Organic Fertilizers F20

Ajouté : 2026-05-13

[00:00:01]all right um today i'm going to talk about organic fertilizers you may remember we talked about this in plant science 2 but before i talk about organic production a little bit more i want to talk about nitrogen metabolism because essentially nitrogen is kind of the the critical nutrient around everything that's what everything sort of pivots on so let's try to better understand how nitrogen is metabolized so let's dig into this there are two paths for nitrogen in plants and it's important to be able to distinguish between the two one is in the soil which you've talked a little bit about and the others inside the leaf so now inside the plant nitrate right that's our nitrate fertilizer is ultimately converted to ammonium in the leaves which are then eventually converted to protein which is what makes things happen in biology right proteins are the little molecules that make you and me up and actually make a lot of the enzymes that are plants so that's effectively what this is all about is making proteins so the plant is trying to move things around and shuffling the nutrients to ultimately get to this goal um we spent a lot of time talking about ammonium and nitrate and we're gonna continue again today and maybe it'll make even more sense after today i hope this can be a complicated topic so hopefully you uh follow with me okay in the soil and we've talked about this in plant science too we know that bacteria do a lot of the heavy lifting they do all the conversion from ammonium to nitrite and from nitrite to nitrate so it's kind of really what causes some confusion in this topic is that right off the bat you're going to see that in the plant we're going from nitrate to ammonium and in the soil we're going from ammonium to nitrate you might say well why not just absorb ammonium because ultimately that's where a closer step to protein right well there might be some validity validity to that statement but let's let's follow the process and and see where it goes so nitrate is absorbed through roots right it's processed either in roots or leaves it requires sugar to be processed to amino acids so the plant has to expend energy to process it and sugars are most abundant in leaves which makes sense because that's where photosynthesis is happening so you can see if you're going to process the nitrate in the roots that means the plant has to move sugars all the way down to the roots which is a rate limiting step it it slows the whole thing down it costs energy um so the plant's not really excited about that if plants get excited but effectively the little industrial machines that they are they're like no i really want to move that to the leaves if i can um so they would rather move the nitrate to the leaves that's their preference so we have two scenarios when nitrate levels in the soil are low right so there's not a lot of nitrate in the soil the plant is is anxious for that food it's going to process it in the roots right away when nitrate levels are high it's processed in the leaves so you know obviously we're talking about agricultural context here so typically nitrate levels are high so that means that the plant's going to reallocate the nitrate to the leaves and process them there which is the most efficient so in the sense that sugar is abundant in the leaves and oxygen which is important for the process is also abundant uh now looking at ammonium right we've talked about ammonium and in how as a nutrient we have to be careful with it because it creates soft growth etc etc um i also alluded to how ammonium is not really a good cold weather fertilizer it's more of a warm weather fertilizer so let's have a look at this ammonium in the roots needs to be converted immediately into something else because it is toxic to the plant um and of course that means that it's going to use oxygen and sugar because it has to be done in the roots not in the leaves so that has a metabolic cost so ammonium has a cost where nitrate has a cost but it seems to be slightly less so at cooler temperatures right that's when the root zone is cool there's less sugar and less oxygen which makes ammonium a poor choice so we often talk about ammonia being a warm weather feed not uh not a cold weather feed um so typically plants that need lots of sugar above the soil line so plants that have a either grow rapidly or have heavy fruit loads or very large flowers like tomatoes peppers and rapid growth like lettuce they generally don't want any ammonium at all they want to they don't want to waste their sugar and they have enough in the leaves up top so they're they're going to want to be as efficient as possible so they don't really want to move uh stuff down to the roots so it's not really a good choice to be using ammonium in that context so in warm sunny conditions ammonia may be a better choice uh than nitrate to some extent right uh you've got lots of oxygen there's plenty of sugar so it's it's confusing but generally speaking if you look at the industry fertilizers what typically happens to try to simplify this is in the winter months you'll see almost no ammonium in the recipe and as we move to the summer months ammonium starts to ramp up up to maybe 40 percent of the fertilizer because the plants can actually handle it there's enough going on there's higher temperatures in the soil you get nitrification happening uh the plants able to process it once