agricultural soils regardless of pasture and arable management, we suggested nine key factors that influence changes in soil CO₂ emissions including soil temperature, metabolic quotient, bulk density, WHC, percentage of silt, bacterial biomass, pH, soil organic carbon, and hot water soluble carbon (glucose equivalent) based on principal component analysis and hierarchical cluster analysis. Slightly different key factors were proposed concerning individual land use types, however, the most important factors for soil CO₂ emissions of agricultural soils in Northern Germany were proved to be metabolic quotient and soil temperature. Our results are valuable in providing key influencing factors for soil CO₂ emission changes in grassland and arable land with respect to soil respiration, physical status, nutrition supply, and microbe-related parameters.     

Temporal variation in soil carbon in various paddy soil types in a cold temperate continental monsoon climate

Soil organic carbon (SOC) is the most important carbon pool in the terrestrial ecosystem. However, temporal variations in paddy SOC under a temperate continental monsoon climate are poorly understood. Here, we demonstrate that significant SOC variations occur in meadow soil (MS), black soil (BS) and planosol (PS) paddy soils. Several soil samples were collected from different regions where rice was cultivated for 1, 6, 10, 23 and 40 years for MS samples; for 1, 6, 10, 20 and 35 years for BS samples and 1, 5, 10, 15 and 25 years for PS samples. The total organic carbon (TOC) content and humus organic carbon (HOC) content were found to increase as the rice cultivation duration increased, while the mineralizable organic carbon (MOC) content and carbohydrate organic carbon (COC) content exhibited the opposite trend. The relationships between the relative carbon accumulation (Y) in the three soil types and time (X) were consistent with the following models: Y_TOC = 0.9973X^0.0245, Y_HOC = 0.9936X^0.0457, Y_MOC = 1.023X^−0.073, and Y_COC = 1.040X^−0.059, describing the temporal variation in the various forms of organic carbon in paddy soils under a temperate continental monsoon climate. The results of this study provide a reference for soil carbon pool management and fertilization management.     

气候和土壤质地对土壤有机碳影响的区域差异研究

The agricultural soil carbon pool plays an important role in mitigating greenhouse gas emission ana unaerstanamg the son orgamc carbon-climate-soil texture relationship is of great significance for estimating cropland soil carbon pool responses to climate change. Using data from 900 soil profiles, obtained from the Second National Soil Survey of China, we investigated the soil organic carbon （SOC） depth distribution in relation to climate and soil texture under various climate regimes of the cold northeast region （NER） and the warmer Huang-Huai-Hai region （HHHR） of China. The results demonstrated that the SOC content was higher in NER than in HHHR. For both regions, the SOC content at all soil depths had significant negative relationships with mean annual temperature （MAT）, but was related to mean annual precipitation （MAP） just at the surface 0-20 cm. The climate effect on SOC content was more pronounced in NER than in HHHR. Regional differences in the effect of soil texture on SOC content were not found. However, the dominant texture factors were different. The effect of sand content on SOC was more pronounced than that of clay content in NER. Conversely, the effect of clay on SOC was more pronounced than sand in HHHR. Climate and soil texture jointly explained the greatest SOC variability of 49.0% （0-20 cm） and 33.5% （20-30 cm） in NER and HHHR, respectively. Moreover, regional differences occurred in the importance of climate vs. soil texture in explaining SOC variability. In NER, the SOC content of the shallow layers （0-30 cm） was mainly determined by climate factor, specifically MAT, but the SOC content of the deeper soil layers （30-100 cm） was more affected by texture factor, specifically sand content. In HHHR, all the SOC variability in all soil layers was predominantly best explained by clay content. Therefore, when temperature was colder, the climate effect became stronger and this trend was restricted by soil depth. The regional differences and soil depth influence underscored the importance of explicitly considering them in modeling long-term soil responses to climate change and predicting potential soil carbon sequestration.     

