Carbon, nitrogen and phosphorus mineralization in two soils amended with distillery yeast

The concentrations and the seasonal changes of heavy metals and organic carbon in the sediments underlying a Zostera marina L. bed were measured monthly during one year, in two Mediterranean lagoons: Thau (France) and Venice (Italy). While at Thau sediments showed Cu (18.7+/-3.9 microg g-1) and Pb (13.8+/-3.8 microg g-1) average concentrations twofold higher than at Venice (Cu: 8.4+/-4.8 microg g-1; Pb: 6.1+/-0.70 microg g-1), the Italian site exhibited average concentrations of Fe (13383+/-955 microg g-1 versus 6098+/-1089 microg g-1 at Thau), Mn (339+/-12 microg g-1 versus 190+/-23 microg g-1 at Thau), Zn (61.6+/-12.7 microgg -1 versus 36.1+/-7.4 microg g-1 at Thau), Cr (47.3+/-7.3 microg g-1 versus 21.8+/-8.0 microg g-1 at Thau) and Ni (12.7+/-1.7 microg g-1 versus 8.9+/-3.1 microg g-1 at Thau) approximately 1.5-2 times as high as the French site. The organic carbon concentration was systematically higher at Thau (1.0+/-0.3) than at Venice (0.7+/-0.2). A significant seasonal fluctuation was found for Zn, Cu, Ni, Cr in both lagoons while no significant variations were recorded for Pb at Venice and for Cd at Thau. Some of those changes appeared to be significantly correlated with the biomass of Zostera at Thau and the concentration of organic carbon at Venice.     

Nitrogen mineralisation potential in calcareous soils amended with sewage sludge

Mineralisation of organic N is an important consideration when determining the annual amount of sewage sludge to be applied to agricultural soils. The mineralisation of sludge organic N was studied in two different textured soils (clayey and sandy soil) treated with aerobic and anaerobic sludge at two different rates (30 and 50 g sludge kg(-1) soil). The mineralisation of sludge organic N was determined during 20 weeks incubation period by analysis of inorganic N produced by a non-leached procedure. Sludge organic N mineralisation was influenced by soil type, organic N mineralisation being greater in the sandy soil (from 30% to 41%) than in the clayey soil (from 13% to 24%). Mineralisation rates decreased rapidly the first two weeks, followed by a slower decrease with time. Although total mineralisation increased with sludge addition rate, net mineralisation decreased with sludge addition rate, probably due to denitrificaton losses. The aerobically treated sludge gave higher mineralisation rates than the anaerobically treated one. The values of N0 and k for treated soils varied depending on the type of sludge and soil.     

Bacterial community structure in the rhizosphere of three cactus species from semi-arid highlands in central Mexico

The nature reserve of Tehuacan-Cuicatlan in central Mexico is known for its diversity and endemism mainly in cactus plants. Although the xerophytic flora is reasonably documented, the bacterial communities associated with these species have been largely neglected. We assessed the diversity and composition of bacterial communities in bulk (non-rhizospheric) soil and the rhizosphere of three cactus plant species: Mammillaria carnea, Opuntia pilifera and Stenocereus stellatus, approached using cultivation and molecular techniques, considering the possible effect of dry and rainy seasons. Cultivation-dependent methods were focused on putative N₂-fixers and heterotrophic aerobic bacteria, in the two media tested the values obtained for dry season samples grouped together regardless of the sample type (rhizospheric or non-rhizospheric), these groups also included the non-rhizospheric sample for rainy season, on each medium. These CFU values were smaller and significantly different from those obtained on rhizospheric samples from rainy season. Genera composition among isolates of the rhizospheric samples was very similar for each season, the most abundant taxa being α-Proteobacteria, Actinobacteria and Firmicutes. Interestingly, the genus Ochrobactrum was highly represented among rhizospheric samples, when cultured in N-free medium. The structure of the bacterial communities was approached with molecular techniques targeting partial 16S rRNA sequences such as denaturing gradient gel electrophoresis and serial analysis of ribosomal sequence tags. Under these approaches, the most represented bacterial phyla were Actinobacteria, Proteobacteria and Acidobacteria. The first two were also highly represented when using isolation techniques.     

