Press Releases and Project Papers

These early reports involve EMU 2009 Summer Bridge Students who did mini-research projects comparing the soil characteristics of two organic treatment plots.  A sampling of these student reports follow.

2009 Summer Bridge Student Blueberry Soil Reports

An Analysis of Soil Health for the Production of Organic Blueberries in Comparing the Fertilizing Methods of Pine Straw to Sheep Manure and Hay

July 27-30, 2009

Karla Martin

Abstract

Animal manures, crop residues, and composts are all organic fertilizing methods that provide various nutrients and help build soil organic matter.  However, each of these methods contains certain precautions to be heeded, depending on the crop planted and soil type.  In this experiment, soil health and suitability of certain plots located in the Shenandoah Valley of Virginia for raising blueberries was determined and the fertilizing effects of pine straw in comparison to those of sheep manure and hay were examined.  A series of LaMotte tests were conducted on soil samples to investigate the chemical properties of the soil for pH, nitrate nitrogen, phosphorus, potassium, ammonia nitrogen, calcium, and nitrite nitrogen.  In addition, infiltration assessments were completed as well as respiration tests to detect biological activity.  Based upon its lower soil pH of 5.4 and high organic matter content, the pine straw soil plots had more suitable conditions for optimal blueberry production.  Both the pine straw and sheep manure and hay soil plots need additional ammonia nitrogen to be applied in the form of fertilizer, and both contained high levels of calcium at 14,000ppm, which may be a concerning issue that causes magnesium deficiency.  Further research of the soil calcium should be performed since the high calcium levels did not supplement the higher soil acidity of the pine straw plot or complement the usual amount of calcium found in soils with sandy textures. 

Introduction

“Soil is a living entity: the crucible of life, a seething foundry in which matter and energy are in constant flux and life is continually created and destroyed” (Hillel, 1991).  Soil is incredibly complex as its contents are in a constant cycle of change.  Mineral matter, organic matter, air, and water are the four primary constituents of soil.  Soil organic matter comprises the “liveliness” of the soil and includes microscopic plant and animal materials in different stages of decomposition.  It is often referred to as the fiber that connects the biological, chemical and physical properties of soil and the factor that determines soil health and productivity.  Furthermore, soil organic matter supplies plant nutrients, such as nitrogen, phosphorous, and calcium; supports water infiltration; and helps crop growth by enhancing the soil’s capability to transmit air and hold water. (Cooperband, 2002)  When analyzing soil content, the organic matter contains the key to producing a sustainable crop. 

Organic farmers heavily rely on the soil organic matter to provide adequate soil nutrition for their crop production since synthetic fertilizers and pesticides are prohibited from use.  Soil organic matter can be built and managed through the application of animal manures, crop residues, and composts, but each of these organic fertilizing methods have differing precautionary guidelines for use depending on the soil type and crop planted.  In general, animal manures are sources for many nutrients and organic matter.  Raw manures that are applied to crops contain more available nutrients, but composted manures are more biologically stable and are void of weed seeds and pathogens.  Often times, the application of animal manures to increase nitrogen causes excessive phosphorus to be supplied because manures have similar amounts of nitrogen and phosphorus.  The excess phosphorus results in an imbalance in the ratio between nitrogen and phosphorus where crops need six times more nitrogen than phosphorus (Kuepper and Diver, 2004).  Crop residues are very biologically active and high in carbon.  Though they provide ample supplies of organic matter, crop residues may leave diseased materials in the soil that can affect crop production from year to year.  Composts are biologically stable sources that can improve the biological, chemical, and physical aspects of soil content, but use of composts may cause salt damage to occur in sandy soils with low organic matter.  Composts also need to be in a mature state; unfinished composts can hold toxic levels of aluminum. (Kuepper and Diver, 2004)  All these organic fertilizing methods improve soil health if certain guidelines for use are followed, depending on the soil type.

The purpose of this experiment is to investigate the soil health of certain organic soil plots located at Knoll Acres in the Shenandoah Valley of Virginia and to determine the soil suitability for optimal organic blueberry production on those soil plots.  The effects of pine straw fertilizer will be compared to that of sheep manure and hay in determining soil quality for the growth of organic blueberries.

Materials and Methods

The following soil tests were completed during this experiment: soil respiration to detect microbial activity, infiltration which serves as a physical indicator, soil sampling, and several LaMotte tests for pH, nitrate nitrogen, phosphorous, potassium, ammonia nitrogen, calcium, and nitrite nitrogen.  To begin the soil respiration test, a random soil area that was mostly clear of surface residue and located in either of the designated rows I and J was chosen for testing.  A 6-inch diameter ring was driven halfway into the chosen soil plot using a hand sledge and block of wood.  The ring was covered with the lid and left for 30 minutes.  During the end of 30 minute waiting period, the soil temperature was recorded and the Draeger tube apparatus was assembled.  After 30 minutes, the Draeger tube apparatus needle was placed into one of the outer stoppers on the lid and a second needle was inserted into the other outer stopper to allow airflow.  Then, a head space sample was taken by pulling the syringe handle back to the 100cc mark. The estimated percent of carbon dioxide was then recorded by reading the highest point that the purple color reached on the “n=1” column. Then, all respiration materials were removed except the ring, which was used for the infiltration.  Beginning the infiltration, a layer of plastic wrap was situated over the ring and 444mL or 1-inch of water was poured onto the plastic wrap.  Then, the plastic wrap was gently pulled out from underneath the water, and the amount of time it took (in minutes) for the water to infiltrate the soil was recorded.  This infiltration procedure was then repeated a second time over the same soil space.  Two respiration tests and two full infiltration tests were completed—one in Pine Straw Row I and another in Pine Straw Row J.  Once both tests were finished, the soil respiration of lbs CO₂-C/acre/day was calculated with the equation: 1 x ((A + 273)/273) x (B – 0.035) x 22.91 x 5.08 where A is equal to the soil temperature in Celsius and B is equal to the percent of CO₂ from the Draeger tube on the “n=1” column.    

