Thank you. My question doesn't relate to avoiding salt buildup in the soil, though. I am asking about ways to facilitate gas exchange at the root zone in soils that lack proper aeration for this to happen passively. Since the act of watering displaces soil gasses, pushing out what is already there and drawing in fresh oxygen behind the water, I was curious if watering on a more frequent schedule than necessary would help mitigate the lack of passive gas exchange. Of course, you would have to manually drain the PWT each watering. There seem to be two benefits of a highly aerated container soil, from what I have read and understood so far, and they are closely related: 1. Reduces or eliminates areas that allow no gas exchange (the dreaded PWT - waterlogged areas with insufficient oxygen available for roots to respire) 2. Reduces or eliminates areas that allow insufficient gas exchange (compacted areas where the available oxygen is quickly used up and the other gasses, byproducts of root respiration, end up trapped instead of being able to diffuse out to allow new oxygen in). Now, 1. can be addressed, in part or completely, by the methods described in this thread. Ways to manually drain the soil's PWT when the soil is too dense for it to drain away passively. Are there similar strategies for dealing with 2. manually when a soil is too dense for reasonable gas exchange to occur passively? Will a more frequent watering schedule act as a manual gas exchange?

The latest is of the journal Science is devoted to hydrogen as a fuel and to other aspects of the energy equation. I've appended the titles; for access to full articles, you must be a subscriber. In the meantime, I'll post the series' editors introduction. ------------------------------------------------------------ Not So Simple Robert Coontz and Brooks Hanson Seen up close, hydrogen looks like a recipe for success. Small and simple--one proton and one electron in its most common atomic form--hydrogen was the first element to assemble as the universe cooled off after the big bang, and it is still the most widespread. It accounts for 90% of the atoms in the universe, two-thirds of the atoms in water, and a fair proportion of the atoms in living organisms and their geologic legacy, fossil fuels. To scientists and engineers, those atoms offer both promise and frustration. Highly electronegative, they are eager to bond, and they release energy generously when they do. That makes them potentially useful, if you can find them. On Earth, however, unattached hydrogen is vanishingly rare. It must be liberated by breaking chemical bonds, which requires energy. Once released, the atoms pair up into two-atom molecules, whose dumbbell-shaped electron clouds are so well balanced that fleeting charge differences can pull them into a liquid only at a frigid -252.89 Celsius, 20 kelvin above absolute zero. The result, at normal human-scale temperatures, is an invisible gas: light, jittery, and slippery; hard to store, transport, liquefy, and handle safely; and capable of releasing only as much energy as human beings first pump into it. All of which indicates that using hydrogen as a common currency for an energy economy will be far from simple. The papers and News stories in this special section explore some of its many facets. Consider hydrogen's green image. As a manufactured product, hydrogen is only as clean or dirty as the processes that produce it in the first place. Turner (p. 972) describes various options for large-scale hydrogen production in his Viewpoint. Furthermore, as News writer Service points out (p. 958), production is just one of many technologies that must mature and mesh for hydrogen power to become a reality, a fact that leads many experts to urge policymakers to cast as wide a net as possible. In some places, the transition to hydrogen may be relatively straightforward. For her News story (p. 966), Vogel visited Iceland, whose abundant natural energy resources have given it a clear head start. Elsewhere, though, various technological detours and bridges may lie ahead. The Viewpoint by Demirdöven and Deutch (p. 974) and Cho's News story (p. 964) describe different intermediate technologies that may shape the next generation of automobiles. Meanwhile, the fires of the fossil fuel-based "carbon economy" seem sure to burn intensely for at least another half-century or so [see the Editorial by Kennedy (p. 917)]. Service's News story on carbon sequestration (p. 962) and Pacala and Socolow's Review (p. 968) explore strategies--including using hydrogen--for mitigating their effects. Two generations down the line, the world may end up with a hydrogen economy completely different from the one it expected to develop. Perhaps the intermediate steps on the road to hydrogen will turn out to be the destination. The title we chose for this issue--Toward a Hydrogen Economy-- reflects that basic uncertainty and the complexity of what is sure to be a long, scientifically engaging journey. ============================================================ SPECIAL ISSUE: Toward a Hydrogen Economy --------------------------------------------------------------------------- Toward a Hydrogen Economy: Introduction to special issue -------------------- Not So Simple Robert Coontz and Brooks Hanson http://www.sciencemag.org/cgi/content/summary/305/5686/957?etoc p. 957 Toward a Hydrogen Economy: News -------------------- The Hydrogen Backlash Robert F. Service http://www.sciencemag.org/cgi/content/summary/305/5686/958?etoc p. 958 The Carbon Conundrum Robert F. Service http://www.sciencemag.org/cgi/content/summary/305/5686/962?etoc p. 962 Choosing a CO2 Separation Technology Robert F. Service http://www.sciencemag.org/cgi/content/summary/305/5686/963?etoc p. 963 Fire and ICE: Revving Up for H2 Adrian Cho http://www.sciencemag.org/cgi/content/summary/305/5686/964?etoc p. 964 Will the Future Dawn in the North? Gretchen Vogel http://www.sciencemag.org/cgi/content/summary/305/5686/966?etoc p. 966 Can the Developing World Skip Petroleum? Gretchen Vogel http://www.sciencemag.org/cgi/content/summary/305/5686/967?etoc p. 967 Toward a Hydrogen Economy: Viewpoint -------------------- Sustainable Hydrogen Production John A. Turner http://www.sciencemag.org/cgi/content/abstract/305/5686/972?etoc p. 972 Hybrid Cars Now, Fuel Cell Cars Later Nurettin Demirdoven and John Deutch http://www.sciencemag.org/cgi/content/abstract/305/5686/974?etoc p. 974 Toward a Hydrogen Economy: Review -------------------- Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies S. Pacala and R. Socolow http://www.sciencemag.org/cgi/content/abstract/305/5686/968?etoc p. 968 ---------------------------------------------------------------------------

