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)
Principles of Nutrient Management
- Always remember that the nutrient status of a given soil is a balance sheet.
- High yielding crops remove nutrients, which must be replaced.
- Nutrient status depends on the previous crop and how well it yielded.
Fritz Haber, German Chemist
Developed a process with Bosch to fix nitrogen from the air, combined with hydrogen under high temperature and pressure with a catalyst to produce ammonia.
Initially for WW1
Mustard gas
Zyklon B
Later the Haber-Bosche process was modified for fertilizer production
The Green Revolution
Norman Borlaug, American scientist
“The Father of the Green Revolution”
Began in Mexico in the 1940s
Disease resistance
Dwarf wheat
Occurred in the 1950s - 1960s
Irrigation, mechanization, management, pesticides, fertilizers, varieties
Increased Harvest Index (HI), increased yield
1960s India
”IR8” rice + irrigation + fertilizer
Effectively more than doubled our yields and food production
Modern agricultural technologies
Issues with monocrops today?
Did it lead to overpopulation?
Borlaug won a Nobel Peace Prize in 1970
Cultural Practices: Seeding
Plant Population
- Target plant stand, not seeding rate
- Seed size variation
- Calculating correct seeding rates
Effect of soil temperatures, seeding depth, row widths, and seeding dates on crop stand and final yields.
Main goal of seeding
To bring the seed into hydraulic contact with the soil
To facilitate rapid and even moisture uptake
Management factors include:
Seed quality (pedigree seed)
Rate, date and arrangement of seeding
Variety
Plant populations
- How much to plant?
- Optimum population
- Species and variety differences - How to plant it?
- Spatial arrangement, rows, etc
- Depth control
- Method to put it there
- Time of planting - Interaction of how much to plant (1.) and how to (2.) with resources available for growth
- Moisture, temperature, soil and climate
- The place of seed in the system
- Fundamental importance of good seedling growth
‘Book’ seed rates, Cereals
Lower seed rates in dry areas
Higher seed rates in wet areas
Higher seed rates help control weeds and promote earliness, but may also promote lodging
*Higher rates are recommended in northern Alberta and B.C., especially on fallow
Seed Rates Target
Target: Seeded Plants / Unit Area
Based on known 1,000 Kernel Weight (TKW)
105 kg/ha is converted to bu/acre depending on the sample bushel wt.
- 9 bu/ac wheat = 60 lb
- 3 bu/ac barley = 48 lb
Seed Rates examples.
- 49 x 10-2 x kg/ha = bushel per acre, (60 lb wheat, soybean, peas)
- 59 x 10-2 x kg/ha = bushel per acre, (56 lb rye, corn, flax)
- 86 x 10-2 x kg/ha = bushel per acre, (48 lb barley, buckwheat)
EXAMPLE:
Variety A weights 35g/1,000 kernels
300 seeds / m2 = (35 𝑥 300)/1,000 = 10.5g / m2
(10.5 g/m2) x 10,000 m2/ha = 105,000g/ha
= 105 kg/ha
Plant Stand Targets
150 plants/m2 = Low rate, Dry land
300 plants/m2 = Good target stand in good moisture
500 plants/m2 = High rate used in intensive management
650 plants/m2 = Common European & Chinese rates
Plant Stand Adjusting Rates
- Adjust for germination % less than 100% (run a sample)
- Adjust for anticipated field losses (requires experience and field counts)
- Require good control of seeding equipment and good calibration prior to planting
- Take into account row spacing when calculating plants/area:
e.g. 300 seeds/sq yard 4” rows - 11 seeds/running foot 6” rows – 17 7” rows – 19 10” rows – 28 12” rows - 33
Plant Seed Rate Summation
The best seeding practice is to have a target plant stand based on plants/unit area, and based on farm experience.
Reasons:
- Bushel/acre is inaccurate due to variations in bushel - - weight
- Variety
- Sample
- 1,000 KWT not proportional to bushel weight
- Pounds/acre is inaccurate due to variation in 1,000 KWT (ie seed size).
The Effect of Seeding Rate on Grain Yield (Schematic diagram).
Cereals compensate by higher tiller numbers/plant at lower plant density. Similar effects occur in canola and flax, but not in row crops (corn, sunflower).
Depths of Seeding: Considerations
Large Seeds
- More tolerant to incorrect seeding depths, cool soil temp. than small seeds, as they have more energy reserves
Sub crown internode length
- Many cereals form crown roots at the same depth
- Greater chance of fungal attack, therefore: shallower seeding (winter wheat)
- Semi-dwarf cereals have short coleoptiles and an inability to emerge from deep seeding
Research on the effect of Row Width on Yield and yield components.
