Soil science part 2

Nitrogenase (monera)

The enzyme involved in the biological dinitrogen cycle. This enzyme lowers the active energy (needed to cause the reaction to occur). The fixation progresses in reduction stages from dinitrogen (N=N) through intermediates (HN= NH and H2H-NH2 to produce 2NH3 that is transformed (NH3) into organic compounds such as amino acids.

Electrical conductivity measured in?

The flow of a current through a soil extract, measured in Siemens per meter or some variation thereof. This method typically determines salinity. At low salt concentrations EC is directly proportional to salt content.

Aerobic (bacteria)

require free gaseous oxygen source; includes most active decomposers; most populous bacteria.

Immobilization

The incorporation of NH4 + NO3 into the bodies of plants or microbes.

Leaching fraction

The leaching fraction can be defined as the ratio of electrical conductivity of applied water to that of drainage water. When the amount of water to wet the soil is calculated, the leaching fraction indicates the addition water that must be added for leaching.

How fertilizers can improve the enivornment

The more trees, grass, crops we grow the more CO2 can be removed from the atmosphere. More plant cover = less erosion. More crop production in stable landscapes = less crop production in fragile landscapes.

Legume (monera)

The most important symbiotic relations involve bacteria and plants from the legume family. Legumes (pod bearing plants such as peas, beans, alfalfa, and clovers) have beneficial effect on both the companion crop and whatever crop is planted next in the same soil.

Detritus

debris from decomposing rock and from dead plants and animals (like dirt)

Heterotrophic (bacteria)

derive their food (reduced carbon) and energy directly from organic substances. Fungi, protozoa, animals, and most bacteria are heterotrophs. Include both N fixing and non N fixing groups. Heterotrophic bacteria that do not fix N are the most prevalent in soil and account for much decomposition of organic materials.

Saline seeps

develop on several kinds of layered substrate, but all have water moving in a downslope direction within the soil (recharge area), usually above a low permeability geologic layer and probably dissolving more salts as it flows. The water eventually seeps to a soil surface at some low elevation (seep area), where it is evaporated or transpired, leaving salt accumulations.

Salt balance

exist when outgoing salt is equal to incoming salt

Virus

has a protective protein coat around its RNA or DNA; sometimes even a lipid containing envelope surrounds the nucleic acid.

Symbiotic bacteria

heterotrophic bacteria that fix atmospheric dinitrogen in plant root nodules have a mutually helpful relationship with their host. They include legumes, nitrogenase, and rhizobium.

Commensalism

in biology, a relationship between individuals of two species in which one species obtains food or other benefits from the other without either harming or benefiting the latter.

Symbiosis

interaction between two different organisms living in close physical association, typically to the advantage of both.

Saline soils

is a soil with enough salt at some position within the root zone to interfere with plant growth. SAR < 13. 23% of cultivated soils are saline

Allelopathy

is any beneficial or harmful effect of the chemicals produced by one plant on another plant.

Animalia

is one of the five generally accepted kingdoms of living organisms. Includes worms, nematodes, arthropods, mollusks, jellyfish, coral, vertebrate animals, insects, etc. They are multicellular organisms, Heterotrophs (animals ingest food), and undergo sexual or asexual reproduction.

Compost

is the microbial decomposition of piled organic materials into partially decomposed residues. The process is best done aerobically. To destroy pathogens exact temperatures for determined lengths of times must be reached inside the compositing mixtures, such as about 71 C (160F) for an hour or more.

Humin

is the portion of humus that is insoluble in dilute sodium hydroxide.

Exchangeable sodium percentage (ESP)

is the portion of total exchangeable cations (in units of centimoles of charge per Kilogram) that are sodium. ESP = Exchangeable Na / Total Exchangeable cations (100%). The value is used extensively to indicate the hazard of sodium induced soil dispersion, which can severely reduce soil hydraulic conductivity. An ESP value equal to or greater than 15 indicates a sodic soil.

Prion

various nucleic acids without a protective coat. They store genetic material, but cannot carry out physiological functions of their own (they replicate acellular within living cells).

Managing crops in salt affected soils

1) Maintain Fc during early growth (this dilutes salts and lessens their toxicity), 2) prevent crusting of soil to reduce emergence damage irrigate often but in smaller amounts, 3) Use organic mulches to slow evaporation, 4) Ridge till and plant on ridge sides, 5) use tolerant crops- few some varieties of grains and cotton, and halophytes, 6) Deep plowing can bury salinized salts.

