Dealing with Water-Retentive Soils
tapla
11 years ago
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jojosplants
11 years agolast modified: 7 years agosissysimone
11 years agolast modified: 7 years agoRelated Discussions
Soil Smack Down: Peat Moss vs. Coconut Coir: Compost Wins!
Comments (10)The idea that agricultural use of peat contributes to an unsustainable harvest rate is far from the truth. I would concede the point if everyone in Canada and the northern tier of states was burning it as fuel, but consider: In Canada alone, there are more than 270 million acres of harvestable peat bogs - that's harvestable. Not taken into account are the millions of additional acres of bog that are not deemed harvestable because of their size or location. If we make the conservative guess that the harvestable portions of these bogs are 10 feet deep, that means there are probably more than 900 billion cu. ft. available for harvest, just in Canada! That doesn't even take into consideration what's available in Europe, Asia, or places like New Zealand where they also mine peat. Canada currently has mining/harvesting operations underway on approximately 40 thousand acres or about .014% (that reads 14 one thousandths of 1 percent) of their harvestable peat. You'll find the math accurate and conservative. It's more likely that the next Laurentide Ice Sheet will be upon us and glaciers will have covered what's available before we even use a notable fraction of one percent. As peat bogs grow, their depth is increased by a paltry 1mm per year, approximately. Based on current harvest rates in North America, peat is accumulating at a rate approximately 70x greater than what is being lost to harvest. You can probably tell I don't feel guilty about using peat. I agree that both peat and coir can be left out of the lawn/garden equation altogether, and compost would also be my first choice as a top dressing or soil amendment, but we part ways again when we turn to use of peat vs coir or compost in container media. Peat and coir have moisture retention curves that are close enough you would be hard pressed to say one has much advantage over the other. Coir does have less loft (so less aeration) and tends to compact severely if watered from the top or used as a large fraction of a medium - more than 25%. For this reason, most greenhouse ops that use significant amounts of coir in their media sub-irrigate. Too, one should not think all that needs to be done is substitute coir for peat in container media and all will be well. Coir is chemically different than peat and requires work-arounds if we are to avoid unnecessary limitations of plant potential. For example, coir is often high in salinity and can contain toxic levels of Na. It has an extremely high K content, and it's notably higher pH (than peat) means dolomite is not suitable as a liming agent/source of Ca/Mg. Gypsum should be used as a Ca source, which acts remedially to fix coir's low S content as well. My go to medium for garden display containers/veggies is (by volume): 5 parts pine bark (dust to 3/8) 1 part perlite (medium - soil mix grade) 1 part peat (more or less - depending on the particle distribution of the bark) Dolomite Micromax I've done a number of comparisons between plants grown in the medium above, contrasted with media in which I substituted coir for peat or CHCs for the pine bark, and the results were extremely telling ..... which is what started my investigation into coir and why it might be performing so poorly. What I use for short term container plantings - no more than 2 years: What I use for long term plantings - woody material growing on as potential bonsai, and refined bonsai; succulents; cacti; anything that might be in the same medium for more than 2 years: It's equal parts by volume of screened pine or fir bark, screened Turface MVP, and screened granite in grower size or screened quartzite in size 2. There are no fine particles in this mix. Some mixed plantings: Al...See Morered cedar in contaner soils?
Comments (1)Also are there negative effects of using the red cedar for mulch around citrus trees, flower beds, or pine trees? If there are, are there specific plants or plant groups that cedar should not be used as a mulch around?...See MoreSoil for newly propagated succulents
Comments (12)I realize this is an old thread, but generally speaking, commercially prepared potting media are a poor choice for any plant that doesn't tolerate wet feet w/o protest, and Crassula falls in that category. Even those media labeled as being suitable for succulents and cacti very rarely are good choices, it's not what's ON the bag that determines a medium's suitability, it's what's IN it that counts. Generally speaking, commercially prepared media are too water-retentive even for plants that prefer an evenly moist medium. The reason lies in how much perched water these media support, which commonly ranges from 3-6". Perched water is water that takes up residence in a 100% saturated layer of soggy soil at the bottom of the pot, and refuses to be dislodged by the force of gravity. It sits there until it eventually evaporates of the plant uses it. The trouble with the later is, soil saturation very quickly kills the fine roots which do the plant's heavy lifting. When these roots die, the plant's chemical messengers tell plant central to halt all top growth until a sufficient volume of new roots are brought online to support new growth. In most cases, the grower uses a digital moisture monitor, their forefinger, to check moisture levels. If the top inch or two of soil is dry, they add more to the saturated layer at the bottom of the pot, which is still waiting to evaporate or be used for the plant. This very often results in the cyclic and never ending death and regeneration of roots, which is paid for by energy that would otherwise be put toward growth or ensuring the healthy glow we all covet. Media that holds no, or very little perched water is a much better choice. These media will always be based on an VERY high % of coarse ingredients, usually between 75-90%, with some smaller particles mixed in to adjust water retention to suitable levels; this, because it's primarily soil particle size that determines how much excess water a medium can/will hold. Media with high % of peat, coir, compost, composted forest products, sand (other than horticultural sand which you would likely consider gravel), topsoil, in any combination lead to watering issues that rob plants of most of their genetic potential. The most productive media will hold water inside of porous particles, on the surface of all particles, and at the interface where particles contact each other, and there would be no appreciable amount of water in the spaces between soil particles. In order to achieve that end, a very large fraction of soil particles would necessarily be large/coarse to achieve that end. Something like this would be an excellent choice for a huge % of succulents and cacti: Al...See More100% Compost or 50% top soil, 50% compost
Comments (1)Well, your leaves and manure will do a lot of what the compost does, so I think I'd get the 50-50 mix. (I'd want to be sure it was yard waste with no pesticides too!!)...See Moretapla
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