Qualitative and quantitative differences in particulate organic matter fractions in organic and conventional farming systems

To quantify functionally important differences in soil organic matter (SOM) that result from use of different farming practices, soils from 9 long-term trials comparing manure+legume-based organic, legume-based organic, and conventional farming systems were collected and particulate organic matter (POM) was fractionated to reflect its position within the soil matrix. The free, light POM (FPOM; <1.6 g cm⁻³) not occluded within aggregates and occluded POM (OPOM; <2.0 g cm⁻³) were compared to an undifferentiated POM fraction (coarse fraction, CF; >53 μm) obtained by wet sieving. Fraction C, N, and hydrolyzable N (quantified using the Illinois test (IL-N)) were determined. Organic farming systems had greater quantities of C and N in the OPOM and CF and, greater IL-N contents in all POM fractions considered. The OPOM's C:N ratio (16-19) and was least in the manure+legume-based organic, intermediate in the legume-based organic, and greatest in the conventional systems (P<0.10). Trends in OPOM C:N and IL-N abundance suggested occluded POM was most decomposed, and possibly a greater N reservoir, in the manured soils. The FPOM quality reflected the residues added to each system and its removal improved resolution of quality-based differences in POM associated with long-term management. Subdivision of POM revealed differences in its quality that were not evident using the undifferentiated CF. Quantification of hydrolysable N (IL-N) in POM did not enhance our understanding of management's affect on SOM quality. This multi-site comparison showed organic management simultaneously increased the size of the labile N reservoir and the amount of POM protected within aggregates; and that, occluded POM is more decomposed in manure+legume- than in legume-based organic systems. The characteristics of POM reveal how organic practices improve SOM and suggest the nutrient and substrate decay dynamics of organic systems may differ as a result of the N fertilization strategies they employ.     

Effects of organic versus conventional arable farming on soil structure and organic matter dynamics in a marine loam in the Netherlands

Abstract. We compared the effects of conventional and organic arable farming on soil organic matter (SOM) content, soil structure, aggregate stability and C and N mineralization, which are considered important factors in defining sustainable land management. Within one soil series, three different farming systems were selected, including a conventional and an organic arable system and permanent pasture without tillage. The old pasture represents optimal conditions in terms of soil structure and organic matter inputs and is characterized by high earthworm activity. More than 70 years of different management has caused significant differences in soil properties. SOM content, mineralization, earthworm activity and water-stable aggregation decreased as a result of tillage and arable cropping when compared with pasture, but were significantly greater under organic farming than under conventional farming. Total SOM contents between 0 and 20 cm depth amounted to 15, 24 and 46 g kg⁻¹ for the conventional arable, organic arable and permanent pasture fields, respectively. Although less sensitive to slaking than the conventionally managed field, the soil under organic farming was susceptible to compaction when high pressures were exerted on the soil under wet conditions. The beneficial effects of organic farming are generally associated with soil biochemical properties, but soil physical aspects should also be considered. Depending on soil type and climate, organic farmers need to be careful not to destroy the soil structure, so that they can enjoy maximum advantage from their organic farming systems.     

Carbon and nitrogen stocks and their mineralization potentials are higher under organic than conventional farming practices in Japanese Andosols

ABSTRACT

This study aimed at understanding whether and how long-term organic rice farming affects soil carbon (C) and nitrogen (N) stocks and their mineralization potentials in submerged rice paddies in Tochigi, Japan. An incubation experiment was carried out to assess the impacts of internal nutrient cycling after organic farming (OF) for 4–5 years (4OF), 8–9 years (8OF), and 12 years (12OF), compared with a conventional rice field (CF). Soil samples were collected at 0–15 cm and 15–20 cm in flooded rice fields after harvest in October 2013. pH and bulk density at 0–15 cm were significantly lower in 12OF fields than in CF fields (by 0.22 unit pH and 17.5%, respectively). Compared with CF, 12OF fields showed significant differences in soil organic carbon (SOC) and total nitrogen (TN), but 4OF and 8OF fields did not. In 8OF fields, the C decomposition (Co) and N mineralization (No) potentials were significantly higher (by 34.0% and 35.6%, respectively, at 0–15 cm, and by 67.1% and 24.5% at 15–20 cm) than in CF fields. Similarly, in 8OF fields at 0–15 cm, the Co:SOC and No:TN ratios were 19.8% and 23.2% higher, respectively, than in CF fields. Co, No, Co:SOC, and No:TN in 12OF fields were higher than those in CF fields, demonstrating the effects of prolonged organic rice farming. Additionally, in 12OF fields, C and N stocks were significantly higher (by 15.5% and 17.2%, respectively, at 0–15 cm, and by 4.8% and 12.1% at 15–20 cm) than in CF fields. Our findings suggest that long-term organic rice farming increases soil C and N stocks as well as C and N mineralization in Japanese Andosols.     

