PROJECT RESULTS

Evaluation of the Addition of Commercial Fertilizer to Swine Manure on Transportation Cost, Yield Performance and Nutrient Accumulation

ARDI Project:

Total Approved:

Date Approved:

Project Status:

Peter Grieger

Agricultural Management (AGMGT) Ltd.

Winnipeg, Manitoba  R3Y 1S7  Canada

#98-223

$17,475

March 26, 1999

Completed January, 2001

Table of Contents:

• Background and Objective
• Procedure and Project Activities
• Results and Discussion
• Conclusions

Background and Objective:

Nitrogen is generally considered to be the most valuable plant nutrient in manure and as a result it is often used as the base element in determining manure application rates.  The result of nitrogen based application rates has on occasion shown that phosphorus and potassium accumulations occurred to various degrees depending on crop rotation.  Elevated phosphorus levels are of particular concern in soils subject to erosion, which when relocated may contribute to surface water pollution.  There is also potential for soluble phosphorus to leach through the root zone affecting groundwater quality.  The likelihood of phosphorus and potassium accumulation in the soil is significantly reduced by supplementing the nitrogen content to levels consistent with crop requirements based on manure application rates tailored to meet the phosphorus and potassium requirements of the crop.  The aim of developing the proposed process is in anticipation of changes requiring that manure application be based solely on meeting crop nutrient requirements.  Under these circumstances, swine manure would be blended to nutrient levels and applied at rates consistent with total crop nutrient requirements.

Perception within the agricultural industry is that swine manure represents an inconsistent source of nutrients for crop production thus requiring supplemental nutrients to be added to achieve yield targets.  As a result, the value of swine manure to grain producers is generally not as high as the actual value.  Due to the large volumes of material to be handled, the cost of transporting swine manure based on nitrogen value is significant.  Currently, the value of the nitrogen limits the transport distance to approximately 1½ miles in order to be economically advantageous.  In comparison, it is economically feasible to transport liquid fertilizer (28-0-0) approximately 300 miles. The blending of swine manure with commercial fertilizer to provide a homogeneous product that meets specific nutrient levels will ultimately result in a marketable product readily accepted as a source of nutrients for grain production. The increased demand and willingness to pay for this product based on total nutrient value and the organic nature of the blended product will permit greater transportation distances.  Through the development and testing of this process, it is hoped to calculate the feasible transport distance for swine manure which would permit siting of intensive livestock operations in remote, sparsely populated areas that would otherwise remain inaccessible due to shortages in arable acres and increased production costs.  This application would provide a feasible option to producers located in densely populated areas where odours from spreading operations is a large concern or accessibility to spreading land is limited.

The objective of this study was to evaluate the use of commercial fertilizers to supplement the nutrient content in swine manure in order to make one-pass application for crop requirements possible.  Through the efficient use of available nutrients and predictable nutrient levels it is hoped to demonstrate that swine manure is a valuable source of nutrients for crop production.  In testing the process, it was evaluated whether this technology would reduce the risk of accumulation of phosphorus and potassium in the soil.

Procedure and Project Activities:

Phase I – Test Plots at Martin Farms, East Selkirk

Phase I was initiated in the spring of 1999 on a wheat and canola field at Martin Farms in East Selkirk, Manitoba.  Soil nutrient levels were measured on the selected fields to establish background levels for use in determining crop nutrient requirements.  The initial soil test results from the parcels of land where the field trials were conducted indicated the following nutrient levels in the top 12” of soil, Table 1.  Samples were collected as a representation of the entire field using a hand probe on a random basis.

Table 1.  Soil Nutrient Levels Prior to Field Trials

Manure nutrient availability was measured from a Slurrystore structure.  Testing was done prior to agitation at one foot increments within the storage to determine nutrient distribution in order to demonstrate the variability of nutrient content.  The manure was also sampled at one foot increments following 14 hours of agitation to determine the degree of uniformity of nutrients that can be achieved utilizing agitation.  The agitation mechanism utilized was equipped with a cycle timer which automatically repositioned the agitator ensuring that thorough mixing of the entire structure was achieved.  The test results from the agitated manure were used in establishing the average available nutrients.  The available nutrients were used in calculating the application rates and blending requirements.  A summary of the nutrient levels measured prior to agitation and following agitation have been provided in Table 2 and Table 3 respectively.

