Out of 3,600 samples of 145 fresh fruits and vegetables tested in California in 2015, just 43 had pesticide residue over legal limits, and 113 contained residue of a pesticide not approved for that commodity. Pesticide residue limits are set based on legal use of the product and violations are generally not health concerns.
The tests were conducted by the California Department of Pesticide Regulation, which for three decades has been conducting one of the most comprehensive pesticide monitoring programs in the country.
Other highlights from the just-released results:
As in recent years, the majority of these samples had residues at less, usually much less, than 10% of the tolerance level.
The department also tested 170 fruits or vegetables labeled organic and 85.3% had no detectable pesticide residue, 11.8% had residues acceptable under organic regulations, 2.4% had residues acceptable in conventionally grown produce but not organic, and 0.6% had unacceptable residues.
Certain products from China and Mexico had the highest level of illegal pesticide residues detected.
In a recent meeting the topic of where to go for irrigation information came up. Well there's no substitute for attending a class in irrigation, such as offered at Cal Poly SLO (http://www.itrc.org/classes/iseclass.htm ,
but here's some written sources to get you started thinking.
- Author: Jim Wolpert - UC Davis
Soil Moisture Sensors
Jim Wolpert, University of California, Davis
Soil Moisture Content
The quantity of water in soil is called the soil moisture content. After rainfall or irrigation, some water drains from the soil by the force of gravity. The remaining water is held in the soil by a complex force known as surface tension and varies depending on the amount of sand, silt, and clay. Sands, with larger particles and smaller total surface area, will hold less water than clays, which have much smaller particles and larger total surface area. The drier the soil, the greater the surface tension, and the more energy it will take for a plant to extract water.
Vineyard managers often measure soil water content as a guide to determine their irrigation timings and amounts. There are several methods for monitoring soil water content. Correlating these methods with actual inches of moisture per foot of soil is very complicated (see Recommended Links) but at the very least can help a grower to identify patterns of water use, depth of irrigation, and soil water content trends over time.
A tensiometer, as its name implies, is a device for measuring soil moisture tension. The design is a simple tube with a porous cup at the lower end and a vacuum gauge on top. The tube is filled with water, sealed airtight, and placed in soil. As soil dries, water is pulled from the porous cup into the soil, creating a vacuum and causing the gauge to move. As soil continues to dry, more water is pulled out and the suction increases. As soil re-wets after a rain or irrigation, water moves back into the cup and the suction decreases. Installing tensiometers in soil requires attention to detail to obtain accurate readings (see Recommended Links for installation downloads).
Tensiometers are usually placed as a pair with the shorter tube positioned in the middle of the rooting zone (e.g., 18 inches deep) and a longer tube positioned near the bottom of the rooting zone (3 to 4 feet deep). Growers can use the difference between the two tubes to monitor water usage and determine the effective depth of irrigation. At least two stations (two tubes per station) are recommended per field, or more depending on soil variability.
Tensiometers have the advantage of being inexpensive, and easy to install, maintain, and read. They are better in fine-textured soils where good contact can be made between the porous cup and the soil. They do not work well in coarse sands where good contact may not be possible. Because the gauges are aboveground, the units are prone to damage by vineyard equipment.
Electrical Resistance Blocks
Electrical resistance blocks are also known as gypsum blocks or soil moisture blocks. They are simple devices with two electrodes embedded in a block of gypsum or other similar material. When blocks are buried in soil, water moves into or out of the block, depending on the moisture of the soil, changing the resistance between the two electrodes. Like tensiometers, gypsum blocks are cheap and easy to install. They are usually installed in at least two stations per field, at two depths, and must be installed correctly to provide accurate readings. Some block designs perform better under wet soil conditions and some correct for soil temperature. The meter used to read the blocks can be moved from field to field, but is specific to the block design (i.e., it is not a simple ohm meter). The wires aboveground are much less prone to damage by equipment compared to tensiometers.
A neutron probe uses a radioactive source for measuring soil moisture. A tube, usually made of PVC or aluminum, is installed in soil to a depth of interest and the radioactive probe is lowered into soil to measure soil moisture at as many depths as desired. The probe emits fast neutrons that are slowed by water in the soil in a way that can be calibrated to the soil water content. The probe has a significant advantage, especially for perennial crops, because access tubes are easy to install and relatively permanent. Another advantage is the reading accounts for a spherical area about 10 inches in diameter, much greater than other methods. The major limitation to this method is the probe itself; it is expensive and the presence of a radioactive source triggers requirements for operators to be trained and licensed in handling, storage, and use. In some production regions, service providers are available, usually at a fixed cost per access tube for a growing season.
Di-electric sensors measure the di-electric constant of soil, a characteristic that changes with changing soil moisture. A common method is called time domain reflectometry, or TDR. The theory behind how this method works is too complicated to be discussed here. The advantage of these types of systems is that they are designed to be left in place and provide continuous readings of soil moisture. The disadvantages are that the units are expensive and read soil moisture only a very small distance from the unit.
All measures of soil moisture suffer from the same limitation — the value of the information is dependent on the extent to which the soil where the measurements are taken reflects the rest of the field. Where soil variability is high, growers must exercise caution in relying too heavily on relatively few measurements.
Irrigation of Winegrapes, University of California
Irrigation Basics for Eastern Washington Vineyards, Washington State University
Reviewed by Ed Hellman, Texas AgriLife Extension and Eric Stafne, Mississippi State University
SACRAMENTO — The California Department of Food and Agriculture (CDFA) has awarded $215,670 for five projects that will promote and administer agricultural education and leadership programs for students, teachers and youth under the 2014 California Special Interest License Plate (CalAgPlate) grant program. The CalAgPlate program is funded with proceeds generated through the sale of specialized, agriculture-themed license plates through the California Department of Motor Vehicles (DMV). CalAgPlates were first made available in 2012, and over 19,000 plates have been sold to date.
Projects funded as part of the program's inaugural year include a farm-to-school program linking students to local farmers; an agricultural industry tour that will increase student awareness of career opportunities within farming and agribusiness; a hands-on seminar for teachers to help broaden curricular exposure of students to agriculture; a program to educate elementary school students on the role of agriculture in our daily lives; and a program that provides opportunities for high school students to engage in agricultural education, leadership development and career training.
“Agricultural education is fundamental to the appreciation of how agriculture and food production touches every Californian,” said Secretary Karen Ross. “The projects being funded are great examples of how to connect students and consumers to agriculture and the many career possibilities within the food and agricultural system.”
The CalAgPlate program is made possible through the hard work of many people and organizations that helped to promote the sale of this specialized license plate. Special thanks are given to the Future Farmers of America (FFA), the California Agricultural Leadership Program (Class XXXI), and to the many student volunteers who represent California agriculture.
The 2014 CalAgPlate project abstracts are available online at www.cdfa.ca.gov/calagplate.
Help to support agricultural education and the CalAgPlate program by purchasing a special interest license plate at your local DMV office or online today.
—California Department of Agriculture
Here's a wide range of information on drought resources from ATTRA, the National Sustainable Agriculture Information Service - https://attra.ncat.org/attra-pub/summaries/summary.php?pub=458