Development of soil organic matter stocks under different farm types and tillage systems in the Organic Arable Farming Experiment Gladbacherhof

In 1998, the Organic Arable Farming Experiment Gladbacherhof (OAFEG) was started in order to explore the impact of different organic arable production systems (mixed farming, stockless farming with rotational ley, stockless cash crop farming) and of different tillage intensities (conventional plough as a full inversion tillage, two-layer plough, inversion tillage at reduced depth, non-inversion tillage) on sustainability parameters. In this article, we present results on the development of soil organic matter (SOM) levels. Starting with organic mixed farming with approximately 0.7 livestock units (LU) per ha cattle before set-up of the experiment, only the mixed farming system in the experiment was able to maintain SOM levels. The stockless system with ley maintained soil organic carbon (SOC), but lost soil total nitrogen (STN), and the stockless cash crop system had a significant SOM loss in the magnitude of 7.7 t SOM ha^?1, or roughly 8.4% of the initial SOM mass. Reducing tillage intensity had no impact on SOM masses, but only on organic matter stratification in soils. We conclude that specialization of organic farms towards stockless arable crop production requires special attention on SOM reproduction to avoid detrimental effects. Further, reduced tillage intensity does not necessarily have a positive effect on SOM.     

Relation between soil organic matter and yield levels of nonlegume crops in organic and conventional farming systems

The aim of this study was to evaluate the interaction between yield levels of nonleguminous crops and soil organic matter (SOM) under the specific conditions of organic and conventional farming, respectively, and to identify implications for SOM management in arable farming considering the farming system (organic vs. conventional). For that purpose, correlations between yield levels of nonlegume crops and actual SOM level (C_org, N_t, C_hwe, N_hwe) as well as SOM‐level development were examined including primary data from selected treatments of seven long‐term field experiments in Germany and Switzerland. Yield levels of nonlegume crops were positively correlated with SOM levels, but the correlation was significant only under conditions of organic farming, and not with conventional farming treatments. While absolute SOM levels had a positive impact on yield levels of nonlegumes, the yield levels of nonlegumes and SOM‐level development over time correlated negatively. Due to an increased demand of N from SOM mineralization, higher yield levels of nonlegumes obviously indicate an increased demand for OM supply to maintain SOM levels. Since this observation is highly significant for farming without mineral‐N fertilization but not for farming with such fertilization, we conclude that the demand of SOM‐level maintenance or enhancement and thus adequate SOM management is highly relevant for crop production in organic farming both from an agronomical and ecological point of view. Under conventional management, the agronomic relevance of SOM with regard to nutrient supply is much lower than under organic management. However, it has to be considered that we excluded other possible benefits of SOM in our survey that may be highly relevant for conventional farming as well.     

The effect of farming system on labile fractions of organic matter in Calcari‐Epileptic Regosols

Total soil organic carbon (TOC) and nitrogen (N_t) and labile soil N and C fractions were investigated in a field experiment in the Swabian Mountains, Germany. The plots used had been farmed conventionally or organically since 1972 and treated with either mineral or organic fertiliser. There were no significant differences between organic and conventional plots in terms of TOC, N_t, C and N mineralisation potentials (C_pot, N_pot) and microbial C/N ratio. Microbial biomass C and N, however, were significantly higher on organic plots in spring. There was only a weak correlation between N_pot and microbial N. It is proposed that limitations in microbial N availability, as reflected in the microbial N/C ratio, control net N mineralisation rates in the incubation experiments, as indicated by the highly significant correlations between both N_pot and N_pot/C_pot ratios and microbial N/C ratios. The conclusion reached is that, under these field conditions, the positive effect of organic farming on the microbial biomass N pool does not contribute to an (relative or absolute) increase in the N available to plants.     

