First Hour Exam
March 14, 2003
SOIL 4213/BAE 4213
Name______
Answer & circle all that apply
Relative to the needs for Precision Agriculture your instructors included which of the following;
T F World population increases by 86 million people per year (235,000/day, World Resources, 1996). 33,000 people die each day due to malnutrition/starvation
T F Cropland needed to feed the human population, if population growth stops and land is preserved, will be roughly 3.3 billion hectares, and likely to become limiting near the year 2050
T F When larger plot sizes were used (study of <300 experiments), the CV’s from these experiments were found to be larger (e.g., variety trials versus fertilizer trials)
Student Questions:
1. Recalling our discussion on the Green Revolution, in what year did India finally achieve self sufficiency relative to wheat production?
Year: 1974
2. Provide one disadvantage of using a chlorophyll meter to improve N management in a particular crop
(small area/plant)
(high # of of samples required to estimate mean)
3. When using a GPS system, how many satellites are needed to find a 3-D position?
4
4. What is the purpose of an N-Rich Strip? Describe the benefit of utilizing an N-Rich Strip within a conventional farming practice.
To establish the relative need for mid-season fertilizer N applications
Identify the appropriate N rate (tailored to that seasons’ growing conditions)
5. What is NDVI and how can it be used?
NDVI = (NIR-red)/(NIR+red)
NDVI is an excellent predictor of biomass and plant N uptake. It can be used as a tool to refine mid-season fertilizer N rates
6. Remembering the lecture on Response Index (RI) and its components (N-Rich NDVI Strip and Check NDVI), what does an RI of 1.2 represent about an area and also what would an RI of 2 represent about a field?
Higher the RI number the more responsive to nitrogen application, conversely, the lower the RI the less responsiveness to nitrogen application there will be.
7. Which of the following are causes of spatial variability in a wheat field?
a) topography
b) poor seed stand
c) cloud cover
d) compaction
8. CV’s were found to be useful for
a. comparing experimental variation of trials containing variables with common units
b. comparing the variability in seed trials with soil contamination
c. determining stock prices when market fluctuations were high
9. The Coefficient of variation is
a. a Relative measure of the mean
b. (standard deviation/mean)*100 = (s/x)*100
c. (square root of the variance/mean)*100 = √s2/x, where MSE = s2
d. Used to describe the amount of variation in a population (Cochran)
e. root mean square error divided by the mean multiplied times 1000
10. Field Element Size (FES) should theoretically identify (circle all that apply)
a. The smallest resolution where cause and effect relationships can be identified
b. The precise resolution where variances between paired samples of the same size (area) become unrelated and where heterogeneity can be recognized
c. The resolution where the environment is at risk
d. The treated resolution where net economic return is achieved.
e. The resolution where differences in wheat yields are noticed from the air
11. Describe “Yield Potential” as has been proposed in class (YP0). How is it different from “Yield Goal” and why is knowing “Mid-Season Yield Potential” so important?
YP0 = Predicted or potential yield based on growing conditions up to the time of sensing, that can be achieved with no additional (topdress) N fertilization
YP0 is different from “yield goal” because it is the predicted yield within a growing season, based on growing conditions from planting to sensing. Yield goal is generally established prior to planting the crop and is the average yield obtained on X farm over the past 5 years plus 5%.
Mid Season Yield Potential is extremely important because one can accurately predict how much of X nutrient will be removed in that crop (based on yield potential) and work backwards to identify a fertilizer N rate, using a response index specific to a particular nutrient.
12. The concept of “precision agriculture” refers to agricultural practices that, compared to current approaches, are able to
a. more precisely measure production inputs.
b. identify and treat parts of the field that need different input levels than other parts of the field.
c. use GPS to identify exactly where a field implement is when it is treating or harvesting any part of the field.
d. more precisely determine the size of a field.
13. The term “spatial variability” used in describing the concept of precision agriculture refers to
e. the extent to which specified areas, different from each other, are present within a ‘field’.
f. different sized cells that may be used to grid sample and fertilize a field.
g. variation, in the vertical dimension, of volumes above the soil surface that are different from each other.
14. Spatial variability that is related to past production management practices in a field is called
h. inherent variability.
i. diffuse variability.
j. cell variability.
k. acquired variability.
