Residue Return Research Articles

Spatial distribution of soil nutrient at depth in black soil of Northeast China: a case study of soil available potassium

Spatial mapping of potassium is very urgently needed to develop economically and environmentally sound soil management plans, and deeper-layer soil available potassium (AK) resources on the farm are important for evaluating the long-term need for purchased K fertilizer. The objectives of this study are to analyze AK spatial distribution in deep soil depths from a small watershed, and to provide reference for farmers better managing fertilizer application and protecting environment in the farmland. In order to describe AK spatial distribution in deeper depths, six hundred and ten soil samples were collected from 122 soil profiles (0–60 cm) in a representative random sample method. Kriging procedures, correlation analysis and regression analysis were used to describe the spatial variability of soil AK in a small watershed from typical black soil of northeast China, and AK in cultivated field and forest (field returned to forest over 10 years) areas was compared. Gaussian models were recognized as the best for predicting AK in the soil at different layers. Spatial autocorrelations as influenced by human activities were weak for AK at 0–30, and 40–60 cm layers and was moderate at 30–40 cm, and autocorrelation distance (A0 = 3,110 m) is uniform at all layers. AK heterogeneity was different among soil layers, and was influenced by soil parent material, landscape, slope position, land use, soil management and so on in the watershed. The content of AK was 21.1–428.4 mg kg−1 in the cultivated areas and 117.2–401.0 mg kg−1 in the forest (field returned to forest over 10 years) in the entire profile (0–60 cm). AK in the forest areas were larger 18, 3, 22, 16 and 5 % in 0–20, 20–30, 30–40, 40–50 and 50–60 cm, respectively than in the farmland. AK variance in space decreased from the 0–20 to the 50–60 cm depth. The spatial pattern of AK was similar in all layers, and typically decreased from forest to surrounding farmland. AK also deceased along the water flow direction. Furthermore, AK was influenced by steepness, aspect, elevation, leading to the big difference between the two banks of the hydrographic reaches. In the field, AK was negatively correlated to gross soil loss and steepness at all depths, and became significant at the 0–20 cm depth, while it was significantly positively correlated to elevation except at the 40–50 cm depth. Generally, AK is sufficient for crop production for at least 160 year with a little potassium fertilizer application needed during the growing season in the study area. However, crop residue management and fertilizer application, especially manure and nitrogen application in special conditions (dry seasons, intensive cropping without residue return and so on) and sensitive areas (such as Low elevation, closer forest and so on) is still necessary in order to increase potassium storage and promote the efficiency of AK for plants.

Carbon sequestration efficiency in paddy soil and upland soil under long-term fertilization in southern China

Soil organic carbon (SOC) stock can be improved through the return of crop residues. However, the efficiency of C sequestered in soil (i.e., ΔSOC/ΔC input) might differ among crop systems. In this paper, we investigated the C input and SOC stabilization in paddy soil and upland soil under different long-term fertilization practices. Our objectives were to determine (i) the response of SOC stock to C input under different fertilization practices, and (ii) C sequestration efficiency in the two contrasting agroecosystems. The long-term fertilization experiment in paddy soil started in 1981, while the adjacent upland soil experiment commenced in 1986. Each experiment consists of 9 treatments: CK (no fertilization), N, P, K, NP, NK, NPK, 2NPK (double dose), and NPKOM (NPK plus organic manure). Physical SOC fractions (cPOM, silt+clay_f, fPOM, iPOM_m, silt+clay_m) were isolated by sieving, dispersion, and density flotation. Fertilization increased crop yield and C input, but it did not change the quality of SOC as revealed by CPMAS-13C NMR spectra. During the period of the experiment, SOC stock was improved by 6.7–15.3Mgha−1 in paddy soil for all fertilization practices, while in upland soil the CK, N, P, K, and NP fertilizations reduced the SOC by 1.2–3.8MgCha−1 and the other four fertilizations increased it by 0.5–7.4MgCha−1. The change in SOC was mainly ascribed to the POM fraction, whereas the two silt+clay sized fractions were independent of fertilization practice except the NPKOM treatment. At a given C input, the C sequestration efficiency was greater in paddy soil than in upland soil, which may be attributed to lower microbial activity but greater chemical (i.e., oxalate-soluble Fe) and physical stabilizations (i.e., soil structure) in paddy field. Our results indicate that paddy soil may sequester more SOC, with higher efficiency, than upland soil does.

