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First, there have to be good estimates of both soil moisture depletion and soil infiltration rates.
Depletion information is needed to know how much water to apply.
It can be estimated from evapotranspiration where high water tables do not exist.
With high water tables, depletion must be measured directly by soil sampling, tensiometers, or neutron probe methods, which may be time-consuming and expensive.
Estimates based on evapotranspiration between irrigations will be inaccurate because
of the upward flow of water from a shallow water table.
The intake rate needs to be estimated to know how long to irrigate.
Unfortunately, the intake rates of many Valley soils are almost impossible to estimate by conventional means, such as ring or blocked furrow infiltrometers and inflow/outflow methods.
These are too time-consuming and unreliable in cracking soils.
However, relatively simple computer models, coupled with some advance time data, offer a potential for rapidly estimating infiltration rates.
Second, the short runs, such as those required in site BU, may cause problems with field-wide operations and may be relatively expensive.
Additional conveyance ditches or pipelines and surface runoff recovery systems will be needed, increasing capital costs.
Short runs can also interfere with farming practices.
Third, these drainage reduction measures may require set times incompatible with current labor limitations.
Normally, set times of 12 or 24 hours are used because of the ease of labor management.
Other set times may be difficult to implement.
Fourth, inflexibility in an irrigation district's distribution system in responding to frequent changes in demand may limit opportunities to change set times.
However, automation of furrow irrigation, using valves designed for surge irrigation, may overcome the problems of odd set times versus labor management and district inflexibility.
Fifth, leaching requirements under saline high water tables may limit the amount of drainage reduction to less than the potential.
There is a potential for substantial subsurface drainage reduction with properly designed and managed furrow irrigation sysitems.
Existing systems can be upgraded by cutting run lengths and set times, and/or converting to surge irrigation or level basin irrigation, where appropriate.
Major problems exist in achieving the
However, labor management and cultural practices and the management of distribution systems will need to be changed considerably.
The limits imposed by these constraints and the reduced run lengths can only be assessed with field-wide demonstrations of drainage reduction measures.
Where these practices cannot be changed, other types of irrigation systems, such as drip/trickle irrigation or linear-move machines will need to be considered.
Blaine R.
Hanson is Irrigation and Drainage Specialist, Department of Land, Air and Water Resources, University of California, Davis.
How Economic Factors Affect the Profitability of Center Pivot Sprinkler and SDI Systems
In much of the Great Plains, the rate of new irrigation development is slow or zero.
Since the 1970s there has been a dramatic shift in irrigation methods in the Great Plains region, as center pivot sprinkler irrigation systems have become the predominant technology, having replaced much of the furrow-irrigated base.
In addition, a small yet increasing amount of subsurface drip irrigation has been installed.
Although SDI systems represent less than 1 percent of the irrigated area, producer interest still remains high because of their greater irrigation efficiency and irrigated water application uniformity.
As irrigation systems need to be upgraded or replaced, available irrigated water sources become more scarce, and farm sizes become larger, there will likely be a continued interest in and momentum toward conversion to modern pressurized irrigation systems.
Irrigation system investment decisions will be affected by both the physical characteristics of the irrigation systems being considered and the economic environment that irrigated crop enterprises are operating within.
Key assumptions about the physical characteristics of the irrigation systems include input-output efficiencies, life span, and system investment costs.
Key economic factors include commodity prices, costs of key crop inputs, irrigation energy costs, interest rates on operating expenses, the opportunity cost of capital investments, and overall inflation in production costs.
The economic factors affecting irrigation system choices can be strongly influenced by broader macroeconomic conditions and trends in the United States and world economies.
To the degree that the volatile patterns in agricultural, energy and financial markets since the early 1970s continue or even become more pronounced, economic decisions about irrigation system investments will become more riskprone and uncertain.
