Posts Tagged: soil
There are 4,000 species of earthworms grouped into five families and distributed all over the world. Some grow uo to 3 feet long, while others are only a few tenths of inches. We call them nightcrawlers, field worms, manure worms, red worms and some people call them little diggers.
In California, we have some native species of earthworms, but in many cases non-native introduced species have come to dominate. The predominant native species belong to the Argilophilus and Diplocardia while many of the non-native are of European in origin in the Lumbricidae family. Many of these non-natives were probably introduced by settlers bringing plants from home, which had soil containing the worms. A survey of California earthworms by the US Forest Service can be found at:
This is a wonderful description of earthworm biology and their occurrence in the landscape.
When digging in citrus orchards, it is common to find earthworms in the wetted mulch under tree canopies. Many of our citrus orchards were initially established by “balled and burlap” nursery trees that brought worms along with the soil. In the case of many avocado orchards, on the other hand, it can be rare to find earthworms in orchards. Most avocado orchards have been established since the 1970s when potting mixes and plastic liners were the standard practice and worms were not part of the planting media. Even though there is a thick leaf mulch in avocado orchards, the worms have not been introduced, and it is rare to find them.
Numerous investigators have pointed out the beneficial effects of earthworms on soil properties. One of the first of these observers was Charles Darwin who published Earthworms and Vegetable Mould in 1881. He remarked on the great quantity of soil the worms can move in a year. He estimated that the earthworms in some of his pastures could form a new layer of soil 7 inches thick in thirty years, or that they brought up about 20 tons of soil per acre, enough to form a layer 0.2-inch-deep each year.
Earthworms, where they flourish, are important agents in mixing the dead surface litter with the main body of the soil. They drag the leaves and other litter down into their burrows where soil microorganisms also begin digesting the material. Some earthworms can burrow as deeply as 5 to 6 feet, but most concentrate in the top 6 to 8 inches of soil.
The worm subsists on organic matter such as leaves and dead roots near the soil surface. The earthworm ingests soil particles along with the organic matter and grinds up the organic matter in a gizzard just as a chicken does. This is excreted in what we call worm casts. The castings differ chemically from the rest of the soil, as they are richer in nitrogen, potassium and other mineral constituents.
Castings are a natural by-product of worms. When added to normal soils in gardens or lawns, they provide the same kinds of benefits as other bulky organic fertilizers. Castings today are not commonly used as fertilizer by commercial plant growers because of their cost relative to other fertilizers. However, castings are used by some organic growers and are sold commercially as a soil amendment or planting medium for ornamental plants grown in pots.
The physical soil churning process also has several important effects:
-Organic residues are more rapidly degraded with the release of elements such as nitrogen, sulfur and other nutrients.
-Some of the inorganic soil minerals tend to be solubilized by the digestive process.
-Extensive burrowing improves soil aeration.
-Burrowing can improve water penetration into soils
-The earthworm carries surface nutrients from the soil surface and imports them into the root zone of the plant.
Although earthworms are considered beneficial to soil productivity, few valid studies have been made to determine whether their presence will significantly improve plant growth. This may seem odd since many of us have learned from childhood that worms are good. It is something like the chicken and the egg analogy. The conditions that are conducive to earthworms are also ideal for plants. Both plants and worms need temperatures between 60 and 100 degrees F for good growth; both need water, but not too much or little; they both require oxygen for respiration; and they do not like soils that are too acid or basic or too salty. By correcting soil conditions that are unfavorable for one will also improve the outlook for the other. The earthworm is a natural component of the soil population. If the soil is properly managed this natural population will thrive. In this sense, the presence or absence or earthworms can be an indicator of the "fertility" of one's soil.
At the recent HLB Conference in Florida a paper was given that reinforces the need for appropriate soil and water pH to maximize root density and tree health. The industry there is dominated by a range of rootstocks and by Valencia-like varieties. Jim Graham and colleagues have shown that pH contributes to orchard health in their HLB situation. This should be a reminder for California growers for general tree health. Florida soils tend to be more coarse than soils found in many California orchards. It's much harder to change soil pH with acidified irrigation water with heavier textured soils.
