I need N balance calculation with one example if possible please provide the same
Nitrogen balance is measured by deducting N outputs and changes in soil total N storage from N inputs as follows:
Nitrogen balance = N inputs − N outputs − changes in soil total N
Where N inputs = N fertilization from inorganic N fertilizers + N fertilization from manures and amendments + atmospheric N depositions (rain, snow, and dry deposition) + biological N fixation (symbiotic + non-symbiotic N fixation) + irrigation water + crop seed.
N outputs = crop N removal (grain and biomass) + N losses (through N leaching, NH4 volatilization, denitrification, gas emissions [NOx], surface runoff, soil erosion, and plant senescence)
Changes in soil total N = Soil total N at the end of the experiment − soil total N at the beginning of the experiment.
A positive value of N balance indicates that N is gained in the system and negative value indicates loss. When all sources, sinks, and losses of N are accounted, there should be no net gain or loss of N if N is recycled efficiently. This, however, occurs rarely due to various factors, such as variations in soil and climatic conditions, N management, soil and crop management practices, and difficulty in measurement of some parameters, such as atmospheric N depositions, biological N fixation, and N losses through various processes.
The information provided by J C TARAFDAR AND A K SRIVASTAVA is really very comprehensive .
A nitrogen balance calculates the balance between nitrogen added to an agricultural system and nitrogen removed from the system per hectare of agricultural land. Ideally the balance result should be related to the area of agricultural land which is potentially fertilised, to avoid a bias in the result for countries with large extensive and not utilised areas. A deficit over a number of years indicates that the farming system, in particular the soil, is losing its fertility, while a large surplus of N suggests a risk of pollution of soil, water and air, though this may depend also on other factors, such as agricultural practices, weather conditions and soil type. In many countries, nitrogen surpluses per hectare of agricultural land can be highly variable, with some sub-national regions severely affected by the problem of “excessive” nitrogen and others not. National balances are, in this sense, much less powerful indicators than regional level balances (see Section 5). Among the methods to calculate the nitrogen balance, two types are in general use: • The Farm-gate balance (Farm balance or sector balance) treats the farm (or national agricultural industry) as an entity. Nitrogen recycled within the entity is ignored. This type of balance takes into account the amount of nitrogen imported into the farm or national agricultural industry (i.e. in fertilisers, feedstuffs, etc.) and exported from the farm or the national agricultural industry, i.e. in animal products (e.g. milk, eggs, meat) and crops, excluding fodder crops and grass which are consumed on the farm. The difference between imports and exports is the nitrogen surplus or deficit. This type of balance is very suitable for use at individual farm level and at national level2 . • The Gross balance also treats the farm as the unit to be observed, but attempts to calculate all inputs and outputs from this unit, i.e. the amount of nitrogen used by the farm (e.g. fertilisers, animal manure), through atmospheric deposition, fixed in the soil through biological process, and removed from the soil (in crops and through grazing). In practice the soil includes un-harvested plant material, but not the livestock moving over the land. Thus grass harvested or grazed which is recycled internally within a farm-gate balance, must be explicitly accounted for as nitrogen removed by cutting or grazing and re-deposited as manure. Amount of N removed in harvested crop of category(i) [kg N] = crop production of category(i) [tonnes of fresh-matter ] X N coefficient for category(i) [kg N/tonne of fresh-matter]
We provide a simple framework how to calculate a N balance for the single crops and the cropping system (rotation) in our article: Article A cropping system assessment framework—Evaluating effects of...
and this concept was applied to five case studies hereArticle Trade-Offs between Economic and Environmental Impacts of Int...
All the explanations are very much helpful. Thanks everybody to clarify the problem clearly.
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