Jacky Foo wrote:
>In your paper, you have two case studies comparing the use of
>anaerobically digested manure and manure for fish farming
>(a) in Jiangsu Province and
>(b) in Taixian County.

Both cases came from Jiangsu Province: one in Guquan Village Nanjing
Jiangsu and the other in Taixian Jiangsu.

>There are a number of items in the first study in Jiangsu Province
>that are no clear to me.
>
>The set up is that
>(a) biogas-digester slurry (chicken manure (30-60%)+pig manure)
>is added into the 913 m2 "slurry pond" (852 m3 water volume,
>av. depth=1.4m).
>(b) chicken manure and grass are added into the 3,260 m2
>"manure pond" (6,520 m3 water volume, av. depth=2m)
>(c) the fish stocking density was the same (fingerlings 0.13 kg/m3)
>based on the effective water body.
>
>Comment 1:
>there is an error in the calculation of the effective water body for
>the slurry pond. i.e. a 913 m2 pond with 1.4 m depth would
>give 1,278 m3 effective water body (not 852 m3)

Slurry came from the digester. The input (pig manure) of digester came from
a pigsty.
1.37 mu x 1.4 m (average depth) = 1277 m3.
Here the pond bottom was just like a bowl bottom so that the water capacity
could not be 1277 m3. According to the original data, the effective water
volume was 852 m3.

In the manure pond, it is the same as above, i.e. 4.89 mu x 2 m = 6,513 m3.
The effective water volume varied as the water depth changed due to
evaporation or leakage, etc.

>Then you used a fingerling stocking of 0.13 kg / m3, i.e. slurry pond
>would get 110 kg fingerlings (using 852 m3 data) and the manure
>pond would get 847 kg of fingerlings. However, in Table 2 of your
>paper, stocking is different as shown in the Table columns
>"Net wt" and "Size (gram)" and "Weight (kg/mu)".
>
>Q1: what is the different in the "net wt" total and "size" total and
>how are these different from the above 110 kg in slurry pond
>and 847 kg in manure pond ?.
>1 mu (1/15ha)= 666.6 m2. and the manure pond received
>126.3 kg fingerlings/mu or 0.189 kg/m2 or 1,235 kg in manure pond.

The stocking density were 85 kg/mu and 167.3 kg/mu, respectively. I think
the figures were correct. The figure 0.13 kg/m3 was an
estimate. You may forget this.

Table 2, deduct the stocking weight from the gross weight, and then we get
the net weight.
 

-Li Kangmin