Addition Of Organic Matter Research Articles

Absorption and Translocation Capacity of Cadmium in Papaya (Carica papaya L.) Plants With Addition of Organic Matter

Cadmium (Cd) is a toxic element that can be easily absorbed by crops, and can enter through the frequent use of fertilizers in crop areas. The objective of this study was to evaluate the bioaccumulation percentage (BAP) and translocation factor (TF) of Cd in papaya plants exposed to contaminated soils at 50, 100 and 150 mg L-1 and at two concentrations of organic matter: 2% and 10%-MO. Growth variables, chlorophyll and metal concentration were measured after 10 months of cultivation. The results indicated that the greatest growth occurred in soil at 10%-OM in relation to those grown at 2%-OM. Cd bioaccumulation was leaves < stem < root (9 < 22 < 68%) at 50 mg L-1, (7 < 29 < 65%) at 100 mg L-1 and (4 < 34 < 63%) at 150 mg L-1, observing the greatest accumulation in the root. The findings showed that organic matter in soil decreases the availability of metal uptake in the roots. The translocation results were < 1, indicating that the root has the ability to restrict metal transport to the aerial part in plants grown in 10%-OM soil, however, in 2%-OM soil it tends to increase this metal accumulation, suggesting that the application of organic amendments is an alternative to reduce the risk of Cd absorption in agricultural soils.

Analisa Faktor Pembatas Pertumbuhan Tebu (Saccharum officinarum L.) di Cangkringan, Yogyakarta

This study aims to determine the plant growth parameters that most influence sugarcane productivity. The research was carried out from April 2021 to September 2021 in Argomulyo Village, Cangkringan District, Sleman Regency, Yogyakarta. This research was conducted using a survey method by taking samples of sugarcane stalks at each sampling point. The land area is 3 ha which is divided into 3 blocks, then from each block 10 sugarcane samples are taken so that there are 30 sugarcane samples. Parameters observed in this study were plant height, number of stems, stem diameter, number of leaves, number of internodes, and weight of sugarcane stalks. The results showed that the parameters that had a very high effect on productivity were stem diameter (r=0.986), number of tillers per clump (r=0.908) and sugarcane plant height (r=0.904). Meanwhile, the correlation with sugarcane stalk weight was high (r=0.879), with the number of leaves and cane stem segments very low (r=0.160 and r=0.172). Land productivity in the research location was also much lower than its potential. The addition of organic matter to improve the physical properties of the soil and increase the availability of nutrients was needed so as to increase the growth and productivity of sugarcane.

Effects of organic amendments and cover crops on soil characteristics and potato yields

ABSTRACT Intensive potato production may reduce the soil organic matter content (SOM), which may impact several soil functions and increase the incidence of potato diseases. We examined if cover crop and addition of organic materials may counteract these effects. Organic materials were one application of biochar mixed with liquid digestate (BLD); solid digestate (SD); or farmyard manure (FYM); with or without winter rye as cover crop, in a field with regular potato growing. Organic amendment increased SOM, especially for FYM and BLD, while cover crop did not affect SOM. Yet, cover crop increased tuber yields in the second year, and reduced the severity of potato diseases by 10% in post-harvest potatoes in both years. In the second year, the number of marketable potatoes after storage increased by 37% with cover crop. Organic amendments did not affect potato yield or quality, but the proportion of marketable potatoes tended to be higher in the amended soil. By lab incubation, BLD showed the largest potential for SOM storage, up to 32 years, followed by FYM and SD. Cover crops and organic amendments is recommended in potato production, especially for early potatoes where there is sufficient time after harvest to establish a good cover crop.

