This GRDC podcast provides some insights about research by Helen Burns and Dr Mark Norton from NSW DPI about acidic soils and the negative impact on pulse and legume yields
Timing nutrient application and rotation for best results
At BioAg, we recommend that – based on soil analysis – a lime, BioAgPhos and gypsum blend is broadcast onto cropping soils, prior to incorporation and in front of canola in the rotation. Most mixed farmers will bring a paddock out of a lucerne or clover-based pasture phase and use canola as the first crop in the rotation.
While in the pasture phase, most paddocks tend not to be topdressed, with farmers relying on the cropping phase to raise deficient nutrient levels.
Soils entering this cropping phase often possess a large soil bank of organic nitrogen. At the same time, they are usually deficient in calcium, phosphorus, sulphur and trace elements, particularly zinc and copper.
When soils are acid at depth you’ll find iron, manganese and aluminium levels elevated. This makes the soil toxic to acid-sensitive plants like pulses. These metals are also very antagonistic to important plant nutrients, particularly phosphorus.
Which nutrients to apply for soils that are acid at depth
Consider a prescribed blend containing:
- lime (provides calcium and removes acidity)
- BioAgPhos (provides similar levels of calcium to lime, phosphorus in a form that is resistant to locking up with these toxic metals caused by acidity)
- gypsum (provides calcium and sulphate sulphur inexpensively).
This mix, incorporated through the soil will provide relief from soil acidity, suppression of toxic metals, capital rates of Ca, P and S and will also reduce dependence on more expensive acidifying water-soluble starter P and S products at planting.
A typical blend for top dressing and incorporation might be: 1-2 tonnes/ha lime + 200-300 kg/ha BioAgPhos + 150 – 300 kg/ha gypsum.
Micronutrients can be supplied in a starter fertiliser blend and sown alongside or below seed. Alternatively they are easily applied in liquid form, ideally furrow injected or by boom spray at around sowing. They can be foliar applied at much lower rates to feed the plant but this will not address underlying soil deficiencies.
This lime blend applied and incorporated prior to canola helps with the preparation of a good seedbed for sowing canola into. Generally, canola is followed by wheat and then a pulse or barley. So several years after the application and incorporation, it’s time to grow a pulse. Pulses have a number of agronomic benefits including weed management, disease breaks and more. The residual nitrogen that they leave behind generally supports a good cereal crop to follow.
Acid soil? Talk to us for expert advice
Talk to one of our trained and certified regional managers for sound advice about soil fertility – in any kind of soil
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