Weather risks: strategies to mitigate the risk of insufficient moisture
Information for apple and tender fruit growers to assess and mitigate damage caused by a lack of rain.
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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 factors.
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 storage.
- 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.
- Irrigation in Ontario
- Monitoring Soil Moisture to Improve Irrigation Decisions
- Irrigation Scheduling For Fruit Crops
- BMP 08 - Irrigation Management (Revised 2004)
- Drip Irrigation for High Density Orchards
- Low Water Conditions
- How to Prepare for Irrigation during water shortages
- Irrigating cherry orchards efficiently
- Effect of water on apple trees: not enough or too much
- Irrigation Equipment Suppliers (Partial List)