Harvest Weed Seed Tour – Review

By Kate Coffey, Riverine Plains Inc

A local Harvest Weed Seed Management tour was held on the 24th January.  The tour involved looking at three different options for harvest weed control and followed on well from what was learnt on the Western Australia study tour two years ago.

The day’s discussions showed many farmers have already adopted practices such as spray topping cereals and spraying behind canola windrows. However, the difficulties encountered last year with weed control in wet conditions has focussed attention on the need to also do something at harvest.

The techniques that were viewed and discussed on the day included:

  • Separating chaff and straw, dropping chaff on top of the straw and baling (Trevethan Farms, Corowa).
  • Collecting the chaff in a cart towed behind the header (Wayne and Curt Severin, Brocklesby).
  • Adding a ready-made chaff deck  to the header to separate the chaff from straw, placing it in the wheel tracks (Chris Blomeley, Mulwala).

Visit 1  to the Trevethan family property saw Ian describe their header modifications (done this year with the assistance of engineers) in order to separate the chaff and straw. This involved changing the spinners and adding chutes and funnels so that the chaff could be dropped on top of a narrow windrow of straw.  The straw is  baled as soon as possible after harvest to ensure that as many weeds as possible can be removed from the paddock.

NOTE: The efficiency of this method will be analysed in a GRDC funded Harvest Weed Seed Control for the Southern Region demonstration site.  The site will compare the efficiency of the “chaff dropped on top of narrow windrow and baled” method, versus a more traditional narrow windrow burn as well as a blanket burn.

Visit 2 was to the Severin family, who have used a chaff cart for many years.  Curt has recently built a new cart, with several design improvements. The cart is towed behind the header and works by blowing the chaff  onto a conveyer belt, which feeds in to the top of the cart.  A camera in the header shows when the cart is full (or near to), so the cart can be emptied in the headland while turning without stopping.  The chaff is dumped in the paddock every few runs.

One of the problems with this method has been removing the “chaff dumps”, which was previously done by burning. The dumps can take a long time to burn but breaking them up with a loader can help them burn more quickly.  The preferred  option is to bale the chaff, or to fence off the chaff dumps and strip graze with stock.  Canola chaff in particular is quite popular as a livestock feed.

Visit 3 was to the Blomeley family who built and trialled a “chaff deck” in 2012.  The deck separated out the chaff and placed it in the wheel tracks.  Once the weed seeds germinate the following year, weeds are controlled in the tracks using a shielded sprayer.

The chaff deck was abandoned due to design problems, which caused blockages where there were high residues.  In the future, Chris will use rotational crops (such as hay and faba beans) for weed control and investigate a prefabricated chaff deck, when he purchases a new header.

Summary: The day featured three different methods of managing weed seeds at harvest, all with the ultimate goal of reducing paddock weed seed numbers.  Each method had its pros and cons, and as one farmer said “it doesn’t matter what weed seed collection/destruction system you are using, as long as it is causing a reduction in the weed numbers over time”.

Thanks to all our farmer hosts and organisers.

View A short clip of Ian Trevethan’s header in action. The header has been modified to separate the chaff and drop it in a narrow windrow. 

View a short clip of Curt Severin’s chaff cart in action.