IMPROVING THE EFFICIENCY OF FERTILISER UREA ON PASTURE WITH ONEsystem®
Bert Quin1, Allan Gillingham2, Stewart Spilsbury3, David Baird4, Maurice Gray5
1`Quin Environmentals (NZ) Ltd, PO Box 125-122, Auckland 1740, New Zealand
2Agricultural Research Consultant, 92 Waicola Drive, Palmerston North 4471, NZ
3 FOO Technologies, PO Box 892, Newry, Victoria 3859, Australia
4 VSN NZ Ltd, 8 Mariposa Crescent, Christchurch 8025, NZ
5 Maurice Gray & Associates Ltd, 1 Aotea Cres., Havelock North, NZ
Given the importance many farmers place on optimising the pasture response to urea, there has been surprisingly few attempts to improve its performance by the main fertiliser manufacturers and suppliers. In fact, the only efficiency-orientated modified urea sold in significant quantities in New Zealand is SustaiN®, which is granular urea treated with the urease inhibitor nbpt. This product was introduced by Summit-Quinphos in 2002. It is now estimated to comprise 30% of urea sold by Ballance Agri-Nutrients, or 20% of total New Zealand urea sales. SustaiN® is currently sold at a $50/t (8.5%) premium to standard granular urea.
This paper presents results from a field trial conducted on an irrigated dairy farm in mid-Canterbury, comparing granular urea with a new process – ONEsystem® – developed by Dr B. Quin and S. Spilsbury over the last 2 years in east Victoria in Australia and in New Zealand. The system uses prilled (micro-granular) urea, which is passed through a fine water spray containing the urease inhibitor nbpt during application. A nil-N control and 3 rates of each fertiliser (14, 28 and 42 kg N/ha) were applied to large plots (12 x 25) on four occasions after grazing during spring/early summer 2014
Results showed a substantial and statistically significant increase in extra dry matter (EDM) to N applied with the ONEsystem® compared to the pasture response from traditional granular urea, by a factor of 2.6 (± 0.5) averaged over the 3 application rates. For example, the EDM produced by 30 kg N/ha of granular urea could be produced with only 12.5kgN/ha applied as ONEsystem®. Conversion efficiency (kg EDM/kg N applied) increased from 10.2 with granular urea to 24.6 with ONEsystem®. Pregrazed plant N concentrations were also higher following ONEsystem® N application, meaning total N uptake was increased at least 3-fold compared with that resulting from N applied as granular urea.
These results have very significant positive implications for both the economics and environmental impacts of fertiliser N use in New Zealand. Preliminary results from a similar trial in the Waikato, and others conducted in Gippsland, Victoria also indicate very positive benefits (to be published elsewhere).
Granular urea is by far the most widely used nitrogen (N) fertiliser in New Zealand (NZ), with an estimated 750,000 tonnes (345,000 tonnes N) applied annually in 2014, most of which is applied to dairy farms. Anecdotal information suggests that approximately 50% is spread by contractors and 50% by farm owners and sharemilkers.
The main reason many dairy farmers choose to spread their own urea is not so much to save the spreading cost (which at typically $8-$12/ha is not high), but rather the importance they place on getting the urea applied at the best time to optimise pasture growth, generally 1-3 days after grazing.
Given the importance many farmers place on optimising the pasture response to urea, there has been surprisingly few attempts to optimise the performance of urea itself by the main fertiliser manufacturers and suppliers. Also, there have been very few comparisons of N fertilisers under grazing, as opposed to the use of small, non-grazed plot trials.
The fertiliser manufacturing industry and some advisors have long claimed that both ammonia volatilisation and other N losses from granular urea are low in NZ conditions, the implication being that no improvement can be, or needs to be, obtained. Edmeades (2005) stated that “measurements of the volatilisation losses have been made and they are typically small (between 0-5% of the N applied). However there are some „special conditions‟ where losses can be higher.”
A ratio of 10:1 kg extra dry matter (EDM) : kg N, frequently used as the default value by farmers and farm advisors in NZ, represents approximately 30% recovery of urea N for pasture containing 3.5%N. Ratios of 3:1 or worse can occur from January-August (Roberts and Thomson, 1989). Such low recoveries have been attributed by some to incorporation of urea N in soil organic N, despite the lack of evidence of increasing soil organic N levels on established dairy farms, as opposed to dairy conversions from forestry.
