Abstract

Studies were conducted to ascertain how flax (Linum usitatissimum) would be affected by large amounts of P applied initially for wheat (Triticum aestivum L.). A Zn ✕ P interaction was suspected.

The residual P from 100, 200, and 400 kg P/ha applied in 1965 to two Manitoba soils (orthic haplustolls) affected the yields of flax in 1971 and 1972. In 1972 the levels of NaHCO₃ extractable P in the surface soil ranged from 1.5 ppm where no fertilizer P was added to 46.5 ppm in the surface soil where 400 kg/ha of P was applied in 1965. The higher levels of P in the soil increased the P concentration in the plants, but the Zn and Cu concentrations were depressed to near critical levels in some cases. Field applications of Zn and Cu fertilizer did not increase flax seed yields.

In the growth chamber, increases in the levels of NaHCO₃ extractable P in the soil increased the shoot and root yields, decreased fertilizer P uptake, and decreased Zn and Cu concentrations. Applications of fresh fertilizer P increased yields and further increases were obtained with P-Zn-Cu combinations. Concentrations of N, P, and K were similar in both the roots and shoots, but concentrations of Fe, Zn, and Cu were 25, 2, and 2 times greater, respectively, in the roots than in the shoots. Conversely, Mn concentrations were twice as great in the shoots as in the roots.

Flax crops grown on calcareous soils in Manitoba should be monitored for Zn deficiencies when NaHCO₃ extractable P in the surface soil exceeds 20 ppm.

Copyright © . .