Soil

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yolo_county_soil_textures.pngCommon soil textures in Yolo County. Symbol size denotes relative abundance. The orange symbol represents a weighted average for the entire county.

Davis soils vary from moderately sandy ([WWW]Reiff Series) in south and East Davis, through loamy soils ([WWW]Yolo Series) in Central Davis, to heavy clay soils ([WWW]Caypay Series) in west and North Davis. The spatial variation of soil properties in Davis is directly related to the fluvial deposition histories of the nearby streams. The heavy soils are found where low velocity waters of Putah Creek deposited material from the Coast Range. This material is notorious for having high concentrations of exotic elements; however the local high concentration of the element [wikipedia]Boron is most likely from ground water. Sandier soils are found in locations where depositional energies were higher, or where material from the Sierra Nevada was incorporated. For specifics on the type of soil at your address, check out the [WWW]UC Davis Soil Resource Lab's Online Soil Survey.

Use as a growth media

The soils found in and around Davis are often thought of as a poor growth medium. While this may be true for an [wikipedia]uncultivated parcel of land where one attempts to plant seedlings by hand, but in terms of water storage capacity and nutrient storage the soils found here are some of the most productive in the world. The surface cracking observed in the summer is a result of the high content of [wikipedia]smectitic [wikipedia]clays, derived from weathered Coast Range rocks. The shrinking and swelling effects of these heavy clay soils ([WWW]Capay Series) not only make it difficult to plant a vegetable garden, but also wreak havoc on houses or permanent structures. By incorporating copious amounts of mulch it is possible to create a rooting environment hospitable for seedlings, while retaining the high water holding capacity and nutrient store that the local soils offer. Similarly, you can lower the rate at which house plants dry out by incorporating a small amount of local soil into existing potting mix.

pH issues

The pH of soils found in and around the city of Davis range from neutral (7) to alkaline (> 8.5). While this condition does not affect plants native to this region, many plants may not be able to readily access several key micronutrients at this pH. As a general rule of thumb, a pH near 8.2 suggests that CaCO3 is the main buffering agent, and at pH near 8.5 Na2CO3 is the main buffering agent. It is very common in this region for soils with a high pH to also have a high sodium content as well. The sodium is usually more toxic than the high pH, although at higher pH values important micro nutrients such as Iron are less available to plants.

If you were to draw a rectangle around all of Davis and surrounding sprawl you would find that on a per-area basis only about 16% of the land has a [WWW]moderately alkaline pH value (Yolo County Soil Survey).

Acres of Land Percent of Total Area Maximum pH (all horizons)
0.54 6.2
1637 1.54 7.2
1845 1.65 7.3
4091 6.11 8.5
6574 9.95 8.8
14486 14.57 8.2
19694 21.77 7.9
36891 51.54 7.5

Expected Shrink-Swell by Map Unit

Soils in Yolo County, as tabulated by expected [WWW]Linear Extensibility Percent (lep).

