Deep Placement of Compost

PROJECT BACKGROUND
Our farm operation consists of the home farm, a quarter section with 142 tillable acre, and an adjoining farm which we rent, which has 120 tillable acres and 46 acres of woods and pasture. My wife and I moved here form Washington State in 1999 and began farming at that time. The home farm has a long history in my family. Currently it is farmed in partnership with my brother. Corn and soybeans are grown in a 2-year rotation except where mixed grass/alfalfa hay has been included for 2-3 years in the rotation. A small beef cow herd is maintained to make full use of the pasture on the rented farm. The calves have generally been fattened on the farm rather than sold as feeders. Enough hay is raised that most of it is sold off the farm. This has permitted rotation of hay around most of the farm, since no hay had previously been grown here for many years.

Since conventional equipment was the least expensive to acquire, farming practices began quite conventionally. This also allowed me time to assess the many different options that required different complements of equipment before committing to expensive equipment purchases. The last few years’ crops have been planted no till or minimum till using strip tillage. No fall tillage allows cattle to graze and glean the corn fields in the winter, which adds value to the corn stover. Our planter is equipped for no till planting. Soybeans have been custom no till drilled. Strip tillage has been hired. This has been satisfactory and has also kept out options open for making changes. Assessment is ongoing.

The motivation for the project that was conducted with our SARE grant is explained below. But certainly part of it involved finding a way to apply manure in a minimum or no tillage situation that would conserve nitrogen and prevent erosion loss as can easily happen with surface application without incorporation.

Cooperators:
- George Cummins, Area Crop Specialist
- Neil Wubben, Mitchell Co. Extension Director
- Sandie Adams, Mitchell Co. Soil and Water Conservation District.
- Dr. Richard Cruse, agronomy professor, Iowa State University
- Dr. Mark Hanna, agricultural engineer, Iowa State University

INTRODUCTION
Soil compaction limits yields on most farms. Efforts to ameliorate compaction by subsoiling often results in using larger machinery and can end up exacerbating the problem. The effects of subsoiling are deleterious if the soil is too wet when the tillage is done, but even under optimal conditions the effects are only temporary unless the practices leading to the compaction are changed. Controlled traffic patterns, which are used in no tillage, ridge tillage or zone tillage, are maintained to limit soil compaction beneath the crop rows. However, lateral compression beneath tractor and implement tires can still substantially compact soil. The purpose of the research conducted with this SARE grant was to enhance and sustain the effect of subsoiling beneath the row area by applying composted manure in the subsoiled zone to prevent the fractured layer from recompacting. Development of a deep and friable rooting zone to a depth of about 15 inches should result in substantial yield improvement. Fertilizer nutrients placed in this zone should help encourage deep root development, which would also help to maintain good tilth in the zone. Plant residue or raw manure could be used as an alternative to composted manure, but the effects of compost would be sustained longer because if it’s biological stability. Increasing the bedding content in the manure to compost would decrease the nitrogen availability by increasing the C: N ratio. This would allow higher rates of compost addition without excessive available N application. Composted manure also has an advantage over raw manure due to its low oxygen demand for decomposition in the poorly aerated environment of the subsoil. Alleviating compaction in this way could be accomplished without aggressive annual tillage that leaves bare soil exposed during the no cropping season and without mixing subsoil with surface soil as would occur with deep inversion plowing. By keeping the subsoiled zone friable, controlling wheel traffic in the field, and doing surface tillage only in the crop row area, subsequent tillage should be easier to perform, require much less horsepower and fuel, and deep tillage should be required much less frequently.

Anticipated economic impacts of this research include effects on cost of production as well as effects on crop yield. The field experiment was designed to assess the effects on crop yield, which is the most immediate benefit. Some short-term effects on costs of production can be assessed by coupling well-established data on costs of the tillage operations used with economic evaluations of composting vs. direct field application of animal manure. But the total costs cannot be fully evaluated in a short-term experiment because the benefits of a single deep placement of compost at a high rate will be long-term. Long-term benefits include decreased requirement for subsequent deep tillage and decreased draft requirements when it is deemed to be beneficial because of the improved soil tilth, as well as continued higher crop yields because of the improvement in the rooting environment beneath the row. These long-term benefits can only be determined by subsequent studies. The impact on the environment is due in large measure to the deep placement of the compost rather than surface application of manure where it is subject to erosion. The social impact follows from the environmental and economic benefits. If the practice of deep placement of compost increases crop yields while decreasing long-term requirements for fuel and tillage, then the economics of farming are improved.