黄土区退耕草地合理放牧可减少土壤CO2排放和土壤侵蚀

【目的】在退耕草地实施合理放牧,有助于减少土壤CO2排放、 减缓土壤侵蚀。为验证此假设,本研究选择黄土高原渭北旱原坡地,建立退耕草地放牧、 退耕草地不放牧和传统农业耕作三种处理的对比试验小区,定量研究了退耕草地合理放牧相对于退耕草地在减少土壤CO2排放和土壤侵蚀的作用及其影响因素,为探寻在我国西部退耕还草区实施畜牧业生产与环境保护的协调发展模式提供科学依据。【方法】在建立的退耕草地放牧、 退耕草地不放牧和传统农业耕作3种处理的试验小区,利用LI-8100 碳通量自动测量仪原位监测植物生长期(4~8月)和放牧前后土壤CO2排放速率的变化,同时利用时域反射仪(TDR)测定表层0—10 cm土壤含水量,用地温表测定土壤表层2 cm和5 cm的温度。利用环境放射性核素 7Be示踪技术监测较大降雨事件引起的土壤侵蚀速率,同时取样测定侵蚀区土壤有机碳含量,比较不同处理小区侵蚀导致的土壤有机碳流失量。【结果】观测期间,3种处理CO2平均排放速率大小顺序为退耕草地[3.69±0.39 μmol/(m2·s)]退耕草地放牧[3.00±0.44 μmol/(m2·s)]传统农耕地[1.99±0.22 μmol/(m2·s)],坡耕地退耕还草后土壤CO2排放增加了85%,而合理放牧使退耕草地土壤CO2排放量减少了19%。放牧后退耕草地土壤CO2排放速率平均减少了11%,减少值在2% ~ 41%之间。观测期内,退耕草地放牧后土壤侵蚀速率比农耕地和退耕草地分别减少了93% 和77%。坡耕地退耕还草后土壤CO2排放增加主要由于草被植物引起土壤有机碳储量增加和土壤侵蚀强度减小,放牧后退耕草地土壤CO2排放减少主要与动物踩踏引起土壤容重明显增加及草类植被地上部分向土壤中输入的有机碳的减少有关。水分、 温度影响因子无法解释3种处理间土壤CO2排放差异。【结论】合理放牧不仅能显著减少退耕草地土壤CO2排放,而且可以有效控制退耕草地土壤和有机碳侵蚀流失。放牧期间动物的踩踏作用引起草地土壤容重显著增加是退耕草地土壤CO2排放量和土壤侵蚀速率减少的主要原因。本研究结果揭示,在我国黄土高原和类似的退耕还草地区实施合理放牧既可以促进当地畜牧业生产,又能控制土壤侵蚀和减少CO2的排放,是一种值得探究的草地可持续发展管理模式。     

长期施肥下红壤旱地土壤CO2排放及碳平衡特征

在国家肥力网红壤旱地长期定位试验地上,采用静态箱/气相色谱法测定土壤CO2排放速率,同时利用根去除法区分根系对土壤呼吸的贡献,通过计算净生态系统生产力（NEP）,判断长期不同施肥下红壤旱地农田碳汇强度。结果表明,小麦、玉米生长季各处理的土壤和土体呼吸速率随着作物生长、温度升高均呈现明显的季节变化规律;玉米生长季土壤和土体累积呼吸量大于小麦生长季,小麦、玉米生长季均以NPKM处理土壤和土体呼吸累积呼吸量最大,且显著高于其它处理（P0.05）,NP和NPK处理次之,CK和NK处理最小（P0.05）;小麦、玉米生长季各处理根际呼吸占土壤呼吸的比例分别为7.6 %～17.4 %、4.7%～16.6 %,均以NPKM处理根际呼吸贡献率最大;小麦季NPKM处理、玉米季CK和NPKM处理的NEP值为负,是大气CO2的汇,且NPKM处理的净初级生产力与土壤呼吸的比值（NPP/Rs）最大,其它处理NEP值均为正,是大气CO2的源。有机无机肥配施（NPKM）相比其它处理具有较强的碳汇功能,是红壤旱地比较合理的施肥措施。     

Adding dissolved organic carbon to simulate freeze‐thaw related N2O emissions from soil

It has been assumed that high winter N₂O emissions from soils are the result of increased amounts of microbially available organic C liberated during freezing and metabolized during subsequent thawing. In a laboratory experiment, we attempted to simulate freeze‐thaw events by adding dissolved organic C (DOC) to sieved soil of high water content (95% water‐filled pore space). In a full factorial design, CO₂ and N₂O emissions of a) soil samples provided with DOC extracted from frozen soil and b) soil samples frozen for 46 days and thawed were compared. Additionally, NO , DOC and microbial ATP contents of all treatments were repeatedly analyzed during the experiment. The addition of DOC to unfrozen soil (–F+C) resulted in a substantial (22‐fold) increase in N₂O emissions as compared to the control (–F–C). However, following thawing, the increase in N₂O emissions was much larger (828‐fold in +F–C and 1243‐fold in +F+C). Freezing, but not the addition of DOC led to increased CO₂ emissions. Neither treatment affected microbial adenylate content. By adding ¹⁵N‐labeled nitrate to the soil samples, the main process leading to elevated N₂O flux rates after both DOC addition and freeze‐thaw treatment was identified as denitrification. We conclude that the availability of C substrate plays an important role for freeze‐thaw‐related N₂O emissions. However, the fact that the simulated treatment and the freeze‐thaw treatment yielded significantly different amounts of N₂O suggests that both quantity and quality of available C differed between the treatments. The localization of the liberated substrate, i.e., the availability in situ, seems to be of major importance for the amount of N₂O produced.     

