Weather Risks: Strategies
to Mitigate the Risk of Insufficient Moisture
Table of Contents
- Impact of dry weather on fruit trees
- When it occurs?
- Where it occurs?
- What can you do?
- For more information
It is important for tree fruit growers to recognize the weather
risks for their own location, and develop strategies to reduce
or eliminate the impact on their business operation.
Insufficient moisture is one of the main weather risks for tree
fruit growers. Access to water during important physiological
stages of tree and fruit growth is required for optimal performance
of fruit crops. Shortage of moisture during critical periods of
crop growth and fruit development affects both yields and sizing
of produce, affecting the volume of production and average price
of fruit. The trend to plant high density orchards has intensified
this effect with growers planting dwarfing rootstocks with shallower
roots. With erratic weather patterns increasing, availability
of water is becoming more critical for growing quality fruit.
Impact of dry weather on fruit trees
Fruit trees need water to grow, maintain tree health, and produce
quality fruit. Insufficient moisture can cause: reduced growth,
shoot dieback, reduction in fruit size and weight (now and next
year), reduced tree survival and development (young trees), negative
impacts on fruit quality, reduction in fruit bud production (and
crops in subsequent years), nutrient deficiencies, increased winter
injury, increase in biennial bearing, and increase in physiological
disorders (bitter pit). Access to water can keep trees growing
through drought periods and increase their resistance to stress
When it occurs?
Insufficient moisture can occur anytime during the growing season
when the tree needs moisture. Critical periods for moisture include
bloom, seed set, fruit sizing (especially during cell division in
the first few weeks after bloom), fruit bud initiation, fruit ripening
and tree hardening. An online tool to track the amount of precipitation
your region has received are the Agriculture
and Agri-Food Canada Agroclimate maps. Information on determining
irrigation needs for fruit crops in Ontario in your orchard can
be found in the OMAFRA factsheet, Monitoring
Soil Moisture to Improve Irrigation Decisions. Information on
the use of irrigation
in agriculture can be found on the OMAFRA website. There are
also two ONFruit blog
posts by Rebecca Shortt, Engineer, Water Quantity, OMAFRA, posted
during the dry year of 2016 titled Irrigation
Update and How
Long do I Run my Drip Lines.
Where it occurs?
Dry conditions can occur in orchards across Ontario, but the effects
are worse on sandier soils with low-water holding capacity (eg.
low organic matter). Hot temperatures will exacerbate the problem
due to increased evapotranspiration losses from the trees. Peaches
and nectarines are more vulnerable to insufficient moisture, as
are trees on dwarfing rootstock that have limited rooting area (eg.
apples on M9 size rootstock, sweet cherries on Gisela). Intensive
orchard systems with trees planted at higher densities have competition
between trees and will need supplemental water.
What can you do?
Some of these potential mitigation strategies may help reduce or
eliminate damage due to insufficient moisture:
- Production insurance (PI):
is designed to cover low yields and/or quality losses caused by
adverse weather, disease, wildlife and insect infestation. Plans
are available for over 100 commodities. For most plans, coverage
is available on a yield basis. For yield-based plans, producers
receive a payment after harvest when an insured peril causes their
yield to fall below their guaranteed level of production.
PI is funded by federal and provincial governments. The federal
and provincial governments pay up to 60 per cent of the premium
cost and 100 per cent of the cost of delivering the program.
For more details on Production Insurance and other business risk
management programs such as AgriStability and Self Directed Risk
Management Program, including how to enrol visit Agricorp.com/programs.
- Supplemental irrigation:
When properly applied, both trickle and overhead irrigation will
reduce tree stress, increase fruit size, quality and yields. Trickle
irrigation is more expensive to install and is best installed
when the orchard is planted, but is easier to use when needed.
It can also be used to fertigate. Drip irrigation also minimizes
the risk of food borne illness caused by contaminated irrigation
water, as the water doesn't come in contact with the crop. Overhead
systems require extra labour to move equipment, and work best
if permanent header systems are installed for easy access to water.
Overhead systems also allow growers to apply more water in a single
application. Trickle irrigation is also more efficient in water
use than overhead irrigation which loses more water through evaporation.
A Permit to Take Water is needed if more than 50 000 L/day are
used per day, as well as a dependable water source that should
be monitored for quality. There are maintenance costs and costs
of water to consider.
- Under-tree mulch: These
mulches can have the same result as irrigation, because they conserve
soil moisture, cool the rooting zone, and improve fruit size,
quality and yield. Mulches can provide nutrients, add organic
matter and may host beneficial insects, but are also attractive
to rodents. Mulch materials may be expensive, not easy to source,
and likely need re-application over time. In some cases, they
may encourage late growth of trees which could result from winter
injury because of delayed hardening off.
- Add soil organic matter before planting:
Adding manure, compost, cover crops, straw, mulch or
any organic matter before planting will increase the water-holding
capacity of your soil. There is a cost to either purchasing materials
or growing it as a cover crop, but it can improve tree growth,
provide nutrients for the tree, and add resilience in the event
of a dry season.
- Build additional water storage:
Structures to store water available in the off-season may be expensive,
but well worth it in critical dry summers. A well-designed structure
is needed, and access for livestock and the public should be restricted
to ensure safety. Be sure your insurance company is aware of your
- Reducing competition from weeds and cover crops:
Maintaining a vegetation-free strip down the planting row or around
the base of individual fruit trees will help conserve soil moisture.
Weeds will compete with trees for soil moisture, so weed control
is especially important during droughty periods.
- Crop load management: Research has shown that
the severity of water stress is dependent on crop load. Peach
trees with heavier fruit loads are more vulnerable to water stress
than those with less fruit. As a result in orchards with high
levels of drought stress and no access to water, fruit thinning
can help to mitigate the adverse long term effects of water stress
on growth and can benefit fruit growth.
- Summer pruning: Summer pruning can help reduce
water stress on trees but has minimal impact on fruit size.
- Foliar fertilizers: There has been little
research done to support the effectiveness of using foliar nutrients
to alleviate dry weather symptoms in fruit trees. The permeability
of the leaf cuticle to mineral nutrients is greatly affected by
relative humidity (RH). Under conditions of low RH, less than
80%, cuticle permeability is low resulting in reduced uptake of
foliar nutrients. As RH increases above 80%, permeability increases.
However, at high RH the foliar product being applied can dry too
quickly, reducing uptake through the cuticle. During times of
prolonged heat stress, the cuticle gets thicker, making it more
difficult for nutrients to move through it. Drought stressed trees
can also close their stomata, reducing the ability of the foliar
nutrients to enter the trees. As a result drought conditions may
reduce the trees ability to uptake foliar nutrients, minimizing
their benefits. Avoid applying foliar nutrients in high heat,
as it can result in leaf damage (salts concentrating too quickly).
Foliar nutrients are unlikely to alleviate heat stress-only a
good rain will.
Growing quality fruit in today's intensive plantings is an increasing
challenge with changing weather patterns, increasing evapotranspiration
in summer's heat, and reduced rainfall. Growers need to ensure that
water is available during critical periods in tree growth and fruit
development. Access to water has become more important in producing
high volumes of high quality fruit for today's markets.
For more information
For more information:
Toll Free: 1-877-424-1300