This paper will discuss how volatile economic conditions in key agricultural and financial markets affect expected relative profitability of center pivot sprinkler and subsurface drip irrigation systems under crop production conditions in the Great Plains.
This analysis will use a K-State center pivot sprinkler and subsurface drip irrigation comparison spreadsheet to estimate the affect of various key economic factors upon investment decisions.
K-State Research and Extension introduced a free Microsoft Excel 1 spreadsheet template for making economic comparisons of CP and SDI in the spring of 2002.
The spreadsheet has been periodically updated since that time to reflect changes in input data, particularly system and corn production costs.
The spreadsheet also provides sensitivity analyses for key factors.
Lamm, et al., explains how to use the spreadsheet and the key factors that most strongly affect the returns comparisons.
The online accessible template has five worksheets , the Main, CF, Field size & SDI life, SDI cost & life, Yield & Price tabs.
Most of the calculations and the result are shown on the Main tab.
Critical field and irrigation system assumptions are illustrated.
This template determines the economics of converting existing furrow-irrigated fields to
center pivot sprinkler irrigation or subsurface drip irrigation for corn production.
Field description and irrigation system estimates
Total Suggested CP Suggested SDI Suggested
Field area, acres 160 160 125 125 155 155
Non-cropped field area , acres 5 5
Cropped dryland area, acres 30 0
Irrigation system investment cost, total $ $73,450 $73,450 $186,000 $186,000
Irrigation system investment cost, $/irrigated acre $587.60 $1,200.00
Irrigation system life, years 25 25 21 20
Interest rate for system investment, % 7.5% 8.0%
Annual insurance rate, % of total system cost 1.60% 1.60% 0.60% 0.60%
Production cost estimates CP Suggested SDI Suggested
Total variable costs, $/acre $517.90 $517.90 $499.85 $499.85
Additional SDI variable costs or savings , $/acre Additional Costs $0.00 $0.00
Yield and revenue stream estimates CP Suggested SDI Suggested
Corn grain yield, bushels/acre Suggested 220 220 220 220
Corn selling price, $/bushel $3.50 $4.00 KSTATE
Net return to cropped dryland area of field $38.55 $36.00 Konsas State University
Advantage of Center Pivot Sprinkler over SDI * $/total field each year $876
* Advantage in net returns to land and management $/acres each year $5
You may examine sensitivity to Main worksheet assumptions on three of the tabs listed below.
Figure 1.
Main worksheet of the economic comparison spreadsheet template indicating the 18 required variables and their suggested values when further information is lacking or uncertain.
The scenario analyzed in this research is a comparison of whether a center pivot sprinkler irrigation system is more or less profitable than a subsurface drip irrigation system on 160 acres of farmland.
The CP system would irrigate 125 acres of the 160 acres of farmland, with the remaining 35 acres divided between 30 acres of non-irrigated or "dryland" cropping systems and 5 acres of noncropped area.
The SDI system would irrigate 155 acres of the 160 acres of farmland, with the remaining 5 acres used for non-
cropped roads and access areas.
Irrigation system design and cost information is available from the authors and the K-State Research and Extension publication Irrigation Capital Requirements and Capital Costs, MF-836.
Only information that is relevant to the comparison of returns for CP and SDI systems is included in this analysis.
This excludes such factors as cost of irrigated cropland which will not vary for those acres that are irrigated under either irrigation system investment scenario.
Non-irrigated cropland returns are included because of the inclusion of dryland acreage under the CP scenario.
Average cash rental rates are included as a market-based proxy for the returns expected from farming nonirrigated cropland.
For further discussion of the assumptions used in this analysis see Lamm, et al..
Actual values used in this analysis may vary from suggested values in the Main tab of the worksheet where current prices and market conditions warrant.
Key information from the Main tab for the following analysis is as follows.
2.
Interest rate for system investment, % = 7.5%
3.
Total variable costs, $/acre: CP = $517.90
4.
Total variable costs, $/acre: SDI = $499.85
5.
Net return to cropped dryland area of field = $ 38.55
Production cost estimates and assumptions represented in the CF tab are based on K-State Research and Extension crop enterprise budget estimates for irrigated corn in western Kansas.
Seeding rate, seeds/acre $/1000 S Suggested 34000 34000 34000 34000
Seed, $/acre $2.49 $2.24 $84.66 $84.66
Herbicide, $/acre $31.06 $28.68 $31.06 $28.68
Insecticide, $/acre $35.64 $35.30 $35.64 $35.30
Nitrogen fertilizer, lb/acre $/lb Suggested 242 242 242 242
Nitrogen fertilizer, $/acre $0.24 $0.40 $58.08 $58.08
Phosphorus fertilizer, lb/acre $/lb Suggested 50 50 50 50
Phosphorus fertilizer, $/acre $0.44 $0.35 $22.00 $22.00

