Direct-Drilling Pastures
When correctly applied, direct-drilling minimises soil loss, retains moisture, allows the strengthening of existing pastures and will maintain yields.
There are five main reasons why farmers should consider direct drilling:
- Soil conservation-Extensive studies have shown serious medium- and long-term effects on soil structure and soil losses through wind and water erosion.
- Moisture conservation-Disturbance of the soil by cultivation will result in accelerated soil moisture loss. Leaving the surface residues undisturbed will ensure the greatest possible moisture retention.
- Time conservation-In situations where seasonal extremes play an important role, the timeliness of pasture establishment is important. It involves only two passes (spraying and drilling) and has the potential to be carried out much more rapidly and with greater flexibility than full cultivation.
- Control of difficult weeds (eg Couch).
- Lower machinery capital.
Site Suitability
Direct drilling can be used with consistent success on almost any soil type providing some important criteria are fulfilled.
The machinery used plus the way they are set up and operated have a big influence in the end result. Direct drilling is not as reliable as conventional sowing techniques. More effort is needed to ensure the best possible job is done. If the inputs to ensure reliable results cannot be provided then the system should not be used.
Things to Consider
- Start with a paddock with good soil structure and drainage and use direct drilling to maintain it.
- Ensure that weed control is effective. A good spraying job using the correct chemical at the correct rate in the correct condition is essential.
- Identify and control pests. Pest damage is a major contributor to poor results obtained from direct-drilled crops, although the damage often goes undetected. Pests such as slugs, Argentine Stem Weevils, springtails and grass grub are all potential problems with direct-drilled crops, although all can be effectively controlled before or during drilling.
- Fertility levels should be checked by soil tests and/or fertiliser application records. Fertiliser should be sown with the seed, preferably separately placed, rather than broadcast. If rates are kept low (N < 30 kg/ha) an NPK fertiliser in the drill row helps seedling vigour and can kill slugs for the short term who try to live in the drill row.
- Best results are achieved when direct drilling from dry conditions to wet. Spring drilling tends to be less reliable if following conditions are dry.
Equipment
The equipment used and how it is used is crucial. There are large differences in performance between different direct-drilling openers and tines, particularly in dry soil conditions.
These differences increase as soil moisture becomes more limiting and are always in order of:
- V-shaped grooves worst.
- Inverted T-shaped grooves best.
- With U-shaped grooves intermediate.
Effective control of seeding depth is required. This is essential for clovers and herbs like chicory. Surface residues must be left over the seed zone for maximum moisture retention, but not pushed down into the slot. These are the responsibility of the operator to monitor.
Weed populations are very high after a drought. Unless you are direct-drilling fast-establishing species (which are not generally drought resistant), you should follow one of the three following choices
- Spray in the autumn following a break in a dry period. Drill in a winter feed crop. Spray again early spring and direct-drill in permanent pasture. This gives two weed control phases before drilling the slow establishing grasses.
- Spray in the spring and leave as a chemical fallow over the summer. Spray again early autumn and drill when moisture is good. Weeds striking in the spring and summer would be killed in the autumn.
- Sow fast establishing grasses. Sow into permanent pasture in two or so years. The faster species suppress the weeds and leave a cleaner sward to drill into.
In summary, consistently good results can only be achieved with direct-drilling by correctly using the appropriate chemicals (herbicides and pesticides), choosing a suitable site and using equipment that is tolerant of varying soil conditions (especially dry), handles surface disturbance, controls seeding depth effectively and places fertiliser. If any of these inputs are limited, you risk partial or complete failure of crop establishment.
Rob Eccles
Agronomist
Wrightson Research
Armidale NSW
Australia
Contact for Enquiries
Manager
North Island Regions
Sector Performance Policy
MAF Policy
Hamilton
NEW ZEALAND
Phone: +64 7 957 8313
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