Constraints of No‐Till Dryland Agroecosystems as Bioenergy Production Systems

Soil erosion and loss of soil organic C (SOC) may limit the sustainable harvest of crop residues for biofuels from dryland systems in the semiarid Great Plains. The objective of this study was to evaluate the capabilities and constraints of harvesting residues from dryland systems. The study used observations from a long‐term experiment in Colorado to examine biomass production from wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum [Sorghum bicolor (L.) Moench] at three no‐till sites in a winter wheat–corn–fallow (WCF) or winter wheat–sorghum–fallow cropping system. Modeling evaluated the impact of residue removal on erosion rates and SOC dynamics. The Revised Universal Soil Loss Equation and the Wind Erosion Equation were used to simulate erosion, and the DAYCENT model was used to estimate changes in SOC with residue removal. Biomass yield for WCF averaged 3.8 Mg ha−1, divided into stover and grain yields of 2.2 and 1.6 Mg ha−1. Water erosion was not shown to constrain residue harvest, but modeling indicated unsustainable wind erosion rates after removing 10 to 30% of corn residue. Simulations showed that up to 80% of wheat straw could be harvested without exceeding sustainable wind erosion rates. The major constraint to sustainable residue harvest is a residue return rate of 2.4 Mg ha−1 yr−1 of biomass to maintain SOC.

Effect of Cut Plant Residue Management and Fertilization on the Dry-Matter Yield of Swards and on Carbon Content of Soil

The goal of this research was to study the impact of cut plant residues, returned to or removed from the grassland sward, on the dry-matter yield of swards and on the organic carbon (Corg) concentration of soil. The experiment was carried out during 2004–2008. The variables of the experiment were (i) sward type: turfgrass sward (Festuca rubra rubra and Poa pratensis) and grass–clover sward (Phleum pratense, Lolium perenne, and Trifolium repens) and (ii) treatment of residues: the cut plant residues were returned (RRT) to the plots or removed (RRM) from the plots after the mowing. The fertilizer treatments were as follows: N0P0K0, N80P11K48, N160P22K96, and N400P56K240 kg ha−1 for the turfgrass sward and N0P0K0 and N80P26K50 kg ha−1 for the grass–clover sward. The Corg and Ntot concentrations in the 20-cm soil layer were measured at the beginning and at the end of the experiment at depths of 0–5 cm and 5–20 cm. Nitrogen was returned as plant residues to the grass–clover sward in treatment N0P0K0 at 190 kg ha−1 and N80P26K50 at 204 kg ha−1 and consequently the returned cut plant residues increased the yield by 31% and 22%, respectively. The amount of N returned as residues to turfgrass sward was 31–236 kg ha−1 but it had no significant influence on the sward dry-matter yield. During the 5 years of the experiment the Corg content in 0- to 5-cm soil layer of grass–clover sward in treatment RRT increased by 42.9% and in RRM by 32.0% as an average of both fertilization treatments. At the depth 5–20 cm the Corg concentration did not change in treatment RRT, but in treatment RRM with fertilization the Corg concentration decreased by 8.2%. In turfgrass soil the Corg concentration increased in RRT treatment by 21.6% and in treatment RRM by 7.2% during 5 years. In the lower soil layer the concentration of Corg decreased with removal and return of plant residues. The fertilization did not influence the changes of Corg concentration in turfgrass swards soil.

Estimation of possible energy contributions of crop residues in Nigeria

This study applied a simple methodology to evaluate energy contribution of selected crop residues to the possible replacement of conventional sources of energy and their specific technologies based on Nigerian situations. Using this methodology, energy content, replacement energy value, energy cost and energy return of crop residue (kJ per kg dry matter) were considered. The cost estimates of these residues using 2008 crops production data vary from US$6.45/tonne to US$23.12/tonne, depending on the type of crop residue and the transportation distance. Estimation of values of energy from maize stover, cassava peels, millet stover and sorghum straw showed that about 30 million tonnes are energetically available in Nigeria in 2010 and could replace 1.05 PJ/year if they were used exclusively for heat generation by direct combustion, or 0.58 PJ/year if used in gasification processes to generate electricity and replace the energy currently supplied by the national grid.

The effects of composted pineapple residue return on soil properties and the growth and yield of pineapple

A field experiment was conducted to investigate the influence of composted pineapple residue return (CPRR) on soil bio-chemical properties and the growth performance of next-cropped pineapple plants. The results suggested that CPRR markedly decreased the soil bulk density and increased the contents of available P and K. CPRR significantly increased the abundance of bacteria and actinomycetes, and the activities of catalase, acid phosphatase and invertase in the soil were notably heightened. Growth characteristics, including the plant height, length of leaves and roots, leaf width, number of leaves and fresh weight of the aboveground and belowground parts were significantly increased by CPRR. The contents of chlorophyll, soluble sugars, and soluble protein, as well root vigor were also markedly increased. CPRR also increased the fruit transverse and longitudinal diameters, weight and yield of next-cropped pineapple.

