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PubMed1999

Transgenically enhanced sorbitol synthesis facilitates phloem boron transport and increases tolerance of tobacco to boron deficiency

The mobility of elements within plants contributes to a plant species' tolerance of nutrient deficiencies in the soil. The genetic manipulation of within-plant nutrient movement may therefore provide a means to enhance plant growth under conditions of variable soil nutrient availability. In these experiments tobacco (Nicotiana tabacum) was engineered to synthesize sorbitol, and the resultant effect on phloem mobility of boron (B) was determined. In contrast to wild-type tobacco, transgenic tobacco plants containing sorbitol exhibit a marked increase in within-plant B mobility and a resultant increase in plant growth and yield when grown with limited or interrupted soil B supply. Growth of transgenic tobacco could be maintained by reutilization of B present in mature tissues or from B supplied as a foliar application to mature leaves. In contrast, B present in mature leaves of control tobacco lines could not be used to provide the B requirements for new plant growth. 10B-labeling experiments verified that B is phloem mobile in transgenic tobacco but is immobile in control lines. These results demonstrate that the transgenic enhancement of within-plant nutrient mobility is a viable approach to improve plant tolerance of nutrient stress.

Journal Article↗
PubMed2001

[Changes of crop yields and soil fertility under long-term application of fertilizer and recycled nutrients in manure on a black soil].

The results from a field experiment over thirteen years on a black soil in Northeast China indicated that nitrogen fertilizer increased crop yields by 724 kg.hm-2 per year on average, with an increase rate of 27.5% and about 9.4 kg increased yield from 1 kg applied N. In the early stage, the crop yields almost gave no response to phosphorus fertilizer, owing to the high level of soil available phosphorus at the beginning of the experiment. The average increase of crop yields by phosphorus in thirteen years was only 241 kg.hm-2 per year, with an increase rate of 7%, about 12.7 kg increased yield from 1 kg applied P. Annual application of recycled pig manure made by 80% of harvested grain fed to pigs and the stolks as bedding materials could increase crop yields by 268, 258 and 255 kg.hm-2 per year with an increase rate of 9.8%, 7.6% and 7.0%, based on no fertilizer, with N and with P and N, respectively. There was a trend that the effect of recycled manure on crop yield was gradually increased during the period of experiment, implying the existence of accumulative residual effect from the manure.

Agriculture↗
PubMed2005

Base cation stimulation of mycorrhization and photosynthesis of sugar maple on acid soils are coupled by foliar nutrient dynamics.

The nutritional benefits that mycorrhizal associations provide to plants may be constrained by acidic soil conditions resulting in decreased photosynthetic function. Sugar maple (Acer saccharum) and red maple (Acer rubrum) seedlings were grown on a native acidic (pH 4.1) soil both unamended and amended with base cations (pH 6.2). In a second study a fungicide treatment was included. Foliar nutrition, mycorrhizal colonization, photosynthesis and their relationships were assessed. On the native soil, red maple maintained higher levels of mycorrhizal colonization and photosynthesis than sugar maple but showed little response to base cation amendments. Mycorrhizal colonization and photosynthesis of sugar maple increased significantly in response to base cation amendments. Correlations were observed among mycorrhizal colonization, foliar nutrition and photosynthesis. The fungicide treatment indicated that 50% of the base cation-induced increase in sugar maple photosynthesis was mycorrhiza related. The results suggest that base cation stimulation of mycorrhization and photosynthesis of sugar maple on acid soils are coupled by foliar nutrient dynamics. Red maple exhibits much less sensitivity to these same edaphic conditions.

Acer↗
PubMed2004

Monitoring physiological status of GFP-tagged Pseudomonas fluorescens SBW25 under different nutrient conditions and in soil by flow cytometry.

