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Impact of discontinuing phosphorus fertilization after 20 years on barley yields and soil phosphorus status

Karamanos,R.E., J.T. Harapiak and G.A. Kruger. 2007. MSSS Conference Proceedings


An experiment that was established in 1982 to assess placement of P fertilizer on the yield of continuous barley was terminated in 2004, after annual application of P (30 kg ha-1) was discontinued in all but one treatment in 2001. Total removal of P during the first 20 years of the experiment (615 kg P2O5 ha-1) was virtually equal to total P application (600 kg P2O5 ha-1); however, when removal by the control that was fertilized with N only was subtracted from the total removal, a residual P component of 474 kg P2O5 ha-1 was obtained as a result. In spite of this, discontinuing P fertilization after 20 years of annual application of 30 kg P2O5 ha-1 resulted in significant reduction in barley grain yield that was greater in the treatments that P was seedrow placed (21%) than either banded (12%) or 1/3 seedrow placed and 2/3 banded (15%). Four week burial of PRS™ probes in 2006 allowed us to ascertain the reasons for these differences that reflected management and P placement practices. The use of PRS™ probes allowed us to interpret 93% of variations in P removal by barley over the duration of the experiment.