Nutrient deficiencies F20

追加: 2026-05-13

[00:00:00]okay well i hope you had a good break week and uh i hope you have got some of their midterms out of the way a couple of them is one more to go um the topic of deficiencies i know that we talk about implant signs too but i go over it again because a lot of students seem to forget what the symptoms are and these things are important for you to remember at least the major ones so um i go over again a little more detail with some more examples uh and then i'm talking a little bit about toxicities at the end of the uh this talk so let's get started um terminology that you need to know and look for with deficiencies again some of this should be review things like a purple petiole right so the petiole of the leaf showing purple pigmentation [Music] intervenal chlorosis or chlorotic veins necrotic spots which is a tricky one because uh and i think in your plant pathology you've come across leaves that have necrotic spots and uh that that is often more associated with toxicities or fungal infection or insect damage but let's keep it on the list then there's chlorosis of the margin of the leaf on the outer edge or tip burn right so things to to remember again i think i mentioned this before that macronutrients tend to be mobile and micronutrients tend to be immobile so you're npk you it's no surprise you find them on this side um we rarely talk about chlorine and nickel but we do talk about magnesium and sulfur and uh these these are more along especially sulfur on the line of somewhat mobile so we'll keep that in mind as we talk again about where to find it and remember the reason why we talk about mobile on a mobile immobile is because if a nutrient is mobile that means that it can be reallocated it's mobile it's like you know if you don't like your apartment you're going to pack up and move to another apartment so mobile nutrients if the plant is not happy with where you are it will take you and move you to another location and usually when there's a deficiency i.e not enough of a particular nutrient the plant will look at other tissues that have that nutrient and if it's mobile they'll remove it and then relocate it to where it's needed more importantly like the apical meristem and so things like nitrogen phosphorus potassium these are mobile and if the plants running short in the roots are not bringing enough in then they will extract it from old leaves at the bottom that don't get a lot of sunlight or maybe less efficient uh we'll remove them and then move them up to the top where new leaves are forming so it's sort of a self-preservation move right so that's why we talk about mobile and immobile um some nutrients like all these ones are built into the plant in such a way that the plant cannot extract them anymore so once they've been used it's done they're stuck it's permanent so these are the ones that are especially troublesome for plants and fortunately other than maybe iron and calcium they're not needed in much supply we talked a little bit about boron deficiencies with poinsettias because they seem to be inefficient at taking up boron but for the most part it is calcium and iron that you will see in your lives so let's review some of the obvious ones from plant science 2 nitrogen which is mobile right causes general yellowing of the lower or older leaves so your classic house plant has got yellow lower leaves and dropping leaves all the time the ficus at the mall is dropping leaves because they don't feed it they just water it so when you don't have enough nitrogen plants will will disassemble chlorophyll which has lots of nitrogen in it which makes the leaves go yellow and then they'll move the nitrogen up to the top of the plant where the new leaves are forming so nitrogen mobile nitrogen deficiencies obviously they present at the bottom with yellowing even the top leaves will be less green because there is less nitrogen to make chlorophyll but generally speaking the bottom is yellow top is like green really good example here this is actually a like a canola plant this is an orange tree showing yellowing on older leaves when it's a mature tree it's harder to tell old for new but you sort of look at each branch individually don't look at the whole tree um phosphorus you should also remember this i think in labs i've when i've asked you guys you for the most part remembered uh the key with phosphorus is purpling right and it is older leaves began because it is mobile so it starts in the petioles often but sometimes it's in the leaves in the case of tomatoes we see it in the leaves sooner than we do in the petiole as you can see in these photographs the phosphorus is fairly straightforward and when you you uh don't have enough phosphorus one of the key things is the plant is stunted internodes are shorter and that's we talked about that with the the crops class about growing plugs right there's some phosphorus deficiency outside one of the key things to remind you of is that phosphorus deficiencies often present in cold temperatures so when you're growing outside like in this photograph this could be just because there was a couple of cold nights and plants are very inefficient at extracting phosphorus from the soil when it's cold so they go purple strawberries which is one you might see in the greenhouse they are tricky with phosphorus and you get this sort of purpling on older leaves um that's one to keep an eye on okay let's move on to potassium again this is review you're looking at it's obviously mobile uh intervenoclerosis uh in the older leaves because it is mobile it often starts in the margins like on this tomato leaf here and then progresses to the entire leaf it all becomes necrotic and cucumbers you see cucumbers are a little tricky because there's a couple of nutrients that cause this sort of yellow hailing of the leaf you see this bright yellow that's forming but generally we like to say that that's a potassium problem uh it can also be related to chloride and uh that for the most part chloride but let's just let's just call it potassium for the most part when we see that and pepper plants a they have leather leather leaves uh sort of thicker leathery leaves they tend to show up as marginal