Effects of biochars and hydrochars produced from lignocellulosic and animal manure on fertility of a Mollisol and Entisol

Biochar and hydrochars (HC) are emerging soil fertility amendments; however, their ability to improve fertility levels in soils possessing vastly different pedogenic characteristics has not been well investigated. In this study, several plant and manure biochars and two blended HC applied at 3.84 g/kg (ca.10 t/ha) were incubated in pots containing a highly fertile‐Mollisol (Waukegan series; Sandy‐skeletal, mixed, superactive, mesic Typic Hapludoll) and an infertile Entisol (Margate series; Siliceous, hyperthermic, Mollic Psammaquent). During the 124–125 day laboratory incubations, pots were leached four times with deionized H₂O with the leachates analysed for the concentrations of dissolved phosphorus (DP) and potassium (DK). After the incubations, both soils were analysed for fertility characteristics (i.e. pH, cation‐exchange capacity (CEC), and extractable P and K). In both soils after biochar additions, there were mixed pH and CEC responses. Both the Mollisol and Entisol treated with swine solid biochar had greater plant extractable P and K contents, which was reflective of the elevated P and K contents in the swine solid biochar. However, most biochars and HC additions to the Mollisol and Entisol had minimal impact on soil fertility characteristics indicating a low direct fertilization potential. These nutrient contents could be altered through feedstock blending to target a particular fertilizer requirement.     

生物质炭对冬小麦产量、水分利用效率及根系形态的影响

为了探讨生物质炭对冬小麦产量、水分利用效率及根系形态的影响,该文利用田间小区试验研究了生物质炭不同施用水平对冬小麦产量、水分利用效率、根形态的影响及差异性。结果表明:生物质炭显著增加了冬小麦茎蘖数、有效穗数和产量(P0.05),与对照相比,其增加比例范围分别为1.6%~4.9%、0.7%~1.5%、1.0%~5.9%。冬小麦耗水量随着生物质炭施用量的增加而逐渐减小,水分利用效率由对照的17.06 kg/(hm2·mm)提高到17.69~19.57 kg/(hm2·mm)。生物质炭显著增加了冬小麦根系总根长和总表面积(P0.05),在0~20和≥20~40 cm范围内,总根长的增加比例范围分别为2.8%~14.6%、8.4%~21.2%;总表面积增加比例范围分别为5.6%~19.5%、1.9%~13.6%。冬小麦根系形态特征与冬小麦产量呈极显著正相关(P0.001)。各处理中以生物质炭施用量为40 t/hm2的处理对冬小麦产量、水分利用效率及根系生长的促进作用最为显著。该研究可为科学施用生物质炭提供参考。     

Influence of disturbance and nitrogen addition on plant and soil animal diversity in grassland

Two key determinants of biological diversity that have been examined in aboveground and aquatic systems are productivity, or resource supply, and physical disturbance. In this study, we examined how these factors interact under field conditions to determine belowground diversity using microarthropods (mites and Collembola) as our test community. To do this, we established a field manipulation experiment consisting of crossed, continuous gradients of nitrogenous (N) fertilizer addition (up to 240 kg N ha^?1) and disturbance (imitated trampling by cattle) to produce a gradient of soil nutrient availability and disturbance. Due to the relatively short-term nature of our study (i.e. 2 years), we only detected minimal changes in plant diversity due to the experimental manipulations; in the longer term we would expect to detect changes in plant diversity that could potentially impact on soil fauna. However, disturbance reduced, and additions of N increased, aboveground biomass, reflecting the potential effects of these manipulations on resource availability for soil fauna. We found that disturbance strongly reduced the abundance, diversity, and species richness of oribatid mites and Collembola, but had little effect on predatory mites (Mesostigmata). In contrast, N addition, and therefore resource availability, had little effect on microarthropod community structure, but did increase mesostigmatan mite richness and collembolan abundance at high levels of disturbance. Oribatid community structure was mostly influenced by disturbance, whereas collembolan and mesostigmatan diversity were responsive to N addition, suggesting bottom-up control. That maximal species richness of microarthropod groups overall occurred in undisturbed plots, suggests that the microarthropod community was negatively affected by disturbance. We found no change in microarthropod species richness with high N additions, where plant productivity was greatest, indicating that soil biotic communities are unlikely to be strongly regulated by competition. We conclude that the diversity of soil animals is best explained as a combination of their many varied life history tactics, phenology and the heterogeneity of soils that enable so many species to co-exist.     