秸秆还田与施肥对稻田土壤微生物生物量及固氮菌群落结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 秸秆还田与施肥对稻田土壤微生物生物量及固氮菌群落结构的影响 DOI: 10.5846/stxb201205290788 作者: 作者单位: 四川农业大学资源环境学院微生物系,四川省农业科学院土壤肥料研究所,四川省农业科学院土壤肥料研究所,四川农业大学资源环境学院微生物系,四川农业大学资源环境学院微生物系,四川农业大学资源环境学院微生物系 作者简介: 通讯作者: 中图分类号: 基金项目: 农业部公益性行业(农业)科研专项资助(201003016) Effect of different fertilizer combinations and straw return on microbial biomass and nitrogen-fixing bacteria community in a paddy soil Author: Affiliation: College of Resources and Environment,Sichuan Agricultural University,Soil and Fertilizer Institute,Sichuan Academy of Agricultural Sciences,Soil and Fertilizer Institute,Sichuan Academy of Agricultural Sciences,College of Resources and Environment,Sichuan Agricultural University,College of Resources and Environment,Sichuan Agricultural University,College of Resources and Environment,Sichuan Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用氯仿熏蒸法和变性梯度凝胶电泳法(PCR-DGGE)研究了秸秆覆盖还田与施肥对灰棕冲积水稻土0-10cm和10-20cm土层土壤微生物生物量碳、氮和固氮菌群落结构的影响。结果表明:土壤微生物量碳、氮和固氮菌多样性从0-10cm土层到10-20cm土层均呈现降低趋势。无秸秆覆盖处理(对照组)的土壤微生物生物量碳(SMB-C)和微生物生物量氮(SMB-N)量最小。在秸秆覆盖还田处理中,低氮和无钾处理的SMB-C和SMB-N都显著低于全量氮磷钾肥处理。虽然无磷处理的SMB-N低于全量氮磷钾处理, 但差异不显著。说明秸秆覆盖还田配施充足氮磷钾肥能显著提高土壤微生物生物量碳、氮。由DGGE图谱多样性指数分析得知,配施充足氮磷钾肥的处理土壤的固氮菌多样性最丰富。UPGMA聚类分析显示,10种不同处理的聚类图也不同,对照(无秸秆)处理0-10cm和10-20cm的微生物不同于其它处理单独聚在了一个群里。DGGE条带测序得知,14个条带的近缘种大部分为非培养细菌nifH基因片段,主要优势菌群其归属于变形菌门(Proteobacteria)的β-变形菌纲(Betaproteobacteria)。应用PCR-DGGE技术可以解释灰棕冲积水稻土秸秆覆盖不同肥料用量固氮菌分子群落结构特点。 Abstract:Chloroform fumigation and denaturing gradient gel electrophoresis(DGGE) were employed to study the influence of different fertilizer treatments with crop residue return on microbial biomass and nitrogen-fixing bacteria community in a gray brown alluvial paddy soil at soil depth of 0-10 cm and 10-20cm. Results show that soil microbial biomass carbon (SMB-C), microbial biomass nitrogen (SMB-N) and diversity of nitrogen-fixing bacteria decreased with soil depths. The control treatment with straw removal had the lowest amounts of SMB-C and SMB-N. Among the treatments receiving straw return, the quantity of SMB-C and SMB-N in the treatments with low nitrogen rate and omitting was significantly lower than the full rate NPK treatment. Omission of phosphate on the basis of NPK nonsignificantly reduced the SMB-N compared to the NPK treatment. It shows that straw mulching with addition of adequate NPK fertilizers can significantly increase the SMB-C and SMB-N. The diversity indices of DGGE profiles indicate that the treatment with adequate NPK had the most abundant nitrogen-fixing bacterial diversity. According to UPGMA cluster analysis, dendrogram of the 10 treatments were different, and the micro-organisms at the 0-10cm and 10-20cm in the control treatment differed from all the other treatments and stood alone in a separate group. DGGE bands sequencing further revealed that the 14 closely related species were largely uncultured bacteria nifH gene fragment with the predominant community falling in the class of Proteobacteria in Betaproteobacteria. Application of PCR-DGGE can well interpret the community structure characteristics of the nitrogen-fixing bacteria molecules in the gray-brown alluvial paddy soil with straw return and different fertilizer treatments. 参考文献 相似文献 引证文献

Effect of optimal irrigation, different fertilization, and reduced tillage on soil organic carbon storage and crop yields in the North China Plain

