Nitrogen loss from herbicide use

Rueben HaleThe West Australian

The Statewide use of herbicides is being blamed for the "vicious cycle" of declining nitrogen in soil.

Planfarm consultant and 10-year veteran of crop and pasture systems, Paul Omodei, warned farmers that legumes are growing but not fixing the nitrogen in the soil because of the heavy use of the herbicides in modern farming.

Mr Omodei spoke to a group of farmers about the importance of correcting the depleted PH levels at the Brookton Sheep Optimisation Workshop last week.

He said cereals or deep seed canola sewn in pastures could increase early season biomass, while taking pressure off other paddocks that may need to be manipulated.

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"If you manipulate out all the grasses in the pastures, that creates pressure on the stocking rates and the point is, to manipulate pasture you've got to think about paddocks in blocks," he said.

Mr Omodei said one way may be to sow cereals into pasture, or another to manipulate for grasses.

"What that means is by diversifying, then you take the pressure off winter stocking of pasture," he said.

Mr Omodei said farmers have to evaluate where arial seed cleaners fit into their system.

"This is for two reasons," he said. "First, they have a very hard seed that can sustain a cropping rotation.

"Second, they have a higher biomass product which allows more nitrogen for the soil."

Mr Omodei also said high pasture stocking rates for low cost feeds can be achieved by implementing an appropriate bedding system.

"This also allows for the other paddocks being manipulated ready for the next crops and turning off the lambs in spring," he said.

West Brookton grower and sheep farmer Allen Clarke said he could bolster his pasture quality and availability for summer sheep feed with a good pasture manipulation program.

"Good pasture quality and stocking rates has provided a relatively low cost feed source for my sheep," he said.

"We need to lift State lambing percentage by lifting our lambing numbers.

"The State lambing rate is around 78 to 80 per cent but it needs to be around 90 per cent to ensure sustainability and a low cost feed source for sheep can assist with that."

Mr Clarke said his system last year yielded an extra 100kg of pasture, per hectare, per day.

"This gave me an extra two tonne per hectare of extra quality dry matter to feed my stock," he said.

He also said manipulation removed unwanted competition.

"Then by inference, you are left with sub-clover or any other legume with moisture left to itself," Mr Clarke said.


·Use chaff carts.

·Allow sheep to put on weight in canola stubble.

·Cereal can be achieved in autumn because of winter vernalisation.

·Utilise a grain then graze program for your paddocks.

·Spread big and sew small or sew small spread big.

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