In summary, it can be said that nitrogen is a critical
commodity, essential to the growth and development of
all plants. In order to synthesize the protein and other
nitrogenous compounds essential to growth, the nitrogen
must be in a reduced form (ammonia). Plants can absorb
nitrogen from the soil as nitrate as well as ammonia but
in this case it must be reduced by the plant in order to be
assimilated. This nitrate reduction requires energy or reducing
power and carbohydrate skeletons to form the
various amino acids. Therefore, the process is strongly
dependent upon photosynthesis. Various metabolic transformations
make nitrogen a mobile element in the plant.
The ultimate source of nitrogen to any living organism
is atmospheric denitrogen Since N2 cannot be utilized by
higher plants it must be converted to forms which can be
absorbed and assimilated. These forms are primarily nitrate
and ammonia. The necessary conversions are accomplished
by specific soil microbes as discussed.
The balance of the different forms of nitrogen in the
soil then is the result of the physiological status and activity
of all the living organisms found in a defined agricultural
system plus any supplemental applications and minus any
nitrogen removed by cropping_ Nitrogen is a natural resource,
in a sense a renewable natural resource, and the
productivity of our land is dependent on our understanding
the processes by which it undergoes various transformations
and our willingness to safeguard the balance of these
processes, inputs and exports.
In summary, it can be said that nitrogen is a criticalcommodity, essential to the growth and development ofall plants. In order to synthesize the protein and othernitrogenous compounds essential to growth, the nitrogenmust be in a reduced form (ammonia). Plants can absorbnitrogen from the soil as nitrate as well as ammonia butin this case it must be reduced by the plant in order to beassimilated. This nitrate reduction requires energy or reducingpower and carbohydrate skeletons to form thevarious amino acids. Therefore, the process is stronglydependent upon photosynthesis. Various metabolic transformationsmake nitrogen a mobile element in the plant.The ultimate source of nitrogen to any living organismis atmospheric denitrogen Since N2 cannot be utilized byhigher plants it must be converted to forms which can beabsorbed and assimilated. These forms are primarily nitrateand ammonia. The necessary conversions are accomplishedby specific soil microbes as discussed.The balance of the different forms of nitrogen in thesoil then is the result of the physiological status and activityof all the living organisms found in a defined agriculturalsystem plus any supplemental applications and minus anynitrogen removed by cropping_ Nitrogen is a natural resource,in a sense a renewable natural resource, and theproductivity of our land is dependent on our understandingthe processes by which it undergoes various transformationsและเรายินดีที่จะรักษาดุลของประมวล ผล ปัจจัยการผลิต และส่งออก
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