Abstract
Farmers in Rwanda do not apply P fertilizer on their crops. Bray and Kurtz #1 extractable P levels are generally less than 2 ppm on these soils. Therefore, a long-term experiment was established to determine the yield response of potatoes to P fertilizer. A maximum accumulated yield of 130 t/ha in 5 crops was obtained with 902 kg/ha of P. The no P treatments produced 72% of the average maximum yield. The external P requirements, determined with P sorption isotherms, averaged 0.04 μg/ml if equilibrated at 15 C and 0.02 μg/ml if equilibrated at 25 C for the 5 crops. The residual efficiency of the applied P fertilizer was less than 20%, suggesting that large applications of P are not advisable on Andepts, which have amorphous materials because the applied P is not available for subsequent cropping seasons.
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Vander Zaag, P., Kagenzi, C. The phosphorus requirements of five consecutive potato crops on an Andept in Rwanda. American Potato Journal 63, 121–129 (1986). https://doi.org/10.1007/BF02853536
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DOI: https://doi.org/10.1007/BF02853536