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Nutrient flows in perennial crop-based farming systems in the humid forests of Cameroon

Ehabe E.E., Bidzanga N.L., Mba C.M., Nkengafac Njukeng J., De Barros I., Enjalric F.. 2010. American Journal of Plant Sciences, 1 (1) : p. 38-46.

DOI: 10.4236/ajps.2010.11006

A study was conducted in some perennial crop-based farms in the humid forests of South West Cameroon, to better understand their soil fertility patterns and management and identify factors that contribute most to nutrient depletion trends in such multi-storey farmholdings. The main perennial crops were the para rubber tree (Hevea brasiliensis), cocoa (Theobroma cacao) and oil palm (Eleais guineensis) whose ages ranged from immature to very old (senescence). Data were collected over a two-year period (2007 and 2008) and modelled using the farm NUTrient MONitoring (NUTMON) tool. Results showed that the farming systems played key roles in the overall exploitation strategies. Plantain and cassava (annual crops) and cocoa (perennial) were the most associated crops, accounting for more than half of intercropped frequencies. Whereas nutrient flows within and between farm units were confirmed, the net loss in soil N, P and K nutrient balances differed with the main perennial crop - being highest for the oil palm and lowest for the rubber tree. The average nutrient balance of each farm was markedly negative for N but positive for P and K. Partial nutrient balance (ignoring biophysical flows like N-fixation, leaching and erosion) was positive for the three nutrients indicating therefore that the biophysical flows accounted more for N depletion. Nitrogen loss was mainly due to, leaching (~70%), volatilization (~20%), and exported crops and their residues.

Mots-clés : forêt tropicale humide; agroforesterie; theobroma cacao; hevea brasiliensis; elaeis guineensis; plante de culture associée; cameroun

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