Citrus Drainage Management

Cindy Fake University of California Cooperative

Extension, Placer & Nevada CountiesApril 2012

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

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!

Orchard Floor Management Techniques• Mulch• Cover crops• Minimize cultivation - maintain

undisturbed root zone• Divide fertilizer

applications to optimize nutrient use

• Ensure good drainage

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

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

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!

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

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

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!

Citrus Drainage

Thank you!

Cindy Fake University of California Cooperative

Extension, Placer & Nevada CountiesApril 2012