Productivity and profitability of straw-tillage and nitrogen treatments on irrigation in southern Alberta

Abstract

Straw-tillage treatment and N fertilizer rate were assessed for their impact on plant growth, N uptake, and profitability of irrigated cereals and oilseeds on a Dark Brown Chernozemic Lethbridge loam in southern Alberta. Straw was either retained or removed by baling. Tillage treatments were fall plowing, spring plowing, and direct seeding. Four N fertilizer rates (0, 50, 100, and 200 kg ha-1) were imposed on the straw-tillage treatments. The data were analyzed by crop using analysis of covariance with year and replication as random factors, straw-tillage treatment as a fixed effect, and fertilizer and fertilizer squared as covariates. Grain and straw yields were higher for fall plowing than for spring plowing or direct seeding at zero N rate, but were not different at the high N rate (200 kg ha-1). Grain and straw N concentrations were higher for fall plowing than spring plowing or direct seeding at the low N rate (50 kg ha-1), but similar at the high N rate. Total N uptake was higher for fall plowing or spring plowing without retaining straw than direct seeding without retaining straw or spring plowing with retaining straw at the low N rate, but similar at the high N rate. Net returns were higher for fall plowing and treatments that sold the straw, and were maximized at a N rate of about 100 kg ha-1. Key words: Crop residue, fertilizer nitrogen, economics, tillage timing, irrigation