Effect of long-term fertilization and placement of phosphorus on barley yields
Karamanos, R. E. and Kruger, G. A. 2009. Communications in Soil Science and Plant Analysis. 40: 538-554.
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An experiment that was established in 1982 to assess placement of phosphorus (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 2002. 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 resulted in significant reduction in barley grain yield that was greater in the treatments where P was seedrow placed (21%) than where P was either banded (12%) or one third seedrow placed and two thirds banded (15%). Four-week burial of anion PRS TM 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 more than 90% of variations both in P removal and yield of barley over the duration of the experiment.