Pseudomonas fluorescens SBW25, a plant growth promoting bacterium, has been widely studied due to its potential as an inoculum for improving crop yields. Environmental inoculants are usually applied on seeds or directly to soil and to effectively promote plant growth they need to be viable and active. However, it is difficult to study the physiological status of specific microorganisms in complex environments, such as soil. In this study, our aim was to use molecular tools to specifically monitor the physiological status of P. fluorescens SBW25 in soil and in pure cultures incubated under different nutritional conditions. The cells were previously tagged with marker genes (encoding green fluorescent protein and bacterial luciferase) to specifically track the cells in environmental samples. The physiological status of the cells was determined using the viability stains 5-cyano-2,3-ditolyl-tetrazolium chloride (CTC) and propidium iodide (PI), which stain active and dead cells, respectively. Luciferase activity was used to monitor the metabolic activity of the population. Most of the cells died after incubation for nine days in nutrient rich medium. By contrast when incubated under starvation conditions, most of the population was not stained with CTC or PI (i.e. intact but inactive cells), indicating that most of the cells were presumably dormant. In soil, a large fraction of the SBW25 cell population became inactive and died, as determined by a decline in luciferase activity and CTC-stained cells, an increase in PI-stained cells, and an inability of the cells to be cultured on agar medium. However, approximately 60% of the population was unstained, presumably indicating that the cells entered a state of dormancy in soil similar to that observed under starvation conditions in pure cultures. These results demonstrate the applicability of this approach for monitoring the physiological status of specific cells under stress conditions, such as those experienced by environmental inoculants in soil.

Biomarkers↗
PubMed2006

[Changes of crop yield and soil fertility under long-term fertilization and nutrients-recycling and reutilization on a black soil: IV. Soil organic carbon and its fractions].

A long-term experiment was conducted on a black soil of Northeast China to study the effects of applying chemical fertilizers and recycled organic manure (ROM) on the changes of soil organic carbon and its fractions. The results showed that from 1985 to 2004, soil total organic carbon (TOC) decreased by 7.83% in control,4.56% in N application, 1.61% in N + P application, and 5.56% in ROM application, but increased by 0.33% in N + P + K application. Comparing with single application of ROM, its application with chemical fertilizers, i. e., N + ROM, N + P + ROM, and N + P + K + ROM, increased the TOC concentration by 0.35%, 1.05% and 0.64%, respectively. The readily oxidized carbon (ROC) in fertilization treatments was increased by 8.64% to approximately 28.4%, and the increment was higher in treatments of chemical fertilizers plus ROM than in treatments of chemical fertilizers. The ROC was significantly correlated with soil TOC (Y = 14.192X + 23.9, R2 = 0.802) and stalk yields (Y = 19032X - 7950.6, R2 = 0.759). Light fraction organic carbon (LF-C) had the same trends with ROC. After 20 years fertilization, the organic carbon in soil humic acid and fulvic acid was decreased by 1.64% to approximately 26.23% and 2.33% to approximately 28.68%, respectively, but in treatments of chemical fertilizers plus ROM, the decreasing trend was slowed down.

Biomass↗
PubMed2004

Developmental physiology of cluster-root carboxylate synthesis and exudation in harsh hakea. Expression of phosphoenolpyruvate carboxylase and the alternative oxidase.

Harsh hakea (Hakea prostrata R.Br.) is a member of the Proteaceae family, which is highly represented on the extremely nutrient-impoverished soils in southwest Australia. When phosphorus is limiting, harsh hakea develops proteoid or cluster roots that release carboxylates that mobilize sparingly soluble phosphate in the rhizosphere. To investigate the physiology underlying the synthesis and exudation of carboxylates from cluster roots in Proteaceae, we measured O2 consumption, CO2 release, internal carboxylate concentrations and carboxylate exudation, and the abundance of the enzymes phosphoenolpyruvate carboxylase and alternative oxidase (AOX) over a 3-week time course of cluster-root development. Peak rates of citrate and malate exudation were observed from 12- to 13-d-old cluster roots, preceded by a reduction in cluster-root total protein levels and a reduced rate of O2 consumption. In harsh hakea, phosphoenolpyruvate carboxylase expression was relatively constant in cluster roots, regardless of developmental stage. During cluster-root maturation, however, the expression of AOX protein increased prior to the time when citrate and malate exudation peaked. This increase in AOX protein levels is presumably needed to allow a greater flow of electrons through the mitochondrial electron transport chain in the absence of rapid ATP turnover. Citrate and isocitrate synthesis and accumulation contributed in a major way to the subsequent burst of citrate and malate exudation. Phosphorus accumulated by harsh hakea cluster roots was remobilized during senescence as part of their efficient P cycling strategy for growth on nutrient impoverished soils.

