Soil Management Handbook - Ministry of Agriculture and Lands

The single most important soil factor that is beneficial
in conserving water is the addition or use of organic
matter as a soil amendment or mulch. Organic matter
improves soil structure and holds moisture. Mulches
allow rain or irrigation water to penetrate, but
prevents evaporation.
Water conservation techniques for agricultural water
users are as follows:
• Maintain irrigation systems to prevent leaks,
replace sprinklers or nozzles to reduce risk of loss
or over application.
• Use correct sprinklers, nozzles and pressure for
the designed system spacing.
• Keep filtration system clean.
• Irrigate only when required, based on soil
moisture conditions or crop needs rather than on a
schedule.
• Stop irrigation if rainfall exceeds 6 mm. Rule of
thumb is to stop for 1 day for every 6 mm over
the initial 6 mm, i.e., a 12 mm rainfall equals a 1
day stop.
• Ensure the system is designed for the soil and
crop requirements.
• Use trickle or drip irrigation systems as they
reduce water use by as much as 30% over a
sprinkler system.
• Use annual or permanent cover crops in perennial
crops.
• In the case of perennial crops, keep them pruned
to avoid excessive, non-productive shoot growth.
• Use mulches that allow water to enter the soil, but
reduce evaporation.
• Recycle or reuse water used for washing produce.
• Improve soil structure.
• Conserve crop residues at or near the soil surface.
• Prevent excess growth of cover crops or weeds.
• Use windbreaks or shelterbelts to reduce wind
velocity and evaporation.
3.3 Soil Management for Erosion Control
Soil erosion by water occurs whenever water fails to
percolate into the soil and begins to move across the
land as runoff. Erosion is greatest under high or
intense rainfall conditions or rapid snow melt on
frozen ground.
Erosion increases 1.5 times for every doubling of the
slope length, and increases 2.5 times for every
doubling of the slope percentage. Bare cultivated soil
is the most susceptible to erosion. Erosion decreases
as the density of the crop increases. Fields in
permanent grass or grass-legume mixtures are the
most resistant to erosion, and have the least soil loss.
Water erosion can also result from improper sprinkler
irrigation practices.
The general principles of soil management for water
erosion control are:
• Maintain a vegetative cover to protect the soil
from the impact of falling rain, to allow better
infiltration of water, and to reduce the velocity of
runoff water. Use cover crops and crop rotations
which include close-growing crops. Crop
residues should be left on fields over the rainy
months or periods of snow melt rather than
working the land.
• Maintain soil structure with large pores and good
internal drainage to permit more infiltration of
water. Avoid excessive tillage and compaction.
• Carry out tillage and seeding across the slope of
the land, preferably on the true contour, rather
than up-and-down the hill.
• Runoff water must be controlled rather than
allowing it to erode the soil. This may require
properly designed and located ditches, interceptor
drains or permanently grassed waterways.
The following guidelines for soil conservation
methods apply to upland soils with different degrees
of erosion hazard due to the steepness of slopes.
1. Low to Moderate Erosion Hazard (2 to 5%
Slopes)
Soils with slopes from 2 to 5% have low to moderate
erosion hazard, but soil loss may be excessive,
particularly if the slopes are long and approaching
5%. Surface runoff from adjacent land, should be
intercepted with a drainage structure. Either an open
ditch or a tile line backfilled with a porous medium
can be used. Areas on hillsides with shallow soils
overlying compact subsoils, or areas subject to
54 Soil Management Handbook – Okanagan-Similkameen Valleys