Table 11a. Fertilization with inorganic fertilizers based on secchi disk reading.
Secchi disc (cm)	Nitrogen  kg/ha/ week4	P, kg/ha/ week1	Fertilize as urea kg/ha/week4	Fertilize as triple super phosphate (50%) kg/ha/ week4
20�25	0	0	0	0
25�30	0	0	0	0
30�35 3	5	2	11	4
35�40	10	2	22	4
>40 2	20	2	44	4
Abbreviations:  P2O5, Phosphorus oxide; N, nitrogen; P, phosphorus.
Source: Boyd and Tucker (1998), Boyd (2005), Fox (2008b).
1P as P2O5 (Boyd, 2003c). Phosphorus is generally limiting algae production.
2Max 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.
4Applied to the water (dissolved).
Table 11b. Some inorganic and organic fertilizers used in shrimp aquaculture.
Inorganic Fertilizer8	Nitrogen %	Phosphorus % (as P2O5)	kg to get��� 20 kg N/ha 4,5,6	kg to get 1 kg P/ha (as P2O5) 4,5,6	Fert. based on available Nitrogen: 12.5 mg/100 g soil1,7	Fert. based on available Nitrogen: 25 mg/100 g soil7	Fert. based on available Nitrogen: 50 mg/100 g soil7	Available Phosphorus in soil (mg/100 g soil): 1.5 2,7	Available Phosphorus in soil (mg/100 g soil): 3 2,7	Available phosphorus in soil (mg/100 g soil): 6 2,7
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) (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 (mg/100 g soil): 1000	Organic carbon in soil (mg/100 g soil): 500	Organic carbon in soil (mg/100 g soil): 250
Organic fertilizer	Nitrogen	Phosphorus	Potassium	Sulphur	Moisture	Amount of organic manure (kg/ha) to add7	Amount of organic manure (kg/ha) to add7	Amount of organic manure (kg/ha) to add7
Cow dung (fresh)	0.5	0.15	0.5	�	60	500	1 000	2 000
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	1 333
Abbreviations: NPK(S), fertilizer with nitrogen, phosphorus, potassium and sulphur; P2O5, phosphorus oxide; N/ha, nitrogen per hectare; P/ha, phosphorus per hectare.
Source: Knud�Hansen et al. (1998), CIBA (1994, 2003a).
1 Available nitrogen in soil at 250 to 750 mg/kg (ppm) is good for aquaculture (Boyd, 2003b).
2 Available phosphorus above 60 ppm in the soils is good for aquaculture (Boyd, 2003b).
3 Organic 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/I and 0.08 to 0.8 mg N/l (Boyd, 2003b).
5Fox (2008b):  "Typical ratio (N:P) for brackishwater ponds is around 12-20:1"; Phytoplankton:  50% C, 9% N, 1% P.
6Applied to the water (dissolved).
7Applied to the soil before filling.
8See also FAO (1987c) for a more detailed table on inorganic fertilizers (http://www.fao.org/docrep/field/003/ab468e/AB468E03.htm) .