Long-term changes in soil organic matter under conventional tillage and no-tillage systems in semiarid Morocco

Abstract. A no-tillage (NT) system was developed in semiarid Morocco to improve the soil fertility and stabilize yield through conservation of water. Results in two long-term trials (4 and 11 years) were able to show the effects of a no-tillage system in increasing total soil organic matter and total nitrogen. Over time, the quality of the NT soil surface was improved compared with that under conventional tillage (CT) with disc harrows. This effect was the result of an increase in soil organic carbon (SOC) and a slight decline in pH. However, over time, nitrogen decreased in both tillage practices, especially in the 0–25 mm layer (from 0.59 to 0.57 t ha⁻¹ and from 0.44 to 0.42 t ha⁻¹ under NT and CT, respectively). After 4 years of NT an extra 5.62 t ha⁻¹ of SOC was sequestered in the 0–25 mm layer, and after 11 years the SOC increased further to 7.21 t ha⁻¹.     

Characteristics of phosphorus accumulation in soils under organic and conventional farming in plastic film houses in Korea

Organic farming (OF) is a fast growing alternative for sustainable agriculture in Korea. However, information on the effects of OF on the soil properties and environmental conservation is limited. In order to determine the effects of OF on the soil properties, 31 fields under OF (hereafter referred to as "OF fields") and 61 fields under conventional farming (CF) (hereafter referred to as "CF fields") in plastic film houses were selected throughout Korea and the soil chemical properties were investigated, including the P distribution characteristics. Average organic matter (OM) content was significantly higher (44 g kg^-1) in the OF fields then in the CF fields (24 g kg^-1). Bray-2 P values were 986 and 935 mg kg^-1 in the OF and CF soils, respectively, markedly exceeding the optimum range. Average total P (T-P) values were 2,973 mg kg^-1 in the OF fields and 1,830 mg kg^-1 in the CF fields. The high T-P values were due to repeated application of manure compost with a low N/P ratio. Inorganic P was the dominant fraction with 62–65% of T-P. The amounts of residual and organic P were significantly lower. The level of OF organic P was significantly higher (453 mg kg^-1) compared to the 106 mg kg^-1 value for the CF fields. Fractionation of soil inorganic P showed that Ca-P predominated with 1,332 mg kg^-1 in the OF fields, which was associated with soil pH values over 6.0. The main inorganic P fraction in the CF soils whose pH values were generally less than 6.0 consisted of Al-/Fe-P. The levels of water-soluble P was significantly higher (65 mg kg^-1) in the OF fields than in the CF fields (24 mg kg^-1). These results indicated that the OF system may lead to a serious degradation of the soil environment due to the accumulation of phosphorus and may be an important source of water pollution compared to the CF systems in Korea.     

连续施用不同比例鸡粪氮对水稻土有机质积累及土壤酸化的影响

【目的】土壤酸化是自然过程。随着农业集约化发展,土壤酸化在部分农田呈加速趋势,而施肥是目前农田土壤酸化加速的重要诱因,研究有机肥和化肥对土壤酸化的作用差异及机理,对合理指导施肥及耕地保育有重要的意义。【方法】通过测定不同施肥处理的不同组分有机质含量及酸碱缓冲容量,探明不同施肥处理的酸化影响,从土壤有机质和盐基累积角度对有机-无机肥料不同比例配施条件下土壤酸化特征进行了研究。【结果】① 连续5年在等氮量（N 270 kg/hm2）且有机－无机肥料不同配施比例的处理中,水稻产量以有机肥比例为25%~50%的处理最高,其平均产量比单施化肥处理提高了5.1%,比对照提高44.9%。但处理间无显著性差异;② 土壤各活性有机质及总有机质等指标中仅总有机质含量随鸡粪施用比例的增加而持续增加,不同比例有机无机肥配合施用后,土壤的高活性有机质及低活性有机质均高于CK和纯化肥氮处理,但随着有机肥投入比例的升高,除中活性有机质和水稻产量之间呈显著的正相关外（P=0.0067**）,高活性有机质、活性有机质及总有机质含量与水稻产量之间的相关性不显著（对应的概率值分别为P=0.192,P=0.208,P=0.160）;③ 施肥提高了土壤的碳库管理指数（CPMI）,且其随有机肥施用比例的上升呈增加趋势。增施鸡粪提高土壤的交换性盐基离子（Ca2+、 Mg2+、 K+、 Na+）含量,导致阳离子代换量（CEC）和pH随鸡粪施用比例的提高而升高。供试土壤酸碱缓冲容量为2.07~2.36 cmol/kg,随鸡粪施用比例的上升而增加,其与土壤阳离子代换量及有机质含量呈显著正相关。表明增施鸡粪可使土壤pH及酸碱缓冲容量上升,与鸡粪使土壤盐基累积量及有机质含量的提高有关。【结论】连续有机-无机肥施用下,土壤pH上升和酸碱缓冲容量的提高可能与该试验点下盐基离子和有机质含量随鸡粪施用比例上升有关,但其最终上升幅度及平衡点尚需进一步研究。鸡粪氮替代化肥氮比例为25%~50%时,土壤性质最优,水稻产量最高。     

