Crop Management

Question 1

What are the advantages/limitations of crop rotations as compared to monoculture crop?

Answer 1

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

Question 2

What is the role of a fallow in a cropping system?

Answer 2

Used to store soil water, control weeds, and increase nutrient availability

Question 3

What role do green manure crops and cover crops play in a cropping system?

Answer 3

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.

Question 4

What role do companion crops play in a cropping system?

Answer 4

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.

Question 5

What is herbicide carryover?

Answer 5

When pesticide used on a crop damages the succeeding crop

Question 6

Define a hybrid

Answer 6

The offspring of two plants that differ genetically; used to create offspring that are superior, but different characteristics from their parents.

Question 7

What is the difference between a hybrid and open-pollinated varieties?

Answer 7

In a hybrid, pollination is controlled, while in an open-pollinated variety pollination is natural.

Question 8

What is plant maturity and how does it influence hybrid or variety selection?

Answer 8

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

Question 9

What is yield potential and how does it influence hybrid or variety selection?

Answer 9

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.

Question 10

What characteristics does a high quality seed have?

Answer 10

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

Question 11

What is the standard germination test?

Answer 11

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

Question 12

What conditions alter recommended planting depth?

Answer 12

Excessive moisture at normal seeding depth

Lack of moisture at normal seeding depth

Low/high temps

Question 13

What factors influence planting date?

Answer 13

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

Question 14

What are the consequences of seeding earlier or later than optimum?

Answer 14

Delayed germination

Stand losses

Replanting

Yield loss

Question 15

How does soil tilth affect seeding rate?

Answer 15

Poor soil tilth causes less germination and emergence, necessitating higher seeding rates

Question 16

How does crop residue affect seeding rates?

Answer 16

Crop residue can reduce germination and emergence necessitating higher seeding rates

Question 17

How does seed quality affect seeding rates?

Answer 17

As the percentage of pure seed and germination rate decrease, higher seeding rate is recommended

Question 18

How is plant population calculated?

Answer 18

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)

Question 19

What soil factors reduce root growth?

Answer 19

Extremes in pH

Lack of moisture

Excessive moisture

Excessive fertilizer near root

Soil born insects and disease

Soil compaction

Question 20

How do you diagnose a cropping problem in the field?

Answer 20

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

Question 21

Differentiate precision and accuracy

Answer 21

Accuracy describes how close a measured value is to the correct value

Precise describes how close measured values are to each other

Question 22

What is GPS used for?

Answer 22

To determine the position of a sample being taken on the surface of the earth with a receiver that interprets satellite positional information

Question 23

Define guidance systems

Answer 23

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)

Question 24

Define remote sensing

Answer 24

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

Question 25

Define geographical information systems

Answer 25

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

Question 26

Define crop management zone (CMZ)

Answer 26

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.

Question 27

Define variable rate technology (VRT)

Answer 27

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)

Question 28

Differentiate management zones, grid, and field composite approaches to precision farming

Answer 28

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

Question 29

How does soil texture affect yield variability in a field?

Answer 29

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

Question 30

How does soil organic matter affect yield variability in a field?

Answer 30

Source of plant nutrients

Increases soil physical conditions

Impacts soil biology including pests

In general, Soils are more productive if they contain more OM

Question 31

How does topography affect yield variability in a field?

Answer 31

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

Question 32

How does pest distribution affect yield variability in a field?

Answer 32

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

Question 33

How does previous management affect yield variability in a field?

Answer 33

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

Question 34

How does nutrient status and pH affect yield variability in a field?

Answer 34

These can vary within a field, of differences are sufficient, crop yields can be affected.

Question 35

How does drainage affect yield variability in a field?

Answer 35

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

Question 36

Describe the consequences of biomass harvest of a crop

Answer 36

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.

Question 37

What are identity-preserved crops?

Answer 37

Crop varieties that have a specific end-use design or that have restrictions on their end use.

Question 38

Differentiate commodity crops from specialty crops

Answer 38

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

Question 39

Define horticulture

Answer 39

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

Question 40

How does basis influence crop prices

Answer 40

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

Question 41

How does supply and demand influence crop prices?

Answer 41

Influences crop prices locally, nationally, and internationally. And supply increases, prices decline and vice versa.