富含磁性铁纳米颗粒的生物炭对菌根侵染、植物生长、营养吸收及土壤质量改善的影响

At present, there is little commercial sale of biochar, since farmers find they can not gain a return on their investment in this amendment in the first few years after its application, because of the high cost associated with large application rates. To overcome this constraint, development of artificially aged enriched biochar-mineral complexes (BMCs), having a higher mineral content, surface functionality, exchangeable cations, high concentration of magnetic iron (Fe) nanoparticles, and higher water-extractable organic compounds has been undertaken by a combined team of researchers and a commercial company.~% Two biochars produced under different pyrolysis conditions were activated with a phosphoric acid treatment. A mixture of clay, chicken litter, and minerals were added to the biochar, and then this composite was torrefied at either 180 or 220 $^\circ$C. In this study a pot experiment was carried out in glasshouse conditions to determine the effects of four different BMCs, with different formulations applied at rates of 100 and 200 kg ha$^{-1}$, on the mycorrhizal colonisation, wheat growth and nutrient uptake, and soil quality improvement. It was found that the phosphorus (P) and nitrogen uptake in wheat shoots were significantly greater for a low application rate of BMCs (100 kg ha$^{-1}$).~The present formulation of BMC was effective in enhancing growth of wheat at low application rate (100 kg ha$^{-1}$).~The increase in growth appeared due to an increase in P uptake in the plants that could be partly attributed to an increase in mycorrhizal colonisation and partly due to the properties of the BMC.     

Influence of water solubility of granular zinc fertilizers on plant uptake and growth

Abstract

Zinc (Zn) fertilizer application has increased during the past three decades. This increase has created the need for more information regarding the availability and agronomic effectiveness of Zn containing fertilizers because differences of opinions exist relating the relationships between Zn water solubility and plant availability. Plant availability of eight commercialized Zn fertilizer materials having different water solubilities was measured under greenhouse conditions. Corn (Zea mays L.) plants were grown for 40 days in a soil (loamy, mixed, mesic arenic Ustollic Haplargid) amended with lime to two pH's: 6.3 and 7.4. To evaluate the effect of pH, some Zn fertilizers were used at both soil pH levels while all Zn fertilizers were used in the pH 7.4 soil. The experimental design was a factorial combination of pH, Zn fertilizers, and Zn rates of 0,2.1,4.2,8.4 mg Zn kg^?1 soil. Dry matter production and Zn uptake increased significantly when the soil pH decreased from 7.4 to 6.3. The highest dry matter production was obtained with ZnSO₄ (ZnSO₄ H₂O, 99.9% total water soluble Zn), Zn20 (Zn oxysulfate, 98.3% total water soluble Zn), and Zn27 (Zn oxysulfate, 66.4% total water soluble Zn). While ZnFe (Zn iron ferrite, 0.3% total water soluble Zn), ZnK (Zn oxide, KO61, 1% total water soluble Zn), and ZnOS (Zn oxysulfate, 0.7% total water soluble Zn) were less effective followed by Zn40 (Zn oxysulfate, 26.5% total water soluble Zn) and ZnOxS (Zn oxysulfate, 11% total water soluble Zn). The same trend was observed for Zn concentration and uptake. Regression correlations showed that the higher the water solubility, the more effective the Zn fertilizer in increasing dry matter production. Assuming that 5 to 10 kg Zn ha^?1 are the rates commonly recommended, about 50% water soluble Zn is required to adequately supply the crop's needs. Lower fertilizer rates were needed as Zn solubility increased. The cadmium (Cd) and lead (Pb) concentrations and uptakes in corn forage were not significant for any of the sources and rates.     

不同农业废弃物生物炭及施用量对土壤pH值和保水保氮能力的影响

以黄秋葵秸秆炭(HQK)、茭白秸秆炭(JB)、水稻秸秆炭(SD)、废弃食用菌基质炭(JZ)、无花果秸秆炭(WHG)、猪粪炭(SM)和稻壳炭(DK)为供试原料,设置0.5%、1%、2%和5%4个添加浓度,研究不同生物炭及添加量对土壤pH值和保水保氮性能的影响。结果发现,所有生物炭添加量在2%时,均能显著提高土壤pH值,但不同生物炭调酸能力不同,JB和SD作用最强;生物炭能提高土壤持水能力,添加量在2%时,所有处理均极显著(P0.01)的提高了土壤持水量,增幅分布在2.87%～12.30%之间,SD效果最明显;生物炭能够吸附土壤溶液中NH_4~+-N,但吸附能力与生物炭的添加量无相关性,WHG吸附能力最强,JZ和HQK吸附能力最弱;添加生物炭对土壤溶液中的NO_3~--N则基本无吸附作用。     