Carbon Dioxide↗
PubMed2005

[Preliminary studies on the nutrient characters of different kinds of Chinese goldthread soil].

OBJECTIVE: To study the changes of nutrient contents in Chinese goldthread soil before and after planting Coptis chinensis. METHOD: The soil in Shizhu, Chongqing, was analyzed for nutrient contents. RESULT AND CONCLUSION: The results indicated that the preplanted soil was strongly acidic and the levels of organic matter, total nitrogen and potassium were high. However, the content of total phosphorus was very low; so were the contents of other eleven nutrients. Variations of nutrients except zinc and molybdenum were large. After four years of planting C. chinensis, the soil pH was increased. Contents of organic matters, manganese, zinc and boron were increased, while the contents of iron and copper were decreased. In general, the variance coefficient of all nutrient elements and the difference of soil fertility were decreased.

China↗
PubMed2001

Estimating toxic damage to soil ecosystems from soil organic matter profiles.

Concentrations of particulate and total organic matter were measured in upper soil profiles at 26 sites as a potential means to identify toxic damage to soil ecosystems. Because soil organic matter plays a role in cycling nutrients, aerating soil, retaining water, and maintaining tilth, a significant reduction in organic matter content in a soil profile is not just evidence of a change in ecosystem function, but of damage to that soil ecosystem. Reference sites were selected for comparison to contaminated sites, and additional sites were selected to illustrate how variables other than environmental contaminants might affect the soil organic matter profile. The survey was undertaken on the supposition that environmental contaminants and other stressors reduce the activity of earthworms and other macrofauna, inhibiting the incorporation of organic matter into the soil profile. The profiles of the unstressed soils showed a continuous decrease in organic matter content from the uppermost mineral soil layer (0-2.5 cm) down to 15 cm. Stressed soils showed an abrupt decrease in soil organic matter content below a depth of 2.5 cm. The 2.5-5.0 cm layer of stressed soils--such as found in a pine barren, an orchard, sites contaminated with zinc, and a site with compacted soil--had less than 4% total organic matter and less than 1% particulate organic matter. However, damaged soil ecosystems were best identified by comparison of their profiles to the profiles of closely matched reference soils, rather than by comparison to these absolute values. The presence or absence of earthworms offered a partial explanation of observed differences in soil organic matter profiles.

Animals↗
PubMed1998

Calcium, magnesium, and potassium in hair of deer from areas of contrasting soil productivity.

Differences in mineral nutrient composition of soils have been considered to affect health and population characteristics of free-ranging animals, particularly herbivores. Contents of Ca, Mg, and K in hair of female fawn white-tailed deer (Odocoileus virginianus) were measured for eight consecutive years to determine if soil and annual effects occurred in two areas of contrasting soil productivity in Illinois. Soil differences may account for some of the autumnal weight difference (7.2 kg for 4 yrs of observation) observed in fawn does from the areas. Ca, Mg, and K were assayed, because these macronutrients were known to differ in soils of the areas and were presumed to differ in forages. In 6 of the 8 yrs, at least one element was significantly different (P < or = 0.05) between areas. Significant (P < or = 0.05) differences for K occurred in 5 yr, for Ca in 4 yr, and for Mg in 2 yr. Ca and Mg were lower in hair in 7 yr from deer collected from the area in which extractable Ca and Mg were higher in soils; that is, hair Ca and Mg levels tended to be inversely related to levels of plant-available Ca and Mg in soil. For 7 of the 8 yr, K content was lower in hair from the area of lower soil K content. Within one area, between-year differences occurred for Ca and K and for Ca and Mg in the other area. Between-year differences in diet selection and annual climatic effects on mineral uptake of forages, among other factors, may account for some of the latter differences. Results for hair analyses suggest that macronutrient differences in Ca, Mg, and K occur in the diets of these populations and may account for some of the weight difference observed between the areas.

