Archive for the category: Crop management to improve nitrogen efficiency

Helen Suter¹, Charlie Walker², Deli Chen¹

¹ Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Burnley Campus, 500 Yarra Boulevard, Richmond, Victoria 3121, http://fvas.unimelb.edu.au/ Email: helencs@unimelb.edu.au

² Incitec Pivot Fertilisers, PO Box 54, North Geelong, Victoria 3215, Australia

Abstract

The nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) is being widely used across Australian agricultural systems to reduce nitrogen loss from soils, particularly targeting the greenhouse gas nitrous oxide, and to improve nitrogen use efficiency. However, the effectiveness of DMPP is variable and the reason for this has been unclear. A laboratory investigation was undertaken using 30 soils collected from a range of agricultural land uses to identify the key drivers influencing the performance of DMPP. Average nitrification over 14 days across all treatments ranged from -4.61 to 26.89, with a median of 2.57 mg NO₃^–N produced/g soil/day. Cumulative N₂O emissions ranged from 0.01 to 7.74 mg N₂O-N/g soil. However only 3 soils contributed to high emissions and the remaining soils had < 0.63 mg N₂O-N/g soil. DMPP effectively reduced average nitrification by 9-100% (average of 42%) and N₂O emissions by 0-100% (average of 55%) Only manganese and the interaction between organic C and clay influenced DMPP’s efficacy at reducing nitrification, having a negative impact. The efficacy of DMPP at inhibiting N₂O emissions was positively related to pH, Cu and Zn and negatively related to Fe. The results suggest that further investigation of the soil metal-inhibitor interaction, and the role of metals in soil microbial function (nitrifiers and denitrifiers) is required to understand when the DMPP will work best.

Li Qianqian¹, Liu Xuejun¹, Chen Xinping¹, Zhang Fusuo¹

¹ College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, website: http://www.cau.edu.cn/, Email: lilli@cau.edu.cn; liu310@cau.edu.cn

Abstract

Maize field experiments were conducted over two years at Quzhou site (Hebei Province, North China Plain) to investigate ammonia (NH₃) volatilization from urea and from urea amended with 0.12% (w/w) Limus^® (a new urease inhibitor). Grain yields and nitrogen (N) budgets of all N treatments were evaluated to investigate the effects of urea-N application rates and Limus during two summer maize seasons. Cumulative NH₃ losses after two weeks for conventional urea ranged from 42 to 108 kg N ha^-1 (20-57% of applied N), while the new urease inhibitor Limus significantly reduced NH₃ losses by 65 to 90%. However, maize grain yields (9.5-10.1 t ha^-1) were not significantly (P<0.05) increased by Limus compared to conventional urea without Limus (9.0-10.1 t ha^-1). A clear increase in apparent N recovery efficiency (RE_N) with Limus (ranging from 11 to 17 percentage points during two consecutive maize seasons) compared to equal amounts of optimized urea-N. A further 20% reduction in urea N rate amended with Limus led to the same maize yield but substantially decreased NH₃ losses and increased RE_N compared with optimized urea treatment. Our study also demonstrates the role of Limus in reducing NH₃ losses and improving N use efficiency in maize production in the North China Plain.

Peter Scharf ¹

¹ University of Missouri, 108 Waters Hall, Columbia, MO, 65211, U.S.A., http://plantsci.missouri.edu/nutrientmanagement/, http://nvisionag.com/, scharfp@missouri.edu

Abstract

Nitrogen fertilizer has a tremendous impact on crop growth and is essential for feeding the 7.4 billion people on Earth.  It is also the most energy-intensive input to crop agriculture, has a proclivity to escape from ag systems, and has negative off-site impacts when it escapes.  For all of these reasons, efficient use of N fertilizer is essential.  Crop sensors are a promising approach to optimize N fertilizer application rate and timing.  Three separate experiments with maize (corn) helped to define the N efficiency gains to this approach.  One experiment group involved 55 field-scale experiments in which the farmer’s N rate was compared to variable-rate N based on crop sensors.  System efficiency (N removed in grain/[N applied as fertilizer + manure]) was 0.68 with the farmer’s chosen rate, and increased to 0.78 with sensor-chosen N rates.  A second experiment was initiated in 2007 to compare N fertilizer rate and timing decision systems.  For 2007-2014, the most profitable pre-plant N rate (200 kg N ha^-1) gave system N efficiency of 0.43, while sensor-based N rate gave system N efficiency of 0.74. The third experiment was initiated in 2012 and compared a pre-plant N rate of 155 kg N ha^-1 with sensor-based variable-rate N.  System efficiency for pre-plant N was 0.51, and for sensor-based N was 0.57.  In the latter two experiments, pre-plant N treatments had low efficiency in years with high spring rainfall.  Timing of N probably improved N efficiency more than improved N rate.

