Lime Performance Report. By Lisa Miller Southern Farming Systems Date 25/9/2017

Transcription

1 1 Performance Report By Lisa Miller Southern Farming Systems Date 25/9/217

2 2 Contents Introduction... 3 Factors affecting lime quality... 3 Particle size determination... 3 Research objectives... 4 Method... 4 Results... 6 Wet and dry sieving Effective Neutralising Value Nutrient Content Discussion Neutralising Value Particle size... 2 Effective Neutralising Value quality effects on ph change within trials Moisture Micronutrients Difficulties farmers have in choosing limes Conclusion Acknowledgements References Appendices... 24

3 3 Introduction Factors affecting lime quality quality influences the amount and rate of ph change within soil. Both changes are important to growers who seek to get a fast return on their investment. The main factors reflective of lime quality include purity and particle size distribution (Scott et al, 1992). Neutralising Value (NV) is a measure of the lime s ability to neutralise acidity. Commercial limes are compared against pure lime (calcium carbonate) which has an NV rating of 1%. s with high NV have the potential for greater ph change. If lime has a low NV, more of the lime could be applied provided this cost is taken into account. Particle size affects the rate of change and is therefore an important factor to measure. The finer the lime, the more coverage and exposure to soil particles to create alkalinity which can then leach down the profile. only dissolves in acid soils. Coarser limes are slower because the surrounding soil ph is changed preventing further breakdown of the lime. Finer particles of lime also have the opportunity to physically be washed through macro-pores (Scott, et al, 2). Effective Neutralising value (ENV) is a calculation that allows for comparison of different liming materials by accounting for both NV of the lime and particle size. The rate of lime dissolution is also affected by its solubility. is regarded as being insoluble although the degree varies amongst types of lime. NSW DPI compared ph change of different lime types (Conyers et al, 1995) and found that soft limes created 2% more ph change compared to the model predicted for hard calcitic limes for their particle size over six and 12 months. This was thought to be due to differences in solubility. Dolomites because of their magnesium carbonate content are more insoluble and created approximately 15% less ph change for their particle sizes compared to that predicted. The initial effects of ph change created by the solubility of lime occurred within the first 12 months following lime application then after this time ph change fitted with predicted models of lime reactivity based on particle size. There are no current tests for lime solubility although the rates of change observed in the NSW DPI trials have been suggested as surrogate values for different lime types. Particle size determination There are different methods of determining particle size. It s important that these measures and methods are reflective of what happens within under field conditions. Conyers et al (1995) reports that particle size analysis on limestones undertaken using dry sieves do not extend reliably to < 5 micron or.5 mm. Sedimentation and laser diffraction are generally used to obtain particle sizes below 1 micron (.1 mm). Sedimentation involves placing particles of different size in solution and letting them settle. Large particles (i.e. sand) settle quickly and small particles (i.e. clay) settle more slowly. The density of the liquid changes as particles settle and can be measured using a hydrometer. The particle size distribution can be calculated. It is unrelated to wet sieving.

4 4 The fine fractions of lime generate electrostatic electricity causing clumping of finer particles so they are unable to pass through sieves. Wet sieving is thought to reduce electrostatic electricity and also wash finer particles off larger ones. The shape of lime particles is irregular whilst sieves have square apertures created with wire mesh and although lime could be fine it may not pass through. Washing could help shift particles to move through finer sieves but this too is likely with mechanical shaking in dry sieving. There is general agreement that the finer the lime the better but the degree of fineness needed for fast ph change is disputed amongst agencies and lime producers. The ENV calculation of lime reactivity in Victoria traditionally rates a particle size less than.3 mm as being 1% reactive, this value in NSW is.75 mm and in WA.5 mm. Whitten, (2) proposed standard lime segregations in WA should include particles sizes less than.1 mm to give a more accurate description of lime quality. Farmers use lime for different purposes, one for amelioration of acidity and one for prevention of soil acidity (maintenance liming). Amelioration of acidity is where farmers need lime to work quickly to recoup costs and prevent losses in plant production. Research objectives In 36 different pasture and crop trials in South West (SW) Victoria by SFS there has only been one trial that recorded a significant response (p<.5) to lime surface applied in its first year of application. This was achieved at a ph of 4.1 using acid sensitive barley. Monitoring potential lime movement indicates ph change down to 5 cm in the first year. Lack of lime responses can be caused by sufficient ph, acid tolerant species, nutrient constraints and subsoil acidity (Scott et al, 2). The lime used in SFS trials was a soft SW lime with a NV of 9% and ENV of 62.8%. limes dominate the Victorian lime market and distribution of particle size is generally no longer reported since the deregulation of the Victorian lime market in 24. In understanding what situations and timelines when lime responses occur, it s necessary to get an understanding of how lime quality also affects responses. SFS had different lime types tested by Nutrient Advantage to find out: the quality of limes accessible to Victorian farmers and how this may influence response. if wet sieving would be a better test to indicate lime quality compared to current testing methods involving test dry sieving if micronutrients within lime could replace fertiliser application. SFS will use the information to make recommendations on what descriptors, type of lime and testing of lime should be sought by growers to make decisions on lime purchase and what quality factors are important to include in lime calculators. Method SFS has had 15 different lime samples analysed to find out what information and tests are needed to indicate potential lime performance. quality information collected has been used in lime comparison calculations to determine the cost effectiveness of different limes spread. Samples were collected in July 216 and so samples varied in their moisture contents. Testing was performed by Nutrient Advantage soil testing laboratory at Werribee. Samples were collected by SFS or provided by the lime producer. In the case of limes 8, 5 and 6 samples had been stored out doors and had become saturated. Particularly lime sample 8 which being clay based became

