Defining growth, development and management / cut of a grass-clover composite crop

[Kamau Katana Lindhardt]

Hi everyone,

I am working on a crop rotation that includes a 2-year grass-clover crop (). 

Based on the group discussion: https://groups.google.com/g/daisy-model/c/3z94jVshI6s/m/qn9pg4_KAQAJ I see that I would need to change the DSmax to 3 (allowing for re-growth all the time). I have done this, like this:

"
;; Grass-Clover setup (based on a Grass and a Clover composite crop 'intercrop')
;; Grass
(defcrop "grass_new" "Grass to grain"
(Devel original
(DSRate1 0.005)
)
(Harvest
(DSmax 3.0) ; DSmax is the maximum DS-value where the crop survives a cut, is set to 3, meaning that it can be cut at any stage and re-grow
)
)

;; White clover
(defcrop "wclover_new" "Wclover"
(Devel original
(DSRate1 0.05))
(Harvest
(DSmax 3.0) ; DSmax is the maximum DS-value where the crop survives a cut, is set to 3, meaning that it can be cut at any stage and re-grow
)
) 

"

My questions are:

Question 1. How can I define this grass-clover composite crop in a way that allows simultaneous management (i.g. both grass and clover are cut and fertilised at the same time - all the time)? Right now, I have a situation where I sometimes get a cut of my grass crop without the cut of my clover (something that is practically unrealistic). 

"
[...]
;; Simultaneous sowing of Grass and White Clover (composite crop)
  (wait_mm_dd 8 28)
  (sow "grass_new" (seed 20 [kg w.w./ha]))   ;; Grass ( xx %)
  (sow "wclover_new" (seed 15 [kg w.w./ha])) ;; White Clover (xx %)
 
  ;; Fertilization before the first cut
  (wait_mm_dd 4 15)
  (fertilize ("N_min_fertilizer" (weight 85 [kg N/ha])))
 
  ;; 1st Cut + Fertilization on May 22nd
  (wait_mm_dd 5 22)  ;; 1st cut on May 22nd
  (cut "grass_new" (stub 5.0 [cm]))
  (cut "wclover_new" (stub 5.0 [cm]))
  (wait_days 1)
  (fertilize ("N_min_fertilizer" (weight 85 [kg N/ha])))
[...]

(output log)

** 2017-09-05T08:00:00*** Fine_sandy_loam

**** crop: grass_new harvest
Phenology reverted

Cutting grass_new, removing 0 + 3.91904 Mg DM/ha
Cutting wclover_new, with no yield :-(
** 2017-09-05T17:00:00

"

Question 2. As I want the DAISY simulation to resemble as much as possible my field experiment, I need to implement 5 cuts at designated times throughout the growing season (as that is the case for my field experiment). How can I do that, without ending in a situation where I get the message: "Cutting wclover/grass, with no yield :-("


In advance, thank you for your help
All the best,
Kamau

[Per Abrahamsen]

Hi Kamau,

First I advice you to log the two crops individually, to see what/when something go wrong:

(output (Crop (crop "grass_new")) (Crop (crop "wclover_new")))

Second, when you fertilize a grass / clover mixture, I expect the grass to outcompete the clover.  It grows faster, and the grass leaves will shadow the clover leaves, preventing growth.  

** New "min_light_fraction" crop parameter.
You can now specify that a certain fraction of the crop in a mixed
crop field get exclusive access to the light.  For example

  (progn
    (sow "Spring Barley" )
    (sow ("Grass to grain" (min_light_fraction 0.2))))

Here, 20% of the light will be reserved for the grass, for the
remaining 80% the grass and barley will compete, with the highest crop
shadowing for the other.

This is intended to emulate small "patches" in the field, where one
crop dominates for some reason.

Again, the tall crop shadow low crop effect is real, so you may not need to do this.

There are other possible problems with e.g. height and partitioning as function of DS, but you will have to look at the data first.

Let me know whether this helps.

Per 

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