May 9, 2013
Wind speed: 16/27 mph
We were able to fit in a field trip before school ended this spring to the Jersey Island site. John Sierra and Cheryl Ochinero were the teachers involved in bringing out the students from the high school. Emille Kirk, Nicole Stern and Rongzhong Le came from UC Davis and Tetra Tech, UC Davis to help with the testing.
A week or so before the event I ordered all kinds of testing supplies from LaMotte Science Services so the student could do hands on testing.
Thanks to Nicole Stern from Tetra Tech, UC Davis in helping us order all the sets needed for the experiments.
Yumi Henneberry wasn't able to join us as she left on an extended trip. Hopefully she will be back toward the end of this year's planting season to see how far we've come on the project.
The students began by taking a tour up the hill to the levee and looked out to the San Joaquin River and then turned to look down onto the site where our rice fields are. This is a first hand look at subsidence and part of what our study is all about. I was also able to show them pictures taken in the 1920-30s, photographed from the same spot we were standing on. Instead of a hill that we now saw, there were level homes and at one time a hotel on the shoreline of the island.
Nicole Stern started the testing events by showing students how to test water samples. During the testing we were testing sulfates, nitrate/nitrogen, phosphates and ammonia-nitrogen.
Why do we test for sulfates in the soil?
Acid sulfate soils are naturally occurring soils, sediments or organic substrates (e.g. peat) that are formed under waterlogged conditions. These soils contain iron sulfide minerals (predominantly as the mineral pyrite) or their oxidation products. In an undisturbed state below the water table, acid sulfate soils are benign. However if the soils are drained, excavated or exposed to air by a lowering of the water table, the sulfides react with oxygen to form sulfuric acid.
Why are we testing for nitrate nitrogen?
Nitrogen in the soil is the most important element for plant development. It is required in large amounts and must be added to the soil to avoid a deficiency. Nitrogen is a major part of chlorophyll and the green color of plants. It is responsible for lush, vigorous growth and the development of a dense, attractive lawn. Although nitrogen is the most abundant element in our atmosphere, plants can't use it until it is naturally processed in the soil, or added as fertilizer.
The availability of nitrogen is often used to calculate the cost-to-benefit ratio of using fertilizer in a given area.
When nitrogen inputs to the soil system exceed crop needs, there is a possibility that excessive amounts of nitrate (NO 3 - ) may enter either ground or surface water.
Managing nitrogen inputs to achieve a balance between profitable crop production and environmentally tolerable levels of nitrates in water supplies should be every grower's goal.
Why do we test phosphate in water?
Phosphate’s role in promoting plant growth actually makes it a dangerous pollutant when dumped in excessive quantities into aquatic ecosystems. Plants have difficulty obtaining phosphates. In fact, plants have so much difficulty that the chemical is a limiting nutrient.
The rate at which plants can grow and reproduce is limited by the amount of usable phosphate in the soil or water. When humans add extra phosphorous to water, they create a condition called eutrophication that can wipe out aquatic ecosystems. Eutrophication is characterized by a rapid growth in the plant population (an algal bloom).
With more living plants comes more dead plants needing decomposition. The bacteria that decompose the dead plants use oxygen, and eventually burn up so much that not enough remains to support fish, insects, mussels, and other animals, leading to a massive die-off.
Why do we test for ammonia-nitrogen?
Ammonia-nitrogen is an inorganic, dissolved form of nitrogen that can be found in water and is the preferred form for algae and plant growth. Ammonia is the most reduced form of nitrogen and is found in water where dissolved oxygen is lacking. When dissolved oxygen is readily available, bacteria quickly oxidize ammonia to nitrate through a process known as nitrification.
Other types of bacteria produce ammonia as they decompose dead plant and animal matter. Depending on temperature and pH (a measurement of acidity), high levels of ammonia can be toxic to aquatic life. High pH and warmer temperatures increase the toxicity of a given ammonia concentration. High ammonia concentrations can stimulate excessive aquatic production and indicate pollution.
Important sources of ammonia to rivers can include: fertilizers, human and animal wastes, and byproducts from industrial manufacturing processes. Techniques to prevent high ammonia concentrations involve filtration of runoff water especially from barnyards and other areas where animals may be kept in larger numbers, proper septic system maintenance, and not over-fertilizing yards or fields.
Next Rongzhong Le spoke with the students about measuring carbon emission (greenhouse gas) within the rice field. The group took a pre-rice test to measure future emission tests from.
With the rice the peat soil, a natural carbon emitter into the atmosphere, soaked in water for the rice planting, the carbon emission will be considerable less.
Soil tests are completed to make sure that the rice isn't releasing substances into the soil that we don't want to be added. Whenever a change is made to the environment are can be unintended consequences. In the case of rise nitrates can change in the soil or methane gas can be added in the air. These will all be measured by the students to make sure if those changes are made they are within acceptable numbers.