15. For a plant nutrient that is mobile in the soil, like nitrogen, the most important criteria relating to management of fertilizer inputs is
l. knowing or reliably estimating yield goal or yield potential.
m. knowing or reliably estimating available soil nitrogen.
n. the soil texture.
o. soil moisture content at the time of normal fertilization.
16. For a plant nutrient that is immobile in the soil, like phosphorus, the most important criteria relating to management of fertilizer inputs is
p. knowing or reliably estimating yield goal or yield potential.
q. knowing or reliably estimating ‘calibrated’ soil test phosphorus.
r. the soil texture.
s. soil moisture content at the time of normal fertilization.
Define:
INSEY = In Season Estimated Yield = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) = YP0
GDD =Growing Degree Days = (Tmin + Tmax)/2 – 4.4°C
RINDVI = NDVI from plots receiving adequate but not excessive preplant N, divided by NDVI from plots where no preplant N was applied
RIHARVEST = Maximum observed grain yield (treatment average with N fertilizer) divided by observed yield from plots where no N was applied either preplant or topdress
RISV = Estimate of RI (spatial variability), using the average NDVI value from a random sensor sample (100 m in length) collected in a farmers field + 1 standard deviation, divided by the average NDVI value minus 1 standard deviation.
YPN = Predicted or potential yield that can be achieved with additional (topdress) N fertilization based on the in-season response index (RINDVI) YPN= (YP0)*(RINDVI)
Engineering/Precision Agriculture
Sketch and label a semivariogram.
2) A nanometer is:
a) 1012 m e) 1 m
b) 109 m f) 10-3 m
c) 106 m g) 10-6 m
d) 103 m h) 10-9 m
i) 10-12 m
2) In the column “Match” place the letter of the “Question” that matches the “Answer”. There may be more than one question for an answer or more answers than questions.
Question / Answer / Matcha. Distance at which two measurements are no longer related
/ Blue / E
b. Distance over which measurements vary randomly
/ Drift / R
c. 550 nm / Longitude / Q
d. 950 nm
/ GLONASS / J
e. 450 nm
/ GPS
f. 1,500 nm
/ Green / C
g. Hyperspectral measurements
/ Irradiance / I
h. Ratio of incident and reflected light
/ Reflectance / H
i. Light emitted or reflected from an object
/ Many Bands / G
j. Russian satellite navigation system
/ Minor Water Band / D
k. The beacon differential system is operated by…
/ Mean
l. A measure of the distribution around the average
/ Nugget
m. Difference between the maximum and minimum values
/ Omnistar
n. The middle ranked value
/ Range / M,A
o. The standard deviation normalized by the mean / Coefficient of Variation / O
p. Distance from the Equator
/ Sill / B
q. Distance from the prime meridian / Standard Deviation / L
r. Phenomena where the spatial variable tends to increase or decrease with distance / U.S. Coast Guard / K
s. Distance where values are no longer related / Latitude / P
Major Water Band / F
Median / N
3) Differential correction minimizes the effect of _____ on GPS positional error
a) Selective availability
b) GPS satellites moving below the horizon
c) Atmospheric effects
d) Multiple paths taken by the GPS signals
e) Fewer than three GPS available satellites
4) List two readily available GPS differential correction services.
WAAS
Omnistar
Coast Guard
EGNOS
5) Why has grid soil sampling not been an effective tool for site specific management?
To be effective soil samples must be made at distances where the measurements can describe the true viability in the field. It is not economically or physically feasible to collect soil samples at these distances (recall the Wibawa paper sited in class where the sampling interval was 50 feet).
6) What is reflectance?
Reflectance is the ratio of the light reflected from the target to the incident (incoming) light.
7) Why do we report optical measurements as reflectance?
Reflectance corrects for shifts in the spectra caused by atmospheric conditions such as dust in the air, moisture in the air, and sun angle.
8) Red reflectance is a measure of which of the following factors:
a) Amount of chlorophyll in the plant
b) Total amount on nitrogen in the plant
c) Plant biomass
d) Percent of ground surface covered by the plant
e) The ability of the plant to reflect heat from the sun
9) Define Circular Error Probability and tell how should you use the circular error probability to evaluate a GPS unit.
Circular error probability is the radius from the average position measurement where you expect 50%, 68%, or 95% of your position measurements to fall (a measure of GPS precision). GPS units with low CEP are more precise.
10) Why might you not buy a GPS unit with the lowest CEP?
Cost increases as the CEP decreases. You may not be able to afford units with the best CEP.
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