13: Center Pivots and Lateral Moves
- Page ID
- 44309
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 13.1: Introduction
- This page discusses the invention of the self-propelled irrigator by Frank Zybach in 1948, which paved the way for center pivot and linear irrigation systems. These modern systems are efficient, labor-saving, and adaptable to various terrains. Key components include pivot laterals and towers, with innovations like remote controls enhancing functionality. Both center pivot and linear systems significantly improve irrigation management and are transforming agricultural practices.
- 13.2: Center Pivot Characteristics
- This page covers key aspects of center pivot irrigation systems, focusing on sprinkler discharge requirements, spacing, and area coverage influenced by pivot rotation and end guns. It highlights the calculation of pressure distribution, the impact of pipe diameter on pressure loss, and the significance of monitoring pressure variations to maintain water application uniformity.
- 13.3: Application Rate
- This page discusses the implications of center pivot irrigation systems on water application rates and soil runoff, particularly on steep slopes. It highlights the differences in application rates between outer towers and the need to manage peak rates and wetting times. To mitigate runoff, it suggests adjusting design elements like system capacity and sprinkler types.
- 13.4: Sprinkler and Nozzle Selection
- Determining the proper nozzle size for each sprinkler along the center pivot lateral is complex. The number of nozzles needed, the size of the nozzles, spacing of sprinklers at the point of concern, the diameter of coverage, pressure loss along the lateral, the use of pressure regulators, and the elevation gain around the field are all issues. In addition, every sprinkler along the pivot lateral is considered individually.
- 13.5: Depth of Water Applied
- As indicated earlier, the maximum application rate does not change with the depth of water applied. However, the time required to apply the water is directly proportional to the depth applied. Since the infiltration rate of the soil decreases with time, the longer it takes to apply water the greater the chance of runoff
- 13.6: Remote Monitoring of System Operation and Control
- GPS and communication technology used by the center pivot and lateral (linear) move irrigation industry makes it relatively easy to remotely monitor system operation and control the water application using a computer, tablet, or mobile device. With little effort, irrigation managers can implement important water management decisions and detect system malfunctions or operational problems
- 13.7: Variable Rate Irrigation
- The nozzle flow rate is typically reduced from the design flow rate by using a valve to pulse the nozzle on and off. This provides a finer resolution of control compared to speed control, and irrigation management zones can be defined to follow the shape of irregular soil patterns. One drawback of zone-control VRI is the higher investment cost compared to speed control VRI.
- 13.8: Community Shared Center Pivot Systems
- Changing application depths enables the shared pivot to accommodate various crop types and planting dates in different sectors. It is ideal if fields within a sector all have the same crop and planting date, resulting in similar irrigation needs. It is conceivable that zone control VRI could be used to provide unique irrigation management
- 13.9: Summary
- Manufacturers have continued to improve pivots to operate at lower pressures and have improved sprinkler performance. Equations to determine sprinkler discharge, area irrigated, and pressure distribution are presented. Minimization of surface runoff from pivot sprinklers is a major management concern discussed in detail. Application depths of 0.70 to 1.25 inches per irrigation
- 13.10: Questions
- A center pivot will be installed with 6 5/8-inch outside diameter pipe. The system will include 7 towers (178-ft spans), with a system length of 1,280 ft (including overhang). The flow rate of the entire system is 700 gpm. Determine the pressure loss due to friction (psi) in the pivot lateral without the end gun operating (Table 13.3).
- 13.11: References
- Bittinger, M. W., & Longenbaugh, R. A. (1962). Theoretical distribution of water from a moving irrigation sprinkler. Trans. ASAE, 5(1), 26-30. Camp, C. R., Sadler, E. J., Evans, D. E., Usrey, L. J., & Omary, M. (1998). Modified center pivot system for precision management of water and nutrients.