Response of pea to rate and placement of triple superphosphate fertilizer in Alberta

The expansion of the pea acreage on the Canadian prairies has increased the need for more information on P fertilizer response by pea to both rate and method of placement. To determine responsiveness, 52 field trials using tr iple superphosphate (TSP) were conducted from 1995 to 1998 over a wide rang e of soil types across Alberta. Five rates of 0, 6.5, 13.1, 19.6 and 26.2 k g P ha(-1) were placed with the seed or in bands applied prior to seeding. The application of TSP significantly (P < 0.1) increased pea seed yield at 19 of 52 sites. The average increase in seed yield due to TSP application w as 7%, with values ranging from -12 to +33% across all trials. The average yield benefit was similar in the Thin Black, Black and Gray soil zones, but was negligible in the Dark Brown soil zone and in irrigated trials. Of the 31 trials with soil test P (modified Kelowna method) levels of less than 3 0 kg P ha(-1) to 15 cm, 52% had a significant yield increase due to applica tion of TSP, while only one of 17 trials with soil test P levels of more th an 30 kg P ha(-1) had a significant yield increase. Application of 13.1 kg P ha(-1) was sufficient to attain close to maximum yields in trials with so il test P levels of less than 30 kg P ha(-1). The yield response of pea was insensitive to TSP placement. The mineral impact of seed placement on yiel d in this study was likely due to the less damaging effects of seedling gro wth of TSP than of the more commonly used source of P, monoammonium phospha te (MAP). Seed protein and P concentrations were not strongly affected by T SP application.