Long-term effects of mineral and organic fertilization on soil organic matter fractions and sorghum yield under Sudano-Sahelian conditions

Abstract. Knowledge of changes in soil organic matter (SOM) fractions resulting from agricultural practice is important for decision‐making at farm level because of the contrasting effects of different SOM fractions on soils. A long‐term trial sited under Sudano‐Sahelian conditions was used to assess the effect of organic and inorganic fertilization on SOM fractions and sorghum performance. Sorghum straw and kraal manure were applied annually at 10 t ha^?1, with and without urea at 60 kg N ha^?1. The other treatments included fallowing, a control (no fertilization), and inorganic fertilization only (urea, 60 kg N ha^?1). Fallowing gave significantly larger soil organic carbon and nitrogen (N) levels than any other treatment. Total soil SOM and N concentrations increased in the following order: urea only < straw < control < straw+urea < manure with or without urea < fallow. Farming had an adverse effect on SOM and N status; however, this mostly affected the fraction of SOM >0.053 mm (particulate organic matter, POM). The POM concentrations in the control, straw and urea‐only treatments were about one‐half of the POM concentrations in the fallow treatment. POM concentrations increased in the following order: urea only < control < straw with or without urea < manure with or without urea < fallow. The fraction of SOM <0.053 mm (fine organic matter, FOM) was greater than POM in all plots except in fallow and manure+urea plots. Total N concentration followed the same trend as SOM, but cultivation led to a decline in both POM‐N and FOM‐N. Crop yield was greatest in the manure plots and lowest in the straw, control and urea‐only plots. Results indicate that under Sudano‐Sahelian conditions, SOM, POM and FOM fractions and crop performance were better maintained using organic materials with a low C/N ratio (manure) than with organic material with a high C/N ratio (straw). Urea improved the effect of straw on crop yield and SOM concentration.     

Soil organic matter dynamics under grain farming in Northern Kazakhstan

Because of their ability to store a high amount of soil organic matter (SOM), Chernozem soils are one of the most important resources from both agricultural and environmental viewpoints. This study was carried out to determine the SOM budget under grain farming in the Chernozem soil of northern Kazakhstan through the analysis of in situ soil respiration and soil environmental factors such as soil temperature as well as moisture content. Five experimental plots including one fallow field were established at the experimental farm of Barayev Kazakh Research and Production Center of Grain Farming, Shortandy, northern Kazakhstan (mean annual precipitation and average year temperature are 323 mm and 1.6°C, respectively). Mean daily soil temperature increased to above O°C in early April, remaining at above 20°C from mid-June to mid-August, and then sharply decreased to below 5°C at the end of September. Most of the biological activities were considered to be limited from April to September. On the other hand, the soil moisture content remained high after thawing until mid-June and then continuously decreased in the cropped plots except during the rainfall events. The soil respiration rate recorded the highest values from late June to early July and overall fluctuations were similar to those of the soil temperature, unlike the fluctuations of soil microbial C and N contents, which exhibited similar patterns to those of the soil moisture content. In order to represent the daily soil respiration rates using the soil environmental factors, the following relationship was introduced as a model function: Cem = aM ^pbexp(-E/RT). The coefficients, a, b, and E (activation energy in Arrhenius equation), were determined by stepwise multiple regression after logarithm transformation using the measured data, Cem (daily soil respiration rate), M (volumetric soil moisture content), and T (absolute soil temperature). As a result, a significant relationship was always obtained between the soil respiration rate and the activation energy, E, while the contribution of the soil moisture content to the soil respiration rate was uncertain. Using the regression equations and monitored data of soil temperature and moisture content, cumulative soil respiration throughout the cropping period was calculated to be in the range of 2.5 to 3.2 Mg C ha^p-1 On the other hand, the amounts of crop residues in the cropped plots that were expected to be incorporated into the soils ranged from 1.6 to 4.4 Mg C ha^p-1 Except for the plot planted with oats (higher amounts of residues than for wheat), the SOIL budget was slightly negative in this year, that is, the soils lost their organic matter stock. Although it is difficult to generalize the C budget in different years because of the large variations in crop growth due to fluctuating water resources, the disadvantage of summer fallow (no residues) was obvious in terms of SOM budget. The net soil respiration rate in the fallow plot, 2.9 Mg C ha^p-1 was approximately equivalent to 4% of the total SOM stock in the plow layer (30 cm) (70 to 80 Mg C ha^p-1 To reduce further loss of SOM, at least evenly extensive use of summer fallow should be reconsidered.     