In 2002, the nbpt-treated granular urea product SustaiN® was introduced into New Zealand by Summit-Quinphos. Research findings on pasture in Ireland (Watson 2000) had demonstrated the effectiveness of the urease inhibitor nbpt in reducing ammonia volatilisation and increasing pasture response to urea. These findings were supported by field studies in New Zealand (Quin et al. 2003). Zaman et al. (2005) demonstrated the additional nbpt benefit in reducing nitrate leaching from fertiliser urea. Field trials conducted by Summit-Quinphos throughout NZ (Blennerhassett et.al 2007; 5 statistically analysed trials reported), and Ramakrishnan et al. 2008 (these 5 plus an additional 4 unanalysed trials reported), gave increases in N efficiency ranging from 1.6 – 72% (mean 28.2) compared to granular urea. Zaman et al. (2008) provided more detailed evidence for reductions in ammonia and nitrous oxide emissions, and nitrate leaching, from granular urea using nbpt.
Bishop and Manning (2011) reviewed scientific data on ammonia volatilisation losses from granular urea surface-applied to pastures in NZ and several other countries. They reported that losses in NZ ranged from 4.2 – 33.3% (similar to that found in other countries, and concluded that losses of less than 10% would only occur on highly acid soils with pH of 5.3 or less and with high cation exchange capacity. Few if any dairy farms operate at soil pH levels below 5.5.
Sustain® is now strongly promoted by Ballance Agri-Nutrients Ltd as being more effective than granular urea, for example ; „Use instead of urea unless 5-10mm of rain is guaranteed within 8 hours of applying N‟ (Ballance Agri-Nutrients „Key Products‟ 2015). Sustain® has been a very important step in the right direction, but is not the game-changer in efficiency that New Zealand dairy farming urgently needs.
Other improved-efficiency products or application processes have failed to gain significant market share, generally because of higher product and/or application costs or relative inconvenience of use by farmers and/or contractors. The Quinspread Technology spreading trucks produced an agronomically highly effective fluid of crushed granular urea immediately prior to spreading (Quin & Findlay 2009). However, the very high machinery and operating costs, combined with a narrow swath width of 10m, made for high application costs. This proved to be a significant barrier to adoption of the technology by farmers, despite the improved net profit.
This paper presents results from a trial conducted under grazed dairy farming, in which granular urea was compared with a new process known as ONEsystem®, developed since early 2013 by two of the authors (B.F. Quin and S. Spilsbury) in eastern Victoria and in New Zealand. ONEsystem® uses prilled (micro-granular) urea, wetted with a fine water spray containing nbpt during spreading. Results from similar trials conducted in the Waikato, NZ and Gippsland, Victoria, Australia will be published elsewhere.
The trial was conducted on large (12x25m) plots on an irrigated dairy farm near Hororata in mid-Canterbury, South Island, New Zealand. The soil is a Lismore stony silt loam, a Yellow Grey Earth classified as an Ustrechrept under USDA taxonomy. The pasture was ryegrass-dominant, with very little clover. Soil tests were quite adequate for vigorous ryegrass growth on this soil type, being Olsen 26, K 4, sulphate-S 11, and pH 5.6. The main source of fertiliser N used in the 6 months before the trial commenced was SustaiN® which was applied regularly by a spreading contractor. No fertiliser of any type was applied in the 3 months before the trial commenced.
The trial comprised a nil-N control, 3 rates of granular urea and 3 rates of the ONEsystem® processed prilled urea. Each treatment had 4 replicates. The accompanying nbpt and water applications were 2 gm/kg N (0.2%) and 50 L/ha respectively.
The 3 rates of each fertiliser (14, 28 and 42 kg N/ha) were applied to large plots immediately after grazing on four occasions during spring/early summer 2014. These rates were chosen both because they covered the normal rates used by farmers, and were predicted to most clearly define the N response curve. Pasture yields before and after grazing were measured on individual plots using a rising plate-metre, which was calibrated against weighed dry matter (DM) on several occasions (Figs 1- 3). Topsoil (0-75mm) samples were taken on 2 occasions (10 November and 2 December), immediately before the next fertiliser application, for ammonium-N and nitrate-N analysis. The very stony nature of the soil made deeper sampling impossible, given the limited time and resources available.
Results and discussion
Dry matter yields and N uptake
The responses in extra dry matter (EDM) produced per kg of N applied with ONEsystem® were much greater than those obtained with granular urea, and were very obvious to the naked eye (Fig.4). At the 30 kg N/ha application, urine-affected areas stood out clearly three weeks after granular urea (right plot in photo, Fig. 4), but were almost unnoticeable with ONEsystem® application of N (left plot in photo).
