Response of canola to different seed-row placed fertilizer phosphorus forms, opener configurations and rates of application

Abstract

Maintaining canola yields requires that phosphorus (P) removed from soil in crop harvest is replaced through P fertilizer application. Rate of P fertilizer application, form used, and method of placement are important factors that influence the crop utilization and yield response to added P. The objective of this thesis work was to assess the influence of P fertilizer application rate, form (mono ammonium phosphate versus struvite) and seed-row opener configuration (narrow versus wide opener spread and row spacing) on canola (B. napus hybrid var LL 252 & L 233P) under controlled environment and field conditions. In the controlled environment study, application of P fertilizer (MAP) at 20 kg P2O5 ha-1 significantly increased early (30 days after seeding) above ground biomass yield compared to the unfertilized control, while further rate increases produced no statistically significant yield increases. Struvite (ammonium magnesium phosphate) performed similar to the mono ammonium phosphate in crop yield response, fertilizer P uptake and recovery. The narrow seed-row opener spread (1”) gave better canola yield response and recovery of P from the two seed-row placed P fertilizers compared to the wide (3”) spread, which is attributed to greater localized concentration of P fertilizer in the narrow spread with concomitant reduced fixation in the soil. Canola emergence after 5 days was delayed with the high seed-row placed P fertilization rate of 60 kg P2O5 ha-1, but the differences among rates were not significant and the emergence recovered at day 10. In the field study, conducted in 2019 at five sites across SK and AB (Saskatoon, Brooks, Lethbridge, Melfort, and Scott) using mono ammonium phosphate as the P source, canola had significant positive biomass yield (above ground plant material at maturity) responses to P fertilization at most sites, with the greatest incremental yield increase associated with the addition of 22 kg P2O5/ha, with responses levelling off at higher rates. Across the sites, the canola biomass yield and P uptake was maximized at rates of 39 to 56 kg P2O5 ha-1. At Brooks, Scott and Lethbridge, significantly higher canola biomass yield and P uptake were observed using the highest seed bed utilization (44%) configuration, which was the combination of widest opener spread (4”) with narrowest (9”) row spacing. Limited and non-significant effects of seed bed utilization were observed at Saskatoon and Melfort sites. The benefit observed from having higher seed bed utilization at three of the five sites in the field study may be explained by greater early season root exploration of the soil volume associated with greater dispersion of seeds and fertilizer throughout the seed bed, with negative effects of greater opener spread that were observed in the controlled environment study not apparent under field conditions.