For the soil samples, ten shovels of soil from various, random places in both rows I and J were collected in a large container and evenly distributed among four smaller containers with lids.  In addition, two plastic baggies containing 100mL of soil from each row of Pine Straw was also collected.

A series of tests from the LaMotte Model 5^th Series Combination Soil Outfit Instruction Manual were then conducted on the four sealed containers of soil.  First, the LaMotte extraction procedure was completed to produce a soil extract, which was used in the rest of the conducted LaMotte tests for pH, nitrate nitrogen, phosphorous, potassium, ammonia nitrogen, calcium, and nitrite nitrogen (LaMotte, 2001).

Results

There are a total of 14 rows of soil for organic blueberry production at Knoll Acres as seen in the diagram below.  Rows E, F, G, and H were fertilized with sheep manure and hay, and rows I and J were fertilized with pine straw. The colored rows were chosen for the soil sampling; thus, the results describe the contents of these rows.

                                  

The Organic Blueberry Rows of Knoll Acres

Table1.  LaMotte Test Results (including the average and standard deviation) for pH, nitrate nitrogen, phosphorus, potassium, calcium, and nitrite nitrogen for the pine straw and sheep manure and hay samples.

	pH	Nitrate Nitrogen	Phosphorus	Potassium	Ammonia Nitrogen	Calcium	Nitrite Nitrogen
	5.4	150	150	390	5 (very low)	14,000+	< 1
	5.4	150	150	410	5 (very low)	14,000+	< 1
	5.4	150	200	410	5 (very low)	14,000+	< 1
	5.4	150	200	410	5 (very low)	14,000+	< 1
Average	5.4	150	175	405	5	14,000+	< 1
Stand Dev	0	0	28.87	10	0	0	0

	pH	Nitrate Nitrogen	Phosphorus	Potassium	Ammonia Nitrogen	Calcium	Nitrite Nitrogen
	6.6	40	200	350	5 (very low)	14,000+	1
	6.6	40	200	375	5 (very low)	14,000+	1
	6.6	50	200	250	5 (very low)	14,000+	1
	6.6	40	200	300	5 (very low)	14,000+	1
Average	6.6	42.5	200	318.75	5	14,000+	1
Stand Dev	0	5	0	55.43	0	0	0

When compared to the general soil respiration class ratings, pine straw rows I and J fall under the category of “ideal soil activity,” containing “adequate organic matter and active populations of microorganisms;” and sheep manure and hay rows E and G have “medium soil activity” where the “soil is approaching or declining from an ideal state of biological activity” (Soil Quality Test Kit, 1999).  The standard respiration readings can be seen in Table 2.

Concerning infiltration, all soil samples for both pine straw and sheep manure and hay had rates far beyond 20 inches per hour (Table 2).  Thus, all soil samples can be classified as having extremely rapid infiltration rates (Soil Quality Test Kit, 1999).

Table 2  Standard Respiration and Infiltration Rates (including the Averages and Standard Deviation) for Pine Straw Rows I and J and Sheep Manure & Hay Rows E and G. 

	Standard Respiration Rate (CO2-C lb/acre/day)	Infiltration Rate (in/hr)
Pine Straw Row I	47.36	66.64
Pine Straw Row J	40.02	59.41
Average	43.69	63.03
Standard Deviation	5.19	5.11
Sheep Manure & Hay Row E	31.14	73.89
Sheep Manure & Hay Row G	31.35	109.29
Average	31.25	91.59
Standard Deviation	0.15	25.03

The pine straw soil samples had a pH of 5.4 while the sheep manure and hay soil samples had a pH of 6.6 (Figure 1).  Both soil types had high levels of calcium at 14,000ppm (Figure 2).

Figure 1  pH values for the pine straw and sheep manure and hay soil samples.

Figure 2  Calcium values in parts per million for the pine
manure and hay soil samples

Both phosphorus levels for pine straw (175 lbs/acre) and sheep manure and hay (200 lbs/acre) are adequate supplies and do not require additional amounts in the form of fertilizer (Figure 3).  Both soil samples for pine straw and sheep manure and hay appear to have ample amounts of potassium and would not require additional amounts in the form of fertilizer (Figure 3).

As seen in figure 3, the pine straw soil samples contained about 71.7% more nitrate nitrogen than the sheep manure and hay soil samples.  Neither the pine straw nor sheep manure and hay soil samples require additional amounts of nitrate nitrogen in the form of fertilizer.  Both soil samples for pine straw and sheep manure and hay contained “very low” amounts of ammonia nitrogen and should have additional amounts applied.  Both soil samples for pine straw and sheep manure and hay had levels of nitrite nitrogen at or less than 1ppm.