The problem of compaction is certainly a concern throughout the North Central Region, but it is far more ubiquitous as well. It can be even more sever in regions that do not experience the deep frozen soils that we often have here in north Iowa. Increased yields and better utilization of livestock manure would benefit farmers economically and everyone environmentally. I consulted with Dr.’s Mark Hanna and Richard Cruse from Iowa State University regarding their evaluation of the merits of this project as well as their knowledge of previous research that would preclude the need for the research. While they were aware of prior research that may have some similarity to this project, the similarity is difficult to assess because none of the publications they found were available to them on campus. They both agreed that more work in this area should be done.

The grant was used to: a) purchase compost, b) purchase the implements that will be modified to apply the compost, c) offset some of the cost of modification and fabrication, and d) offset some of the cost of a field experiment to evaluate the effectiveness of deep placement of the compost. Benefits derived from the incorporated compost were evaluated in a replicated field experiment of two years duration. This report describes the production of the compost, the equipment that was used to apply the compost, and the field experiment.

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Compost Preparation:
The compost was made under cover in a hoop hog-house in what was essentially a static pile in which straw bedding was added periodically for the hogs over a long period. This was followed by storage outside in a long windrow about 10 to 12 ft. high. It was then brought to the experiment site and further composted with more aggressive turning to accelerate the composting process. Approximately six weeks prior to applying the treatments the compost was spread out to dry so that it could be ground for ease of application. Shortly before application the quantity of compost was judged to be inadequate for the experiment, so it was diluted with composted cattle manure in a ratio of 4:1 (hog manure compost: cattle manure compost).

We benefit from the dry late summer in 2003, which made it possible to spread out the compost on concrete cattle yards to dry. It occasionally had to be piled under cover when the rain chance was high enough. But it was dry for long enough to reduce the moisture content sufficiently to easily pulverize the compost to a very friable state. Prior to spreading the compost out to dry, it was processed through a side-slinger type manure spreader, which ground the compost as it was discharged. Well-composted cattle manure was mixed with the hog manure compost in a forage wagon by layering the two composts in the forage wagon and discharging them into a pile. Good vertical mixing of the layers was accomplished in this way. Alternately spreading and piling the compost for periodic rainfall events also helped to blend the compost mixture. It should perhaps be acknowledged that this kind and degree of handling would be prohibitive in normal practice, but the emphasis in this research was to evaluate the agronomic merits of compost application in the proposed manner. Demonstration of agronomic advantages could then be followed by research on the methods of application. A private laboratory analyzed compost samples. The nutrient analysis of the compost mixture on a dry matter basis is as follows:

% Moisture, % Total N, % P2O5, %K2O, %Amm-N, %Org-N, pH
17, 1.33, 1.73, 1.58, 0.148, 1.19, 8.94

Field Experiment and Equipment Used:
The field experiment was conducted on our home farm on a Franklin slit loam soil near Osage, IA. The site was approximately 6 acres. Soil pH was >6.0 and P and K levels in the soil were at or above the optimum levels recommended by Iowa State University. Drainage tile had been installed in the field in 2002. The experiment site drained quite slowly prior to 2002, which made it more prone to soil compaction. The field has a long history of row cropping; but alfalfa/grass hay was established for two years before the experiment began .the site was sprayed with glyphosate (41%) at a rate of 48 oz./acre on September 24. the compost and fertilizers were applied November 21, 2003. the experimental treatments are as follows:

Treatment #, Compost rate (T/ac), Subsoiling, Fertilizer placement
1, 0, No, Surface
2, 0, Yes, Surface
3, 0, Yes, Subsoiled
4, 3.7, Yes, Subsoiled
5, 5.5, Yes, Subsoiled
6, 11, Yes, Subsoiled

Treatments 1, 2, and 3 are controls without compost application. Treatment 1 vs. 2 was to evaluate the effect of subsoiling. Treatment 2 vs. 3 evaluated the effect of fertilizer placement. Treatment 3 vs. 4, 5 and 6 tested the effects of adding compost at different rates into the furrow behind the subsoiler. The experimental site was quite uniform, so a completely randomized design was used. Each treatment was replicated three times. A random number table was used to assign plot sequence. The low and high compost rates were applied first. There was only enough compost left for two of the three reps of the intermediate rate.

