better suited to labour resources . Automation was not available at the time of the trial . This same farmer is now in the process of installing automation on his 200 ha farm .
� Improved Nutrient Use Efficiency . �
Moving to OHLP and drip irrigation allows N fertiliser to be applied in smaller but more frequent doses , rather than the conventional single application applied shortly after harvest . This reduces the risk of N losses , particularly through unexpected rainfall events . Farmers using drip irrigation indicate that nitrogen rate has generally reduced in both plant and ratoon crops , compared to the amount used under the furrow system . Shannon ( 2014 ) reports that these reductions are around 20-25 per cent . When coupled with an average increased cane yield of 25 per cent ( range between 20-48 per cent , in Shannon 2014 ), nitrogen use efficiency ( NUE , t cane / kg N ) would be increased by at least 50 per cent .
Practices to increase water penetration are also likely to be important in the BRIA where surface runoff dominates losses . Guidance from SRA ( 2014 ) highlights the following :
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Where the water penetration problem is not severe , it may be overcome by changing the irrigation technique . More severe problems will require either a change in the quality of the irrigation water or application of a suitable soil ameliorant such as a soluble form of calcium ( gypsum is commonly used ).
� Water penetration can be greatly improved by forming small hills and making a broad flat interspace , lower inflow rates and larger watering sets will also improve soakage . Trickle irrigation may also be of benefit in soils with poor water penetration .
� Too much slope on a block will reduce the intake of water ( e . g . the slope should not exceed 0.125 per cent in poorly drained soils ).
� Where green cane harvesting is practised , using a trash blanket will improve water penetration . Trash slows the flow of water down the drill and allows more time for the water to infiltrate into the soil . Increased irrigation times up to 25 per cent have been observed . As the trash breaks down , the soil structure at the soil surface is improved which aids water infiltration . In young ratoon crops , a trash blanket acts as a mulch to reduce evaporative losses from the soil . Measurements show that up to 40 mm additional soil moisture can be conserved by a trash blanket or more depending on the situation ( SRA , 2014 ).
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Addition of other organic material such as mill mud or other organic material will improve water penetration when incorporated into the soil for up to two seasons .
Delaying irrigation after fertiliser or pesticide applications , which reduces losses . The same principles apply as those described above for nutrients and pesticides above ; essentially , loads and concentrations of nutrients and pesticides in run-off are greatest soon after application and decline with time . Therefore , the timing of irrigation , nitrogen and pesticide application is an important practice for reducing off-farm losses .
Capturing irrigation tailwater to minimise runoff . On many furrow-irrigated farms in the Lower Burdekin , irrigation tail water can be collected in small dams and subsequently used for irrigation ( Thorburn et al ., 2011b ; Shannon and McShane , 2013 ), reducing the potential for off-farm losses of nutrients ( and other chemicals ). It has been estimated that the infrastructure exists to capture some irrigation tail water in 30 per cent ( Davis et al ., 2013 ) to 70 per cent ( Shannon and McShane , 2013 ) of the farmed area in the Burdekin Haughton Water Supply Scheme ( i . e . the southern Burdekin irrigation area ).
Generally , there are more opportunities for recycling in the BRIA because the heavier soil types are typically more conducive to the construction of recycle pits ( high clay content to reduce leaking into the aquifer ) and due to the larger farm size there is usually more land available ( Rickert and Kenniff , 2018 ). The opportunity for construction of recycle pits is generally more limited in the Delta , due to less suitable soil types ( low clay content soils will need to be clay , plastic or concrete lined which becomes uneconomic for most farmers ), less available land due to small farm size and more undulating topography . In addition , the higher infiltration soils common in the Delta often results in limited surface runoff .
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