Figure 3  Pounds per acre available phosphorus, potassium, and nitrate nitrogen in the pine straw and sheep manure and hay soil samples

Discussion

Based upon soil pH, the pine straw soil plots are more suitable for raising blueberries.  The sheep manure and hay soil plot pH should be lowered to the 4.8-5.5 pH range through the application of sulfur.  Since the soil had such a rapid infiltration rate, it can be classified as having a sandy texture.  Soils with sandy textures usually require 435-650 pounds per acre of sulfur to lower pH. (Soil Quality Test Kit, 1999)  In addition, the pine straw soil plots tended to have more adequate organic matter and biological activity as was seen through the respiration tests.  However, both soil plots are lacking in ammonia nitrogen.  Adding fertilizer in the form of feather meal, which contains around 13% nitrogen can help increase nitrogen levels without adding extra phosphorous or potassium nutrients, for blueberries usually contain sufficient amounts of potassium that are supplied through decaying mulches and prefer low levels of phosphorous (Kuepper and Diver, 2004). Neither soil scientists nor the Natural Resources Conservation Service has declared a maximum soil phosphorus level due to a lack of information assessing its negative effects on the environment.  However, the Mehlich III extraction testing method has suggested the general phosphorus limit to be 300 pounds per acre, a value that is said to be about three times more phosphorus than is actually needed (Daniels et al.).  Both phosphorus levels for pine straw (175 lbs/acre) and sheep manure and hay (200 lbs/acre) seem to have ample amounts of phosphorous at present, and both soil plots contain adequate supplies of potassium.  The high levels of calcium for both soil plots may be of concern.  If calcium levels are too high, a magnesium deficiency may result (Krewer and Nesmith, 2001).  The high calcium value of 14,000ppm for pine straw did not supplement the lower soil pH reading of 5.4 in which high calcium levels neutralize soil acidity.  This same high level of calcium at 14,000ppm somewhat complemented the slightly acidic pH of 6.6 for sheep manure and hay though an even higher, more alkaline pH may be expected (Figures 1 and 2).  Since the calcium levels did not necessarily complement the lower pH readings or the LaMotte soil tests where sandy soils typically contain around 500ppm calcium, experimental error in the testing procedure may have flawed the data; further research of the soil calcium should be conducted (Figures 1 and 2).  Concerning the extremely rapid infiltration rates, perhaps a drip irrigation system should be installed to increase the moisture content of the dry soil.  

References

Cooperband, L. 2002. Building Soil Organic Matter with Organic Amendments: A Resource for Urban and Rural Gardeners, Small Farmers, Turfgrass Managers and Large-scale Producers. Center for Integrated Agricultural Systems: 1-13.

Daniels M, Daniel T, Vandevender K. Soil Phosphorus Levels: Concerns and Recommendations. University of Arkansas Cooperative Extensive Service [Internet]. Available from: http://www.uaex.edu/Other_Areas/publications/pdf/FSA-1029.pdf

Krewer G, NeSmith S. 2001. Blueberry Fertilization in Soil. University of Georgia Ext. Fruit Publication 01-1 [Internet]: 1-12. Available from: http://www.smallfruits.org/Blueberries/ production/blueberryfert.pdf

Kuepper G, Diver S. 2004. Blueberries: Organic Production. ATTRA National Sustainable Agriculture Information Service IP021 Slot 30(Version 042505):1-26.

2001. LaMotte Model 5^th Series Combination Soil Outfit Instruction Manual. USA: LaMotte Company. 26p.

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Comparing the Quality of Sheep Manure/Hay Soil vs Horse Manure/Sawdust Soil and its Suitability for Growing Organic Blueberries at Knoll Acres

July 28-August 12, 2009

Phillip Martin

Abstract

Soil chemistry is very important to the health of the soil itself as well as the plants that grow in it.  The microscopic plants and animals that make up the soil help to maintain humus formation and are responsible for the organic waste recycling of our planet.  Blueberry bushes need the help of all of these microorganisms to survive and thrive and they do especially well when planted in soil mixed with organic fertilizer.  In this experiment, the suitability of sheep manure/hay soil for growing organic blueberries as well as a comparison between the health of sheep manure/hay and horse manure/sawdust was tested.  Soil respiration and infiltration tests were taken at Knoll Acres as well as two top soil samples and four soil samples from 10 inches underground.  LaMotte laboratory tests were then used to test for pH levels, humus, and other minerals within the soil samples.  The results showed that the sheep manure/hay soil needed to decrease its pH levels in order to become better suited for organic blueberry production, so therefore it was not as healthy as it should be.  This could be because the sheep manure has not had enough time yet to lower the pH of the soil.  No significant difference between the sheep manure/hay soil and the horse manure/sawdust soil was found when it came to soil health. 

Introduction

Everyone knows that soil is an important part of plant growth, but what makes it so special and how does it function?  Surprisingly enough, soil consists of billions of microscopic plants and animals that form the basis of the soil food web (Gershuny and Smillie, 1999).  Many of these organisms aid mainly in humus formation which creates a healthy soil.  The more organic matter that soil has, the better off plants will be in the future.  In general, these microbial organisms do most of the world’s organic waste recycling, so they are an indispensable part to soil science and inevitably its health. 

Three major groups of organisms play a role in the soils ecosystem and they include the producers, consumers, and decomposers.  The producers, most notably green plants and blue-green algae, are mainly your organisms that create their own food by using photosynthesis to capture the sun’s energy to create carbohydrates and proteins.  However, there are some specialized bacteria that can take carbon dioxide and mineral elements from the soil to create their own food.  The group with the most abundance of organisms would have to be the consumers.  These creatures mainly feed off of green plants, except for the secondary and tertiary consumers who will eat other consumers for nourishment.  Finally, there are the decomposers who are probably the most critical organisms to inhabit the soil.  All decomposers are bacteria and fungi and their job is to bring the basic chemical nutrients in the soil full circle.  An astounding 60 to 80 percent of the total soil metabolism is accounted for by microbial decomposers (Gershuny and Smillie, 1999). 

