Agronomy 280

NDVI stands for normalized difference vegetation index and it is defined as:

(NIR-VIS(red))/(NIR+ VIS(red))

Maintaining a soil pH in a _____ range improves nutrient availability for most row crops.

6 to 7

Ideal pH for alfalfa is in the _____ range

6.7-7

How can production be increased?

Increasing area, yield or area & yield

Vegetative Stages

VE= Emergence Vn= nth Leaf VT= Tasseling

Crops are successful because these 3 things work together:

genetics, management, environment

Combines with yield monitors can provide spatial estimates of ______ and _____

height and yield

Acid Detergent Fiber is _____ correlated with low digestible a forage may be

negatively

A nematode is a

worm

Components of forage are normally used to access its quality. Neutral Detergent Fiber is composed mainly of

Cellulose, hemicellulose, lignin

The economic threshold for insect control

Declines if the price of grain increased

Soybean nodulation ______ nitrogen fertilization

Decreases with

The most effective strategy for nematode control in soybeans is through

Rotation with non-hosts and use of resistant varieties

For alfalfa, _____ planting is recommended for Iowa, whereas _____ planting is recommended for Missouri

Spring, Fall

Yield maps can provide useful information about diagnosing yield losses due to

change in soil properties (pH, fertility, drainage

Rotary hoes:

will uproot small, shallow-rooted weeds

Single rate application of nitrogen fertilizer has always been proven superior to variable rate application

False

Herbicides can be classified in terms of how they affect the plant. ____ if considered a systemic herbicide whereas ____ is a contact herbicide

Glyphosate, Paraquat

The correct relationship is

Production= Area x Yield

The ______ of a nematode are highly variable and can be confused with other stresses. The ____ of the disease is detected by observing the cysts on the soybean roots.

Symptoms, sign

Which of these factors is NOT currently considered in the Iowa State University N rate calculator.

Yield goal

The correct equations for yield components for small grains is (order is important):

Yield= plants per acre x tillers per plant x kernels per tiller x kernel weight

Soybean nodulation ______ N fertilization

decreases with

One of the major agronomic differences between determinate and indeterminate soybeans is that indeterminate soybeans flower over ____, and determinate soybeans flower over_____

1 to 3 days: 3 to 4 weeks

An inter row cultivator is normally operated at depths of:

1/2-1.5 inches

Normal development for typical corn belt hybrids results in plants which will have around_____ total leaves

19-20

Conservation tillage is defined as the management that results in at lease ____ precent residue cover

30

On average total N uptake by the corn plant is about _____ percent before flowering and about _____ percent after flowering

50, 50

On average, corn without N fertilized yields about ______ percent following corn and ______ percent following soybeans compared to the agronomic optimum

55 and 70

Deep tillage is defined by operations that go ____ inches or deeper using implements such as chisel plows, or moldboard plows.

6

Choose the herbicide with high leaching potential

Atrazine

______ is an effective herbicide when applied before the weeds have emerged (pre-emergence)

Atrazine

Most systems that reduce the amount of tillage tend to increase the amount of insect pest pressure. However, the ______ is not typically impacted by reduced tillage.

Corn rootworm

The most complete list of precision farming tools is

GPS, GIS, yield monitors, data analysis and Variable Rate Technology (VRT)

Stress (such as drought stress) during VT to R1 will:

Increase the pollen shed-silking interval

_______ is generally the most limiting nutrient in corn production

Nitrogen

What is the main planting month for soybeans in Argentina?

November

The corn rootworm is a significant insect pest of corn. It normally has ____generations per year in Iowa

One

At what stage do silks emerge from the ear?

R1

At what stage in corn development does water use reach a maximum?

R1

Silks emerge from at ear at _____

R1

Reproductive Stages

R1= Silking R2= Blister R3= Milk R4= Dough R5= Dent R6= Physiological Maturity

The critical period for yield determination in soybeans is

R4-R5

The most critical period for yield determination is soybeans is _____

R4-R5

The _____ generation of bean leaf beetle is the most damaging and it is caused by _____ defoliation

Second, Adult beetle

A soybean variety can be considered tolerant if it performs well (ex. high yields) but susceptible because if does not prevent the reproduction of the soybean cyst nematode

True

The European Corn Borer, an insect pest, normally has_____ generations per year in Iowa

Two

At what stage does the growing point in corn transition from vegetative to reproductive?

V6

Which of these crop is not commercially available as RoundUp Ready in the US?

Wheat

Silage is

a forage that is cut at high moisture and the fermented

Soybean are normally planted ______ corn

after

Long days (>12 hours daylight) _____ flowering in soybeans

delay

Worldwide yield gaps are _______ at the same rate as in the past

either stable or not increasing

Yield reductions from soybean cyct nematode tend to be ____ on a ______ year because the more shallow rooting system relies more on soil moisture in the upper most soil layers

higher & dry

The goal/s of shallow tillage is/ are to:

kills weeds, incorporate nutrients, incorporate herbicides, level soils

THe most important source of non-fertilizer nitroged are

organic matter and crop residue decomposition