Nitrogen transformations in tropical soils under conventional and sustainable farming systems

Samples of alluvial soil from mixed sandstone shale and slate and of Taiwan clay were collected from two sites, both managed under a similar crop rotation scheme. The fields were further divided into sections which were managed under either conventional farming or sustainable farming practices. When the soil samples were collected in April 1989, after 1 year of operation under conventional or sustainable practices, the nitrification activities of both soils managed under sustainable practices practices. The nitrifying activities in Taiwan clay samples collected in April 1993 which had been managed with chemical or with organic fertilizer were not significantly different. However, nitrifying activity in the alluvial soil was higher under sustainable than under conventional practices. Numbers of NH ₄ ⁺ -oxidizing bacteria were not significantly different in any of the soil samples irrespective of the different management practices. In contrast, higher numbers of NO ₂ ^- -oxidizing bacteria were detected in both soils managed sustainably. The results also indicated that the composition of NH ₄ ⁺ -oxidizing bacteria differed in the alluvial soil when managed with different kinds of fertilizer.     

用土壤全氮与有机质建立油菜测土施氮指标体系的研究

本文在汇总近年来浙江省多点油菜氮肥效应试验、氮肥用量试验的基础上,比较氮肥效应、经济施氮量与土壤全氮、土壤有机质之间的回归函数模型,筛选建立油菜测土施氮指标体系的可靠测定指标。回归分析结果表明,土壤有机质、土壤全氮与缺氮处理相对产量回归指数函数分别为Y=20.157e0.4413X（R2=0.5887**）和Y=10.882e0.045X（R2=0.3365**）,土壤有机质、土壤全氮与油菜经济施氮量对数函数分别为Y=-314.25LnX +1392.9（R2=0.6896**）和Y=-191.77LnX+427.81（R2=0.314**）。比较曲线函数的回归决定系数R2,土壤有机质与缺氮处理相对产量、经济施氮量的回归决定系数大于预测精度要求,可成为油菜种植田土壤供氮能力丰缺和推荐经济施氮量的指标,而全氮由于回归决定系数R2低于0.35,不适合成为土壤供氮能力和推荐经济施氮量的指标。通过回归方程划定不同土壤供氮水平下土壤有机质含量范围和相对应的推荐经济施氮量,构建浙江省油菜测土施氮指标体系。     

Effects of hydrophobic and hydrophilic organic matter on the water repellency of model sandy soils