 Organic matter is the basis for decomposers to survive with an ideal balanced ratio of carbon to nitrogen of 25-30 parts to 1 (Meyer, 2002).  Carbon is the most important soil element since it allows for all soil biological activity and when balanced with mineral nutrients it provides a favorable pH.  Soil aeration is also important since air is a crucial part of soil health.  Plant roots cannot take the full advantage of the soils minerals without an ample supply of air.  Finally, water is a must for plants to grow successfully.  Ideal biological environments consist of each soil particle having a thin film of moisture clinging to it combined with lots of air circulation (Gershuny and Smillie, 1999). 

Bacteria are the most numerous organisms in the top 6 inches of soil and vary greatly in shape and in function.  An ideal environment for these organisms would be at a temperature of 21°-38°C and a pH close to neutral along with adequate moisture, food, calcium, and a balance of micronutrients.  These creatures may be small, but they are a force to be reckoned with since they basically have a monopoly on the three basic soil processes of nitrification, sulfur oxidation, and nitrogen fixation (Gershuny and Smillie, 1999).  Bacteria are able to take nitrogen in its different forms and make it available for other organisms to use, especially plants.  Many times these bacteria will have a symbiotic relationship with plant roots.

Molds are part of the fungi family and are wildly important for humus formation.  Mycorrhizae is one group of fungi that is extremely important since they have a symbiotic relationship with plant roots and are able to turn insoluble nutrients in biological forms, mainly phosphorus, and in return they receive carbohydrates from the plants (Gershuny and Smillie, 1999).  Actinomycetes are also an essential fungi group that helps with organic matter decomposition and humus formation.  Plenty of air is needed for these fungi along with a pH between 6.0 and 7.5.  Manure has high numbers of actinomycetes which makes it essential for making high-quality compost according to many people. 

Organic blueberries are a tasty treat but to grow them one needs the right kind of soil and the knowledge of how to grow them.  These blue fruits are members of the genus Vaccinium and belong to the Rhododendron family.  Highbush blueberries (Vaccinium corymbosum) are the most commonly cultivated bushes and are grown from the Mid-Atlantic to California, Oregon, and Washington, and from the Upper Midwest to the Mid-South (Kuepper and Diver, 2004).  Pest control is not much of a problem since they have fewer problems compared to most fruits.  This makes for an economic advantage when switching blueberries to an organic cultivation method.  Typically production begins in the third season for highbush blueberries and their yields increase for the next four years.  Three tons per acre can be harvested at full capacity and the plants will remain productive for at least 15-20 years.

Soil implications are very important to consider when deciding where to plant blueberries.  A low pH of 4.8 to 5.5 is the optimal soil range for blueberry growth.  If soil pH is higher then iron chlorosis may result, and if the pH is significantly lower then manganese toxicity begins to occur (Kuepper and Diver, 2004).  Low nitrogen requirements are necessary for blueberries but they thrive on organic fertilizer.  They also prefer soil and fertilizer nitrogen in the ammonium form which they absorb and use much more efficiently than nitrate nitrogen (Kuepper and Diver, 2004).   

The purpose of this experiment is to determine how suitable the sheep manure/hay plot at Knoll Acres is for growing organic blueberries.  Sheep manure/hay and horse manure/sawdust plots will also be compared to see if health wise the sheep manure/hay plots are as healthy, more healthy, or less healthy than the horse manure/sawdust plots.

Materials and Methods

A van was taken to Knoll’s organic blueberry plot in order for tests and samples to be taken of the soil containing the sheep manure/hay.  There were eleven plots at Knoll’s acres including four containing horse manure and sawdust, four containing sheep manure/hay, two containing pine and straw, and one containing Wenger’s professional mulch.  Since the sheep manure/hay plots were of more importance a USDA (United States Department of Agriculture) soil quality test kit guide was used to perform both a soil respiration test as well as an infiltration test.  The plots being tested were four rows of sheep manure/hay and they were tested against the four rows of horse manure/sawdust that were adjacent to the western most sheep manure/hay row. 

For the soil respiration test, a 6-inch diameter ring was driven into the soil.  The ring was then covered with a lid with rubber stoppers and was let sit for exactly 30 minutes.  During the 30-minute wait, a thermometer was inserted into the soil adjacent to the ring with the lid.  The Draeger tube apparatus was assembled just before the end of the 30-minute wait.  At exactly 30 minutes, a second needle was stuck  into one of the stoppers while inserting the Draeger tube apparatus needle into the other stopper.  The syringe handle was drawn back to the 50 cc reading and then repeated for a second reading.  The “n=1” column was read and  recorded as well as  the temperature in Celsius at the time of sampling.  In order to determine the lbs of CO2 that are produced per acre per day, the following equation was used:

Soil Respiration = PF x ((A+273)/273) x (B – 0.035) x 22.91 H where H is 5.08cm

The ring in the soil was left for the infiltration measurement.

For the infiltration test, fingers were used to gently firm the soil surface around the inside edges of the 6-inch diameter ring to prevent unnecessary seepage.  Plastic wrap was then used to completely cover the surface inside the ring to prevent disturbance to the soil surface when the water was added.  A 500mL graduated cylinder was grabbed and filled with distilled water to the 444mL mark.  The 444mL of distilled water was poured into the ring lined with plastic wrap.  Your partner stood  ready with a stop watch before the plastic wrap was removed.  Having removed the plastic wrap gently, your partner started the stopwatch.  The watch was stopped once the soil surface glistened, and the amount of time was recorded in minutes.  A repeat of the infiltration test was conducted to determine the true field capacity of the soil.  The ring was removed and moved to row G, and both the soil respiration test as well as the infiltration test were repeated as mentioned above.

