Abstract
At the time this project was conceived, rising watertables and subsequent salinisation were considered to be the major threats to the sustainability of irrigated agriculture in the rice growing areas of southern NSW. The biggest threat to sustainability at present is the reduced availability and higher cost of water as a result of the water reforms, and more recently prolonged drought. The hypothesis of this project was that growing crops immediately after rice would increase water use efficiency and profitability of rice-based cropping systems while reducing net recharge. Field experiments were conducted from 1998 to 2000 on two soil types to evaluate the effect of non-irrigated wheat after rice on watertables and net recharge. Rainfall during the wheat season was reasonably similar in all 3 years (270-318 mm) and higher than average (220 mm). Yield and biomass production of early sown (24 April) wheat were higher than yield of late wheat (29 June) (grain yield 4.7 vs 3.8 t/ha at 12% moisture). In the absence of irrigation, the soil profile remained wet in fallow areas, whereas there was considerable drying in areas planted to wheat. The drying created capacity in the soil profile to capture and use winter rainfall. There was a general increase in depth to the watertable during the first half of the season where non-irrigated wheat was grown after rice, but not in the fallow areas. However, in all situations, the watertable rose around the time of rice sowing each year due to a rise in the regional groundwater level. The lumped water balance studies suggested net discharge of about 1 ML/ha between the time of sowing and harvesting wheat after rice in each of the three years, mostly due to higher upflow due to crop water use. In the fallow, net discharge/recharge was close to zero. The CERES Wheat and SWAGMAN® Destiny models performed very well in simulating a wide range of crop and soil water parameters, although the validation data sets were limited in that the yield range was smaller than desirable. Consistent with the field studies, yield of nonirrigated early sown wheat (median 3.8 t/ha) was usually much higher than yield of late sown wheat (median 1.8 t/ha). With one or two irrigations yields of both early and late sown wheat almost always increased, by around 1 t/ha with one irrigation at heading, and an additional 0.5 t/ha with a second irrigation during grain filling. It was only with frequent irrigation (whenever cumulative ETo-rain since the previous irrigation reached 60 mm) that yields of late sown wheat matched (or surpassed) yields of early sown wheat. However, the irrigation requirement for late wheat irrigated at ETo-rain 60 mm was almost always much higher than for early wheat with the same irrigation management (by >100 mm in most years). While irrigation increased yield, it also increased net recharge, with final watertables generally higher by 0.5 to 0.8 m for wheat after rice (wet initial soil) with irrigation at ETo-rain 60 mm compared with no irrigation. The model simulations showed that with wheat after rice, there was net discharge in almost all years, regardless of initial watertable depth (0.5-1.5 m). In comparison, net recharge occurred in 18 to 48% of years with fallow after rice, the amount of recharge increase as initial depth to the watertable increased. For non-irrigated wheat after rice, salinity of the watertable was 2 important where the watertable was shallow (0.5 m), with yield reductions in excess of 1 t/ha in most years. However for deeper watertables, there was no effect of watertable salinity for non-irrigated wheat. With irrigation, watertable salinity had no impact on yields. Growing wheat immediately after rice was financially beneficial, with an increase in Net Present Value (NPV) ranging from 31 to 126 $/ha/yr depending on the rotation. Assuming that the rate of adoption is doubled over 20 years as a result of the project, the NPV of benefits was estimated to be $5.6 million compared with costs of $1.1 million, resulting in a benefit cost ratio of 5.3.
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Claims 20
Claim · model-written summary
Early sown wheat had higher grain yield than late sown wheat.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- early sown (24 April)e0
- Outcome
- grain yielde0
- Direction
- highere0
- Value
- 4.7 vs 3.8 t/hae0
- Comparator
- late wheat (29 June)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield and biomass production of early sown (24 April) wheat were higher than yield of late wheat (29 June) (grain yield 4.7 vs 3.8 t/ha at 12% moisture)”
Claim · model-written summary
Early sown wheat had higher biomass than late sown wheat.
- Taxon
- wheatTriticum aestivume0
- Treatment
- early sown (24 April)e0
- Outcome
- biomass productione0
- Direction
- highere0
- Comparator
- late wheat (29 June)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield and biomass production of early sown (24 April) wheat were higher than yield of late wheat (29 June)”
Claim · model-written summary
Wheat dried the soil profile relative to fallow.
- Taxon
- wheatTriticum aestivume0
- Treatment
- areas planted to wheate0
- Outcome
- soil profilee0
- Direction
- considerable dryinge0
- Comparator
- fallow arease0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the absence of irrigation, the soil profile remained wet in fallow areas, whereas there was considerable drying in areas planted to wheat”
Claim · model-written summary
Wheat increased depth to the watertable in the first half of the season, unlike fallow.
- Taxon
- wheatTriticum aestivume0
- Treatment
- non-irrigated wheate0
- Outcome
- depth to the watertablee0
- Direction
- increasee0
- Comparator
- fallow arease0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was a general increase in depth to the watertable during the first half of the season where non-irrigated wheat was grown after rice, but not in the fallow areas”
Claim · model-written summary
Watertables rose around rice sowing each year.
- Taxon
- rice
Oryza sativae0 - Outcome
- watertablee0
- Direction
- rosee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in all situations, the watertable rose around the time of rice sowing each year due to a rise in the regional groundwater level”
Claim · model-written summary
Water balance indicated about 1 ML/ha net discharge during wheat growth.
- Taxon
- wheatTriticum aestivume0
- Outcome
- net dischargee0
- Value
- about 1 ML/hae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“net discharge of about 1 ML/ha between the time of sowing and harvesting wheat after rice in each of the three years”
Claim · model-written summary
Fallow net discharge or recharge was close to zero.
