crop rotation 8 march2012-edit2

Crop rotation, cover crops and ecological weed management

Assist.Prof.Dr. Boonthida Kositsup

Department of BotanyFaculty of Science

1

2

Definition of a weed• A weed is an undesired

plant out of place– Water hyacinth in a

aquatic garden: not a

weed– Water hyacinth clogging

canals: a weed

3

What is a Weed?

• A plant that is growing where it is not wanted Roberts et al. 1982. Weed Control Handbook

4

What is a Weed?

• A plant that is successful in colonizing disturb, and maintaining their abundance under conditions of repeated disturbances

MohlerC., 2001. Ecological Management of Agricultural Weeds

5

Disturbance

• An event that disrupts ecosystem, community or population structure

• Changes resources, substrate availability or the physical environment

Pickett and White, 1985

6

7

Why Do We Have Weeds?

BECAUSE WE CREATE THE ENVIROMENTS WHERE WEEDS THRIVE (go, develop or be successful)!

8

What management practices contribute to weed problems?

• Poor soil management• Excessive use of manure• Poor crop rotations using crops with similar

seasonal growth patterns which have similar weed species associated with them.

9

Weed Management

• GoalManage cropping systems (not just weeds!) so that the resources made available through disturbances are captured by crop and not by weeds

10

What are some conventional treatments used to control weeds?

• Physical removal– The use of agricultural tools such as hoe to

physically remove weeds

• Chemical suppression– Herbicide application is not favored in ecological

farming

11

What are some basic principles for ecological weed control?

• Create a diverse ecosystem. Use as many species and types of plants as possible

• Use a good crop rotation• Don’t over fertilize your soil with manure or

fertilizers as this will leave too much fertility on the soil for weeds

• Use clean seed (free of weeds)

12

Crop Rotation

“Rotation of crops, when accompanied by care in the use of pure seed, is the most effective means yet devised for keeping land free of weeds.”

Leighty (1938)

13

Crop rotation

• is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons.

14

Crop rotation: two considerations

1.Vary the seasonality of plantingVarying crop seasonality and management practices

prevent any one species from getting out of control

2.Vary crops allow you to vary management practices

15

How does crop rotation help control weeds?

• Breaks weed multiplication cycles, as certain weeds are associated with certain crops.

• Maintain soils fertility which helps crop growth.

• Crops that have different season growth patterns compete for weed space on the field, as weeds have different growth cycles.

16

Cover crops

17

are crops whose main purpose is to benefit the soil, to manage soil fertility, but is not intended to be harvested for feed or sale.

What is a cover crop?

A crop whose main purpose is to benefit the soil or other crops in one or more ways, but is not intended to be harvested for feed or sale.

18

Cover crops

• Plants that are grown for various ecological benefits other than as a cash crop (a crop that is grown mainly to be sold).

• They may be grown in rotations during periods when cash crops (main crops) are not grown.

19

Advantages of cover crops

• Cover crops can also improve soil quality by increasing soil organic matter. Increased soil organic matter enhances soil structure, as well as the water and nutrient holding of soil.

• Weed suppression

20