AbstractThe objective was to evaluate the effect of different agricultural managements on soil organic C (SOC) storage and crop yields in the North China Plain (NCP). The study was conducted at five experimental stations. Different agricultural managements were designed, including optimal (OPT) and conventional (CON) irrigation and fertilization treatments, different amounts of fertilization application and residue‐return treatments, and different tillage practices. Compared to the CON treatment, SOC storage in the 1 m soil profile under the OPT treatment increased by 2 t ha–1, 8 t ha–1, and 4 t ha–1 at Quzhou, Wuqiao, and Dongbeiwang sites, respectively. The annual increasing rate of SOC storages in the topsoil (0–30 cm) under the OPT treatments at Wuqiao (0.88 t ha–1 y–1), Quzhou (0.93 t ha–1 y–1), and Dongbeiwang (1.86 t ha–1 y–1) were higher than those in the CON treatments at Wuqiao (0.15 t ha–1 y–1), Quzhou (0.54 t ha–1 y–1), and Dongbeiwang (0.28 t ha–1 y–1), but the difference of grain yields between the two treatments was not significant. The SOC storage in 1 m soil profile in the no‐tillage treatment with standing residue return (NT1) at Luancheng increased by 5 t ha–1 and 7 t ha–1 compared with rotary‐tillage (RT) and conventional‐tillage (CT) treatments, respectively, but the crop yield under no‐tillage treatment was the lowest. While at Quzhou site, it increased by 3 t ha–1 in the top 40 cm soil under the NT treatment compared to the CT treatment. The annual increasing rate of SOC storage in the top 30 cm under NT treatment was also the highest (1.08 t ha–1 y–1 at Luancheng, 1.86 t ha–1 y–1 at Quzhou), compared to the other tillage treatments. At Henghsui site, the combination of the highest fertilization application and highest residue‐return treatments got the highest SOC storage and the highest crop yields. We concluded that the agricultural management practices, such as optimal irrigation and fertilization treatment, the higher fertilization, residue return and RT, has significant impact on the SOC storage and agricultural sustainability in the NCP.

Management effects on bioenergy sorghum growth, yield and nutrient uptake

Bioenergy sorghum (Sorghum bicolor L. Moench.) productivity and nutrient uptake may be affected by cropping sequence complexity, fertilization, and residue removal. The goal of this research was to optimize the efficiency of crop management in high biomass (bioenergy) sorghum systems. The two-year field study was conducted in two diverse locations near College Station and Weslaco, Texas. The study utilized a complete factorial design with four replications of the following factors: Rotation: continuous biomass sorghum vs. biannual rotation with corn (Zea mays L.); Stover Return: 0, 25, 50% of the sorghum biomass and all corn stover; and N Rate: 0 vs. non-limiting N. The bioenergy sorghum used was a high-yield photoperiod-sensitive hybrid. Other inputs and practices were those commonly used in the respective areas. Sorghum was harvested for yield, and C, N, P and K, were determined. Rotation, fertilization, and residue return affected yields, plant growth, and nutrient uptake (p < 0.05). Total yields, C, N, P, and K uptake in sorghum were significantly increased by rotation and N fertilization both years, while 25% residue return increased sorghum yield and N uptake at College Station the first year. Uptake of C, N, P and K were increased by N fertilization. Sorghum tissue concentrations of N, P and K declined from the first to the second year although mean yield increased, possibly indicating decreased soil nutrient availability after only two years. A regression equation was developed relating biomass yield and site, rotation, nitrogen rate, and plant physical traits (R2 = 0.67).

Erosion-induced CO2 flux of small watersheds

Soil erosion not only results in severe ecological damage, but also interferes with soil organic carbon formation and decomposition, influencing the global green-house effect. However, there is controversy as to whether a typical small watershed presumed as the basic unit of sediment yield acts as a CO2 sink or source. This paper proposes a discriminant equation for the direction of CO2 flux in small watersheds, basing on the concept of Sediment Delivery Ratio (SDR). Using this equation, watersheds can be classified as Sink Watersheds, Source Watersheds, or Transition Watersheds, noting that small watersheds can act either as a CO2 sink or as a CO2 source. A mathematical model for calculating the two discriminant coefficients in the equation is set up to analyze the conditions under which each type of watershed would occur. After assigning the model parameter values at three levels (low, medium, and high), and considering 486 scenarios in total, the influences are examined for turnover rate of the carbon pool, erosion rate, deposition rate, cultivation depth and period. The effect of adopting conservation measures like residue return, contour farming, terracing, and conservation tillage is also analyzed. The results show that Sink Watersheds are more likely to result in conditions of high erosion rate, long cultivation period, high deposition rate, fast carbon pool turnover rate, and small depth of cultivation; otherwise, Source Watersheds would possibly occur. The results also indicate that residue return and conservation tillage are beneficial for CO2 sequestration.

