Background
Continuous and sufficient boron (B) supply is essential for achieving maximum yield in Brassica napus. Increasing incidences of environmental water limitation are linked to reduced plant B availability and increased B deficiencies. Developing an optimized fertilization strategy that considers the release speed of different B fertilizers is crucial to prevent B-deficiency during flowering.
Aims
Evaluation of different B species’ ability to sustain growth and fertility of B. napus during flowering under single and combined B-deficiency and water-limitation stresses.
Methods
The effects of highly soluble/fast-release (boric acid, borax) and slow-release (colemanite, ulexite, zinc borate) B species on plant phenotype and B status was investigated before and during flowering on B-sufficient and severe and moderate B-deficient conditions with varying water availabilities.
Results
Under B-deficiency, plant performance when supplied with the different B species decreased in the following order: borax > boric acid > ulexite > colemanite or zinc borate. Under well-watered and severe and moderate B-deficient conditions, borax application led to higher shoot dry weight, shoot B content, and more asymptomatic flowers than the other B species, on water-limited conditions only under moderate B-deficiency. Independent of B species, root length correlated positively with shoot B content, and shoot head B concentration before flowering correlated positively with the number of asymptomatic flowers.
Conclusions
In B-deficient conditions, floral performance of B. napus is driven by the B species supplied and the soil water status. Fast-release fertilizers, and particularly borax performed best in both well-watered and water-limited treatments, likely due to more continuous availability.