5 5 clumpy. Samples were left to dry in a shed for several months before testing. Sample 8 was broken up by hand to try and get a more representative sample before being tested by Nutrient Advantage. received by the laboratory was split evenly into two samples. One for the standard testing of the bulk sample and one where both wet chemistry and dry chemistry where used. The standard testing done by Nutrient advantage involves particle size analysis using dry sieving (method code 4-71-RPSA). It was done on a known quantity of lime (2g) which was placed on top of a nest of 7 sieves with different apertures and shaken for 1 minutes on a mechanical sieve shaker. Sieved samples were then brushed into beakers for weighing. Table 1. samples tested Test ID Number Type Sample collection comments 1 GIP Hard Same pit as 14, but collected from a different depot 2 Magnesium Provided by lime producer 3 SA Provided by lime producer 4 SA Provided by SARDI 5 NSW Collected by SFS from depot sample in Gippsland 6 GIP Collected by SFS from depot sample in Gippsland 7 GIP Provided by lime producer 8 SW Collected by SFS from depot sample which was out doors and wet 9 SW Provided sample from lime pit depot, but was dry 1 SW Provided by lime producer 11 SW Provided by lime producer 12 SW Collected from pit by lime producer 13 SW Collected from pit by lime producer 14 GIP Hard Same pit as 14, provided by lime producer 15 SA Magnesium Provided by lime producer The sieve sizes used were: > 5. mm 2. to 5 mm 1. mm to 2. mm.85 mm to 1. mm.3 mm to.85 mm,.75 mm to.3 mm <.75 mm The Neutralising Value was tested according to their method code 4-54-WCalc using a titration method. is calculated as a percentage of acidity neutralised relative to pure calcium carbonate. Moisture % was calculated by air drying samples at o C until their weight stabilised. Calcium, Magnesium and impurities sodium, potassium, sulphur and other metal ions Copper, Iron, Manganese, Aluminium, Zinc, Boron were determined using test method 4-73-ICP2 via an Inductivelycoupled Plasma Mass Spectrometer.

6 6 The ENV of a limestone was determined using the following calculation: ENV = A + B + C Where A = %.85 mm x.1 x Where B = %.3 mm to.85 mm x.6 x Where C = % <.3 mm x A = %.85 mm is the percentage of particles greater than or equal to.85 mm. B = %.3 mm is the percentage of particles greater than.3 mm but less than.85 mm. C = <.3 mm is the percentage of particles less than.3 mm. In the second sample it was again split in two for additional testing. The dry sieving method was the same as that outlined above except two extra sieving fractions were included.125 to.3 mm and.75 to.125 mm. This replaced the standard sieve range of.75 mm to.3 mm. The same sieve sizes were also used in wet sieving. The NV using the same method as above was used to test each fraction range. There was no standard method of wet sieving of lime known to Nutrient Advantage. There is an AOAC (official method of analysis) method for wet chemistry determination of clay and sand analysis. Samples were placed into a nest of sieves and taken to the sink and trickled with deionised water. They were hand shaken for 5 minutes and visually checked for passing through the sieve. Samples were lightly brushed and washed into beakers and dried in the oven at 15 o C. Some samples contained approximately 1 litre of water which needed to be evaporated. Samples were then weighed to determine their weight and proportion of lime in each fraction size. Results The results from the bulk testing are shown in table 2 (Moisture content, NV and ENV) and table 6 (Analytes). sampling occurred in July and any limes not stored indoors had high moisture contents. s with moisture contents of 1% or greater included samples: 5, 6, 8, 9, 12 and 15. Table 2. Results of testing limes using standard testing from the bulk sample Sample Description Moisture % (Dry basis) ENV (Dry basis) ID 1 GIP Hard SA Dolomite SA SA GIP GIP GIP SW SW SW SW SW SW GIP Hard SA Dolomite

