Grain yields and water use efficiency tended to be higher when seeded into tall compared to short stubble and significantly lower when seeded into cultivated stubble.
In the semiarid Brown soil zone, improving the economics of growing canola requires adopting practices that promote more efficient use of water such as seeding into tall standing cereal stubble and seeding early to avoid heat and water stress during July and August. Deciding when a canola stand requires reseeding has been a perennial question in the Brown soil zone, and making this assessment is especially important for fall- or early-spring seeded canola.
Therefore, to determine the effect of seeding management, stubble management and population densities on the productivity of canola and mustard in the Brown soil zone, field experiments were conducted at Swift Current during 1998-1999, 1999-2000, and 2000-2001.
The main goals of this research were to:
1) compare yield and water use efficiencies of different canola and mustard species when seeded at different dates: late fall, early and late spring and of Argentine canola seeded into stubble of various heights: cultivated, short (15 cm high) and tall (>30 cm high) stubble.
2) to determine the relationship between suboptimal plant populations and yield to determine the conditions under which re-seeding becomes advantageous. The secondary objective was to evaluate the heat balance sap flow system for measuring the real time water use of canola under varying environments.
Generally, with adequate fertility and water, grain yields and water use efficiencies of fall seeded canola and mustard were similar to those for early spring-seeded canola and mustard and greater than those when seeded later in spring. As well, grain yields and water use efficiency tended to be higher when seeded into tall compared to short stubble and significantly lower when seeded into cultivated stubble. However, yield benefits were greater when canola in tall stubble was fertilized with an extra 34 Kg ha-1 N. Canola maintained seed yield over a wide range of populations. Seed yield declined with populations less than 40 plants/m2. On average, compared to early spring seeding, late spring seeding reduce canola yield by >30%; on average, when seeded in early spring, compared to optimum plant densities of 80 plants/m2, canola yields were reduced by 20% at a plant population of 20 plants/m2.
Therefore, 20 plants/m2 is a reasonable threshold population for re-seeding of early spring seeded canola in the semiarid prairie.