Nitrogen dynamics in soils fertilized with digestate and mineral fertilizers: A full field approach

Highly stabilized digestate from sewage sludge and digestate-derived ammonium sulphate (RFs), were used in a comparison with synthetic mineral fertilizers (SF) to crop maize in a three-year plot trial in open fields. RFs and SF were dosed to ensure the same amount of mineral N (ammonia-N). In doing so, plots fertilized with digestate received much more N (+185 kg ha−1 of organic N) because digestate also contained organic N. The fate of nitrogen was studied by measuring mineral and organic N in soil at different depths, ammonia and N2O emissions, and N uptake in crops. Soil analyses indicated that at one-meter depth there was no significant difference in nitrate content between RF, SF and Unfertilized plots during crop season indicating that more N dosed with digestate did not lead to extra nitrate leaching. Ammonia emissions and N content in plants and grains measured were also similar for both RF and SF. Measuring denitrification activity by using gene makers resulted in a higher denitrification activity for RF than SF. Nevertheless, N2O measurements showed that SF emitted more N2O than RF (although it was not statistically different) (7.59 ± 3.2 kgN ha−1 for RF and 10.3 ± 6.8 kgN ha−1 for SF), suggesting that probably the addition of organic matter with digestate to RF, increased the denitrification efficiency so that N2 production was favoured. Soil analyses, although were not able detecting N differences between SF and Rf after three years of cropping, revealed a statistical increasing of total carbon, suggesting that dosing digestate lead to carbon (and maybe N) accumulation in soil. Data seem to suggest that N2O/N2 emission and organic N accumulation in soil can explain the fate of the extra N dosed (organic-N) in RF plots.

Long-Term Organic Amendments Combined with Nitrogen Fertilization Regulates Soil Organic Carbon Sequestration in Calcareous Soil

Organic amendments have been widely confirmed to support soil health and agricultural sustainability. However, the effects and mechanisms of long-term organic amendments combined with chemical fertilizers on soil organic carbon (SOC) sequestration and soil macroaggregate formation are still unclear. Therefore, this study aimed to explore the interaction between soil carbon sequestration and soil agglomeration after 12 years of fertilization. Seven treatments within a field experiment were selected to conduct the research, including nitrogen (N) application by farmers, optimized N management, biochar and/or straw, manure, compost or biogas residue plus optimized N management. The results showed that the addition of organic materials significantly enhanced the SOC by 29.6–119.8% and 10.3–36.3% in 0–15 and 15–30 cm soil layers compared to N application by farmers, respectively. Meanwhile, the soil humus carbon pools in the 0–15 cm soil layer were increased by 14.7–205.2%, particularly humin carbon (HUC), which could be considered as a useful indicator of the soil carbon sequestration process. Among the organic materials, the addition of biochar was the most effective strategy due to its high aromatic carbon content that resisted biodegradation. The addition of organic materials also improved the soil labile carbon fractions, and the contents of microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC) and KMnO4-oxidizable carbon (ROC) were enhanced by 120.5%, 92.3%, 217.2% and 85.5% on average, respectively, and the amount of exchangeable Ca2+ and Mg2+ cations and Fe and Al oxides in the soil increased significantly whilst the Na+ content declined in the 0–15 cm soil layer. These indicators showed a significant correlation with the mean weight diameter (MWD). Our results revealed that the addition of organic materials could be an effective management practice to promote soil carbon sequestration and soil macroaggregate formation in calcareous soil.

INDICATOR ATTRIBUTES OF SOIL QUALITY IN AREAS UNDER DIFFERENT LAND USE SYSTEMS, IN THE WESTERN AMAZON

The anthropization of natural environments, when performed inadequately, promotes the disruption of the ecological balance and can influence the fauna, flora and biodiversity in general, including the edaphic environment and its components. The objective was to evaluate the soil attributes in areas with different types of vegetation cover and different forms of soil management. The study was carried out in native forest area (Subperennial Equatorial Forest) and cultivated area (annual species), in Porto Velho, Rondônia, Brazil. Samples were collected in two layers (0-10 and 10-20cm), on a Latossolo Vermelho-Amarelo, to evaluate microbial biomass by the fumigation-extraction (FE) method, as well as the chemical and physical soil attributes. It was possible to verify a significant increase in soil density and reduction of moisture and improvement of chemical attributes resulting from the use of the area. The organic matter content decreased sharply in the managed area (25%), compared to the forest, in the superficial layer (0-10cm). Microbial C-biomass under the native forest showed 54% higher mean value (883 mgC g-1) compared to the managed area (410 mgC g-1) in the superficial layer. The microbial N-biomass ranged from 21.3 to 19.5 mgN.g-1 in the native forest area, and from 9.3 to 11.5 mgN g-1 in the managed area, respectively in the 0-10 and 10-20cm layers. In the native forest area, the addition of organic matter to the soil by the vegetation litter was an important conditioning factor for the microbial community, demonstrating the use of this attribute as an indicator of soil quality.

