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Keith L. Bristow, Altaf A. Siyal and Jirka Šimůnek

Strategies to reduce deep drainage and nitrogen leaching from furrow irrigated systems: A simulation study. CSIRO LAND AND WATER / Sustainable Agriculture. Keith L. Bristow, Altaf A. Siyal and Jirka Šimůnek. Furrow Irrigation.

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Keith L. Bristow, Altaf A. Siyal and Jirka Šimůnek

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  1. Strategies to reduce deep drainage and nitrogen leaching from furrow irrigated systems: A simulation study CSIRO LAND AND WATER / Sustainable Agriculture Keith L. Bristow, Altaf A. Siyal and Jirka Šimůnek

  2. Furrow Irrigation • Need to improve productivity and environmental performance of furrow irrigated systems • Think about potential changes / improvements within a systems context • Consider developed and developing world context • Consider environmental and social (eg labour) implications of potential changes • Draw on experiences from Australia and especially China, Asia, Africa • Improve water use efficiency (reduce evaporation and deep drainage) and nutrient use efficiency (reduce runoff and leaching losses)

  3. HYDRUS 2-D Model • Richards’ Equation (RE) for water flow • Convection Dispersion Equation (CDE) for solute transport Half furrow Ridge Half furrow Flow Domain

  4. P1 P2 Fertiliser P4 P3 Fertiliser P5 Fertilizer placement: 150 Kg N / ha mixed into the top few centimetres of soil

  5. Sn Normal Soil surface management “Water supply turned off when water level reaches a pre-determined depth in the furrow” Sc Compacted Plastic cover Sp

  6. Time to ‘turn off’ and ‘water to infiltrate’ Pressure head at base of furrow (cm)

  7. Drainage flux from base of root zone

  8. Effect of soil surface treatment on water applied Initial water held in the profile was 180 mm in all treatments Water application rate = 900 L/hr

  9. Effect of water application rate on water saved Initial water held in the profile was 180 mm in all treatments

  10. Sp Sn Nitrogen concentration

  11. Effect of fertiliser placement on nitrogen leached from the root zone Total nitrogen applied was 150 kg N / ha

  12. Conclusions • Can use ‘plastics’ to maximise the benefit of capillarity and minimise the impact of gravity in furrow irrigated systems • This analysis demonstrated water savings can exceed 40% and leaching losses can be reduced from 33% to zero • Projects to explore design and management of ‘smart’ plastics are now underway

  13. Soil water content at initiation of irrigation and 120 hours later

  14. Flow Domain

  15. Boundary conditions

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