Consequences of feasible future agricultural land‐use change on soil organic carbon stocks and greenhouse gas emissions in Great Britain

The aim of this study was to assess the consequences of feasible land‐use change in Great Britain on GHG emissions mainly through the gain or loss of soil organic carbon. We use estimates of per‐area changes in soil organic carbon (SOC) stocks and in greenhouse gas (GHG) emissions, coupled with Great Britain (GB) county‐level scenarios of land‐use change based on historical land‐use patterns or feasible futures to estimate the impact of potential land‐use change between agricultural land‐uses. We consider transitions between cropland, temporary grassland (<5 yr under grass), permanent grass (>5 yr under grass) and forest. We show that reversion to historical land‐use patterns as present in 1930 could result in GHG emission reductions of up to ca. 11 Mt CO₂‐eq./yr (relative to a 2004 baseline), because of an increased permanent grassland area. By contrast, cultivation of 20% of the current (2004) permanent grassland area for crop production could result in GHG emission increases of up to ca. 14 Mt CO₂‐eq./yr. We conclude that whilst change between agricultural land‐uses (transitions between permanent and temporary grassland and cropland) in GB is likely to be a limited option for GHG mitigation, external factors such as agricultural product commodity markets could influence future land‐use. Such agricultural land‐use change in GB could have significant impacts on Land‐use, Land‐Use Change and Forestry (LULUCF) emissions, with relatively small changes in land‐use (e.g. 5% plough out of grassland to cropland, or reversion of cropland to the grassland cover in Nitrate Vulnerable Zones of 1998) having an impact on GHG emissions of a similar order of magnitude as the current United Kingdom LULUCF sink. In terms of total UK GHG emissions, however, even the most extreme feasible land‐use change scenarios account for ca. 2% of current national GHG emissions.     

Soil tillage and cover crop on soil CO2 emissions from sugarcane fields

Soil tillage is an agricultural practice that directly affects the global carbon cycle. Our study sought to assess the implications of adopting sunn hemp cover crops with different tillage practices on CO₂ emissions for two soil types (clayey and sandy soil) cultivated with sugarcane in Brazil. The experimental design was a split‐plot with randomized blocks, with the main plots being with cover crop or fallow and sub‐plots being under conventional or minimum tillage. Our results indicate that during the first 50 days after soil tillage, the variation in soil CO₂ emissions was stimulated by cover crop and soil tillage, while after that, it became dominated by the root respiration of sugarcane plants. We also found that over the first 97 days after the tillage, the clayey soil showed differences between minimum tillage with cover crop and fallow. Conversely, for sandy soil over the first 50 days following, there were differences between the tillage systems under cover cropping. Emissions from sugarcane rows were found to be greater than those from inter‐row positions. We concluded that soils under different textural classes had distinct patterns in terms of soil CO₂ emissions. The correct quantification of CO₂ emissions during the sugarcane renovation period should prioritize having a short assessment period (~50 days after soil tillage) as well as including measurements at row and inter‐row positions.     

Analysis and simulation of soil organic‐carbon stocks in grassland ecosystems in SW Germany

Grassland extensification is followed by a change of soil organic‐matter (SOM) contents. In order to give a better assessment of these developments on grassland sites in SW Germany, the CENTURY Soil Organic Matter Model was used on five long‐term experimental sites under three different management practices (“Mowing”, “Mulching” (mowing without removal of the phytomass), and “Natural succession”). On these sites, soil‐organic‐carbon (SOC) monitoring was continuously done for soil depths of 0–4 and 4–8 cm from 1975 to 2002. The contents of organic carbon (OC) were at steady state or showed a slight decrease for the mulched and succession plots. Carbon contents of the mowed plots were decreasing. Measured C contents were transferred into stocks and compared with the simulated OC stocks. Linear regressions between observed and simulated C stocks were calculated separately for mulched and succession plots. The regressions for OC yielded significant relationships (R² = 0.8) for both kinds of plots. However, the model did not reproduce the short‐term dynamics of C stocks. Whereas SOC stocks on mulched and succession plots are expected to stay stable for the next decades according to the simulation, they are expected to decrease for a couple of years before stabilization on mowed plots.     