Carbon and nitrogen mineralization in soil amended with phenanthrene,anthracene and irradiated sewage sludge

Lactic acid production by Lactobacillus brevis and Lactobacillus pentosus on a hemicellulose hydrolysate (HH) of wet-oxidized wheat straw was evaluated. The potential of 11-12 g/l fermentable sugars was released from the HH through either enzymatic or acidic pretreatment. Fermentation of added xylose in untreated HH after wet-oxidation, showed no inhibition on the lactic acid production by either Lb. pentosus or Lb. brevis. Lb. pentosus produced lactate corresponding to 88% of the theoretical maximum yield regardless of the hydrolysis method, whereas Lb. brevis produced 51% and 61% of the theoretical maximum yield after enzymatic, or acid treatment of HH, respectively. Individually, neither of the two strains were able to fully utilize the relatively broad spectra of sugars released by the acid and enzyme treatments; however, lactic acid production increased to 95% of the theoretical maximum yield by co-inoculation of both strains. Xylulose was the main sugar released after enzymatic treatment of HH with Celluclast. Lb. brevis was able to degrade xylobiose, but was unable to assimilate xylulose, whereas Lb. pentosus was able to assimilate xylulose but unable to degrade xylobiose.     

Uptake of phosphorus by plants in relation to carbon dioxide production and organic phosphorus mineralization in soils

Summary In previous work, the yield of phosphorus in plants grown in the greenhouse on 36 alkaline soils was correlated significantly with the organic phosphorus mineralized during incubation of the soils in the laboratory, independently of the labile inorganic phosphorus. In this investigation, the same soils were used to test the hypothesis that the apparent organic-phosphorus effect observed previously was an indirect effect of CO₂ evolved from soil organic matter in increasing the susceptibility of the inorganic phosphorus to uptake by plants. The hypothesis was tested on the basis of measurements of CO₂ evolved and organic phosphorus mineralized concurrently during incubation of the soils in the laboratory. Statistical tests showed that the yield of phosphorus in the plants was correlated significantly with the organic phosphorus mineralized, independently of correlations with CO₂ evolved and labile inorganic phosphorus; the yield of phosphorus in plants, however, was not correlated significantly with CO₂ evolved, independently of correlations with organic phosphorus mineralized and labile inorganic phosphorus. The results thus provide no justification for discarding the organic-phosphorus theory and for substituting the CO₂ theory in its place.Journal Paper No. J-5691 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1183.Rockefeller Foundation Fellow and Professor of Soils.     

Phytoextraction capacity of the Chenopodium album L. grown on soil amended with tannery sludge

The metal accumulation potential of Chenopodium album L. grown on various amendments of tannery sludge (TS) was studied after 60 days of sapling planted. The analysis of the results showed that the levels of pH, cation exchange capacity, organic carbon, organic matter and DTPA extractable metals (except Mn) of amendments increased by the addition of tannery sludge ratio. Shoot length of the plant increased by the addition of sludge, whereas, no marked change was observed in root length, fresh and dry weight of the plant. Accumulation of the metals in the plants was found in the order; Fe > Mn > Zn > Cr > Cu > Pb > Ni > Cd. Translocation of toxic metals (Cr, Pb, Cd) in different parts of the tested plant was found in the order; leaves > stems > roots. An increase in the photosynthetic pigments, carotenoid and leaf protein contents of the plants were found to increase with increase in sludge amendments. Correlation analysis between metal accumulation in the plants with DTPA extractable metals emphasized that Mn, Ni, Cr, Pb and Cd showed positive correlation (p < 0.05), whereas, Fe, Zn and Cu showed negative correlation. Transfer factor analysis emphasized that 10% TS amendments were suitable for phytoextraction of Cr. Overall analysis of the data exhibited that the plants may be used for phytoextraction of Cr from tannery waste contaminated soil as most of the metal was accumulated in harvestable part which is a matter of serious concern, whenever used for edible purposes.     

Nitrogen and carbon mineralization during incubation of two Bangladesh soils in relation to temperature

Summary At temperatures of 20°, 30°, 40°, 50° and 60°C in a Gangetic alluvial soil (G soil, pH 7.6) N-mineralization and nitrification increased with temperature up to 40°C and mineralized N accumulated entirely as nitrate. At 50° and 60°C mineralized N was relatively low and no nitrification occurred. In the Red soil (R soil, pH 5.2) mineralized N increased with temperature up to 40°C, was somewhat less at 50°C and was at a maximum at 60°C. Nitrification was maximum at 30°C but did not occur at 50° and 60°C. In the G soil C-mineralization increased considerably with temperature, whilst in the R soil there were only small differences due to temperature.     

