Crop Management Flashcards
What are the advantages/limitations of crop rotations as compared to monoculture crop?
Advantages:
Risk spread across more than one commodity
Pest life cycle can be interrupted improving pest control
Yield of one or more of the rotational crops can increase compared to a single crop system
Erosion may be less due to soil coverage
Soil physical properties (infiltration, tilth) may improve
Limitations:
Requires a higher level of management, more planning
May require more or different equipment
Yield of one or more of the rotational crops may decrease compared to a monoculture
Time management (seeding, fertilization, pest control) may be difficult
May be more soil compaction from implements
What is the role of a fallow in a cropping system?
Used to store soil water, control weeds, and increase nutrient availability
What role do green manure crops and cover crops play in a cropping system?
They are grown to retain nitrogen in the root zone for the subsequent crop, to protect the soil surface from erosion, to increase the soil organic matter, to increase infiltration and decrease runoff and may be used for grazing.
What role do companion crops play in a cropping system?
They are grown within a major crop to more completely cover the soil surface with harvestable crop. Some erosion control is possible but main role is to be a second harvestable crop on the same acreage.
What is herbicide carryover?
When pesticide used on a crop damages the succeeding crop
Define allelopathy
When one plant impairs the growth of another by release of a chemical toxin
Define a cultivar/variety
Plants that are clearly different from others and whose offspring retain distinguishing characteristics of the parents
Define a hybrid
The offspring of two plants that differ genetically; used to create offspring that are superior, but different characteristics from their parents.
What is the difference between a hybrid and open-pollinated varieties?
In a hybrid, pollination is controlled, while in an open-pollinated variety pollination is natural.
What is plant maturity and how does it influence hybrid or variety selection?
Maturity: the point in time when harvest can begin
Can be used to avoid environmental stresses (temp, drought), decrease harvest loss (shattering, wet/dry cycles), use harvesting equipment effectively, allowing double cropping, etc
What is yield potential and how does it influence hybrid or variety selection?
Yield potential: refers to the yield that can be achieved in the absence of stress for a given geographical area.
If the yield potential is high and stress can be controlled, the variety is desirable.
Define a transgenic crop
Genes in that species have been altered directly or through insertion of foreign genetic material.
Why are randomization and replication important in field trial?
Randomization is used to place experimental treatments in locations within a field trial so that differences among treatments can be determined as real (significant) or arbitrary (not significant).
Replications are used to estimate the variability within a treatment across the field trial.
What is required in order for a seed variety to be protected?
Must be shown to be new (never sold)
Distinct (unique characteristics)
Uniform (same characteristics within seedlots)
Stable (can reproduce with same characteristics)
What characteristics does a high quality seed have?
High percentage of pure seed
Low percentage of other varieties, other crops, noxious weeds, objectionable weeds, total weed seed, hard seed, and inert matter
High germination percentage
High tolerance of environmental stresses
High resistance to disease
What conditions reduce seed quality?
Early freezes or excessively high temps
Excessive moisture and disease
Alternate wetting/frying cycles
Improper combine settings
Improper storage causing heating and diseases
Improper use of grain handling equipment
What is the standard germination test?
Seeds not in dormancy are germinated under controlled temp, moisture, and light.
Seed germination percentage is the percentage of viable seedlings of the total seedlings tested
If seed is not stored properly, germination can decline
How is pure live seed calculated?
PLS= fractional pure seed content * germination fraction time* 100
How is amount of seed calculated?
Amount of seed needed = seed rate/ %PLS as a decimal fraction.
Seeding rate can be adjusted for large/small seed sizes and for an insurance factor
What is a seedlot?
A quantity of seed that has the same characteristics within approved limits or tolerances.
Characteristics can include amounts of pure seed, other crop seed, seed seed, and inert matter; germination percentage; and dormant seed
What conditions alter recommended planting depth?
Excessive moisture at normal seeding depth
Lack of moisture at normal seeding depth
Low/high temps
What factors influence planting date?
Soil temp optimum for germination
Soil moisture between field capacity and permanent wilting point
Soil aeration to provide sufficient oxygen
Soil problems absent (salinity, extremes in pH)
Availability of labor and equipment
Anticipated weather patterns
Adaptation of crop to soil and climatic conditions
What are the consequences of seeding earlier or later than optimum?
Delayed germination
Stand losses
Replanting
Yield loss
How do planting practices affect seeding rate?
If plants/ac are to remain constant, seed planted per row foot will decrease as rows become more narrow
If plants/ac are to increase, seed planted per row foot will also increase as rows become more narrow
How does soil tilth affect seeding rate?
Poor soil tilth causes less germination and emergence, necessitating higher seeding rates
How does soil salinity affect seeding rate?