Infiltration patterns into two soils under conventional and conservation tillage: influence of the spatial distribution of plant root structures and soil animal activity

The characteristics and properties of the soil macropore system may cause different infiltration behavior under different tillage practices. To evaluate the effect of a specific tillage system on infiltration and percolation with particular regard to the influence of crop structure and soil animal activity dye tracer irrigation experiments were conducted in a silty (Luvisol) as well as in a sandy loam soil (Podzolluvisol). The spatial distribution of water flow paths was experimentally examined at four square areas of 0.49 m², under conservation and conventional tillage. Natural rainstorms were simulated by irrigating the plots with 2.8×10⁻³ M methylene blue solutions. For both soils the root crowns of the agricultural crop, wormcasts and stained soil sections as well as macroscopic conduits were traced on plastic sheets. The investigated soil depths were 0, 5, 10 and 20 cm for the both soils. For the Luvisol, the 30, 40, 50, 80 and 120 cm depths were also studied.For the Luvisol, the conservation tillage plot revealed pronounced vertical connectivity and continuity of the macropore network (maximum depth of stained pores=120 cm), while at the conventional tillage plot, continuous macropores were observed to soil depths of 50 cm, but mainly restricted to the ploughed topsoil (0–30 cm soil depth).For the Podzolluvisol, at the conservation tillage site extensive mulch residues prevented water transport beneath 5 cm soil depth. In contrast, at the conventionally tilled site stained water reached a depth of 20 cm. For all investigated plots on both soil types, the location of the root crowns of agricultural crop and of wormcasts was not related to percolation patterns.The results suggest that conservation tillage on silty soils under agricultural landuse could induce an increased water retention capacity reducing the significance of fast runoff components.     

Vesicular-arbuscular mycorrhiza: Influence on plant uptake of cesium and cobalt

A study was made to determine if infection with vesicular-arbuscular mycorrhizal (VAM) fungi would increase the uptake of ¹³⁷Cs and ⁶⁰Co by Yellow sweetclover [Melilolus officinalis (L.) Lam] and Sudan grass [Sorghum sudanense (Piper) Stapf.]. Plants were inoculated by germinating and growing plants in small volumes of soil containing one of three inoculum sources. Control plants were grown in steam-sterilized inoculum to which sieved (38 μm) inoculum washings had been added. Infected and control plants, with the accompanying soil volume, were subsequently transplanted into pots containing autoclaved field soil which 7 yr previously had been contaminated with ¹³⁷Cs and ⁶⁰Co. The clover was harvested at 65 and 93 days; Cs content was 2.0 and 1.7 times that of the control respectively, on these dates, while Co was not significantly different. The grass was harvested at 85 and 119 days; Cs content was greater in the treated than the control grass, but not significantly; however, Co content was increased 2.5 times that of the control at the first harvest data, but was not significant at the second.     

Enzyme inactivation analysis for industrial blanching applications: comparison of microwave, conventional, and combination heat treatments on mushroom polyphenoloxidase activity.

Browning reactions in fruits and vegetables are a serious problem for the food industry. In mushrooms, the principal enzyme responsible for the browning reaction is polyphenoloxidase (PPO). Microwaves have recently been introduced as an alternative for the industrial blanching of mushrooms. However, the direct application of microwave energy to entire mushrooms is limited by the important temperature gradients generated within the samples during heating, which can produce internal water vaporization and associated damage to the mushrooms texture. A microwave applicator has been developed, whereby irradiation conditions can be regulated and the heating process monitored. Whole edible mushrooms (Agaricus bisporus) were blanched by conventional, microwave, and combined heating methods to optimize the rate of PPO inactivation. A combined microwave and hot-water bath treatment has achieved complete PPO inactivation in a short time. Both the loss of antioxidant content and the increase of browning were minor in the samples treated with this combined method when compared to the control. This reduction in processing time also decreased mushroom weight loss and shrinkage.     