Effects of biochar amendment on greenhouse gas emissions,net ecosystem carbon budget and properties of an acidic soil under intensive vegetable production

Biochar addition to soils has been frequently proposed as a means to increase soil fertility and carbon (C) sequestration. However, the effect of biochar addition on greenhouse gas emissions from intensively managed soils under vegetable production at the field scale is poorly understood. The effects of wheat straw biochar amendment with mineral fertilizer or an enhanced‐efficiency fertilizer (mixture of urea and nitrapyrin) on N₂O efflux and the net ecosystem C budget were investigated for an acidic soil in southeast China over a 1‐yr period. Biochar addition did not affect the annual N₂O emissions (26–28 kg N/ha), but reduced seasonal N₂O emissions during the cold period. Biochar increased soil organic C and CO₂ efflux on average by 61 and 19%, respectively. Biochar addition greatly increased C gain in the acidic soil (average 11.1 Mg C/ha) compared with treatments without biochar addition (average ?2.2 Mg C/ha). Biochar amendment did not increase yield‐scaled N₂O emissions after application of mineral fertilizer, but it decreased yield‐scaled N₂O by 15% after nitrapyrin addition. Our results suggest that biochar amendment of acidic soil under intensive vegetable cultivation contributes to soil C sequestration, but has only small effects on both plant growth and greenhouse gas emissions.     

Application of mixed straw and biochar meets plant demand of carbon dioxide and increases soil carbon storage in sunken solar greenhouse vegetable production

Solar vegetable greenhouse soils show low soil organic carbon content and thus also low rates of soil respiration. Processing vegetable residues to biochar and mixing biochar with maize straw might improve soil respiration and increase soil organic carbon stocks, while preventing the spread of soil-borne diseases carried by vegetable residues. In an incubation experiment, we tested how additions of maize straw (S) and biochar (B) added in varying ratios (100S, 75S25B, 50S50B, 25S75B, 100B and 0S0B (control)) affect soil respiration and fraction of added C remaining in soil. Daily CO₂ emissions were measured over 60 days incubation, the natural abundance of ¹³C in soil and in the added biochar and maize straw were analysed. Our result shows that (a) soil CO₂ emissions were significantly increased compared to soil without the straw additions, while addition of biochar only decreased soil respiration; (b) cumulative CO₂ emissions decreased with increasing ratio of added biochar to maize straw; (c) the abundance of soil ¹³C was significant positively correlated with cumulative CO₂ emissions, and thus with the ratio of straw addition. Our results indicate that incorporation of maize straw in greenhouse soils is a meaningful measure to increase soil respiration and to facilitate greenhouse atmosphere CO₂ limitation while producing vegetables. On the other hand, additions of biochar from vegetable residues will increase soil organic carbon concentration. Therefore, the simultaneous application of maize straw and biochar obtained from vegetable residues is an effective option to maintain essential soil functions for vegetable production in sunken solar greenhouses.     

美国路易斯安那州土壤碳估算的尺度效应——美国STATSGO和SSURGO两大最新土壤数据库的比较研究

Estimation of soil organic carbon (SOC) pools and fluxes bears large uncertainties because SOC stocks vary greatly over geographical space and through time.Although development of the U.S.Soil Survey Geographic Database (SSURGO),currently the most detailed level with a map scale ranging from 1:12 000 to 1:63 360,has involved substantial government funds and coordinated network efforts,very few studies have utilized it for soil carbon assessment at the large landscape scale.The objectives of this study were to 1) compare estimates in soil organic matter among SSURGO,the State Soil Geographic Database (STATSGO),and referenced field measurements at the soil map unit;2) examine the influence of missing data on SOC estimation by SSURGO and STATSGO;3) quantify spatial differences in SOC estimation between SSURGO and STATSGO,specifically for the state of Louisiana;and 4) assess scale effects on soil organic carbon density (SOCD) estimates from a soil map unit to a watershed and a river basin scale.SOC was estimated using soil attributes of SSURGO and STATSGO including soil organic matter (SOM) content,soil layer depth,and bulk density.Paired t-test,correlation,and regression analyses were performed to investigate various relations of SOC and SOM among the datasets.There were positive relations of SOC estimates between SSURGO and STATSGO at the soil map unit (R2=0.56,n=86,t=1.65,P=0.102;depth:30 cm).However,the SOC estimated by STATSGO were 9%,33% and 36% lower for the upper 30-cm,the upper 1-m,and the maximal depth (up to 2.75 m) soils,respectively,than those from SSURGO.The difference tended to increase as the spatial scale changes from the soil map unit to the watershed and river basin scales.Compared with the referenced field measurements,the estimates in SOM by SSURGO showed a closer match than those of STATSGO,indicating that the former was more accurate than the latter in SOC estimation,both in spatial and temporal resolutions.Further applications of SSURGO in SOC estimation for the entire United States could improve the accuracy of soil carbon accounting in regional and national carbon balances.     