Animals↗
PubMed2001

Synchronizing N release from organic residues: opportunities for integrated management of N.

In intensive cropping systems, mineral nitrogen (N) fertilizers represent the largest component of the N cycle because the indigenous N supply is not adequate. The requirement for mineral fertilizer may be reduced with the use of organic nutrient sources. A more realistic use of organic matter, particularly in sub-Saharan Africa due to limited amounts and availability, is the combined use of organic nutrient sources and mineral fertilizers. The beneficial effects of integrated use of inorganic fertilizers and organic manures on improved nutrient recoveries, soil moisture retention, cation exchange capacity, and erosion control have been reported. However, there are as many reports indicating negligible benefits or even disadvantages of combining nutrient sources on crop production. This is not surprising given the combination of organic residue sources, soils, climatic, crops, and management factors that influence nutrient dynamics. The most widely accepted function of organic materials is improving the nutrient availability to crops by supplying N. The key to both improving efficiency of N use and reducing N losses is synchronization of N supply from soil, biological N2 fixation, organic residues, and inorganic fertilizers with the crop N demand. Organic materials are not magic; N losses also result from their use. Controlling N release from organic sources depends on their nutrient content and quality, soil properties, and the environmental and management factors. This paper will synthesize the information generated from integrated nutrient management trials in sub-Saharan Africa and the Philippines. Management strategies based on an organic resources database and a dynamic soil-crop simulation model are used to identify organic sources as N fertilizers or soil amendments. The decision support tools are also used to attain optimum synchrony between release from organic sources and soils with crop N demand.

Africa South of the Sahara↗
PubMed2004

[Changes of soil chemical properties in sheep urine patches in Inner Mongolia steppe].

Sheep play an important role in the nutrient cycling in extensively grazed grasslands, mainly through their annual return of around 5-25 kg N in the shape of urine. This return changes the temporal distribution of nutrients in soil and alters their bioavailability. Urine patches are the most important areas of the transformation and cycling of nutrients in the grazed grasslands. In order to make known the changes of soil chemical properties in sheep urine patches, an experiment was set up in the typical steppe area of central Inner Mongolia. The results indicated that soil pH value reached the maximum on the second day after urine excretion, and then declined. It maintained at around 6.5 from the 58th day, which was under the level of the control. Soil dissolved organic carbon (DOC) in urine patches exhibited the identical changing characteristics with soil pH, and had a significantly (P < 0.01) positive correlation with it. Soil total dissolved phosphorus (TDP) increased significantly (P < 0.05) after urine excretion, and reached the maximum at the 2nd day. The percentage of molybdate reactive phosphorus (MRP), dissolved organic phosphorus (DOP) and dissolved condensed phosphorus (DCP) showed significantly two changing phases, and there existed significantly (P < 0.05) negative correlations between MRP, DOP and DCP. Soil NH4+-N reached the maximum on the 2nd day after urine excretion and then declined, while soil NO3(-)-N increased significantly after 14 days and reached the maximum on the 21st day, showing significant "double peaks" characteristics. Soil dissolved organic nitrogen (DON) also increased significantly after urine excretion.

Animal Feed↗
PubMed2001

Bioremediation of sterile agricultural soils polluted with crude petroleum by application of the soil bacterium, Pseudomonas putida, with inorganic nutrient supplementations.

