Table 2: Mean yields of rice grain, Nile tilapia (Oreochromis niloticus) and mallard duck (Anas platyrynchos) eggs in different rice-based cropping systems.
 

Cropping systems

Rice yield

Nile tilapia yield

Eggs production

(t/ha/year)

(t/ha/year)

(eggs/ha/year )

1

Rice+HM-fallow-Rice+HM

5.49 e

-

-

2

RF+HM-fallow-RF+HM

6.05 de

0.39 d

-

3

Rice-fallow-Rice

5.32 e

-

-

4

RF-fallow-RF

4.32 f

0.29 d

-

5

RA-(fallow-Azolla)-RA

6.36 cd

-

-

6

RD-duck-RD

5.82 de

-

84,774 a

7

RFA-(fallow-Azolla)-RFA

7.38 b

0.55 c

-

8

RFD-duck-RFD

6.85 bc

1.26 b

89,165 a

9

RAD-(duck-Azolla)-RAD

8.82 a

-

87,900 a

10

RFAD-(duck-Azolla)-RFAD

8.69 a

1.39 a

81,607 a

* Legend: R+HM = rice monoculture with herbicide (H) and molluscicide (M);
RF+HM = rice-fish culture with HM; R = rice monoculture; RF = rice-fish;
RA = rice-Azolla; RD = rice-duck; RFA = rice-fish-Azolla; RFD = rice-fish-duck;
RAD = rice-Azolla-duck; RFAD = rice-fish-Azolla-duck.

Notes:
1. Means having common letters are not significantly different at the 5 % level of significance.
2. Values are average of three replicates.
3. Yield per year consisted of two croppings (dry season and wet season 1996)
4. Egg laying period = 359 days (January - December 25, 1996)