Nitrogen As A "Good Value" Feed Source In Autumn

Much work has been done in Western Victoria on responses to nitrogen over recent years. These responses will vary according to pasture composition, soil fertility and seasonal conditions, however it is possible to estimate within reason, the likely result of an application using the information available.

Is Extra Feed Needed?

This is the first question which needs to be answered.

What is the estimated feed requirement over the next 3 months and can nitrogen boosted pasture be included? Some herds will milk through autumn whereas the majority in the district are dry for most of April and May. Feed options for dry cows are:

  • Non nitrogen boosted pasture at home
  • Outpaddock pasture
  • Agistment
  • Hay or silage
Many farmers will plan to have a combination of most of these. If there is a shortfall, then nitrogen applied now may produce the best quality feed at the cheapest cost.

 

Example:
A typical well maintained pasture on reasonably fertile soils will have at least a 10:1 response to nitrogen.

 

Application Rate:
40kg N/hectare
(85kg per hectare Urea or 2/3 bag per acre of urea)

 

A 10:1 response will grow 40 x 10 = 400kg pasture at 10kg/hectare/day over 40 days

 

Estimated daily growth rate
  • Without nitrogen 20kg/day
  • With nitrogen 30kg/day
To build up a feed wedge of 600kg per hectare over the 40 days from 1400kg up to 2,000kg per hectare, some of the daily growth needs to be set aside.
Growth for Pasture Wedge:
15kg per hectare per day.
Growth left for consumption:
15kg/hec/day with nitrogen
5kg/hec/day without nitrogen
For farmers wishing to feed some green grass to dry cows, or milkers and build up a feed wedge, a typical autumn growth rate of 20kg/hec would hardly suffice.

A farm stocked at 2 cows per hectare would only have 5kg per hectare or 2.5kg per cow. If nitrogen is used this jumps up to 15kg per hectare or 7.5kg cow.

This is well over half of their daily requirements as dry cows.

What is the cost of Nitrogen Boosted Pasture?

At a 10:1 response, for each tonne of nitrogen applied, 10 tonnes of feed are grown.

1 tonne of nitrogen = 2.2 tonnes Urea.
2.2 tonnes of urea spread= 2.2 x $350= $770
1 tonne of feed = $77 (.64 c/MJ)

What are the advantages of Nitrogen Boosted Pasture?

  1. It allows the farmer to more easily build up a feed wedge approaching winter
  2. It provides the cheapest source of purchased feeds if seasonal conditions are adequate
  3. It is a high energy and protein feed
  4. There is no work involved to feed it out
  5. The benefits of good seasonal conditions and a favourable response to N will be reflected in increased body weight in dry cows and more milk in early calvers and a reduced cost per tonne of feed.
  6. It can potentially have minimal wastage when grazed compared with losses incurred feeding hay.
Following reasonable rains and an early start to autumn growth this year, pastures are already in a responsive state for nitrogen. An application of 40kg of N/hectare (85kg urea) in damp conditions is recommended.

 



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