Impact of crop patterns and cultivation on carbon sequestration and global warming potential in an agricultural freeze zone

Agricultural activity is a primary factor contributing to global warming. In higher latitude freeze zone, agricultural activities pose a more serious threat to global warming than other zones. The crop management practices of various land use types have direct impacts on soil organic carbon (SOC) and global warming potential (GWP). Crop variations and cultivation practices are two important factors affecting carbon sequestration and the exchange of greenhouse gases between soils and the atmosphere. This exchange has special characteristics in the freeze zone. In this paper, the impact of crop patterns and cultivation management (i.e., residue return rate, manure amendment, and chemical N fertiliser application) on SOC and GWP in an agricultural freeze zone was analysed. The Denitrification–Decomposition (DNDC) model was employed to predict the long-term dynamics of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) for dryland and paddy rice systems. The CO2-equivalent index was used to express the GWP response of N2O, CH4 and CO2. The simulated results indicated that the manure amendment and N fertiliser application can improve the SOC, increase crop production and enhance the GWP. The cultivation of returning residue to the soil is the win–win solution for SOC conservation and GWP control. It was found that paddy rice was preferable to dryland for sequestering atmospheric CO2 and mitigating global warming. This analysis also indicated that the DNDC model is a valid tool for predicting the consequences of SOC and GWP changes in cropland agroecosystems in the freeze zone.

长期施肥对稻田土壤固碳功能菌群落结构和数量的影响

CO2 fixation is the central mechanism of primary production in almost all ecosystems,and plays a major role in regulating the concentration of atmospheric CO2.Carbon dioxide accounts for about 50% of the current global warming potential.Soil microorganisms that assimilate CO2 are widely distributed,and have a great ability to adapt to environmental extremes,such as within volcanic sediments,lake wetlands and the submarine realm.Microbial CO2 assimilation is of great significance to climate change mitigation and sustainable development for human beings. It has now been well established that atmospheric concentration of CO2 can be reduced significantly by adopting management practices to enhance CO2 sequestration(storage) in cropland soils.Among the approaches for increasing CO2 sequestration of croplands are soil fertilization management practices,such as returning crop residues to the soil,planting temporarily retired land with grass for stabilization,and integrating nutrient management strategies to diversified cropping systems. Paddy soils are distributed widely throughout the world,and generally are known for their production of greenhouse gasses(N2O and CH4).Numerous studies have used molecular techniques to investigate these microbial driving mechanisms.However,few studies have addressed the importance of microbial CO2 fixation processes in paddy soils.Investigation of the impacts of long-term fertilization on the structure and abundance of CO2 assimilating bacteria in paddy soils can provide a theoretical basis for the application of information on fertilization of paddy-rice fields.This type of research also may benefit the reduction of greenhouse gas emissions and increase carbon sequestration. Although carbon fixating microorganisms exhibit a wide range of physiological and ecological traits,most photo-and chemoautotrophic bacteria use ribulose-1,5-biphosphate carboxylase/oxygenase(RubisCO),which catalyzes the first rate-limiting step in the Calvin cycle to incorporate atmospheric CO2.The cbbL gene,which encodes the large subunit of the form I RubisCO is especially useful as a functional marker for significant phylogenetic analyses of CO2 fixating microorganisms in different ecological systems. In this study,soil samples were collected from a long-term fertilization experiment,which included a station that received no fertilization(CK),one treated with chemical fertilization(NPK),and one with NPK plus crop residue return(NPKS).The abundance,diversity,and composition of soil-CO2 fixating bacteria were determined using Polymerase Chain Reaction(PCR),cloning and sequencing,and real-time quantitative PCR of the cbbL gene to explore the effects of long-term fertilization on the structure and abundance of the CO2 fixation bacterial community.Based on sequence libraries of cbbL genes,our results clearly demonstrate that there was a significant response difference in community composition with respect to long-term fertilization regimes.A total of 165 cbbL genotypes from three different treatment soils were divided into 14 bacterial cbbL gene phylotypes,mainly including Bradyrhizobium,Ralstonia,and Thiobacillus.Facultative autotrophic bacteria,such as Bradyrhizobium and Ralstonia,dominated both in NPK and NPKS treatment soils,while growth of the obligate autotrophic bacteria,such as Thiobacillus and Nitrosospira,were suppressed.LUBSHUFF statistical analyses also demonstrated that cbbL gene libraries of CK,NPK and NPKS treatments were significantly different from one another.The Rarefaction curve indicated that fertilizer addition increases cbbL gene diversity.Thus,the NPK treatment had the highest curve.The abundance of the bacterial cbbL gene ranged from 3.35×108—5.61×108 copies g-1 soil.Crop residue return NPKS had the highest abundance of bacterial cbbL gene,which was about one half the value of CK.Finally,application of chemicals and organic fertilizers in paddy ecosystems significantly influenced the CO2 fixating bacterial community structure,and increased bacterial abundance and diversity.These results provide a strong basis for further investigation of fertilization on soil carbon sequestration potential and its related microbial mechanisms.

