Buckwheat Potential to Contribute Solubilized Soil P to Subsequent Crops.

Several reports supporting folklore beliefs that buckwheat (Fagopyrum esculentum Moench) can significantly contribute phosphorus (P) to subsequent crops by solubilizing sparingly soluble soil P to available forms remain anecdotal. A one-year field trial was conducted to quantify the amount of P solubilized by buckwheat from five inorganic and three organic P pools in a one-year fallow Fargo silty clay soil in Fargo, ND. Spring wheat (Triticum aestivum L.), considered an inefficient P solubilizing plant was grown as a reference crop to buckwheat to determine P uptake and P mineralized. Both plants were grown with no fertilizer input using a complete randomized design with six replicates. Soil samples were collected from each plot at 0-15 cm depths at pre-plant and at post-harvest. The P content was extracted by sequential fractionation from the inorganic pool [labile, aluminum (Al)-, iron (Fe)-, reductant-soluble-, and calcium (Ca)-bound P] and organic pool (labile, moderately labile, and non-labile) and analyzed by spectrophotometry. Phosphorus changes between pools were indicative of solubilization from more recalcitrant to easily absorbed P pools. Calcium-bound P pool, with the highest P content (266 kg ha^-1), contributed the most P (72% of inorganic pool) to the available fraction and to P uptake by buckwheat (40 kg ha^-1) and wheat (16 kg ha^-1) . Significantly more P was taken up (p < .05) by buckwheat (16 kg ha^-1) than wheat from the inorganic soil fractions. Wheat took up significantly (p < 0.05) more P than buckwheat from the organic P fraction. Following buckwheat and wheat harvest, significantly more P was found in available P pools after buckwheat compared with wheat. This finding suggests that more P may indeed be available to crops following buckwheat under these conditions compared with wheat.