Management of nitrogen and phosphorus fertilizer in no-till flax

Abstract

The major flax-growing areas of Canada coincide with areas where large shifts towards conservation tillage have occurred. These shifts have also brought about major changes in the way fertilizer is applied. The objective of this study was to determine the combination of nitrogen fertilizer form and N and P fertilizer placement methods that can increase N and P uptake, seed yield and seed oil concentration and composition in flax. The study was conducted at four locations covering the flax-growing areas over a 3-yr period. Three fertilizer forms, ammonium nitrate (AN), ammonium sulphate (AS) and urea were compared using different placement methods, pre-plant band (Pp) or side-band (Sb) in combination with monoammonium phosphate in either a Pp, Sb or seed-placed (Sp) position. Plant uptake of N and P was measured at 7, 14, 21 and 28 d after crop emergence and at the start of flowering. Other variables collected included crop establishment, crop yield and seed oil concentration and composition. AS resulted in the highest N uptake followed by AN then urea. As well, AS in the Sb showed higher N uptake than when applied Pp. The largest uptake of P was observed on days 7, 14 and 21 when AS and P were placed together in an Sb position. Crop establishment was adversely affected by urea and least by AN and AS, indicating that adequate seed-fertilizer separation between urea and flax seed is critical to minimizing reductions in plant stands. N form and placement, and P placement had no effect on seed oil concentration and composition in this study. Seed yield was improved marginally, overall, with the addition of P, while changes in N and P placement had no overall yield benefits. Treatments that resulted in improved N and P uptake in the first 21 d after crop emergence did not result in improved seed yields. When site x year interactions were investigated, 2 of 12 site years showed better yields when N and P were placed together in the Sb position. Based on the results of this study, we conclude that flax growers have many agronomically acceptable N and P management options available.