The first step when creating an analysis in OverseerFM is to define the blocks that make up the farm.
This article assumes the reader has extensive farm systems knowledge. Decisions on creating OverseerFM analyses are dependent on working knowledge of the farm being analysed.
Advice
- Try to combine paddocks in to blocks that are managed in a similar way - Larger blocks provide the model with more flexibility
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Draw blocks to get climate for that location
- The quality of the block drawings does not have any impact on the model, so you can just draw an approximation to get climate data
Management blocks
OverseerFM analyses nutrient movements within similarly managed land on a farm to produce nutrient budgets that identify where nutrients are being lost from the system (as leaching, run-off or emissions) rather than being converted into product. To do this OverseerFM defines blocks as land that is managed similarly.
OverseerFM is mostly interested in the nutrient flows through productive areas of the farm, but there is also the ability to include blocks of land that are not used to grow food, as these can have an impact on the farms nutrient footprint.
OverseerFM blocks include; pasture, crop, fruit, outdoor pig, trees and scrub, house, fenced wetlands and riparian. The following information relates to the productive block types, as no soil or management information is required for the other blocks.
What is a block?
As a block may contain multiple soils and irrigation, it could be defined as land used for a common purpose and managed in a similar way. It can be made up of areas of the farm separated from each other but managed in the same way.
Larger blocks provide the model with more flexibility in averaging out the usage of the block while creating many small blocks increases the risks of making mistakes in the data entry, in producing model errors and making reports hard for farmers, other consultants and others to understand. Because of this, when creating blocks, try to combine paddocks and only separate on soils and irrigation where it is significant to the area being modeled. The "illusion" of more precision with smaller blocks can be counter productive and should be avoided.
When dividing a farm into blocks, each block should:
- Grow the same pasture/fruit or crop
- Support similar animals
- Have similar climate
- Have similar topography (for pastoral blocks)
- Have similar fertiliser applied
- Have the same drainage system
Soil and water added through rain or irrigation are important factors in drainage and nutrient flows and previous versions of Overseer software have required setting up management blocks based on a single soil type and irrigation application. To reduce data entry effort and align with farm practice, OverseerFM allows for up to three soils and two irrigation systems per management block. The model breaks these down in the background.
If you import a farm file where the blocks have been divided by soil/irrigation, these will be imported as is. You have the choice of combining the blocks (using the simplify tool) or leaving them separated. We suggest leaving older analyses and only converting the new ones that will be used going forward.
Block Types
A block type defines the basic farm anatomy and types of management that occur on an area of
land within the farm. Allowable block types are:
Pasture- A pastoral block is a block growing pasture or lucerne and with animals grazing. Some pasture can be removed for animal supplements. There are two types of pastoral blocks: permanent pasture blocks, and pasture blocks through which a fodder crop rotates.
Crop - A crop block is a block that is cultivated and sown in vegetable, arable or fodder crops.
Although animals may graze the block during a pasture phase, or as part of the crop
management, the primary focus of the block is the crop.
Fruit - A fruit crop block is a block that has a permanent fruit crop grown on it. Currently five fruit
crops (kiwifruit, apples, grapes, avocadoes, and peaches) can be modelled. Fruit crop blocks
are assumed to have a flat topography.
Outdoor Pigs - Outdoor pigs blocks are blocks where outdoor pigs are keep. For for information on modelling these, see here
Trees and Scrub - Trees and scrub blocks typically have lower nutrient inputs and outputs than other block types. You can also add forest details to Trees and Scrub blocks to determine their carbon sequestration for GHG reporting purposes.
House - House blocks can discharge nutrients via septic tanks, cultivated areas (gardens) or runoff from
hard surfaces. On larger (takes account of land use intensity) farms, the contribution from the
house block can be a non-significant proportion of total property losses and hence can be
ignored. However, on small blocks, the contribution from the house block may be a significant
part of whole property losses. Multiple house blocks can be added together into one block.
Fenced Wetland - Fenced wetlands are wetland areas that have been fenced off to all grazing. These may include natural or artificial wetlands. Wetlands can also be listed as a farm input or artificial wetlands
entered as treating outlets of mole/tile drainage systems under the Drainage tab - it is important that the same wetland areas are not included in both sections
Riparian - A riparian block or strip is an area fenced off such that runoff water passes through it before
reaching a water body such as a stream. A riparian block is the fenced areas around streams.
A riparian strip or filter is an area fenced off to intercept runoff within a block.