Abstract
The main objective of this thesis was to determine the impact of crop management practices on the grain quality of rice grown in Australia's southern rice growing region to help reduce the variability found within the industry. Nutritional management, irrigation protocols and planting density are controlled farming practices that impact grain quality with effects specific to variety. Analysis of grain quality under various pre-permanent water (PW) and panicle initiation (PI) nitrogen (N) rates revealed increasing the rate of N applied pre-PW significantly increased whole grain yield (WGY; the proportion of unbroken grain expressed as a percentage of harvested grain) in all tested varieties, however, the effect of splitting the same total N rate into two applications on WGY was variety specific. The results in this thesis revealed N applied at PI altered protein composition affecting WGY and pasting properties. Comparison of the water saving technique delayed permanent water (DPW) with conventional irrigation methods revealed at N rates above 60 kg ha-1, WGY was higher in DPW compared to plants grown with conventional irrigation methods. DPW reduced grain filling duration while prolonging the grain ripening phase due to a slower in-field grain drying, which had a positive effect on WGY (Reiziq, r = 0.32; Sherpa, r = 0.29; Langi, r = 0.67; Topaz, r = 0.52; p < 0.05). When analysing cooking parameters, RVA peak viscosity was lower in the water saving irrigation method compared to permanent flood which increased RVA setback for all varieties despite no differences in amylose and total protein content. DPW altered the grain protein composition improving WGY and affected the pasting properties of rice. Analysis of grain quality under various sowing and N rates revealed changes in plant architecture. The differing densities that resulted from varying the sowing rate significantly affected grain weight and milling quality and the response differed between varieties. Decreasing sowing rate increased the number of grains per panicle, reduced grain dimensions, the thousand grain weight (TGW) and slightly increased WGY in the medium grain variety. In the short grain variety, decreased sowing rate increased TGW and reduced WGY in one season. There was a negative correlation between protein content and TGW (r = -0.58, p < 0.001) but a positive relationship between protein content and WGY in both varieties (r = 0.52, p < 0.001). Analysis of grain quality of Reiziq grown with increasing rates of Zn fertilisation demonstrated the Zn content of paddy and milled grain increases with increasing Zn fertiliser rate. However, Zn fertiliser rate did not affect protein content and WGY. Results in this study also demonstrate that RVA trough viscosity was increased by Zn fertiliser, possibly due to increased water absorption and increased starch granule swelling or a change in the amino acid profile. However, the impact on the overall RVA curve was minor. These results indicate that increasing the Zn content of the grain through fertilisation will not affect grain quality but may improve the Zn level delivered to consumers. This study demonstrated progress in understanding the effect of crop management on rice grain quality. Results in this thesis also demonstrated the importance of protein composition on grain quality parameters. A significant challenge for rice growers in Australia and globally is to reduce water usage without impacting crop yield and grain quality. This thesis demonstrated that grain quality is improved when rice is grown using water saving methods, increasing farmer profit per megalitre of water used in crop production.
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Claims 20
Claim · model-written summary
Higher pre-PW nitrogen significantly increased whole grain yield across tested varieties.
- Taxon
- rice
Oryza sativat0 - Treatment
- increasing the rate of N applied pre-PWe0
- Outcome
- whole grain yielde0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“increasing the rate of N applied pre-PW significantly increased whole grain yield (WGY; the proportion of unbroken grain expressed as a percentage of harvested grain) in all tested varieties”
Claim · model-written summary
Splitting the same total nitrogen into two applications had a variety-specific effect on whole grain yield.
- Taxon
- riceOryza sativat0
- Treatment
- splitting the same total N rate into two applicationse0
- Outcome
- WGYe0
- Qualifier
- variety specifice0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“the effect of splitting the same total N rate into two applications on WGY was variety specific”
Claim · model-written summary
Nitrogen at panicle initiation altered protein composition.
- Taxon
- riceOryza sativat0
- Treatment
- N applied at PIe0
- Outcome
- protein compositione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“N applied at PI altered protein composition affecting WGY and pasting properties”
Claim · model-written summary
Nitrogen at panicle initiation affected whole grain yield and pasting properties through protein composition.
- Taxon
- riceOryza sativat0
- Treatment
- N applied at PIe0
- Outcome
- WGY and pasting propertiese0
- Qualifier
- protein compositione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“N applied at PI altered protein composition affecting WGY and pasting properties”
Claim · model-written summary
Delayed permanent water gave higher whole grain yield than conventional irrigation above 60 kg ha-1 nitrogen.
- Taxon
- riceOryza sativat0
- Treatment
- DPWe0
- Outcome
- WGYe0
- Direction
- highere0
- Qualifier
- N rates above 60 kg ha-1e0
- Comparator
- conventional irrigation methodse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“at N rates above 60 kg ha-1, WGY was higher in DPW compared to plants grown with conventional irrigation methods”
Claim · model-written summary
Delayed permanent water reduced grain filling duration.