it's in the root because there's more sugars available uh you know whereas in cool temperatures the bacteria in the soil are too slow there's maybe not enough oxygen and the plant has slightly less sugar because there's less daylight it's just too much of a metabolic cost to rely on ammonium in the winter months so here in in terms of you know sunny warm conditions right this is sort of where ammonia might make sense if you look going from nitrate all the way to protein we have to go through nitrite then ammonium then glutamate and then protein that's how many steps are involved whereas if you feed ammonium you go ammonium to glutamate and then directly to protein so if conditions are such that the ammonia can be processed quickly enough without too much of a metabolic cost ammonium can make sense so that's why i'm saying that ammonium is really only applicable in the summer months when we have sufficient sugars oxygen and temperature to process it remember we're talking about both soil and hydroponics here and soil has bacteria right which are able to process the ammonium to nitrate in the soil right and that makes the entire thing work more effectively whereas in cold soil the bacteria cannot process it and you might end up with ammonium in the roots which ends up having a toxic effect on the roots because remember ammonium is not very good for the roots it needs to be converted quickly to protein but that happens up in the leaves so very difficult to work with that in hydroponics there are no bacteria whoops i was supposed to erase that in hydroponics there's no bacteria so we do not get conversion of ammonium right so it accumulates in the roots quickly and can reach toxic levels so that's why typically in hydroponics you see very little if not zero ammonium in fact if you remember from your spreadsheet the only ammonium you typically see is the amount that's contaminated in calcium nitrate remember there is a small percentage oh man i'm terrible at writing with my mouse there's a small percentage of i think it's point six percent of by weight in fertilizer grade uh calcium nitrate is ammonium nitrate so in soil it's okay provided there's enough temperature so a nitrification happens in soil but not in hydroponics it also happens in aquaponics so remember that is ammonium going to nitrite going to nitrates we have nitrosomas and we have nitrobacter that are doing all this work in the soil and you may remember from plant science 2 i've used this picture many times the idea that you know nitrogen bacteria can produce ammonium the ammonium is goes through nitrifying bacteria to nitrates and then they get converted to nitrates and hopefully it is assimilated into the plant to make protein but there are always competing bacteria if conditions become too cold or wet or insufficient oxygen and they will actually convert the nitrate to nitrogen gas and we lose it so we don't want to grow too wet you have your soil wet all the time all your money and energy put into buying fertilizer is wasted because the denitrifying bacteria will just stump you and crush your nitrogen levels so don't grow too wet so what's the take home plants can use ammonium but it too much of it is toxic hydroponic uses ammonia uses too much sugar and mainly because it has to be processed in the roots to avoid toxicity and it slows growth so we don't use it and remember any ammonium in the fertilizer will not be nitrified in the root zone unlike soil so again in organics we avoid it in hydroponics in soil ammonium is converted to nitrate which is toxic and if it's cold it takes too long to convert to nitrate which means plants can be damaged so we avoid too much ammonium when it is cold so those are the the key takeaways from that thing right so plants can use ammonia but too much is toxic ammonia must be converted in roots fruiting plants will slow sugar is used to basically convert ammonium leafy greens will slow down if there's too much ammonium present uh ammonia can be converted i'm just reading this you can read it too just i think i didn't realize i had so many summary slides um oh yeah this is a good one ammonium can be sprayed so you can fully feed it remember we just talked about processing in soil and in roots but if you spray it on the leaves it's a shortcut so foliar feed fertilizers often have ammonium in them and you see a very rapid response in the plant and there's a place for that i've done it myself there's a chemical called nutrafog with the chemical it's basically ammonium uh based fertilizer that's in a solution then you fog it in your greenhouse and it will quickly absorb into the leaves and you get a real boost in growth if your crop is behind schedule you can kind of catch up by almost a week by fogging a couple of times a pretty cool trick [Music] also remember ammonia helps acidify the soil so when you're designing a fertilizer program for in soil uh it's it's a good idea to incorporate some ammonium because it will help keep the ph under control if you just use nitrate alone in soil then the ph will constantly creep up now if you think about it when we're doing hydroponics for this class we're working with the tomatoes and peppers and cucumbers do we ever add alkaline components to the tank no we always add acid and the reason we're always adding acid is because our principal nitrogen component is nitrate which raises ph so in soil you can have ammonium in the fertilizer mix and then