Foliar fertilization is a potential strategy to supplement P requirements when conditions permit. In 2016 and 2017, canola, pea and wheat were grown in a randomized complete block design trial near Pilger, Saskatchewan, Canada, along with a completely randomized design controlled environment experiment that was conducted with the same soil in the winter of 2016. Each crop received a total P application of 20 kg P2O5 ha-1, with varying proportions of the P applied as seed placed monoammonium phosphate (MAP) supplemented with foliar KH2PO4 (0, 25, 50, and 100%) applied prior to anthesis. Under both field and controlled environment conditions, yield response decreased as the proportion of seed placed MAP decreased. The 100% foliar applied P treatment in canola was able to maintain significantly higher yield than the unfertilized control in the absence of seed-placed MAP, indicating some uptake and response. Of the crops evaluated, canola was most responsive to P fertilization. Phytate content ranged from 68 to over 90% of total seed P, with the highest proportions found in wheat grain and with limited effect of foliar P application on phytate content observed. Fertilizer treatment had had little effect on grain Fe content but there appeared to be an inverse relationship between seed-placed MAP and grain Zn concentration that was less evident when P was applied in foliar form. In this study, foliar P application was unable to substitute for seed-placed MAP, and overall had marginal effect on grain yield and P uptake as well as seed nutritional value.

Placement strategies for P fertilizer can affect P availability to crops and influence the amounts and forms of P removed from soil in runoff, contributing to eutrophication. On the Canadian prairies, most runoff occurs during snowmelt. Two adjacent farm fields in Saskatchewan, Canada, were used to assess the effects of spring P fertilizer placement on crop P uptake, residual soil P, and potential P export in simulated snowmelt. One was in conventional tillage (CT) with no history of P fertilization, and the other was in a no‐till (NT) system with multiyear P fertilization at recommended rates. Fertilization (monoammonium phosphate) treatments were no P fertilizer (control); seed placed, deep banded, and broadcast and incorporated at 20 kg P2O5 ha−1; and broadcast treatments at 20, 40, and 80 kg P2O5 ha−1. Yield and P uptake were not affected by placement method. Water‐extractable P at the soil surface after harvest was unaffected by placement or rate at either site but increased below the 5‐cm depth at the NT site in 2016. Broadcast treatments increased P in runoff relative to in‐soil P placement for the 20‐ and 80‐kg P2O5 ha−1 treatments at the CT site and for the 80‐kg P2O5 ha−1 treatment at the NT site. Thus, in‐soil application of P fertilizer appears to be an effective strategy to reduce the risk of P export in snowmelt runoff. Core Ideas In‐soil fertilizer placement reduced P loss in snowmelt runoff from cropland. Broadcasting P fertilizer increased P loss in snowmelt runoff. Crop yield and P uptake were not affected by fertilizer placement method. Soil P was largely unaffected by placement over the 1 or 2 yr of the study.