Assistance Needed with Crop Rotation Simulation in APSIM NextGen

[cranju]

Hi,

I’m currently working on simulating various crop rotations in APSIM NextGen, including some that involve mixed cropping/grazing systems and others with longer rotations of cereals, legumes, and fallow periods. I've started with a basic rotation of Wheat_Barley_Wheat_Fallow but am encountering difficulties. Specifically, I’m unsure how to use the Arc function to properly simulate harvesting one crop and simultaneously initiating the sowing of another.

I’ve looked into several examples and papers, but most seem to focus on crop/pasture_fallow or similar sequences, which doesn’t fully address my needs. I’m attaching my weather file and simulation file for reference. Could someone guide me on how to approach this?

Thanks in advance for your help!

crop_rotation.zip

[peter-devoil]

The issue is that there is a need for an "end crop" time to be different from a "start of crop" time - as different things happen: at the end of a crop it is harvested and yield calculated, and at the start a seed bed is prepared, fertiliser applied etc, etc. Apsim shouldn't do all this on one day. And if you have any flexibility in what to do after the crop is harvested (ie multiple arcs leading away from a node), you'll want that to occur at some distant time - the decisions are often made at different times (eg early vs late sowing)..

If you try to collapse all this temporal complexity to two nodes connected by an arc, then some things (eg harvest) are delayed, and others (eg sowing) are premature: apsim's rules are evaluated each day and transitions made immediately.

A lot of the reason for this grief was calling the in between nodes "fallow". They're not a fallow - should be a "period of time with no crop in the ground", and if anybody comes up with a good word for that, I'd be grateful..