Transcript Crop rotation - Science at NESS

Crop Rotation
Crop Rotation
Crop Rotation: Growing plants with different
types of crops in succession.
Types of Crops: Root, Leaves, Fruit, Flowers,
Legumes
Example: The first year you plant a crop
harvested for its root. The following year you
plant a crop harvested for its leaves.
Why Rotate Crops
Monoculture: Growing one type of crop on the
same field year after year
Problems that were encountered when the same
type of plant was grown in the field year after year.
1) Some of the nutrients will be depleted more
than others based on the needs of that plant
2) The soil may become contaminated by large
amounts of pests that attack that particular
crops
Choosing Crops
Crop Choice is based on…
Environment
1) Soil
2) Climate
3) Precipitation
Financial
1) Market values (sale crops)
2) Economic gains (crops for livestock)
Crop Rotations
-Crop Rotation may include 2 – 6 different crops
with each crops having a particular benefit either
financial or environmental (benefit to the field)
- Crops may be rotated every year or at different
times in the growing season
- Many crop rotations will include a legume.
Remember legumes have a symbiotic relationship
with bacteria that fix nitrogen = Increased nitrogen
in the soil for the next crop
Examples of Crop Rotation
Rotate Soybeans (legume) followed by corn
How Crop Rotation Works
Four Field Rotation: Started in the 16th century
Four fields are planted beside each other
Crop
Year 1
Year 2
Field A
Corn
Carrots
Field B
Soybeans
Corn
Field C
Lettuce
Soybeans
Field D
Carrots
Lettuce
Crop Rotation With Animals
Crop rotation may be mixed with grazing. First
cows are allowed to graze in the field. Cows
release manure which adds nutrients to the soil
Second year (After the manure has had a chance
to decompose) plants are grown on the cattle
fertilized field
Benefits of Crop Rotation
1) Each crop depends on a specific amounts of each
nutrient. Some plants will use up more of one
nutrient than another.
-By rotating crops you are not constantly depleting
the same nutrient
2) The number of pests that attack each crop is
reduced.
3) Farmers can grow more than one successful crop
per year
= Increased crop yields (10-25%)
Risk of Crop Rotation
• May reduce economic gain if farmer has to
alternate between a high value crop and a low
value crop
• May require different machines (one to
harvest soy and one to harvest corn)
Overall the benefits out way the risks
Assignment
Questions 1-6