During the 30-minutes one waited in between testing for soil respiration, top soil samples were taken.  A cup marked with mL was used to scrape the first two centimeters of the soil to fill a cup up to the 100mL mark.  Next, a plastic bag was label with the row and sheep manure/hay and filled with the top soil sample.  This step was repeated in order to fill a second plastic bag with 100mL of the top two centimeters of soil.  The last step was to take four plastic Tupperware containers and fill them each ¾ full with soil from about 10 inches underground from the sheep manure/hay plot. These samples were used to test for humus, pH levels, as well as trace minerals in the soil.

Back in the lab, the four Tupperware containers containing the soil were taken and labeled 1-4 respectively.  These four soil samples were used to test for pH, nitrate nitrogen, phosphorus, potassium, ammonia nitrogen, calcium, humus, and nitrite nitrogen.  The LaMotte series of extractions was used to assay the soil samples for the nutrients mentioned above.  The results that were achieved from testing the sheep manure/hay were then compared to the results from the horse manure/sawdust.

Results

The Knoll Acres Organic and Traditional Blueberry Plot is situated on a hill with a 10.1 degree downward slope from north to south with the blueberry plots being laid out lengthwise in a north to south fashion.  The four plots that are situated farthest east are the horse manure/sawdust plots, the next four are the sheep manure/hay plots, followed by two plots of pine and straw, and on the far western side is one plot of professional mulch from the Wengers.  Each sheep manure/hay plot has a width of 0.97 meters with the lengths of each plot being as follows; row E is 22 meters in length, row F is 20.9 meters in length, row G is 20.85 meters in length, and row H is 19.9 meters in length.  There is also a distance of 1.65 meters between each of the rows, along with a slight negative slope running from east to west. 

The pH level of the sheep manure/hay soil, which is 6.6, is above the optimal level of blueberry growth by .8.  Significant differences between the pH of the sheep manure/hay and the horse manure/hay are relevant because their mean number were 6.6 and 6.875 respectively (Table 1).  A 2-Sample T Test was done to compare the pH of the two soils by setting the null hypothesis and the alternate hypothesis equal to one another, and since the p-value was 0.04775, the null hypothesis (with an alpha value of 0.05) could be rejected.  Therefore it was concluded that the pH of the two soils was significantly different (Figure 1). 

 

 

 

 

 

 

 

 

 

Figure 1. Comparing pH levels of Sheep Manure/Hay vs. Horse Manure/Sawdust.

Figure 2. Comparing nitrate nitrogen levels of Sheep Manure/Hay vs Horse Manure/Sawdust.

A 2-Sample T Test was also administered to compare potassium levels in sheep manure/hay and horse manure/sawdust.  There was a significant difference since the p-value was 0.02995.  Therefore the null hypothesis was rejected at an alpha value of 0.05 concluding that there is significantly more potassium in the horse manure/sawdust soil than in the sheep manure/hay soil with their means being 318.75lb/acre and 500lb/acre respectively (Table 1).  The horse manure/sawdust soil also had significantly more nitrate nitrogen in it than the sheep manure/hay soil according to the 2-Sample T Test with their means being 50ppm and 153.75ppm respectively (Table 1).  Since the p-value was 0.00021, the null hypothesis was rejected at an alpha value of 0.05 concluding that the horse manure/sawdust soil had significantly more nitrate nitrogen than the sheep manure/hay soil (Figure 2).  The horse manure/sawdust soil is therefore better suited for organic blueberry production due to the higher levels of potassium, but since blueberries prefer nitrogen in its ammonium form versus nitrate nitrogen, the significant difference in levels of nitrate nitrogen is irrelevant. 

Humus levels between sheep manure/hay and horse manure/sawdust, with a mean of 2.25 and 3.625 respectively, were also shown to have an insignificant difference.  Since the p-value was 0.0533, the null hypothesis was not rejected at an alpha value of 0.05 (because 0.0533 is not less than 0.05) concluding that the humus levels in sheep manure/hay and horse manure/sawdust were not significantly different (Figure 3).  Both the sheep manure/hay soil and the horse manure/sawdust soils had very high levels of calcium which were 2800ppm and 2625ppm respectively as well as equal levels of nitrite nitrogen levels at 1ppm and phosphorus levels at 200lb/acre (Table 1).   The levels of phosphorus are relatively normal, but the high calcium levels are undesirable for blueberry growth. 

The Horse Manure/Sawdust soil had an usually high soil respiration level with a mean of 122.165 CO2 – C/acre/day while the sheep manure also had an ideal level of respiration at 60.997 CO2 – C/acre/day (Table 1 and Figure 3).  There may have been some error when measuring soil respiration for the horse manure because the soil temperature is about 10 degrees cooler than soil temperature for the sheep manure/hay.  Instead of measuring the temperature at 1 inch, the thermometer could have been put all the way into the soil.

Finally, no significant differences between the soil quality of the sheep manure/hay versus the horse manure/sawdust was discovered besides the increased amount of potassium in the horse manure/sawdust soil which does improve soil quality.  There is still a lot of work that needs to be done to the sheep manure/hay soil in order for it to become better suited for blueberry growth, especially concerning the pH levels.

