chemical composition in nature
chemical composition in nature
chemical composition in nature
Chemical composition and nature of organic amendments :
a. Chemical Constituents :
The plants used for green manuring are high in water-soluble constituents, in nitrogen and other nutrient elements; but are comparatively low in cellulose and lignin. As a result, decomposition of a green manure crop ploughed into the soil sets in very rapidly. This is accompanied by rapid liberation of the nitrogen and other nutrient elements in available forms. Comparatively little humus is produced.
The plants grown for green manuring and ploughed into the soil could be divided into three categories:
* Those that contain balanced proportion of available carbohydrates to nitrogen.
* Those that contain excess nitrogen, or more than what is required for the decomposition of the carbohydrates.
* Those that contain excess carbohydrates and lignin over nitrogen.
The third group, comprising both legumes and non-legumes decomposes more slowly than the plants of the other two categories (Saber 1997).
Farmyard manure consists of three main components, bedding (soil materials, straw … etc.), solid excreta of the animals and liquid excreta or urine. The nature and relative concentration of these components vary greatly in different manures, depending on the type of animals, their feeding practices, nature and chemical composition of bedding. Since the various components of the manure also differ considerably in chemical composition, it is natural to expect that the decomposition of different manures should vary.
Sheep manure is high in protein, in cold-water-soluble organic materials and in ash, but is low in cellulose. Horse manure is low in protein and high in cellulose and hemicellulose. Cow manure is intermediate in its properties. Chicken and pigeon manures are highest in nitrogen, phosphorus and potassium as well as the most important nutrient elements required for plant growth. Cattle and horse manures contain comparatively lower quantities of these essential ingredients.
Sewage sludge constituents is the highest contributor to building up of soil organic matter in addition to its high contents of phosphorus and nitrogen, however certain polluting constituents.
Synthetic soil conditioners and petroleum by-products used for mulching are mainly long chains of hydrocarbons with varied structures – linkages and specific functioning groups. The produced by-products of decomposition are very significant in terms of impacts on formation of soil aggregates, soil water relations and generation of pollutants.
b. C/N Ratio :
The huge variations in C/N ratios of the organic amendments referred to is evident. Natural organic amendments have a range of 10-20 C/N ratio while other organic amendments of varied origins could reach a C/N ratios of 70. The application of amendments of high C/N ratios lead to consumption of the available soil N especially in the early stages of decomposition which could deprive the growing plants from N in its early growth stages. The adverse impact of C/N ratio is dependant on the rate of application and the initial N content of the soil among other factors.
c. Physical Nature of Amendments:
The bulkiness, natural state (solid, liquid slurry, emulsion inoculation …etc.) of the organic amendments will affect its handling, storage and proper method of application and mixing with the soil materials. These factors have impacts on the efficiency and function of the added amendments.
4.2. Decomposition Reactions, Chemical Conversions and By-Products :
The ease and rate of chemical decomposition, conversion of chemical constituents of the applied organic amendments will depend on the chemical composition, degradable components, interactions with the soil flora and fauna. Methods and rate of application, as well as, moisture status, aerobic conditions and soil temperature.
Nitrogen, phosphorus and to a lower rate potassium are among the main by-products of decomposition especially of natural amendments. The released nutrients are mainly in plant available forms which undergo other chemical conversions based on soil properties. Nitrogen could be released in the forms of ammonia (green manuring) which could be oxidized to nitrate or partially lost through voletilisation. The rate of release of N to the soil media would determine its availability to growing plants which might be accompanied by significant losses of N especially with application of N rich amendments (Poultry and Bird manures).
Available phosphorus forms are relatively soluble phosphates or organic phosphorus compounds that would enhance the availability and mobility of phosphate in arid soils traditionally poor in P supplying power. The released inorganic forms of phosphate gradually transform to more sparingly soluble phosphate compounds, through enrichment with Ca under alkaline soil reaction.
The availability of micronutrients including Fe, Mn, Zn, and Cu are exhanced through formation of metalo-organic chelated compounds that maintains the availability of these important nutrients under arid soil conditions which are usually diagnosed by deficiency of one or more of these micro nutrients, due to alkalinity of soil ph and presence of carbonate.
