Precision Plant Systems Blog

The following is a quick summary of why should growers and crop consultants measure pH in their soils during the course of the year.

Soil pH is an important consideration for farmers and gardeners for several reasons:

• Many plants and soil life forms have a preference for either alkaline or acidic conditions, affecting the choice of crop or plant that can be grown without intervention to adjust the pH
• Diseases affecting plants also tend to thrive in soil with a particular pH range
• The pH can affect the availability of nutrients in the soil.

Factors affecting soil pH

The pH value of a soil is influenced by the kinds of parent materials from which the soil was formed. Soils developed from basic rocks generally have higher pH values than those formed from acid rocks.

Rainfall also affects soil pH Water passing through the soil leaches basic nutrients such as calcium and magnesium from the soil. They are replaced by acidic elements such as aluminum and iron. For this reason, soils formed under high rainfall conditions are more acidic than those formed under arid (dry) conditions.

Soil life and pH

A pH level of around 6.3-6.8 is also the optimum range preferred by most soil bacteria, although fungi, moulds, and anaerobic bacteria have a broader tolerance and tend to multiply at lower pH values. Therefore, more acidic soils tend to be susceptible to souring and putrefaction, rather than undergoing the sweet decay processes associated with the decay of organic matter, which immeasurably benefit the soil. These processes also prefer near-neutral conditions.

pH and plant diseases

Many plant diseases are caused or exacerbated by extremes of pH, sometimes because this makes essential nutrients unavailable to crops or because the soil itself is unhealthy (see above). For example, chlorosis of leaf vegetables and potato scab occur in overly alkaline conditions, and acidic soils can cause clubroot in brassicas.

Measuring Soil pH

Simple mistakes when measuring soil pH will leave you with results that can ruin your farming operation.  Don't get caught in not following simple process rules.

Do not test cold soil. Cold inactivates bacteria, resulting in a false reading. Wait until soil temperature (not air temperature) has been above 60 degrees for at least two weeks, then test.

When measuring soil pH, don't neglect the subsoil, unless you are the lucky owner of a four-foot-deep black prairie loam. We forget that if surface soil is only six to ten inches deep, most roots of many crops will grow through that upper layer and get the majority of their nourishment from the subsoil.

Precision Plant Systems offers pH testers with stainless steel probes that makes the measurement process much easier to manage and record.  http://www.cropiq.com/products/cropiq-field-instruments.aspx

California quarantine to combat European grapevine moth (EGVM) detection

In response to the recent detection of the European grapevine moth (EGVM) in Napa County, the California Department of Food and Agriculture (CDFA) has established a quarantine of 162 square miles including portions of Napa, Sonoma and Solano counties.

The detection of an EGVM larva in a trap in the Oakville area on September 15, 2009 was the first detection of this pest in the United States. Confirmation of that detection led to increased trapping and surveys that have since detected the pest at several sites, generally contained in two pockets of infestation: one on the eastern side of the City of Napa and the other between Oakville, Rutherford and St. Helena.  Maps of the two quarantine zones and additional information are available at www.cdfa.ca.gov/PHPPS/PE/InteriorExclusion/egvm_quarantine.html.

"Grapes are our state's top crop," said CDFA Secretary A.G. Kawamura.  "This quarantine will help us ensure that the infestation doesn't have an opportunity to spread.  I fully understand that quarantines impact both the public and our growers. It is important and necessary to protect our food supply and the larger environment from these invasive pests, so the entire community's cooperation is essential and appreciated."

EVGM, or Lobesia botrana, is found in southern Asia, Europe, North Africa, Anatolia, the Caucasus and in South America. The pest primarily damages grapes, but has also been known to feed on other crops and plants.

Inspectors are working with growers, nurseries, landscapers and others who work with plants and fruit to guard against spread of the pest by regulating the harvest, shipping and handling of affected crops and plants.  CDFA and local officials will plan grower meetings to make sure the agricultural community understands the quarantine regulations.
Residents of the quarantined area are asked to review the list of host plants/fruits (below) and to not remove them from their property; the produce may, however, be harvested and consumed on site.
 
Scientific Name                        Common Name
Actinidia chinensis                   Kiwi fruit or Chinese Gooseberry
Berberis vulgaris                      European Barberry
Clematis vitalba                       Old-Man's-Beard or Traveller's Joy
Daphne gnidium                       Spurge Flax
Dianthus spp.                          Carnation
Diospyros kaki                         Persimmon
Galium mollugo                        False Baby's Breath or White Bedstraw
Hypericum calycinum               St. John's Wort or Aaron's Beard
Ligustrum vulgare                    European Privet
Olea europaea                         Olive
Prunus spp.                             Stone Fruit (e.g. apricot, cherry, plum)
Punica granatum                     Pomegranate
Rhus glabra                             Smooth Sumac
Ribes spp.                               Currant, Gooseberry
Rosmarinus officinalis              Rosemary
Rubus spp.                              Blackberry, Dewberry
Silene vulgaris                         Bladder Campion
Trifolium pratense                   Red Clover
Urginea maritime                    Sea squill
Vitis spp.                                 Grape
Ziziphus jujuba                       Jujube
 
The EVGM larvae, not the adult moths, are responsible for the damage to grapes. Larvae that emerge early in the spring feed on grape bud clusters or flowers and spin webbing around them before pupating inside the web or under a rolled leaf.  If heavy flower damage occurs during this first generation, the affected flowers will fail to develop and yield will be reduced.  Second-generation larvae enter the grapes to feed before pupating inside the grape.  Larvae of the third generation - the most damaging - feed on multiple ripening grapes and expose them to further damage from fungal development and rot.
 
In the Oakville area of Napa County, where the original infestation was detected last fall, one grape grower lost his entire harvest.
 
CDFA, working closely with the US Department of Agriculture and county agricultural commissioners, has begun an intensive statewide trapping effort to determine whether the moth has infested any other areas of the state.  In addition to traps already deployed in Napa and the immediate area, an array of traps is being deployed beginning in the warmer, southern region of the state, and progressing northward as the spring weather arrives, grapevines come out of dormancy, and the moths begin to emerge if they are present.


Source: imperialvalleynews.com

Great article in the Portland Oregonian on March 13th that helps explain the critical importance of scouting your fields and the focus on integrated pest management for the control of Asian fruit fly, the  the spotted wing Drosophila. CropIQ, the premier crop management system will be deployed this growing season.