Holm oak (Quercus ilex L.) cover: A key soil-forming force in controlling C and nutrient stocks in long-time coppice-managed forests

In forest ecosystems, soil-plant interactions drive the physical, chemical, and biological soil properties and, through soil organic matter cycling, control the dynamics of nutrient cycles. Parent material also plays a fundamental role in determining soil's chemical properties and nutrient availability. In this study, eight long-time coppice-managed Holm oak forests under conversion to high forest, located under similar climatic conditions in Tuscany and Sardinia Regions (Italy), and grown on soils developed from three different lithologies (limestone, biotite granite, and granite with quartz veins) were evaluated. The research aimed to a) estimate the amount of C and nutrients (total N and potentially available P, Ca, Mg, and K) stored both in the organic, organo-mineral, and mineral horizons and at fixed depth intervals (0–0.3 and 0.3–0.5 m), and b) assess the dominant pedological variables driving elemental accumulation. The soils were described and sampled by genetic horizons and each sample was analyzed for its C and nutrient concentration in both the fine earth and skeleton fractions. Despite the different parent materials from which the soils had evolved, the physicochemical properties and the C and nutrient stocks for the 0–0.3 and 0.3–0.5 m layers did not show substantial differences among the eight soils. Conversely, some differences were observed in the stocks of potentially available P and Ca per 0.01 m of mineral horizons. The findings show that over time, plant-induced pedogenic processes (acidification, mineral weathering, organic matter addition, and nutrient cycling) almost obliterated the influence of parent materials on soil properties. This resulted in the upper soil horizons that showed similar characteristics, even though derived from different lithologies. However, among the study sites, some differences occurred due to lithology, as in the case of the soils derived from calcareous parent materials that had high concentrations of exchangeable Ca in the mineral horizons and, likely, to environmental variables (e.g., exposure), which possibly influenced litter degradation and the release of nutrients such as N and available P.

Mapping Soil Parameters with Environmental Covariates and Land Cover Projection in Tropical Rainforest, Hangadi Watershed, Ethiopia

Machine learning and geostatistics are efficient techniques for investigating the geographic distribution of soil properties. This study’s objectives were to assess soil fertility status, map the spatial variability of selected soil parameters and compare random forest with ordinary kriging. Soil samples were collected to analyze parameters: pH, cation exchange capacity (CEC) and organic carbon (OC) using systematic sampling. Some environmental covariates were used in the machine learning process: a digital elevation model (DEM) collected from USGS distributing shuttle radar topography mission data and a LULC map generated from a 30-year time series (1988–2018) of Landsat 8. Georeferenced samples were sent to Batu Soil Research Laboratory. pH, CEC and OC were mapped and status was determined using random forest and ordinary kriging. Random forest was more accurate with low mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE) and coefficient of determination (high R2). In random forest, pH varied between 5.03 and 5.76 and ordinary kriging pH ranged from 4.96 to 5.76. pH was greater in cultivated land. CEC and OC were higher in the forest. The higher pH in cultivated land was due to grass coverage and minimal tillage. The addition of organic matter and CEC to a forest may result in higher OC. Environmental covariates (topographic, bands, NDVI and LULC) were used to predict the gradients of pH, OC and CEC. For pH, OC and CEC, DEM was the most important predictor. CEC was high in low landscape, but low in high landscape positions. Low OC requires composting, fallow and organic fertilizers. Future research should include the remaining predictors: physiochemical and lithological data to improve the performance of random forest.