7 7 generally contains Calcium carbonate or Magnesium carbonate or calcium or magnesium oxides. Assuming the Calcium (Ca) and Magnesium (Mg) content is carbonate, Neutralising Value can be estimated from the Calcium and Magnesium carbonate content. Figure 1 shows the relationship between the laboratory measured and the estimated based on its calcium and magnesium percentage. The estimated equation used was (Ca% x (1/.) + (Mg% x (84.3/24.3)) Laboratory measured Estimated (Based on Ca and Mg being carbonate) Figure 1 Estimated versus laboratory measured. The products close to the trend line indicate that Ca and Mg are as carbonates. The products well below the red line indicate potential error or that the Ca and/or Mg are not present as carbonates. s which contain both Magnesium carbonate and Calcium carbonate are known as dolomites. Product 2 is clearly below the line which is a dolomitic limestone containing 1% Magnesium. Sample 15 was also a dolomitic limestone with 17% Magnesium detected and sample 4 contained 4% Magnesium. It is suspected that laboratory error was involved in the determination of the NV s of dolomite. The from each fraction size was collected to see if NV declined with fineness using both wet and dry sieving. Table 3 shows the differences in the NV taken from the dry sieving or wet sieving. The difference in NV was on average approximately 1 %. The greatest difference was in the sample 8 which was comprised as it had been saturated and contained 18% moisture.

8 8 Table 3. A comparison of dry and wet that was calculated as a proportion of each fraction size. Sample Sample Type ID Dry Size calculated as a proportion of each fraction size Wet Size calculated as a proportion of each fraction size 1 GIP Hard SA Dolomite SA SA NSW GIP GIP SW SW SW SW SW SW GIP Hard SA Dolomite It was thought that finer particles of lime may have lower NV because they become contaminated with other products, namely clay (alumina silicates) with lower or no neutralising capacity. With dry sieving, the NV of.3 to.85 mm particle range compared with the fines (<.75 mm) declined by more than 3% units in 6 samples (id numbers 5, 6, 7, 8, 1 and 15). It increased by more than 3% units in 2 samples (id number 2 and 13) and stayed approximately the same in 7 samples (id numbers 1, 3, 4, 9, 11, 12 and 14). Figures 2 to 9 show the differences in NV at different fraction ranges using dry and wet sieving. Products 1 and 14 were from the same Gippsland lime pit but sourced by different people. Figure 2 shows the limestone to be uniform in across all particle fraction ranges at about 9 to 94%. This reflects a uniform product which reflects the additional processing involving in preparation of hard limes. Neutralising Value of dolomites is shown in Figure 3 but it has been discussed that laboratory error may have accounted for the difference in NV between fraction ranges in samples 2 and 15. The largest decline was in the Gippsland lime product 7 where the NV (.3 to.85 mm) was 83 and the fines (NV<.75 mm) was 68. Aluminium % in the bulk product was detected at.38% and gives some support that this contamination has come from clay. From these results, it is not possible to generalise that the finest fraction will have a lower NV due to more clay contamination.

9 Product 1 Dry Sieve Wet Sieve Product 14 Dry Sieve Wet Sieve Figure 2. of Gippsland hard limes (Product 1 and 14) from dry and wet sieving Product 2 Dry Sieve Wet Sieve Product 15 Dry Sieve Wet Sieve Figure 3. of Product 2 and 15 (Dolomitic limes) from dry and wet sieving Product 3 Dry Sieve Wet Sieve Product 4 Dry Sieve Wet Sieve Figure 4. of SA soft limes Product 3 and 4 ( limes) from dry and wet sieving.

10 Product 5 Dry Sieve Wet Sieve Product 6 Dry Sieve Wet Sieve Figure 5 of SA soft limes Product 5 and 6 ( limes) from dry and wet sieving Product 7 Dry Sieve Wet Sieve Product 8 Dry Sieve Wet Sieve Fig 6 of SA soft limes Product 7 and 8 ( limes) from dry and wet sieving. 1 Product 9 Dry Sieve Wet Sieve 1 Product 1 Dry Sieve Wet Sieve

11 11 Figure 7 of SA soft limes Product 9 and 1 ( limes) from dry and wet sieving Product 11 Dry Sieve Wet Sieve NV % Product 12 Dry Sieve Wet Sieve Figure 8 of SA soft limes Product 11 and 12 ( limes) from dry and wet sieving Product 13 Dry Sieve Wet Sieve Figure 9 of SA soft limes Product 13 ( limes) from dry and wet sieving.