Patterns and processes of carbon, water and energy cycles across northern Australian landscapes: From point to region

Savannas comprise a large proportion of the terrestrial land surface and are highly varied in their composition, structure and function. These characteristics alter land-atmosphere exchanges of heat, water, carbon dioxide and other trace gases, which feed back to the climate at multiple scales. Australian savannas provide significant ecosystem services and further systematic scientific study is needed to sustainably manage these ecosystems. We undertook an interdisciplinary research effort to understand the patterns and processes of carbon, water and energy cycles across northern Australian landscapes across scales from point to region. We quantified the land surface-atmosphere exchanges across the vast region of Australian savannas using a hierarchical, integrated measurement and modelling approach to determine regional greenhouse gas and water budgets. The research team comprised groups from seven institutions and four countries. The research effort comprised of a multi- year measurement and modelling endeavour and culminated in an intensive field program held in September 2008 (late dry season). The program aimed to improve our knowledge of the spatial and temporal variability of land-atmosphere exchanges and the processes driving them as well as our ability to remotely sense them and simulate them using land surface models, which are crucial components of Global Climate Models. We attempted to robustly integrate small scale processes, such as leaf photosynthesis to larger scales applicable to modelling and remote sensing for the savanna region. In this paper we provide the scientific background and our overall approach to the program with reference to the papers in this “Savanna Patterns of Energy and Carbon Integrated Across the Landscape” (SPECIAL) issue.     

Interaction between grapevines and trees: effects on water relations,nitrogen nutrition,and wine

Agroforestry systems (AF) consisting of grapevines and trees, may lead to resource competition for water and nutrients. This study aimed to evaluate the impact of a combined cultivation on water relations, nitrogen nutrition and the resulting wine quality.

¹⁵N-labeled inorganic nitrogen (N) sources were used to quantify net N uptake capacity. N content and δ¹⁵N natural abundance were analysed as integrating parameters of N nutrition. Leaf water potential (ψ_leaf) was determined to evaluate the water status of grapevines. Wine quality was evaluated by chemical and sensory analyses. In result, AF system reduced leaf water potential and increased net N uptake capacity in grapevines. However, chemical composition and sensory quality of the wine were not significantly affected in the present system consisting of Riesling, Sauvignon Blanc, oak and poplar.

Nitrogen availability of grapevines was favourable and water relations were improved, whereas wine quality was similar when grown with trees or without. Trees were able to reduce water and nitrogen losses without negative effects on wine quality.

This work provides information on benefits and limits for intercropping of trees and grapevines in terms of performance of grapevines and wine quality compared to traditional vineyard systems.     

Influence of water regime on growth,yield, and nitrogen uptake of rice

Abstract

Greenhouse and field experiments were conducted to study the effects of water regime on growth of rice. The greenhouse experiment investigated the effects of two water regimes‐continuous flooding and flooding with soil drying between crops for 2 to 3 weeks on the growth of rice during six cropping (for six week each) on seven soils varying widely in total N contents (0.07 to 0.35%). The results averaged for the 7 soils indicated that the drymatter production or N uptake of rice was not affected by the water regimes during the six croppings.

The field experiment conducted during the dry season for two consecutive years (1976 and 1977) on a near neutral clay soil studied the effects of three water regimes (continuous flooding alternate flooding and soil drying every 2 weeks, and continuous flooding with 2 weeks mid season soil drying after 6 weeks of transplanting) and three levels of fertilizer N (0, 100 and 200 kg N/ha as urea) on grain yield and N uptake of rice. The results confirmed the absence of any significant reduction in grain yield or N uptake as a result of any of the soil drying treatments during the growing season on the unfertilized plots carrying a rice crop. On the plots fertilized with 100 or 200 kg N/na, alternate flooding and drying resulted in a significant depression in both grain yield and N uptake. Soil analysis supported heavy losses of N in the fertilized plots that underwent alternate flooding and soil drying apparently by nitrification and denitrification reactions.

The results of this study suggest that alternate flooding and drying of soils in the presence of established rice plants itiay not cause a significant loss of nitrogen in unfertilized plots although in plots fertilized with high rates of N the losses may be large as indicated by the performance of rice crop.     