Table 2.  Nutrient Levels of Swine Manure Prior to Agitation

Table 3.  Nutrient Levels of Swine Manure after Agitation

Field trials using AC Barrie wheat and Hyola 401 canola were established in approximately two acre plots.  The trials included plots fertilized with manure amended with commercial fertilizer, commercial fertilizer only and a check strip for comparison.  Target nutrient application rates based on soils analysis and producer preference for the wheat were 80 lb/acre nitrogen, 17 lb/acre of phosphorus and zero lb/acre of potassium.  Target levels for canola were 100 lb/acre nitrogen, 17 lb/acre of phosphorus and zero lb/acre of potassium.

Manure for the trials was applied using a tractor drawn tanker equipped with injectors spaced at 42” and 48” centers.  A portion of the field was used to calibrate the application equipment in order to attain the desired application rate.  Based on the soil test results and manure nutrient levels, supplemental commercial fertilizer was added to each tank separately in order to achieve the desired nutrient level.  The tanker was equipped with an internal agitator to ensure mixing of the supplemented nutrients with the manure.

In order to achieve the target phosphorus level on both the wheat and canola plots, it was calculated that 3500 imperial gallons of manure had to be applied per acre based on the assumption that 50% of the phosphorus in the manure is available in the first year.  Based on the industry adopted standard of 50% nitrogen availability in the first year, the supplemental nitrogen required to meet target application rates was calculated.  Supplemental nitrogen in the form of 28-0-0 was blended with the manure to provide an additional 3.6 lb/acre on the wheat trial and 21.1 lb/acre on the canola trial.  Samples of the manure in each tanker that was applied were collected and analyzed in order to establish the average applied nutrient levels, Table 4.

Table 4.  Nutrient Application Rate of Amended Swine Manure

During the growing season, plant growth including emergence, growth uniformity and levels of maturity were visually monitored.  During the growing season the East Selkirk area received 6” of rain over a short period of time.  As a result of localized flooding a portion of the canola plots were affected.  The canola plot fertilized with commercial fertilizer was the most affected, resulting in reduce plant density over approximately 25% of the plot.  Aside from the reduced plant population, the remaining growth did not appear to be any more stressed than any of the other plots.

Germination and emergence were consistent between all plots in both canola and wheat.  At the two to three leaf stage it became evident that the wheat plot fertilized with the amended manure had a distinct colour banding in the plant canopy running parallel to the direction of manure application.  As this difference did not appear in either the commercially fertilized plot or check plot, this anomaly was attributed to the manure application equipment.  It was determined that the colour difference was due to the wide injector spacing, resulting in a poor distribution of nutrients.  Plant growth directly behind the injector where nutrient accumulations were greatest was a deep green.  The colour of the canopy became lighter as the plants got further away from the band of nutrients.  This distinction remained prevalent throughout the entire growing season affecting crop maturity.  This distinction was not evident in the amended manure plot on which the canola was grown.  This most likely was due to the intertwining of the plant canopy which occurred on all of the canola plots.

Although it was not evident during the development and heading stages of the growth cycle of the wheat and canola plots, it became readily evident that the check plots reached maturity significantly sooner than the fertilized plot.  This is attributed to the fact that plant vigor was not as great due to the stress imparted by limited nutrient availability.

Harvest of the plots was completed on September 24, 1999.  A weigh wagon was utilized to measure the yield from each plot.  Yield results have been summarized in Table 5.

Table 5.  Yield Summary, lb/acre

As indicated by the yield measurements, the amended manure plots out yielded the check strips as expected, as well as, the commercially fertilized plots.  Yields between the plots in wheat were very similar.  However, there was a 15% greater yield of canola on the amended manure plot over the commercially fertilized plot.  The majority of this difference can be attributed to the reduced plant density on the commercially fertilized plots as discussed earlier.

Following harvest of the test plots, the individual test plots were soil sampled at random locations to determine residual nutrient levels in the soil for the alternate sources of fertilizer.  These laboratory results have been summarized in Table 6.

