The flows and balances of N, P and K were studied in 20 farms in the Campo Ma'an area in Cameroon between March and August 2002 to assess the nutrient dynamics in smallholder farms. Data were collected through farmer interviews, field measurements and estimates from transfer functions. Nutrient input from mineral (IN1), animal feed (IN2a) and inorganic amendments (IN2b) was absent. Major outputs were through crop (OUT1a) and animal (OUT1b) products sold. Partial budgets for farmer managed flows were negative: À65 kg N, À5.5 kg P and À30.8 kg K ha À1 year À1 . For inflows not managed by farmers, deep capture (IN6) was the major source: 16.6, 1.4 and 6.6 kg ha À1 year À1 of N, P and K, respectively. Atmospheric deposition (IN3) was estimated at 4.3 kg N, 1.0 kg P and 3.9 kg K ha À1 year À1 , and biological nitrogen fixation (IN4) at 6.9 kg N ha À1 year À1 . Major losses were leaching (OUT 3a): 26.4 kg N, and 0.88 kg K ha À1 year À1 . Gaseous losses from the soil (OUT 4a) were estimated at 6.34 kg N, and human faeces (OUT 6) were estimated at 4 kg N, 0.64 kg P and 4.8 kg K ha À1 year À1 . The highest losses were from burning (OUT 4c), i.e. 47.8 kg N, 1.8 kg P and 14.3 kg K ha À1 year À1 . Partial budgets of environmentally controlled flows were negative only for N À4.8 kg N, +2.4 kg P and +9.6 kg K ha À1 year À1 . The overall farm budgets were negative, with annual losses of 69 kg N, 3 kg P and 21 kg K ha À1 . Only cocoa had a positive nutrient balance: +9.3 kg N, +1.4 kg P and +7.6 kg K ha À1 year À1 . Nutrients reaching the household waste (1.9 kg N, 2.8 kg P and 18.8 kg K ha À1 year À1 ), animal manure (4.9 kg N, 0.4 kg P and 1.6 kg K), and human faeces (4 kg N, 0.64 kg P and 4.8 kg K ha À1 year À1 ) were not recycled. Five alternative management scenarios were envisaged to improve the nutrient balances. Recycling animal manure, household waste and human faeces will bring the balance at À62.6 kg N, 0 kg P and +1 kg K ha À1 year À1 . If, additionally, burning could be avoided, positive nutrient balances could be expected.
The flows and balances of N, P and K were studied in 20 farms in the Campo Ma'an area in Cameroon between March and August 2002 to assess the nutrient dynamics in smallholder farms. Data were collected through farmer interviews, field measurements and estimates from transfer functions. Nutrient input from mineral (IN1), animal feed (IN2a) and inorganic amendments (IN2b) was absent. Major outputs were through crop (OUT1a) and animal (OUT1b) products sold. Partial budgets for farmer managed flows were negative: À65 kg N, À5.5 kg P and À30.8 kg K ha À1 year À1 . For inflows not managed by farmers, deep capture (IN6) was the major source: 16.6, 1.4 and 6.6 kg ha À1 year À1 of N, P and K, respectively. Atmospheric deposition (IN3) was estimated at 4.3 kg N, 1.0 kg P and 3.9 kg K ha À1 year À1 , and biological nitrogen fixation (IN4) at 6.9 kg N ha À1 year À1 . Major losses were leaching (OUT 3a): 26.4 kg N, and 0.88 kg K ha À1 year À1 . Gaseous losses from the soil (OUT 4a) were estimated at 6.34 kg N, and human faeces (OUT 6) were estimated at 4 kg N, 0.64 kg P and 4.8 kg K ha À1 year À1 . The highest losses were from burning (OUT 4c), i.e. 47.8 kg N, 1.8 kg P and 14.3 kg K ha À1 year À1 . Partial budgets of environmentally controlled flows were negative only for N À4.8 kg N, +2.4 kg P and +9.6 kg K ha À1 year À1 . The overall farm budgets were negative, with annual losses of 69 kg N, 3 kg P and 21 kg K ha À1 . Only cocoa had a positive nutrient balance: +9.3 kg N, +1.4 kg P and +7.6 kg K ha À1 year À1 . Nutrients reaching the household waste (1.9 kg N, 2.8 kg P and 18.8 kg K ha À1 year À1 ), animal manure (4.9 kg N, 0.4 kg P and 1.6 kg K), and human faeces (4 kg N, 0.64 kg P and 4.8 kg K ha À1 year À1 ) were not recycled. Five alternative management scenarios were envisaged to improve the nutrient balances. Recycling animal manure, household waste and human faeces will bring the balance at À62.6 kg N, 0 kg P and +1 kg K ha À1 year À1 . If, additionally, burning could be avoided, positive nutrient balances could be expected.
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