necrosis on the on the edges as opposed to in intervenal margin uh necrotic spots so it's much more marginal in the peppers this is a close-up of a tomato plant showing early onset of potassium deficiency so on the margins and we're getting some yellowing and then it'll become inter venal necrotic spots as it matures and there's another picture of cucumber leaf showing potassium deficiency with the haloing or yellow chlorosis of the margins and this is in a an ornamental crop it's kind of a dogwood very pronounced chlorotic outer margins of the leaves classic potassium um i think i mentioned this that potassium is uh primarily used as an osmotic nutrient so expanding cells and when cells can't expand properly they they split and that's how you get that necrosis so they just become weak and die calcium so calcium we've talked about again plant science 2 but be a little more specific today about things like blossom end rot and tomatoes and edge burn in lettuce [Music] cupping in cucumbers we've already seen that and extensive necrotic spots and cucumbers and really pronounced calcium deficiencies with the lettuce i want to mention just briefly the the margins of lettuce leaves often become necrotic when you don't have enough calcium and that is primarily because calcium is moved and it's immobile right it's moved through the plant by transpiration we've talked about this a bunch of times with poinsettias with brac brack edge burn the same idea here with lettuce if you don't have enough transpiration calcium doesn't make it to the edges of the leaves especially the new leaves where the head tends to be more folded in on itself and more dense and you get higher humidity there remember one of the things that moves water through leaves is transpiration and if we have high humidity we don't get transpiration if there's no transpiration water is not moving through the tissues it doesn't pull that calcium to the edge of the leaf so really important with lettuce that you have fans for air movement to make sure that those delicate leaves have enough transpiration happening you can imagine a dense iceberg head of lettuce while the leaves are all folded in over each other that you're going to have localized high humidity that's going to make it difficult to move calcium so lettuce is particularly prone to it in the case of the cucumbers this was when we had insufficient uh nutrient supply because it was a combination of nutrients and water that's a photo from our greenhouse that i took sad and uh blossom end rot i think i have another slide coming up but when the ovary is first forming in the tomato the very end which is furthest from the petiole is more likely to be in have insufficient calcium and so then the cells don't form properly and they're weak and then as the ovary starts to enlarge as the fruit forms it tears the end of the ovary open which causes necrosis and you get that rotten bottom of your tomato there you go blossom end rod so this this problem started way back at the beginning shortly after the flower was pollinated like at this stage so if you don't have enough calcium even in the early stages uh you're gonna end up with blossom enron this plant actually has a lot of issues look at this dark margin here and light central parts of the leaves some interesting stuff going on there cucumbers will also get blossom and run a lot of times people just talk about tomatoes but it happens in cucumbers if you have the end of the cucumber rots easily or is soft then you did not have a cut enough calcium when that fruit was forming and again this is another picture showing calcium deficiency when the leaves are trying to form and with tomatoes the meristematic tissues can't form properly in the leaves are necrotic especially the very young sensitive tissues they will die uh with insufficient calcium because those cell walls just can't form and the the new tissues are growing so rapidly and if their cells aren't forming properly they tear and rip and and dry up and die um so yeah calcium is is very important and a lot of it is managing your environment in your greenhouse right making sure that it's not humid not too humid that there's enough transpiration happening on the plants um yeah so things like not enough nutrient being supplied or your humidity is too high because remember calcium uptake in a plant is passive in that the plant can only move the calcium through water movement in the plant which means that the stomata has to be open and there has to be actual evaporation happening from the plant if your greenhouse humidity is too high you're not going to have evaporation and you don't have water movement and you don't get calcium delivered to those tissues magnesium mobile uh intervenal chlorosis that's pretty straightforward this is classic uh what you're looking for with peppers same thing uh tomatoes same thing uh intervenol chlorosis pretty straight forward sulfur from plant science too i use this picture as well because it's it's it's uh pretty obvious that the eggplant on the right has overall yellowing and on the left does not now sulfur is what we call moderately immobile which means it presents all over the plant and this is species dependent so you have to sort of do the research on your your particular plants most plants present at the bottom and in the middle for sure and lastly at the apical meristem this is a pot mom on the right that has a sulfur deficiency a lot of times we would say this looks like nitrogen deficiency but that's actually a sulfur deficiency so that can happen if you're using city water and you don't have enough epsom salt sulfur deficiency is quite a possibility often well water has enough and surface water has enough sulfur in it that it's less of an issue if you're collecting rain water that can be an issue too so yeah it resembles nitrogen right that's terrible it looks like a w um iron deficiency again we've talked so much about this but i'm going to drive it home because i you need to know this it's got to be right on the tip of your tongue the second you see it right we know it's immobile so it presents at the top of the plant we know that it's general chlorosis it can also be intervenal chlorosis like here or just general