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Baseline Soil Physical Properties of the Sites in the Biofuel Production Study: Streeter Location Report

Dr. Kristine Nichols, Soil Scientist, USDA-ARS, Mandan, ND


Editor’s note: The following report discusses three soil characteristics: aggregate size, aggregate stability, and glomalin content. Glomalin is an important factor in both soil quality and carbon storage. Discovered by ARS soil scientist Sara F. Wright in 1996, this protein is produced by mycorrhizal fungi in soil and roots. Glomalin binds organic matter to the soil particles and also clumps the soil particles together into aggregates. This structuring helps to maintain soil quality and keeps soil carbon in the soil. Because glomalin itself is made up of 30 to 40 percent carbon, it may account for nearly a third of the carbon stored in soils.

Kristine Nichols is a former colleague of Wright’s at the Sustainable Agricultural Systems Laboratory in Beltsville, MD, and is continuing her research at the USDA-ARS in Mandan.


Introduction

In May 2006, a study was initiated at five locations (six sites) in North Dakota to evaluate ten perennial grasses for biofuel production and carbon sequestration. Prior to seeding, soil samples were taken from each of the 20 plots at each site to collect baseline data on physical and chemical properties of the soil. This report is a portion of that study.

Methods

Soil samples were collected at 0-2 and 2-4 in. depths in May 2006 prior to planting. At the Northern Great Plains Research Laboratory, these samples were gently broken up along natural fracture lines, and air-dried. After drying was complete, three aggregate size classes (0.079 to 0.039, 0.039 to 0.010 and 0.010 to 0.002 in.) were separated from each sample by passing the samples through a series of screens. The weight of soil in each aggregate size class was measured (Figures 1 and 2). (Williston 5A was irrigated; 5B was dryland).

Each aggregate size class was analyzed for water-stable aggregation (WSA) (Kemper and Rossenau, 1986) (Figures 3 and 4) and glomalin concentration (oz. per lb. aggregates) (Wright et al., 1996; Wright et al., 2006). A stability index was calculated by combining the values for the weight in each size class and WSA (Figures 5 and 6) (Nichols and Toro, in review).

 

Figure 1. Percent aggregate weight of soil from the 0-2 in. depth at six sites in North Dakota. No statistical differences between the plots at the individual sites were found, but there were differences between the aggregate sizes with the 0.039 to 0.010 in. size class having the highest percentage weight (P <0.0001).

 

Figure 2. Percent aggregate weight of soil from the 2-4 in. depth at six sites in North Dakota. No statistical differences between the plots at the individual sites were found, but there were differences between the aggregate sizes with the 0.039 to 0.010 in. size class having the highest percentage weight (P <0.0001).

 

Figure 3. Percent water-stable aggregation of soil from the 0-2 in. depth at six sites in North Dakota. No statistical differences between the plots were found, but differences did occur between the aggregate sizes with the 0.039 to 0.010 in. size class having the highest percentage (P <0.0001), and between sites, with Streeter having the highest values (P <0.0001).

 

Figure 4. Percent water-stable aggregation in soil from the 2-4 in. depth at six sites in North Dakota. No statistical differences between the plots at the individual sites were found, but there were differences between the aggregate sizes with the 0.039 to 0.010 in. size class having the highest percentage (P<0.0001), and between sites, with Streeter having the highest values (P<0.0001).

 

Figure 5. Stability index of soil from the Streeter site from two depths (0-2 and 2-4 in.) and from the 20 plots was calculated by combining the aggregate weight and water-stable aggregation values with a quality factor. No statistical differences in the stability index were found between these samples.

 

Figure 6. Stability index of soil from six sites in North Dakota. No statistical differences between the plots and the two depths at the individual sites were found, but there were differences between the sites (P <0.0001), with the Streeter location having the highest values.

 

Results and Discussion

Since the samples were collected prior to planting the research plots in 2006, and all sites were cultivated the fall prior to sampling, no statistical differences were expected between values from an individual site (as seen in Figure 5). The data showed that this was true, but there were some differences between sites (Figures 1-4 and 6). The 0.039 to 0.010 in. aggregate size class tended to have the highest percentage weight of the three size classes, as well as the highest percent of WSA at both depths and from all sites. Soil from the Streeter site had the highest percentage of WSA at both depths (Figures 3 and 4), and the highest stability index (Figure 6).

Unfortunately, not all of the glomalin data has been collected yet, but the data collected so far indicates no statistical differences between plots (treatments) or depths, but there were differences between sites. Preliminary glomalin data for the Streeter location showed that samples from this site had some of the highest glomalin values with 0.065 and 0.062 oz. of glomalin per lb. in aggregates at the 0-2 in. and 2-4 in. depths, respectively. The WSA and glomalin values are similar to those measured in 30 year-old crested wheatgrass plots near Akron, CO (Wright and Anderson, 2000), as well as other values reported for an undisturbed grassland in MN (Wright and Upadhyaya, 1998).

Click here for more information on glomalin and carbon storage


References

Kemper, W.D., and R.C. Rosenau. 1986. Aggregate stability and size distribution. p. 425-442. In: Klute, A., (Ed.) Methods of soil analysis. Part 1 – Physical and mineralogical methods. 2nd ed. SSSA Book Series No. 5. SSSA and ASA, Madison, WI.

Nichols, K.A. and M. Toro. A new index for measuring whole soil aggregate stability. Soil Sci. in review.

Wright, S.F., M. Franke-Snyder, J.B. Morton, and A. Upadhyaya. 1996. Time-course study and partial characterization of a protein on hyphae of arbuscular mycorrhizal fungi during active colonization of roots. Plant Soil 181: 193-203.

Wright, S.F. and R.L. Anderson. 2000. Aggregate stability and glomalin in alternative crop rotations for the central Great Plains. Biol. Fertil. Soils 31: 249-253.

Wright, S.F., K.A. Nichols, and W.F. Schmidt. 2006. Comparison of efficacy of three extractants to solubilize glomalin on hyphae and in soil. Chemosphere. 64 (7): 1219-1224.

Wright, S.F., and A. Upadhyaya. 1998. A survey of soils for aggregate stability and glomalin, a glycoproteins produced by hyphae of arbuscular mycorrhizal fungi. Plant Soil 198: 97-107.


NDSU Central Grasslands Research Extension Center
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