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How crop inputs impact the model

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Summary

Crop blocks require two years of crop data to be entered. Activities such as cultivation, sowing, harvesting and defoliation are entered on a monthly basis. The nutrient and GHG results are generated for the final year (reporting year), while the previous years activities are used to set up the nitrogen soil pool for the start of the reporting year. In this way OverseerFM is able to consider previous activities in the analysis of a "typical" years nutrient transfers.

The following diagram depicts what parts of the model the crop information entered in OverseerFM impacts. For a full interactive view of the scientific model in its entirety please click here

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Impact

Crop type defines characteristics that drive crop cover, growth, metabolic energy if fed to animals and nutrient uptake. Cover affects surface runoff (hydrology), while growth and uptake affect nutrients being fed to animals as crops and the amount of nitrogen in the soil pool.

Advice

  • Where appropriate similar paddocks (soil, climate and crops) can be grouped as well as Similar crops. OverseerFM identifies categories of crops that can be grouped due to similarities - see Crop types in OverseerFM

  • The model includes your defined cultivation practice in the month of sowing, so only enter a cultivation event if cultivation occurs in any month other than that month.

  • Avoid using non-farm animals for defoliation as model makes a large number of assumptions about those animals. If known set up the animals as an enterprise on the farm.

Details

In the past these were also broken down by soil and irrigation, with OverseerFM the number of blocks can now be reduced.

Some crop farms may be able to combine “like” paddocks into single blocks, therefore reducing the complexity of the analysis. The definition of what is a “Like” paddock comes down to what is needed to understand the farm system being run and what possible changes are being analysed.

Each crop in Overseer defines a set of characteristics that influence how nutrients build up and are used in the soil. So, crops with similar characteristics will provide similar results. Please refer to Crop types in OverseerFM.

“Like” paddocks would run the same or a similar rotation of the same or similar crops. Some of the paddocks may have differed in the previous year’s crops, but if they are similar it may be good enough to build a representation of the previous year for the block. Each year you may reconfigure the blocks as you change the rotations.

You may block up based on wanting to understand the effect of using different parts of the farm in different ways, because the soils are different, drainage is different, or the climate is different.

Crops are entered over a two-year period. The model moves through each month estimating the nitrogen pools in the soil. The previous year is used to set up the pools for the reporting year.

Over time residue decomposition occurs, releasing nutrients from the soil. The amount released is affected by temperature, the soils water capacity and the cultivation practice. Using conventional tillage has a greater effect on the nutrients released.

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