Hello. I need the certainty of professional advice. My common sense is not acceptable. My girl friend loves to grow plants. Recently she started burying discarded food in the garden near plants she wants to feed. I have tried to stop this by telling her that the food must first compost, but she insists it will compost in the ground and is good for the plants. Today I had to stop her from pouring 2 litres of old cooking oil into a 1.5 foot hole near a hydrangia and a small tree. I insist to her that cooking oil has nothing in it that the plants can not get from the air or water, carbon from CO2 and hydrogen from water and that oil is ONLY composed of carbon, hydrogen and possibly oxygen , all of which the plant can get by other means. Is she going too far? Can cooking oil be used as fertilizer? And what about burying food scraps? Is this good gardening?
All of our kitchen scraps, including meat, bones, oil, and fat is buried in the garden under at least one foot of soil. I have transplanted tomato seedlings directly on top of kitchen scraps and found that the tomatoes grew better than ever before. I've been doing this year around for over 40 years and have never had any problems, except for certain pests (mostly raccoons) digging up some of the scraps, especially fish and crab remains. However, this is easily prevented by laying old chicken wire over the dug up area, weighing it down with a few rocks or bricks around the edges. Note that all of the garden advice in books and on the Web say that you should not bury oil or some of the other kitchen scraps, but I've always ignored this advice without encountering any problem; however, we do no deep fat frying, so that the amount of oil buried is not excessive.
What about putting meat, bones, oil and fat in a secure (rat-proof) compost bin instead? There is nowhere in my garden I can dig even 8 inches down. I have a gardening friend not too far away who maintains a hot compost where he successfully decomposes everything from terrible weeds to pest carcasses. I'm not sure I would be up for that even if I could. (Garry Oak, aka Margot)
I see two main risks concerning buring left food near plants. 1. Food is often rich of sodium and this may affect negatively plants, especially in areas of naturally high sodium soils like coasts and areas with high evaporation. 2. Buring food may invite rodents like mice, voles and rats, and promote their population. High rodent concentration probably causes damages to your vegetables and fruit trees. Pouring excessive amount of oil into the ground near plants may temporarily reduce effective area of roots surface, that can intake water and minerals and participate in gas exchange. I'm not aware if roots can obtain oil directly from the ground. If they can, then probably just in a very small quantity, and the rest is practically wasted as a plant food. I don't know, how the waste oil affects soil microorganisms and worms, there may be both positive and negative effects. I think, that if you have significant flow of waste oil in your household, then the wisest thing is to use it as a fuel (if permitted).
Thank you for the replies. I hope more come in. The more the better. Yes, I have found several sites warning of burying oil. It repels water. It might coat roots leading to reduced root function. It discourages oxygenation of soil. My thoughts, 2 Litres of oil is not a small amount of oil to be putting into the ground in one spot. I wonder what organisms (anarobic bacteria) that grow in it and if they would be harmful for plants... I once made fertilizer from blood/bone meal to fertilize my cacti. Within a week or so, the watering solution became a bacterial culture ( I could smell it) and many of my cacti started to rot. I lost a couple to rot. I stopped using the solution. The rest survived.
I should have mentioned that the friend I talked about earlier who keeps a hot compost, attributes the addition of cooking oil to his success achieving high temperatures - up to 160F. "I'm feeding Thermo horse chestnuts, kitchen scraps, coffee grounds and used cooking oil but just can't get much higher than 120F. Normally Thermo throws out a sack of primo compost every 10 days but with a low-fat diet and cooler temp's it is now taking almost three weeks." That's different than pouring oil directly on the soil of course but maybe a hot compost could be an alternative for you to consider as a way to dispose of kitchen scraps.
@Garry Oak, your suggestion about a rat-proof compost bin would work if large bones and large volumes of oil are not included. I find large, solid bones years after burying them; this doesn't matter for me because they don't bother anything a foot down in the soil. Even eggshells take years to break down, but their presence also doesn't have any negative effects. I don't know what a large volume of oil would do in a compost bin because I've never tried it, but it seems risky for an ordinary bin. @Sulev, your point about sodium is valid for some soils, but in the Vancouver area salt is quickly leached out of the soil. Regarding rodents, I've only had a rat digging where I'd buried kitchen scraps once in all the years I've been doing it; and it was easily eliminated by applying a cover of chicken wire over that area for a few weeks. The buried scraps only rarely attract vermin and only for a relatively short while.