- Taxon
- RiceOryza sativat0
- Outcome
- net discharge/rechargee0
- Direction
- close to zeroe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the fallow, net discharge/recharge was close to zero”
t0“Crops After Rice”
Claim · model-written summary
The models performed very well for crop and soil water parameters.
- Taxon
- WheatTriticum aestivume0
- Outcome
- simulating a wide range of crop and soil water parameterse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The CERES Wheat and SWAGMAN® Destiny models performed very well in simulating a wide range of crop and soil water parameters”
Claim · model-written summary
Simulated early sown wheat yield usually exceeded late sown wheat yield.
- Taxon
- wheatTriticum aestivume0
- Treatment
- nonirrigated early sowne0
- Outcome
- yielde0
- Direction
- much highere0
- Value
- median 3.8 t/hae0
- Qualifier
- median 1.8 t/hae0
- Comparator
- late sown wheate0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yield of nonirrigated early sown wheat (median 3.8 t/ha) was usually much higher than yield of late sown wheat (median 1.8 t/ha)”
Claim · model-written summary
One irrigation at heading increased wheat yield by around 1 t/ha.
- Taxon
- wheatTriticum aestivume0
- Treatment
- one irrigation at headinge0
- Outcome
- yieldse0
- Direction
- increasede0
- Value
- around 1 t/hae0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields of both early and late sown wheat almost always increased, by around 1 t/ha with one irrigation at heading”
Claim · model-written summary
A second irrigation during grain filling added 0.5 t/ha yield.
- Taxon
- RiceOryza sativat0
- Treatment
- a second irrigation during grain fillinge0
- Outcome
- an additional 0.5 t/hae0
- Direction
- additionale0
- Value
- 0.5 t/hae0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an additional 0.5 t/ha with a second irrigation during grain filling”
t0“Crops After Rice”
Claim · model-written summary
Frequent irrigation let late sown wheat match or surpass early sown wheat yield.
- Taxon
- wheatTriticum aestivume0
- Treatment
- frequent irrigation (whenever cumulative ETo-rain since the previous irrigation reached 60 mm)e0
- Outcome
- yieldse0
- Direction
- matched (or surpassed)e0
- Comparator
- early sown wheate0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“frequent irrigation (whenever cumulative ETo-rain since the previous irrigation reached 60 mm) that yields of late sown wheat matched (or surpassed) yields of early sown wheat”
Claim · model-written summary
Late wheat required more irrigation than early wheat under the same management.
- Taxon
- wheatTriticum aestivume0
- Treatment
- late wheat irrigated at ETo-rain 60 mme0
- Outcome
- irrigation requiremente0
- Direction
- much highere0
- Value
- >100 mme0
- Comparator
- early wheat with the same irrigation managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigation requirement for late wheat irrigated at ETo-rain 60 mm was almost always much higher than for early wheat with the same irrigation management (by >100 mm in most years)”
Claim · model-written summary
Frequent irrigation raised final watertables by 0.5 to 0.8 m.
- Taxon
- wheatTriticum aestivume0
- Treatment
- irrigation at ETo-rain 60 mme0
- Outcome
- final watertablese0
- Direction
- highere0
- Value
- 0.5 to 0.8 me0
- Comparator
- no irrigatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“final watertables generally higher by 0.5 to 0.8 m for wheat after rice (wet initial soil) with irrigation at ETo-rain 60 mm compared with no irrigation”
Claim · model-written summary
Simulations found net discharge with wheat after rice in almost all years.
- Taxon
- wheatTriticum aestivume0
- Outcome
- net dischargee0
- Qualifier
- almost all yearse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“with wheat after rice, there was net discharge in almost all years, regardless of initial watertable depth (0.5-1.5 m)”
Claim · model-written summary
Fallow after rice had net recharge in 18 to 48% of years.
- Taxon
- riceOryza sativae0
- Outcome
- net rechargee0
- Value
- 18 to 48%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“net recharge occurred in 18 to 48% of years with fallow after rice”
Claim · model-written summary
Watertable salinity reduced non-irrigated wheat yield at shallow depth by more than 1 t/ha.
- Taxon
- wheatTriticum aestivume0
- Treatment
- watertable salinitye0
- Outcome
- yield reductionse0
- Direction
- reductionse0
- Value
- in excess of 1 t/hae0
- Qualifier
- shallow (0.5 m)e0
Not reportedSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“where the watertable was shallow (0.5 m), with yield reductions in excess of 1 t/ha in most years. However for deeper watertables, there was no effect of watertable salinity for non-irrigated wheat”
Claim · model-written summary
Watertable salinity did not affect non-irrigated wheat at deeper watertables.
- Taxon
- wheatTriticum aestivume0
- Treatment
- watertable salinitye0
- Outcome
- effect of watertable salinitye0
- Direction
- no effecte0
- Qualifier
- deeper watertablese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for deeper watertables, there was no effect of watertable salinity for non-irrigated wheat”
Claim · model-written summary
Watertable salinity had no yield impact with irrigation.
- Taxon
- RiceOryza sativat0
- Treatment
- watertable salinitye0
- Outcome
- yieldse0
- Direction
- no impacte0
- Qualifier
- With irrigatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“With irrigation, watertable salinity had no impact on yields”
t0“Crops After Rice”
Claim · model-written summary
Wheat after rice raised net present value by 31 to 126 $/ha/yr.
- Taxon
- wheatTriticum aestivume0
- Treatment
- Growing wheat immediately after ricee0
- Outcome
- Net Present Value (NPV)e0
- Direction
- increasee0
- Value
- 31 to 126 $/ha/yre0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growing wheat immediately after rice was financially beneficial, with an increase in Net Present Value (NPV) ranging from 31 to 126 $/ha/yr depending on the rotation”
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