Mineral "apatite" (rock phosphate) Ca5(PO4)3

A natural, calcium phosphate form. Rock phosphate and other phosphates of Fe, Mn, and Z make up the inorganic phosphate minerals.

Arthropods (animalia)

joint footed invertebrate organisms. Ex: Mites, spiders, scorpions, millipedes, centipedes, etc. They feed on mostly decaying vegetation and help aerate the soil.

Sodic

A sodic soil is not caused by an overabundance of total salts, but rather by a salt imbalance in which sodium (Na) is the dominant cation rather than calcium (Ca), which dominates in most soils. SAR > or = 13 and pH > 8.5. 39% of cultivated soils are sodic.

Saturated paste

A soil sample of perhaps 100g to 500g would be completely saturated with water. Once saturation is achieved, no more water is added. After an equilibration period of several hours, water is removed from the saturated sample by vacuum filtration, and the salt content of the saturated paste extract is measured. This is the standard method for measuring soil salinity in the laboratory.

Polysaccharides

Another instance of organic substances comprising soil organic matter. They are chains of sugar molecules that help to cement soil aggregates together.

Fulvic and Humic Acid

Are soluble in dilute sodium hydroxide solutions, but humic acid is larger and will precipitate out (be insoluble) when the solution is made acidic.

Gastropods (animalia)

Belly footed organisms; feed on decaying vegetation, but will eat and damage living plants. Ex: Slugs and snails.

Anaerobic (bacteria)

Can use electron acceptors other than O2 such as NO3- or SO4^2-; do not require free oxygen.

Humus

Colloidal, amorphous, dark brown materials; substances left after breakdown of fresh plant and animal residues and microbial biomass.

Soil Magnesium

Commonly supplied by soil minerals, Mg deficiency is corrected by adding lime (dolomite) to acidic soil. Other common fertilizers: potassium magnesium sulfate, magnesium sulfate (epsom salt). Plants use MG in Chlorophyll molecules and activation of enzymes. "Grass tetany" disease of domestic animals caused by low MG in blood.

Thermophiles

Composting microbes tolerate relatively high temperatures: 55 C to 65 C (131 F to 149 F)

Soil sulfur

Constituent in 2 of 20 amino acid. Found in several vitamins and plant oils. In protein sulfur is 1/10 the content of N. Availability of S for plants is hard to predict due to major portions come fro SOM which depends microbial activity which is dependent on climate. Soils contain many sources of S: Pyrite is common, gypsum is found in many arid soil, as are sodium sulfate. Rainfall dissolves sulfur oxides from burning fossil fuels. Deficiens are not common since many fertilizers constina sulfur.

Mineralization

Conversion of organic nitrogen to ammonium form. Release of amino groups during decomposition of organic material. Major source of nitrogen in no fertilized soil.

Controlled N release fertilizers

Crops recovery of N is 40-70%, slow release N fertilizers are used to increase the % used by plants. Financial savings and less pollution (N leached). Commonly used in turf mgmt, EX- formaldehyde UF, sulfur coated urea (SCU), polymer coated N, organic products

Reclaiming salinized soils

Deep plow via deep chisel plowing, internal drainage, irrigation, and organic mulching (cover cropping)

Fertility Management overview

Efficient land managers may spend < 20 % of production costs on fertilizer for yield increases up to 50%. Fertilizers may not be profitable when: water is the most limiting factor, other issues arise, pest, acidity, extreme cold. And increased yield has less market value. Compared to other production problems, fertility is relatively easy to solve. Many crop disease are linked to poor fertility.

Reclaming salty soils

Establish internal drainage, replace excess sodium if need, leach out soluble salts.

Phosphorus problem

Getting P into a plant is a widespread problem as soil forms of P are very slow solubility and phosphates applied as fertilizers readily combine with cations in the soil to form low solubility substances. Making it available to plants it critical as it is low in most soils and are not readily available for plants. (total P in soil is 0.05% by weight). Only 10-30% of P added is used by crops during the same season, retained excess P can cause Zn deficiency.

pH

In acidic areas of higher rainfall, pH of 4.5-5.5 is common. Toxic levels of Al and Mn increase as pH decreases. Most soils with pH less than 5 respond to lime applications. The more clay and OM, the more lime is needed to change pH as soil colloids contain large quantities of exchangeable Al and H ions due to high CEC, the Higher the CEC the more lime is needed.

Plants tolerant to acidity

Include tea, pineapples, blueberries, coffee, and azalea. They can do this because of immobilization in the cell wall, selective permeability to Al at the cellular membrane, a plant induce pH barrier in the rhizosphere, and compartmentation of Al in the vacuole.