稻田土壤有机碳矿化及其激发效应对磷添加的响应

采用室内模拟培养和¹³C同位素标记技术相结合的研究方法,探讨了在葡萄糖与无机氮肥共施的条件下,土壤有机碳矿化及其激发效应对外源磷添加的响应,以揭示土壤有机碳矿化的碳磷耦合调控机制.结果表明:外源磷的输入加快了CO_2的释放,但抑制了CH_4的释放;在整个土壤淹水培养期间,磷添加抑制了土壤碳矿化释放CH_4总量的53.1%,其中外源葡萄糖-¹³C矿化成¹³CH_4的总量降低了70.5%;磷添加促使通过微生物转化的葡萄糖-¹³C向易利用态碳库的分配比例增加了3.6%,显著提高土壤有机碳快库矿化速率,缩短土壤碳矿化周期.土壤培养前期,外源有机质的添加表现为短暂的负激发效应;随着葡萄糖不断矿化分解,CO_2累积激发效应(PE_{CO_2})总体上呈现先增加后下降的趋势,而CH_4累积激发效应(PE_{CH_4})稳步增加最终保持基本稳定状态;培养结束时(100 d),在磷添加条件下,PE_{CO_2}增强32.3%,PE_{CH_4}显著降低93.4%.冗余分析和Pearson分析表明,电导率、氧化还原电位和溶解有机碳对稻田土壤碳矿化的影响最为显著;速效磷与¹³CH_4、PE_{CH_4}呈极显著负相关.在外源有机质添加条件下,磷的添加能够抑制CH_4排放及其激发效应,促进土壤有机质的矿化和养分释放,提高土壤原有有机碳的可利用性,促进稻田土壤有机碳循环.     

Dynamics of carbon,nitrogen and phosphorus in soil amended with irradiated,pasteurized and limed biosolids

Sewage biosolids contain high concentrations of pathogens, which limits their use as soil amendment. This study investigated how application of lime (Ca(OH)2), irradiation, or pasteurization reduced pathogens in biosolids and how its application affected soil characteristics. A soil sampled outside the canopy of Mesquite trees (Prosopis laevigata) and from a pasture at Lerma (Mexico) was amended with treated or untreated biosolids, characterized and incubated aerobically while dynamics of carbon (C), nitrogen (N) and phosphorus (P) were monitored. Heavy metals concentrations in the biosolids were low, so it was of excellent quality (USEPA). The amount of pathogens in the biosolids made it a class "B" (USEPA) which can be used in forests. Only irradiation sufficiently reduced faecal coliforms to make it a class "A" biosolids without restrictions in application. C mineralization increased significantly when biosolids were added, but not concentrations of available P (P < 0.05). Ammonium (NH4+) concentrations in soil amended with biosolids were higher compared to unamended soil, but not the concentrations of nitrate (NO3-) except when biosolids treated with Ca(OH)2 was added to the Lerma soil.     

Speciation and dynamics of phosphorus in some organically amended soils of southwestern Nigeria

Availability of soil phosphorus (P) is a function of its dynamics and can be improved by using organic amendments. Experiments were carried out to determine the effect of poultry manure (PM) on soil P fractions and bioavailability to soybean (Glycine max). Soils from ten farmers’ fields in Southwest Nigeria, were used for incubation and pot experiments. Treatments were five rates of PM (0, 2.5, 5.0, 7.5 and 10 t ha^?1). Triplicate units in incubation and pot experiments were arranged in Completely Randomised Design. Soybean was grown for three consecutive growth cycles of seven weeks each and soil samples were analysed for Saloid P, Al-P, Fe-P, Ca-P, occluded P, reductant soluble P, and residual P. Results indicated that Fe-P was the dominant active inorganic P in the soils while residual P was the dominant inactive inorganic-P in most of the soils. In the pot experiment, application of poultry manure significantly increased organic P in the soils in the first growth cycle, but decreased slightly in second growth cycle. Highest and lowest (P ≤ 0.05) organic P values were observed in soil samples from Ayetoro and Odeda, respectively. In the pot experiment, application of PM reduced P fixation and occluded P fraction in the soils. There was general increase in available P in most of the soils considered despite increase or decrease in other forms of P. Poultry manure reduced the fixation of P and release of occluded phosphorus. Generally, Poultry manure significantly improved soil P fractions and plant P tissue concentrations.     

Minimizing phosphorus release from newly flooded organic soils amended with calcium silicate slag: a pilot study

A pilot study was conducted using commercially available forms of calcium silicate (CaSiO₃) slag as a soil amendment to reduce phosphorus (P) release from an organic soil after flooding. Broadcasting CaSiO₃ slag on top of the soil reduced the flux of soil P up to 84% compared to an unamended soil control. However, incorporation of CaSiO₃ slag into the soil was only minimally effective at reducing P release. These materials have a potential use in the construction of treatment wetlands in south Florida. Further work is needed to better define reaction mechanisms, investigate the long-term treatment efficacy of these materials and address other environmental questions concerning their use.     

