Prince Edward Island growers can reduce soil phosphorus buildup while maintaining carrot crop yield

Abstract

Producers seek to manage the application of nutrients in a manner that maximizes economic crop returns; however, emphasis must now include sensitivity to environmental issues such as increasing soil phosphorus. To address this issue in carrot (Daucus carota L.) production, we studied the effect of soil-applied P fertilizers on yield and soil P content in Prince Edward Island. Six field studies over a 3-yr period evaluated the yield response of carrot on sandy to loamy sand Orthic Podzol soils. Treatments consisted of pre-plant broadcast applied P at 0, 33, 66, 99 or 132 kg ha-1 on sites where residual P levels ranged from 81 to 162 µg P g-1. When the total yield response of carrots to increasing P levels was fitted to a quadratic response curve, 110 kg P ha-1 was required to achieve maximum yield, but an application of as little as 22 kg P ha-1 resulted in 95% of maximum marketable yield. This reduced application rate resulted in a saving of 88 kg P ha-1 and slowed the buildup of soil P levels. Therefore, by applying more conservative amounts of P fertilizer carrot growers can maintain excellent crop yield while reducing the potential for environmental damage caused by the buildup of soil P. Key words: Orthic Podzol soil P, tissue P, fertilizer P, maximum yield, Daucus carota L.