Activation energy

Is an energy barrier to decomposition and must be overcome before decomposition can occur. Enzymes lower this activation energy between chemical bonds, allowing for this biological process to occur in nature.

Ammonium sulfate NH4SO4

Manufactured from recovered coke oven gases. Contains 21% N high cost so less popular. Most strongly acid forming.

Soil sampling guidelines

Many laboratories request samples from the top 30cm (root zone) for no till fields and sod crops, this depth may be shallows. Cost and time usually determine the number of samples taken. Tests should be done every year on new crop land; once crops needs and soil attributes are known, once every 2-3 years.

Mycorrhizae (fungi)

Meaning "fungus root", are symbiotic associations between fungi and plant roots. The plant roots transmit energy rich organic substances to the fungi, and the fungi aid in transmitting nutrients and water to the plant roots. The fungal Hyphae extend the plant's root 100-fold. They reach additional water and less mobile nutrients. They provide a protective cover which increases plants resistance to drought.

Psychrophiles

Microbes able to tolerate cold temperatures; 15 C to 20 C (59 F to 68 F).

Lime

More than 90% of agricultural lime is impure.

Common liming material

Most common liming materials include: Calcic limestone (CaCO3), Dolomitic limestone (CaMg(CO3)2), Lime from bottom of small freshwater ponds, soft limestone in ocean bottoms, furnace slag, ground oyster shells, and wood ashes.

Mesophiles

Most soil bacteria and actinomycetes, however, have optimum activity temperatures like those of the mesophiles (middle group) 25 C to 37 C (77 F to 99 F).

Soluble salts

Most soluble salts in soils are composed of the cations sodium, calcium, and magnesium, and the ions chloride, sulfate, and bicarbonate. Sourced from naturally occurring minerals (parent material) which causes irrigation water containing salts (fertilizer,minerals) 3 tons salt / acre.

Diffusion

Movement down a concentration gradient from a region of high concentration to a region of low concentration. Regions of low concentration is region of plant root caused by active uptake of less soluble and less abundant nutrients (K,P)

Mass flow

Movement of dissolved plant nutrients in water flowing toward the root. Most important mechanisms for soluble and abundant elements (N, Ca, Mg, S)

N2 fixation nonsymbiotic

N2 fixation by free living microorganisms, then release it for plant use when they die and are decomposed.

How to develop a fertility management program

Need to know 1) the plant fertility needs, 2) the fertility status of the soil. Standard method: soil sampling followed by soil analysis.

Growing plants can cause major pollution

Nitrates, phosphates, pesticides. Nitrates percolate through soil to groundwater. Once rare, nitrate pollution of wells is common near heavily fertilized fields and feedlots and dairies. Phosphates pollute surface water.

Anhydrous ammonia (NH3)

Principle N fertilizer more than 90% of all N fertilizers consist of ammonia or ammonia compounds. Ammonia is a colorless gas (physical properties like propane or butane), it is 82% N. Anhydrous ammonia is made from atmospheric N using natural gas to supply the hydrogen. It is the least expensive fertilizer as it requires less processing.

Carbon:nitrogen

Nitrogen most often controls the rate of organic matter decomposition; it is needed to build proteins in new bacterial and fungal populations. The nitrogen content in the microorganisms and in organic material is given through this ration. A wide organic carbon total nitrogen ratio indicates a material relatively low in nitrogen content. Bacteria require 1g N for each 5‐6g C (5:1). Process of decay can be hastened with more N. Plants growing in a high C:N environment are deficient in N because the soil microorganisms are able to use the N before the p.

Root interception

Occurs as roots explore new soil that contain untapped supplies of nutrients.

Soil Calcium

Occurs in soils in many minerals. Is more plentiful than other plant nutrients (feldspar, limestone, and gypsum are all sources). Ca deficiency is rare, but can be found in acidic leached soils in which lime has been added. It needs to be added to soil less media. Plants need Ca for cell division (buds, new growth) & function of cell membranes.

Mycelia

One of the first visual signs of decomposition is the appearance of mycelia, a mass of threadlike branching filaments (Hyphae). They also hold soil aggregates together.

Nitrification

Oxidation of ammonium to nitrate by microorganism. Most small amounts of NH4 (ammonium) is nitrified in 1-2 days (rapidly) unless soil is strongly acidic, waterlogged, or cold. large amounts of nitrites seldom accumulate which is good due to their toxic nature.