chlorotic tissues like in a cucumber apical meristem uh typically it is insufficient supply but remember the first thing we check is ph all right i know you said oh derek we know that and i'm so happy that you said that because it means you know it um one more shot at cucumbers with iron deficiency and again just a reminder ph is a key issue here zinc immobile so it's a newer growth first now this one's less it looks a bit unusual i think it looks quite a bit different from iron in that the veins are much more visible so that's how i distinguish zinc from iron but the other reason you might want to distinguish zinc from iron is because zinc deficiencies are rare like the chances of you seeing one are are slim but there you have it that's what they look like the veins are much more pronounced uh i know in greenhouses that collect rain water it's never an issue because first of all rain is slightly acidic because it passes through the air and the air has carbon dioxide which is very water soluble that forms carbonic acid in the rain so rain always has a slightly acidic ph not crazy but slightly and that moderate acid in the rain as it washes over the greenhouse runs down the gutters to go to the cistern and all greenhouses have galvanized steel gutters because of strength and galvanizing is made of zinc and the acid actually etches some of the zinc off over the as the water runs along and that's more than enough that you for what you need for plants to have sufficient zinc so typically in greenhouses you don't see zinc deficiencies boron we we do run into um again we talked about this with poinsettias because boron is an issue so is molybdenum uh boron is immobile right it's essential for meristematic tissues so any new forming fruit or apical meristems if you don't have enough boron they become uh deformed and on this tomato you'll see that there's kind of a corky scarring around the top of the fruit that is from deformed tissues in the meristem and as the fruit formed it tore now unlike calcium with brackets bottom and blossom end rot which is at the bottom the boron presents at the top of the fruit so that helps you distinguish between boron and calcium when you're looking at tomatoes um one of the key things about boron is that it is passive it is passively brought to the plant just like calcium which means it requires transpiration so if you have a deficiency you have to look at your climate to ensure your climate is correct that it's active that there's enough transpiration happening the plants are actually evaporating water that it's not too humid so oftentimes cooler humid times of the year like the fall can be an issue or early in or late in the fall early winter when the greenhouse closes and your plants are still you know active you get a lot of humidity buildup and you have to open the vents and vent that off or you end up with problems this is another deficient nutrient deficiency key i'm not going to go over it it's just another one for you to look at if you need a study aid or whatever um let's do a little name that deficiency so this is lettuce what are we looking at you got it calcium so insufficient or insufficient air movement right that's that's the key with calcium uh what are we looking at here so i've got actually the next few are kind of tricky uh what do we got here so you see purpling and you see intervenor chlorosis you see a lot yeah there's a lot going on so we know there's a magnesium deficiency because the intervenal chlorosis now this is assuming it's an older leaf if this was an exam i had to make that much more clear but we also see purpling which means phosphorus right we're getting anthocyanin buildup so there's multiple things happening when when you see multiple deficiencies at once the first thing you want to do is go to your fertilizer tank make sure that the a and b are being pumped out in equal ratios and make sure they're both stocked uh because often when you see sort of compounding deficiencies there's some sort of fundamental problem that's much bigger than a minor deficiency there's this there's a big issue going on look at this little cucumber what's going on with that well there's a couple of things yellowing with fruit like cucumbers and zucchinis and some gourds it's important to understand that a lot of them their skin has chlorophyll in it that the outer uh epidermis and if they don't see enough sunlight the epidermis becomes ideolated in other words the chlorophyll disappears and they go yellow so sometimes the cucumber is tucked in the ground or it's buried under something and it gets yellow where it doesn't see sunshine the second thing we're looking at here is the sort of pinch central uh hourglass shape that means that there was insufficient water delivered to that fruit at a point in time and it's important to understand it only takes a couple of hours of interruption with irrigation for a cucumber to not form properly because they swell so quickly and once they swell the tissues kind of set and you can't fix it so uh that there's two things going on here right so the fruit was probably buried under something which made it yellow and there was a disruption in water supply causing the full fruit to deform what are we looking at here well we have yellowing of the apical meristem which tells us that it's an iron deficiency but we have deformed juvenile leaves this is a i believe a spinach that is not formed properly so we're looking at boron as well so this is another i'm kind of doing these tricky combination problems because uh you run into these things so you got iron and boron deficiencies going on here this is interesting this we have a cucumber that has hollowed out or the central axis has split um this is often the combination of irregular water supply maybe someone's thought of that insufficient calcium right so as the ovaries forming the cell walls are not properly attached and as the fruit swells it tears the center apart and the other one can be insufficient boron uh making the apical meristem weak so that when the fruit enlarges the tissues are not properly attached and lastly is excess nitrogen when you over supply nitrogen the fruit swells and grows rapidly this is sort of one of the classic things