First, there have to be good estimates of both soil moisture depletion and soil infiltration rates.

Depletion information is needed to know how much water to apply.

It can be estimated from evapotranspiration where high water tables do not exist.

With high water tables, depletion must be measured directly by soil sampling, tensiometers, or neutron probe methods, which may be time-consuming and expensive.

Estimates based on evapotranspiration between irrigations will be inaccurate because

of the upward flow of water from a shallow water table.

The intake rate needs to be estimated to know how long to irrigate.

Unfortunately, the intake rates of many Valley soils are almost impossible to estimate by conventional means, such as ring or blocked furrow infiltrometers and inflow/outflow methods.

These are too time-consuming and unreliable in cracking soils.

However, relatively simple computer models, coupled with some advance time data, offer a potential for rapidly estimating infiltration rates.

Second, the short runs, such as those required in site BU, may cause problems with field-wide operations and may be relatively expensive.

Additional conveyance ditches or pipelines and surface runoff recovery systems will be needed, increasing capital costs.

Short runs can also interfere with farming practices.

Third, these drainage reduction measures may require set times incompatible with current labor limitations.

Normally, set times of 12 or 24 hours are used because of the ease of labor management.

Other set times may be difficult to implement.

Fourth, inflexibility in an irrigation district's distribution system in responding to frequent changes in demand may limit opportunities to change set times.

However, automation of furrow irrigation, using valves designed for surge irrigation, may overcome the problems of odd set times versus labor management and district inflexibility.

Fifth, leaching requirements under saline high water tables may limit the amount of drainage reduction to less than the potential.

There is a potential for substantial subsurface drainage reduction with properly designed and managed furrow irrigation sysitems.

Existing systems can be upgraded by cutting run lengths and set times, and/or converting to surge irrigation or level basin irrigation, where appropriate.

Major problems exist in achieving the

However, labor management and cultural practices and the management of distribution systems will need to be changed considerably.

The limits imposed by these constraints and the reduced run lengths can only be assessed with field-wide demonstrations of drainage reduction measures.

Where these practices cannot be changed, other types of irrigation systems, such as drip/trickle irrigation or linear-move machines will need to be considered.

Blaine R.

Hanson is Irrigation and Drainage Specialist, Department of Land, Air and Water Resources, University of California, Davis.

How Economic Factors Affect the Profitability of Center Pivot Sprinkler and SDI Systems

In much of the Great Plains, the rate of new irrigation development is slow or zero.

Since the 1970s there has been a dramatic shift in irrigation methods in the Great Plains region, as center pivot sprinkler irrigation systems have become the predominant technology, having replaced much of the furrow-irrigated base.

In addition, a small yet increasing amount of subsurface drip irrigation has been installed.

Although SDI systems represent less than 1 percent of the irrigated area, producer interest still remains high because of their greater irrigation efficiency and irrigated water application uniformity.

As irrigation systems need to be upgraded or replaced, available irrigated water sources become more scarce, and farm sizes become larger, there will likely be a continued interest in and momentum toward conversion to modern pressurized irrigation systems.

Irrigation system investment decisions will be affected by both the physical characteristics of the irrigation systems being considered and the economic environment that irrigated crop enterprises are operating within.

Key assumptions about the physical characteristics of the irrigation systems include input-output efficiencies, life span, and system investment costs.

Key economic factors include commodity prices, costs of key crop inputs, irrigation energy costs, interest rates on operating expenses, the opportunity cost of capital investments, and overall inflation in production costs.

The economic factors affecting irrigation system choices can be strongly influenced by broader macroeconomic conditions and trends in the United States and world economies.

To the degree that the volatile patterns in agricultural, energy and financial markets since the early 1970s continue or even become more pronounced, economic decisions about irrigation system investments will become more riskprone and uncertain.

This paper will discuss how volatile economic conditions in key agricultural and financial markets affect expected relative profitability of center pivot sprinkler and subsurface drip irrigation systems under crop production conditions in the Great Plains.

This analysis will use a K-State center pivot sprinkler and subsurface drip irrigation comparison spreadsheet to estimate the affect of various key economic factors upon investment decisions.

K-State Research and Extension introduced a free Microsoft Excel 1 spreadsheet template for making economic comparisons of CP and SDI in the spring of 2002.