My friend is adding oil to boost the temperature of a HOT compost; up to 160F. I'll get in touch with him tomorrow to ask if he could explain his methods - he does post here on the forums sometimes. Is sodium quickly leached because of our high rainfall (like right now :) )? Based on what Linda Chalker-Scott has written, I believed it to move through the soil very slowly. I have questioned that though since a neighbour once disposed of hundreds of oyster shells under a huge arbutus tree near our property line. When I suggested that might be a problem, he assured me that he had dumped 20 pounds of salt over the shells. !!! I expected the poor tree to quickly show signs of trouble. Only now, 10+ years later is the tree ailing - but so are many other arbutus in this area - so it's hard to say for sure if the salt is to blame. Margot
Lots of plants such as rhododendrons, azaleas, balsam fir and some dogwoods that are intolerant of salt grow very well in the same areas as arbutus along the BC coast. It may be a bit of an exaggeration to describe the coast as highly saline but arbutus is definitely more tolerant of salt than average. EDIT: For what it's worth, a soil test I had done a few years ago said the sodium was 108 ppm. I've read that it should be below 4o ppm. I don't know if my reading is something to worry about or not but my plants grow well (if they get enough water).
Did you measure that? People usually don't keep so much salt in their household, at least in my country. And when caught at activity, that may likely cause harm to neighbors, people tend to exaggerate with their claims about used countermeasures.
AFAIK, Arbutus is not native in BC, but is introduced there from the Mediterranean. I am glad, that it can thrive even in your low salinity soils, but my comment was about the tree, that was supposedly poured with 20 pounds of salt near the tree. If rhododendrons, azaleas, balsam fir and these dogwoods can tolerate such salt applications, then they hardly are intolerant of salt. .
According to https://ibis.geog.ubc.ca/~epicc/reports/Vancouver-EPiCC-Tech-Report-2.pdf proximity to the coast is still a factor of elevated salinity even in the Vancouver area. I have seen several soil test lab results from this area, and most had elevated sodiun content.
Salt spray and inundation are two different things involving different levels of exposure, trees and shrubs can be just above high tide line and not demonstrating the same tolerance as if they were flooded by salt water on a recurring basis for extended periods. The latter circumstance is what applies to species classed as halophytes. That are characteristic of habitats such as salt marshes.
20 pounds of NaCl distributed over 10 m2 area and leached down to 1 m deep add average sodium amount just about 225 ppm. If to believe soil test results from @soccerdad published in the thread https://forums.botanicalgarden.ubc.ca/threads/disappointing-garden.101336/page-3 https://forums.botanicalgarden.ubc.ca/attachments/upload_2021-11-30_13-52-37-png.221187/ Then sodium concentration of 155 ppm is not unusual in the Vancouver area.
Another soil test report from the Vancouver area with high sodium result (by @Margot ): https://forums.botanicalgarden.ubc.ca/attachments/soil-test-october-2021-jpg.219516/
That is my soil test. I am surprised that the sodium number is as high as it is considering I've never put any in the soil and we don't get any direct spray from the ocean. I wonder if the fact that our rainfall is low over the course of the year would explain why it doesn't leach away more quickly. Margot aka Garry Oak
My neighbour is a completely guileless fellow - seemingly unaware that salt could be an environmental problem. Nevermind the fact that the hundreds of oyster shells he was pouring it on were illegally harvested. I'm sure he didn't have 20 pounds of salt on his kitchen shelf but it's cheap to buy at the nearby grocery store.
1. Maybe your neighbor does that instead of you? 2. Maybe your property is still in the coastal area, and is affected by salt fogs? AFAIK, distance up to 1 km from the coastline is strongly affected (depending on dominant wind directions).
Thank you for your suggestions, Sulev. My neighbour does not garden; in fact, only 'home' a few weeks a year. We seldom get fog. In Nanoose Bay, we are far from the open ocean on the west coast of Vancouver Island where spray and fog are common. Anyway, I'm going to ignore the high salt reading and carry on trying to keep my garden happy.
I thought that it was your neighbor, who poured 20 pounds of table salt on the ground under his arbutus tree, near the property line? Salty water can easily flow horizontally, if the relief supports this flow. You don't have to be near the open ocean, to be affected by the cyclic salt, proximity to some sea bay is sufficient. Each year over 300 million tons of salt is carried into the coast by winds from seas. https://en.wikipedia.org/wiki/Cyclic_salt