Capturing the rapid response of sediments to low-oxygen conditions with high temporal resolution gas concentration measurements

Low-oxygen conditions plague coastlines worldwide. At present, little is known about how the transition from normoxic to low or even no oxygen conditions alters sediment biogeochemical cycling and ultimately ecosystem functioning. Conventional sediment core incubations cannot capture rapid (<hourly) changes in biogenic gas fluxes that may occur due to oxygen depletion. To better constrain the response of sediments to hypoxia, we employed a novel flow-injection system coupled to a membrane inlet mass spectrometer to quantify fluxes oxygen, dinitrogen, and methane across the sediment-water interface from a temperate estuary (Narragansett Bay, Rhode Island, United States). We evaluated how sediments from a site more impacted by nitrogen pollution compare to one less impacted by nitrogen in response to organic matter addition. Our system is able to sample every 10 minutes, allowing us to cycle through triplicate core measurements roughly every 30 minutes to track the response of sediments to increasing hypoxic severity. The high temporal-resolution data revealed dynamic changes in sediment-water gas fluxes, suggesting that reactive nitrogen removal is enhanced under mild hypoxia but dampened under prolonged hypoxia to anoxia. Further we found that organic matter loading enhances both net denitrification and methane emissions. Ultimately, our approach represents a powerful new tool for advancing our knowledge of short-term temporal dynamics in benthic biogeochemical cycling.

Physico-chemical Properties in Rhizosphere of Some Field Crops at Different Growth Stages in a Sandy Clay Loam Soil in Sourthern Nigeria

The effects of different cultivated crops and their growth periods on some hydraulic and chemical properties of a sandy clay loam soil at the University of Port Harcourt, Teaching and Research Farm, in Choba, Rivers State, Nigeria was studied. The objective was to understand the changes in soil physical and chemical properties near the plant environment during the growing period for optimum management. Four (4) crops: Maize (Zea mays L.), Okra (Abelmoschus esculentus), Pepper (Capsicum annuum), and Garden egg (Solanum melongena F.) were planted to native fallowed soil and the soil properties measured at three (3) growth stages of the crops viz: Establishment, Flowering, and Maturity. Results revealed that the plants did not modify the soil textural class. Significant changes in bulk densities and saturated hydraulic conductivity were found during the flowering stage of the crops. Bulk density of 1.36 and 1.34 g cm-3 were significantly (p<0.05) low at during flowering and maturity stages, respectively, in Garden egg soils. The highest saturated hydraulic conductivity (Ksat) values of 22.9 and 27 cm h-1, respectively, were significant (p<0.05) during the same periods for garden egg, followed by Maize and Okra. Results also revealed that Okra, Pepper and Garden egg significantly (p<0.05) reduced the soil acidity at flowering growth period. Maize contributed significant additions of soil organic matter to the soil at flowering and maturity periods. Maximum removal of available plant nutrients was at flowering stage for maize when more than 80% of the plant had shown tasselling and cob formation. Therefore, monitoring the growth stages of specific plant could help in nutrient and soil management and changes in soil physical and chemical properties.

Spatial variability of soil organic carbon fractions in areas under cultivation of Amazonian species in the southern region of Amazonas state, Brazil

Soil organic carbon (OC) is heterogeneous and sensitive to agricultural management, so knowledge of its spatial variability can improve the monitoring of areas under anthropogenic influence, as OC can serve as a sensitive indicator of changes in the environment. The objective of this study was to evaluate the spatial variability of soil OC fractions in areas of cultivation with Amazonian species in the southern region of Amazonas state. A total of 256 georeferenced data points were collected in the 0.0–0.05 m and 0.05–0.10 m layers in the following agricultural systems: areas with cultivation of Guaraná, Annatto, Cupuaçu and forest. The OC contents were analyzed, and the chemical fractionation of soil organic matter was performed. The analytical results were evaluated through descriptive statistical analysis, and the spatial pattern was evaluated through geostatistical analysis. The conversion of natural ecosystems to agricultural systems affected the rates of addition and decomposition of soil organic matter. Changes in soil organic carbon stocks (SOC stock) due to the uses of different agricultural systems were determined by evaluating the free light fraction of soil organic matter. For the chemical fractions of organic matter, there was a predominance of the humin fraction (C-HU) in relation to the fractions of humic acid (C-FAH), fulvic acid (C-FAF) and OC associated with minerals (COAM) in the different land uses and soil layers analyzed. The geostatistical procedures proved to be important in determining the degree of carbon dependence and its fractionation in the context of spatial variability, and this information is useful in soil quality monitoring.

