Assessing controlled release and deep placement N fertilizer technologies in subtropical sugarcane

Lukas Van Zwieten1,2, Josh Rust1, Terry J Rose2, Stephen Joseph3, Rick Beattie4, Scott Donne3, Greg Butler5, Robert Quirk6, Stephen Kimber1, Stephen Morris1

1 NSW Department of Primary Industries, 1243 Bruxner Highway, Wollongbar, NSW, 2480 www.dpi.nsw.gov.au

2 Southern Cross Plant Science, Southern Cross University, Military Road, East Lismore, NSW, 2480

3 Discipline of Chemistry, University of Newcastle, Callaghan NSW 2308

4 Sunshine Sugar, Suite 1, Level 1, Cnr River and Martin Streets Ballina, NSW, 2478

5 South Australia No-Till Farmers Association, PO Box 930 Berri, SA,5343

6 30 Duranbah Road, Duranbah, NSW 2487

Abstract

Maintaining adequate nitrogen (N) nutrition in sugarcane requires matching supply with demand. The NSW sugarcane system predominantly grows sugarcane over 2 years, with fertiliser N supplied within a couple of months after planting cane or harvesting the previous crop and ratooning. We evaluated alternate N fertiliser technologies; a) that supply N deeper into the soil profile (ca. 50-200mm) via ultra-high pressure, and b) slow release products. Preliminary results indicate that polymer coated urea is able to lower nitrous oxide (N2O) emissions during peak events, presumable by limiting mineral N in soil at any given time. This lower soil NO3- was observed at site 1 in the 2015/16 season only. The N fertiliser based on a modified charcoal pellet gave lower cumulative N2O emissions than farmer practice urea (matching N rate) at only one of six field sites. The emissions of N2O did not appear to depend upon the dose of fertiliser N applied, but were site specific, and highly dependent upon rainfall events.