Managing risks to waterlogged crops

Floods and high rainfall present a number of potential problems for tree and vegetable crops. Dealing with these issues quickly will maximise your chances of maintaining healthy crops.

Loss of oxygen

Waterlogged soils are deficient in oxygen because the oxygen between soil particles is replaced by water. Oxygen is essential for healthy root growth, and insufficient oxygen in soils over time causes cell, root and eventually plant death.

Drain waterlogged soils as quickly as possible, and cultivate between rows to aerate the soil. Learn more about improving drainage of crop land.

Heat from stagnant water

Stagnant water, particularly if it is shallow, can heat up in hot sunny weather and kill plants in a few hours. Remove excess water as soon as possible after flooding to give plants the best chance of survival.

Chemical and biological contaminants

Floodwater may carry contaminants, particularly from off-farm run-off. You should discard all fruit and vegetables exposed to off-farm run-off, particularly leafy vegetable crops.

Make sure you take food safety precautions and test soils before replanting, even if crops look healthy. Contaminants will reduce over time with follow-up rainfall and sunny weather.

Increased breakdown of fruit and vegetables

Fruit and vegetables affected by floods and high rainfall are at risk before and after harvest - particularly underground crops such as potatoes or sweet potatoes. Drain waterlogged soils as soon as possible, and carefully check the quality of produce.

Iron chlorosis or nitrogen deficiency

Floods and high rainfall can leach essential nutrients from the soil, which can affect plant health. Nutrients such as nitrogen, potassium, iron and boron can be replaced through the use of fertiliser.

Learn more about fertiliser replacement after leaching of nutrients.

Soils with high clay content

High clay content means soils can become compacted and form a surface crust after heavy rainfall and flooding. Floodwater also deposits a fine clay layer or crust on top of the soil, which prevents oxygen penetration into the soil (aeration). This layer should be broken up and incorporated into the soil profile as soon as possible.

Pests and diseases

Many diseases are more active in wet, humid conditions and pests can also cause problems. Remove dying or dead branches that may become an entry point for disease organisms or insect pests. Apply suitable disease control measures as soon as possible and monitor for pests.

Grow Help Australia can test your horticultural crops for diseases and pests.

The Australian Pesticides and Veterinary Medicines Authority website contains a complete list of pesticides with registrations or permits.

Also consider...

• These fact sheets provide information on managing specific crops during wet weather and floods.
• Learn more about restoring cyclone-damaged fruit and nut trees.
• Learn more about managing pests and diseases of plants and controlling summer pulse pests in wet weather.