The released protein, carbohydrate, lipid organic acids and other compounds gradually form organo-clay complexes and humus compounds of varied stages of complexity. These compounds are highly beneficial for the amendment of most physical, chemical and biological properties. Other constituents released with possible hazardous impacts are heavy minerals and polluting intermediate by-products.
Application of organic of varied amendments to a certain crop usually have a residual effect for the crop/crops to follow. Such residual effect is a function of many factors including the ratio of degradable components, the rate of decomposition and chemical conversion of the soil, the formation of stable chelates and organo-clay compounds, impact of agronomic practices of the growing crops and interactions with cropping pattern followed. The later two factors will be dealt with in a following section.
Biofertilizer practices include the application of varied single or multi-strain beiofertilizers which have definite beneficial well-known impacts in supporting plant growth and enhancing the soil fertility status. Some of these micro-organisms fix atmospheric nitrogen in a free-living state i.e. non-symbiotic to baster, Azolla and others. Others form symbiotic association with higher plants (Rhizobium and mycrohizial strains). Other biofertilizer components include those of abilities to mobilize the unavailable forms of nutrient elements (phosphorus and micro nutrients) to available forms. Mechanisms by which these organisms accomplish their impact include secretion of certain organic acids which help solubilize immobile phosphate compounds and forming chelated micro nutrient compounds. Another mechanism is the chelating of excess Ca which gives preference to more soluble phosphate and micro nutrient compounds.
The degradation of petroleum by-products lead to the release of large amounts of sulphur and Zn in addition to other heavy metals including Cd, Pb, Ni and Cu. Under the alkaline soil Ph of arid lands it is expected that these heavy metals would be immobilized and its availability to growing plants is sharply reduced up to a certain level of soil loading. However, microbial degradation of petroleum by-products and the huge number of synthetic soil conditioners available on the market will lead to the release of large number of intermediate hydrocarbon products, of varied molecular composition, some of which are regarded as pollutants to the environment. The use of many of these long chain hydrocarbon for agricultural soil development were banned in its countries of origin. It is of significance to realize the type of by-products and fate of such long carbon polymers before application to the soils resources base.
chemical composition in nature
chemical composition in nature
a. Chemical Constituents :
The plants used for green manuring are high in water-soluble constituents, in nitrogen and other nutrient elements; but are comparatively low in cellulose and lignin. As a result, decomposition of a green manure crop ploughed into the soil sets in very rapidly. This is accompanied by rapid liberation of the nitrogen and other nutrient elements in available forms. Comparatively little humus is produced.
The plants grown for green manuring and ploughed into the soil could be divided into three categories:
* Those that contain balanced proportion of available carbohydrates to nitrogen.
* Those that contain excess nitrogen, or more than what is required for the decomposition of the carbohydrates.
* Those that contain excess carbohydrates and lignin over nitrogen.
The third group, comprising both legumes and non-legumes decomposes more slowly than the plants of the other two categories (Saber 1997).
Farmyard manure consists of three main components, bedding (soil materials, straw … etc.), solid excreta of the animals and liquid excreta or urine. The nature and relative concentration of these components vary greatly in different manures, depending on the type of animals, their feeding practices, nature and chemical composition of bedding. Since the various components of the manure also differ considerably in chemical composition, it is natural to expect that the decomposition of different manures should vary.
Sheep manure is high in protein, in cold-water-soluble organic materials and in ash, but is low in cellulose. Horse manure is low in protein and high in cellulose and hemicellulose. Cow manure is intermediate in its properties. Chicken and pigeon manures are highest in nitrogen, phosphorus and potassium as well as the most important nutrient elements required for plant growth. Cattle and horse manures contain comparatively lower quantities of these essential ingredients.
Sewage sludge constituents is the highest contributor to building up of soil organic matter in addition to its high contents of phosphorus and nitrogen, however certain polluting constituents.