Lukas Van Zwieten^1,2, 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.

Noura Ziadi¹, Mervin St.Luce¹, Athyna N. Cambouris¹, and Bernie J. Zebarth²

¹Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd, Quebec, QC, Canada, G1V 2J3, Noura.Ziadi@agr.gc.ca

²Agriculture and Agri-Food Canada, PO Box 20280, 850 Lincoln Rd., Fredericton, NB, Canada E3B 4Z7

Abstract

Nitrogen (N) is the most limiting essential nutrient for potato (Solanum tuberosum L.) and its management is important from both economic and environmental standpoints. Controlled-release N fertilizers, such as polymer-coated urea (PCU), could reduce N losses and increase N use efficiency (NUE) by matching the release of N with potato N uptake. During the last 10 years, different studies were conducted in eastern Canada (Quebec and New-Brunswick) to evaluate the effectiveness of PCU in potato production. A total of nine site-years were conducted between 2006 and 2012 to compare the PCU to the most used conventional N sources. Their effects were assessed on various parameters including yield, specific gravity, NUE, chlorophyll meter readings nitrate (NO₃) leaching, and nitrous oxide (N₂O) emissions along with soil nitrate availability during growing seasons and at harvest. Our results showed that PCU can maintain or increase marketable tuber yield and quality, increase NUE, and reduce NO₃ leaching, particularly in excessively wet years. However, higher N availability from PCU may have implications for N₂O emissions and non-growing season N losses. Evidence of the overall economic advantages of using the PCU in potato production, if any, will be needed to influence a more widespread adoption of PCU by producers.

Weijin Wang^1,2, Lawrence Di Bella³, Steven Reeves¹, Melissa Royle³, Marijke Heenan¹, Minka Ibanez³

¹ Department of Science, Information Technology and Innovation, 41 Boggo Road, Dutton Park QLD 4102, Australia; Email: weijin.wang@qld.gov.au

² Environmental Futures Research Institute, Griffith University, Nathan, QLD 4111, Australia

³ Herbert Cane Productivity Services Limited, 181 Fairford Rd, Ingham, QLD 4850, Australia

Abstract

Sugarcane crops are predominantly grown in warm and high rainfall or irrigated areas where substantial fertiliser nitrogen (N) losses can occur. This study was conducted in a wet tropical sugarcane cropping system to assess polymer-coated urea (PCU), polymer- and sulphur-coated urea (PSCU) and the denitrification inhibitor DMPP-coated urea (NICU) on sugar productivity, N use efficiency and profitability at the normal application rate (150 kg N/ha) and a reduced rate (110 kg N/ha). Nitrous oxide (N₂O) emissions were also measured for selected treatments using automatic and manual gas sampling chambers in combination. The results demonstrated that annual cumulative N₂O emissions in the treatment receiving conventional urea at 150 kg N/ha amounted to 4.74 and 9.51 kg N₂O-N/ha, with the fertiliser N emission factor of 1.90 and 3.01%, based on the manual and automatic chamber measurements, respectively. Application of NICU decreased the annual fertiliser-induced N₂O emission by approximately 83%. However, N₂O emissions in the PSCU treatment were about two times that in the conventional urea treatment, probably due to less N leaching from PSCU. Use of PCU, PSCU and NICU at 150 kg N/ha increased the sugar yield by 2.5, 3.3 and 2.8 t/ha, respectively, compared to the conventional urea treatment (8.4 t/ha). The crop N uptake in the aboveground biomass were significantly higher for the coated urea fertilisers than uncoated urea, and higher for PSCU and NICU than PCU at 150 kg N/ha. The farming profits also tended to be higher for the coated urea fertilisers than the conventional urea.