Soil water repellency affects the hydrological functions of soil systems. Water repellency is associated with the content and the composition of soil organic matter. In the present study, we examined the effects of hydrophobic and hydrophilic organic matter contents, the hydrophobic/hydrophilic organic matter ratio and the total organic matter content on water repellency using model sandy soils. Stearic acid and guar gum were used as the hydrophobic and hydrophilic organic compounds, respectively. Water repellency was estimated using the sessile drop method. Hydrophobic organic matter content was found to be the dominant factor affecting soil water repellency. Hydrophilic organic matter was found to increase the contact angle to some extent without the presence of hydrophobic organic matter. With the presence of both hydrophobic and hydrophilic organic matter, the effects of the hydrophilic organic matter content on contact angle were found to be dependent on the hydrophobic organic matter content of the soil. This relationship was explained by the differences in the surface free energies of different organic matter and mineral surfaces. The contact angle increased with increasing hydrophobic/hydrophilic organic matter ratio when the hydrophilic organic matter content was constant. When the hydrophobic organic matter content was constant, contact angles were roughly comparable, irrespective of the hydrophobic/hydrophilic organic matter ratio. The contact angles were not comparable at each total organic matter content. Accordingly, the hydrophobic/hydrophilic organic matter ratio and the total organic matter content in soil may not provide satisfactory information about soil water repellency.     

Detectability of degradable organic matter in agricultural soils by thermogravimetry

Sustainable agricultural land use requires an assessment of degradable soil organic matter (SOM) because of its key function for soil fertility and plant nutrition. Such an assessment for practical land use should consider transformation processes of SOM and its sources of different origin. In this study, we combined a 120‐day incubation experiment with thermal decay dynamics of agricultural soils altered by added organic amendments. The aim was to determine the abilities and limits of thermal analysis as a rapid approach revealing differences in the degradability of SOM. The carried out experiments based on two independent sampling sets. The first sample set consisted of soil samples taken from non‐fertilized plots of three German long‐term agricultural field experiments (LTAEs), then artificially mixed with straw, farmyard manure, sheep faeces, and charcoal equal to 60 Mg ha^?1 under laboratory conditions. The second sample set based on soil samples of different treatments (e.g., crop type, fertilization, cultivation) in LTAEs at Bad Lauchstädt and Müncheberg, Germany. Before and after the incubation experiment, thermal mass losses (TML) at selected temperatures were determined by thermogravimetry indicating the degradability of organic amendments mixed in soils. The results confirmed different microbial degradability of organic amendments and SOM under laboratory conditions. Thermal decay dynamics revealed incubation‐induced changes in the artificial soil mixtures primarily at TML around 300°C in the case of applied straw and sheep faeces, whereas farmyard manure showed mainly changes in TML around 450°C. Charcoal did not show significant degradation during incubation, which was confirmed by TML. Detailed analyses of the artificial soil mixtures revealed close correlations between CO₂‐C evolution during incubation and changes in TML at 300°C with R² > 0.96. Results of the soils from LTAEs showed similar incubation‐induced changes in thermal decay dynamics for fresh plant residues and farmyard manure. We conclude that the practical assessment of SOM could be facilitated by thermal decay dynamics if modified sample preparation and evaluation algorithms are used beyond traditional peak analysis.     

Extraction of water‐soluble organic matter from mineral horizons of forest soils

Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H₂O, 0.01 M CaCl₂, and 0.5 M K₂SO₄. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K₂SO₄ extracted the largest amounts of WSOC (up to 126 mg C kg^–1) followed by H₂O followed by CaCl₂. The H₂O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol^–1 cm^–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K₂SO₄ bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous.     

Soil organic matter and sorption capacity under different soil management practices in a productive vineyard

The effect of soil organic matter (SOM) on sorptive parameters under different soil management practices in Rendzic Leptosol was studied. In 2006, an experiment of different management practices in a productive vineyard was established in the locality of Nitra-Dra?ovce (Slovakia). The following treatments were established: (1) control (grass without fertilization), (2) T (tillage), (3) T + FYM (tillage + farmyard manure), (4) G + NPK3 (grass + 3rd intensity of fertilization for vineyards), (5) G + NPK1 (grass + 1st intensity of fertilization for vineyards). Soil samples were collected every month during the year 2010. Obtained results showed increased hydrolytic acidity (by 23%), sum of basic cations (by 37%) and decreased total cation exchange capacity (CEC) (by 36%) with higher doses of fertilization in comparison to control. Application of farmyard manure had a positive effect on the increase in the SOM cation sorption capacity. Positive correlations between pH and sum of basic cations (SBC) (r = 0.493, p ≤ 0.001), CEC (r = 0.498, p ≤ 0.001) and cation sorption capacity of SOM (r = 0.391, p ≤ 0.01) were observed. Higher values of labile carbon:potentially mineralizable nitrogen (C_L:N_pot) ratio corresponded with lesser CEC, SBC and base saturation values in the soil. With increased humus quality (higher values of humic acid:fulvic acid (C_HA:C_FA) ratio), cation sorption capacity of SOM significantly increased (r = 0.329, p ≤ 0.01). The results of this study proved that the application of farmyard manure had a positive effect on the increase of SOM sorption capacity, but higher doses of mineral fertilizers added to soil had a negative effect.     