4.b.1 Soil and water acidification sustain root density of huanglongbing-infected trees in Florida
Jim GRAHAM, Kayla GERBERICH, Diane BRIGHT, Evan JOHNSON
University of Florida, Citrus Research and Education Center, Lake Alfred, Florida, USA
Abstract: Early symptoms of HLB include fibrous root loss and leaf blotchy mottle, followed by premature fruit and leaf drop, and yield decline. As a consequence of initial bacterial infection of fibrous roots, a 30-50% reduction in fibrous root density and elevated soil Phytophthora populations were detected in field surveys. Continued sampling of Hamlin and Valencia orange trees on Swingle citrumelo rootstock in different stages of HLB decline revealed that root loss occurs in two stages. The second phase of root loss (70-80%) begins at the early stage of tree canopy thinning resulting from leaf drop and branch dieback. A more extensive survey of HLB-affected groves indicated that greater decline in fibrous root health and expression of HLB symptoms is observed where irrigation water is high in bicarbonates (> 100 ppm) and/or soil pH > 6.5. HLB symptom expression of trees on different rootstocks follows the known intolerance to bicarbonate (Swingle citrumelo > Carrizo citrange > sour orange > Cleopatra mandarin). Acidification of irrigation water in central ridge and south central flatwoods Valencia orange groves on Swingle citrumelo rootstock for three seasons has maintained soil pH below 6.5 on the flatwoods and 6.0 on ridge. Over the last three seasons of survey, root density as an index of root heath has been sustained. Phytophthora populations remain below the damaging level in ridge groves and in flatwoods increase to damaging levels coincident with the fall root flush but drop back to non-damaging levels for remainder of the season. Compared to the 2013-14 season, yields in the ridge blocks have increased up to 4% and on the flatwoods have increased up to 22%.Growers using acidification treatments with sulfuric and/or N-phuric acid for the last 3 seasons report an average cost of $60 per acre. This cost will analyzed in relation to yield response to provide a cost benefit of acidification
Non-Technical Summary: Managements have been implemented to reduce soil, nutrient and water stress, and Phytophthora root rot. They include frequent irrigation cycles, fertigation and acidification of irrigation water and soil to reduce rhizosphere pH, and fungicides. Root density of trees under these practices fluctuates seasonally and annually but has not declined over the past 3 years. Trees managed with soil acidification and fertigation have steadily recovered in health and yield.
Many states have a designated state bird, flower, fossil, mineral, etc. In California, the state bird is the California Valley Quail, the state flower is the Golden Poppy, the state fossil is the Sabertoothed Cat, and the state mineral is Native Gold. The state rock is Serpentine which contains chrysolite asbestos which is a carcinogen. It's a beautiful rock, though.
The state soil is the San Joaquin series. The series concept is that a given soil has certain properties like pH, depth, color, texture, etc. that distinguishes it from other “soils” or series. So wherever this soil is found it is given the same name. San Joaquin series is a soil that is found primarily along the foothills of the Sierras in the Central Valley. The name comes from where it is first described, in this case, San Joaquin, but it is found in other places. Yolo series is named after a soil on the campus at UC Davis in Yolo county, but it is also found in San Diego county, and in other states.
A description of the state soil can be found at the link below, as well as the state soils in other states:
Soils can be highly variable depending on the context in which they are found. Going to flat old Kansas which is actually flatter than a pancake (http://www.usu.edu/geo/geomorph/kansas.html), the variability from spot to spot across miles can be minimal. But going to a place like Ventura, Santa Barbara, San Luis Obispo Counties of the Sierra foothills, you can't step on the same soil twice. That's because of the terrain and landforms. Where there is natural erosion (yes, it doesn't take humans to cause erosion) or accelerated erosion (this is where humans have often changed the landscape with roads, houses, removing ground cover) soil gets moved around and deposited in different positions and over time forms different soils with different properties. On large tracts of land that have not been altered much, such as avocado orchards, the naturally formed soils can be seen. In a housing tract where soil has been moved around to level and compact housing pads, it is often hard to find a natural soil because it is so highly disturbed. The soil can have been moved from one end of a 100 acres tract to the other with big equipment. It's all one big homogenous mix down to several feet at times depending on the slope.
In many cases, it is still possible to see the natural soils and knowing their series classification, it's possible to learn some of the properties and some of the problems that will be encountered when working with them. Knowing the pH prior to working it means that it could be adjusted before planting. It's a whole lot easier to adjust before planting than when the plants are in the ground.
You can see the soils in your area by going to the USDA-NRCS (Natural Resources Conservation Service) website - https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm - and typing in the area code to find the soil at a given site. It probably isn't the state soil series, but it's your soil series.
For a great text on understanding soils, check out Soils: An Introduction by Michael Singer and Don Munns.
California Gov. Jerry Brown has included $7.5 million in the 2017-18 budget to launch the Healthy Soils Initiative, reported Bob Gore in a commentary on Techwire.net.
The story said CDFA secretary Karen Ross announced the development at a recent meeting, saying "We're starting from the ground up."
Carlos Suarez of the U.S. Natural Resources Conservation Service was also quoted in Gore's story. Suarez said the funding puts "soils back into the forefront of agriculture. Feeding the people is the real issue. We have to take care of our soils."
Jenny Lester Moffitt, CDFA deputy secretary and walnut farmer, is the point person for the Governor's Healthy Soils Initiative, which formally starts Jan. 19. Moffitt said the $7.5 million will fund research and demonstration projects so the "UC Ag and Natural Resources engine will rev up."
California's Healthy Soils Action Plan notes that the new initiative will "provide boots-on-the-ground" research, education and technical support to the agricultural industry.
"Utilizing partners such as Natural Resource Conservation Services, University of California Cooperative Extension and Resource Conservation Districts, (the initiative will) enhance and expand technical assistance and outreach activities to distribute new and existing management practice information to farmers and ranchers," the action plan says on Page 5.
A recent website just posted hopes to make research papers available to the general public. Many times these papers are locked away in archives or libraries and are hard to access. This website wants to change that. It is sponsored by various group0s, including USDA, University of Missouri, industry, Resource Conservative Districts and other entitites. It's a small data base at this point, but hopes to build over time. check it out:
There's a lot of distracting stuff at the site, but the guts are at
Other good ag websites are the USDA's National Ag Library:
USDA's ATTRA which is loaded with basic and detailed farming information:
USDA's Farming Information Center
It's a new year, READ ON!!!!