Feature Presentation | INI 2016

The effect of nitrification inhibitors on wheat crop performance on coarse-grained soils in Mediterranean environments

2016 INI, Feature Presentation, Inhibitors to improve N efficiency

Elliott Duncan^1,2*, Cathryn O’Sullivan¹, Margaret Roper¹ and Mark Peoples³

¹ CSIRO Agriculture, Centre for Environment and Life Sciences, Underwood Avenue, Floreat WA 6014, Australia.

²Future Industries Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia.

³CSIRO Agriculture, Black Mountain Laboratories, Acton, ACT 2601, Australia.

Abstract

This research investigates whether nitrification inhibitors (NIs), including DMPP, DCD & nitrapyrin, are effective in preserving ammonium (NH₄⁺) in soil, reducing the abundance of ammonia oxidising microorganisms in soil and improving crop performance in Mediterranean wheat cropping systems. Data from laboratory soil incubation studies and glasshouse pot trials demonstrated that, under controlled conditions, DMPP was highly effective at inhibiting nitrification and limiting the growth of ammonia oxidising bacteria (AOB) for over 100 days on coarse-grained soils common in the Western Australian wheatbelt. This, however, did not result in improvements in grain yield or quality in wheat (Triticum aestivum) cv. Mace which suggests that preservation of mineral N as NH₄⁺ does little for crop N uptake. Under field conditions yield increases of ≈300 kg ha^-1 were observed in the presence of DMPP in a small number of trials. These increases, however, only occurred on soils with a shallow coarse-grained layer (<30cm) over a heavy clay pan. It is likely that the clay layer in these soils slowed the movement of water (and N) thus allowing the crop access to fertiliser N for a longer period of time. Overall, this study demonstrates that NIs slow nitrification in a range of soils common in the study region and in some cases yield and NUE benefits can occur.

Agronomic evaluation of enhanced efficiency N fertilizers in lowland rice

2016 INI, Feature Presentation, Inhibitors to improve N efficiency

Dinesh Kumar

Division of Agronomy, ICAR-Indian Agricultural Research Institute, New Delhi 110 012, INDIA, Email: dineshctt@yahoo.com

Abstract

Nitrogen use efficiency (NUE), expressed as agronomic efficiency, of prilled urea is quite low under lowland rice in India. Among the different strategies used for enhancing agronomic efficiency of fertilizer N, use of enhanced efficiency fertilizers holds a great promise. Therefore a field experiment was conducted at the Research Farm of ICAR-Indian Agricultural Research Institute, New Delhi for two consecutive years. Main objective of the study was to find out the effect of essential and vegetable oils coated prilled urea on grain yield and agronomic efficiency of rice. The treatments (22) comprised of combinations of 3 N rates (50, 100 and 150 kg N/ha) and 7 N sources (citronella oil, meliacins, karanj oil, lemongrass oil, cottonseed oil, palmarosa oil and no oil coated prilled urea) at a thickness of 1000 mg oil/kg urea, and an absolute control. The experiment was laid out in a Randomized Block Design with three replications. Rice grain yield increased significantly up to highest N rate (150 kg/ha). All the oil coated ureas, except palmarosa oil, produced significantly higher rice grain yield over uncoated urea. Citronella oil coated urea produced highest grain yield of rice, being at par to karanj oil and cottonseed oil coated urea, but significantly higher than other coated ureas. The highest agronomic efficiency of nitrogen was recorded with citronella oil coated prilled urea.

The role of nitrification inhibitors and polymer coated urea in N management in the sub-tropics

2016 INI, Feature Presentation, Inhibitors to improve N efficiency

Terry J Rose¹, Lee J Kearney¹, Stephen Kimber², Stephen Morris², Peter Quin¹, Lukas van Zwieten^1,2

¹Southern Cross University, Military Road, East Lismore, NSW, 2480, www.scu.edu.au

² NSW Department of Primary Industries, 1243 Bruxner HWY, Wollongbar, NSW, 2480, www.dpi.nsw.gov.au