with nitrogen and potassium where we feed things like blueberries and raspberries and they end up being really big and we can fill containers to the grocery store with far fewer berries because the berries are so engorged and that's to do with irrigation and fertilizers which unfortunately make the fruit less sweet because you take the same amount of sugar that's in a wild blueberry and then put that into a swollen blueberry that's been fed huge amounts of fertilizer and irrigation and you get that sugar is diluted across a much larger berry giving you the sense that it's not as sweet when in fact the same amount of sugar is in each individual berry it's just there's a lot more water and tissue so over feeding fertilizer to fruits is something that you know california and florida farmers are well known for let's look at nutrient toxicity now so that is when you either over supply a nutrient so you put too much in or you have over availability as in ph uh this is a common one with things like iron and manganese um yes ph is important so just to remind you this part this is a key thing here right when you're looking at nutrient problems you want to make sure that it's over the entire crop because if you find one plant that has a deficiency you have to ask yourself the question what is going on to this one plant that it is experiencing this problem or the other ones are not and if it is a nutrient deficiency you don't find any insects more than likely if you look down at the roots dig into the soil cut the bag open you'll see that there's a root infection some sort of fungal infection that or aphids in the roots that are parasitizing the roots and weakening them so they cannot take the nutrients up as effect as effectively as the other plants in the in your crop so you have to do some detective work when you're looking at uh problems like that so whether it's a toxicity or or whatever deficiency this is this is something that you want to make sure logically is there's something unique to this plant is the ph wrong on just this plant why what could have gone wrong the other thing across different crops it is important to understand that crops are not all the same i mentioned this in one of my labs uh students that are interested in cannabis you know you would be well it would be well advised to understand the history of the plant and it's obviously related to hemp and hemp is actually used for remediating soils because hemp is very effective at taking up heavy metals and nutrients like that which means that if you over supply certain micronutrients you can actually reach toxic levels in certain plants and in fact cannabis is a crop where things like iron and manganese you have to be very careful that you don't oversupply because they will quickly show toxicity which would be localized necrotic spots purpley spots all over the leaves that's a sign that you've got toxicity um foliar feeding which is something we've talked about is another one that can be risky if it's not applied evenly right uh or if it's not mixed sufficiently sometimes in the tank they settle out you go have coffee you leave the tank you come back you start spraying again uh it's settled and for the next little while you're giving a much larger dose than normal so um it's important to you know whether you're applying it or mixing it that that is consistent the other thing is your math could be off so that's when you got you know there's no excuse after this you got to remember how to do that get the math right let's look at some toxicities so manganese and boron toxicity uh and this is sort of toxicities to be honest almost all look the same but at least you if you see this you have a good idea what you're looking at so early stages are marked by specs on the leaves with reduced chlorophyll now right off the top if you're looking at this geranium leaf and you've been doing ipm with graham you might say well couldn't that be stippling from an insect that's feeding on the leaf and you'd be right to say that so obviously the first thing you're going to whoops the first thing you're going to do is you're going to inspect the leaf flip it over look for insects are there mites under there what's going on if there's no sign of any insects then you move on to okay is this nutritional or is it fungal and then you again you have to get your magnifying glass out look to see if it's fungal um look at the conditions if it's fungal would it be the entire crop at once or would it just be one plant it would probably just be one plant at first if you're scouting regularly but if it shows up on the whole row or bun or section of your greenhouse then you're more likely to say okay we have a nutrient toxicity here so again using logic right so these spots you see these stippling spots or even marginally necrotic spots those are early signs of the toxicity so as manganese and boron toxicity progresses it looks a little more pronounced you get much larger necrotic spots it starts to look kind of like a potassium deficiency but and this picture doesn't show it very well but you can also get yellowing of the apical meristem because if you have excess manganese and boron they compete they actually out-compete the root spots for iron to enter the plant so by having excess remember how we talked about antagonistic and synergisms with nutrients excess manganese and boron will actually be antagonistic to iron uptake so you can also see a combination of necrotic spots and yellowing in the younger leaves as a result of excess manganese and boron availability either one and i'm going to say most likely manganese if you had to choose okay i i'm not going to promise but i hope to be done talking about nutrient deficiencies so if you're tired of hearing about it that maybe that's a good thing because it is an important uh thing to know about so i've got some interesting links in this week's folder for you to look at uh there's a paper there's some interesting discussions web articles if you're curious have a look at them nothing of it none of it's required but might be of interest to you if you have time i know you can be pretty busy now that you're back from break week and things ramp up again but okay see you in the greenhouse