you can keep your root zone at the correct ph without having to constantly add acid so you'll notice if you're growing in peat moss and coir you're not really too concerned about ph as much because of the ammonium content another important uh thing that i added on here towards the end of this was yes ammonium is a cation right has a positive charge and as such it can compete for other cations namely calcium and again growing things like tomatoes where blossom and rot can be a real problem you definitely want to avoid ammonium in the fertilizer because you will end up out competing calcium at the roots and the plant doesn't get enough calcium and then you get blossom enron so this is yet another summary now this is good maybe to help you study for for your final with this kind of stuff when you come back here to look at it um what i want to highlight from here calcium magnesium can be out competed with ammonium we just talked about that i'm gonna skip that all right let's talk about organic fertilizers again i did mention this is kind of picking up from plant science too so you'll recognize some of this um organic farming versus uh it's sort of like the in your mind we often think of you know an old tractor and a nice big garden people harvesting but in truth organic farming has become business and it looks like this um it's not nearly as romantic but organic farming is important i looked up various definitions and i decided to go with the encyclopedia britannica one um it is defined as an agricultural system that uses ecologically based pest controls and biological fertilizers derived largely from animal and plant wastes and nitrogen fixing cover crops modern organic farming was developed as a response to the environmental harm caused by the use of chemical pesticides and synthetic fertilizers and has numerous ecological benefits some of that is debatable but for the most part i'd say it's true i thought it was a fairly fair assessment um so remember organic fertilizers are not readily available to plants i'm going to sound like a broken wrecker but i i find that students uh struggle with this concept you know with our organic cucumbers we added alfalfa meal and blood meal and all these different things and we're just we feel like we're fertilizing the crop but really we're not what's actually happening is we're feeding bacteria and the bacteria have to process all those complex structures into the exact same molecules that we supply with synthetic fertilizers because that's what plants look for so they have to be mineralized right so bacteria have to break down decompose these are the decomposers bacteria protozoa fungi they have to decompose those organic fertilizers into the constituents that plants can use which means they need the correct temperature ph and oxygen lastly and i didn't talk much about this in plant science too but fungi are critical we did talk about mycorrhizae but fungi are also really critical in delivering nutrients to plants specifically phosphorus so yeah plants do not absorb organic molecules i really have to stress this because there's a lot of people selling stuff to to home growers that are lying plants do not absorb organic molecules they absorb inorganic molecules like ammonium nitrate phosphate calcium magnesium they do not absorb enzymes they do not absorb proteins only bacteria will consume those things break them down into exactly these sorts of things and then plants will absorb them all right so let's be clear on that so when you're reading some of these bottles that you see at the hydroponics store and they're adding all kinds of large complex molecules beware that you're not necessarily buying something that plants can actually use um so yeah i mean as animals we have stomachs that have bacteria and we have acids that and enzymes that break down but everything in their stomach actually breaks down whatever we eat into nitrate ammonium nitrate and phosphate etc so we're really no different except we have an ecosystem in our stomach that's taking care of all that decomposition um all right so let's move on so organic fertilizers need conditions favorable to nitrifying bacteria that's nitrosomos and nitrobacter that convert from ammonium to nitrate and nitrite to nitrate which means we need oxygen moisture and warmth remember from our last or the beginning of this lesson if it's not warm the bacteria cannot convert ammonium past nitrate very quickly and we end up with too much nitrite in the soil which causes toxicities or roots and actually can kill the the plant or do a lot of root damage and this is probably on a statement again i really sound like i'm repeating myself but it's so important that everyone understands there is not a single organic fertilizer that produces nitrate that that provides nitrate directly to the plant there's no such thing which means that what does that mean what are the implications it means that you're always working with potentially a lot more ammonium and you have to be extra extra extra cognizant of the fact that you need sufficient temperature moisture and warmth for the organic fertilizers not to do damage which means cool weather growing is very challenging or you have to just accept very slow growth and not push the crop because you will end up killing it um now oftentimes organic farmers probably never clued into this because when you get root toxicity from nitrate levels it looks like kind of pythium