PBL 3: Cropping systems and tillage Flashcards
Cropping systems: crop rotations
A planned sequence of different crops grown over years on the same land. Crop rotations vary in length and diversity of crop species.
Crop rotation advantages
e.g. corn, soybean, alfalfa alfalfa
-Weed control: switching crops helps break weed cycles and reduces weed populations
-Disease and insect control: rotations remove the hosts for diseases and insects (can also be useful habitat for other insects to eat)
-Increase in soil fertility and quality: nitrogen-fixing legume can add nitrogen. Perennial crops that do not require annual tillage increase SOM
-Reduced soil erosion
-Rotation effects
-Less risk, increased diversity:
-Recycling of nutrients
Continuous cropping
same crop is grown for 2 or more years on the same land.
-typically practices when there are economic incentives for growing that single crop or there is a limited market for alternative crops.
-allows for greater specialisation, in management too.
Monoculture systems
involve growing a single crop within a field during the GROWING SEASON.
-simplify crop management
-concentrates efforts and resources on a single crop
Advantages of Monoculture systems
-Machinery specialized for the crop can maximise efficiency of crop planting/harvest
-Chemi “cides” can target specific pests
-Maturity and dry down of all plants within a variety is synchronised.
-Specialized varieties are developed to efficiently use light, moisture, other environmental resources
Polyculture systems (Intercropping)
growing of two or more crops together on the same piece of land during a GROWING SEASON.
-allows for spatial diversification of plant species
-can be challenging to grow due to competition of resources and environment.
Polyculture systems: advantages
-Yield stability
-Greater tolerance to environmental+pest stress
-Income diversification (long-term and short term income of different species)
-Greater overall productivity per acre (potential)
Polyculture systems: Strip cropping
Involves growing crops in monocultures, in adjacent strips planted within a field.
-Can involve alternate rows of annual crops often harvested at different times.
Polyculture systems: Living mulch
Involve planting annual grain crops into a living, but suppressed perennial sod that can recover following harvest of the grain crop.
-provides year-round ground cover for soil conservation and weed suppression.
-Must be suppressed and controlled to avoid competition (otherwise no good :()
Multiple cropping
the sequential production of two or more different crops from the same piece of land each year.
-provides for maximum use of the land and the environment for crop production.
-most practised in regions with a long growing season.
Multiple cropping: Cover cropping
A crop is introduced during or following harvest of the cash crop.
-Can be used to cover the soil during the winter months between annual grain crops, or cool-season harvest.
-Before the next crop is seeded, cover crops are killed before maturity by mowing/tillage/herbicide
Cover cropping advantages:
-protects the soil from wind/water erosion
-absorb excess fertiliser nutrients from the soil
-enhance soil fertility via nitrogen fixation
-reduces weed growth
-control soil moisture levels
Green manure
crops that are grown for the primary purpose of plowing under to improve the soil quality through the addition of SOM and nutrients.
linked to cover cropping
Agroforestry
A type of agricultural system where trees/perennial shrubs are grown for harvest alongside other annual/perennial crops or grazing livestock.
-Can generate additional sources of income, provide species habitat, carbon fixation, environment protection.
Two types of systems: alley cropping and silvopasture
Alley cropping
Trees are grown in rows with other crops between them in the inter-row area. Alleys need to accommodate the size of mature tree crops so enough light can reach the alley crop without shading.
-protects from wind/water
Silvopasture
Combines trees with pastures for livestock utilisation. Trees+livestock both must be intensively managed for production.
-Livestock provides income while trees mature.
-Trees used for timber, nut/fruit crops, etc.
Tillage
land preparation before planting crops. Tillage goals include:
-Incorporation of residues (SOM up)
-Control of crop pests
-Incorporation of manures, fertilisers, lime
-Preparation of seedbed
-Alteration of soil temp+color
Conventional tillage
-Traditional two-step process:
- Primary tillage: uses plowing to disrupt
(Moldboard plowing >15% of previous residue remains/ excess can disrupt SOM+Disks
- Secondary tillage: uses harrows to smooth
Conservation tillage
creates variable levels of soil disturbance, leaves >30% of crop residue on the soil surface.
-important for reducing soil+water erosion
-protects from rainfall impact
-enhances SOM
-less time+energy required
No-till
Conservation tillage method that does not use primary tillage
-specialised planters with disk openers slice through residues and precisely deposit seed at a desired depth
Methods of increasing diversity in Agricultural systems
- Fallows
- High organic matter inputs
- Reduction in Use of Chemical Inputs
Fallows
Allow a period in the cropping sequence where the land is simply left uncultivatived/fallow.
-allows the soil to “rest”
-secondary succession and diversity revovery
High organic matter inputs
High levels of OM are crucial for stimulating species diversification.
Can be increased by:
-composts
-covercropping
-diversifying, etc.
Reduction in the use of Chemical Inputs
-Many agricultural pesticides either harm/kill many non target organisms in crop systems.
Best to minimise usage.