The effects of bioremediation program of sterile agricultural soils contaminated with crude petroleum were determined with a view to developing a suitable technique for rehabilitation of similar environments upon pollution by oil spillage. Sterile soils inoculated with the soil bacterium, Pseudomonas putida (PP), with inorganic nutrients monitoring and supplementation constituted the experimental set-ups (ESU). The control set-ups (CSU) contained all the materials present in ESU except that they were not inoculated with PP. In ESU at week 9, the oil pollutant was completely biodegraded, and the inorganic nutrient ions, particularly PO4(-3) and NO3(-1), were significantly utilized. In contrast, there were no significant changes in the concentrations of oil and inorganic nutrients in CSU. Also, the percentage germination and growth profiles of cress seeds (Lepidium sp.) planted as evidence of the recovery of the oil-impacted soils were poor in CSU (27.5%) with pronounced abnormal morphology when compared with the results obtained for ESU (98.8%). Inoculation of PP with addition of appropriate inorganic nutrients may be a suitable method for a rapid rehabilitation of agricultural land upon pollution with crude petroleum.

Biodegradation, Environmental↗
PubMed1999

Stress Survival of a Genetically Engineered Pseudomonas in Soil Slurries: Cytochrome P-450cam-Catalyzed Dehalogenation of Chlorinated Hydrocarbons.

Biological treatment of hazardous chemical wastes has potential as an effective, practical, and economically viable process in above the ground treatment systems that consist of both genetically engineered microorganisms (GEMs) and bioreactors with process control instruments to create ideal conditions for biodegradation. A strain of Pseudomonas putida coexpressing cytochrome P-450cam and luciferase (lux) that provides both the reductive detoxification potential of the hemoprotein and a mechanism for its reduction in the absence of "normal" P-450 redox partners was evaluated for its ability to survive and remain metabolically competent under nutrient stress in soil slurry microcosms. More than 74% of the cells of engineered Pseudomonas were culturable after 7 days of multiple nutrient (C,N,P) starvation. The diagnostic luminescence and carbon monoxide-difference spectra for the two engineered traits could be detected in a significant fraction of the surviving population. The GEM could be revived after repeated desiccation and starvation using Luria broth, benzoate, or citrate as nutrients. Soil slurries inoculated with the GEM transformed hexachloroethane (HCE) to tetrachloroethylene (tetraCE) 8-10-fold faster than uninoculated slurries. The GEM also transformed the insecticide, gamma-HCH (gamma-3,4,5,6-hexachlorocyclhexene), to gamma-3,4,5,6-tetrachlorocyclohexene (gammatetraCH) in soil slurries under subatmospheric conditions. These results indicate that GEMs can be constructed with broad substrate range detoxification catalysts such as cytochrome P-450 for remediation.

Journal Article↗
PubMed2006

Effects of fire on major forest ecosystem processes: an overview.

Fire and fire ecology are among the best-studied topics in contemporary ecosystem ecology. The large body of existing literature on fire and fire ecology indicates an urgent need to synthesize the information on the pattern of fire effects on ecosystem composition, structure, and functions for application in fire and ecosystem management. Understanding fire effects and underlying principles are critical to reduce the risk of uncharacteristic wildfires and for proper use of fire as an effective management tool toward management goals. This overview is a synthesis of current knowledge on major effects of fire on fire-prone ecosystems, particularly those in the boreal and temperate regions of the North America. Four closely related ecosystem processes in vegetation dynamics, nutrient cycling, soil and belowground process and water relations were discussed with emphases on fire as the driving force. Clearly, fire can shape ecosystem composition, structure and functions by selecting fire adapted species and removing other susceptible species, releasing nutrients from the biomass and improving nutrient cycling, affecting soil properties through changing soil microbial activities and water relations, and creating heterogeneous mosaics, which in turn, can further influence fire behavior and ecological processes. Fire as a destructive force can rapidly consume large amount of biomass and cause negative impacts such as post-fire soil erosion and water runoff, and air pollution; however, as a constructive force fire is also responsible for maintaining the health and perpetuity of certain fire-dependent ecosystems. Considering the unique ecological roles of fire in mediating and regulating ecosystems, fire should be incorporated as an integral component of ecosystems and management. However, the effects of fire on an ecosystem depend on the fire regime, vegetation type, climate, physical environments, and the scale of time and space of assessment. More ecosystem-specific studies are needed in future, especially those focusing on temporal and spatial variations of fire effects through long-term experimental monitoring and modeling.