Purification of Active Peroxidase Isoenzymes and Their Responses to Nitrogen Fertilization and Rotation of Biomass Sorghum

Peroxidases (EC 1.11.1.7) participate in lignin biosynthesis. But peroxidation is not a tool for assaying lignocellulose metabolism because the active cannot yet be separated from the inactive peroxidases. A biochemical tool for assaying plant cell wall responses to agronomic practices is needed in the lignocellulosic feedstock renewable energy industry. Peroxidase of biomass sorghum was purified to 9 - 13 charge isomers by free solution IEF (Rotofor) technique. Free solution IEF was more effective than chromatographic purification of active peroxidase isoenzymes. Native PAGE separated each charge isomer to three anionic and three cationic isoenzymes. Hydrogen peroxide and o-dianisidine assays showed that only 20% - 30% of the isoenzymes displayed normal Michaelis-Menten kinetics. Sorghum planted without nitrogen fertilization induced the hydrogen peroxide noncompetitive inhibition of peroxidase, but 280 kg·ha–1 nitrogen fertilization and 100% sorghum mineral residue return to the soil tripled the concentration of active peroxidase and relieved the inhibition with concomitant increases of 350 kg lignin and 3532 kg·cellulose·ha–1. Nitrogen fertilization without crop rotation induced hydrogen peroxide inhibition of the peroxidase, but nitrogen fertilization and 25% sorghum rotation changed the PI of the active peroxidase from neutral to mildly acidic and relieved the inhibition with concomitant enormous increases of 690 kg lignin and 7151 kg·cellulose·ha–1. Hydrogen peroxide inhibition kinetics is consistent with the known peroxidase-substrate intermediate dead-end complex formation. Lignocellulosic yield was greatest under the agronomic management that combined 280 kg·ha–1 nitrogen fertilizer with 25% sorghum residue, which resulted in a shift of pI value of the active peroxidase due to a reduction in the Km value of the peroxidase. Therefore, up to 75% of sorghum biomass rather than only 50% can be harvested for conversion to bioenergy products.

No tillage in rainfed Aragon (NE Spain): Effect on organic carbon in the soil surface horizon

Conservation tillage has been encouraged as a management alternative to preserve soil and water resources in semiarid Aragon (NE Spain). In fact, its adoption by farmers, and especially of no tillage (NT) systems, has increased in recent years. However, little information concerning the soils on which these techniques are applied is available for this region. The objective of this study was to assess the potential of NT to increase organic carbon content at the soil surface (0–20 cm) in rainfed Aragon. To this aim, 22 pairs of adjacent farm fields under NT and conventional tillage (CT) were compared in different cereal production areas. The fields were under continuous NT between 5 and 19 years but half were over 10 years. Soil organic carbon (SOC) in NT ranged from 7.06 to 18.53 g kg −1 (0–20 cm depth) and was higher than 12 g kg −1 in nearly 30% of the fields. These contents represented between 8% less (only one case) and 55% more SOC under NT than under CT with an average gain of 20% in favour of NT. The highest SOC contents were found in the NT fields of longer duration (>10 years) and/or managed with practices that enhance the return of more crop biomass to the soil (complete residue return, cropping intensification and manure application). The identification of the current management practices used by farmers has allowed us to know the diversity of the NT-based cropping systems and the reality of the conservation agriculture in our region. Overall, results from this on-farm study indicate that NT can be recommended as a viable alternative to CT to increase organic carbon at the soil surface in cereal production areas of Aragon.

Modeling impacts of farming management practices on greenhouse gas emissions in the oasis region of China

Abstract. Agricultural ecosystems are major sources of greenhouse gas (GHG) emissions, specifically nitrous oxide (N2O) and carbon dioxide (CO2). An important method of investigating GHG emissions in agricultural ecosystems is model simulation. Field measurements quantifying N2O and CO2 fluxes were taken in a summer maize ecosystem in Zhangye City, Gansu Province, in northwestern China in 2010. Observed N2O and CO2 fluxes were used for validating flux predictions by a DeNitrification-DeComposition (DNDC) model. Then sensitivity tests on the validated DNDC model were carried out on three variables: climatic factors, soil properties and agricultural management. Results indicated that: (1) the factors that N2O emissions were sensitive to included nitrogen fertilizer application rate, manure amendment and residue return rate; (2) CO2 emission increased with increasing manure amendment, residue return rate and initial soil organic carbon (SOC); and (3) net global warming potential (GWP) increased with increasing N fertilizer application rate and decreased with manure amendment, residue return rate and precipitation increase. Simulation of the long-term impact on SOC, N2O and net GWP emissions over 100 yr of management led to the conclusion that increasing residue return rate is a more efficient method of mitigating GHG emission than increasing fertilizer N application rate in the study area.