Wastewater Use: A Debatable Scenario and their Impacts on Crop Production

About 90% of freshwater is used in agriculture for crop production and the world is already facing a scarcity of fresh water resources. Changing climate and rainfall pattern urge crops to demand more water while wastewater is excessively available and produce in huge amount which holds a maximum amount of organic matter and nutrients. Freshwater scarcity and demand for more food production urge farmers to use wastewater. Wastewater use has some pros and cons, in pros the addition of organic matter to soil bodies, while in cons are reduction in germination, growth, and yield. Wastewater helps farmers increment soil organic matter, total available macro and micronutrients. The negative effect is due to the addition of toxic material to soil bodies such as heavy metals, and it can't be reduced crop yield if it remains below the toxic limits. But the current scenario of wastewater uses and their positive and negative effects on the yield of crops are still under debate due many researchers showed that crop yield is reduced, and some mentioned that the crop yield increases or effects are insignificant. In this article, discussions are made about the impacts of wastewater irrigation and their correlation to seeds germination, plant growth and yield.

The influence of compost amendments on bioaccumulation of potentially toxic elements by pea plant cultivated in mine degraded soils

Potential toxic metal (PTE) accumulation in soil and water is one of the major sources of food crop contamination. PTE remediation from soil can be enhanced by the addition of organic matter to the growing media. An experiment was carried out to investigate the effect of different organic amendments on the accumulation of PTEs in pea plant grown on mine degraded soils. Mining soils from chromite mine (CM), soap stone mine (SSM), manganese mine (MM), and quartz mine (QM) were mixed with vermicompost (VC), leaf mould (LC), and spent mushroom compost (SMC) along with garden soil at 1:1:1 ratio. Various growth and yield-related attributes of pea plant as well as PTE concentrations in soil and plants were studied. The highest Cd (2.62 mg kg−1) and Cr (13.6 mg kg−1) concentration was reported in CM soil, while Pb (23.3 mg kg−1) and Mn (59.2 mg kg−1) concentration in SSM and MM soil, respectively. Mining soils significantly reduced the plant growth and yield, while organic amendments reduced the PTE availability and increased pea plant growth. Comparing the various organic fertilizers used, it was observed that VC efficiently reduced Cd, Cr, Pb, and Mn uptake by pea plant, subsequently, improved pea plant growth and productivity. In order to assess the effects of various amendments on PTE health risk reduction, various risk indices including plant tranfser factor, average daily intake, health risk, target hazard quotient, and target cancer risk were also calculated and the results revealed that application of compost particularly VC significantly reduced the dietary intake and health risks of PTEs.

Ketahanan Bibit Kayu Putih (Melaleuca cajuputi) pada Berbagai Media Tercemar Air Asam Tambang

Cajeput (Melaleuca cajuputi) is widely used as a post-mining revegetation plant. The addition of organic matter to post-mining land can improve the physical, chemical, and biological conditions of the soil that lead on to increasing growth and endurance of cajeput in polluted land by acid mine drainage. This study aims to analyze the effect of compost mixture media and roasted husk mixture media to endurance and growth of cajeput seedling and also to analyze the effect of acid mine drainage concentration on the endurances of cajeput seedling on various media. This study used a completely randomized design with two factors consisting of acid mine drainage concentration and type of media. The results of this study indicate that the concentration of acid mine drainage has no significant effect on the growth of height, diameter, and number of leaves, also on total wet weight, total dry weight, moisture content, and root length while the type of media used has a significant effect on growth in height, diameter, and the number of leaves.
 Keywords: acid mine drainage, compost, Melaleuca cajuputi, roasted husk

Ancient metalworking at Yodhawewa site, Sri Lanka: tracing the archaeological and geochemical relationship by analyzing soil and slags