Effect of mercuric chloride on carbon mineralization in soils

Summary The short and long-term effects of mercuric chloride amendment of five surface soils from southeastern Montana on carbon mineralization was studied. Short-term radiorespirometric studies utilizing a glucose substrate indicated Hg levels greater than 40 g/g soil were required for significant inhibition in all soils tested. Under chronic exposure conditions, levels from 0.1 to greater than 100 g Hg/g soil proved necessary for inhibition.     

Nitrogen deposition promotes phosphorus uptake of plants in a semi-arid temperate grassland

Plant and Soil - Nitrogen (N) deposition greatly influences ecosystem processes through the alteration of plant nutrition; however, there is limited understanding about the effects of phosphorus...     

Nitrogen and phosphorus dynamics in three central Texas impoundments

Summary The entrapment of nitrogen and phosphorus by three man-made impoundments in central Texas was studied from February, 1969 through January, 1970. Each impoundment was sampled at four-hour intervals during February, May, August, and November. During the other months, each station was sampled at midafternoon and between 2 A.M. and dawn.Annual nitrogen budgets for the three lakes show they all serve as nutrient traps. In general, retention of nitrogen is a function of increased autotrophic assimilation during the growing season.All three lakes lost phosphorus on an annual basis. This loss was attributed to the small demand by autotrophs and the addition of phosphorus from allochthonous sources around the lakes and from sewage plant effluents upstream. Based on nitrogen-phosphorus ratios, it is postulated that nitrogen is the nutrient factor which limits algal growth in all three impoundments.     

Emission of CO2 from biochar‐amended soils and implications for soil organic carbon

Soil amendment with pyrogenic organic matter (PyOM), also named biochar, is claimed to sequester carbon (C). However, possible interactions between PyOM and native soil organic carbon (SOC) may accelerate the loss of SOC, thus reducing PyOM's C sequestration potential. We combined the results of 46 studies in a meta‐analysis to investigate changes in CO₂ emission of PyOM‐amended soils and to identify the causes of these changes and the possible factors involved. Our results showed a statistically significant increase of 28% in CO₂ emission from PyOM‐amended soils. When grouped by PyOM C (PyC):SOC ratios, the group of studies with a ratio >2 showed a significant increase in CO₂ emissions, but those with a ratio <2 showed no significant effect of PyOM application on CO₂ emission. Our data are consistent with the hypothesis that increased CO₂ emission after PyOM addition is additive and mainly derived from PyOM's labile C fractions. The PyC:SOC ratio provided the best predictor of increases in CO₂ production after PyOM addition to soil. This meta‐analysis highlights the importance of taking into account the amount of applied PyC in relation to SOC for designing future decomposition experiments.     

Spatial relationships between cacti and nurse shrubs in a semi-arid environment in central Mexico

Abstract. The Zapotitlán de las Salinas valley, central Mexico, harbours a high diversity of cacti. Pattern analysis indicated that the establishment of two columnar cacti, Neobuxbaumia tetetzo and Cephalocereus hoppenstedtii, and of three small globose cacti, Coryphantapallida, Mammillaria colina andM casoi, is aggregated and associated with perennial nurse shrubs. Some nurse species, Castela tortuosa, Caesalpinia melanadenia and Eupatorium spinosarum have a higher number of cacti beneath their canopies than would be expected by chance. A replacement pattern was found between the columnar cacti and their nurses, an aspect which was not found with the globose cacti. Following the assumption that protection against excessive radiation is the main factor determining the nurse effect, the azimuth orientation of the cacti with respect to their nurses was evaluated. Only Coryphanta pallida presented a non-random distribution with a tendency towards the North and West. The difference in maximum temperature between the soil surface under the different nurse species and of open spaces, which is reached at midday, was 16 °C. No significant differences were found in beneath-canopy temperatures for the three nurse species considered. Soil nitrogen levels were significantly lower beneath the different nurse plants than in open spaces. This result suggests that soil fertility is not an important factor in the nurse-plant phenomenon in Zapotitlán.     