Abstract

While there is a growing body of literature suggesting that the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) can reduce N₂O emissions from soils in temperate environments, there is little evidence of its efficacy in subtropical and tropical environments where temperatures and rainfall intensities are typically higher. We investigated N₂O emissions in aerobic rice crops in a subtropical environment in late summer/autumn in 2014 and in an adjacent field in late summer/autumn in 2015. Crops received 80 kg/ha N as either urea, DMPP-urea, or a blend of 50 % urea and 50 % urea-DMPP in 2014, and urea, urea-DMPP or polymer-coated urea (PCU) in 2015. DMPP-urea significantly (P < 0.05) lowered soil N₂O emissions in the 2013-14 season during the peak flux period after N fertiliser was applied, but had no effect in the 2014-15 season. The mean cumulative N₂O emissions over the entire growing period were 190 g N₂O-N/ha in 2013-14 and 413 g N2O-N/ha in 2014-15, with no significant effect of DMPP or PCU. Our results demonstrate that DMPP can lower N₂O emissions in subtropical, aerobic rice crops during peak flux events following N fertiliser application in some seasons, but inherent variability in soil N₂O emissions limit the chances of detecting significant differences in cumulative N₂O flux over longer time periods. A greater understanding of how seasonal and/or soil factors impact the efficacy of DMPP in lowering N₂O emissions following N fertiliser application in the subtropics is needed to formulate appropriate guidelines for its use commercially.

Azolla fertilizer as an alternative N source for red spinach production on alluvial and peat soils in West Kalimantan, Indonesia

2016 INI, Feature Presentation, New methods of measuring reactive nitrogen in the environment

Dwi P. Widiastuti¹, Jessica G. Davis¹, Sutarman Gafur²

¹Colorado State University, Dept. of Soil & Crop Sciences, Colorado State University, Fort Collins, CO, USA, 80523-1170, http://soilcrop.agsci.colostate.edu/, dwi.widiastuti10@gmail.com

² Tanjungpura University, Jl. Prof. Dr. H. Hadari Nawawi, Pontianak, West Kalimantan, Indonesia, 78124

Abstract

Food security is an important goal in Indonesia, and each household is expected to utilize their backyard to provide food (vegetables) for their family. One approach to intensify vegetable production is through locally-grown fertilizer. Through biological nitrogen fixation, the Azolla-Anabaena symbiosis can provide N for vegetable production. The objective of this study was to evaluate the contributions and Nitrogen Use Efficiency (NUE) of A. pinnata as a biofertilizer on red spinach production on Inceptisols and Histosols in West Kalimantan, Indonesia compared to commonly-used fertilizers. The experimental design was a Randomized Complete Block Design with three replications. Five N fertilizer treatments were used: control, urea at 50 kg ha^-1, chicken manure at 5 t ha^-1, Azolla at the urea N rate, and Azolla at the manure N rate. Treatment means were compared using the honestly significant difference Tukey adjusted post hoc test (n=3, P<0.1). Overall, the results showed that Manure had the highest yield in the alluvial soil and it was comparable to Urea; whereas, in the peat soil, the significantly highest yield was also from the Manure treatment, but it was comparable to Azolla applied at the manure N rate. The highest leaf N content was in the Manure treatment (in the alluvial soil) and the Azolla applied at the manure N rate (in the peat soil). The highest NUE was in the Urea treatment in the alluvial soil. Therefore, Azolla applied at the manure N rate can be used as an alternative biofertilizer, especially for peat soil.

The net contributions of fixed N by crop legumes in low rainfall farming systems

2016 INI, Biological N fixation for improved nitrogen utilisation, Feature Presentation

Michael Moodie¹, Mark Peoples², Laura Goward², Nigel Wilhelm³

¹Mallee Sustainable Farming, PO Box 843, Irymple VIC 3498; michael@moodieag.com.au

²CSIRO Agriculture and Food, Black Mountain Laboratories, Canberra, ACT 2601

³ South Australian Research and Development Institute, Glen Osmond 5064, South Australia

Abstract

The inclusion of grain legume crops in low rainfall farming systems of south-eastern Australia can improve subsequent cereal crop productivity where nitrogen (N) is a limiting factor. However, little is known about either the productivity or the capacity of crop legumes to contribute N in this low rainfall environment. Over three seasons (2013-2015) break crop comparison trials were sampled to measure dry matter (DM) production and symbiotic N₂ fixation of chickpea, field pea, lentil, lupin, faba bean and vetch crops grown in the Victorian and South Australian Mallee. On average, shoot DM produced across species and seasons was in the order of 3 – 4 t DM/ha while average grain yields for all species across the three years was around 1 t/ha. Chickpea fixed significantly less shoot N than the other species, which on average fixed ~60 kg N/ha in the above-ground DM across the three seasons. After taking account of the amount of N removed in harvested grain across the three seasons, and including estimates of the likely contributions of fixed N associated with the nodulated roots, 12 of the 15 crop by season combinations were calculated to have provided agronomically significant net inputs of fixed N for the potential benefit of following crops. Therefore it was concluded that legume crops appear to be a viable mechanism to maintain or improve the N fertility of cropping soils in low rainfall Mallee farming systems.

