Abstract
In this paper the potential benefits of irrigation system evaluations are explored through the analysis of results from a case study. The effects of application depth, operating pressure, distribution uniformity and scheduling technique were evaluated using the ZIMsched 2.0 irrigation systems and crop yield simulation model. Data measured from on-farm irrigation system evaluations performed in Pongola in 2001 and again in 2003, were used in ZIMsched 2.0 to simulate sugarcane yield and water use for the period 1980 to 2000. The simulated crop yield and water use results facilitated a comparison of relative profit margins. The system performance, in terms of uniformity and application depth, was poorer in 2001 than in 2003, largely as the result of low system operating pressures in 2001. Results from the simulations show that with the scheduling practice followed by the farmer in 2001, these low system pressures resulted in reduced water applications. This in-turn resulted in reduced simulated sugarcane yields but an increase in irrigation efficiency, as there were fewer losses due to runoff and deep percolation. The calculated electricity and water costs were also lower in 2001 than in 2003. The system was upgraded in 2002 and the simulations undertaken using the 2003 system evaluation data showed increases in crop yield, water use and profitability, despite the accompanying increases in the calculated electricity and water costs. The improvement in the uniformity of the system from a DUlq of 61 % to a DUlq of 68 % had little effect on the simulated yields. For the case study, the greatest benefit of an irrigation system evaluation was that it provided information which facilitated making improvements to seasonal water applications. Based on simulated yields and water use, the impacts of these improvements on profitability ranged from R164 to R1882/ha.
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Claims 13
Claim · model-written summary
Irrigation uniformity and application depth were poorer in 2001 than in 2003.
Verbatim
e0“The system performance, in terms of uniformity and application depth, was poorer in 2001 than in 2003”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
Low system operating pressures in 2001 largely explained poorer irrigation performance.
Verbatim
e0“The system performance, in terms of uniformity and application depth, was poorer in 2001 than in 2003, largely as the result of low system operating pressures in 2001”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
Low operating pressures under 2001 scheduling reduced water applications.
- Taxon
- sugarcanee1
- Treatment
- low system pressurese0
- Outcome
- water applicationse0
- Direction
- reducede0
- Qualifier
- scheduling practice followed by the farmer in 2001e0
Not reportedComparator
Verbatim
e0“with the scheduling practice followed by the farmer in 2001, these low system pressures resulted in reduced water applications”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
Reduced water applications lowered simulated sugarcane yield.
Not reportedComparator
Verbatim
e0“This in-turn resulted in reduced simulated sugarcane yields”
e1“reduced water applications”
Claim · model-written summary
Reduced water applications increased irrigation efficiency.
- Taxon
- sugarcanee2
- Treatment
- reduced water applicationse1
- Outcome
- irrigation efficiencye0
- Direction
- increasee0
- Qualifier
- fewer losses due to runoff and deep percolatione0
Not reportedComparator
Verbatim
e0“an increase in irrigation efficiency, as there were fewer losses due to runoff and deep percolation”
e1“reduced water applications”
e2“simulate sugarcane yield and water use”
Claim · model-written summary
Calculated electricity and water costs were lower in 2001 than in 2003.
Verbatim
e0“The calculated electricity and water costs were also lower in 2001 than in 2003”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
The upgraded system evaluated in 2003 increased simulated crop yield over the earlier system.
Not reportedComparator
Verbatim
e0“The system was upgraded in 2002 and the simulations undertaken using the 2003 system evaluation data showed increases in crop yield, water use and profitability”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
The upgraded system evaluated in 2003 increased simulated water use.
Not reportedComparator
Verbatim
e0“The system was upgraded in 2002 and the simulations undertaken using the 2003 system evaluation data showed increases in crop yield, water use and profitability”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
The upgraded system evaluated in 2003 increased simulated profitability.
Not reportedComparator
Verbatim
e0“The system was upgraded in 2002 and the simulations undertaken using the 2003 system evaluation data showed increases in crop yield, water use and profitability”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
Calculated electricity and water costs rose with the upgraded system.
- Taxon
- sugarcanee2
- Treatment
- system was upgraded in 2002e1
- Outcome
- calculated electricity and water costse0
- Direction
- increasese0
Not reportedComparator
Verbatim
e0“despite the accompanying increases in the calculated electricity and water costs”
e1“The system was upgraded in 2002”
e2“simulate sugarcane yield and water use”
Claim · model-written summary
Improving distribution uniformity from 61 % to 68 % had little effect on simulated yields.
Verbatim
e0“The improvement in the uniformity of the system from a DUlq of 61 % to a DUlq of 68 % had little effect on the simulated yields”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
The evaluation chiefly benefited the case study by informing improvements to seasonal water applications.
- Taxon
- sugarcanee1
- Outcome
- provided information which facilitated making improvements to seasonal water applicationse0
Not reportedComparator
Verbatim
e0“For the case study, the greatest benefit of an irrigation system evaluation was that it provided information which facilitated making improvements to seasonal water applications”
e1“simulate sugarcane yield and water use”
Claim · model-written summary
Simulated yield and water-use based improvements changed profitability by R164 to R1882/ha.
Verbatim
e0“Based on simulated yields and water use, the impacts of these improvements on profitability ranged from R164 to R1882/ha”
e1“simulate sugarcane yield and water use”