The equipment purchase and modification requirements for subsoil application of the compost were minimal. A used three-point toolbar was purchased, and two auto-reset subsoiler units were donated. New shanks and points were purchased for the subsoiler units. Long and narrow drop tubes were fabricated and fastened behind each subsoiler shank. The top dimensions for the drop tube were 2 inches wide and 10 inches long. Where the drop tube attached to the subsoiler shank, the drop tube extended down to the bottom of the shank (to a depth in the soil of about 15 inches). The bottom of the drop tube was tapered upward toward the rear at about a 45 degree angle. In this way it was intended that the soil would close behind the drop tube at different depths along its length as it traveled through the soil, and the material delivered into the drop tube would be distributed vertically. Funnels were made from sheet steel and attached to the top of each drop tube.

A hitch was welded onto the right end of the toolbar for a forage wagon to be towed. The forge wagon carried the compost in the field and was calibrated to deliver it to the subsoiler at the prescribed rate. The hitch was oriented on the tool bar so that the wheels of the forage wagon would track between rows and the discharge point of the forage wagon would be alongside the subsoiler units. As the compost came off of the incline web of the forage wagon onto the discharge web a portion of the compost was directed to the front of the discharge web using sheet metal. This better distributed the compost on the discharge web so that it could be evenly divided to the two subsoiler units. As it was discharged the compost was divided into two pipes, which directed the two streams to their respective subsoilers. A dry fertilizer hopper was mounted on top of the tool bar. Tubes leading from the fertilizer hopper were inserted into the drop tubes so that fertilizer could be added simultaneous to compost application. Both the fertilizer hopper auger and the forage wagon were driven by hydraulic orbital motors, which were independently controlled at the tractor so that a constant rate of fertilizer could be maintained while varying the rate of compost application. The rate of discharge of each unit was calibrated to the tractor ground speed to apply the desired rate of fertilizer and compost. An unanticipated complication of the application system was that the wheels of the forage wagon would fall into the ruts made by the subsoiler in a previous pass. This would result in misalignment of the discharge tubes and the funnels on the subsoilers. It was necessary to begin application at the center of the plot and work toward the outside so that the wheels of the forage wagon stayed on smooth and firm ground. It also became necessary to shift the plot layout so that there was always firm soil for the forage wagon to roll on. This was possible because there were most plots planned for in the experimental design than were used.

After harvest in 2004, the soil was excavated from an inspection pit in the high compost treatment. The compost had accumulated largely at the bottom of the furrow that was opened by the subsoiler and drop tube at a depth of 11 to13 inches. Although the intent was to place the compost in a vertical band from about 5 to 15 inches, the depth achieved should be below the tillage pan on this site. In hindsight, the furrow opened by the subsoiler probably would have remained open long enough for the compost to be injected without the need for a drop tube. This would eliminate the potential for plugged tubes and may result in the vertical distribution that the drop tube that was fabricated for the experiment was intended to accomplish.

Phosphorus, potash, and micronutrients were applied in the fall during compost addition at high enough rates to ensure adequate levels of applied nutrient to sustain crop growth during both years of the experiment. Because the purpose of the experiment was to evaluate the physical effects of deep placement of the compost rather than the fertility benefits, attaining a high level of fertility in all treatments minimized effects due to fertility benefits of compost addition. The fertilizer was a mixture of di-ammonium phosphate, potassium chloride, elemental sulfur, zinc sulfate, and sodium borate (59-150-150-30-10-2; N-P2O5-K2O-S-Zn-B), and was applied at a rate of 700 lbs/acre. Fertilizer nutrients were distributed in deep bands through the same openers through which the compost was applied, with the exception of the two controls with and without subsoiling (treatments 1 and 2) where the fertilizer was broadcast on the surface.

