Activity 3 - Managing nitrogen when planting winter wheat on barley grain stubble
The major focus of this sub-activity was to determine if nitrogen management recommendations need to be altered when planting winter wheat into barley stubble. There is some concern that heavy trash left after barley is harvested could lead to N immobilization and cause deficiencies in winter wheat. This study was established at Brandon, and at locations in northern (Fahler) and southern (Lethbridge) Alberta in the fall of 2011.
Treatments consisted of a factorial combination of four N rates (0, 40, 80, 120 kg N ha-1) and six N application/straw treatments (urea banded at seeding, straw on surface; urea banded at seeding, straw removed; ESN banded at seeding, straw on surface; SuperU banded at seeding, straw on surface; UAN dribble band in spring, straw on surface; SuperU broadcast in spring, straw on surface).
N fertilizer rate increased most winter wheat responses, the exceptions being plant density, and kernel/test wt. Of more interest was N/straw management and interactions between the two N management responses. No significant interactions were evident between N fertilizer rate and N/straw treatment for any of the winter wheat responses. Nitrogen/straw management alone did impact some winter wheat responses.
Nitrogen/straw management did not affect plant density, grain quality, and N uptake responses. Midseason biomass yield at Lethbridge was greater when UAN was dribble banded in spring (with barley residue on soil surface) relative to when urea was banded at seeding (barley residue removed); biomass yield was intermediate for the remaining treatments (Table 3). Greenseeker assessments of winter wheat growth in May and June showed that NDVI was affected by N/straw treatment only for the initial three assessments at Brandon.
The consistent difference that emerged was that urea banded at seeding (residue removed) consistently resulted in an NDVI equivalent to or greater than other N/straw treatments (Table 3). At Brandon, grain yield was greater where urea was banded at seeding (residue removed) than where SuperU was spring broadcast (with residue applied in the spring) (Table 3). This followed the same general trend as NDVI values observed earlier in the season, suggesting that under the relatively dry conditions experienced in fall 2011 in Manitoba, urea banded at seeding (with residue removed) was more effective than spring broadcast SuperU (with residue applied in the spring) and as effective as the other N/straw treatments employed in this study.
The extent to which spring-application of straw may have impacted the plant available N supply in this treatment is unclear. No differences were evident between the spring broadcast SuperU treatment, and the remaining N/straw management treatments at Brandon, and for all treatments at Lethbridge.