 

SOIL TESTS	Number of Samples	Sheep Manure/Hay	Horse Manure/ Sawdust
pH	4	6.6 ± 0	6.875 ± 0.2217
Humus	4	2.25 ± 0.2887	3.625 ± 1.1087
Nitrate Nitrogen (ppm)	4	50 ± 20	143.75 ± 12.5
Potassium (lb/acre)	4	318.75 ± 55.4339	500 ± 115.47
Phosphorus (lb/acre)	4	200 ± 0	200 ± 0
Calcium (ppm)	4	2800 ± 0	2625 ± 880.814
Nitrite Nitrogen (ppm)	4	1 ± 0	1 ± 0
Soil Respiration (CO2-C/acre/day)	2	60.997 ± 0	122.165 ± 0.7849
Soil Infiltration (in/hr)	2	91.59 ± 35.03	199.025 ± 217.669

Table 1  Mean soil test readings of sheep manure/hay and horse manure/sawdust plus/minus their standard deviation

 

Figure 3  Levels of soil respiration are compared between sheep manure/hay and horse manure/sawdust

Discussion

According to the results, the horse manure/sawdust soil had a much higher respiration rate than the sheep manure/hay soil, which could have been due to human error while doing the experiment.   The sheep manure/hay soil had a respiration rate of 60.997 lbs CO2-C/acre/day which gives it an ‘ideal soil activity rating’, while the horse manure/sawdust had a respiration rate of 122.165 lbs CO2-C/acre/day which gave it an ‘unusually high soil activity rating’.  The ‘unusually high soil activity rating’ starts at 64 lbs CO2-C/acre/day, so the horse manure/sawdust reading seems to be an exorbitant number.  The error could have occurred when the soil temperature reading was taken, because the sheep manure/hay soil temperature had an average of 34.65°, while the horse manure/sawdust soil temperature had an average of 23.95°, which is a difference of 10.7°.  The procedure mentioned that the thermometer should be placed one inch below the surface, so the horse manure/sawdust group may have placed their thermometer deeper into the soil than necessary. 

No significant difference between the sheep manure/hay and the horse manure/sawdust soil was found, therefore the sheep manure/hay plot is as healthy as the horse manure/sawdust plot.  Nitrate nitrogen and potassium were the only two parameters where the horse manure/sawdust soil had a significantly higher reading than the sheep manure/hay soil.  However, only the potassium is of much interest since it and nitrogen are of greatest concern when using supplemental fertilization (Kuepper and Diver, 2004).  Although nitrate nitrogen is a form of nitrogen, blueberries tend to go for nitrogen in the ammonium form which tends to occur when the soil’s pH is acidic.  Since both of the soils tend towards being neutral, there should be a higher concentration of nitrate nitrogen versus ammonia nitrogen.  If this experiment were to be continued, a LaMotte ammonia nitrogen test should be conducted in order to better compare the quality of both soils.  Many of the other parameters that were used to compare the sheep manure/hay and horse manure/sawdust plots were very similar and helped to support the hypothesis that, health wise, there was no significant difference between the sheep manure/hay and the horse manure/sawdust soils.  These parameters included the humus, pH, phosphorus, calcium, and nitrite nitrogen. 

Some parts of this soil make the soil suitable for growing organic blueberries.  The respiration rate of 60.997 lbs CO2-C/acre/day for sheep manure/hay gives it an ‘ideal soil activity rating’ which means it has adequate organic matter and active populations of microorganisms.  This ties into the medium reading the soil tested for humus, which means that there is an ample supply of organic matter imperative for organisms and plants to thrive. 

Sheep manure/hay soil is not the most suitable soil for growing organic blueberries.  The pH of the soil is only 6.6 which is not the ideal pH of 4.8-5.5 for blueberries to grow properly.  The more neutral nature of the soil also affects what kind of nitrogen is in the soil, namely nitrate nitrogen versus ammonia nitrogen.  Blueberries absorb ammonia nitrogen much better which would make sense since they like acidic soils.  Unfortunately, in this soil there is most likely very little ammonia nitrogen due to the soils neutrality, although there seems to be a rather low level of nitrate nitrogen in the soil as well.  Since the manure and hay combination has only been on the plots for a short amount of time, there is still room for the soil to change its chemical characteristics which would mainly include lowering its pH and ultimately creating more ammonia nitrogen for the blueberries to thrive on. 

References

Gershuny G, Smillie J.  1999. The Soil of Soil. White River Junction: Chelsea Green Publishing Company.

Kuepper G., Diver S. 2004. Blueberries: Organic Production. 

Meyer Dr. J. 2002. Building Soil Organic Matter with Organic Amendments. Madison: Center for Integrated Agricultural Systems. 13 p.

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The Effects of Nitrogen and pH on Mulches in Organic Blueberry Soils

Aly Zimmerman

 7/27/2009

Abstract

In this experiment, determining the health of the organic soil plots at Knoll Acers was the main objective. It was then be necessary to deduce the requirements for the plots to become optimal to blueberry plant growth. Soil respiration, certain element levels and pH were also important factors in determining soil health in relation to blueberry plants. CO₂ emission levels were recorded using Draeger tubes and further data on pH, nitrate nitrogen, phosphorus, potassium, ammonium nitrogen, calcium, humus and nitrate nitrogen were collected in the lab. It was found that the pH of the professional mulch plots was relatively high, there should be more nitrate nitrogen and the phosphorus levels were rather low. More nitrate nitrogen would allow the professional mulch to decompose more rapidly, thus buffering the pH of the soil.