Soil salinity can reduce stands and cause seedling death. Removing salts by soil amendments and leaching is preferable to increasing seeding rate
How do environmental conditions affect seeding rate?
Adverse climatic conditions lead to less germination and emergence necessitating higher seeding rates
How does crop residue affect seeding rates?
Crop residue can reduce germination and emergence necessitating higher seeding rates
How does seed size affect seeding rates?
As seed size increases, the seed per bushel decreases, and higher seeding rates are recommended
How does seed quality affect seeding rates?
As the percentage of pure seed and germination rate decrease, higher seeding rate is recommended
How is plant population calculated?
The number of plants per a given row distance/area are counted in several random locations in the field.
Mean is computed (plant/ft or plants/sq ft)
Plants/ac= (plants/ft)* (43,560 sqft/ac)/ (row spacing [in])/(12 in/ft))
Plants/ac= (plants/ sq ft)*(43,560 sq ft/ac)
Differentiate seeding rate, plant population, and harvest population
Seeding rate: number of seeds planted per acre
Plant population: number of planted seeds that germinated, emerged, developed into productive plants per acre
Harvest population: plant population at harvest
Define germination and emergence
When the seed embibes water, the embryo develops, and the Coleoptile (monocots) or hypocotyl (dicots) crosses the soil-atmosphere interface
Define vegetative growth stage
Includes the development of roots, stems, and leaves
Define the flowering stage
A reproductive phase where blooms/flowers are produced
Define seed development stage
Includes development of the seed embryo and surrounding seed cost
Define when physiological maturity occurs
At max seed dry weight
When is germination and emergence reduced?
Soil moisture is above field capacity or below permanent wilting point
Soil temp is not within optimum range
Soil oxygen levels concentration is small or zero
What happens to plants at very high temperatures?
The protoplasm in the cells are destroyed (proteins denatured) or the plant is injured due to sun burning
What happens to plants at very low temps?
Frost causes cell damage (ice crystals form in plant), water moves from protoplasm to intercellular spaces, causing dehydration of the protoplasm and death to occur.
What is vernilization?
When periods of low temps are required by a crop to initiate reproductive or vegetative growth
How do plants compensate for excessive precipitation and limiting oxygen in the soil?
Adventitious torts can form at the soil surface to absorb atmospheric oxygen.
If excess water remains long enough, large aerenchyma cells can form in some plants that transport atmospheric oxygen to roots
How do plants compensate for limited precipitation and drought?
Leaf surfaces may become waxy or rough, reducing transpirational water losses
Other adaptations include more efficient and larger root systems and physiological adjustments (osmotic potential in plants, stomata closure)
Define growing degree unit
Growing degree days are used to calculate the cumulative amount of heat to which the plant has been exposed from some starting point in the plants development
Heat units= average temp- base temp
Heat units are added growing degree days
How are growing degree days used to determine the rate of crop development?
Can be used to time:
Application of fertilizer
Application of pesticides to avoid crop injury or improve control
Initiation of scouting for pests
Irrigation or cessation of irrigation
Also used to select hybrids or cultivars of the proper maturity as the growth and development of a crop are related to heat units that accumulate during a growing season
Describe how day length affects flowering in short day, long day, and day neutral crops
The effect of Day length (photoperiodism) on flowering is the impact of the period of darkness.
Short-day plants flower after a series of long dark periods or nights
Long-day plants flower after a period of short dark periods
Day-neutral plants are not affected by the day (night) length
What is the primary growing point of a broadleaf plant (dicot)
The end of the apical meristem of the shoot
What is the primary growing point for grasses (monocots)?
Intercalary meristem located at the base of the internodes
What is the growing season and life cycle of a summer annual?
One growing season
Life cycle: seedlings germinate in the spring, plants produce seed and die in the fall
What is the growing season and life cycle of a winter annual?
One growing season
Life cycle: seeds germinate in the fall, plants produce seed in the spring and die in the summer
What is the growing season and life cycle of a biennial?
Two growing seasons
Seeds germinate in one year one, after over-wintering and vernilization, plants produce seed in the summer of year two and die that fall
What is the growing season and life cycle of a perennial?
More than two growing seasons
Have vegetative structures that allow them to live more than two years
What soil factors reduce root growth?
Extremes in pH
Lack of moisture
Excessive moisture
Excessive fertilizer near root
Soil born insects and disease
Soil compaction
How do you diagnose a cropping problem in the field?
Characterize the pattern of the problem in the field
Have a knowledge of field history and past problems which might recur
Have a knowledge of similar symptoms in other fields
Compare the symptoms to potential problems using above information
Decide upon the most likely cause based on information at hand
If appropriate, collect plant and/or soil samples for lab evaluation
Differentiate precision and accuracy
Accuracy describes how close a measured value is to the correct value
Precise describes how close measured values are to each other
What is GPS used for?
To determine the position of a sample being taken on the surface of the earth with a receiver that interprets satellite positional information
Define guidance systems
Used to determine the position of equipment on the surface of the earth to link that position to some activity (soil sampling, planting, fertilization, pesticide application, harvest)
Define remote sensing
Use of sensors that detect radiation such as visible, infrared, and radar reflecting from the surfaces which can be related to surface properties such as crop type, crop yield, and crop moisture status
Define geographical information systems
Consist of special data that can be put in the form of maps (soil series, crop yield or soil test values vs position on field) and used on site-specific management. The relationship among maps can also be part of GIS
Define crop management zone (CMZ)
An area of a field or fields that receives the same crop input such as fertilizer, pest management or irrigation and is separate economically from other parts of the field or fields regarding that crop input.
Define variable rate technology (VRT)
Applying inputs such as seed, pesticides and fertilizers at varying rates across a field. The rate is varied in response to some field property changing spatially (irrigation, weed populations, soil test values)
Differentiate management zones, grid, and field composite approaches to precision farming
Management zone: a land area that has similar properties and can be managed in a similar manner (may be within field or across different fields)
Grid sampling: sampling soil or plants in a grid (often 2.5 acres) within or across fields to assess variability in soil and plant properties (samples define management zones)
Field composite samples: soil or plant samples taken from areas that have similar properties. Several sub samples are taken within each area, composited and a single sample is analyzed/evaluated
How does soil texture affect yield variability in a field?
It can affect yield in a number of ways
Ex: as clay content of a soil increases, plant nutrient retention and supply, buffering against adverse pH changes, available water, and tendency to compact increase; while water infiltration and soil aeration decrease
Can also affect timeliness and effectiveness of field operations such as tillage, planting, and harvest
How does soil organic matter affect yield variability in a field?
Source of plant nutrients
Increases soil physical conditions
Impacts soil biology including pests
In general, Soils are more productive if they contain more OM
How does topography affect yield variability in a field?
Impacts infiltration, runoff and erosion, each of which impact yield.
Yield decreases are often found in low areas that collect excessive water or steep areas where runoff is rapid and infiltration low
Decline in productivity can occur when soils erode
How does pest distribution affect yield variability in a field?
Can mirror soil properties if those soil properties affect the growth and development of the pest. Extremes in soil pH, OM, or soil water at examples
If higher levels of pests are due to soil properties, yield declines appear to follow soil characteristics, when in fact, they are due to pests
How does previous management affect yield variability in a field?
Can affect yield through pest populations, herbicide carryover, soil fertility, soil pH, and soil physical conditions
Pest management practices, fertilization, liming, and tillage in previous crop can alter the yield of s subsequent crop
How does salinity affect yield variability in a field?
Salinity can occur in localized areas of a field where conditions David accumulation of soluble salts, sodium, or carbonates.
In excess, these accumulations can decrease yields
How does nutrient status and pH affect yield variability in a field?
These can vary within a field, of differences are sufficient, crop yields can be affected.
How does drainage affect yield variability in a field?
Both internal and surface drainage often vary across a field. If excess water accumulated or if the soil is subject to drought, crop yields often decline compared to other parts of the field
Describe the consequences of biomass harvest of a crop
Additional nutrients are removed from the soil, less organic inputs are added to the soil, soil OM will decline, and crop residues are not available to protect soil surface from erosion.
What are identity-preserved crops?
Crop varieties that have a specific end-use design or that have restrictions on their end use.
Differentiate commodity crops from specialty crops
Commodity crops: broadly defined as food, feed, or fiber crops grown on large acreages (rice, corn, soybeans, grain sorghum, wheat, potatoes, cotton)
Specialty crops: fruits and vegetables, tree nuts, dried fruit, and horticulture and nursery crops, including floriculture
Define horticulture
The branch of agriculture with intensively cultivated plants that are used by people for food, medicinal purposes, and aesthetic gratification.
Differentiated from other crops by level of management employed in their production and by their subsequent use
Divided into groups that are edible, for culinary or medicinal purposes, and those used for ornamental/aesthetic purposes
How does basis influence crop prices
Basis is the difference between the current local cash price of the crop and a price at a future date.
If the basis is low or negative, it means local demand for the current crop is low and vice versa for high basis.
One way to estimate a cash price for a given month is to add the long term average basis for that month to the future price for that month
How does supply and demand influence crop prices?
Influences crop prices locally, nationally, and internationally. And supply increases, prices decline and vice versa.
