Drip irrigation and similar high-efficiency systems ( e . g . microjet ) are common in horticultural crops ( Stork et al ., 2009 ; Armour et al ., 2013a ; Armour et al ., 2013b ) but are less common in sugarcane production ; however , there is increasing evidence that sugarcane can be produced successfully under drip irrigation ( Attard and O ’ Donnell , 2013 ; Thompson et al ., 2016c ). They are the most costly method and require a high level of skill to operate and maintain . These systems are most suited to the Delta where infiltration rates are high and therefore , furrow irrigation systems are likely to be less efficient , requiring adoption of more advanced techniques to achieve best management practice application efficiencies .
If drip or overhead low-pressure irrigation systems were installed then there would be several additional impacts and benefits which could be significant . Examples are listed below :
� Green cane trash blanketing could be implemented on suitable soils ; �
Nutrient management could be improved with potentially reduced application rates due to greater delivery efficiencies , increased ability to move from single to split or multiple applications ( e . g . weekly as is possible with drip fertigation ); and
� In drip systems herbicide usage could also be dramatically reduced ( no wetting of the soil surface ), due to significantly lower wetting of the soil surface and therefore reduced weed germination ( Shannon , 2014 ). Local studies demonstrated that in years where no rain falls during the early stages of crop development , e . g . the first three months , no herbicide may be required as was the case of several Burdekin drip irrigated fields in 2013 . It is likely the reduced weed population would also alter both herbicide product selection and lower application rates due to the reduced area , maybe 50 per cent , requiring spraying .
The choice of irrigation system depends on local characteristics and requires substantial effort supported by detailed field assessment , and industry consultation . To guide future investment , it would be useful to determine the likely proportion of each system that might be suitable for the BRIA and Delta areas . A first attempt of this estimate was presented in Alluvium ( 2016 ) and shown below in Table 4.3 .
Table 4.3 . Potential future scenario of the proportion of land under higher water application efficiencies at B practice irrigation management that could use each method , included in the Alluvium ( 2016 ) improved irrigation scenario .
Irrigation Method
Well-designed and managed conventional furrow systems
Well-designed and managed automated furrow systems Well-designed and managed drip and overhead low pressure systems
Potential proportion of each sugarcane area that could adopt irrigation method
BRIA
Delta 5 per cent 5 per cent
65 per cent 35 per cent
30 per cent 60 per cent
Other potential benefits of tailoring irrigation methods include : �
�
Yield increases are expected with a move from conventional furrow irrigation to more efficient systems . Shannon ( 2014 ) documents that an average yield increase of 35 t / ha / year was delivered at four different sites , over several years , and across different soils and water qualities .
A trial comparing lower flow furrow irrigation ( 1.5 L / s with typically 18 h irrigation sets ) with higher flow ( 2.0 L / s , 11 h irrigation sets ) while keeping the same irrigation dates , showed improvements of 3.5 ML / ha ( reduction of 2 0 per cent ), a pumping time reduction of 7 h x 21 irrigation events for the year , and an increase in cane yield of 14 t / ha ( 12 per cent increase ) ( BSES , 2006 ). At the time , the farmer was not able to manually operate the irrigations and 18 h irrigation was more practical and
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