Green manures in orchards and vineyards

Green manures can be grown during the season or in the off-season in annual and perennial horticulture, such as:

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in orchards and plantations of temperate or tropical trees or shrubs (fruit, berries, coffee, nuts etc)
in vineyards of grapes, kiwifruit (Chinese gooseberry) etc
on farms growing annual and perennial medicinal or cooking herbs
in annual vegetables where they are often a key part of the operation as a whole
and in permanent plantings of vegetables and the like: asparagus, rhubarb etc.

In orchards in south-eastern Australia (winter-dominant rainfall), oats, barley or wheat are used as winter green manures. Oats often produces the best result followed by barley or cereal rye (ryecorn not ryegrass), then wheat. The result is better soil structure leading to a soil that is "softer and easier to work" according to one farmer on red clays that would set hard if he didn't grow the green manure or a permanent sod.

In Sunraysia (where NSW, Victoria and South Australia meet), some farmers grow oats, cereal rye, barley or wheat between rows of grapes. They can be sown any time from late summer (from January onwards) to suit the farmer, the season and the grape harvest.

Sowing them before harvest (any time from February onwards) can help to reduce compaction at harvest because the roots are more resilient than the soil and tend to push the soil back into shape once the machinery has moved on.

The cereal is slashed and thrown onto the vine rows to

give the vines a mulch to reduce weeds
reduce moisture loss from the soil surface
increase nutrient supply to the grapes and
protect the soil from the extreme summer heat.

The cereal is slashed several times during the spring to reduce the competition it would otherwise give the grapes and to suppress weeds in the grape rows. For repeated slashings, oats are generally best, again with barley the next best.

Because the cereal has a different feeding and rooting pattern and because it covers a different area to the grape, it gets nutrients from a greater area than the grape roots might get to. The cereal makes these nutrients available to the vines through increased biological activity in the grape roots zone.

There is no need to add fertilizer in the short term. This is because the green manure collects nutrients from the air and water and the increased biological activity unlocks nutrients from the soil and from past fertilizer applications. Longer term there may be a need to add fertilizer, but there doesn't seem to be generally unless the farmer is trying to push yield to an unsustainable level.

In tropical and subtropical orchards and banana plantations on the east coast of Australia, peanuts (ground nuts) are a common green manure and sometimes they are used year-round. They are slashed frequently and thrown onto the rows to reduce the competition they give to the crop, to suppress weeds in the rows and to allow easy access for machinery.

In perennial medicinal and cooking herbs, there are three main possibilities

GROW green manures in the off season all over the ground surface
KEEP a permanent rolling green manure under control with regular slashing and throwing or
MAINTAIN a low-growing green manure among taller herbs.

In permanent plantings of vegetables and the like: such as asparagus, rhubarb etc, the best method is likely to be growing a green manure in the off season and slashing it just before the season starts. Some farmers report success with poultry in asparagus including a side benefit - the poultry have reduced their problems with low-growing weeds.

Alfalfa (lucerne) has particular potential in an orchard where the vines or trees are prone to the soil disease phytophthora, such as passionfruit, macadamias, avocados and citrus. Lucerne mulch and well-made heat compost are two excellent additions to soil that has a phytophthora problem. Both help beat the disease while they improve the soil.

So one way to kick start the process is to grow lucerne between the rows of trees and to slash it frequently, throwing the slashings around the base of the plant. However, contact between organic matter and the trunk can lead to collar rots, so it is a tricky balance. Simple tree shields to ensure an air gap between organic matter and the trunk are a practical way to manage this.

These are some possibilities. Most farmers are inventive and develop a system that suits them specifically.

Over to you and please pass on to us your experiences if you think other farmers would benefit. Let us know what works for you and what you find doesn't work for you.

Related info:

Green manures

Choosing a green manure mix

Green manures under sweet corn or tomatoes

Squeezing a green manure in

Return a third to the soil

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This page was updated on December 27, 2007