- Author: Dan Macon
After several multi-year droughts over the last decade, I find myself puzzled by the moisture that's been falling from the sky here in Auburn this winter! I find myself even more puzzled by the saturated state of our foothill soils! Over the last several weeks, as I've driven Highway 49 between Auburn and Sonora, I've seen creeks running that haven't flowed in the last several years. After years of worrying about drought and wildfire, I find myself worrying this year about flooding.
In the last two weeks here in Auburn, I've measured more than 11 inches of rain. Our total for the water year (which started October 1) is more than 23 inches - more than we measured in all of 2020-21! And if the 7-day forecast is correct, we'll measure another 6 inches by next Tuesday. In other words, we're wet and going to get wetter!
Over the last two fire seasons, we've implemented a Livestock Pass Program here in our foothill counties (Nevada, Placer, and Yuba). Rather than focusing on evacuating livestock during an active emergency, the program provides training for ranchers to allow access within evacuation zones to care for livestock. While our focus has been on wildfire evacuations, recent flooding in rural parts of Sacramento County reminds me that there may be other types of disasters (natural and otherwise) for which we need to prepare.
During fire season, I carry 5 gallons of water and a fire tool in my pick-up. While I've never actually had to use either of these, I feel better knowing that I have at least some capacity to deal with an emergency. But it's been so long since we've had this kind of winter weather, I've had to think about what I need to carry in my truck this winter.
Unlike the Sacramento Valley (where all of this water we're seeing in the foothills eventually winds up), our region typically doesn't face total inundation. That said, rainfall like we've experienced in the last several weeks makes small creeks run and bigger creeks rage - sometimes across the roads I use to access our sheep before and after work. And the combination of saturated soils, high winds, and drought-weakened trees can cause problems, as well - with fencelines and power lines alike. Since we use portable electro-net fencing, I spend a few extra minutes each day walking the fence to make sure nothing has blown over. This week, with more wind and rain, I put my chainsaw and shovel in my truck.
Someone asked me this week how my sheep chores change in weather like this. I jokingly answered that not much changes, other than the fact that I get wet while doing them! But that's not entirely true - I find that my grazing planning does change when we're in a wet pattern like this. Since we won't be lambing for another 6-7 weeks, I'm not too worried about making sure there's shelter from wind and rain - the ewes are pretty hardy at this stage. But I do adhere to the old shepherd's adage that the best shelter for sheep is a belly full of grass. Just like I try to keep my gas tank at least half full during fire season, I try to make sure the sheep always have enough feed to be ok if I can't get to the paddock for a day or two.
And with the rain we've had so far, we seem to have enough grass! For now, anyway!
- Author: Dr. Anthony Fulford
What is subsoil?
There are several layers (also known as “horizons” to soil scientists) that can be found when we dig deeper and deeper down into the soil. We can imagine all the individual layers of a soil stacked one on top of the other like a layer cake, this is called the soil profile. The surface soil is the uppermost layer of the soil profile, and the one we are most familiar with, because this is where most of the action takes place. Soil mixing with tillage, compost and fertilizer application, irrigation, plant root growth, and animal activity (including microbes) are mainly concentrated within the soil's surface layer. Additionally, decomposition of plant and leaf litter occurs most rapidly in the surface soil, this eventually leads to the formation of new soil organic matter. In comparison, the subsurface soil, or subsoil, is composed of one or more soil layers that lie below the influence of surface soil activities. There is not a consistent depth at which every surface soil layer changes into the subsoil layer(s), rather the subsoil occurs at a different depth from place to place depending on numerous factors, including some of the factors mentioned previously. This is the reason why it is difficult to determine where the subsoil layer begins in the soil profile.
What does subsoil contain?
What does subsoil look like?
What is subsoil used for?
In general, the subsoil is a less suitable medium for plant growth compared to surface soil because of some of the factors mentioned previously. There are properties of subsoil however that make it suitable for other uses such as a source of “fill soil” for “cut-and-fill” construction operations, as a source of clay for building materials, and as an absorption layer for on-site wastewater disposal.
What can home gardeners do to keep their subsoil in great shape year after year?
What is the substratum layer of soil? Does that layer affect gardening at all, and if so how?
What is the bedrock layer? Does that layer affect gardening at all, and if so how?
Bedrock is the bottom layer of the soil profile layer cake. The bedrock layer consists of solid rock that has not yet been exposed to the chemical, physical, and biological processes of the surface soil and subsoil. In some places, bedrock is the foundation from which the overlying soil layers developed, while in other places, the bedrock layer may have become “buried” by windblown sand or sediment. Bedrock does not directly influence plant growth, but it can determine the type of clay minerals found in different layers of the soil profile.
Dr. Anthony Fulford is the Area Nutrient Management and Soil Quality Advisor for Stanislaus, Merced, and San Joaquin Counties.
/h3>/h3>/h3>/h3>/h3>/h3>/h3>- Author: Ben Faber
In 2018 the Ojai Valley Land Conservancy (OVLC) accepted a grant from the Resources Legacy Fund on behalf of Watershed Coalition of Ventura County (WCVC) for a study of projected climate changes in Ventura County. OVLC contracted with Drs. Nina Oakley and Ben Hatchett, climatologists with the Desert Research Institute (DRI), to evaluate historic climate variability and projected changes in Ventura County. This information is needed to “paint a picture” of future climate in the watersheds of Ventura County (Ventura River, Santa Clara River, and Calleguas Creek) to support and inform climate change-related decision-making. This study provides important information for the amendment to WCVC's Integrated Regional Water Management (IRWM) Plan
You can find a copy of the report on the DRI website at: https://wrcc.dri.edu/Climate/reports.php.