Table 6.  Soil Nutrient Levels Post Harvest 

On the wheat trials, the amended manure application resulted in an 8 lb/acre increase in Nitrate –N levels over the commercial fertilizer application of 80 lb/acre.  The difference between the theoretical and actual nitrogen utilization on this basis indicates that approximately 60% of the nitrogen was available.  It was anticipated that the nitrate levels for the check strip would have been significantly lower than the plots receiving supplemental nutrients.  Instead, levels were consistent with the commercially fertilized plot.  Unexpectedly, the phosphorus level on the amended manure plot remained consistent with the background phosphorus level measured earlier in the spring, while the commercially fertilized plot, which received a similar amount of supplemental phosphorus experienced a 48 lb/acre difference in residual nitrogen.  A similar anomaly is evident in equal residual phosphorus levels between the commercially fertilized plot and the check strip.  Potassium levels were highly erratic with variations almost ten times greater than the potassium added with the manure.  The check plot, which received no supplemental potassium, experienced a 30% increase in residual levels.  It is evident from these results that the soil nutrient levels determined from a representative sample of the entire field did not accurately reflect the true nutrient levels for each of the individual plot areas.

In the canola trials, the estimated nitrogen application rate with the amended manure was 91.6 lb/acre compared to 100 lb/acre of nitrogen applied with the commercial fertilizer.  Based on the 12 lb/acre increase in residual nitrogen over the commercially fertilized plot, the percentage of nitrogen available in the manure would have been approximately 61% assuming no variability within the field.  Phosphorus levels were also variable.  Similar phosphorus application rates for the amended manure and commercial fertilizer yielded a 24 lb/acre difference in residual levels.  As expected, the phosphorus levels on the check strip declined. However, the decline was significantly smaller than would be expected following a season of crop growth.  Residual potassium levels in the canola plots were highly variable as with the wheat plots.  In this situation, the initial field soil samples were not representative of the area of the field where the test plots were conducted although the background tests encompassed the test plot area.

Phase II – Test Plots at ProWest Nurseries, Hartney

Phase II was initiated early in September, 1999 at ProWest Nurseries in Hartney, Manitoba.  As in phase I, manure and soil samples were gathered and analyzed for nitrogen, phosphorus and potassium levels.  Similar to phase I, the manure storage was sampled at one foot increments before and after agitation.  Results of these tests have been summarized in Table 7 and Table 8.

Table 7.  Nutrient Levels of Swine Manure Prior to Agitation 

Table 8.  Nutrient Levels of Swine Manure after Agitation

Due to the results of the manure analysis, it was determined that two tonnes of 28-0-0 was required to achieve the desired nutrient levels for a balanced application based on phosphorus.  This was equivalent to supplementing 8.8 pounds of nitrogen per acre.  To facilitate the addition of this small amount of product, the 28-0-0 was added to the storage and agitated prior to pump-out.  Field application of the manure was accomplished using umbilical application techniques.

Results for the amended manure mixture prior to application are summarized in Table 9.  As anticipated, the average nitrogen content marginally increased by 1.17 lb/1000 gallons as a result of the liquid nitrogen added to the manure.   The phosphorus and potassium levels, however, fell from the levels originally measured when the storage was initially agitated.  As the phosphorus and potassium are not volatile, this decrease can not be explained by losses during agitation.  Dilution of the manure from the addition of the commercial fertilizer is not a feasible explanation as the volume added represented only 4/100^th’s of a percent of the total manure volume, whereas the percentage decrease in phosphorus and potassium was 7.5% and 6% respectively.

Table 9.  Nutrient Levels of Swine Manure after Application of Commercial Fertilizer 

Following the blending of the commercial fertilizer with the manure, it was required to stop agitation as a heavy rainfall made application impossible for several days.  When the spread field became accessible, agitation was again started and continued until it was felt that thorough mixing was achieved.  During application manure samples were taken from a discharge at the pump at two hour intervals in order to determine the nutrient consistency of the manure during the pump-out process.  Table 10 indicates the results of the nutrient analysis for each interval.