Plantae-plants

Produce carbon foods using CO2 and energy from the sun. Plant roots exude (secrete) many substances including: 18 amino acids, 10 sugars, 10 organic acids, various proteins, microbe attractants and repellents.

Dihydrogen phosphate (H2PO4)

Rapidly reacts in the soil to form insoluble phosphate. No efficient mechanism in the soil retains it in large qualities. Thus it is believed most P retained by plants comes from organic phosphate of decomposition.

Ammonium nitrate NH4NO3

Relatively cheap; 33 N, half in ammonium for and half in nitrate. Is explosive mixed with diesel.

Rhizobium (monera)

Rhizobia are bacteria that fix nitrogen (diazotrophs) after becoming established inside root nodules of legumes (Fabaceae). They are the most well known symbiotic bacteria.

Halophyte

Salt loving plants

Soil phosphorus is essential in?

Second most prescribed and limiting plant nutrient. It is essential in nucleoproteins. P has roles in cell division, stimulation of early root growth, hastening plant maturity, energy transformation within the cell, and fruiting and seed production.

Crops and lime

Strongly acidic soils restrict growth of plants. The addition of lime raises the soil pH and eliminated two problems: excess toxic Al3 and slow microbial activity. The adsorbed acidic Al are replaced with Ca from the lime.

Urea CO(NH2)2

Synthetic organic fertilizer. Cheaper per pound of N than another Solid N; 45% N. Is not absorbed by plants until the N is converted by urease enzyme to ammonium.

Leaching requirements

The amount of extra water added to leach the soil. It is the minimum leaching fraction that the crop can tolerate without yield reduction. A salt balance is required such as salt added = salt removed.

Rhizosphere (Plantae)

The area in the soils near the root. This portion of soil may be quite different in chemical properties from the bulk of the soils. It may be one to two pH units more acidic than the bulk soil.

Manure

The most pragmatic means of disposing of manure is by adding it to soil, where its nutritive value can be recycled by growing plants. Cattle manure average 3 5 N, 0.8 % P, 2 % K, 25 % organic carbon, plus varying amounts of other elements essential for plant growth. Due to water content, barn yard manure has a low fertilizer grade. Micronutrient content is higher in manures than chemical fertilizer, though manures supply low quantities of plant nutrients per dry weight. This could be said due to the nutrients the animals are fed. Manures have high soluble salt content and provide a means to spreading weeds as they survive the journey through gestation.

Nitrogen Cycle

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among the atmosphere, terrestrial, and marine ecosystems. Be able to draw this!

Phosphorus cycle

The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.

Soil potassium

The total amount of K found in most soils is sufficient to last several decades, yet the low solubility of micas and feldspar supplies only small amounts of K. Decomposition of fresh residue releases K+. K affects cell division, formation of carbohydrates, translocation of sugars, enzyme actions, resistance of some plants to disease. (Potash) Potash reserves are large,especially in Canada (Us imports 90%)

Protista

They are single celled (Unicellular) organisms (algae, protozoa, slime, molds), They improve soil aggregation and are important decomposers.

Fungi

They lack the ability to use sunlight, they live on dead or living animal or plant tissue (decomposers). They include unicellular yeasts, filament molds, mildews, smuts, rusts, and mushrooms. 1g of soil may contain 10^6 fungi cells. They require O2, but can tolerate acidic conditions. In well aerated soil, fungi usually comprise most of the biomass. They readily attack cellulose (woody material, lignins, gums. Compete with crops for nutrients N, P, K.

Reclaiming sodic and saline sodic soils

This is not the same as salinized (replace Na with Ca by applying gypsum), irrigation work work as the soil is clogged, deep plowing may work can bury salinized salts. Sodic soils with montmorillonite clays are nearly impervious to water because of pore clogging from deflocculation. While gypsum is the standard to reclaim solid soils, sulfuric acid 57% efficient, sulfur 18%, Lime 75%, iron sulfate 162%.

Monera (bacteria)

Unicellular microorganisms, number in soils usually exceeds that of all other microorganisms, although fungi may exceed bacteria in weight. 1g of soil may contain 100M bacteria and may include 1M species. (Include Autotrophic, heterotrophic, symbiotic, N2 fixing, and bacterial diseases).

Sodium absorption ratio (SAR)

Used to determine the Na content or potential sodium content of the soil with years of irrigation containing Na. When a soil SAR is 13 equals it will have poor permeability (Equivalent to 15% ESP).