or phytophthora or fusarium attacked the crop and it died and they say oh it just bad luck but really what happened was the the roots suffered from uh root collapse from high nitrite levels because the bacteria were too cold so important to make that distinction i wanted to briefly talk about sugar because a lot of people buy sugar you can buy this is a bottle of molasses people make their own sugar is a complicated topic because of course plants make sugar right and i just finished telling you that plants don't absorb large complex molecules only inorganic molecules and that is completely true where sugars came from where the concept came from is actually tissue culture if you go back to your plant science one class we do know that when tissues are removed from soil and put into a sterile remember sterile environment that means no bacteria sterile then the plants can absorb the sugars and use them especially if you take the tissue cut it stick it into a gel and the tissues are so wet and soft that the cell walls are loose and things can easily move through the tissues to the membranes where sugars can pass across you're bypassing the roots effectively but let's be honest growing in soil or hydroponics is far from sterile and there are bacteria and so adding sugar what does it feed does it feed the plant no not really what ends up happening is the sugars are consumed by bacteria and unfortunately it's 99 of the time it is the wrong bacteria and sometimes even yeast grow and things get really ugly um when you have sugar in your soil bacteria grow rapidly just think about you know yeast and bacteria in your kitchen when something goes horribly wrong you know orange juice gets really bad uh you can start to build pressure if you're making beer at home and you add yeast what do you do you have sugar in the in the beer you add yeast and it rapidly grows and grows and produces all kinds of gas and in the soil what ends up happening is that this rapid growth of the wrong bacteria consumes nitrogen from the soil and consumes oxygen from the soil so your plant really suffers when that happens it's it's very dangerous um i i can't see a real benefit from it at all so typically we get fewer nutrients for plants and reduce oxygen the only thing that can be a benefit from adding molasses is that molasses is fairly high in iron and so if you have an iron deficiency in your crop or your crop is grown at the wrong ph if you over supply iron through molasses you may rectify the iron levels and the plant may look greener but it will not grow better and often shortly after you make it look a little better things go downhill quickly because of the bacteria and yeast growth so not a fan of this i think this is a bad idea and it's not founded on science um and there's lots of people that are going to disagree with me on that on youtube but you know take this to a soil scientist or a plant scientist and they'll back me up on it uh this in case you want to look at it even more this is beat molasses all right this is a fresh analysis of beet molasses just molasses let's highlight a couple of things right off the bat look at sodium i think most of you know that plants do not like sodium eighty two point seven five percent of fresh weight is sodium and then what little calcium potassium and iron you get look at that point four percent it's really not a lot yeah there's some there but not a lot and the rest is water so we're looking at sugar water and sodium you tell me what is your what does your gut say about that if it's helpful or not so think that through if you're spending a lot of money at the hydroponics store uh this is just another nitrogen cycle slide i found on the net to remind you of the ammonium to nitrite to nitrate to hopefully assimilation by plants and if the soil conditions are incorrect denitrification lost to the atmosphere as nitrogen gas and if you leach the nitrogen into the water you get eutrophication and algae which of course would be horrible and is what all the florida ditches look like around the orange groves i wanted to talk a little bit about omri when you get into the world of organics you'll see the term omri that stands for organic materials review institute that's an organization that was established in eugene oregon to certify inputs and it's important that i distinguish this is not an end product organic certifier it is an inputs certifier in order to grow organically you need to certify all your inputs so that whatever comes out the other end is still certifiable so omri certifies things like fertilizers substrates pest control products and even preservatives for certain food products that are grown or produced organically so again i usually ask this question on the final make sure you understand that omri is just for input certification uh let's do a quick summary one more time of organic fertilizers now that you've had some time to sort of percolate over what you learned in plant science 2 and you know in the summer if you took that so manure which is a classic fertilizer used by a lot of people in agriculture is actually a very complete fertilizer in the sense that it is balanced your npk ratio is pretty balanced but your numbers are very low very very low remember manure is high in ammonium and urea and it uh it is it is a typically sold as composted and to be honest when once you compost manure there's almost nothing left so not that that's not good for your