Purpose
Manure application has long been used as a soil amendment to supply nutrients for crop growth. However, the effects of manure on many other aspects of soil health have been less fully explored, especially in on-farm research settings. The health of soil biological communities has been shown to be positively correlated with the addition of organic materials and soil moisture. This study looked to confirm these observations in an on-farm setting using two types of organic treatments: swine manure and cedar woodchips and their impact on arthropod abundance and soil biological quality (QBS), measured through arthropod adaptations to deep soil living conditions (ecomorphological index).
What Did We Do?
12 plots were established (10 ft x 10 ft) on a commercial farm with clay loam soils, near Julian, Nebraska on a field planted in the second year of a corn-corn-soybean rotation. Plots were assigned to one of three treatments: swine slurry, swine slurry + woodchips, and control plots with no amendments with 4 replications per treatment. Swine slurry was applied at a rate of 4200 gal/ac. Woody biomass was applied at a rate of 10 ton/ac. Swine slurry was applied on all plots in April and woodchips were applied roughly 4 weeks later at the time when plots were established (Day 0).
At establishment (Day 0) and at 5 other days during the growing season (25, 54, 81, 99 and 128 days after establishment) roughly 1 gal of soil was collected from each plot by randomly sampling using a 2-in diameter sampler to a depth of 8-in. These samples were then transferred to Berlese-Tullgren funnels (Figure 1) for extraction of arthropods, a commonly used technique to assess microarthropods in the soil (Ducarme et al., 2002). A 70% ethanol solution was used to preserve the organisms for later analysis. Additionally, a 50 g subsample of the collected material was used to determine the moisture content of the soil at the time of sampling.
The QBS method of classification was employed to assign an eco-morphological index (EMI) score based on soil adaptability level of each arthropod order or family (Parisi et al., 2005). Preserved arthropods from each soil sample were identified and quantified using light microscopy. For some groups, such as Coleoptera, characteristics of edaphic adaptation were used to assign individual EMI scores for each arthropod. Each sample was then assigned a total QBS score, which is the sum of the EMI values for each category of arthropod found in the sample.
What Have We Learned?
We observed that on days when soil moisture content was higher, QBS differed significantly among treatments, while no differences among treatments were evident during periods of low soil moisture content. This indicates that soil moisture is the most important soil factor for soil arthropods collected from the top 8 in of soil because they tend to migrate away from heat and drying to more favorable conditions (cooler and wetter environment).
| Moisture % | Treatment | p-value |
|---|---|---|
| < 3.3 | CON vs SS | 0.16 |
| CON vs SSW | 0.24 | |
| SS vs SSW | 0.99 | |
| 3.4-4.0 | CON vs SS | 0.08 |
| CON vs SSW | 0.03 | |
| SS vs SSW | 0.73 | |
| 4.1-5.0 | CON vs SS | <0.0001 |
| CON vs SSW | <0.0001 | |
| SS vs SSW | <0.0001 | |
| CON=control, SS=swine slurry, SSW=swine slurry and woodchips; (p-values are shown for each comparison between treatments at different moisture content ranges) | ||
Thus, it was only when soil moisture was higher overall that arthropod populations in the soil were high enough to show a difference between treatments. For example, on day 54, a more variable moisture content of the soil was observed, with SSW, SS and CON having moisture contents of 4.16, 3.92, and 3.75%, respectively (Table 2).
| Treatment | Moisture % | |||||
|---|---|---|---|---|---|---|
| Day 0 | Day 25 | Day 54 | Day 81 | Day 99 | Day 128 | |
| CON | 4.65 | 3.43 | 3.75a | 3.95 | 4.77ab | 4.31 |
| SS | 4.63 | 3.42 | 3.92ab | 3.71 | 4.38a | 4.1 |
| SSW | 4.68 | 3.72 | 4.16b | 4.27 | 5.54b | 4.63 |
| Effect | p-value | |||||
| Moisture level | 0.47 | |||||
| Moisture*treatment | 0.05 | |||||
| CON=control, SS=swine slurry, SSW=swine slurry and woodchips; values within columns having the same superscript are not significantly different (p>0.05). | ||||||
On this same day, QBS was also significantly greater for SSW (QBS=1350) compared to SS (110) and CON (97). Similarly, on day 99 the mean moisture content for the SSW treatment (5.54%) was greater than for SS (4.38%) and CON (4.77%; p<0.05) (Table 3).
| Treatment | Day | ||||||
|---|---|---|---|---|---|---|---|
| 0 | 25 | 54 | 81 | 99 | 128 | Mean QBS | |
| CON | 156 | 115 | 97a | 141 | 105a | 150 | 127.17a |
| SS | 125 | 106 | 110ab | 135 | 135b | 140 | 125ab |
| SSW | 140 | 105 | 135b | 160 | 141b | 160 | 137b |
| QBS values having the same superscript within each sampling day are not significantly different. Absence of subscript represent no significant difference between treatments on that day (p≥0.05). CON=control, SS=swine slurry, SSW=swine slurry and woodchips. | |||||||
In general, we observed that the application of swine slurry with woodchips has a positive effect on soil quality biological index, likely because it also had a positive effect on soil moisture. The application of red cedar woodchips seemed to provide with a good habitat for soil arthropods, which in the future may increase microbial activity and soil aggregation through decomposition of organic matter and binding.
Future Plans
Further analysis will be conducted to examine the arthropod classifications and their role on nutrient cycling more closely. Future research should also seek to confirm these observations in different climates and seasons of the year to observe the efficiency of the treatments, especially woodchips, to preserve soil characteristics that are favorable to microbes and arthropods.
Author
Mara Zelt, Research Technologist, University of Nebraska-Lincoln
Corresponding author email address
mzelt2@unl.edu
Additional authors
Karla Melgar Velis, Graduate Research Assistant, University of Nebraska-Lincoln
Amy Schmidt, Associate Professor, University of Nebraska-Lincoln
Agustin Olivo, Graduate Research Assistant, Cornell University
Eric Henning, Graduate Research Assistant, Iowa State University
Additional Information
Parisi, V., Menta, C., Gardi, C., Jacomini, C., & Mozzanica, E. (2005). Microarthropod communities as a tool to assess soil quality and biodiversity: a new approach in Italy. Agriculture, Ecosystems & Environment, 105, 323-333.
Acknowledgements
Funding for this study was provided by the Nebraska Environmental Trust and Water for Food Global Institute at the University of Nebraska-Lincoln. Much gratitude is extended to collaborating members of the On-Farm Research Network, Nebraska Natural Resource Districts, Nebraska Extension Agents and Michael Hodges and family for providing the land, manure, and effort for this research project. Much appreciation to lab and field workers members of the Schmidt Lab: Mara Zelt, Juan Carlos Ramos, Nancy Sibo, Andrew Ortiz, Andrew Lutt, Seth Caines and Jacob Stover