Rhizobacteria: Influence of cultivar and soil type on plant growth and yield of potato

The influence of potato cultivar and soil type on effectiveness of plant growth-promoting rhizobacteria (PGPR) was examined. Rhizobacteria were isolated from potato roots and tubers obtained from fields with a history of high potato yields. Fluorescent pigment-producing rhizobacteria. identified as strains of Pseudomonas putida and P. fluorescens, were selected for their antibiosis against Erwinia carovotora ssp. carotovora and growth-promoting activity on potatoes. In greenhouse tests, treatments of potato seedpieces and stem cuttings increased shoot dry weight from 1.23- to 2.00-fold and root dry weight from 1.27- to 2.78-fold. Survival of PGPR in the rhizosphere was monitored using antibioticresistant strains. Populations of these strains decreased from 3.6 × 10⁹ cgu g^?1 dry root weight to 4.5 × 10⁵ cfu g^?1 dry root weight 4 weeks after treatment. In field trials, PGPR strains were applied to seedpieces of cultivars Kennebec, Pungo, Red Pontiac and Superior and planted in Cape Fear loam. Plymouth loamy sand or Delanco sandy loam. Significant yield increases of 1.17–1.37-fold over controls were observed in two of three field trials. Variability in plant growth-promoting activity was observed between greenhouse and field trials, and no given treatment combination of PGPR strain, potato cultivar and soil type was consistently better than another.     

Influence of nitrogen rates and row spacing on corn yield,protein content,and other plant parameters

New maize hybrids has been intensively used as the first and second crop at the Cukurova region of Turkey in recent years. Therefore, nutritional problems of corn needs to be solved for the optimum yield, and protection from the potential insect and disease damages. Influence of nitrogen (N) and row spacing (RS) on corn yield, grain protein content, and selected plant parameters have been studied under field conditions in 1994 and 1995. Nitrogen was applied in the rates of 200, 250, 300, and 350 kg N ha^‐1 to main plots where row spacings were 10, 15, 20, and 25 cm in each subplots. Phosphorus (P) and potassium (K) were applied to each plot as basal rates. The experiment was arranged in a split‐plot design in three replications. During course of the experiment and after harvest, selected plant parameters, leaf nutrient contents, root length, grain yield, and crude protein content were measured, and the data were statistically analyzed for determination of treatment effects. The selected plant parameters either influenced by N, RS, or both in 1994 and 1995. The leaf N content was affected by N and RS in 1995, and a RS effect was only observed in 1994. Grain yield was influenced by RS and N and RS in the first and second years, respectively. Grain yield ranged between 7.3 to 12.8 Mg ha"¹ for both years. Treat ment effects on crude protein content was significant in 1994 but no response was obtained in 1995.     

氮钾水互作对玉米苗期植株生长及钾素吸收的影响

采用盆栽试验方法探讨了氮钾水互作对玉米苗期植株生长及养分吸收的影响。结果表明,水分适宜能明显增加玉米植株株高和干物重,水分适宜条件下玉米株高和干物重较水分亏缺条件的分别增加7.8%和13.8%。增施氮肥能显著增加玉米植株株高和干物重,水分适宜条件下中氮水平的玉米株高和干物重分别较低氮水平的增加10.4%和8.7%,而水分亏缺条件下株高和干物重均随施氮水平的增加而明显增加;水分亏缺条件下,中高量施钾能显著增加玉米植株干物重。水分适宜条件下增施氮肥能明显促进玉米对钾素的吸收,在水分适宜和亏缺条件下,不同氮水平的玉米钾素吸收均随施钾水平的增加而显著增加。     

Influence of drying temperature, water content, and heating rate on gelatinization of corn starches

The gelatinization properties of starch extracted from corn and waxy corn dried at different temperatures were determined at various water contents and heating rates by differential scanning calorimetry. All gelatinization transition temperatures increased with drying temperature and heating rate. Onset and peak temperatures remained relatively constant, whereas end temperature decreased in the presence of excess water. The gelatinization enthalpy (deltaH(g)) of corn starch decreased with drying temperature at 50% water; however, it remained constant for waxy corn starch. The effects of water content and heating rate on deltaH(g) were dependent on each other. The minimum water levels required for gelatinization of starch extracted from corn dried at 20 and 100 degrees C are 21 and 29%, respectively. The activation energy (E(a)) was calculated using an Arrhenius-type equation and two first-order models; the degree of conversion (alpha) was predicted using a newly proposed model that produced good results for both E(a) and alpha.     

