A POTENTIAL problem looms.
With the winter crop harvested or nearing completion, attention now should turn to controlling weeds that have emerged in the stubble or are waiting to germinate when soil temperatures are high enough.
There will almost certainly be enough soil moisture available to encourage them.
Uncontrolled heavy weed growth during the summer fallow period can reduce the yield of the next crop by robbing those crops of available soil nitrogen; depleting the soil of stored moisture and reducing crop emergence due to the physical and/or chemical (allelopathic) interference at seeding time.
Controlling summer weeds early will conserve valuable soil nitrogen and moisture for use by the crop during the following season.
Growers have gained an average farm crop yield increase of up to 400 kilograms per hectare with consistent summer weed control.
If left uncontrolled, weed burdens of 2.5 tonnes per hectare can cause a loss of available soil nitrogen and burdens of more than 3t/ha can reduce following wheat yields by as much as 40pc.
Chemical control of summer weeds
Growers using zero-till or conservation tillage practices commonly treat emerging weeds with chemicals.
Chemical control of weeds is also common in conventional tillage systems.
Summer weed control can be expensive but is necessary to prevent problems with excessive growth and/or moisture and nitrogen loss from the soil.
Moisture stress in weeds is common in summer and reduces the effectiveness of most herbicides.
This can be partially overcome by spraying early in the morning.
However at this time of day, inversions may be present which could lead to excessive drift.
Avoid spraying during still conditions.
Monitor for problem weeds
There are a number of weeds that are likely to present challenges over the coming summer period.
The challenges are in the fact that some of these weeds are spreading through cropping districts to a greater extent, and second, most seriously, some are showing resistance to herbicides.
The weed species likely to cause problems this summer in the major cropping districts are Feather Top Rhodes grass, melons, wire weed, and fleabane.
Integrated management the key
Many weeds are now showing resistance to commonly used herbicides.
To deal with this problem, an integrated management approach should be adopted.
This involves having a number of tools in your spraying and cultivation arsenal that you can use as the occasion and weed species demands.
The Department of Primary Industries and Regional Development and advisory agencies can provide detailed advice on just how each of the resistant weeds should be dealt with.
In most cases, an important tool in an integrated management approach is strategic tillage.
Choosing an implement that enables chopping and burying of mature weed plants before seed set, and/or burying weed seed to depths that hinder germination are features that you should look for in a tillage implement.
Two implements that effectively deal with a summer weed problem and also handle carryover stubble are the Speedtiller by K-Line Ag and its smaller brother, the K-Line Ag Flexi-Mulch.
The Speedtiller is a high-performing, high speed dual purpose disc-tillage machine that will efficiently cut, size and incorporate high levels of mature or emerging weeds as well as crop residue.
Both have the flexibility and adjustments to suit most trash burdens and soil conditions.
Soil erosion from wind and water is drastically reduced by the excellent incorporation ability of these implements.
The Speedtiller from K-Line Ag is available in sizes ranging from 1.8 metres right up to the massive 15.5m Powerflex model.
Suitable for tractors from 80 horsepower up to 650hp, there's a combination to suit any operation.
Then there's the Flexi-Mulch, designed specifically for multipurpose use in mid-sized farming operations with 70hp to 125hp, three-point linkage tractors.
Both the Speedtiller and FlexiMulch machines are fitted with a crumbler roller that leaves the soil with an even, level tilth, ready for sowing the next crop.
