4.10: Questions
- Page ID
- 44384
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)1. Explain what a grass reference crop is and why this concept is used in estimating crop water use.
2. Describe the sources of energy that affect ET. Which sources are most important in semiarid locations?
3. An irrigation district must establish a schedule for water delivery to the 1,000 producers that they serve. Describe and explain the procedure you would use to develop the schedule.
4. Why does a cotton crop have a higher ET rate than field beans when they both completely shade the soil (i.e., after effective cover)?
5. List and explain three ways data on the rate of crop ET are used in irrigation management.
6. Compute the basal crop coefficient on July 1 for tomatoes planted on May 1 in the Central Valley of California.
7. Given the following information:
Maximum daily air temperature = 95°F Daily solar radiation = 28 MJ/m²/d
Minimum daily air temperature = 72°F Elevation above sea level = 1,500 ft
Dew point temperature = 68°F Latitude = 30°N
Daily wind run = 200 mi/d Date is July 25
a. Compute the daily reference ET using the Penman-Monteith method.
b. What fraction of the total ETo is due to the aerodynamic term?
c. What fraction of ETo is caused by the radiation term?
8. The reference ET is 0.30 in/d, the basal crop coefficient is 0.6, and it has been two days since a thorough rain occurred. The soil water depletion is about 20% of the available water holding capacity for the silt loam soil. How much crop ET occurs for these conditions if frc = 0.5? Assume that Kcf = 0.
9. A crop is irrigated with a subsurface drip irrigation system. The reference ET is 0.25 in/d and the basal crop coefficient is 1.05. The soil water depletion is 50% before irrigating, and frc = 0.5. The root depth is 4 ft, and the soil is a sandy loam. How many days will a 2-inch irrigation last if Kcmax = 1.2 and Kcf = 0.0?
10. How many growing degree days would accumulate in one day if the maximum and minimum air temperatures were 90° and 65°F, respectively and the base temperature was 50°F?
11. Given the following data:
Corn planted on May 1. Effective cover date July 10 (end of week 10). Maturity date is September 10 (end of week 19). Irrigated to prevent soil water stress. The crop is irrigated, or it rains once a week. The soil is silt loam.
a. Compute the average daily ET for corn for each week of the season.
b. What is the total seasonal ET?
| Weeks after May 1 | Average ET o (in/d) |
|---|---|
| 1 | 0.21 |
| 2 | 0.22 |
| 3 | 0.23 |
| 4 | 0.24 |
| 5 | 0.24 |
| 6 | 0.24 |
| 7 | 0.25 |
| 8 | 0.25 |
| 9 | 0.26 |
| 10 | 0.26 |
| 11 | 0.26 |
| 12 | 0.26 |
| 13 | 0.25 |
| 14 | 0.25 |
| 15 | 0.21 |
| 16 | 0.23 |
| 17 | 0.22 |
| 18 | 0.20 |
| 19 | 0.18 |
| 20 | 0.17 |