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The Nutrient Budget

The main reports produced by Overseer are nutrient budgets. A nutrient budget is a summary of annual nutrient inputs and outputs, and the various movements of nutrients through the farm or block during the year.

Overseer produces budgets for seven different farm nutrients - at both whole farm and management block scales.

A budget is broken down into three sections

  1. nutrients added (kg nutrient/ha/yr)
  2. nutrients removed (kg nutrient/ha/yr)
  3. change in soil and plant nutrients pools (kg nutrient/ha/yr).

Definition of terms in the nutrient budget

A nutrient budget is a tabulation of annual inputs and outputs of nutrients for blocks and the farm, assuming that management is constant. Internal transfers (changes in long-term storage pools due to changes in soil organic matter, weathering, adsorption, etc.) are considered as outputs.

The nutrient budget report uses shortened terms to describe the nutrient source or destination. Click on the terms below for their definition.

Nutrients added

Nutrients added as fertiliser, lime, piggery or imported dairy effluents, organic materials (e.g., compost), and foliar spray for fruit crops. This item also includes the nitrogen (N) added as DCD.
Nutrients in rainfall, and from biological N fixation.
Nutrients added in irrigation water.
Nutrients in supplements brought on to the farm or stored supplements, in animal health supplements or net imports of nutrients into a house block (to balance those removed as sewage loading) (farm nutrient budget only).
Nutrients imported onto the block: in supplements brought in or in stored supplements, in supplements or crops grown on-farm and fed to animals on blocks (Interblock supplement/crop transfer), and in animal health supplements (block nutrient budget only).
Nutrients in solid and liquid effluent applications arising from the farm dairy and wintering pads/animal shelters (block nutrient budget only).
Net input into a house block (block nutrient budget only).


Nutrients removed

Nutrients in products sold such as milk, wool, velvet, live weight, or crops.

For blocks, the product removal is distributed between blocks based on the intake that occurs for each block. The sum of product removal from blocks may be less than farm product removal if wintering pads/animal shelters are used.
Nutrients in effluent exported from the farm (farm nutrient budget only).

Farm: Supplements sold from the farm, exported crop residues, crop defoliation products, and fruit tree prunings.

Block: Supplements, fodder crops and crops removed from the block and fed to animals elsewhere on the farm, or exported.
Nutrients transferred in the gut of animals from the block to farm dairy, lanes and races, to a block after consuming feed on a feed pad, from a block to a wintering pad when pasture is consumed, and from a wintering pad/animal shelter and deposited on a block as excreta using nutrients consumed on the wintering pad. Transfers to a block are negative (block pastoral nutrient budget only).
Nutrients (N) losses via volatilisation from urine, fertiliser or other sources (background), and denitrification from urine or other sources (background). Denitrification also includes nitrous oxide emissions.
Nutrients transport from the farm in water, including leaching from urine patches or other sources (background), runoff, direct discharge to stream as drainage and direct deposition by animals, direct pond discharges from a 2-pond treatment system, border dyke outflow and septic tank losses.


Changes in pools

Difference in nutrient amount between the beginning and end of the year in the standing crop. The nutrient level is the total nutrients in the product removed, residues and roots multiplied by the proportion of total growth that has occurred. A negative value indicates that the nutrient in the standing crop was higher at the beginning than the end of the year (crop block nutrient budget only).
Difference in nutrient amount between the beginning and end of the year in stolons and roots added as residues. A negative value indicates that the nutrient in the residues was higher at the beginning than the end of the year (crop block nutrient budget only).
Gain of nutrients in the framework above and below ground of perennial fruit crops as the result of annual tree growth.

For crop and fodder crop blocks, organic pool for N is divided into estimated mineralisation from soil organic matter and decomposition from residues, and Net immobilisation (change in soil organic matter levels excluding the mineralisation and decomposition modelled, and includes the balancing error*).

In other blocks, the organic pool is the net change in nutrients (N, P and S) in soil organic matter and the balancing error*. A negative value indicates an addition (net mineralisation) whereas a positive term indicates a removal (net immobilisation).

In the farm nutrient budget, the Organic pool includes net immobilisation, including balancing errors* (shown as Organic pool sub-item), and accumulation in effluent storage ponds if they are emptied less frequently than once a year is included in the farm nutrient budget.
Nutrients adsorbed on clay minerals or released by weathering or slow release mechanisms. This also includes the undissolved portion of lime in the year of application, or the portion that dissolves in the year after application, which is negative.
Change in the conceptual plant available pool for the block. This pool is the pool related to soil test levels. Note that this is for the whole block (camp and non-camp areas) and hence should not be used to estimate maintenance or change in soil tests. A negative value indicates a net loss from the plant available pool. For nutrients other than N or S, blocks, the balancing error is including in the inorganic plant available pool.
For a block nutrient budget, the model assumes inputs equal outputs (nutrients removed and changes in long-term storage pools due to changes in soil organic matter, weathering, absorption, etc.).


The balancing error is the difference between initial estimated inputs and outputs and includes any errors associated with entered data or the estimation of terms in the nutrient budget, and unaccounted nutrients.


To balance the budget (to reduce the balancing error to zero) the ‘balancing error’ is allocated to items within the nutrient budget.

The Nutrient Budget



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