Introduction!

Results!

Objectives!

Conclusion!

Methods!

References!

Soil samples were taken from 5 locations in each field, sampled at depth intervals of 0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, and 30-50 cm. The farmers described their land management of each field. Soil texture was estimated from NRCS soil series data. Once the soil samples were air dried, each sample was sifted to remove large rocks and debris such as plant material. About 10 grams of soil was mixed with an equal volume of deionized water. After 10 minutes, a pH meter was used to measure pH.!

The pedosphere, or soil, is the foundation for all terrestrial life. Soil is composed of minerals, gases, water, organic substances, and microscopic organisms. Soil regulates water, recycles raw materials, provides habitat, is physical support for vegetation, and regulates our atmosphere. ! !

Figure 9.2 Some pH values for familiar substances (above) compared to ranges of pH typical for various types of soils (below). Image courtesy Prentice Hall Books!

Photo courtesy of William Quirt, Marin County UC Cooperative Extension!

Photo courtesy of Justine Owen, Sliver Lab!

Factors Affecting Soil pH on Managed Dairy Fields in California!Melissa Juedemann, Justine Owen, Whendee Silver University of California, Berkeley!

Soil acidity is directly related to the amount of precipitation. Rainwater dissolves CO2 in the air and forms carbonic acid which disassociates to realize H+ ions. !

Image courtesy Lal, Kimble, and Follett; 1997!

Virtually all biochemical reactions depend on the relative quantities of H+ and OH- ions in soil. These ions are measured on the pH, potential Hydrogen, scale. pH is a logarithmic scale that expresses the degree of acidity or alkalinity. Soil pH controls soil microbe activity, nutrient exchange, nutrient availability, gaseous exchange, chemical degradation, and cation exchange capacity. H+ and OH- ions are exchangeable ions: Through ion exchange, elements such as Ca2+ and K+ are released from electrostatic adsorption on colloidal surfaces (very small particles of rock and organic matter with highly reactive electrically charged surfaces) and escape into the soil solution where plant roots can absorb them for use. ! !

Special thanks and much gratitude to everyone at Silver Lab, Chris Lever, and David McNab !

Sparlis, D.L., et all. (1996). SSSA Book Series Methods of Soil Analysis. (Vol. 3, pp 475-515). Madison, Wisconsin: Soil Science of America!Brandy, N.C., & Weil, R.R. (2010). Elements of the Nature and Properties of Soils. (3 ed.). Boston: Prentice Hall!Walworth, J.L. (May 2009). Crop Production and Soil Management Series. Retrieved from http://www.uaf.edu/files/ces/publications-db/catalog/ant/FGV-00242A.pdf!!

We expect soil texture to play a role, with higher pH in clay soils (clay enhances acid retention), and lower in sandier soil; but we found higher pH levels in the sandier soils. We hypothesized manure addition would decrease pH due to the release of organic acids during decomposition; but we found that the fields with most manure had the highest pH. This is likely due to manure adding base cations (Ca2+, Mg2+, K+, P+) which raise soil pH. Climate also plays a role: drier soils tend to have higher pH and that is what we found as seen in Dairy 5. We found that soil texture, climate, and management affect soil pH. Given the broader goal of increasing manure additions to fields, more study is needed to determine the long-term effects of management practices on soil pH.!!!

Rangelands (area used for grazing) cover about 50% of California, most of which are grasslands. While most of those grasslands are minimally managed, some are amended with manure or commercial fertilizer, seeded with forage or other crops, and/or plowed or cultivated. Research is underway to determine how manure additions to currently low- management grasslands might increase carbon storage and offset greenhouse gas emissions. We wanted to know if this change in management affects soil pH.!

This graph shows and overview of all soils tested; only a few samples had a pH value beyond the acceptable range for unimpeded plant growth. !

Each of the graphs represents one dairy farm and three different fields. The bars are the average pH with standard deviation bars. !Dairy 1: pH range: 5.25 - 6.95. Highest pH from field cultivated, sandiest, most manure; Lowest pH in field with no manure and upslope location.!Dairy 2: pH range: 4.99 - 6.37. Lowest pH in conservation field, no manure; Highest pH in heavy manure application field!Dairy 3: pH range: 7.0 – 7.2. No significant difference between fields. !Dairy 4: pH range: 6.66 - 7.35. Lowest pH in loamiest soil field; Highest pH in sandier soil field.!Dairy 5: pH range: 7.67 - 8.31. Lowest pH in field with oats, high manure, and fine soil; Highest pH in field with alfalfa. Dairy 5 is located in the driest geographical location.!!Two Primary factors affecting pH: (1) soil texture with sandier having a higher pH and (2) manure application with greater manure resulting in higher pH. Climate also plays a role. Drier soils tend to have higher pH due to CaCO3 accumulation.!

Dairy! Field! Longitude!Sand (%)*!

Clay (%)*!

Depth-Averaged

pH! Management!

1!1! -122.939! 41.4! 21.5! 5.25! no manure, grazed!2! -122.939! 41.4! 21.5! 6.02! solid manure annually, grazed!3! -122.939! 96! 2.5! 6.95! tilled and manured annually, seeded with oats and rye!

2!1! -122.822! 25.7! 27.2! 7.2! no manure, heavily grazed!2! -122.822! 25.7! 27.2! 7.0! manured, seeded, plowed and diced this year, grazed!3! -122.769! 39.4! 23.5! 6.37! seeded, no manure!

3! 1! -122.769! 39.4! 23.5! 5.33!irrigated, seeded, cow and chicken manure every year, grazed!

2! -122.769! 39.4! 23.5! 4.99! grazed, no manure (conservation area)!

4!1! -122.686! 68.8! 15! 6.85! manured annually, yeoman plowed 2009 and 2010!2! -122.686! 68.8! 15! 7.35! manured annually, sandiest!

3! -122.686! 68.8! 15! 6.66!manured annually, no-till drilled and seeded in 2010, loamiest of soils!

5! 1! -120.967! 66.4! 12.5! 8.05!commercial fertilizer, no manure in a while, cultivated (oats)!

2! -120.967! 66.4! 12.5! 7.86! liquid and solid manure annually, cultivated (oats)!3! -120.967! 66.4! 12.5! 8.31! liquid and solid manure annually, cultivated (alfalfa)!

* From NRCS Soil Survey Descriptions!

1 4

3

2

5

7!

7.2!

7.4!

7.6!

7.8!

8!

8.2!

8.4!

8.6!

8.8!

9!

0-5! 5-10! 10-20! 20-30! 30-50!

pH!

depth (cm)!

Dairy 5!

5!

5.5!

6!

6.5!

7!

7.5!

8!

8.5!

0-5! 5-10! 10-20! 20-30! 30-50!

pH!

depth (cm)!

Dairy 4!

0!

1!

2!

3!

4!

5!

6!

7!

8!

0-5! 5-10! 10-20! 20-30! 30-50!

pH!

depth (cm)!

Dairy 1!

0!

1!

2!

3!

4!

5!

6!

7!

8!

0-5! 5-10! 10-20! 20-30! 30-50!

pH!

depth (cm)!

Dairy 2!

Key: Field 1 ! Field 2! Field 3!

6.2!

6.4!

6.6!

6.8!

7!

7.2!

7.4!

7.6!

7.8!

0-5! 5-10! 10-20! 20-30! 30-50!

pH!

Depth interval (cm)!

Dairy 3!no manure, grazed!

manured, plowed, seeded, grazed!