12 12 Wet and dry sieving In the hard limes, Product 1 and 14 the wet sieving has increased the percentage of fine particles by 15 and 11%. The fine particles clump in the dry sieving and wetting reduced the.125 and.75mm fractions. The distribution of particle size in mined and crushed hard lime was approximately normally distributed for dry sieving. Both products had virtually no fraction sizes greater than 2 mm. In the dolomite, Product 2 was presumably hard, crushed mined product which particles size peaked at.125 to.3 mm. Wet sieving made only a small improvement (5%) in the amount of lime <.125mm (see table 3). However in the dolomite, Product 15 which was evenly distributed with the dry sieving, had a huge increase in the <.75 mm fraction under wet sieving. It s suspected the particles may have broken up with washing as there was a small percentage of large fraction sizes remaining after wet sieving. This product contained 17% moisture which would have helped the product break up. Product 8 was also a very wet product when sampled and had formed a loose clay product. It seems it and some other products have broken up during wet sieving as the coarse particles under wet sieving have dramatically reduced. In the soft limes, wet sieving has increased the wet sieved fraction of.75 mm in all limes except for product 7. Table 4. A comparison of wet and dry sieve fraction sizes less than.125 mm from different limes. Id Wet sieve fraction % Dry Sieve fraction % Difference between Wet vs Dry sieve 1 GIP Hard SA Dolomite SA SA GIP GIP GIP SW SW SW SW SW SW GIP Hard SA Dolomite

13 13 Product 1 Product Figure 1. Fraction distribution of Products 1 and 14 from dry and wet sieving Product Product 15 Figure 11. Fraction distribution of Products 2 and 15 from dry and wet sieving Product Product 4 Figure 12 Fraction distribution of Products 3 and 4 from dry and wet sieving.

14 14 Product 5 Product Figure 13 Fraction distribution of Products 5 and 6 from dry and wet sieving. Product 7 Product Figure 14 Fraction distribution of Products 7 and 8 from dry and wet sieving Product Product 1 Figure 15 Fraction distribution of Products 9 and 1 from dry and wet sieving.

15 15 5 Product 11 5 Product Fig 16 Fraction distribution of Products 11 and 12 from dry and wet sieving. 5 Product Figure 17 Fraction distribution of Product 13 from dry and wet sieving.

16 16 Effective Neutralising Value In table 5 the ENV from the dry and wet sieving methods are compared. ENV improved with wet sieving, in most samples except for 5 samples which included both hard limes (1, 2, 37 and 14). The samples which had the most change coincided with soft limes. It did this by changing the proportion of fractions assigned to the.3 to.85 mm and <.3 mm fraction ranges. A SA lime sample (id 3) had the highest ENV recorded of 74% with dry sieving. Most SW soft limes, excluding sample 8, had an ENV of approximately 5%. Table 5 Calculated ENV from wet and dry sieving techniques. Test Description Effective Neutralising Value % ID Wet Sieve ENV Dry Sieve ENV % Difference between Wet & Dry ENV 1 GIP Hard SA Dolomite SA SA GIP GIP GIP SW SW SW SW SW SW GIP Hard SA Dolomite Comparison of limes using different models s were compared of a dry sieved basis and bulk and ranked using and calculations where was multiplied by the sum of discounted fraction sizes (see table 7). Discount factors are shown in table 6. The NSW lime (FM7) is generally regarded as the best commercial available lime and test results are also shown, although it was not tested as part of this project and is for comparison purposes only. Table 6 Discount factors used in different lime comparison calculations for different particle sizes. Vic. ENV calculation NSW DPI lime comparison calculator 23 for Product efficiency (PE) WA DAFF calculator & the Soil Quality online Comparison Calculator Efficiency of Product (EP) <.3 mm = 1%.3 to.85 mm = % >.85 mm = 1% <.75 mm = 1%.75 to.15 mm = 58%.15 to.25 mm = 42%.5 to 1 mm = 34% 1 to 2 mm = 22% > 2 mm = 12% <.125 mm =1%.125 to.25 mm =1%.25 to.5 mm = 1%.5 to 1 mm = 5% > 1mm = 2%