Hi Timgren Yes there are still real mechanics, although we think of ourselves as Automotive Technicians these days. As has been said by others, you need to find a good shop, with a strong diagnostic technician, and then stick with them even if they don't nail this the first time. However, after what I write here, if I don't skip anything I should be able to give them all the ammo they need to get this one. One of the things that I have preached for the last 5 odd years that I have posted here is for people to test, and not just throw parts at someones car problem "because that is what was wrong with their neighbors, or relative, or whoevers car" when it was doing the same thing. Todays cars simply have so many ways to produce the same symptoms that nothing but solid diagnostic routines will provide accurate answers. Sadly, the industry still tries to compete between shops by price, and consumers reward this by trying to go to the cheapest place, and hopefully for them the cheapest fix first. Thats why you have had plugs thrown in, filters, a fuel pump ect. Most of the time the symptoms you describe can be caused by these components, but not always. One of the most telling parts though was the convertor replacement. That is something that has two possible causes for the failure, either a missfire was occuring and or the convertor overworking, or quite commonly insulation between the double walled pipe in front of the convertor is coming out of place and blocking the convertor. Without knowing first hand, I'd have to rely on seeing your truck to know, but I suspect you have more than one convertor. One of the things that need to be done is a road test with a good scan tool, (GM's Tech II) not some $300.00 code reader and a snapshot of scan data saved to be looked at to analyze the failure. Basically if the engine is losing power something is affecting either, fuel delivery, spark timing, spark strength, engine displacement, or some combination of those. Scan data has the ability to show a trained technician almost all of that except for strength of the spark. What I would do if your truck came here is first road test the truck under the conditions that display the loss of power and capture a snapshot of the scan data. When I got back to the shop I would concentrate on; mass airflow sensor readings in grams per second, MAP sensor voltage if used, engine RPM, throttle position, spark timing, knock sensor, timing retard, fuel trims, and O2 sensor voltages. One of the things that I can do back at the shop is calculate the volumetric efficiency of the engine using the MAF sensor reading at a given rpm. This would tell me right away if the engine is breathing correctly. I would compare MAF readings while the problem is occuring to TPS and MAP readings. BTW during the symptom event, I would purposely move the throttle around a bit, while keeping the truck acting up and then examine the results on the scan data. Fuel trims and O2 sensor voltages would tell me if we are dealing with a fuel pressure, fuel volume problem. Knock sensor, spark timing, and spark retard could help me identify everything from simply a bad knock sensor, to mechanical engine trouble, to even something loose on the truck rattling and making the knock sensor send a signal that the computer see's as the engine pinging. Lastly while back in the shop, I would go back over secondary ignition and ensure strength of spark, and other normal issues. Off hand I expect you have an individual coil for each plug. That pretty much in itself rules out a number of potential problems that could occur with other designs that could cause your symptoms. This testing that I have outlined would take very little time and would either have me already knowing what is wrong, or it would have me narrowing the investigation to only a few points having ruled out a large portion of the operating system. One thing that is mandatory is to forget anything else has been done to the truck, and test exactly as it is presented, and allow the results to lead me to the problem as it exists today. Feel free to contact me by e-mail once you have this back to a shop if they have trouble figuring it out. I will give you contact information for them and can help them analyze this via live chat on the net if they want. John G. ASE CMAT L1 BTW, thanks Akthy. Take care, we got to get together one of these days. Maybe Arts up for another party....

Your best bet in a used car will be a well-maintained American car. I don't want to get into the U.S./rest of the world "discussion" being held on other threads. I'll just say that proper maintenance has more to do with a car's trouble-free operation than where it is made. Right now, there are some decent American cars out there, but perception has not caught up with the reality, so American cars suffer more depreciation than many foreign cars. As a buyer of a used car, you can take advantage of that. Some of the cars you might want to look at include the Ford Taurus, or just anything midsize or larger from GM. I'm guessing that, since you got to the age of 16 without being a "gearhead," you mostly want a comfortable, reliable car. These will do the job. They shouldn't cost a fortune for insurance, either. Mikie is right -- even if you're paying for your own insurance, it will be cheaper to piggyback on your parents' policy than it will be for you to go solo. Ask about discounts if you get good grades in school or are willing to drive only a certain number of miles per month, etc. Finally, what else I wish I'd known about cars at your age? Having a car is a joy and a privilege -- and a responsibility. As a teenager, you have the benefit of quick reflexes and (I hope) formal training. You can be an excellent driver. But there's no substitute for experience -- especially at night in the rain and on icy roads. I knew how to steer out of a skid -- until the first time I found myself in one and narrowly missed a fence as I spun into a farmer's field. It's different when it really happens. Don't fall into the trap of thinking that you're immortal (every teenager thinks so; so did I). You're in control of almost two tons of metal and glass and plastic, so be careful. When I was 16, nobody had cell phones and we were lucky if the car had an FM radio, nevermind multi-channel stereo systems and iPod links and the like. I know teenagers are better at multi-tasking than they used to be, but you still have one primary task in a car -- driving. Don't be distracted by fiddling with the stereo or talking with friends. It's okay to concentrate on driving. Professional auto racers do. Have fun! Getting my first car was a blast. I hope you find one you really like and have many happy miles with it.