Synthetic soil conditioners and petroleum by-products used for mulching are mainly long chains of hydrocarbons with varied structures – linkages and specific functioning groups. The produced by-products of decomposition are very significant in terms of impacts on formation of soil aggregates, soil water relations and generation of pollutants.
b. C/N Ratio :
The huge variations in C/N ratios of the organic amendments referred to is evident. Natural organic amendments have a range of 10-20 C/N ratio while other organic amendments of varied origins could reach a C/N ratios of 70. The application of amendments of high C/N ratios lead to consumption of the available soil N especially in the early stages of decomposition which could deprive the growing plants from N in its early growth stages. The adverse impact of C/N ratio is dependant on the rate of application and the initial N content of the soil among other factors.
c. Physical Nature of Amendments:
The bulkiness, natural state (solid, liquid slurry, emulsion inoculation …etc.) of the organic amendments will affect its handling, storage and proper method of application and mixing with the soil materials. These factors have impacts on the efficiency and function of the added amendments.
4.2. Decomposition Reactions, Chemical Conversions and By-Products :
The ease and rate of chemical decomposition, conversion of chemical constituents of the applied organic amendments will depend on the chemical composition, degradable components, interactions with the soil flora and fauna. Methods and rate of application, as well as, moisture status, aerobic conditions and soil temperature.
Nitrogen, phosphorus and to a lower rate potassium are among the main by-products of decomposition especially of natural amendments. The released nutrients are mainly in plant available forms which undergo other chemical conversions based on soil properties. Nitrogen could be released in the forms of ammonia (green manuring) which could be oxidized to nitrate or partially lost through voletilisation. The rate of release of N to the soil media would determine its availability to growing plants which might be accompanied by significant losses of N especially with application of N rich amendments (Poultry and Bird manures).
Available phosphorus forms are relatively soluble phosphates or organic phosphorus compounds that would enhance the availability and mobility of phosphate in arid soils traditionally poor in P supplying power. The released inorganic forms of phosphate gradually transform to more sparingly soluble phosphate compounds, through enrichment with Ca under alkaline soil reaction.
The availability of micronutrients including Fe, Mn, Zn, and Cu are exhanced through formation of metalo-organic chelated compounds that maintains the availability of these important nutrients under arid soil conditions which are usually diagnosed by deficiency of one or more of these micro nutrients, due to alkalinity of soil ph and presence of carbonate.
The released protein, carbohydrate, lipid organic acids and other compounds gradually form organo-clay complexes and humus compounds of varied stages of complexity. These compounds are highly beneficial for the amendment of most physical, chemical and biological properties. Other constituents released with possible hazardous impacts are heavy minerals and polluting intermediate by-products.
Application of organic of varied amendments to a certain crop usually have a residual effect for the crop/crops to follow. Such residual effect is a function of many factors including the ratio of degradable components, the rate of decomposition and chemical conversion of the soil, the formation of stable chelates and organo-clay compounds, impact of agronomic practices of the growing crops and interactions with cropping pattern followed. The later two factors will be dealt with in a following section.
Biofertilizer practices include the application of varied single or multi-strain beiofertilizers which have definite beneficial well-known impacts in supporting plant growth and enhancing the soil fertility status. Some of these micro-organisms fix atmospheric nitrogen in a free-living state i.e. non-symbiotic to baster, Azolla and others. Others form symbiotic association with higher plants (Rhizobium and mycrohizial strains). Other biofertilizer components include those of abilities to mobilize the unavailable forms of nutrient elements (phosphorus and micro nutrients) to available forms. Mechanisms by which these organisms accomplish their impact include secretion of certain organic acids which help solubilize immobile phosphate compounds and forming chelated micro nutrient compounds. Another mechanism is the chelating of excess Ca which gives preference to more soluble phosphate and micro nutrient compounds.
The degradation of petroleum by-products lead to the release of large amounts of sulphur and Zn in addition to other heavy metals including Cd, Pb, Ni and Cu. Under the alkaline soil Ph of arid lands it is expected that these heavy metals would be immobilized and its availability to growing plants is sharply reduced up to a certain level of soil loading. However, microbial degradation of petroleum by-products and the huge number of synthetic soil conditioners available on the market will lead to the release of large number of intermediate hydrocarbon products, of varied molecular composition, some of which are regarded as pollutants to the environment. The use of many of these long chain hydrocarbon for agricultural soil development were banned in its countries of origin. It is of significance to realize the type of by-products and fate of such long carbon polymers before application to the soils resources base.
chemical composition in nature
chemical composition in nature
chemical composition in nature
chemical composition in nature
chemical composition in nature