The Yodhawewa archaeometallurgical site was the latest discovery in Sri Lanka in 2018. This study aimed to trace the archaeological and geochemical relationship by analyzing the soil and slags of the site dating back to the c. first to eighth centuries AD. The analysis was mainly based on the X-ray fluorescence (XRF) method. The soil chemistry resulted in some clues to special metal processing zones in the excavation-1 area. The cultural layers of that area (profiles 1 and 2) showed relatively high copper composition (max. 470 ppm), and crucible fragments containing copper particles were also detected in the same layers. The vertical distribution of soil elements and their correlations with TiO2 suggested that long-term metal activity may have affected changes in environmental soil chemistry. Relatively high phosphorus was indicated in the soil-related furnace wall, suggesting the artificial addition of organic matter to the clay body during the furnace wall construction to withstand the high temperatures. High iron slag (HIS) varies from 12.96 to 49.63 wt% of Fe2O3 and shows high MnO, P2O5, and V. Lightweight amorphous/glassy slags (LIS) associated with secondary refining have low iron content and a high CaO and Sr composition.

Evaluasi Status Hara dan Rekomendasi Pemupukan Padi Sawah Di Kecamatan Batin III Ulu Kabupaten Bungo Jambi

Evaluation of Nutrient Status and Recommendations for Fertilization of paddy rice. The assessment was carried out in Batin III Ulu District, Bungo Jambi Regency with a rice field area of 655 ha spread across 8 (eight) villages. This study aims to evaluate the nutrient status and determine fertilization recommendations in paddy rice. The study used a description method based on field observations and laboratory analysis. Examples of composite soils resulting from the field, analyzed the nutrient status of N, P, and K as well as soil pH with the Paddy Soil Test Kit. Based on the value of the N, P, K nutrient status test, it is determined to recommend fertilizer application. N fertilizer during the growth period is applied 3 (three) times, namely at planting time (before 14 DAP), without the use of LCC (leaf colour chart), the second fertilization on active tillering stadia (21-28 DAP), and the third on flower primordia stadia (50 days after planting). The results of the nutrient status analysis with STD, the P and K nutrient status of the soil are grouped into three classes, namely low, medium, and high. From the P and K status classes of the soil, recommendations for fertilization P (SP-36) and K (KCl) are made. The results showed that the obstacle to increasing the productivity of paddy rice in this area is that the content of N, P and K is generally low, and the soil pH ranges from 5-6. Therefore, to increase the productivity of paddy rice yields, it is recommended to apply inorganic fertilizers (N, P, and K) and the addition of organic matter. Based on the results of soil analysis and the nutrient status of paddy soils, site-specific N, P and K fertilization recommendations were obtained. Fertilizers used in the form of Urea, SP-36 and KCl, without the addition of organic matter and with the addition of organic matter.

Mycobiome of Post-Agricultural Soils 20 Years after Application of Organic Substrates and Planting of Pine Seedlings

A 20-year study of a pine stand on post-agricultural land showed that woody debris in the form of organic matter can be successfully used to restore symbiotic mycorrhizal communities, as is the case with forest soils. Woody substrates restored organic matter in soils altered by long agricultural use and had a positive effect on the composition of mycobiota antagonistic to pathogens, especially to Heterobasidion annosum, the causal agent of the dangerous disease root and stump rot of many forest tree species, including stands of Pinus sylvestris (L.). In a study that started in 2001 in the forest district of Czarne Człuchowskie (northern Poland), the following organic materials were used: wood residues (W), sawdust (S), bark compost (B), and compost applied to the root zone during planting (G). The organic materials were spread in the form of mulch over the entire area during planting. After twenty years, it was found that the substrates used provided suitable growth conditions for mycobiome useful for pines. The addition of organic matter did not change the alpha biodiversity of the soil, but in the long term led to significant changes in the composition of mycobiota (beta biodiversity). The changes in the soil after the addition of organic material naturally accelerated the formation of the forest habitat. A number of fungi evolved that degraded added lignin and cellulose while being antagonists of H. annosum and other pine pathogens. In particular, the well-known hyperpathogens of the genus Trichoderma played an important role by promoting resistance of the soil environment to pathogens. Soil enrichment by bark compost and wood residues increased the relative abundance of Trichoderma more than fourfold.Mycorrhizal fungi became dominant in soil enriched with organic matter. After enriching the soil with bark compost, the relative abundance of Amphinema and Inocybe increased to 5%. The relative abundance of Russula in soil enriched with wood residues and sawdust increased to 9% and 5%, respectively. Mycorrhizal fungi, e.g., of the genus Ąmanita, Rusula, which formed root mycorrhizae, not only increased the root receiving area many times over, but also protected the roots (mechanically and chemically from pathogens). Altogether, the observed positive changes increase the chances that the first generation of pines will survive on the ground.

