Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Reexamination Certificate
2000-08-21
2004-03-02
Gitomer, Ralph (Department: 1651)
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
C071S001000
Reexamination Certificate
active
06699709
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for determination of the gross nitrogen-mineralization rate of a soil sample. There is also provided a method for determining the amount of fertiliser to be applied to a soil and a test kit for readily determining a soil microbial enzyme activity present in a soil sample and correlating this activity with the corresponding gross nitrogen-mineralization rate of said sample.
More particularly, the invention provides for a novel and innovative method for determining the total release of plant available nitrogen (N) in soils. Soils contain nitrogen in both organic and inorganic forms. Both forms are potentially available for uptake by agricultural crops. However, organic forms must be converted to inorganic nitrogen before plant uptake.
The invention facilitates a determination of the rate at which organic nitrogen is converted to inorganic nitrogen or mineral nitrogen. This conversion is known as N-mineralization. The total release of plant available nitrogen in a soil, i.e. the gross N-mineralization rate quantifies the conversion in the soil of organic nitrogen to inorganic nitrogen.
The method of the invention can be used e.g. in a determination of the amount of a nitrogen-containing fertiliser to be applied to a soil such as e.g. a field of agricultural crops. Determination of the total release of plant available nitrogen in an agricultural soil is important when considering how much nitrogen-fertiliser to apply in order to obtain optimal growth conditions and at the same time minimising inorganic nitrogen-compounds such as nitrate from leaching out of the soil into ground or surface waters.
BACKGROUND OF THE INVENTION
Nitrogen is present in the soil in both organic and inorganic forms. Nitrogen present in what is generally referred to as “soil organic matter” (SOM) such as macromolecular proteinaceous substances, humus, lignine, pectine, and the like, cannot readily be taken up be growing plants including agricultural crops. Nitrogen must be present in inorganic forms such as e.g. nitrate, ammonia in order to be taken up via the roots of the crops. The amount of inorganic nitrogen in the soil is generally much less than the requirement of the crops for nitrogen. It is therefore necessary to supplement nitrogen in the form of a suitable fertiliser.
An optimal fertiliser application shall facilitate optimal plant growth as well as minimal nitrogen leaching. Determination of the total release of plant available nitrogen in a soil is thus essential, when considering just how much nitrogen-fertiliser to apply, in order to achieve optimal growth conditions as well as preventing inorganic nitrogen-compounds such as nitrate from leaching out of the soil. Without any knowledge of the soils inherent capacity to release nitrogen to the crops, the farmer cannot accurately determine the amount of nitrogen-fertiliser to apply.
The conversion of organic nitrogen to nitrogen present in inorganic forms such as nitrate and ammonia is a dynamic and complex process, which cannot easily be accounted for. The process is influenced by e.g. climate, soil texture, total nitrogen, soil management, and the presence of soil microorganisms capable of degrading organic macromolecules and releasing e.g. nitrate and/or ammonia into the soil, and by the amount of nitrogen taken up by crops.
No simple method is available for measuring the gross N-mineralization rate. Thus, it has hitherto not been possible to account for nitrogen mineralization in fertiliser planning. Various methods for measuring directly or indirectly the amount and/or presence of organic and/or inorganic nitrogen-containing compounds in soil have been described in the prior art and briefly reviewed below.
Burton and McGill (1992) reported on changes in various components of a so called N-mineralization cascade. The changes studied included those of a specific component, such as a deaminase, as well as highly integrated components, such as a biomass. The selected soil was a Black Chernozemic seeded to barly (
Hordeum vulgare L
.) under field conditions. Changes in enzyme contents were related to soil ammonium in order to determine, if the microbial environment changed sufficiently to exert feedback control on N-mineralizing reactions, which would allow them to be detected. Histidase and protease were chosen as model systems for depolymerization and deamination, respectively, because information was already available on their control in pure culture studies, on histidine content and control of histidase in soil, and because assay procedures were readily available for soils. A correlation of an enzyme activity with gross N mineralization rates of a soil and problems associated with excessive use of fertilisers were not disclosed therein.
Burton and McGill (1989) characterised the stability of L-histidine NH
3
-lyase in soil by using a kinetic analysis and enzymatic assays in the presence of a biostatic agent. The objective was to employ a range of assay durations together with a kinetic analysis in order to examine the components of L-histidine NH
3
-lyase activity in soil, the stability of such components and the implications for the control of this enzyme. A correlation of an enzyme activity with gross N mineralization rates of a soil and problems associated with excessive use of fertilisers were not disclosed therein.
Galstyan and Vartanyan (Chem. Abstracts (1980), vol. 92, p. 494, 92:93207k) describe a method for determining an enzyme activity, i.e. arginase activity in soil samples by titration of ammonium ions. The results demonstrate a correlation of the content of humus with microbial activities, but do not evaluate or consider evaluating a correlation of an enzyme activity with gross N-mineralization rates of a soil.
SU-657344 relates e.g. to a calorimetric determination of inorganic nitrate and nitrate reducing enzymes in soil. The method is useful in evaluating nitrogen fixing soil bacterial activities. A correlation of an enzyme activity with gross N-mineralization rates of a soil and problems associated with excessive use of fertilisers were not disclosed.
SU-711470 relates to a determination of plant available nitrogen in a soil sample in order to evaluate a potential fertiliser requirement. A correlation of an enzyme activity with gross N-mineralization rates of a soil and problems associated with excessive use of fertilisers were not disclosed. Derwent Abstract WPI 96-391776 discloses a simple incubation method for determining the net mineralization potential of a soil. No enzymes are mentioned and consequently, a correlation of an enzyme activity with gross N-mineralization rates of a soil and problems associated with excessive use of fertilisers were not disclosed.
Derwent Abstract WPI 93-248897 discloses a method for calculating the net mineralization potential of a soil. A correlation of an enzyme activity with gross N-mineralization rates of a soil and problems associated with excessive use of fertilisers were not disclosed.
Cole (TIBTECH (1993), vol. 11, p. 368-372) describes the need to control environmental nitrogen in various ecosystems by means of exploiting microbial metabolisms, but no solution to the problem of how to reduce the excessive use of fertilisers is presented.
Benchemsi-Bekkari and Pizelle (Black locust nitrogen nutrition. Urea metabolism, relation with arginase and urease activities, Ph.D. thesis, (1993), Pascal no. 94-0041061) describe an acacia tree capable of assimilating nitrogen. Metabolism relating to the urea cycle is disclosed and a ratio of arginase activity to urease activity is determined. A correlation of arginase activity with gross N-mineralization rates of a soil and problems associated with excessive use of fertilisers are not disclosed.
Biosis Acc. No. 37066711 relates to a study of the effect of nitrogen-fertilisers on soil enzymes involved in nitrogen uptake and nitrogen metabolism in soil bacteria. A correlation of an enzyme activity with gross N-mineralization rates of a soil is not disclosed.
It is desirable to be able to
Bonde Torben A.
Miller Morten
Sørensen Jan
Bonde Torben A.
Cooper Iver P.
Gitomer Ralph
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