 musym |                                name                              |   acres | lep  | lep_class
-------+------------------------------------------------------------------+---------+------+-----------
 Ya    | Yolo silt loam                                                   |   39698 | 2.52 | Low
 Sc    | Sacramento clay                                                  |   34886 | 7.50 | High
 Ca    | Capay silty clay                                                 |   33465 | 7.50 | High
 MrG2  | Millsholm rocky loam, 15 to 75 percent slopes, eroded            |   30118 | 1.50 | Low
 Rg    | Rincon silty clay loam                                           |   24580 | 6.36 | High
 BrA   | Brentwood silty clay loam, 0 to 2 percent slopes                 |   23045 | 7.50 | High
 CtD2  | Corning gravelly loam, 2 to 15 percent slopes, eroded            |   22080 | 5.34 | Moderate
 Mf    | Marvin silty clay loam                                           |   20970 | 6.60 | High
 DaF2  | Dibble clay loam, 30 to 50 percent slopes, eroded                |   18612 | 7.11 | High
 SmE2  | Sehorn-Balcom complex, 15 to 30 percent slopes, eroded           |   17794 | 6.17 | High
 TaA   | Tehama loam, 0 to 2 percent slopes                               |   16622 | 3.75 | Moderate
 BdF2  | Balcom-Dibble complex, 30 to 50 percent slopes, eroded           |   16405 | 5.73 | Moderate
 SmD   | Sehorn-Balcom complex, 2 to 15 percent slopes                    |   16117 | 6.50 | High
 BaF2  | Balcom silty clay loam, 30 to 50 percent slopes, eroded          |   12637 | 4.50 | Moderate
 Sg    | Sacramento soils, flooded                                        |   12258 | 6.27 | High
 Cn    | Clear Lake soils, flooded                                        |   11666 | 6.92 | High
 SmF2  | Sehorn-Balcom complex, 30 to 50 percent slopes, eroded           |   11226 | 6.33 | High
 Cc    | Capay soils, flooded                                             |   11030 | 7.50 | High
 Sv    | Sycamore complex, drained                                        |    9241 | 4.18 | Moderate
 Ms    | Myers clay                                                       |    8938 | 7.50 | High
 PfF2  | Positas gravelly loam, 30 to 50 percent slopes, eroded           |    7920 | 5.34 | Moderate
 St    | Sycamore silty clay loam, drained                                |    7839 | 4.50 | Moderate
 Ck    | Clear Lake clay                                                  |    6946 | 7.50 | High
 Ra    | Reiff very fine sandy loam                                       |    6847 | 1.50 | Low
 SkD   | Sehorn clay, 2 to 15 percent slopes                              |    6069 | 7.50 | High
 Sp    | Sycamore silt loam, drained                                      |    6054 | 3.42 | Moderate
 Sa    | Sacramento silty clay loam                                       |    6023 | 6.27 | High
 DbG2  | Dibble-Millsholm complex, 50 to 75 percent slopes, eroded        |    5846 | 5.24 | Moderate
 Wb    | Willows clay                                                     |    5624 | 7.50 | High
 Sw    | Sycamore complex, flooded                                        |    5517 | 4.18 | Moderate
 Ss    | Sycamore silty clay loam                                         |    5489 | 4.50 | Moderate
 Pb    | Pescadero silty clay, saline-alkali                              |    5281 | 7.50 | High
 BaE2  | Balcom silty clay loam, 15 to 30 percent slopes, eroded          |    5192 | 4.50 | Moderate
 Yb    | Yolo silty clay loam                                             |    5040 | 4.50 | Moderate
 PfF3  | Positas gravelly loam, 30 to 50 percent slopes, severely eroded  |    4584 | 6.00 | High
 So    | Sycamore silt loam                                               |    4474 | 3.42 | Moderate
 Rh    | Riverwash                                                        |    4369 | 1.50 | Low
 Sh    | San Ysidro loam                                                  |    4289 | 4.44 | Moderate
 HcA   | Hillgate loam, 0 to 2 percent slopes                             |    4029 | 5.19 | Moderate
 Tb    | Tyndall very fine sandy loam                                     |    3726 | 1.50 | Low
 Pc    | Pescadero soils, flooded                                         |    3589 | 5.22 | Moderate