A high nitrogen fertilizer rate (200lbs. N/acre as urea) was applied to all treatments on April 17, prior to planting the corn, to assure that N fertility did not limit crop growth. A field cultivator was used for shallow tillage to prepare a seedbed April 29. The plots were planted May 3, 2004 with corn (Pioneer 36R11). A Bt variety of corn was chosen for protection from corn borers that could confound treatment results. The seeding rate was 35,600 seeds/acre. The plant population was 34,500 plants/acre, which was determined by counting the number of plants in 100 ft. of row. Plots were 20ft but 500ft. Each plot consisted 8 rows. Field operations following planting were carried out using controlled traffic patterns to prevent driving on the rows. To minimize the effects of drainage tile, plots were arranged so that rows ran perpendicular to tile lines. The plots were sprayed with a full recommended rate of Accent and a half rate of Northstar herbicides on June 8. Weed control was very adequate. Corn grain was harvested with a combine on October 21. The center 6 rows of each 8 row plot were sampled by combining the entire length of the plot. Grain yields were determined using a weigh wagon. Moisture contents and test weights were determined at the time of harvest.

Precipitation data was taken from the rain gauge on the farm near the experiment site as well as form the City of Osage weather station about 8 miles from the experiment site. The 54 year means for precipitation were for the weather station in the City of Osage, IA.

Following harvest, strip tillage was done in the entire plot area in preparation for the 2005 season. Strip tillage was chosen over plowing to keep from moving too much soil, which might disturb the fertilizer and compost placement. Because the quantity of residue was too high to strip till into the fall, corn stalks were removed at a rate of about 3.5 T/ac. Additional P and K fertilizers were applied to compensate for nutrient removal in the stalks corresponding to a stalk removal rate of 6 T/ac.

The corn was planted on May 5 in 2005 at the same population as tin 2004 into the strips tilled after the previous year’s crop. Since strip tillage in the same cornrows was too difficult, the strips were made alongside the cornrows. Two hundred pounds N/ac as urea was broadcast applied prior to a one-inch rainfall that leached the N into the soil. Pioneer 36B11 corn (a Roundup-ready variety) was ordered with Poncho 1250 treatment applied to the seed for rootworm control since corn was grown the previous year. A single application of glyphosate at a rate of 2 qt/acre when the corn was about a foot tall provided adequate weed control.

Results and Discussion:
Corn yields in the controls (treatments 1-3) did not respond to fertilizer placement or subsoiling. Although there appeared to be a small yield response to compost addition, it did not seem to significant based on preliminary statistical analysis. Average yields were as mush as 6% higher as a result of compost addition, but variability within treatments was too large for treatment differences to be statistically significant at less than the 10% level. After a hand calculation of the analysis of variance of the 2004 data illustrated a lack of significance, a decision was made to dispense with the expense of statistical analysis by the university.

Treatment#, rep 1, rep2, rep3, mean
2004
1, 210 ,218, 213, 214
2, 215, 213, 205, 211
3, 210, 204, 216, 210
4, 219, 221, 217, 219
5, 218, 222, ,220
6, 210, 223, 212, 215

2005
1, 195, 212, 204, 204
2, 189, 198, 218, 202
3, 194, 207, 162, 188
4, 204, 214, 197, 205
5,206, 216, , 211
6, 210, 196, 194, 200

Because of excessive rainfall, it was possible very early in the 2004 growing season to see faster corn growth over the drainage tile lines in plots that were not subsoiled. As the soil drained and temperatures warmed the corn growth became more even, and during most of the growing season the only observable differences in corn growth corresponded somewhat to improved growth in treatments with surface applied fertilizer. By September 1 corn development was well behind schedule because of the cool temperatures, but substantially above normal temperatures in September helped to mature the crop before the killing frost on October 2. by the end of the growing season treatment differences could not be easily observed. Although corn growth generally appeared to be uniformly excellent there were areas of lodging caused by Anthracnose-weakened stalk breakage that made harvesting difficult. There was no apparent correlation between degree of lodging and treatment.

