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30 March 2016 Consequences of Ontario P index recommendations for reduced manure and fertilizer phosphorus applications on corn yields and soil phosphorus
M.A. Ribey, I.P. O'Halloran
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Abstract

Environmental indices for soil P limit P applications when soil tests and risk of P losses exceed a given threshold. Producers' reluctance to reduce P inputs often stem from concerns regarding reduced crop production and soil fertility. Our objectives were to identify changes in soil P fractions after 4 yr of repeated manure or fertilizer P applications at rates ≤ crop removal by corn (Zea mays L.), and the impact of these applications on yields. Olsen P and soil P fractions extracted using a modified Hedley P fractionation procedure were measured. Corn yields were nonresponsive to P applications. After 4 yr, Olsen P was 16.6 and 24.6 mg kg-1 at the application rates of 0 and 33 kg P ha-1 yr-1, respectively, for the inorganic fertilizer treatment indicating that soil P drawdown was occurring. Only the most labile forms of Pi (resin and bicarbonate extractable) were affected by treatment, with greater values at higher P application rates. Adherence to Ontario's P index recommendations for P applications at or below crop removal should not be a crop production concern. Furthermore, given the rate of soil labile P drawdown, routine soil testing (every 3-5 yr) would identify agronomically significant changes in soil test P before the crop yield is impacted.

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M.A. Ribey and I.P. O'Halloran "Consequences of Ontario P index recommendations for reduced manure and fertilizer phosphorus applications on corn yields and soil phosphorus," Canadian Journal of Soil Science 96(2), 191-198, (30 March 2016). https://doi.org/10.1139/cjss-2015-0072
Received: 28 July 2015; Accepted: 1 February 2016; Published: 30 March 2016
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KEYWORDS
application de fumier
dosage du P du sol
engrais P
fertilizer P
fractionnement du P
manure applications
P fractionation
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