Carbon sequestration potential of recommended management practices for paddy soils of China, 1980–2050

China's rice paddies, accounting for 19% of the world's total, play an important role in soil carbon (C) sequestration. In order to reduce uncertainties from upscaling spatial processes of the DeNitrification–DeComposition (DNDC) model for improving the understanding of C sequestration under recommended management practices (RMPs), we parameterized the DNDC model with a 1:1,000,000 polygonal soil database to estimate how RMPs influence potential C sequestration of the top 30 cm of Chinese paddy soils and to identify which management practices have the greatest potential to increase soil organic carbon (SOC) in these soils. These practices include reduced/no tillage, increasing crop residue return, and increasing manure applications. A baseline and eleven RMP scenarios were projected from 2009 to 2080, including traditional and conservation tillage, increasing crop residue return, increasing manure incorporation, and the combination of these practices. The results indicated that C sequestration potential under modeled RMPs increased compared to the baseline scenario, and varied greatly from 29.2 to 847.7 Tg C towards the end of the study period with an average rate of 0.7 to 20.2 Tg C yr − 1 . In general, increasing crop residue return was associated with higher rates of C sequestration when compared to increasing manure application or practicing conservation tillage. The simulations demonstrated that the most effective soil C sequestration strategy probably involves the implementation of a combination of RMPs, and that they vary by location.

Long term nitrogen fertilization: Soil property changes in an Argentinean Pampas soil under no tillage

The main objective of nitrogen (N) fertilization is to achieve high yields and/or to increase grain quality. However, nutrient application may affect soil processes and cycles. These could involve increases in crop residues return to soil, changes in soil organic matter dynamic, NO 3 −-N content and pH decrease. The aim of this study was to determine the effect of N application on: crop residue input, soil organic carbon (SOC) and N (SON), their particulate (POC and PON) and mineral associated (AOC and AON) fractions, mineralizable N (anaerobic incubations, AN), and pH on a Molisoll of the southern Buenos Aires Province under no tillage (NT). A long-term crop rotation experiment has been conducted between 2001 and 2008 on a complex of Typic Argiudoll and Petrocalcic Paleudoll soils at Balcarce, Argentina (37°45′S, 58°18′W). Three N rates (N0, N1 and N2) were evaluated, with an average N input of 0, 57 and 105 kg ha −1 year −1, respectively. Crop sequence was integrated by maize ( Zea mays L.), soybean ( Glycine max (L.) Merr.) and wheat ( Triticum aestivum L.)/soybean double crop. Soil sampling was done in 2008, previous to maize planting. Nitrogen fertilization increased carbon (C) return to soil during 2001–2008 (11.1 and 18.7% for N1 and N2 respect to N0) but no differences in SOC, SON, AOC, and AON were observed among N rates in 0–5 and 0–20 cm depth. It was only found more PON in N1 and a slight tendency to increased POC (3% and 13% for N1 and N2 respect to N0) in 0–5 cm depth. At the same time, NO 3 −-N content in 0–60 cm depth was similar among N rates (89.6 ± 8.4, 88.6 ± 6.4, and 81.6 ± 10.3 kg N ha −1 for N0, N1, and N2, respectively). By contrast, it was determined soil acidification (5.8 ± 0.3, 5.5 ± 0.2, and 5.3 ± 0.2 for N0, N1, and N2, respectively) and AN reductions in 0–5 cm depth as N rate increased, (76.1 ± 3.2; 74.9 ± 6.3 and 57.9 ± 3.5 for N0, N1 and N2 respectively). The high frequency of soybean in the rotation could have prevented higher increases in C return to soil and, as a consequence, mitigated the changes in related soil properties. In addition, the absence of N application to soybean also could have prevented enhances in soil acidification and AN depletion.