soil but compost manure has other benefits for your soil but it will not have a massive nutritional benefit so a lot of farmers use raw manure which stinks and has food safety hazards and stuff like that so you can't use it in all contexts right you're not going to spray raw manure in your tomatoes just before harvest that would be disgusting um but when it's well composted there's very little nutritional value [Music] and a lot of the stuff do does need decomposers to break it down to release that so anyways manure is popular in field production i have not seen it uh other than our horse manure in our mushroom compost but cow manure goat manure sheet made or not seen it bone meal uh bone meal is one that we just got delivered at the college which is pretty cool look at the ratios you'll see basically it's high in phosphorus which makes sense if you understand what bones are made of they're made of a lot of phosphorus it's kind of funny you always think of bones as calcium oh bones calcium that's true there is calcium in bones but the vast majority of bone is made up of phosphate structures so that's where grinding bone and using it as a fertilizer is is an excellent way to get phosphorus into your soil really important in organic production that you use some sort of mycorrhizae inoculation to improve the delivery of the phosphorus so if you're growing in soil and you have conditions that are favorable to mycorrhizae then you want to do that because that will make it that much more efficient uh implants nice to talk briefly about some of the risks i don't want to get into that stuff but yeah your bone meal that could be cow diseases same with blood meal uh but the blood mule have the collagen is also an excellent source of nitrogen which is great uh for plants it's also very high in iron because obviously blood has iron in it that's how it holds oxygen um blood meal is a fairly fast decomposer so remember we talked to plant science to about different speeds and trying to match the speeds um blood meal is very quick so you got to watch what you're pairing it with if you want to keep your nutrients in balance you also have to make sure you don't overdo it because iron too much iron is toxic right remember we talked about micronutrient toxicities so blood meal is very useful but gotta be careful um typically it is a ammonium form of nitrogen that it delivers so keep that in mind as well which is obviously very common in organics feather meal uh typically we're looking at you know basically decomposers which you know so you're going to get nitrates and ammonium based on the conditions of the soil [Music] it's a slow release but it's also an excellent source of nitrogen um probably a a better match uh for slower potassium type fertilizers but it's definitely a good one i don't know i talked in plant science too a little bit about some of my concerns about uh trace heavy metals because of feathers and drugs that are used with chickens so i mean if you know your feathers are being sourced from an organic chicken farmer that would be a lot better but to be honest there's not many organic chicken farmers so it would be really difficult to source enough feathers but i don't know of any organic feather meal that is actually has certified inputs um yeah that would be tricky maybe you should look see if we can find an omri certified feather meal i don't know um fish meal this is one fish oil has been used fish meal uh essentially what you're doing is you're adding protein to the soil and then you're hoping the bacteria will convert that to nitrogen uh it is a tricky one because you know that much protein which is a fair amount if the wrong bacteria start growing things can kind of go bad pretty quickly so you gotta really know that you have enough oxygen warm enough conditions and not too wet and not too dry so you got to be a confident grower to pull that off fish oil is a much quicker reaction and you add smaller amounts so you can sort of feed it you know in a narrow window of time and then have a break as opposed to fish meal where you add it and now it's in there and you can't do anything for the next three to six weeks while it breaks down right so fish meal is a little quicker it breaks down quicker because you're adding smaller water soluble amounts um i won't get into the foxy quinn stuff yeah fish motion it's mostly uh from the industry that makes fish oil supplements like cod liver oil additives or what they the uh what is it beta omega fatty acids uh those vitamin supplements you see in stores it's big business and so these little fish are harvested from the atlantic and caribbean ocean and pressed for their oil and the meal that's left over is treated with phosphoric acid uh to preserve it and so what actually happens when you have uh fish emulsion it has phosphorus in it from the phosphoric acid so it has a decent nitrogen source a little bit of potassium and it has phosphorus and it lowers the ph so it's not a bad uh that's why often you see fish emulsion being used by organic farmers and because it's a fairly fast decomposer uh you get a bit of a more immediate response yeah here's the picture of the these schools of manhattan little fish like sardine things that are just basically scooped up and crushed that's i don't know feel a bit sad but whatever um [Music] feather meal talked about this back there i don't really want to get it again uh alfalfa meal yeah 2.5 to 1 to 1.

