Lectures 6-11 Flashcards
Natural Environment factor.
En
No Control:
- Rainfall
- Temperature (heat units / frost)
- Day length
- Soil physical conditions
Biotic Environment factor.
Eb
Some Control:
- Fungi
- Insects
- Weeds
Managerial Environment factor.
Em
Full Control:
- Seeding (date, rate, depth)
- Fertilizer
- Chemical applications
- Tillage
- Rotations
Yield function based on Variety, Natural Envirornment Factor, Biotic Environment Factor, and Managerial Environment Factor.
YIELD = ƒ [ variety(G) + En + Em + Eb ]
Describe the Law of the minimum.
The most deficient or most limiting factor will result in crop yield maximized at that level. Need a comprehensive system of management for crop production. A barrel cannot hold anything above the shortest.
Precipitation Limitations during the Growing Season
Rainfall is limiting, so grow crops adapted to the area.
Problems with Summer Fallow.
Intent was moisture conservation, but soil erosion increased. Slow decline in use
Annual total Growing Degree Days (GDD)
(Min + Max) / 2
If min or max less than 5°C, then = 0
Wheat: 1200 GDD
Corn (Taber) & chickpeas: 1700-1800 GDD
Frost-free Period and Length of growing season
Length of growing season = Days above 0°𝐶
Length of growing season (> 5°C)
Causes of and Percent of
Crop Loss Payments
Causes of Percent of
Crop Loss Payments
Drought 40.8 Excess Water 16.4 Cold 13.8 Hail 11.3 Wind 7.0 Insects 4.5 Disease 2.7 Flood 2.1 Other 1.5
Radiative Forcing
The difference between sunlight absorbed and reflected due to the atmosphere. Positive = BAD
“Negative impacts of climate change on cereal yields: statistical evidence from France”
“ … our model ensemble predicts a 21.0% decline in winter wheat yield, a 17.3% decline in winter barley yield, and a 33.6% decline in spring barley yield by the end of the century”
“Uncertainty from climate projections dominates uncertainty from the statistical model.”
“ … our model predicts that continuing technology trends would counterbalance most of the effects of climate change.”
Climate Summit 2014
“Food production will need to increase by at least 60 per cent over the next 35 years to provide food security for the 9 billion people expected to be living on the planet by 2050. The changing climate directly impacts food security and the supply of nutritious, ample and safe sources of reasonably priced food for the planet’s 7billion people as well as their growing demands. The warming of the planet is already affecting yields of crucial crops . Moreover, approximately one-quarter of all greenhouse gas emissions come from land-use, making sustainable practices in agriculture critical.”
Strategies for maximizing solar radiation use and crop yield.
- Plant early for earlier leaf area development. Often, varieties with greater resistance to frost and cool temperatures must be developed.
- Planting at a seeding rate that will develop an optimal LAI (Leaf Area Index) at the maximum leaf rate development.
- Planting at a seeding rate that provides total ground cover during the period of maximum solar radiation levels
- Planting plants uniformly or nearly uniform over the land to reduce early interplant competition and increase the rate of solar radiation interception.
- Fertilizing to increase the rate of growth and photosynthetic efficiency of leaf surface.
- Extending the time of maximum radiation interception by active leaf surfaces (or the LAD).
- Manage weeds to overcome light interception by them.
note: LAI is a measure for the total area of leaves per unit ground area and directly related to the amount of light that can be intercepted by plants. It is an important variable used to predict photosynthetic primary production, evapotranspiration and as a reference tool for crop growth.
Crop Variety Choice
- Varietal choice is important to achieve a well-suited ‘adapted’ crop in a particular location.
- The genetic component giving ‘good adaptability’ is often/usually not known.
- Good adaptability is achieved in many different ways by different varieties.
Some obstacles to increased future productivity
Economic conditions Research funding (staff) Climate (weather) Deteriorating resource base Government policy Lack of markets Producer adoption of technology Inadequate extension (consumer education) Crop storage
Soil Organic Matter
Typically once living plant material
- Decaying matter including fallen leaves, old roots, rotten plant parts
Increases soil aggregate stability
- Reduced water and wind erosion
- Increased root growth and drainage
High water holding capacity
Binds nutrients and releases them slowly
What conditions affect soil organic matter (SOM)? Explain how they affect SOM.
- An increase in summer fallow will decrease organic matter.
- Rotations with high forage use and/or high cropping levels give an increase in cropping material if crop residues are returned.
- Manage crop rotations, and cropping systems appropriately, to preserve soil organic matter. How?
- Studies have shown that Manure and Fertilizers also increase organic matter slightly.
The Development of Saline Soils
- Accumulation of salts from water
- Fertilizer application
- Some Nitrogen compounds are basic
- Phosphorus (phosphoric acid) is an acid
- Basic + Acid = salt
Salinity and Salt tolerance
Crop tolerance to salinity varies with growth stage
Saline soils often have other associated problems affecting growth:
- Drainage, poor roots, drought
- Fertility
- Compaction
- Acidity
Salinazation Under dryland farming:
- Minimize summer fallowing which may often conserve excessive amounts of moisture and lead to lateral transport of salts to low-lying areas.
Plant deep-rooting crops such as alfalfa, to draw down the water table in recharge or around depression areas. - Apply barnyard manure to salt-affected areas to increase the water holding capacity of the soils.
- Use salt-tolerant crops: barley vs oats, brome grass vs timothy, alfalfa vs red clover.
Soil acidity
- As soil becomes more acidic, soluble Aluminum (Al) and Manganese (Mn) increase to toxic levels.
- Al impedes root growth, while Mn directly affects plant photosynthetic capability.
- Acidic soils impede rhizobium activity.
Liming management
Schematic representation of a typical liming program. The soil with an initial pH of 5.0, received
sufficient lime to raise the pH to 6.5. Ten years later, when the pH has dropped to 6.0, a second
application of lime is made to raise the pH back up to 6.5.
The Effect of Fertilizer on Soil Acidity
Liming and/or use of tolerant crops and varieties will be needed in the future, as fertilizers contribute to soil acidification.
Explain in detail the agriculture cycle.
Ideally, the agricultural cycle occurs when the nutrients uptaken by crops that are sold by farmers to feed animals return to the soil by applying animal manure that contributes to increase the soil organic matter, which will can increase minerals and precipitates in the soil that will ultimately return the nutrients consumed in the previous cycle to the following crops. As an example, planting corn and returning cattle manure to the soil illustrates the cycle.
The Main Crop Nutrients (Macro Nutrients)
Nitrogen (N), Phosphorous (P), Potassium (K), Sulphur (S), Calcium (Ca), and Mg (Magnesium)
Micronutrients
Copper (Cu) Boron (B) Chlorine (Cl) Manganese (Mn) Zinc (Zn) Iron (Fe) Molybdenum (Mo)
Common NPK nutrient sources for Alberta.
Nitrogen: different characteristics for leaching, volatilization, and acidification Ammonium nitrate (34-0-0) Ammonium sulphate (ie 21-0-0-24S) Urea (46-0-0) Urea - ammonium sulphate (34-0-0-11S) Anhydrous ammonia (82-0-0)
Phosphorus Monoammonium phosphate (ie 11-51-0)
Potassium
Muriate of potash (ie 0-0-60)