Table 10.  Manure Nutrient Analysis during Pump-out of Amended Manure 

As indicated, the nitrogen and potassium levels remained relatively consistent during the entire clean-out.  The phosphorus content ranged widely particularly during the last six hours of cleanout.  It is believed that this is due to the fact that the agitation needed to be turned off once the liquid level in the tank dropped to approximately 4’ from the bottom to prevent cavitation of the agitator propeller.  As a result of stopping agitation, it is highly probable that some of the suspended solids settled out resulting in a higher concentration of phosphorus near the bottom.

Initially, the test plots were seeded to Canamaize.  However, due to poor germination and seedling vigour it required re-seeding.  In order to avoid the risk of frost, “Smart” canola 46A73 was selected and seeded at a 6 lb/acre rate.  Some concern had been expressed whether the rainfall during the summer of 2000 had affected the trial.  However, rainfall in the area was not excessive lending itself to favourable growing conditions.

Following the seeding of the Canamaize, soil samples were collected on the respective plots in order to measure background nutrient levels and eliminate the variable of losses from the manure since the application last fall.  The plots consisted of a check plot to act as a control, the amended manure plot and a commercially fertilized plot.  The check plot received no fertilizer and constituted only residual nutrients from the previous crop year.  The commercially fertilized plot received 80 lb/acre nitrogen in the form of anhydrous ammonia, 25 lb/acre of phosphorus and 10 lb/acre of potassium at the time of seeding.  Table 11 summarizes the background soil nutrient levels in the top 24” of the soil profile as measured in the spring of 2000.  No additional fertilizer was added when the plots were re-seeded to canola.

Table 11.  Background Soil Nutrient Levels

No visual indication of differences in growth between all of the plots was evident.  Emergence, plant density, and colouration were consistent for all of the plots throughout the growing season.   Nearing harvest it became evident that the commercially fertilized area was reaching maturity slightly faster than the amended manure and check plot.  This difference in maturity was attributed to lower nutrient levels at the plot location.

A weigh wagon was utilized to monitor the yield of each plot in order to draw a yield comparison, Table 12.  As indicated by the yield measurements, the amended manure plot yielded 6.9% less than the check strip which had unusually high background nutrient levels, and 3.2% less than the commercially fertilized plot.

Table 12.  Yield Summary, lb/acre 

Following harvest, each test plot was soil sampled at locations near the original sampling locations to determine residual nutrient levels in the soil.  The laboratory results have been summarized in Table 13.

Table 13.  Soil Nutrient Levels Post Harvest 

With the exception of the nitrogen level on the commercially fertilized plot and the potash level of the check plot, the other nutrient levels all dropped from the original background levels measured in the spring.  Although the increase in nitrogen was not expected, it is evident that not all of the anhydrous applied in spring was utilized, resulting in an increase in residual levels.  The increase in potash can not be explained other than by statistical variation as no supplemental potash was added to the plot.

Value of Nutrients Contained in Swine Manure

Based on the measured nutrients for each of the trials, the value of the nutrients were calculated based on current commercial granular and liquid fertilizer prices, Table 14 and 15.  The nutrient value has been calculated based on two different application rates; the 3500 gal/acre reflecting the application rate in Trial #1 and the 6000 gal/acre reflecting the application rate in Trial #2.  An adjusted value has been indicated to reflect a potential 10% loss in nitrogen based on application by injection.  Appropriate reduction factors would need to be applied for application methods such as irrigation and broadcasting which incur additional losses.  Because manure test results are expressed in terms of elemental phosphorus and potassium and commercial fertilizer is sold on the basis of phosphate (P₂O₅) and potash (K₂O) it is necessary to convert these forms into equivalent values.

Table 14.  Trial 1 – Equivalent Nutrient Value of Swine Manure 

Table 15.  Trial 2 – Equivalent Nutrient Value of Swine Manure 

The nutrient values indicated represent the value of the nutrients contained within the manure as applied.  It should be noted that not all of the nutrients are available in the year of application as approximately half of the nutrients are organic in nature and must first be broken down into a usable form.  The value of nutrients available in the first year would therefore be represented by half of the value indicated.  The remaining nutrients would be available in subsequent years and are therefore included in the value of the manure nutrients.  The values indicated do not account for micro-nutrients in the manure and the organic nature of the product.  The value of micro-nutrients have been estimated at $7.50 per 1000 gallons from previous estimates but has not been included to offset the value of excess potash applied in each case.  The value of the organic benefits has not been assessed.