17 17 ENV, EP and PE calculations ranked the top 3 limes the same. considers only component of quality but was in agreement for the top 2 limes. Table 7. Analysis of different limes tested by Nutrient Advantage from sampling in July 216 Fractions 1 Gip Hard 3 SA 4 SA 5 NSW in Gip 6 GIP 7 GIP 9 SW 1 SW 11 SW 12 SW 13 SW NSW* FM7 Marulan > 5. mm mm mm mm mm mm mm <.75 mm E (Dry) NSW PE WA EP rank ENV Dry Rank NSW PE Rank WA EP Rank

18 18 Costs spread per tonne of each lime were also calculated based on transport to Lake Bolac. The FM7 lime may be the best lime but it is not the most cost effective due to cartage of approximately 8 km. The cost of effectiveness was calculated using the following formulae (1 ENV) x Cost/t spread. Moisture percentage is not taken into account in these calculations as lime is expected to be purchased dry in summer or early autumn. Table 8. Cost effectiveness of different limes tested by Nutrient Advantage from sampling in July 216 Fractions 1 Gip Hard 3 SA 4 SA 5 NSW in Gip 6 GIP 7 GIP 9 SW Moisture %.1% 9% 3% 14% 1% 5% 13% 2% 3% 1% 9% Cost $/t $3 $25 $21 $34 $26 $18 $18 $22 $28 $39 Cost $/t spread $9 $52 $53 $79 $39 $31 $29 $36 $45 $13 1 SW 11 SW 12 SW 13 SW NSW* FM7 Marulan Cost $/t effectiveness based on ENV Rank Cost $/t effectiveness based on ENV $141 $74 $13 $199 $87 $75 $53 $68 $78 $

19 19 Nutrient Content The laser diffraction has determined no worthwhile amounts of micronutrients. No detectable levels of Zinc or Copper were found in any of the samples. The only detectable sample of Boron was found in number 15 with.11 % and was not enough to treat deficiencies or provide toxicities. The results with ND (Not detectable) are values with less the.1% because the nutrient amount was below the level of possible detection in the sample. The acid soils in the high rainfall zone are likely to have more than adequate Iron and Manganese so these values are of little benefit. The presence of iron and aluminium was more likely a consequence of soil contamination in the samples. In terms of amounts supplied at.1% Manganese 1 t/ha of lime would supply 1 g of Manganese, which is inconsequential to either deficiency or toxicity. Generally only the macronutrient levels (Ca, Mg, Na, S, K) are reported in standard reports but not phosphorus. The Calcium % ranged from 26 to % in limestones. Gypsum products used by growers to ameliorate sodicity often contain approximately 15 to 2% Calcium. Table 9. The percentage of different elements detected in different lime bulk samples. test number & Mag- Potassium Sulfur phorus Phos- type Calcium nesium Sodium Iron Manganese Aluminium 1 GIP Hard ND.17 ND ND.48 2 SA Dolomite ND.62 3 SA ND.58 4 SA ND.31 5 GIP ND.59 6 GIP ND.55 7 GIP ND.38 8 SW SW ND.26 1 SW SW SW ND ND ND SW ND GIP Hard.27 ND ND ND ND SA Dolomite ND.9 Discussion Neutralising Value Neutralising value percentage is the equivalent to the concentration active ingredient. The higher the NV, the more hydrogen ions consumed in chemical reactions. The range in NV of bulk limes tested, excluding those samples which were dolomites and very wet samples was 67% to 92% (table 2). Although limes with high NV s are desirable (> 8%), limes with low NV can still be used by producers, simply more of the lime needs to be applied to create the same soil ph change as a lime with higher NV. This is worthwhile if the cost of the additional lime and extra cartage and spreading costs are taken into account and is cheaper.