The Sanborn Field Experiment: Implications for Long‐Term Soil Organic Carbon Levels

With the potential for generating biofuels from crop residues, many scientists and policymakers are seeking data on what would be the long‐term influence of biomass removal on soil organic matter levels. This paper shares the experience of 100 yr of various cropping systems management applications to soil organic carbon (SOC) levels on historic Sanborn Field. Established in 1888, Sanborn Field has employed monocultures and crop rotations to assess the influence of various treatments on crop yield, changes in soil properties, and long‐term sustainability. Soil samples to nearly 1 m from 1915, 1938, 1962, and 1988 for selected cropping management practices were analyzed for SOC. In the initial design of the plot plan, residues from Sanborn Field were removed from plots to simulate the use of these materials in an animal production system. In 1950 the management program was changed to return residues to each specific plot and for increased utilization of N fertilizers. Little increase in SOC was observed in samples from 1962, 12 yr after the return of residues. In many systems, surface SOC decreased from 1915 to 1962 with an increase for the 1988 samples. After initiation of residue return, manure only treatments nearly returned to 1915 SOC contents in the surface soil. This increase was a result of the nutrients from the manure in concert with the residues. SOC distribution over the time period for rotations did not follow the patterns of monocultures. It appears that an equilibrium level of SOC for some cropping systems takes about 30 to 40 yr to develop. Initial active carbon (AC) content assessment as a proxy for soil quality shows greater AC with manure and higher input management systems. The AC had a wide seasonal flux within a growing season as a function of temperature and moisture fluxes on microbial activity.

Greater Mitigation of Climate Change by Organic than Conventional Agriculture: A Review

ABSTRACT Organic agriculture is an alternative production system that avoids the use of synthetic pesticides and fertilizers, and relies on biological pest control and on crop rotation, green manure and composts to maintain soil fertility. Although many comparisons have been made between organic and conventional agriculture in terms of crop yields, economic returns and other factors, only a few studies have compared their effects on mitigating climate change. The present review compares the effectiveness of organic and conventional agriculture in mitigating climate change. The review reveals that organic agriculture has a greater potential for mitigating climate change, largely due to its greater ability in reducing emissions of greenhouse gases (GHGs) including carbon dioxide, nitrous oxide (N2O) and methane (CH4). It also increases carbon sequestration in soils compared with that of conventional agriculture. In addition, many farming practices commonly adopted in organic agriculture such as rotation with leguminous crops, minimum or no tillage, and the return of crop residues favour the reduction of GHGs and the enhancement of soil carbon sequestration. The certification of farming practices as required in organic agriculture provides a transparent guarantee of organic principles and standards. This also allows the enforced adoption of new and effective practices aimed at improving the mitigation of climate change. Furthermore, organic agriculture is highly adaptable to climate change compared with conventional agriculture. However, greater recognition of the potential of organic agriculture for mitigating climate change is needed. At present, this recognition depends on the ability of organic yields to out-perform conventional yields, which has been shown to occur in developing countries. More research is needed to improve organic yields in developed countries and to improve the potential of mitigating climate change by organic agriculture. Future strategies for improving the effectiveness of organic agriculture in mitigating climate change are presented and discussed.

Post-harvest residue management effects on recalcitrant carbon pools and plant biomarkers within the soil heavy fraction in Pinus radiata plantations

Forest soils contain about 30% of terrestrial carbon (C) and so knowledge of the influence of forest management on stability of soil C pools is important for understanding the global C cycle. Here we present the changes of soil C pools in the 0–5 cm layer in two second-rotation Pinus radiata (D.Don) plantations which were subjected to three contrasting harvest residue management treatments in New Zealand. These treatments included whole-tree harvest plus forest floor removal (defined as forest floor removal hereafter), whole-tree, and stem-only harvest. Soil samples were collected 5, 10 and 15 years after tree planting at Kinleith Forest (on sandy loam soils) and 4, 12 and 20 years after tree planting at Woodhill Forest (on sandy soils). These soils were then physically divided into light (labile) and heavy (stable) pools based on density fractionation (1.70 g cm−3). At Woodhill, soil C mass in the heavy fraction was significantly greater in the whole-tree and stem-only harvest plots than the forest floor removal plots in all sampling years. At Kinleith, the soil C mass in the heavy fraction was also greater in the stem-only harvest plots than the forest floor removal plots at year 15. The larger stable soil C pools with increased residue return was supported by analyses of the chemical composition and plant biomarkers in the soil organic matter (SOM) heavy fractions using NMR and GC/MS. At Woodhill, alkyl C, cutin-, suberin- and lignin-derived C contents in the SOM heavy fraction were significantly greater in the whole-tree and stem-only harvest plots than in the forest floor removal plots in all sampling years. At Kinleith, alkyl C (year 15), cutin-derived C (year 5 and 15) and lignin-derived C (Year 5 and 10) contents in the SOM heavy fraction were significantly greater in stem-only harvest plots than in plots where the forest floor was removed. The analyses of plant C biomarkers and soil δ13C in the light and heavy fractions of SOM indicate that the increased stable soil C in the heavy fraction with increased residue return might be derived from a greater input of recalcitrant C in the residue substrate.