To view presentations and other information from the two WCVC Climate workshops conducted with Drs. Oakley and Hatchett in October of 2018, and April of this year please visit: http://wcvc.ventura.org/documents/climate_change.htm
Some of those most interesting findings for me, are the historical data. For example, data for the years 1896 – 2018, show a tendency toward increasing maximum temperatures over the period, especially the last 10 years (Fig 1.2). But most interesting, is the increasing minimum temperatures (Fig 1.3) as compared to the maximum temperatures. Winter where is thy sting? The 2018-19 winter was the coldest in my memory, with the heater on full time at night, but there was no general frost damage this year. I can remember 1990 and 2007.
Precipitation in the South Coast region exhibits high interannual variability over the period examined. No notable long-term trends are observed (Fig. 1.4). Since approximately 2000, the 11-year running mean decreases, associated in part with the 2012–2019 drought. It is unclear whether this trend will continue in subsequent years.
There's a lot more information in the report. READ On.
But something to keep in mind, is that we had a terrible heat wave last July, and it could easily happen again. Growers who had their trees well hydrated before the heat arrived, sustain less or no damage to the trees and much less fruit drop. Trees that were irrigated on the day it started to get hot, never had a chance to catch up with the heat. Once the atmosphere starts sucking the tree dry, water movement through the soil, roots and trunk cant keep up with the demand. Weather forecasting is pretty accurate 3 days out, and if heat is forecast, get those trees in shape. You can run water to reduce the temperature and raise the humidity in the orchard to reduce transpirational demand which helps some.
Something we learned last year. What we saw and what to expect:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27676
Map of elevational changes in Ventura County and how
- Author: Lynn Wunderlich
The "hydrological year", also called a "water year", is a term hydrologists and water resource managers use to describe the period from Oct. 1 of a given year to Sept.30 of the following year. Thus, the hydro year is meant to include fall rainfall with dormant season rains that may impact the soil water holding capacity and total rainfall for crops emerging the following spring.
The stations are located across El Dorado, Amador, and Calaveras counties and give us a good picture of the rainfall totals across the region. And the winner is....the Lava Cap station located in Camino has recorded the highest rainfall amount to date, 54.04 inches; closely followed by our newest addition to the network, the West Point station at 53.78 inches!
- Author: Ben Faber
Thanks for the rains that leach the soils of accumulated salts and bring on new fresh growth. Or maybe not. When we apply irrigation water with salts which with few exceptions we do in irrigated agriculture, salts accumulate in the soil. They accumulate in a certain pattern depending on the type of irrigation and soil type. There's a strong tendency for drip and microsprinklers to form a pattern of salt accumulation near the margins of the wetted patterns. This pattern is stronger with drip because the source point is always pushing a front outward from the emission point. This pattern occurs with microsprinklers, as well, although not as strongly. These patterns continue to form and accumulate as long as there is no rainfall to evenly push the salt down below the root zone. The longer the period of no rain, the larger the salt concentration at the margin.
So the way water moves is generally down. It moves in a wetting front drawn by gravity. It moves laterally too, because of the attraction water has for the soil particles. It will move laterally more in a clay soil than in a sandy soil because there are more particles in a clay soil than a sand (actually more surfaces that hold water). It also carries salt with it. Wherever the water moves, the salt moves. The more rain, the more salt is moved down. The more rain, the deeper the salt is pushed.
The problem with rain, is that if there is not enough, the salt tends to move laterally. In this wet soil solution, the salt is moving from where it is concentrated, to where there is a lower one. And if there isn't enough rain to move that salt down, it just moves back along the salt gradient, back to where the water first came from…….towards the roots. And that salt may be at such a high concentration that it can cause plant damage.
We talk about effective rainfall. This is usually about a quarter of an inch of rain. This is the amount of water to do more than just wet the dust, it's the amount to move water into the root zone. It is also moving salts into the root zone which can be a real problem. A good rain will do more than wet the dust, it will also move the salts out of harm's way in the root zone. The amount of rain necessary to do this going to depend on the salt accumulated and the soil texture. The more salt, the more rain needed. The finer the texture, the more rain. So there is no good cookbook, other than you need enough. And the first rains of the year, watch out. This is often when the highest salt accumulation and the most irregular the rains. Small amounts that can move salt into the root zone.
If there is not enough rain……………The solution !!!!!!!! Run the water to make sure there is enough to move that salt down. Crazy, but a few months ago we had just this situation. It was one of the last rains in the winter and it was not enough to move salts down, and within a week many avocados showed leaf damage. It was sad since we had all been wanting rain, and we wanted a good drenching.
So why am I bringing this up now? Well, the other night I woke up to rain, glorious rain. I enjoyed listening to it and then it stopped. I thought O NO, it's not enough. There are going to be problems. Well luckily most places didn't get and where it did, it was a dust settler. But it made me aware that with the first rains we might see this fall, growers should be on their guard.
Get ready to irrigate with the first rains if they are insufficient for adequate leaching.