Air Pollution↗
PubMed1995

Growth and nutrient use efficiency of water tupelo seedlings in flooded and well-drained soil.

Growth characteristics and nutrient utilization rate of Nyssa aquatica L. seedlings grown in pots containing flooded or well-drained soil were compared in a greenhouse study. For most of the growing season, relative height and diameter growth rates, and biomass accumulation rates were greater for seedlings in flooded soil than for seedlings in well-drained soil. The concentration of Fe in the roots of seedlings in flooded soil was almost tenfold greater than that of seedlings in well-drained soil. However, flooding had no effect on foliar Fe concentrations. The flooding treatment resulted in decreased concentrations of N in all component parts and increased concentrations of P in the roots and stem, but it had no effect on foliar P concentrations. In response to flooding, foliar K concentrations decreased, whereas the concentration of K in the roots increased. Flooding had no effect on the K concentration of the stem. Seedlings in flooded soil produced more total biomass per milligram of nutrient absorbed than seedlings in well-drained soil, suggesting that N. aquatica seedlings are more efficient at producing biomass and height growth under hydric conditions than under mesic conditions.

Journal Article↗
PubMed2006

Farming with rocks and minerals: challenges and opportunities.

In many parts of the world food security is at risk. One of the biophysical root causes of falling per-capita food production is the declining quality and quantity of soils. To reverse this trend and increase soil fertility soil and plant nutrients have to be replenished. This review provides a literature survey of experiences of using multi-nutrient rock fertilizers for soil fertility enhancement from temperate and tropical environments. Advantages and limitations of the application of rock fertilizers are discussed. Examples are provided from two successful nutrient replenishment projects in Africa where locally available rock fertilizers are used on highly leached acid soils. The potential of combining organic materials alongside rock fertilizers in soil fertility replenishment strategies is stressed.

Agriculture↗
PubMedDate not supplied

Passive nighttime warming facility for forest ecosystem research.

A nighttime warming experiment is proposed. Over the last four decades a significant rise in nighttime minimum temperature has been determined from analysis of meteorological records from a global distribution of locations. The experiment involves nighttime deployment of infrared (IR) reflecting curtains around four sides of a forest canopy and across the top of the forest to mimic the top-down warming effect of cloud cover. The curtains are deployed with cable and pulley systems mounted on a tower and scaffolding structure built around the selected forest site. The trunk space is not enclosed except as an optional manipulation. The curtains reflect long-wave radiation emitted from the forest and ground back into the forest warming the trees, litter, and soil. Excellent infrared reflection can be obtained with commercially available fabrics that have aluminum foil bonded to one side. A canopy warming of 3 to 5 degrees C is expected on cloudless nights, and on cloudy nights, a warming of 1 to 3 degrees C is anticipated relative to a control plot. The curtains are withdrawn by computer control during the day and also at night during periods with precipitation or excessive wind. Examples of hypothesized ecosystem responses to nighttime warming include: (1) increase in tree maintenance respiration (decreasing carbon reserves and ultimately tree growth), (2) increase in the length of the growing season (increasing growth), (3) increase in soil respiration, (4) increase in litter decomposition, (5) increase in mineralization of N and other nutrients from soil organic matter, (6) increase in nutrient uptake (increasing growth), and (7) increase in N immobilization in litter. Hypothesis 1 has the opposite consequence for tree growth to Hypotheses 2 and 6, and thus opposite consequences for the feedback regulation that vegetation has on net greenhouse gas releases to the atmosphere. If Hypothesis 1 is dominant, warming could lead to more warming from the additional CO(2) emissions. Site-specific meteorological, ecophysiological, and phenological measurements are obtained in the warming treatment and in a carefully selected control plot to investigate site-specific hypotheses. Measurements made on both plots for a baseline period and during the period of curtain deployment provide data to test the hypotheses statistically by the "before-after-control-impact" method applicable to unreplicated experiments. The enclosure has a modular design that can be adapted and combined with other forest-scale manipulation experiments such as free air CO(2) enrichment and throughfall displacement.

Journal Article↗