Transport and Application Costs for Swine Manure

Custom manure applicators in Manitoba were contacted in order to establish an average manure application cost across the province.  Those applicators which either applied manure using pipeline/draghose or tankers equipped with injectors were contacted as these are the most popular methods of application and represent the highest cost of application.  Table 16 represents the average application costs ($/imp. gal) of the various application methods based on varying application rates.  The 10,000 gal/acre application rate is not relevant to either of the trials conducted but does represent the cost of application at rates that many producers have used in the past and may currently be employing depending on the nitrogen content of their manure.

Table 16.  Average Custom Manure Application Cost 

Application costs were calculated for application rates typical of the two trials conducted and various travel distances, Table 17.  Based on these application costs and the value of the nutrients contained within the manure the feasible transport distance can be calculated.  For trial #1 and trial #2 the manure can be hauled by tanker a distance of approximately 6 to 7 miles before the cost of application exceeded the value of the nutrients based on granular fertilizer cost.  Transport distance increases to approximately 8 miles if the value of the nutrients is based on liquid fertilizer prices.  In both cases, these distances could be significantly increased by utilizing a nurse truck which is more efficient for transporting greater distances.

Table 17.  Cost of Manure Application Based on Site Specific Application Rate 

It was not possible to contact any custom applicators using pipeline technology to transport manure any further than three miles from the storage.  The cost of manure application within this distance is less than half of the nutrient value which we encountered in the trials.

Results and Discussion:

Based on test plots conducted over the last two years, there has not been conclusive evidence to demonstrate that comparable yields can be achieved from an amended manure application versus commercial fertilizer.  In trial #1, yields from the amended manure exceeded the commercially fertilized plots by 1.1% and 13.4% in AC Barrie and Hyola 401 respectively.  Weather related factors did contribute to the significant difference in Hyola yields.  In trial #2, the yield of Smart canola 46A73 fertilized by amended manure was 3.2% less than the plot commercially fertilized.  Similar research conducted by Curtis Cavers of Manitoba Agriculture’s Soils and Crops Branch using manure only in comparison to commercial fertilizer has experienced similar results in which favourable crop response to one of the two methods of fertilization is random in a particular year.

The amendment of commercial fertilizer into manure was shown to be a feasible option to balancing nutrients based on crop requirements.  Further development of blending and manure testing equipment is necessary to feasibly implement this technology on a commercial scale.  Currently manure can be applied at rates to match the phosphate requirements of the crop to be grown and nitrogen supplemented as required from a commercial source.  The development of this blending technology would eliminate the additional expense of an added field operation to apply the supplemental nutrients.  More importantly would be the development of equipment to rapidly determine manure nutrient levels in the field.  This would permit more accurate nutrient application rates avoiding unnecessary over application or nutrient deficiencies affecting productivity.

The research demonstrated that it is possible to apply manure at rates compatible with crop requirements without the potential for nutrient accumulations.  Nitrate, phosphate and potash levels decreased on the plot which received the amended manure in trial #2.  In trial #1, no nutrient accumulations were noted on the wheat plots.  However, nutrient levels generally increased on all of the canola plots.  This is attributed to the fact that background nutrient levels were determined on an average field basis rather than by individual plot which would have yielded a more accurate comparison.  Further research into the long term effect of repeated applications over several consecutive years is required to substantiate that nutrient accumulation will not occur.  Annual fluctuations are anticipated as crop uptake is affected by variable climatic conditions.  The implementation of annual soil testing is required to identify significant nutrient carryovers and permit the appropriate measures to be taken.

Based on the trials conducted, it was determined that the feasible transport distance using tankers equipped with injectors varied from six to eight miles from the storage.  Similarly, it was determined that the cost to spread manure using pipeline technology to a distance of three miles was less than half of the nutrient value in the manure. Table 18 demonstrates the difference between application costs and the value of nutrients contained within manure.  These values represent the true value of manure to grain producers as an alternate to commercial fertilizer.  These results are specific to the testing conducted and will vary depending on the nutrient content of the manure to be spread.

