Composted manure is animal manure, sometimes with straw bedding, shavings, or feed waste added, that has been aged or decomposed for some length of time and has a relatively stable nutrient content. Composted manure is a great option to apply to vineyards to add macro- and micro- nutrients to the soil, increase organic matter (OM) and to help build and maintain soil structure. As the organic nitrogen within composted manure is mineralized it is slowly available to the vines, supplying nitrogen in diminishing quantities to the soil over many years. Once compost is applied to the vineyard floor, its effects (good or bad) are difficult to undo. The effects of composted manure will remain in the soil and be evident in the vine for 5 to 7 years after the application. As a result, it is important to determine how to best use composted manure without causing long term problems.

Is composted manure a good option for your vineyard?

Applying composted manure to your vineyard will have minimal benefits if you have: vigorous grapevines, high organic matter (>5%), and petiole analysis showing sufficient N and only one or two limiting nutrients.  However, composted manure might be a good option in vineyards if:

• petiole analysis shows the need for N and other macronutrients,
• areas in the vineyard show signs of low vigour,
• areas in the vineyard show drought stress or leaf yellowing,
• areas in the vineyard suffer from soil compaction,
• the goal is to improve soil water holding capacity and infiltration rates,
• there is a desire to increase organic matter in vineyards.

In addition, it may be beneficial to apply composted manure to vineyard replant sites for pre-plant soil conditioning and to improve soil structure.

When is a good time to apply composted manure to grapes?

It’s best to apply composted manure in late fall or in the early spring (before bud break to pea-sized berries). Avoid applying composted manure from bunch closure to harvest; this timing may cause excessive growth, poor grape quality, reduced storability, and delayed cold-hardening of vine woody tissue, impacting winter acclimation. When applying prior to planting, composted manure should be incorporated into the soil to prevent nutrient losses from runoff, erosion or volatilization. In established vineyards, composted manure can be broadcast across the entire vineyard or band-applied under the vines and incorporated, if possible.

Don’t apply manure around newly planted vines, as it may result in vine injury.

Avoid spreading manure on frozen or snow-covered ground, and when there is a high potential for runoff, such as when the soil is wet or rain is predicted.

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