Timing and depth of post-harvest soil disturbance can reduce seedbank and volunteers of oilseed rape

Publikations-Art

Zeitschriftenbeitrag

Autoren

Shoubing Huang, Sabine Gruber, Wilhelm Claupein

Erscheinungsjahr

2018

Veröffentlicht in

Soil & Tillage Research

Band/Volume

175/

Seite (von - bis)

187-193

Appropriate timing of post-harvest tillage to oilseed rape (OSR, Brassica napus L.) is crucial for the creation of a
soil seed bank and unwanted OSR volunteers. Existing recommendations, however, can contrast with needs for
early post-harvest tillage e.g. for pest control. To specify and to systematically further improve preventive volunteer
management through post-harvest tillage of imidazolinone-tolerant oilseed rape (Clearfield®; CL OSR),
field experiments were set up at two locations in two separate trial periods at each location (2013–2014 and
2014–2015) in south-west Germany. After OSR harvest, and average harvest losses of 1500m−2 seeds, or artificially
broadcasting of 20 000 OSR seeds m−2, stubble tillage was performed at weekly intervals (immediate
(0), 1, 2, 3, and 4 weeks) at each of three depths (1–2, 6–8, and 15–17 cm). To depict a worst case scenario in
which herbicides were ineffective, no herbicides were applied. There were significantly smaller soil seed banks
found in spring the longer the period lasted between seed rain and stubble tillage; 265 vs 145 seeds m−2 referred
to 0 week vs. 4 weeks on average. Depth of stubble tillage had no significant effects on the seed number in the
soil. In the first spring after seed loss, 0–2.6 CL OSR volunteers m−2 were found in the winter wheat, and the
number decreased with delayed timing depth of stubble tillage. These volunteers mainly emerged in the
treatment of shallow stubble tillage (1–2 cm), with 0.7-0.9 flowering volunteer m−2, while volunteers averaged
less than 0.04 plants m−2 in the treatment “15–17 cm”. OSR volunteers in winter wheat got ripened only in one
out of the four fields, and produced 1.0 seed m−2 on average. The delay between harvest and stubble tillage can
be limited to approximately three weeks if stubble tillage is performed at a depth of about 6–8 cm; further delay
did not bring additional advantage. We recommend to retain the stubble for three weeks as further delay does
not bring additional advantage, and then to apply stubble tillage deeper than 6 cm. Very superficial or shallow
stubble tillage should be avoided. This procedure seems appropriate for avoiding oilseed rape volunteers without
use of herbicides.