 Za    | Zamora loam                                                      |    3466 | 3.75 | Moderate
 Ob    | Omni silty clay                                                  |    3342 | 7.50 | High
 Su    | Sycamore complex                                                 |    3206 | 4.14 | Moderate
 La    | Lang sandy loam                                                  |    3001 | 1.50 | Low
 Wc    | Willows clay, alkali                                             |    2929 | 7.50 | High
 DaG2  | Dibble clay loam, 50 to 75 percent slopes, eroded                |    2874 | 7.11 | High
 Wf    | Willows clay, alkali, flooded                                    |    2816 | 7.50 | High
 Te    | Tyndall very fine sandy loam, deep                               |    2709 | 1.50 | Low
 Sb    | Sacramento silty clay loam, drained                              |    2663 | 6.27 | High
 Cb    | Capay silty clay, flooded                                        |    2410 | 7.50 | High
 AaA   | Arbuckle gravelly loam, 0 to 2 percent slopes                    |    2391 | 3.48 | Moderate
 Sd    | Sacramento clay, drained                                         |    2384 | 7.50 | High
 HdA   | Hillgate loam, moderately deep, 0 to 2 percent slopes            |    2367 | 3.63 | Moderate
 Mk    | Merritt silty clay loam                                          |    2289 | 3.57 | Moderate
 Sr    | Sycamore silt loam, flooded                                      |    2256 | 3.42 | Moderate
 Vb    | Valdez silt loam, deep                                           |    2222 | 3.42 | Moderate
 Sn    | Soboba gravelly sandy loam                                       |    2205 | 1.50 | Low
 Lg    | Laugenour very fine sandy loam                                   |    2202 | 1.50 | Low
 SlD   | Sehorn cobbly clay, 2 to 15 percent slopes                       |    2163 | 7.50 | High
 SkF2  | Sehorn clay, 30 to 50 percent slopes, eroded                     |    2155 | 7.50 | High
 Lb    | Lang sandy loam, deep                                            |    2123 | 1.50 | Low
 Mn    | Merritt silty clay loam, deep                                    |    2112 | 3.57 | Moderate
 163n  | Maymen-Millsholm-Lodo association, 30-75 percent slopes          |    2092 | 2.25 | Low
 PfE2  | Positas gravelly loam, 15 to 30 percent slopes, eroded           |    2072 | 5.34 | Moderate
 Tc    | Tyndall very fine sandy loam, drained                            |    1989 | 1.50 | Low
 Rb    | Reiff gravelly loam                                              |    1914 | 1.50 | Low
 Mo    | Merritt silty clay loam, deep, drained                           |    1858 | 3.57 | Moderate
 DbF2  | Dibble-Millsholm complex, 30 to 50 percent slopes, eroded        |    1788 | 4.47 | Moderate
 SkE2  | Sehorn clay, 15 to 30 percent slopes, eroded                     |    1775 | 7.50 | High
 Lm    | Loamy alluvial land                                              |    1708 | 1.50 | Low
 Md    | Maria silt loam, deep                                            |    1661 | 3.51 | Moderate
 Mb    | Maria silt loam                                                  |    1644 | 3.51 | Moderate
 Wa    | Willows silty clay loam                                          |    1458 | 6.36 | High
 Wm    | Willows clay, marly variant                                      |    1420 | 7.50 | High
 HcC2  | Hillgate loam, 2 to 9 percent slopes, eroded                     |    1385 | 5.10 | Moderate
 Wg    | Willows soils, flooded                                           |    1331 | 5.97 | Moderate
 AaB   | Arbuckle gravelly loam, 2 to 5 percent slopes                    |    1326 | 3.48 | Moderate
 TaB   | Tehama loam, 2 to 5 percent slopes                               |    1242 | 3.75 | Moderate
 Lk    | Laugenour very fine sandy loam, deep, flooded                    |    1180 | 1.50 | Low
 Lh    | Laugenour very fine sandy loam, flooded                          |    1172 | 1.50 | Low
 Rk    | Riz loam                                                         |    1166 | 6.00 | High
 CtE2  | Corning gravelly loam, 15 to 30 percent slopes, eroded           |    1063 | 5.34 | Moderate