[00:33:30]we have this at the college i i like this it's a nice slow release but not overkill the only question you have is where and how was alfalfa grown right was it organic again you have to find an omri certified one i haven't um soybean meal this is interesting it can be phytotoxic again we talked about that in plant science too a little bit but uh certain things like lettuce and turnips if you really want to grow turnips please don't but if you do be careful some scientists figured out that soybean meal is actually toxic to them and they'd not recommend it for seedlings um cottonseed meal this is a really important one for crops that need a low ph it is one of the only fertilizers that will lower the ph of your soil other than maybe fish meal a little bit because of the phosphoric acid but cottonseed meal is really important for getting the ph down interestingly coffee grounds will also lower ph if you use coffee grounds so algae meal this is high-tech futuristic stuff using human waste uh i think at some point in the future you'll see this but it's not widely done yet but i like talking about it because i think it's so cool and i know a lot of research has been done on it in preparation for the future so you know maybe when you guys are my age it will be a little more mainstream but not yet it's too bad because i think it's really powerful you can do a lot of stuff with algae it's pretty cool um seaweed kelp we have this at the college remember one zero three it is a low rate slow to break down and uh and is high in potassium which is really important because it's not a lot of potassium out there in the nutrients we've been talking about so i think kelp is a good backbone for a lot of fertilizer programs you know it appears sustainable because it's kelp and the sea but the truth of the matter is that kelp provides habitats for like otters and fish to hide from predators and you can imagine you know now that the organic industry is fairly small the footprint for harvesting kelp would be somewhat minimal but you know like everything as it catches on if it gets bigger well once again there we are harvesting all the kelp destroying a habitat so i don't know i mean as much as i like it i'm not sure if it's a a long-term solution and then guano we talked a bit about that in plant science 2 which is basically nitrogen let's look at a couple of fertilizer breakdowns this is uh cottonseed meal phosphate which is crushed stone wood ash limestone crushed stone and kelp meal that is a pretty standard uh feed for a moderately acidic now you notice there's four parts cottonseed meal and wood ash wood ash is alkaline cottonseed is acid so they sell offset each other so the ph doesn't go crazy but you get a good source of potassium from the from the ash that's one of the reasons why it's called pot ash right um and limestone also raises the ph and that's your source of calcium which of course calcium is very difficult to get in organic fertilizers not a lot of sources [Music] here's another complete organic fertilizer mix these are examples of commercially available ones so this is kelp meal bone meal soybean meal and then we've got dolmetic lime and agricultural lime which have calcium and magnesium in them but these i i think it's a bit of a stretch to call it organic when you've got mined fertilizers in it but realistically if people are less dogmatic some of the organic people are like crazy about this but realistically i think the future is a compromise you know instead of just saying you're in that camp i'm in this camp let's pick the best of both and make it work as sustainably as possible and that's where you know using some lime in the recipe makes some sense um in the folder for this week there's this spreadsheet i did briefly show it to you in plant science 2.

[00:38:26]i would love it if you played with it i don't have an assignment for this i decided not to do that instead we have um the organic paper review which i'll post uh probably on wednesday for you to look at and do a summary and i'll have all the instructions and what you need to do but this is a really the only website only spreadsheet i've seen where you can pick and choose different fertilizer inputs to achieve kind of a nutrient target nutrient ratio so just like your fertilizer assignment we had target set points for nitrogen phosphorus potassium calcium magnesium and it's really difficult to do that with organic fertilizers and so these researchers have come up with specific analyses and breakdowns and then you enter in your number in the spreadsheet and it calculates the ratios that you would be applying so it's a really useful tool for trying to build uh organic fertilizer that would have the correct ingredients for your crop so this is just a picture of it the actual spreadsheet is uh in the folder for what is it week 10 so all right that's organic you learned a little bit about nitrogen metabolism you're probably going to want to go through that a couple of times look at the slides um but the gist of it is remember that the plant has to con has to give up energy to process ammonium uh and it has to make decisions so when we over supply we supply lots of nitrate to the plant not over supply but provide a fair amount the plant can easily take it to the leaves and you get your maximum growth because it doesn't have to do a lot of conversion in the roots and shuffling uh think of it like moving inventory back and forth it's just simple move the nitrate to the leaf process it but when it's it's uh when nitrates are low levels then the plant has to process it in the root right away uh to make sure it has enough protein for everything and then ammonium i remember ammonia has to go through a nitrite intermediate before it's converted to nitrate in the roots because it's it's it can't be absorbed directly so that is where toxicity can be a problem if it's too cold because it doesn't get converted quickly but you can fold your feed ammonium if you want to sidestep all this to grow the quickest but that is you know not always feasible um and then we talked about nitrogen in the soil right so bacteria being able to have sufficient temperature to convert ammonium to nitrate uh so that we don't have toxicity in the roots so there's some confusing overlap between inside the plant and inside the soil so try to keep them separate and that will help you understand how that all works okay see you in the greenhouse