20 2 The NV based on individually testing each fraction size showed little difference to their bulk NV. Slight increases were recorded but this may come from an accumulation of small errors in comparison to testing one bulk sample. This study investigated if there was variation in NV across particle fraction sizes due to contamination and if this negated any benefits of choosing fine limes. Contaminates of lime can include soil and fine particles of clay (alumina silicates) and other calcium compounds like gypsum. Pure gypsum has 23.3% Calcium and 18.6% Sulfur. The maximum Sulfur% identified in laser diffraction of limes was generally below.1% which indicated little gypsum presence. In 6 limes, declined in the finest sieved fractions (<.75 mm) indicating clay contamination which was supported with these limes generally showed high aluminium levels determined through elemental analysis. Some of these soft limes are clay based but the effect of clay contamination in the fine fraction was not consistently seen in 6 other soft limes tested. The sum of Calcium plus Magnesium expressed as carbonate correlated well with NV determined by titration tests except for those products containing higher levels of magnesium (Figure 1) and was a useful technique to identify potential testing errors or contamination. The NV of dolomitic limes tested was likely the result of laboratory error. Magnesium carbonate within limes is more insoluble than calcium carbonate and generally requires greater quantities of acid solution to achieve completion of acid neutralisation. It s suspected that not all of magnesium component of the limestone was consumed by the acid solution which resulted in lower NV s recorded than what was estimated from their calcium and magnesium content. Particle size Particle size influences the rate of which the lime is dissolved. The finer the lime the faster the lime is at reacting and moving through the soil and the more coverage and contact with soil to neutralise acidity. Farmers when ameliorating soil acidity desire lime to work quickly so they can recoup their capital investment and avoid further yield losses. Farmers looking to prevent soil acidity and maintain current ph levels, don t require the response to be as fast as they will not be losing yield and could theoretically purchase a slightly coarser lime if it was cheaper. Nutrient Advantage suggests limes should ideally have greater than 5% of material that passes through a.3 mm sieve. Using this measure of quality with dry sieving, four of the limes tested would have been considered to have ideal size (Id numbers 2, 3, 7 and 11). There were also four limes tested that recorded in excess of 1% of particles sizes above 5 mm (8, 9, 1 & 11), two of these were wet and so particles had clumped together, but the other two were not which is a reflection of poor screening practices. Chris Gazey, research scientist DAFWA estimates particles greater than 5 mm take approximately 2 years to breakdown (personal communication). It s interesting to note that product 11 appeared to be one of the finest limes, according to Nutrient Advantage s ideal lime definition but it also contained one of highest amounts (21%) of coarse lime above 5 mm. Particle size distributions of limestones and dolomites depend on the nature of the original material and the crushing and sieving practices of lime producers (Merry, 1995). s are not homogenous in particle size unless processed to be. There is quite a range in the proportions of particle sizes and some limes may be blended products. Under the now defunct Victorian and Agricultural and Veterinary Chemicals (Fertilisers) Regulations 1995 the ENV calculation used to calculate the lime s effectiveness valued lime material greater than.85 mm as 1% reactive. The VLPA only reports fraction sizes above 1. mm to encourage good processing but

21 21 there is a vast difference in lime quality of 1 to 2 mm and lime greater than 5 mm which may not be accounted for. DPI NSW discounts lime above 2 mm by a factor of 12% and lime 1. to 2. mm as 22%. particle size is normally determined by dry sieving although this method is known to be flawed in determining fine particles (<.1 mm) due to electrostatic forces causing clumping. Wet sieving is thought to lubricate samples and reduce friction forces. It may also help move lime which is fine but irregular in shape through square aperture mesh holes in sieves. Results showed that wet sieving increased the percentage of fines (less than.125 mm) in all samples and types of lime except for sample number 7. The samples were only tested once and so potential errors in wet sieving cannot be commented on. Wet sieving would saturate the lime more than what would be experienced with normal rainfall within the field. It would not be expected to dissolve lime because lime is regarded as insoluble at ph 7. and so was not a factor. The biggest increases were in samples that had particularly high moisture contents (id numbers 8 and 15). Gentle trickling through wet sieving may have inadvertently broken up clumps of lime. Wet sieving of lime is a difficult process. Whitten, (2) who used wet sieving in his PhD complained of physically losing large amounts of lime from some samples. He also had concerns about the physical breakup of the soft limes in agitated solutions or extended sieving times and suggested that this would be unlikely to represent what occurs in field conditions. Likewise the WA survey of limes used hand sieving because of the soft nature of many lime materials received (Gazey and Gartner, 29). It mentioned that extended sieving of some types of lime increases the percentage of the finer fractions by abrasion with larger particles. Wet sieving in hard limes (1 and 14) would not be expected to break up particles because of its harder nature but increases in fines, was approximately 11% to 15%. Gains are presumably from decreasing electrostatic forces and washing off the fines from larger particles. Although these levels of increases were not seen in all limes, there is a trend to indicate that wet sieving determines more of the fine fraction. This is important if farmers are trying to base purchasing decisions on particle size and potentially ENV as the fine fraction is more valuable as it drives faster responses. Whilst wet sieving is generally regarded as more accurate measurement of the fine and more valuable fraction it is more labour intensive to measure and therefore more expensive. Nutrient Advantage has made a commercial decision to cease testing any limes due to the low volume they receive. Commercial laboratories that will measure particle size via wet sieving are difficult to find and it seems a standard methodology is not available (personal communication Paul Kennelly, Nutrient Advantage Laboratory Manager). Effective Neutralising Value ENV is a calculation used to compare limes based on NV and particle sizes. The calculation is no longer supported by the VLPA who feel it underestimates the value of their lime. Anecdotally lime id 4 has been reported by Brian Hughes, Principal Consultant, PIRSA to perform better than its dry sieving ENV would suggest and so ENV with wet sieving is generally reported by the lime producer. In this test its ENV increased from 42% to 68%. The highest ENV (dry sieving) recorded was for a SA soft lime of 71% in bulk testing. The average ENV for SW Victoria soft limes excluding sample 8 was 5% from the bulk test and 66% from wet sieving. This suggests that the maximum ph change from SW Victorian limes will not be achieved within the first 12 months to two years. This may partly help explain why only one response to lime was seen in the first year of 3 crop and pasture trials. If an extra 2% efficiency was added for soft limes, then SW limes that averaged % reactive under dry sieving would go to a rating of 48% which is hardly much better. It is argued by lime producers and contract

