Benefits of sub-surface application of nitrogen and water to drip irrigated
A summary of an article by the Commonwealth Scientific and Industrial Research Organisation (CSIRO(1) is Australia's national science research agency) and CRC(2) for Sustainable Sugar Production
Courtesy of Netafim University
Thorburn P., Biggs J., Bristow K., Horan H. & Huth N., Townsville, Queensland, Australia
The Australian sugar industry is located mainly along the north eastern coastline in close proximity to environmentally sensitive areas such as the Great Barrier Reef and regional cities, thereby making it hazardous to environmental quality. For this reason the efficiency of water and fertilizer application is of particular importance. During the 1990’s the area of drip irrigated sugarcane quadrupled, from about 1000 to 4000 hectares, yet it was still less than 2% of the total area of irrigated sugarcane. So far most stress has been given to irrigation application efficiency and little to nutrient, especially nitrogen, application efficiency.
N application rate could probably be reduced by 25 to 50% by using subsurface drip irrigation compared to conventional management.
In the present study an agricultural production simulation model (APSIM) was modified and its performance assessed relative to experimental results, and then applied to assess the long-term effect of subsurface fertigation.
The experimental sugarcane crop (var. Q124) against which the model was assessed was planted in September. Irrigation was applied daily through dripline buried at 0.3 m depth. N (urea) was applied at five different rates (from 0 to 240 kg/ha) on ratoon crops and 75% of this rate on the plant crop. For one of the treatments fertilizer was also applied conventionally. Ten years of cropping (17 crop cycles) were simulated.
The model over predicted the absolute sugarcane yield as yield under actual field conditions depends not only on irrigation and fertilization but on other factors as well (e.g. harvest losses, pest damage, poor aeration, lodging). However, relative yields to the yield under zero N were similar in both experiment and simulation. Thus the modified model can be used to examine the response of sugarcane to the application of N by subsurface fertigation over long periods of time. Furthermore, N was more efficient when applied through subsurface drip than conventionally. Over the 17 crop cycles there was 10 to 40% saving of N when applied by fertigation. The simulation conducted in this study suggests the benefit of subsurface fertigation is either a saving in N fertilizer for similar yield or an increase in yield for similar N input. The choice of alternative depends on economics and production system.
This ten-year study shows that subsurface drip fertigation is the method of choice for sugarcane irrigation when water and fertilizer application efficiency is critical either for environmental protection or for resource conservation.
(1) CSIRO is Australia's national science research agency
(2) CRC was established in 1995 under the Cooperative Research Centers Program of the Australian Government and officially ended its term of operation in 2003
Key words: agricultural production, simulation model, subsurface fertigation, subsurface drip irrigation, sugarcane, sugarcane yield, trickle irrigation, yield
Geographic terms: Australia, Queensland