- Closeness of rows is often set by mechanical limits:
3” is limit
4” is common in Europe - Excellent seedbeds are needed, with good trash control
- Generally narrower rows give higher yields
The effect of spatial arrangement on yield and yield components.
Ideal spatial arrangements is equidistant between all plants to:
Minimize interplant competition
Maximize light interception and hasten canopy closure
Plant Growth Requirements
A good seedbed:
1. To provide suitable seed-soil contact for soil moisture transfer. 2. Provide adequate evaporation and erosion protection. 3. To facilitate fast infiltration of precipitation (less water runoff). 4. Provide solid anchor for plant roots.
Conservation in Crop Production:
Managing moisture and the soil to maintain productivity.
- Climate in temperate regions is usually unpredictable.
e. g. rainfall occurs in localized storms that cover only a narrow strip as they move across the countryside.
Define Wind Erosion
- Soil movement (wind frequency and velocity)
- Evaporation of moisture (wind frequency and velocity
Define Water Erosion
- Rainfall intensity (how much? how fast?)
- The nature of snowmelt in the spring and soil conditions determine how much water and soil is lost in run-off.
Alberta Agriculture: Problems and changes over the years
Tractor power Harvesting methods - swather and combine Summer fallowing Moldboard plow (in south) Crop varieties Irrigation in southern Alberta Pesticides and fertilizers
Wind Erosion: Preventative Measures
Preventive measures are based on eliminating the causal factors…
- Non-erosive condition of the soil itself by keeping a cloddy structure at the soil surface.
cloddy soil surface will absorb more wind energy than a flat, smooth surface
a soil surface that is both ridged and cloddy will absorb even more wind energy - Trash cover on fallow land consisting of stubble, straw etc. on the surface protects the soil.
- Field shelter belts and barrier strips
The barrier strips consist of one or two rows of a tall growing grass or annual plant such as flax, seeded every 50 or 75 feet
(15 to 25m) across the direction of the prevailing wind.
Ideal barrier grows reasonably tall and remains standing over winter
Ideal seeding time is between late June and early July to allow for significant growth, but late enough to prevent seed production
Field shelterbelts and barrier strips reduce the wind
velocity for a distance about 20 times their height on
the leeward side.
- Strip cropping and trash conservation with blade or
cultivator implements on summer-fallow provides
protection against wind erosion.
Strip cropping
planting row crops in strips across the slope, with alternate strips of grain and/or forage crops
combines the soil and moisture conservation properties of cross slope farming with the soil building advantages of a crop rotation and is more effective in reducing soil losses
- Highly erodible soils should not be used for annual crops and should be left permanently seeded to grass.
- Erosion usually begins at focal points (easily eroded areas); detect spots early and spread straw or manure.
Wind Erosion: Research
- Straw/grain ratios of various crops and effect of weather on this ratio
- Amount of plant residue left on the surface by various types of tillage implements.
- Seeding equipment for residue-cover fields
- Width of strips for strip cropping to control erosion on soils of various texture.
- Minimum and zero tillage
- Topsoil losses and their effects on productivity
- Management practices to restore productivity
- Cover crops for erosion control
- Emergency wind erosion control measures
- Soil drifting on irrigated land.
Water Erosion: Major Problems
- Topsoil is lost by sheet, rill and gully erosion, and there is a gradual transport of topsoil down-slope by splash erosion.
Sheet: transport by surface runoff flowing down a hill in a thin layer
Rill: Small concentrated flow path, such as down hill slopes
Gully: channel in the soil where water runs
~30 cm deep; small stream
- Gullies form in fields and roadside ditches; Deep gullies in fields interfere with farm operations, are a source of weeds and pose a safety hazard.
- Roadside ditches, drainage channels, sloughs and streams are filled with eroded materials.
- Valuable water is often lost in spring run-off and from summer rains.
Water Erosion: Control Measures
Deficiency of soil water, preventing optimum crop growth, is an annual problem in many areas in Alberta. Relative humidity is usually low so rates of evapotranspiration are high.
- Water courses likely to form gullies should be seeded down to grass or grass-legume mixes.
- When summer fallowing, as much crop residue as possible should be left on the surface to form a protective cover for the soil.
- Contour strip cropping has been demonstrated at a number of sites in the province. It could be considered where slopes are long and wide.
