Relationship between soil phosphorus and phosphorus budget in grass sward with varying nitrogen applications
Messiga, A.J., Ziadi, N., Bélanger, G., Morel, C. (2014). Relationship between soil phosphorus and phosphorus budget in grass sward with varying nitrogen applications, 78(4), 1481-1488. http://dx.doi.org/10.2136/sssaj2013.05.0200
Canges in soil available P usually relate to P budgets, but the sensitivity of the relationship to N fertilization is poorly understood. Four P rates (0, 15, 30, and 45 kg ha-1) as main plots and four N rates (0, 60, 120, and 180 kg ha-1) as subplots were applied each year from 1999 to 2006 to a timothy (Phleum pratense L.) sward established in 1998 on a gravelly sandy loam soil (Typic Fragihumods). Soil available P was assessed using water (Cp) and Mehlich-3 (PM3) extractions. Annual P budgets were calculatedas the difference between applied P and P offtake and were then summed over the duration of the experiment to determine the cumulative P budget (Bcum). Over the 8-yr study, Bcum (-148 to 286 kg P ha-1), Cp (0.13 to0.94 mg L-1), and PM3 (22.3 to 111.7 mg kg-1) were affected by both Pand N fertilization. The Cp and PM3 were linearly related to Bcum and the relationship was similar among N rates [Cp = 0.0016Bcum + 0.3 (r2 = 0.86, P < 0.001) and PM3 = 0.20Bcum + 47.7 (r2 = 0.90, P < 0.001)]. A positive or negative Bcum of 100 kg P ha-1 would then raise or deplete Cp by 0.16 mg L-1 and PM3 by 20 mg kg-1. The relationship between Bcum and soil available P was not affected by N applications in this gravelly sandy loam soil. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA.
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