Total Neutralizing power or CaCO3 equivalent

Used to express the relative chemical value of lime. If a lime is chemically pure calcium carbonate (calcite), the calcium carbonate equivalent is 100. If all the lime is in the calcium carbonate form, but it is only 85% pure, the CCE is 85. Refer to calculations 8-1 pg. 235. Limestone is seldom pure, it formed in ocean bottoms with silt and clay sediments.

Flocculation and dispersion in soils

When soils particle are disperse, aggregates do not form, and each particle behaves as an individual. Without aggregation, water, air, and root movement is greatly restricted (dispersion is not desirable). The type of cations determine whether the soil is dispersed or flocculated. Soil particles can be unattached to one another (dispersed) or clumped together (flocculated) in aggregates. Soil aggregates are cemented clusters of sand, silt, and clay particles. In dispersion soils Na is the main cation, and two replace every Ca. This causes waterlogging.

Protozoans (Protista)

a unicellular organism without a cell wall. They help control microbes, but can cause serious diseases. They ingest bacteria, fungi, and other microbes, nematode larvae and eggs which hasten recycling of plant nutrients.

Sludge

also called biosolids, are the solids settled out in sewage treatment plants and are much like livestock manures. They are well adapted for applications to turf grasses on gold courses, cemeteries and around public buildings.

Cyanobacteria (bacteria) held in check by?

also known as Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis, and are the only photosynthetic prokaryotes able to produce oxygen. The name "cyanobacteria" comes from the color of the bacteria (blue green algae). They can fix nitrogen and can be found from the Antarctic to Death Valley, their population is often held in check by shortages of phosphate.

Saline-Sodic

are high in salinity and high in the proportion of sodium salts relative to calcium and magnesium. SAR > or = 13

Nematodes: 3 types(animalia)

are microscopic (less than 2 mm), unsegmented, threadlike worms; they are classified according to their different feeding habits. They require moisture, not as feeding habits, but for prey. Up to 40% of soil N can be released from them. 1) Omnivorous nematodes- nematodes who live mainly on decaying organic matter and are the most common of the soils nematodes 2) Predaceous nematodes- prey on soils bacteria, fungi, algae, and even on other nematodes. 3) Parasitic nematodes- infest plant roots, causing the conspicuous knots that give visible proof of their presence. Their presence can be found in numerous vegetables and allow for pathogens which may cause more extensive damage. Sugar beets, soybean, and corn are particularly susceptible.

Actinomycetes (Bacteria)

are the source of numerous beneficial antibiotics and are important decomposers. They are filaments that resemble fungi, but are smaller and smell of freshly mown grass / hay, freshly plowed soil, or musty cellars. They include pathogens that cause strep throat, leprosy, tuber, and potato scab. No nucleus, they are prokaryotes.

Mutualism

association between organisms of two different species in which each benefits

N2 fixation symbiotic

bacteria or actinomycetes cause the formation of root nodules where they fix N2. Rates vary; usually lower when N fertilizers have been added.

Facultative Anaerobe

can be either aerobic or anaerobic in presence or absence of O2.

Autotrophic (bacteria)

manufacture their food by the synthesis of inorganic materials, such as plants do in photosynthesis. They obtain carbon from CO2. Probably the most important autotrophic soil bacteria are those that can oxidize NH4 to nitrite (NO2) than to nitrate (NO3). They grow fastest with abundant nitrogen, aeration, moist nonacidic soil, and 68-104 temp.

Algae (protista)

microscopic organisms that perform photosynthesis. Green algae are the most abundant in temperate climate soils or acidic soils. These algae can exist as single cells, form colonies, or form long filaments of cells. Less abundant are yellow algae which exist as single cells or form filaments. Yellow green algae are chromista, while blue green algae are cyanobacteria in the Monera kingdom. They inhibit bodies of water and are not abundant in subsoils. Some algae form mutualist associations with fungi, resulting in lichens.

Viroid

no protective coat around RNA

Acidic soils

occur primarily in the high rainfall regions of the world where basic cations (Ca, Mg, Na, and K) are leached out a replaced by H and Al. Lime is added to acidic soils to raise pH (reduce acidity), thereby increasing soil fertility, microbial activity, and crop production.

Salinity (salts)

occurs in low rainfall regions, in soils formed from saline parent material, in locations where poor irrigation practices have polluted the soils with salts, and in regions where salty groundwater has risen dangerously close to the surface due to land clearing or irrigation. Managing soil salinity is more problematic than soil acidity due to a lack of simple soil remedies.

Organic waste

plant and animal residues/manures, sewage sludge, composts, food processing wastes. Slow release. Nutrients are low (1-8% N, 0.2-2% P, 0.5-3% K)

Parasitism

relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism