Flashcards in Crop Management Deck (76)
What are the advantages/limitations of crop rotations as compared to monoculture crop?
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
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
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
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?
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