大气CO2浓度升高对土壤碳库的影响

土壤碳库是输入、输出土壤碳量的平衡:大气CO2浓度升高有可能通过生态系统中的各种生理过程来增加输入土壤的碳量,输入土壤碳量的增加使土壤成为一个潜在的碳汇,有可能缓解大气CO2浓度的升高;但另一方面输入土壤碳量的增加,为微生物的生长提供了能量,从而提高了微生物的活性,因此土壤呼吸增强,土壤碳输出增加.本文综述了大气CO2浓度升高对土壤碳输入、输出的影响以及目前研究中存在的争论,并提出有待进一步研究的领域和方向.     

Potential for greenhouse gas emissions from soil carbon stock following biofuel cultivation on degraded lands

Consequent to the interest in converting degraded lands for cultivation of biofuel crops, concerns have been expressed about greenhouse gas (GHG) emissions resulting from changes in soil‐carbon (C) stock following land conversions. A literature‐based study was undertaken for estimating the magnitude of emission of GHGs, particularly carbon dioxide (CO₂), following an assessment of the extent and causes of land degradation and the nature of CO₂ emission from soils. The study estimated the potential for CO₂ emission resulting from changes in soil‐carbon stock following land conversions, using oil palm (Elaeis guineensis Jacq.) as a case study. The analysis indicated that, overall, the magnitude of CO₂ emission resulting from changes in soil C stock per se following opening up of degraded land would be low compared with other potential sources of CO₂ emission. However, lack of data on critical aspects such as baseline soil C status was a limitation of the study. Soil respiration is the single best measure of GHG emission from soils. Fixation of C in additional biomass will compensate, over time, for C loss through soil respiration following a change in land use or land management, unless such changes involve conversion of existing large C stocks. Therefore, any net CO₂ emission from soils resulting from changes in soil C stock following opening up of degraded land is likely to be a short‐term phenomenon. The estimations used in the study are based on various assumptions, which need to be validated by experimental field data. Copyright © 2010 John Wiley & Sons, Ltd.     

Soil CO2 emission and its relationship to soil properties under different tillage systems

There is a lack of understanding as to which soil property is the most important at regulating the temporal variability of soil CO₂ emissions on China’s Loess Plateau. The objective of this study was to evaluate the CO₂ emissions and their relationships to certain soil properties in a winter wheat (Triticum aestivum L.) field subject to no-till (NT) and conventional tillage (CT) practices. The CO₂ emissions were signi?cantly higher in the CT (257.6 mg CO₂ m^?2 h^?1), compared with the NT (143.8 mg CO₂ m^?2 h^?1), treatment. Soil organic matter content and carbon stock were 8% and 14% higher, respectively, in the NT, compared with the CT, treatment. Regression analyses between the CO₂ emissions and soil properties, including soil temperature and carbon stock, explained up to 88% and 60% of the temporal variability in CO₂ emissions in the NT and CT treatments, respectively. Linear correlations between the soil temperature and CO₂ emissions were recorded in both the NT and CT treatments. Soil temperature was the most important factor in terms of understanding the temporal variability in CO₂ emissions in wheat fields of the study area.     

Manure application followed by biochar application increases plant production regardless of soil dehydrogenase activity

Biochar is obtained by the pyrolysis of biomass, and contains abundant carbon and minerals. Biochar supplementation of soils can greatly improve soil health and quality, but these beneficial effects typically develop slowly over time. Depending on the quality of the biochar and the soil to which it is applied, it may take years before positive effects are apparent. This is because organic substances are slowly sorbed onto the biochar over time, and the biochar eventually becomes part of the sorption complex of the soil. It is therefore advisable to apply biochar together with some organic material. We examined the effect of co-application of different doses of biochar with manure on soil dehydrogenase activity (DHA), soil oxidizable carbon (COX), cumulative soil respiration, soil buffering capacity, the soil exchange reaction (pH/KCl) and the production yield of winter rape seeds. We also determined seed production when artificial granular fertilizers were added to biochar and manure. The results showed that the application of biochar and manure significantly increased grain yield, DHA, the soil exchange reaction and cumulative respiration. Thus, application of biochar with organic material can increase seed yield and some properties of agricultural soils. However, the positive effect of biochar on seed yield was not directly proportional to biochar dose, in that the seed yield was lower for a biochar dose of 45 t/ha than 30 t/ha.