Irrigation Resources

Dry Soil Conditions Impact on Nutrient Availability

July 26, 2016 | ONfruit
by Deanna Nemeth, Horticulture Sustainability Specialist, OMAFRA

Although the past week brought some much needed rain, many locations in Ontario were experiencing prolonged dry soil conditions. These extended periods of very dry soil conditions can reduce Nitrogen (N), Phosphorus (P) and Potassium (K) availability to plants.  

For N, low soil moisture decreases soil microbe activity. Microbes play an important role in breaking down organic matter and converting organic N to inorganic nitrate nitrogen, a process called mineralization. In dry soils with low N mineralization, there could be less plant available N in the form of either ammonium (NH4+-N) or nitrate (NO3--N) nitrogen. In dry soils, the risk of NO3--N loss through leaching or denitrification is reduced. While this means there is more soil N available to crops, plant uptake can be reduced. When the rains return there a can be a sudden increase in soil nitrogen. If this occurs late in the season it may be detrimental for perennial crops going into dormancy.

Reduced soil microbial activity in soils with low moisture can reduced organic matter decomposition and the mineralization of organic P to inorganic P. Phosphorus moves from higher concentrations in the soil to lower concentrations in plant roots by diffusion. As soils become drier, less diffusion occurs. This is because the water film around the soil particles becomes thinner, making diffusion to the plant root more difficult.

Decreased movement of K to the plant roots occurs in dry soil. As soil dry, clay minerals become dry and shrink, trapping K tightly between mineral layers. Once trapped, K is unavailable to plant roots for uptake. This K is released and plant available again when the soil moisture increases. Reduce K uptake during extended dry soil conditions can show up as low K levels in tissue samples or high K levels in a post-harvest soil sample. Taking soil samples in a dry year and comparing it to normal years can provide valuable information to for what to expect if future dry years occur again.

Crop nutrient removal in dry conditions
Plant N, P and K uptake under extended periods of dry soil conditions may be less. As a consequence of this it is likely that nutrients applied from fertilizers and organic sources may still be available the following year.

Soil testing in the fall of 2016 is the best to estimate the remaining nutrients available for the next 2017 crop. In dry years, a recent soil sample is a better estimation for next year’s crop nutrition program than a sample that is older (e.g. more than 3 or 4 years old).

A fall soil test will help in accounting for nutrients carried over from 2016 to the 2017 crop.

Nutrients that could be carried over and should be credited from one year to the next include:

· Mobile nutrients like nitrate nitrogen, sulfate, and boron in the soil
· Immobile nutrients previously applied like phosphorus, potassium and zinc
· Nutrients in crop residues 

For more information, contact:
Deanna Németh, Horticulture Sustainability Specialist, OMAFRA
Christoph Kessel, Soil Fertility Specialist, Horticulture, OMAFRA 


1. Soil and Fertility Handbook. OMAFRA Publication 61, 2006
2. IPNI Plant Nutrition Today, W. M Stewart, No. 7, Fall 2012

Irrigation System Assessments

July 12, 2016 | ONfruit

by Rebecca Shortt, Engineer Water Quantity, Ontario Ministry of Agriculture, Food and Rural Affairs

Are you concerned that your irrigation system is not applying enough water? too much water? or applying unevenly?  To request an Irrigation System Assessment contact Rebecca Shortt OMAFRA Water Quantity Engineer 519-426-4920 (limited availability)

Australian research has shown that one of the greatest opportunities for irrigation water savings are in improving how evenly the water is spread across the field by the irrigation system.

Let’s say an irrigator goes out to apply one inch.  But across the field some areas are receiving 0.5” and others 1.5”.  Some areas are not receiving enough water leading to quality and yield impacts in certain portions of the field.  To compensate, the irrigator may consistently set out to apply 1.5” knowing that some areas will receive the necessary 1” but others will receive an entire 2”.  This is where the opportunities are for water and energy savings.

June 25, 2016 | ONfruit
by Rebecca Shortt, Engineer, Water Quantity, Ontario Ministry of Agriculture, Food and Rural Affairs

Irrigation Update

The month of May and the first 3 weeks of June have been extremely dry (<40% of avg rainfall).  The areas of Niagara and Peterborough are of particular concern because of lengthy dry conditions through the entire spring (since March 1st) and stretching back through 2015.
Read more

Grape Irrigation - Both art and science
It’s a delicate dance to get just the right amount of water on grape vines at this time of year.  Water is crucial for cell division and the rapid berry growth occurring.  However, too much water can cause too much vegetative growth.

What is deficit irrigation?
How to calculate the length of time to run my drip system each day?
How much water do I need to apply?
How long do I need to run my drip system?
Read more


Water Infiltration into Soil

Water Infiltration Into Soil Chart prepared by Donna Speranzini, Agriculture and Agri-Food Canada showing water infiltration, soil water holding capacity, and rate of flow through various soil types.

Ontario Weather Maps

Weather Innovations Network (WIN) has provided Youtube videos to provide a detailed look at Ontario rainfall (wet and dry periods) in 2013 compared to 2012.

GGO’s Soil Moisture Management for Quality in Vine Production publication

Grape-growing regions around the world routinely practice irrigation in their vineyards. Unlike many of these viticulture areas, however, Ontario is considered a cool-climate grape growing region. As such, vine water stress is not as prevalent. Learn how to properly manage soil moisture to maximize vine quality.

Contributors: Dr. Andrew Reynolds, CCOVI, Brock University; Rebecca Shortt and Kathryn Carter, Ontario Ministry of Agriculture and Food

Funding provided through Water Resource Adaptation and Management Initiative

Ontario Government Irrigation and Water Factsheets

Energy Conservation in Irrigation
Improving On-Farm Food Safety Through Good Irrigation Practices
Trickle Irrigation System Selection
Water Efficiency and Conservation Practices for Irrigation
Permit to Take Water
Permit to Take Water Consultants
Irrigation Equipment Suppliers