Nitrogen mineralization and potential nitrification at different depths in acid forest soils

Yield decline of cereals grown in monoculture may be alleviated with alternative crop management strategies. Crop rotation and optimized tillage and fertilizer management can contribute to more sustainable food and fiber production in the long-term by increasing diversity, maintaining soil organic matter (SOM), and reducing adverse effects of excessive N application on water quality. We investigated the effects of crop sequence, tillage, and N fertilization on long-term grain production on an alluvial, silty clay loam soil in southcentral Texas. Crop sequences consisted of monoculture sorghum (Sorghum bicolor (L.) Moench,) wheat (Triticum aestivum L.), and soybean (Glycine max (L.) Merr), wheat/soybean double-crop, and rotation of sorghum with wheat/soybean. Grain yields tended to be lower with no tillage (NT) than with conventional tillage (CT) early in the study and became more similar after 11 years. Nitrogen fertilizer required to produce 95% to maximum sorghum yield was similar for monoculture and rotation upon initiation of the experiment and averaged 16 and 11 mg N g^-1 grain with NT and CT, respectively. After 11 years, however, the N fertilizer requirement became similar for both tillage regimes, but was greater in monoculture (17 mg N g^-1 grain) than in rotation (12 mg N g^-1 grain). Crop sequences with double-cropping resulted in greater land use efficiency because similar or lower amounts of N fertilizer were required to produce equivalent grain than with less intensive monoculture systems. These more intensive crop sequences produced more stover with higher N quality primarily due to the inclusion of soybean in the rotation. Large quantities of stover that remained on the soil surface with NT led to greater SOM content, which increased the internal cycling of nutrients in this soil. In southcentral Texas, where rainfall averages nearly 1000 mm yr^-1, more intensive cropping of sorghum, wheat, and soybean with moderate N fertilization using reduced tillage can increase grain production and potentially decrease N losses to the environment by cycling more N into the crop-SOM system.     

Reducing carbon: phosphorus ratio can enhance microbial phytin mineralization and lessen competition with maize for phosphorus

We tested the hypothesis that reducing the carbon (C):Phosphorus (P) ratio in rhizosphere soil would reduce bacterial competition with the plant for P from phytin, which would then increase phytin use efficiency for the plant. A three-factor pot experiment was carried out to study the effect of inoculation with a phytin-mineralizing bacterium, Pseudomonas alcaligenes (PA), on maize P uptake from phytin. Two levels of organic P, two levels of inorganic P, and three different PA inoculation treatments were used. When maize plants were grown in low available P soil with phytin, PA transformed soil P into microbial biomass P, which caused competition for available P with plant and inhibited plant uptake. When 5 mg P kg^?1 as KH₂PO₄ was added, inoculation with PA increased soil acid phosphatase activity which enhanced the mineralization rate of phytin. PA mobilized more P than it immobilized in microbial pool and enhanced plant P uptake. We conclude that the decreased C:P ratio by adding small amount of inorganic P in the rhizosphere could drive phytin mineralization by the bacteria and improve plant P nutrition.     

Phosphorus fertilizer recovery from calcareous soils amended with humic and fulvic acids

Precipitation of Ca phosphates negatively affects recovery by plants of P fertilizer applied to calcareous soils, but organic matter slows the precipitation of poorly soluble Ca phosphates. To study the effect of high molecular weight organic compounds on the recovery of applied P, a mixture of humic and fulvic acids was applied to calcareous soils with different levels of salinity and Na saturation which were fertilized with 200 and 2000 mg P kg^–1 as NH₄H₂PO₄. Recovery was measured as the ratio of increment in Olsen P-to-applied P after 30, 60 and 150 days, and associated P forms were studied using sequential chemical fractionation and ³¹P NMR spectroscopy. Application of the humic-fulvic acid mixture (HFA) increased the amount of applied P recovered as Olsen P in all the soils except in one soil with the highest Na saturation. In soils with high Ca saturation and high Olsen P, recovery increased from < 15% in the absence of amendment to > 40% at a 5 g HFA kg^–1 amendment rate (30 days incubation and 200 mg P kg^–1 fertilizer rate). This is ascribed to inhibition of the precipitation of poorly soluble Ca phosphates, consistent with the sequential chemical extraction (reduction of the HCl extractable P) and P concentration in 0.01 M CaCl₂ (1:10 soil:solution ratio) extracts. ³¹P NMR spectra revealed that in non-amended samples, most spectral shifts were due to poorly soluble P compounds (carbonate apatite); on the other hand, at the 5 g HFA kg^–1 rate, significant amounts of amorphous Ca phosphate and dicalcium phosphate dihydrate (DCDP) were identified. The increase in the recovery of applied P due to HFA reveals a positive effect of the application of organic matter as soil amendments on the efficiency of P fertilizers and also explains that manures and other organic sources of P were more efficient increasing available P than inorganic P fertilizers in calcareous soils.