Assessment of Phosphorus Status in a Long-Term Tillage and Phosphorus Placement Experiment

Abstract

A long-term experiment to examine the impact of nitrogen (N) and phosphorus (P) on the yields of crops in a wheat–canola–triticale–pea–barley rotation under conventional and no-till/direct-seeding conditions was established in 1979 at the Breton and Ellerslie experimental farms of the University of Alberta. A number of treatments, replicated four times, were employed; however, they were subsequently modified to accommodate added treatments. Tillage treatments were not replicated. Consistent throughout the 30 years of this experiment for both cultivation systems were three treatments, namely, control, in-row, and mid-row banded application of 17 to 20 kg P/ha with application of 74 kg N ha⁻¹. Detailed soil analyses, including both chemical and anion resin (PRS™ probes) techniques were carried out on the three permanent treatments, described previously, in 2007. Yield data for a complete rotation of crops covering the period of 1997 to 2007 only are included in this study. Total grain production (all crops) over the period was 15% to 27% greater under the tilled system. Over the 20 years that barley was grown, yield increases were greater (P < 0.05) with in-row application of P only under the direct-seeding system. However, wheat canola, triticale, and pea grain yield increases were greater with in-row than mid-row placement of P under both tillage systems. The agronomic efficiency of in-row application of P was consistently greater than mid-row placement of P only under direct seeding. PRS 28-d burial or 24-h equilibration in the laboratory provided a better estimated of P availability (r = 0.88 and 0.89, respectively) than bicarbonate-extractable P (r = 0.57).

Keywords:

• Apparent crop recovery
• bicarbonate-extractable P
• fertilizer-use efficiency
• PRS probes