Phosphorus sources for winter oilseed rape (Brassica napus L.) during reproductive growth – magnesium sulfate management impact on P use efficiency

ABSTRACT

It has been assumed that phosphorus (P) resources accumulated in vegetative tissues of winter oilseed rape (WOSR) at flowering are too low to cover the requirements for the high-yielding crop during the seed filling period (SFP). The data used originated from field experiments with nutrients sequentially added to WOSR, using crops grown on soil rich in available P (2008–2010). The low-seed density canopies during SFP resulted only from the P remobilized from the pre-flowering crop resources. The high-seed density canopies depended on both P remobilized and its uptake from soil (PFPU). The maximum PFPU of 30.7 kg P ha⁻¹, and the concomitant seed density of 86.8 ∙ 10³ m⁻², resulted in a maximum seed yield of 5.8 t ha⁻¹. Internal P resources were reused during SFP irrespective of the initial P content and without impact on phosphorus use efficiency (PUE). The study showed that PUE improvement in WOSR is related to the seed density of primary branches. Its development depended on the supply of potassium, magnesium and sulfate. A PUE of 105.4 kg seed kg⁻¹ P was used to predict the seed yield gap (PYG). This index can be used as a measure of P management efficiency in WOSR canopy.

KEYWORDS:

• Seed filling period
• phosphorus
• remobilization
• acquisition
• seed density

Acknowledgments

This study was partly supported by Kali & Salz GmbH, Germany.

Disclosure statement

No potential conflict of interest was reported by the authors.