The research conducted concentrated on positive containment structures.  It was shown that a homogeneous mixture can be achieved with proper agitation provided the agitation can be maintained throughout the complete cleanout.  The nutrient content of manure contained within earthen storages is expected to be lower than those encountered in our tests.  For this reason, it is anticipated that the feasible transport distance of manure from earthen storages will be slightly less.

Table 18.  Net Nutrient Value ($/acre) 

Conclusions:

• With aggressive and continuous agitation, it is possible to achieve a relatively consistent manure nutrient content in a Slurrystore structure.  It is important to maintain agitation throughout emptying to maintain this homogeneity.

• By blending commercial fertilizer into swine manure it is possible to achieve a single pass application meeting crop requirements.  By utilizing the manure nutrients to meet the phosphorus requirement of the crop and supplementing the necessary nitrogen it is possible to efficiently utilize the available phosphorus and nitrogen in the manure.  The proportion of potassium contained in the manure which can be fully utilized will vary depending on background soil nutrient levels.

• Further research is required to substantiate that nutrient accumulation will not occur from repeated applications of swine manure.  Annual soil testing is required to monitor nutrient carry-over from the previous year in order to avoid accumulations.

• The value of the nutrients available in swine manure stored in Slurrystore structures without consideration of the organic benefits is substantial.  The research has demonstrated that swine manure is a feasible alternative to commercial fertilizer and will represent a cost saving to grain producers located near swine operations.

Future Directives

It has become evident from this research that in order to implement this technology on a commercial basis, it will be necessary to develop a method of nutrient analysis in the field.  Currently, a lapse of several days is required in order to receive soil and manure nutrient test results from the laboratory.  In reality, a custom applicator moves on site, agitates the manure storage and starts application within half a day.  The availability of a field devise which will quickly measure nutrient levels would alleviate the need for undesirable down time and permit more accurate nutrient management instead of relying on an average value.  Several companies such as PDK Projects Inc., Ag Waste Management Corp. and Ramboc are currently developing and testing such equipment.  We have been informed that Ag Waste Management Corp. has applied for a patent and is currently prototyping application equipment with in-line monitoring capabilities and blending capacity for a balanced nutrient product.

The research conducted concentrated on swine manure stored in Slurrystore structures in order to have a regular shaped storage which was easily agitated in hopes of obtaining a nutrient uniform slurry.  The applicability of this technology to earthen storage requires further investigation.  Due to the irregular shape and often, larger size, it has been shown in the past that consistent nutrient uniformity is not achievable.  The development of field testing equipment or in-line testing equipment will permit frequent testing to occur during pump-out resulting in more accurate nutrient application.

Previous publications have suggested that the nutrient content of manure contained within earthen storages is significantly less than positive containment facilities such as Slurrystore and concrete structures.  Although this is conceivable for nitrogen content, as the volitization of nitrogen increases as surface area increases, there is no explanation for phosphorus and potassium decreases.  Further research into the nutrient levels of manure from earthen storages is required to assess the feasible transport distance.

No information was available to evaluate the value of organic matter in animal manure.  The benefits of organic matter to crop yield needs to be assessed and quantified in a value per acre.  Similarly, the benefits of micro-nutrients contained within manure, which are generally not added as commercial fertilizer, should be further evaluated.  Both of these factors will enhance the value to grain producers.

Further product development of the introduction and blending of commercial fertilizer into the manure stream is also required.  Two relatively inexpensive methods were implemented in the research.  Neither method is conducive to commercial application as one method was significantly labour intensive, and the other eliminated the flexibility to vary nutrient levels on a continual basis.  The development of a reliable and accurate in-line monitoring system would be ideal.

Acknowledgements:

This project was funded by the Agri-Food Research and Development Initiative (ARDI) and the Manitoba Livestock Manure Management Initiative Inc.  The author expresses thanks to Managro Harvestore and Elite Swine Inc. who were co-operators with the project, Martin Farms (landowner/operator Phase I) and Ed Philips (landowner/operator Phase II).

ARDI Home - Contact ARDI