Introduction

For agriculture to be considered organic, the farmer must follow USDA Organic Program rules and be certified by an accredited agency.  Examples of these rules are as follows: farming in a crop rotation to protect the plants against insects and maintain healthy soil and adding soil amendments such as lime, manure and compost. (ISU, 2003)

Another important role of soil in organic farming is maintaining soil organic matter. Soil organic matter begins with the fixation of CO₂ and produces an aggregate sustainability, food source and habitat to beneficial organisms (USDA, 1996). When organic matter is decomposed by aerobic microbes, CO₂ is released. Soil respiration is a good indicator as to the amount of organic matter in the soil. These microbes perform with the most efficiency at 35 to 40°C with as much as a 10^o variation being acceptable.  (USDA, 2009)

Blueberries are especially good to grow organically.  They adapt well and have fewer problems with pests, which is helpful when organic farmers can not use most pesticides. Because blueberries are in the Rhododendron family, they require an acidic soil. Soil pH also effects the nitrogen management in blueberry plants. Being as they also require little nitrogen, an acidic soil with a pH of 4.8 to about 5.5 is the optimal condition for blueberries. Blueberries seem to grow wonderfully with organic fertilizers and prefer the ammonium form of soil and fertilizer nitrogen. In their article, Blueberries: Organic Production, Kuepper and Driver state that the blueberry plant absorbs and utilizes the ammonium form much more efficiently than nitrate nitrogen (Kuepper and Diver, 2004). In Hayden’s Fertilizing Blueberries, however, he claims that nitrogen is the element to which blueberries are most responsive. In many situations, Hayden writes, it is the only element needed (Hayden, 2004).

When mulches are applied to a blueberry plot, however, it is recommended that the farmer apply extra nitrogen to the plot to encourage the decomposition of the mulches. Fresh materials are likely to be harmful to blueberry plants and well-decomposed mulches are the most suitable. (Hayden, 2001)

Organic blueberry farmers should also have care in the application of soil sulfur. Peat moss would be a better choice, both because it is a soil acidifier and because too much sulfur can devastate the soil. Pine bark is another suggestion in place of peat. It is less expensive and has many of the same effects. Adding mulches is also recommended because it acts to buffer the soil pH. This offers some form of protection against irrigation water, which tends to introduce calcium and magnesium into the soil. Both of these elements can raise the pH of soil (Kuepper and Diver, 2004). Where the pH is substantially higher than 5.1, correction is difficult and expensive, and commercial production of blueberries is discouraged (Hayden, 2001).

Water standing over blueberry plants for any length of time can be injurious to the plant (Hayden, 2001). Having the plant on an incline would greatly benefit it, being as the rain water would flow downhill and not stand over the plants. Again, the organic farmer must be careful of the soil pH because the rain water flowing downhill can also drag calcium and magnesium into the plot (Kuepper and Diver, 2004).

In this experiment, determining the health of the organic soil plots at Knoll Acers is the main objective. It will then be necessary to deduce the requirements for the plots to become optimal to blueberry plant growth. The nitrogen content as well as the pH of the soil will be the focus of this experiment. All data will be taken in knowledge that the plot used professional mulch as an assistant to the soil health.

Materials and Method

As the first part of the experiment, the soil respiration apparatus was used to determine the CO₂ emissions from the professional mulch plot. After other data from the plot was recorded, the soil samples were taken to a lab to have LaMotte tests preformed upon them. The LaMotte tests gave valuable information on the chemical composition of the soil and the different elements in the soil, as well as other data.

The metal diameter ring used in the soil respiration apparatus was driven into the soil about three inches. The plastic lid was placed on the ring and the soil temperature was measured in degrees centigrade. Thirty minutes passed. At the end of the thirty minutes, as quickly as possible the two ends of the Draeger tube were broken and the tube apparatuses—one tube with a syringe and another tube with a needle—were attached to the different ends. The needle connected to the tube that was also attached to the Draeger tube was pushed through the farthest right rubber stopper on the lid. A second needle was inserted into the farthest left rubber stopper, as well.

Figure 1: The soil respiration apparatus shown above was used in determining the percentage of CO₂ being emitted from the soil.

Air was pulled through the Draeger tube by using the syringe.  Taking the results from the Draeger tube, the CO₂ level was recorded. A second temperature test was taken on the soil and the data was recorded.

Then, a double layer  of plastic wrap was laid inside of the metal ring. Water was poured into the ring, but the plastic wrap leaked. On the third time, there was no mistake and the plastic wrap was pulled from the ring and it was recorded how long it took the water to seep into the ground.

With the saturated soil, the first part of the experiment was repeated. The soil respiration was tested with the wet ground.

The length and width of the plot were also recorded in meters by using a measuring tape. Also recorded was the angle of depression and the difference in height from the bottom of the plot to the top of the plot. The angle of depression was found by filling a glass with water and measuring the angle of the water as compared to the ground with a protractor.  An overview was taken and a description of the plot was recorded.

Four samples of soil were taken from the four plots. Also, microorganisms were collected from the soil by grazing the top most layer of soil in several areas of a plot.  Four containers were filled with soil taken from four of the professional mulch plots by digging beneath the surface to collect the soil. Then, in order to collect microorganisms from the soil, a pinch of surface dirt was taken in 25 different, random places from the first professional mulch plot.

These soil samples were taken to a lab where LaMotte tests were preformed upon them. The levels of pH, nitrate nitrogen, phosphorus, ammonium nitrogen, humus and nitrate nitrogen were tested to evaluate the chemical health of the soil for organic blueberry plants.

Results

Observing the plot, it was recorded that four days earlier, it had rained profusely. The top soil was dry, clumpy and a light, dusty tan color. About an average of 2 centimeters of the top soil was dry, but below that the soil was very moist. There seemed to be a black, burnt substance on the plot. It was speculated to be ash from a wood fire. The rest of the soil’s color varied from a deep brown-maroon, a deep chocolate brown, a medium brown, a light tan brown to a dusty-almost-white tan. The professional mulch was extremely fine and retained moisture easily. The edges of the plot dipped down slightly and the center rose up. Also, the plot was filled with varying rocks. Very few were larger than an adult’s fist, but almost every inch of ground had a few rocks in it.

Figure 2: The length of the plot at Knoll Acers was about 9.65 meters and the angle of depression from the top of the plot to the bottom of the plot was 11^o. The slope was found to be -0.19648. This data was helpful in determining if rain water was pulling calcium and magnesium, two elements that could raise the pH of the soil, into the plots.