- Taxon
- riceOryza sativat0
- Treatment
- DPWe0
- Outcome
- grain filling duratione0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“DPW reduced grain filling duration while prolonging the grain ripening phase”
Claim · model-written summary
Delayed permanent water prolonged the grain ripening phase.
- Taxon
- riceOryza sativat0
- Treatment
- DPWe0
- Outcome
- grain ripening phasee0
- Direction
- prolonginge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“DPW reduced grain filling duration while prolonging the grain ripening phase”
Claim · model-written summary
Slower field grain drying under delayed permanent water was positively associated with whole grain yield across four varieties.
- Taxon
- riceOryza sativat0
- Organ / stage
- graine0
- Outcome
- WGYe0
- Direction
- positivee0
- Value
- r = 0.32; Sherpa, r = 0.29; Langi, r = 0.67; Topaz, r = 0.52e0
- Qualifier
- slower in-field grain dryinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“a slower in-field grain drying, which had a positive effect on WGY (Reiziq, r = 0.32; Sherpa, r = 0.29; Langi, r = 0.67; Topaz, r = 0.52; p < 0.05)”
Claim · model-written summary
Water-saving irrigation lowered RVA peak viscosity versus permanent flood.
- Taxon
- riceOryza sativat0
- Treatment
- water saving irrigation methode0
- Outcome
- RVA peak viscositye0
- Direction
- lowere0
- Comparator
- permanent floode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“RVA peak viscosity was lower in the water saving irrigation method compared to permanent flood”
Claim · model-written summary
Water-saving irrigation increased RVA setback across varieties.
- Taxon
- riceOryza sativat0
- Outcome
- RVA setbacke0
- Direction
- increasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“increased RVA setback for all varieties”
Claim · model-written summary
Amylose and total protein content did not differ between irrigation methods.
- Taxon
- riceOryza sativat0
- Outcome
- amylose and total protein contente0
- Direction
- no differencese0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“despite no differences in amylose and total protein content”
Claim · model-written summary
Lower sowing rate increased grains per panicle in the medium grain variety.
- Taxon
- riceOryza sativat0
- Treatment
- Decreasing sowing ratee0
- Outcome
- number of grains per paniclee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“Decreasing sowing rate increased the number of grains per panicle”
Claim · model-written summary
Lower sowing rate reduced grain dimensions and thousand grain weight in the medium grain variety.
- Taxon
- riceOryza sativat0
- Outcome
- grain dimensions, the thousand grain weighte0
- Direction
- reducede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“reduced grain dimensions, the thousand grain weight (TGW)”
Claim · model-written summary
Lower sowing rate slightly increased whole grain yield in the medium grain variety.
- Taxon
- riceOryza sativat0
- Outcome
- WGYe0
- Direction
- increasede0
- Qualifier
- medium grain varietye0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“slightly increased WGY in the medium grain variety”
Claim · model-written summary
In the short grain variety, lower sowing rate increased thousand grain weight.
- Taxon
- riceOryza sativat0
- Material
- short grain varietye0
- Treatment
- decreased sowing ratee0
- Outcome
- TGWe0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“In the short grain variety, decreased sowing rate increased TGW”
Claim · model-written summary
In the short grain variety, lower sowing rate reduced whole grain yield in one season.
- Taxon
- riceOryza sativat0
- Treatment
- decreased sowing ratee0
- Outcome
- WGYe0
- Direction
- reducede0
- Qualifier
- one seasone0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“decreased sowing rate increased TGW and reduced WGY in one season”
Claim · model-written summary
Protein content was negatively correlated with thousand grain weight.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“negative correlation between protein content and TGW (r = -0.58, p < 0.001)”
Claim · model-written summary
Protein content was positively related to whole grain yield in both varieties.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“positive relationship between protein content and WGY in both varieties (r = 0.52, p < 0.001)”
Claim · model-written summary
Higher zinc fertilizer rates increased zinc content of paddy and milled grain.
- Taxon
- riceOryza sativat0
- Treatment
- increasing Zn fertiliser ratee0
- Outcome
- Zn content of paddy and milled graine0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“Zn content of paddy and milled grain increases with increasing Zn fertiliser rate”
Claim · model-written summary
Zinc fertilizer did not affect protein content or whole grain yield, but raised RVA trough viscosity.
- Taxon
- riceOryza sativat0
- Treatment
- Zn fertilisere0
- Outcome
- RVA trough viscositye0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rice”
e0“Zn fertiliser rate did not affect protein content and WGY. Results in this study also demonstrate that RVA trough viscosity was increased by Zn fertiliser”
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