Rhizobial and non-Rhizobial nodulators of Pueraria phaseoloides

2016 INI, Biological N fixation for improved nitrogen utilisation, Feature Presentation

M. M. Wedage¹, D. Gunawardana^1,2

¹Department of Botany, University of Sri Jayewardenepura, Sri Lanka.

²Corresponding author (E-mail) – dilanthag_12@yahoo.com.au

Abstract

Pueraria phaseoloides is a widely grown legume cover crop in Sri Lanka. Nitrogen fixation is performed by nodular inhabitants of this cover crop. We endeavored to isolate the whole array of diazotrophs colonizing the root nodules of this economically-significant cover crop. Four isolates were isolated by streaking a macerate of an active nodule from Pueraria phaseoloides and the identification of Rhizobial and Non-Rhizobial species was carried out using colony and cell morphology. One isolate from Pueraria phaseoloides (Sub 1), a gram negative bacterium contoured by a coccobacillus cell shape, (suggesting a likely non-Rhizobial identity), was a potent nodulator of Pueraria phaseoloides seedlings. A further three cultures (Sub 2, Sub 3 and Sub 4) too were able to nodulate Pueraria phaseoloides seedlings but were not as effective as Sub 1 in their nodulation potency. All four bacteria secreted to the extra-cellular medium cellulases suggesting their likely involvement in nodule formation and also showed characteristic patterns of motility to the chemoattractant proline. DNA extracted from Sub 1, Sub 3 and Sub 4 gave a PCR amplicon of the anticipated size (360 bp) using universal nifH primers, which indicated that the genetic foundation for the production of a unit of the nitrogenase enzyme, was found in the genome of these isolates. In summary, we have unearthed here, a strong, likely non-Rhizobial nodulator, in the legume cover crop Pueraria phaseoloides, and three other bacilli bacteria, perhaps Rhizobia, capable of efficient nodulation. Further characterization of these isolates using molecular biology tools is ongoing.

Estimates of the apparent net mineralisation of legume N and comparisons of the subsequent recovery of legume or fertiliser nitrogen by wheat

2016 INI, Biological N fixation for improved nitrogen utilisation, Feature Presentation

Mark Peoples¹, Tony Swan¹, Laura Goward¹, James Hunt^1,2

¹ CSIRO Agriculture & Food, Black Mountain Laboratories, GPO Box 1600 Canberra, ACT 2601, Australia; mark.peoples@csiro.au

² Current address: Department of Animal, Plant and Soil Sciences, La Trobe University, Bundoora, VIC 3086, Australia

Abstract

Results from experimentation undertaken near Junee in southern New South Wales, Australia indicated that concentrations of soil mineral (inorganic) nitrogen (N) measured just prior to sowing wheat in 2012 (0-1.6m) were 42 or 92 kg N/ha greater following lupin grown for either grain or brown manure (BM) than where the preceding crop in 2011 had been wheat or canola. The apparent net mineralisation of lupin organic N over the 2011/12 summer fallow was calculated to be equivalent to 0.11-0.18 kg N/ha per mm rainfall and 7-11 kg mineral N per tonne lupin shoot residue dry matter (DM), representing 22-32% of the total residue N estimated to be remaining at the end of the 2011 growing season. The higher concentrations of soil mineral N after the 2011 lupin treatments resulted in 55-80 kg N/ha more N being accumulated by the 2012 wheat crop (50-74% increase) compared to wheat following wheat and improved grain protein contents from ~9.8% to 12.4-13.6%. The additional N uptake was equivalent to 28% of the lupin residue N from 2011. The uptake of N by wheat grown after either the 2011 wheat or canola treatments was 25-30 kg N/ha higher (21-28% increase) when top-dressed with an additional 51 kg fertiliser-N/ha prior to stem elongation. This represented an apparent recovery of 47-59% of the fertiliser N.

