Relationship between soil phosphorus and phosphorus budget in grass sward with varying nitrogen applications.

Messiga, A.J., Ziadi, N., Bélanger, G., and Morel, C. (2014). "Relationship between soil phosphorus and phosphorus budget in grass sward with varying nitrogen applications.", Soil Science Society of America Journal, 78(4), pp. 1481-1488. doi : 10.2136/sssaj2013.05.0200  Access to full text

Abstract

Changes 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 ha1) as main plots and four N rates (0, 60, 120, and 180 kg ha1) 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 (P{SUB}M{/SUB}3) extractions. Annual P budgets were calculated as 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 ha1), Cp (0.13 to 0.94 mg L1), and P{SUB}M{/SUB}3 (22.3 to 111.7 mg kg1) were affected by both P and N fertilization. The Cp and P{SUB}M{/SUB}3 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 P{SUB}M{/SUB}3 = 0.20Bcum + 47.7 (r2 = 0.90, P < 0.001)]. A positive or negative Bcum of 100 kg P ha1 would then raise or deplete Cp by 0.16 mg L1 and P{SUB}M{/SUB}3 by 20 mg kg1. The relationship between Bcum and soil available P was not affected by N applications in this gravelly sandy loam soil.

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