22 22 spreaders that you cannot practically spread limes less than.75 mm and so should it not be given the highest rating. In NSW F7 lime which has 7% less than.75 mm or 75 micron is handled routinely in commercial spreading operations. Realistically in Victoria it is unlikely that the lime industry would ever accept.75 mm as a level of fineness to aspire to. It would likely require them to move away from processing just using jaw crushers to also using ball mills which grind lime into a finer product and would add to processing costs. Comparison of limes using different calculations Whilst different calculators rate the fineness of lime differently, it is apparent that fine fraction of lime could not be determined accurately via dry sieving and so current fraction size ratings of less than.3 mm as part of the ENV calculation seem sufficient. Generally the calculations that accounted for fineness ranked limes relatively similarly and the same for the top 3 limes where the value of the lime was heavily weighted towards its fineness. In the coarse fraction of lime (above 1 mm), there were few segregations of discounted particle sizes and so limes which may have had poor screening practices and had high fraction amounts above 5 mm were not rated differently from those with fraction sizes of 1 mm to 2 mm fractions. This allowed one of the SW Victorian limes to rank the most cost effective lime when it contained over 2% of its lime above 5 mm. quality effects on ph change within trials The increase in ph due to liming has been found in numerous trials to be a function of average particle size (Scott et al, 1992 and Conyers et al, 1996). Simply put, the finer the product, the more ph change that will occur in the first 6 months. In NSW DPI trials the microfine lime achieved ph(ca) change from an initial starting point of 4. to 6.5 and soft limes (coralline an earthy limes) achieved ph changes to at least 5. after 6 months. A ph of 5. throughout the top 1 cm of soil is generally good enough to remove most constraints to acidity for many plant species. These trials, like most other lime evaluation trials have been done using incorporated lime to depths of 1 cm. There is evidence of rapid initial effect of limestone changing ph in the first 6 months but then slowing as ph increases which reflects its solubility. is only soluble in acid conditions and the breakdown of lime slows at ph > 5.4 (Whitten, 2). In SW SFS trials, the lime has been surface applied with little or no soil disturbance. The ph changes achieved have occurred quickly within the top 5 cm and have ranged from 5. to 6.4 depending on soil type and initial soil ph. With coarse particles of surface applied lime, it is likely they only partly react within 3 years and as a result the ph change is not great enough to allow leaching of enough alkalinity to ensure all the acidity within the top 1 cm is treated or from 1 to 2 cm. The soil ph(ca) required to achieve leaching of alkalinity (bicarbonate ions) occurs above 5.5. With coarser limes and delayed ph change, acidity constraints beyond 5 cm will not be quickly removed. Incorporation of lime would help address this, putting lime where it s needed. This adds another cost possibly $5/ha which could be applied as part of a fodder or crop rotation. This extra cost could also be spent on purchasing a finer lime. There is reasonable fineness in some SW limes but their value can be undone by them also containing large quantities of coarse particles. Moisture Moisture is another factor that can be considered when calculating lime costs and rates as it means less actual liming material per tonne. However, generally limes purchased in summer will be dry. Sample 8 which contained 17% moisture is an example of what could happen to farmer s lime if it sits out in the paddock for six months before spreading. The lime becomes clumpy and loses its processing advantages.