Nitrogen contribution from forage legumes in maize farming system in West Timor, Indonesia

2016 INI, Biological N fixation for improved nitrogen utilisation, Feature Presentation

Evert Hosang1, Jacob Nulik1, Debora Kanahau1, Yandri Abi1 and Lindsay Bell2

1 NTT Assessment Institute for Agriculture Technology, Naibonat, Indonesia, Email: yulianeshosang@yahoo.co.id

2 CSIRO, 203 Tor St, Toowoomba Qld 4350, Australia.

Abstract

Maize is the important staple food crop cultivated in West Timor, Indonesia. However, maize productivity in West Timor is low (2.7 t/ha in 2010) compared to the national average (4.2 t/ha in 2010), due to low use of fertilisers. Integrating forage legumes into maize cropping systems has the potential to assist in improving maize nutrient supply and also provide high quality forage for livestock. The experiment was conducted on the island of West Timor, Indonesia to evaluate biomass production of herbaceous forage legumes in West Timor environment and to quantify potential nitrogen contribution from forage legumes in to maize in a rotation farming system. Butterfly pea, and Centro (both varieties) produced the most biomass (>6 t DM/ha), estimated shoot N was >150 kg N/ha and had the largest impacts on growth of a subsequent maize crop. Growing legumes and retaining their biomass on the field contributed significant nitrogen supply to the following maize crop, increasing N uptake by 30-50 kg/ha. Grain yields of a following maize crop were increased by 50% (1.4-1.6 t/ha) where legume was cut and removed, and by 90% (2.6-2.8 t/ha) where legume biomass was retained. This study has shown that Butterfly pea and Centro, can be used in legume-maize rotation farming system in West Timor to improve soil fertility and increase maize production.

Annual crop legumes may not mitigate greenhouse gas emissions because of the high carbon cost of nitrogen fixation

2016 INI, Biological N fixation for improved nitrogen utilisation, Feature Presentation

David F Herridge¹ and Philippa M Brock²

¹School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351 Australia, www.une.edu.au, david.herridge@une.edu.au

² Department of Primary Industries, “Tocal”, Tocal Road, Paterson, NSW 2421, Australia

Abstract

A large uncertainty in constructing grain cropping Life Cycle Assessments (LCAs) is the effect of a particular crop, or sequence of crops, on soil C stocks. We propose that the C cost of legume N₂ fixation, estimated to be ca. 20 kg CO₂/kg N fixed, will be expressed as reduced residue C returned to the soil and a possible net loss of soil C. Published pre-farm + on-farm greenhouse gas (GHG) emissions associated with N-fertilised wheat (60N) and canola (100N) and N₂-fixing field pea, grown in Australia’s southern grains region, were combined with modelled effects of the same crops on soil C stocks. When effects of the crops on soil C were assumed to be neutral, canola had the highest emissions at 840 kg CO₂-e/ha with field pea the lowest (530 kg CO₂-e/ha). When estimated changes in soil C were included in the LCAs, canola’s GHG emission were totally offset (-100 kg CO₂-e/ha), compared with a more than doubling of emissions for field pea to 1270 kg CO₂-e/ha. This is somewhat counter-intuitive to current thinking that the substitution of fertiliser N with legume fixed N is an effective strategy for GHG emissions mitigation and highlights the need for simple, accurate methodologies for determining net changes in soil C for individual crops.

New mobile, field based continuous-flow isotope ratio mass spectrometer system for automated denitrification studies

2016 INI, Feature Presentation, New methods of measuring reactive nitrogen in the environment

Daniel I. Warner¹, Clemens Scheer¹, David W. Rowlings¹, Peter R. Grace¹

¹Institute of Future Environments, Queensland University of Technology, Brisbane, QLD 4000 Australia, d.warner@qut.edu.au

Abstract

Terrestrial denitrification, the reduction of oxidized nitrogen (N) to nitrous oxide (N₂O) and dinitrogen (N₂), is considered the least well understood process in the global nitrogen cycle. This study introduces a novel continuous-flow isotope ratio mass spectrometer (IR-MS) system that can be deployed in the field and continuously measure N₂ and N₂O emissions. Utilizing the ¹⁵N gas flux method this system can provide a better understanding of terrestrial denitrification. The system was tested over 14 days on 2 different agricultural soils (vertosol and ferrosol) which were fertilized with the equivalent of 100 kg ha^-1 of N added in the form of KNO₃ where the N was 60 at.% ¹⁵N. Total gaseous N losses over the 14 day monitoring period resulted in 14.1± 0.53 kg ha^-1 and 5.7± 0.92 kg ha^-1 for the ferrosol and vertosol soils, respectively. These results clearly demonstrate the ability of the field based IR-MS to measure N₂ and N₂O emissions from denitrification under field conditions. This system has the potential to improve our understanding of terrestrial denitrification and improve efforts to reduce gaseous N emissions from agricultural systems.