Table 11a. Fertilization (kg/ha/week) with inorganic fertilizers based on secchi disk reading
Secchi disc (cm)	Nitrogen	Phosphorus1	Urea	Triple super phosphate (50%)
20�25	0	0	0	0
25�30	0	0	0	0
30�354	5	2	11	4
35�40	10	2	22	4
>403	20	2	44	4
Source: Adapted from, Boyd and Tucker (1998); Boyd (2005); Fox (2008b)
1P as P2O5 (Boyd, 2003c). Phosphorus is generally limiting in algae production.
2Maximum theoretical photosynthesis: 8 kg N and 0.8 kg P/ha/d (Fox, 2008b).
3Fertilization may be suspended below 35 cm, especially where feed rates are higher.
Table 11b. Some inorganic and organic fertilizers used in shrimp aquaculture.
Inorganic Fertilizer	Nitrogen %	Phosphorus % (as P2O5)	Kg4,5 to get 20 kg N/ha�	Kg4,5 to get 1 kg P/ha (as P2O5)	Fertilization1 in kg/ha to add based on available nitrogen in the soil (12.5 mg/100 g soil)	Fertilization in kg/ha to add based on available nitrogen in the soil (25 mg/100 g soil)	Fertilization in kg/ha to add based on available nitrogen in the soil (50 mg/100 g soil)	Fertilization in kg/ha to add based on available phosphorus in soil (1.5 mg/100 g soil)	Fertilization in kg/ha to add based on available phosphorus in soil (3 mg/100 g soil)	Fertilization in kg/ha to add based on available phosphorus in soil (6 mg/100 g soil)
Urea	45	0	44		100	50	25	�	�	�
Ammonium nitrate	33�35	0	59		132	66	33	�	�	�
Ammonium sulfate	20�21	0	95		214	107	54	�	�	�
Ammonium phosphate	11	48	182	2	409	205	102	40	20	10
Diammonium phosphate	18	48	111	2	250	125	63	40	20	10
Calcium nitrate	15	0	133		300	150	75	�	�	�
Sodium nitrate	16	0	125		281	141	70	�	�	�
Super phosphate	0	18�20		5	�	�	�	100	50	25
Triple super phosphate	0	44�54		2	�	�	�	38	19	10
Gypsum	0	0			�	�	�	�	�	�
NPK(S)6 (e.g. 15�15�15)	Variable (15)	Variable (15)	133	7	300	150	75	127	63	32
Mono ammonium phosphate	11	48	182	2	409	205	102	40	20	10
	Nutrient content (%)					Organic carbon in soil (1 000 mg/100 g soil)7	Organic carbon in soil (500 mg/100 g soil)7	Organic carbon in soil (250 mg/100 g soil)7
Organic fertilizer	Nitrogen	Phosphorus	Potassium	Sulphur	Moisture	Amount of organic manure (kg/ha) to add	Amount of organic manure (kg/ha) to add	Amount of organic manure (kg/ha) to add
Cow dung (fresh)	0.5	0.15	0.5	�	60	500	1000	2000
Cow dung (decomposed, dry)	1.2	1	1.6	0.13	35	208	417	833
Poultry manure	1.9	0.56	0.75	1.1	55	167	333	666
Sheep, fresh	1.4	0.2			77	179	357	714
Compost	0.75	0.6	1	�	40	333	667	1333
Adapted from Knud�Hansen et al. (1998); CIBA (1994, 2003)
See also FAO (1987a) for a more detailed table on inorganic fertilizers (http://www.fao.org/docrep/field/003/ab468e/AB468E03.htm)�
1Available nitrogen in soil at 250 to 750 mg/kg (ppm) is good for aquaculture (Boyd, 2003b).
2Available phosphorus above 60 ppm in the soils is good for aquaculture (Boyd, 2003b).
3Organic carbon of 1.5 to 2.5 % is good (Boyd, 2003b).
4Minimum nitrogen and phosphorus concentrations to stimulate eutrophication are 0.01 to 0.1 mg P/Iitre and 0.08 to 0.8 mg N/litre (Boyd, 2003b).
5Fox (2008b), "Typical ratio (N:P) for brackishwater ponds is around 12-20:1"; Phytoplankton:  50 % C, 9 % N, 1 % P.
6N, nitrogen, P, phosphorus, K, potassium, S, sulphur. In 100 kg of 15-15-5, you�ll have 15 kg N, 15 kg P2O5 and  5 kg of K2O.
7For example, if the soil organic  carbon level is 500 mg/100 grams of soil sample, 417 kg of decomposed dry cow dung is sufficient as an organic matter application.