By late in the 2005 growing season lodging was again occurring. Unlike the first year in which lodging was caused by diseased stalks breaking, unusually high rootworm pressure in 2005 overwhelmed the ability of the seed treatment to protect the plant. Abnormally high rootworm pressures even in first year corn were a problem throughout our area in 2005. as in 2004, the degree of lodging could not be correlated with treatment. Although lodging was a complicating factor in the interpretation of the results in both years, it was not considered to be excessive enough to expect that different conclusions would have been significant if not for the complicating effects due to lodging; there is no clear pattern that emerges in the yield data from either year of the experiment.

Excessive rainfall in both years, on the other hand, was considered to e a more unfortunate stroke of luck. From March through September rainfall was 42% greater than normal in 2004 and 23% greater in 2005 according to the weather records in the city of Osage, which is eight miles away. Farm rainfall records tallied to 63% more than normal in 2004 and 29% more in 2005. Most of the root growth may have been confined to the surface where better aeration existed, and even when the weather became drier the rainfall was frequent enough to maintain enough moisture in the surface soil to prelude the need for deep root development. Since the intent of the injection of compost behind the subsoiler was to keep a friable channel in the soil for root penetration into the subsoil for access to nutrients and moisture, it was necessary to have growing seasons in which deep root penetration provided an advantage to the plant. Excessive soil moisture in parts of both years and sufficiently frequent rainfall events throughout the growing season probably prevented moisture stress form occurring in the topsoil. The unusually wet conditions during both growing seasons raise questions about the potential for greater response in a more normal or abnormally dry year in which the corn roots would have more incentive to search for moisture and nutrients in the subsoil.

April, May, June, July, August, Sep., Total, % above 54 year mean
2004
2.43, 11.42, 3.56, 9.62, 4.41, 3.56, 35, 42%
2005
3.75, 5.59, 6.57, 4.8, 3.17, 6.34, 30.19, 23%
54 year mean
3.26, 4.18, 4.67, 4.65, 4.38, 3.19, 24.63

Another important factor for interpretation of the results is that the experiment site may not have been compacted to the extent that a yield response resulted from subsoiling. Not all soils will respond to subsoiling or deep ripping. Not all soils that respond in some years will respond every year. The site was chosen because it is the most compacted site on this farm and has had traffic on and tillage done when the soil was too wet in many years prior to the installation of drainage tile four years ago. The experimental site will be returned to a corn/soybean rotation for the near future. In the years in which corn is grown, the rows can be aligned over the treatments as was done during the two years of the experiment. If treatment differences occur during dry years, the combine yield monitor will be able to document enhanced yields large enough to warrant further experimentation.

Conclusions:
Corn yield potential was very high in both the 2004 and 2005 growing season and corn yields were excellent across treatments. Both growing seasons were excessively wet. Because the abundant rainfall probably precluded the reliance of corn roots on subsoil moisture or nutrients, the lack of yield response to deep placement of the compost cannot be constructed as a failure of the concept of work. Because the compost residues are likely to remain in the soil for a number of years, there is still the opportunity to assess treatment effects in the coming years by using the combine yield monitor during corn harvests. Should such yield responses occur, NCRSARE will be notified of the results.

OUTREACH
Since the weather conditions required to make a good assessment of the deep compost placement did not occur in either year, there were no results that were considered worthy of the original plans for outreach. Prior agreements had been arranged with Mitchell County Extension Director, Neil Wubben, for organization of a field day. The tour, which would have included a visit to our plots. Successful results would have had much wider application as well. Under the circumstances, the most prudent way to make the project known is through an annual publication called Hub and Spoke. George Cummins, Area Crop Specialist for Iowa State University, will receive a copy of this report and has agreed to include a summary of the project in the next edition, which goes to press in December. Since results from the high rates of compost may be long lasting the site will be monitored using the yield monitor in our combine. If in a drier year positive results are apparent, further evaluation will be warranted.