Statistical analysis of the dry matter yields demonstrated a highly significant difference in EDM produced per unit N applied, by an average factor of 2.6 averaged over the 3 application rates of granular urea (Fig.5). This massive differentiation in performance occurred on each of the measurement occasions (results to be reported elsewhere).
The DM measurements reported here (30 per plot) were made using a rising plate-meter (calibrated against mown DM yields) following a set zig-zag path, which naturally included some urine patches. However, the opportunity was taken to measure inter-urine patch DM production as well. The comparison on N responses on urine-affected and unaffected grazed areas will be reported on in a later paper.
A contributing factor to the much greater efficiency of ONEsystem® is the better coverage. At 30 kg N/ha, 400-500 prills are applied per square meter, compared to only 45 granules. This means that individual plants (numbering over 400/m2) automatically get access to a reasonably even supply of N (Fig.6); the 45 granules of urea cannot achieve this, even allowing for lateral movement of urea during dissolution.
Other likely factors include (in no particular order) –
- Greatly reduced ammonia volatilisation due to the addition of nbpt;
- A degree of foliar uptake, as the damp prills dissolve in situ on plant leaves in the same manner as fluidised fine particles of urea (Dewar et al. 2010);
- Reduced nitrate leaching and nitrous oxide emissions (under study).
The magnitude of the increases in pasture response efficiency found with ONEsystem® are not unique to this trial location and conditions. However, indications of a much lower plateau in DM with granular urea are more pronounced at this site than elsewhere. The increased herbage N% (Fig.7) demonstrates that N recovery with ONEsystem® was even greater than that indicated by DM increase alone. At this site, there was little clover and soil N supply was very yield-limiting. Control (nil N) pasture N levels were below optimum for ryegrass-dominant pasture.
Interpretation of soil mineral N data
Mineral N levels in the topsoil, measured on two occasions (10 November and 2 November) immediately before fertiliser re-application took place. Results from these two samplings were averaged. Levels of both ammonium-N and nitrate-N were significantly higher with ONEsystem® prills than with granular urea at the two higher N application rates (Figs 8 and 9).
As much greater pasture N recovery took place with the ONEsystem® prills, this indicates that much greater losses from the topsoil, either through nitrate leaching or gaseous emissions, had occurred with granular urea. As farm irrigation rotations were carefully controlled so as not to exceed water-holding capacity, it is likely that gaseous emission was the greatest N loss mechanism from granular urea.
The higher levels of soil nitrate-N and ammonium-N remaining in the surface soil after successive applications of the two higher rates of N applied as ONEsystem® would certainly result in higher residual pasture growth, but with a risk of nitrate leaching if a very heavy rainfall event occurred. Therefore, individual applications of less than 20 kg N/ha as ONEsystem® are likely to be optimum.
Tabular summary of advantages of ONEsystem®
Table 1. Advantages of ONEsystem® vs granular urea
ONEsystem® – eliminating N losses and inefficiencies with granular urea
|Granular urea loss/inefficiency||ONEsystem® answer|
|Many plants receive no N at all – insufficient number of particles||Use of prills means 10 times more particles – N supplied more evenly to individual plants|
|Little if any foliar uptake, missing out on this very efficient mode of N utilisation by the plant||The use of prills, wetted during spreading, ensures that most of the product landing on the leaf dissolves; significant foliar uptake occurs|
|Very susceptible to ammonia loss||Urease inhibitor minimises ammonia loss|
|Nitrate leaching is a big problem - too much N is available in the vicinity of individual granules relative to plant N uptake ability.||Faster, more even plant uptake via foliar uptake and better „coverage‟ (less distance between location of individual prills)|
Table 2. Advantages of ONEsystem® vs other technologies
ONEsystem® – eliminating drawbacks with other efficiency alternatives
|Drawbacks of alternative||ONEsystem® answer|
|High cost of product (most coated granular products) or application ( FPA, fluidising etc)||Cost of prills is similar to that of granules; application costs remain competitive|
|Lack of reliable benefit (affects both granular urea and „biologically activated‟ products)||Wetted prills optimise foliar uptake, nbpt minimises NH3 volatilisation|
|Scorching, caused by excessively heavy and rapid leaf uptake (liquid or fluidised urea)||The time required for wetted prills to dissolve on the leaf slows foliar uptake sufficiently to avoid scorching|
|Lack of placement control can cause direct waterway pollution due to excessively wide spread of granules||Prills give an even coverage, with an acceptably wide but well defined swath width, minimising direct entry into waterways|
|Difficulty in getting product applied by the contractor exactly when farmer needs it||Focused ONEsystem® contractors will synchronise with clients‟ grazing rotation|
The results from this field trial under grazing lead to the following conclusions –
- The efficiency of granular urea was extremely poor under the spring-early summer trial conditions, which were typical of irrigated Canterbury dairy farms.