Figure 3: The length of the plot was about 9.65 meters while the length was about 1.7 meters. 

Table 1: Professional Mulch Soil Respiration Data

Sample Site	Ring Height	Time Taken	Soil Temp.	Draeger tube %CO2	Soil Respiration	Infiltration
Row 14	15.24 cm	30 minutes	30.3oC	0.5	60.125	1 inch of water took 12 sec.

 Table 2: Pine Straw Soil Respiration Data

Sample Site	Ring Height	Time Taken	Soil Temp.	Draeger tube %CO2	Soil Respiration	Infiltration
Row I	12.7 cm	30 minutes	31.3oC	0.6	73.29537	1 inch of water took 28.1 sec.
Row J	12.7 cm	30 minutes	30.9oC	0.5	60.24345	1 inch of water took 17.3 sec.

For Tables 1 and 2, the readings for soil respiration were within an acceptable range of about 60 to 70 soil respiration. These readings display a soil that is adequate for organic blueberry plants to grow in the professional mulch plots.

Table 3: Professional Mulch Plot Data

	Sample 1	Sample 2	Sample 3	Sample 4	Group Value
pH	8.4	6.8	7.0	8.0	7.55
Nitrate Nitrogen	40	150	60	20	67.5
Phosphorus	75	25	50	25	43.75
Ammonium Nitrogen	Very Low	Very Low	Very Low	Very Low	Very Low
Humus	5	2	1	1	2.25
Nitrite Nitrogen	<1ppm	<1ppm	<1ppm	<1ppm	<1ppm

 

 

 

 

 

 

Table 4. Pine Straw Plot Data

	Sample 1	Sample 2	Sample 3	Sample 4	Group Value
pH	5.4	5.4	5.4	5.4	5.4
Nitrate Nitrogen	150	150	150	150	150
Phosphorus	200	200	150	150	175
Potassium	410	410	390	410	405
Ammonium Nitrogen	Very Low	Very Low	Very Low	Very Low	Very Low
Nitrite Nitrogen	<1ppm	<1ppm	<1ppm	<1ppm	<1ppm

 

 

 

 

 

 

For Tables 3 and 4, all results for ammonium nitrogen are very low while the readings for nitrate nitrogen are relatively high. The phosphorus results are inconsequential, being as phosphorus does not heavily effect blueberries. All potassium readings are within an acceptable range, as is calcium. No strong conclusion can be drawn from the data on humus.

Figure 4: Comparison of Professional Mulch and Pine Straw Data.

While the pH in all plots were relatively similar, the pH of the soil is always lower where pine straw was applied instead of professional mulch. In all but one plot, the nitrate nitrogen in the plots where pine straw was applied is vastly greater than in the plots were professional mulch was applied. The phosphorus levels in the plots where pine straw was applied is much greater than the phosphorus levels in the plots where professional mulch was applied.

Discussion

The health of the plots at Knoll Acers is well adapted to growing organic blueberries; the health of the plants themselves can only be concluded with  further experimentation on the plants once they grow.

Being as both pine straw and professional mulch need to be well decomposed to be beneficial, the levels of nitrogen in all plots is acceptable (Hayden, 2001). The professional mulch, however, has significantly less nitrogen in the soil that the pine straw plots do; this may effect the pH of the two plots.

Pine straw acts as a better buffer to pH than professional mulch. However, there is more nitrate nitrogen in the pine straw plots than in the professional mulch plots, so the quicker decomposition of pine straw could make it a better buffer to pH than the professional mulch, which did not have as much nitrate nitrogen to help it decompose (Kuepper and Diver, 2004).

In order to test this hypothesis, the same amount of pine straw and professional mulch should be added to separate plots and given the exact same amount of nitrogen. As a control, one plot should have nothing added to it, one plot should have professional mulch but no nitrogen, another should have pine straw with no added nitrogen and the last plot should have only nitrogen added to it. In the following weeks, multiple tests of the pH of the soil should be taken to see if a trend appears.

Also, because of the incline of the hill on which the plots were sowed, calcium and magnesium deposits filtering into the soil could raise the pH (Kuepper and Diver, 2004). The level of calcium in the pine straw plots was rather high and could be due to the fact that rain water is washing over the plot.

Testing the soil above the plots and below the plots for calcium and magnesium could strengthen or weaken this hypothesis. If the calcium and magnesium readings are higher at the bottom of the plot than at the top, then it would be likely that rain water washed the elements down hill.

As a last note, while the soil respiration is fair, it is not the best it could be. The reading for both plots was about 0.5%CO₂, which is only a 35% water-filled pore space (USDA, 2009).  The greatest percent of water-filled pore space possible is about 57%, which is about 1%CO₂. The soil temperature was slightly cooler than aerobic microbes prefer the soil to be, however it is still in the acceptable range (USDA, 2009). Both of these variables are of good quality for soil organic matter and soil respiration.

Acknowledgements

Zach Ferguson was a participant in the lab.

References

Cooperband. 2002. Building Soil Organic Matter with Organic Amendments. University of Winsconsin-Madison: CIAS

Hayden. 2001. Fertilizing Blueberries. West Lafayette, IN: Purdue University Cooperative Extension Service

ISU. 2003. Soil Quality in Organic Agriculture Systems.Ankeny, Iowa, ISU.

Kuepper and Driver. 2004. Blueberries: Organic Production. NCAT.

Pittaway. 2002. What Is A Healthy Soil? Toowoomba: USQ.

USDA. 1996. Indicators for Soil Quality Evaluation. USDA.

USDA. 2009. Soil Quality Indicators. USDA.

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