Weather risks: strategies to mitigate the risk of excessive moisture
Information on for apple and tender fruit growers to assess and mitigate damage caused by excessive rainfall or over-irrigation.
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This in the 6th in a series to help Apple apple and tender fruit growers in Ontario face many weather risks that can damage their trees and crops. It is important for growers to recognize the weather risks for their own location, and develop strategies to reduce or eliminate the impact on their business operation.
What it is
Excessive rainfall, over-irrigation or poor drainage can cause flooding, soil compaction and erosion in orchards. Excess moisture may increase the incidence of: root rots, splitting/cracking of fruit (eg. sweet cherries), diseases, winter injury, vegetative growth, soil compaction, nutrient deficiencies and tree mortality. Excessive moisture can also restrict root development resulting in decreased yields and plant vigour, and makinges the trees more vulnerable to tipping over due to high winds or heavy crop loads. Unmanaged water runoff can result in sediment loading into streams and open outlet drains having a negative impact on water quality.
When it occurs
Excessive moisture can occur anytime during the growing season. It is common to have excessive moisture in the late fall or in spring before budbreak, and luckily tree roots are most tolerant of flooded soils at this time. However, strong weather fronts, including thunderstorms or hurricanes can bring large downpours at any time. Sometimes, consequentive rainy days of small amounts of rainfall will keep the orchards wet enough to cause problems.
Where it occurs
Excessive moisture is one of the main weather risks for tree fruit growers. Excess moisture can have a negative impact on tree health, disease and susceptibility to winter injury.
What can you do
Some of these potential mitigation strategies may help reduce or eliminate damage due to winter injury:
- Production insurance (PI): Production insurance is purchased before the season, and can give you peace of mind that at least some of your input costs will be covered if your crop is reduced by insufficient moisture. Your premiums will depend on the coverage you choose, your claim history, and the yield potentials of your orchards. Over time, your premiums can be reduced if you are lucky enough not to have claims. However, some growers struggle with the premium costs (especially in their start-up years or if they have claims) and the fact that PI is not intended to fully cover your loss, either in yield or price. There is also the problem of reduced coverage levels in the years after your crop is reduced, due to the effect of the loss on your long-term average yields. Also, spot loss insurance is not available, so growers with multiple orchard sites may be penalized when good yields occur on the non-damaged sites.
- Site selection: Avoiding planting in low-lying areas or soils which may be prone to waterlogging. Areas that are poorly drained due to ponding, compact sub-soils, seepage from up slopes and high water table should be improved prior to planting, or avoided. If choice of site is limited to soils with one or more of these problems then attempts should be made to improve the soil prior to planting.
- Drainage: Surface and subsurface drainage can be used to manage water movement in vineyardsorchards. Install tile drainage in the orchard and check tile in older orchards to ensure they are working well. Heavier soils may need benefit froma French drains (channels of gravel from the surface to the tile drains) to improve drainage.
- Land preparation: Be aware of surface water flow and grade the orchard to manage water and prevent flooding. Heavier soils may need the application of gravel to improve drainage.
- Compaction and erosion: Traffic through the orchard with equipment under moist or wet soil conditions can cause soil structure problems such as compaction. After heavy rains allow soil to drain before driving through the orchard when possible. Where possible select light weight equipment, and reduce tire pressure to minimize compaction.
- Cover crops or orchard sod: Cover crops and sod row middles can help to absorb moisture throughout the growing season and may help trees or prepare for winter. They also prevent leaching losses by tying up nutrients in organic form over winter, and releasing the spring when the trees can use them.
- Efficient use of irrigation: Monitor soil moisture levels when irrigating to avoid excessive water use.
Managing water in orchards is an increasing challenge with changing weather patterns. Growers need to be prepared to deal with excess moisture to ensure tree growth and fruit development.