Chemistry of soil organic matter as related to C : N in Norway spruce forest (Picea abies(L.) Karst.) floors and mineral soils

Due to high nitrogen deposition in central Europe, the C : N ratio of litter and the forest floor has narrowed in the past. This may cause changes in the chemical composition of the soil organic matter. Here we investigate the composition of organic matter in Oh and A horizons of 15 Norway spruce soils with a wide range of C : N ratios. Samples are analyzed with solid‐state ¹³C nuclear magnetic resonance (NMR) spectroscopy, along with chemolytic analyses of lignin, polysaccharides, and amino acid‐N. The data are investigated for functional relationships between C, N contents and C : N ratios by structural analysis. With increasing N content, the concentration of lignin decreases in the Oh horizons, but increases in the A horizons. A negative effect of N on lignin degradation is observed in the mineral soil, but not in the humus layer. In the A horizons non‐phenolic aromatic C compounds accumulate, especially at low N values. At high N levels, N is preferentially incorporated into the amino acid fraction and only to a smaller extent into the non‐hydrolyzable N fraction. High total N concentrations are associated with a higher relative contribution of organic matter of microbial origin.     

Evaluation of soil health in organic vs. conventional farming of basmati rice in North India

Conventional agricultural practices that use excessive chemical fertilizers and pesticides come at a great price with respect to soil health, a key component to achieve agricultural sustainability. Organic farming could serve as an alternative agricultural system and solve the problems associated with the usage of agro‐chemicals by sustainable use of soil resources. A study was carried out to evaluate the impact of organic vs . conventional cultivations of basmati rice on soil health during Kharif (rainy) season of 2011 at Kaithal district of Haryana, India, under farmers' participatory mode. Long‐term application of organic residues in certified organic farms was found to improve physical, chemical, and biological indicators of soil health. Greater organic matter buildup as indicated by higher soil organic carbon content in organic fields was critical to increase soil aggregate stability by increasing water holding capacity and reducing bulk density. Proper supplementation of nutrients (both major and micro nutrients) through organic residue addition favored biologically available nutrients in organic systems. Further, the prevalence of organic substrates stimulated soil microorganisms to produce enzymes responsible for the conversion of unavailable nutrients to plant available forms. Most importantly, a closer look at the relationship between physicochemical and biological indicators of soil health evidenced the significance of organic matter to enzyme activities suggesting enhanced nutrient cycling in systems receiving organic amendments. Enzyme activities were very sensitive to short‐term (one growing season) effects of organic vs . conventional nutrient management. Soil chemical indicators (organic matter and nutrient contents) were also changed in the short‐term, but the response was secondary to the biochemical indicators. Taken together, this study indicates that organic farming practices foster biotic and abiotic interactions in the soil which may facilitate in moving towards a sustainable food future.     

Organic matter effects on phosphorus sorption in sandy soils

Phosphorus (P) sorption processes in soils contribute to important problems in agriculture: a deficiency of this plant nutrient and eutrophication in aquatic systems. Soil organic matter (SOM) plays a major role in sorption processes, but its influence on P sorption remains unclear and needs to be elucidated to improve the ability to effectively manage soil P. The aim of this research was to investigate the influence of SOM on P sorption. The study was conducted in sandy soil profiles and in topsoils before and after removal of SOM with H₂O₂. The results were interpreted with the Langmuir and Freundlich isotherms. Our results indicated that SOM affected P sorption in sandy soils, but that P sorption also depended on specific soil properties (e.g. values of the degree of P saturation (DPS), P sorption capacity (PSC) and pH) often related to land use. Removal of SOM decreased PSC in most of the topsoils tested; other soil properties became important in controlling P sorption. An increase in P desorption observed after SOM removal indicated that SOM was potentially that soil constituent which increased P binding and limited P leaching from these sandy soils.