 HdC   | Hillgate loam, moderately deep, 2 to 9 percent slopes            |    1060 | 3.63 | Moderate
 Mp    | Merritt complex, saline-alkali                                   |     897 | 3.57 | Moderate
 DbE2  | Dibble-Millsholm complex, 9 to 30 percent slopes, eroded         |     804 | 5.13 | Moderate
 Mc    | Maria silt loam, flooded                                         |     793 | 3.51 | Moderate
 Rn    | Riz loam, flooded                                                |     787 | 6.00 | High
 Ld    | Lang silt loam                                                   |     744 | 1.50 | Low
 Tf    | Tyndall silty clay loam                                          |     741 | 2.25 | Low
 Pa    | Pescadero silty clay                                             |     727 | 7.50 | High
 Td    | Tyndall very fine sandy loam, flooded                            |     684 | 1.50 | Low
 114n  | Bressa-Dibble complex, 30 to 50 percent slopes                   |     666 | 4.15 | Moderate
 Sf    | Sacramento clay, deep                                            |     645 | 7.50 | High
 Vc    | Valdez complex, flooded                                          |     645 | 3.42 | Moderate
 Va    | Valdez silt loam                                                 |     581 | 3.42 | Moderate
 Wd    | Willows clay, alkali, drained                                    |     566 | 7.50 | High
 Wn    | Willows clay, marly variant, saline-alkali                       |     553 | 7.50 | High
 Se    | Sacramento clay, flooded                                         |     544 | 7.50 | High
 Oa    | Omni silty clay loam                                             |     523 | 6.60 | High
 Ch    | Clear Lake silty clay loam                                       |     402 | 5.97 | Moderate
 142l  | Henneke-Montara-Rock outcrop complex, 15 to 50 percent slopes    |     366 | 4.50 | Moderate
 CrE2  | Climara clay, 2 to 30 percent slopes, eroded                     |     333 | 7.50 | High
 BaD3  | Balcom silty clay loam, 5 to 15 percent slopes, severely eroded  |     312 | 4.50 | Moderate
 154n  | Henneke gravelly loam, 30 to 75 percent slopes                   |     303 | 3.08 | Moderate
 Lc    | Lang sandy loam, deep, flooded                                   |     280 | 1.50 | Low
 BaG3  | Balcom silty clay loam, 50 to 75 percent slopes, severely eroded |     264 | 4.50 | Moderate
 112c  | Westfan loam, 0 to 2 percent slopes                              |     260 | 3.42 | Moderate
 115c  | Clear Lake clay, 0 to 1 percent slopes,occasionally flooded      |     160 | 9.59 | Very High
 166n  | Montara clay loam, 5 to 30 percent slopes                        |     145 | 4.50 | Moderate
 115n  | Bressa-Dibble complex, 50 to 75 percent slopes                   |     142 | 4.12 | Moderate
 320c  | Millsholm loam, 5 to 30 percent slopes                           |     113 | 1.92 | Low
 160c  | Grandbend loam, 0 to 2 percent slopes                            |     107 | 4.27 | Moderate
 127c  | Mallard clay loam, 0 to 1 percent slopes                         |     100 | 5.93 | Moderate
 174l  | Maymen-Hopland-Mayacama association, 50 to 75 percent slopes     |      66 | 2.75 | Low
 GP    | Gravel pits                                                      |      61 | 1.50 | Low
 114c  | Westfan clay loam, 0 to 1 percent slopes                         |      59 | 4.58 | Moderate
 188c  | Westfan loam, clay substratum, 0 to 2 percent slopes             |      58 | 4.32 | Moderate
 173l  | Maymen-Hopland-Mayacama association, 30 to 50 percent slopes     |      42 | 2.75 | Low
 280c  | Skyhigh-Millsholm complex, 15 to 50 percent slopes               |      24 | 3.59 | Moderate
 171l  | Maymen-Hopland-Etsel association, 15 to 50 percent slopes        |      24 | 2.43 | Low
 129c  | Mallard clay loam, 0 to 1 percent slopes, occasionally flooded   |      21 | 5.80 | Moderate
 108c  | Scribner silt loam, 0 to 1 percent slopes                        |      20 | 2.86 | Low
 129n  | Diablo clay, 30 to 50 percent slopes                             |       7 | 7.50 | High
 165n  | Millsholm loam, 30 to 75 percent slopes                          |       7 | 1.50 | Low
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