Green Manure - UPDATE 18/9/2012

Spring time give us a chance to assess soil fertility by observing what is growing in the vineyard. One group of plants we are particularly interested in are called the "green manures." We think these are a great indication that soil organic carbon is improving.

These are the most common green manure plants we found growing on roadsides and in vineyards and orchards this season.

• Burr Medic – Ben South thinks this is Paragio pasture medic gone wild from paddocks.
• Snail & Barrel Medic – Escaped pasture grasses similar to Burr Medic but with different seed and different growth habits.
• Vetch – planted as a soil erosion control agent beginning in the 19C^th continuing to the 1980’s in sand mining operations on California Rd.
• Clover – Ben has had good success with Balansa clover as a covercrop, plus ‘wild’ white/strawberry/sub clovers have seen growing in old almond orchards replanted to vines near Willunga (both pictured below).

Clover in Willunga.

Balansa clover foreground and burr medic background

Green manure crops are so named because they add nutrients and organic matter to the soil. Green manure crops are also useful for weed control, erosion prevention, and reduction of insect pests and diseases.

In addition to the 'wild' green manure plants (burr, snail, barrel medic, clover and vetch) farmers have actively planted field peas and faba beans. All of these plant types all grow through winter and flourish in spring. They all fix nitrogen from the atmosphere and draw it into the soil.

Vetch -  

Grows well and persists for many seasons. It is able to self-sow. Vetch is growing well across all of McLaren Vale. Vetch seems to do well in wet winters which favour its lifecycle.

Vetch is relatively slow growing in winter but has prolific spring growth. It has been used to stop soil erosion in McLaren Vale for over 100 years. Now a natural population grows in vineyards - picture McLaren Vale.

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Beans and Peas- 

Beans and peas are generally planted by vineyard owners and orchardists. They are annual crops and don't persist for multiple seasons without resowing.

Field peas are a hardy winter legume that can provide good bulk and help with soil structure.
Picture - Seaview district sandy loam soil.

 

   

Medics - 

Many vineyards have good self-sustaining populations of medic. Wild burr medic is growing across many different soil types.

Burr medic is very common in the McLaren Vale region.

Burr Medic grows on a wide range of soils, but does best in alkaline soils. 
Grows most prolifically on heavy clays like this at Malpas Rd, Willunga.

Clover - 

Many vineyards have good self-sustaining populations of clover - it thrives on alkaline soil.

Sub clover growing in vineyard midrow at Clarendon.

In many areas, particularly on acidic soil, clover is short-lived because of a combination of insect pests, diseases and nutrient balance; this is known as "clover sickness".

DJ’s All-rounder Blend. The all-rounder blend has clover, medic and perennial grasses with the balansa clover dominating (over knee height) in the photos – planted this autumn with SOA and guano.  The grower will let this perennial sward go to seed this year to build the clover and grass seed bank.

In many situations clovers make an excellent seed mix inter-sown with other varieties.Vineyard ryegrass mixes were very popular in the 1990's and early 2000's. Many of these are persisting and the clover has survived to become self-generating.

 

What are you seeing? - 

This winter has been wet and favourable to crop growth. What are you seeing on your farm? Are you concerned about soil carbon and ground cover and if so do you have plans in place for next year? We are always interested to hear what is working for you.