23 23 Micronutrients Testing showed all limes had non-detectable or non-useful amounts of trace elements (Cu, Zn, Mn, Bo, Fe) and are not worth testing for. Difficulties farmers have in choosing limes quality varies across different limes and so testing is important. Producers have difficulties choosing limes, because access to timely independent information about different limes quality is not readily available. Most producers and agronomists are wary of potential bias from samples taken by lime producers. Some agronomists will collect samples from delivered lime to get an idea of what lime to purchase in the following year, even when they know that the limes are unlikely to be homogenous across the pit. It is very difficult for growers to make informed decisions on lime purchase without up to date testing data. At present, agronomists chose lime pits based on limited testing and trust of the lime producer. Having a range of particle sizes tested gives the farmers and agronomist s information to make decisions about the quality of the lime and whether it will be suitable for maintenance programs or for fast amelioration of soil acidity. ENV type calculations are a useful way to allow farmers to compare limes but more sieve sizes above.85 mm should probably be used to discount coarser fractions. Whilst producers commonly ask, Which is the best lime, this may not be the most cost effective lime depending on their location. Cartage therefore needs to also be considered. A lime which is more cost effective but lower in quality could have more applied to compensate. Whitten (2/21) found both lime rate and fineness can influence lime movement because presumably they create high surface ph which means there is more dissolved alkalinity to leach down the subsurface. Conclusion Dry sieving does not accurately determine the fine component of lime but wet sieving is not representative of what happens in undisturbed field conditions. It is also a technique that commercial testing laboratories are unlikely to adopt because it takes longer to complete and is more costly. With dry sieving, NSW DPI product efficiency calculations that value lime fractions less than.75 mm at 1% will underestimate the fine lime component but ENV and WA Efficiency of product calculations that value lime fractions below.3 mm and.5 mm respectively at 1% reactivity will capture the finer particles and so are also useful for comparisons. Neutralising value alone is not a useful way to compare limes as it only considers one part of quality and ignores the rate at which acidity is neutralised. The coarse fraction segments in ENV and WA EP calculations are not enough to properly value lime and additional sizes, for example 1 to 2 mm, > 2 mm and > 5 mm should be considered to be included to discourage poor screening practices. does not contain sufficient micronutrients to replace fertiliser application. If farmers desire a fast response to lime and are surface applying lime, then seek to purchase the fineness most cost effective lime available and consider applying a higher rate to access finer material and increase lime movement.

24 24 Acknowledgements Thanks to the support of the Corangamite Catchment Management Authority and GRDC and Department of Agriculture Food and Forestry. Thanks to Paul Kennelly, Nutrient Advantage for testing our lime samples. Thank you to the information generously shared by Brendan Scott, Charles Sturt University, Brian Hughes, PIRSA and Bruce Shelley, AgVic. Thank you to the producers and Trevor Tovey (VLPA) for providing lime samples. References Conyers M K, Scott B J, Fisher R and Lill W (1995) Predicting the field performance of twelve commercial liming materials from southern Australia. Fertiliser Research 44, Gazey C and Gartner D, 29. Survey of Western Australian agricultural lime sources. Dept. of Agriculture and Food. Bulletin 47. ISSN Hollier C In Acid Soil Action. Land and Water Resources Research & Development Corporation. Merry R H, Hodge T J V, Lewis D C and Jacka J (1995) Evaluation of liming materials used in South Australia. In: Plant soil interactions at low ph, Kluver Academic Publishers, Netherlands. Scott B J, Conyers M K, Fisher R and Lill W (1992) Particle size determines the efficiency of calcitic limestone in amending acidic soil. Australian Journal of Agriculture Research 43, Scott B J, Ridley A M and Conyers MK (2). Management of soil acidity in long-term pastures of southeastern Australia: a review, Whitten M (2) PhD thesis. Amelioration and treatment of agriculturally generated subsurface acidity in sandy soils in Western Australia. The University of Western Australia. Whitten M (2/21) Comparing size in lime. Journal of the Department of Agriculutre, Western Australia, Series 4. 41, 1-12 Appendices Table 7 Additional data for each lime tested

25 25 Sample Name 1 GIP Hard 2 SA Dolomite 3 SA 4 SA 5 NSW Fractions Dry sieve Fraction % Dry Sieve Wet sieve Fraction % Wet Sieve 1 Dry Sieve 1 Wet Sieve Bulk Dry sieve > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm

26 26 Sample Name 6 GIP 7 GIP 8 SW 9 SW 1 SW Fractions Dry sieve Fraction % Dry Sieve Wet sieve Fraction % Wet Sieve 1 Dry Sieve 1 Wet Sieve Bulk Dry sieve > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm

27 27 Sample Name Fractions Dry sieve Fraction % 11 SW 12 SW 13 SW 14 GIP Hard 15 SA Dolomite Dry Sieve Wet sieve Fraction % Wet Sieve 1 Dry Sieve 1 Wet Sieve Bulk Dry sieve > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm > 5. mm mm mm mm mm mm mm <.75 mm