- This efficiency is dramatically improved – by a factor of 2.6 in extra dry matter (EDM) per kg N applied terms averaged over the 3 rates of N application, or 3-fold on an N uptake basis – by using ONEsystem®.
- As an example, a total EDM of 1230 kg DM/ha above the nil-N 2000 kg DM/ha grown during spring/early summer required 4 applications of 30 kg N/ha as granular urea (120 kg N/ha total), compared to 4 applications of only 12.5 kg N/ha (50 kg N/ha total) as ONEsystem®. This represents conversion efficiencies of 10.2 Kg EDM/kg N for granular urea compared to 24.6 for ONEsystem®.
- These results have enormous implications for (a) reducing farmers‟ input costs and Overseer® N-loss outputs for farmers using ONEsystem®, and (b) Regional Councils‟ predicted nutrient loadings and water use planning.
- Overall, it is estimated that ONEsystem® achieved 90% recovery of fertiliser N applied, compared to 30% from granular urea.
Dr M-L Nguyen (Group ONE Consultancy Ltd) is thanked for his comments on the manuscript. This research was funded entirely by Global Sustainable Farming Ltd, 24 Bridge St, Hamilton 3216, New Zealand.
Ballance Agri-Nutrients Ltd website February 2015. „Key Products‟ page; “SustaiN”.
Bishop, Peter and Manning, M. (2011). Urea volatilisation: the risk management and mitigation strategies. Proceedings of the Workshop „Adding to the Knowledge Base for the Nutrient Manager‟. Massey University Occasional Report No. 24.
Blennerhassett, J.D., Zaman, M., Ramakrishnan, C., Quin, B.F. and Livermore,N. (2007). Summary of New Zealand SustaiN® trials to date. Proceedings of the Workshop „Designing Sustainable Farms – Critical aspects of Soil and Water Management‟. Massey University Occasional Report No. 20, ISSN 0112-9902, pp 111-116.
Dewar, K., Zaman, M., Rowarth, J.S., Blennerhassett, J.D. and Turnbull, M.H. (2010). The impact of urease inhibitor on the bioavailability of nitrogen in urea and in comparison with other nitrogen sources in ryegrass (Lolium perenne L.). Crop and Pasture Science, 61: 214-221.
Edmeades, D.C. (2005). „agKnowledge‟ Fertiliser Review Issue 15, October 2005. „Urea versus SustaiN‟, pp 1-2.
Quin, B.F., Braithwaite, A, Nguyen, M-L, Blennerhassett, J.D. and Watson, C.J. (2003). The modification of commodity P and N fertilisers to reduce nutrient loss to the environment. Proceedings of the Workshop “Tools for Nutrient and Pollutant Management – Applications to Agriculture and Environmental Quality‟. Massey University Occasional Report No. 17, ISSN 0112-9902, pp 115-121.
Quin, B.F., and Findlay, G. (2009). On-truck fluidisation and spreading – removing obstacles to achieving greater efficiency and environmental protection with fertiliser urea. Proceedings of the Workshop „Nutrient Management in a Rapidly Changing World‟. Massey University Occasional
Report No. 22, ISSN 0112-9902, pp 250-256.
Roberts, A.H.C., and Thompson, N.A. (1989). Use of nitrogen fertiliser for intensive dairy production. Proceedings of the Workshop „Nitrogen in New Zealand Agriculture and Horticulture‟, pp 42-55.
Watson, C.J. (2000). Urease activity and inhibition – principles and practice. Paper presented to „The International Fertiliser Society, London, Nov.28, 2000. The International Fertiliser Society, Proceedings No. 454.
Zaman, M., Blennerhassett, J.D., Quin, B.F. (2005). Increasing the utilisation of urea fertiliser by pasture. Proceedings of the Workshop „Developments in Fertiliser Application Technologies and Nutrient Management‟. Massey University Occasional Report No. 18, ISSN 0112-9902 pp 276-284.
Zaman, M., Nguyen, M-L, Blennerhassett, J.D., Quin, B.F. (2008). Reducing NH3, N2O and NO3-N losses from a pasture soil with urease inhibitors and elemental S-amended nitrogenous fertilizers. Biol. Fertil. Soils 44 (5): 693-705.
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