This document discusses the importance of drainage management for citrus orchards. It notes that citrus trees have shallow roots within the top 30 cm of soil and a small root zone. Saturated, wet soil prevents the roots from getting enough oxygen and nutrients, and can cause root death within 1-2 weeks. To improve drainage, the document recommends digging shallow drainage ditches across slopes at 15-30 m intervals in heavy clay soils, protecting ditches with gravel, and allowing vegetation growth to slow runoff. Improving drainage in heavy soils can increase tree health and root mass, leading to higher yields and fruit quality. The overall goal is to maintain a healthy root system for healthy citrus trees.

1. Citrus Drainage Management
Cindy Fake
University of California Cooperative Extension,
Placer & Nevada Counties
April 2012

2. Importance of Orchard Floor Management
• Citrus have shallow roots, most
in top 30 cm of soil
• Small root zone to exploit
• Manage soil to provide good
root/soil environment
• Not just nutrient management,
but soil management
• Feed the soil to feed the tree!

3. Agenda
• Orchard floor techniques
• Mandarin root structure
• Improving drainage
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4. Importance of Orchard Floor Management
• Citrus have shallow roots, most
in top 30 cm of soil
• Small root zone to exploit
• Manage soil to provide good
root/soil environment
• Not just nutrient management,
but soil management
• Feed the soil to feed the tree!

5. Orchard Floor Management Techniques
• Mulch
• Cover crops
• Minimize cultivation - maintain undisturbed
root zone
• Divide fertilizer
applications to optimize
nutrient use
• Ensure good drainage

6. Mandarin Root Structure
• Typically no tap root
• Woody lateral roots radiating
from the trunk
• Fibrous feeder roots grow from
woody roots
• Feeder roots absorb nutrients and
water
• Most roots in top 30 cm, under tree
canopy
• 3 root growth flushes: early spring,
early summer and late summer

7. Mandarin Roots in Saturated Soil
• Citrus root growth starts ±12ºC
• Roots do not function in saturated (very wet) soil
• Citrus roots need oxygen and water
• In wet soil, tree roots cannot “breathe”
• Absorbing roots start to die
within 1 to 2 weeks
• Major root loss =>
yellowing leaves, then leaf drop
• Worse in hot weather

8. In Chronically Saturated Soils…
• Fibrous roots grow on the soil surface
• Not enough oxygen is
available in the soil
• Roots have plenty of water,
but cannot get nutrients
from soil
• These roots should not be
removed, they may be the ONLY functioning roots
• Improve drainage!

9. Improving Drainage
• Dig shallow drainage ditches
across the slope for runoff
• 1-2º downward slope
• 15 m intervals in heavy clay soil
• 30-60 cm deep, V shaped
• Top width 2+ m
• Bottom 1-1.5 m
Use A-frame level
to determine slope

10. Improving Drainage
• Protect drainage ditches with gravel or stones to
prevent erosion
• Allow vegetation to grow in ditches
to slow runoff
• Or install drainage pipe

11. Other problems with Saturated Soil…
• Increases Phytophthora root disease
• Disease damages roots, decreases
productivity
• Toxic levels of gases e.g. hydrogen
sulfide (H2S) collect in wet soil
• Improving drainage in heavy soils
=> improve tree health & root mass
=> increased yields & fruit quality
Goal is healthy roots
for a healthy tree!

12. Citrus Drainage
Thank you!
Cindy Fake
University of California Cooperative Extension,
Placer & Nevada Counties
April 2012