The spreadsheet has been periodically updated since that time to reflect changes in input data, particularly system and corn production costs.

The spreadsheet also provides sensitivity analyses for key factors.

Lamm, et al., explains how to use the spreadsheet and the key factors that most strongly affect the returns comparisons.

The online accessible template has five worksheets , the Main, CF, Field size & SDI life, SDI cost & life, Yield & Price tabs.

Most of the calculations and the result are shown on the Main tab.

Critical field and irrigation system assumptions are illustrated.

This template determines the economics of converting existing furrow-irrigated fields to

center pivot sprinkler irrigation or subsurface drip irrigation for corn production.

Field description and irrigation system estimates

Total Suggested CP Suggested SDI Suggested

Field area, acres 160 160 125 125 155 155

Non-cropped field area , acres 5 5

Cropped dryland area, acres 30 0

Irrigation system investment cost, total $ $73,450 $73,450 $186,000 $186,000

Irrigation system investment cost, $/irrigated acre $587.60 $1,200.00

Irrigation system life, years 25 25 21 20

Interest rate for system investment, % 7.5% 8.0%

Annual insurance rate, % of total system cost 1.60% 1.60% 0.60% 0.60%

Production cost estimates CP Suggested SDI Suggested

Total variable costs, $/acre $517.90 $517.90 $499.85 $499.85

Additional SDI variable costs or savings , $/acre Additional Costs $0.00 $0.00

Yield and revenue stream estimates CP Suggested SDI Suggested

Corn grain yield, bushels/acre Suggested 220 220 220 220

Corn selling price, $/bushel $3.50 $4.00 KSTATE

Net return to cropped dryland area of field $38.55 $36.00 Konsas State University

Advantage of Center Pivot Sprinkler over SDI * $/total field each year $876

* Advantage in net returns to land and management $/acres each year $5

You may examine sensitivity to Main worksheet assumptions on three of the tabs listed below.

Figure 1.

Main worksheet of the economic comparison spreadsheet template indicating the 18 required variables and their suggested values when further information is lacking or uncertain.

The scenario analyzed in this research is a comparison of whether a center pivot sprinkler irrigation system is more or less profitable than a subsurface drip irrigation system on 160 acres of farmland.

The CP system would irrigate 125 acres of the 160 acres of farmland, with the remaining 35 acres divided between 30 acres of non-irrigated or "dryland" cropping systems and 5 acres of noncropped area.

The SDI system would irrigate 155 acres of the 160 acres of farmland, with the remaining 5 acres used for non-

cropped roads and access areas.

Irrigation system design and cost information is available from the authors and the K-State Research and Extension publication Irrigation Capital Requirements and Capital Costs, MF-836.

Only information that is relevant to the comparison of returns for CP and SDI systems is included in this analysis.

This excludes such factors as cost of irrigated cropland which will not vary for those acres that are irrigated under either irrigation system investment scenario.

Non-irrigated cropland returns are included because of the inclusion of dryland acreage under the CP scenario.

Average cash rental rates are included as a market-based proxy for the returns expected from farming nonirrigated cropland.

For further discussion of the assumptions used in this analysis see Lamm, et al..

Actual values used in this analysis may vary from suggested values in the Main tab of the worksheet where current prices and market conditions warrant.

Key information from the Main tab for the following analysis is as follows.

2.

Interest rate for system investment, % = 7.5%

3.

Total variable costs, $/acre: CP = $517.90

4.

Total variable costs, $/acre: SDI = $499.85

5.

Net return to cropped dryland area of field = $ 38.55

Production cost estimates and assumptions represented in the CF tab are based on K-State Research and Extension crop enterprise budget estimates for irrigated corn in western Kansas.

Seeding rate, seeds/acre $/1000 S Suggested 34000 34000 34000 34000

Seed, $/acre $2.49 $2.24 $84.66 $84.66

Herbicide, $/acre $31.06 $28.68 $31.06 $28.68

Insecticide, $/acre $35.64 $35.30 $35.64 $35.30

Nitrogen fertilizer, lb/acre $/lb Suggested 242 242 242 242

Nitrogen fertilizer, $/acre $0.24 $0.40 $58.08 $58.08

Phosphorus fertilizer, lb/acre $/lb Suggested 50 50 50 50

Phosphorus fertilizer, $/acre $0.44 $0.35 $22.00 $22.00