- Author: Mark Bolda
Great article here by Dr. Robert Mikkelson from the International Plant Nutrition Institute concerning the why and how of liming a soil which is acidic.
Here's the short of it:
Several factors contribute to the acidity of a soil, one being the geologic composition of the base material, another being lots of rain which leaches out calcium and magnesium. Another contributing factor to soil acidity in agricultural soils is the continual use of nitrogen fertilizers, especially in the same spot over a longer period of time. Both urea and ammonium, when converted to nitrate by soil micro-organisms, release hydrogen ions, the higher the concentration of which raise the acidity of the soil.
A common grower solution to acidic soils is the addition of ground limestone. However, while limestone neutralizes acidity, adds calcium and enhances the solubility of phosphate (and consequently availability of phosphorous to the the plant) does not dissolve well at all at pH's above 6.5 (common for soils of the Central Coast) and one would be hard put to realize the aforementioned benefits at this pH. So if one needs to add calcium to a soil with a pH above 6.5, the better choice would be gypsum, which while it also does not dissolve well in a neutral pH soil, does supply more soluble calcium.
- Author: Mark Bolda
Had the following paper forwarded to me by Tom Gordon from UCD for a further understanding from the literature on what it takes for an organic soil amendment to be suppressive:
In summary, this paper:
1- Uses an immense data set (2423 studies) drawn from 252 papers to explore the efficacy of using organic soil amendments (compost, peat, organic wastes, animal and green manures) in inducing soilborne diseases suppression.
2- Looks at the influence of the state of decomposition of the organic matter. Decomposition either increases or decreases suppressiveness, or in other cases (especially compost) shows more complex responses (see Fig 4 in the paper).
3- States that generally speaking when a specific organic amendment was suppressive to one pathogen it was ineffective or even CONDUCIVE (emphasis mine) to other pathogens (important consideration in our emerging Central Coast soil pathogen complex of Verticillium – Fusarium – Phytophthora – Macrophomina).
4- Finds that chemical and physical aspects of an organic amendment are not as strong predictors of suppressiveness as are enzymatic and microbiological aspects. The paper concludes then that, while certain parameters such as FDA activity, substrate respiration, microbial biomass, total culturable bacteria, fluorescent pseudomonads and populations of the fungus Trichoderma are all useful for predicting suppressiveness of organic matter, no one variable can be considered in isolation to be a reliable and consistent predictor of soil suppressiveness. An integration of methods is therefore suggested.
Read the paper, it's well worth the time you put into it.
Bonanomi et al. Identifying the Characteristics of Organic Soil Amendments that Suppress Soilborne Diseases.
- Author: Mark Bolda
I have had a lot of requests for posting the talk I gave last week Thursday at the North American Strawberry Grower's Association meeting in Ventura. Great meeting by the way, totally a who's who of the industry, with top flight scientists from public institutions and the private sector sharing information on a giant range of topics in strawberries.
- Author: Mark Bolda
So that growers, PCA's and other agricultural people might have a bit more access to UC and UCCE scientists, entomology Advisor Shimat Joseph is sponsoring a breakfast meeting at my auditorium at 1432 Freedom Blvd in Watsonville on March 10. We have both Plant Pathology Farm Advisor Steven Koike speaking about diseases, followed by our special guest entomologist and IPM Advisor Pete Goodell out of the Kearney research station in the Central Valley (he has a enormous amount of experience with lygus).
Point is to have a good discussion between people involved in strawberry production and UC scientists, along with having a great breakfast of course. Come by if you have the time - starts at 630 am and will be wrapped up by 8.
- Author: Steven T. Koike
- Author: Mark Bolda
In strawberry and other crop field soils, growers and PCAs may occasionally see small “worms” wriggling around and near the roots and crowns of plants and sometimes around ungerminated seeds. Concern is sometimes expressed that these worms might be plant parasitic nematodes that could damage strawberry or other crops. There is good news here: if one is able to see these worms without using a hand lens or other magnifier, these worms are not parasitic to plants.
Worm samples submitted to our UCCE offices over the years have all turned out to be a type of soil and water organism called an oligochaete worm (which is in the taxonomic group Annelida). These small worms are large enough to see without magnification (Fig. 1), are whitish to translucent in appearance, and move vigorously when disturbed. Examination with a microscope is needed to confirm the identification; the worm body is made up of segments (Fig. 2), with each segment bearing small external spines or seta (called chaeta) (Figs. 3 and 4). Oligochaetes are much larger than the parasitic nematodes that attack plants (Fig. 5).
Closely related to earthworms, these small oligochaetes are found in wet areas such as puddles of standing water and moist soils. Like earthworms, they feed by ingesting sediment and soil particles and digesting nutrients from organic matter and bacteria. Oligochaetes may therefore be found in large numbers in soil around organic substrates, rotting plant materials, and other food sources.