Fortified cassava peel compost amendment for Amaranthus: Influence on plant growth,nutrients uptake and on soil nutrient changes

Nutrient supply through organic sources usually requires fortification for timely and optimum release of plant nutrients to achieve optimum crop performance. A pot experiment was conducted in a screen house to determine the optimum rate of cassava peel compost (CPC) fortification that supports optimum Amaranthus (Amaranthus cruentus L.) plant nutrient contents and residual soil nutrient contents. A compost of cassava peel and poultry manure was applied at 2.5; 5.0 and 7.5 t ha^?1each complemented with either 25 or 50 kg nitrogen (N), using nitrogen, phosphorus and potassium (NPK) 20-10-10 at 2 weeks before sowing Amaranthus. An unfertilized treatment served as control. Seeds were sown in plastic containers with a surface diameter of 24 cm filled with 5 kg soil, with a drain underneath. Seedlings were thinned to 4 plants/pot 2 weeks after planting. Plants were harvested at 5 weeks by ratooning and plant re-growth also harvested after 5 weeks. Soil pH was lower with high rates of 5.0 and 7.5 t ha^?1 CPC while the organic matter content was increased with increased CPC rate. Soil N was reduced but reflected in increased plant shoot and root N, with compost application. Soil P was generally increased but was not reflected in plant contents. Soil K contents were reduced and were reflected in increased plant contents. Application of 2.5 t ha^?1 CPC, fortified with either 25 or 50 kg N ha^?1 gave the optimum Amaranthus shoot nutrient contents with optimum residual soil nutrient contents.     

Influence of soil temperature and moisture on micronutrient supply,plant uptake,and biomass yield of wheat,pea, and canola

Abstract

Crop yield response to micronutrient fertilization is difficult to predict, particularly under unfavorable environmental conditions as these may alter both crop nutrient demand and the soil micronutrient supply to plant roots. The research objective was to evaluate the effect of various soil temperature and moisture conditions on crop growth response to added micronutrient copper (Cu), zinc (Zn), and boron (B) along with soil micronutrient supply and distribution among fractions. Brown and Dark Brown farm soils collected from southern Saskatchewan were used to grown wheat, pea and canola within controlled environment chambers. The biomass yields of all crops decreased under cold soil temperature and moisture stress (drought and saturated) conditions. Greater plant uptake of Cu, Zn, and B was associated with optimum (i.e., field capacity) soil moisture and warm temperature (23°C) growing conditions, compared to drought (i.e., 50% field capacity), saturated, and cold (5°C) temperature conditions. Environmental stress had the greatest impact on pea growth, reducing crop yield and micronutrient utilization efficiency more than 95%. Soil supplies of Cu and Zn were most negatively impacted by drought stress due to reduced mobility of these diffusion limited nutrients. The extractable micronutrients levels and chemical speciation fractions of Cu, Zn, and B indicating that bioavailability and micronutrient transformation were not affected during our short-term (i.e., six-weeks) study. However, it is suggested that assessments of micronutrient forms also be conducted on soil samples under actual moisture and temperature conditions as they exist in the experiment, as well as on dried, processed samples.     

Emissions of N2O from soils during cycles of freezing and thawing and the effects of soil water, texture and duration of freezing

Freezing and thawing influence many physical, chemical and biological processes in soils, including the production of trace gases. We studied the effects of freezing and thawing on three soils, one sandy, one silty and one loamy, on the emissions of N₂O and CO₂. We also studied the effect of varying the water content, expressed as the percentage of the water‐filled pore space (WFPS). Emissions of N₂O during thawing decreased in the order 64% > 55% > 42% WFPS, which suggests that the retardation of the denitrification was more pronounced than the acceleration of the nitrification with increasing oxygen concentration in the soil. However, emissions of N₂O at 76% WFPS were less than at 55% WFPS, which might be caused by an increased ratio of N₂/N₂O in the very moist conditions. The emission of CO₂ was related to the soil water, with the smallest emissions at 76% WFPS and largest at 42% WFPS. The emissions of CO₂ during thawing exceeded the initial CO₂ emissions before the soils were frozen, which suggests that the supply of nutrients was increased by freezing. Differences in soil texture had no marked effect on the N₂O emissions during thawing. The duration of freezing, however, did affect the emissions from all three soils. Freezing the soil for less than 1 day had negligible effects, but freezing for longer caused concomitant increases in emissions. Evidently the duration of freezing and soil water content have important effects on the emission of N₂O, whereas the effects of texture in the range we studied were small.