- Crop rotations including grasses and legumes not only provide protective cover for the soil, but result in an improvement of soil structure and tilth and a chance to build up its organic matter content.
- Tall stubble will trap snow and decrease run-off.
Primary goals of Water Erosion Prevention
- Conserve soil moisture by preventing run-off whenever possible
- Stop gullying by using grassed -in water courses
- Leave sufficient crop residue on the surface to form a protective cover.
Water Erosion: Research
Infiltration rates and water-holding capacities in relation to water erosion
Management Mistakes Resulting in Erosion:
- Water courses are cultivated.
- Steep slopes are cultivated and cropped.
- Fields are summer fallowed when it is not necessary forconservation of moisture.
- Fields are cultivated up and down the slope instead of on the contour.
- Burying all crop residue when tilling their land.
- Allowing water erosion to occur may also cause otherProblems like pollution of streams and rivers.
Organic Matter Losses
Modern swathing and combining techniques, with all crop residues returned to the soil, have halted the decline, and may even increase organic matter levels. However, when the straw is baled and removed there is little crop residue left to protect and improve the soil. Manure helps to maintain high organic matter levels in soils. The value of alfalfa and manure has been demonstrated.
The Future - What can be done to protect and conserve soil?
- Drought-proofing: farmer must be prepared to cope with dry years when they come.
- Conserve and make use of all precipitation: whether rain or snow.
- Keep snow-melt for agricultural purposes.
- Evaporation from the soil be reduced.
- Water-use efficiency of crops be increased.
- Reduced Tillage
Reduced and Zero Tillage
Can be a challenge!
Tillage was the best tool available for many years for weed control - residue management - disease control - seedbed preparation - nutrient management
Therefore removing tillage means different tools and techniques are required
Direct Seeding as a System
Adopting direct seeding is much more than just changing seeding equipment…. Direct seeding is a system that requires careful management of all the interacting components.
Key Components of a Direct Seeding System
Crop Rotation Residue Management Integrated Pest Management Nutrient Management Stand Establishment
Crop Rotation
Diversity is the key to long term success
- helps to manage weeds, disease, residue
- better utilizes resources
- increases yield potential and/or lowers costs
Rotations must also be dynamic
- allow for changes in sequence to match cropping - - - - conditions, climate or markets
- some chemicals will limit re-cropping options
long-term thinking & planning
Diversity in a mixture of…
cereals & broadleaf - oilseeds and pulses - forages
spring annuals, winter annuals & perennials
early seeded & late seeded
short season & long season
early harvest, late harvest & whole plant
high residue & low residue
shallow rooted & deep rooted
high water use & low water use
nitrogen users & nitrogen fixers
Examples of the dangers of non-diverse cropping systems
- same crops > same weeds > same herbicides = herbicide resistance
- same crop in same residue = more disease risk
- lower yields
Residue Management
- expect an increase in surface residue
- rotate high and low residue crops
- select short straw varieties
- manage residue at the combine
- removal or post-harvest management
- wider row spacing
- strategic direction of travel
IPM (Weed Management)
- know your enemy – life cycle, growth habit, etc
- expect changes in weed species
- competitive crop stands
- diverse crop & herbicide rotation
- sanitation
- timely herbicide applications
- annuals, winter annuals, perennials
- on row packing
IPM (Disease Management)
- expect changes in disease pressure
- diverse & long term crop rotation
- know your enemy
- resistant varieties
- seed treatment / fungicide application
Nutrient Management
More than commercial fertilizer application building organic matter - manure applications - nitrogen fixing crops - pulses – field peas, fababeans, etc - forages – alfalfa, vetches, etc
Fertilizer application
- soil testing
- fertilizer type effects application method
- understand soil type, conditions & SBU
- double shooting – deliver seed and fertilizer separate
- low disturbance fall banding / dual pass
Single shoot
- fertilizer is placed with the seed
- not suitable for NH3
- more fertilizer can be placed as
- moisture increases
- organic matter increases
- clay content increases
- specialty products are used – inhibitors/coatings
- seedbed utilization increases
- — wider openers
- — narrow row spacing
Double shoot
- fertilizer is placed separate from the seed
- allows very high rates & use of NH3
How do I get high yields of canola?
- use a good crop rotation
- do a good job of residue management
- have a good weed control strategy
- use a variety suited to your conditions
- ensure good fertility
- use a calculated seeding rate
- seed shallow
- seed slow
- ensure on-row packing
- monitor and manage diseases
- use a seeding system matched to your soil
- and more