Prediction of CO2 emission from arid soil after addition of exogenous organic matter

Organic amendment application is an efficient technique that could contribute to stock organic C in soil reducing CO2 and enhancing soil fertility. However, some types of amendments increase CO2 emission from soil such as soil respiration. Modeling soil respiration after addition of exogenous organic matter will help to provide carbon fates and then to choose the most efficient amendment.Empirical method was used to develop a pseudo-empirical model based on soil wealth and organic matter composition. These data were obtained during an incubation experiment. The obtained model simulated immediate CO2 emission from the soil in controlled and natural conditions following carbon input based on the chemical and biochemical compositions of the organic matter applied in the soil. The simulated values showed an excellent correspondence with the amounts of CO2 emitted from an arid soil after organic matter application. This model allowed a good prediction of the exogenous organic matter mineralization. Moreover, it can be used to predict CO2 emission, as a greenhouse gas, from the soil following exogenous organic matter input. Nevertheless, this empirical model can only be applied in areas with the same climatic characteristics.

The dynamics of boron when amending agricultural soil of the Mediterranean basin with biosolids: trials in leaching columns.

There is mainly a lack of boron (B) in soils with low amounts of organic matter and in acidic and sandy soils. This is especially true in irrigated land or humid regions, where leaching can occur. The results from studying the amount of available B will reveal the status of B in the soil of a specific plot of land. The experimentation was performed as a controlled study using leaching columns. A container was placed at the end of the columns to collect the infiltrated water. Three treatments were performed by applying different amounts of biosolids (T40: 40,000kgha-1, T80: 80,000kgha-1, T120: 120,000kgha-1), as well as a blank test or control treatment (T0). We conclude that the mobility of B in soil was generally low despite the addition of organic matter and humidity to the soil. This is an indication that there is no clear risk of aquifers being contaminated with B or plants being impacted by toxicity due to this micronutrient.

Depth-related patterns in microbial community responses to complex organic matter in the western North Atlantic Ocean

Abstract. Oceanic bacterial communities process a major fraction of marine organic carbon. A substantial portion of this carbon transformation occurs in the mesopelagic zone, and a further fraction fuels bacteria in the bathypelagic zone. However, the capabilities and limitations of the diverse microbial communities at these depths to degrade high-molecular-weight (HMW) organic matter are not well constrained. Here, we compared the responses of distinct microbial communities from North Atlantic epipelagic (0–200 m), mesopelagic (200–1000 m), and bathypelagic (1000–4000 m) waters at two open-ocean stations to the same input of diatom-derived HMW particulate and dissolved organic matter. Microbial community composition and functional responses to the input of HMW organic matter – as measured by polysaccharide hydrolase, glucosidase, and peptidase activities – were very similar between the stations, which were separated by 1370 km but showed distinct patterns with depth. Changes in microbial community composition coincided with changes in enzymatic activities: as bacterial community composition changed in response to the addition of HMW organic matter, the rate and spectrum of enzymatic activities increased. In epipelagic mesocosms, the spectrum of peptidase activities became especially broad and glucosidase activities were very high, a pattern not seen at other depths, which, in contrast, were dominated by leucine aminopeptidase and had much lower peptidase and glucosidase rates in general. The spectrum of polysaccharide hydrolase activities was enhanced particularly in epipelagic and mesopelagic mesocosms, with fewer enhancements in rates or spectrum in bathypelagic waters. The timing and magnitude of these distinct functional responses to the same HMW organic matter varied with depth. Our results highlight the importance of residence times at specific depths in determining the nature and quantity of organic matter reaching the deep sea.