How Much Fertilizer do Tomato Plants Need?

how do you fertilize tomatoes correctly a lot of the discussions I see online talk about the right kind of mpk what is the ratio of those three nutrients that you should use but I very seldom see any discussion about how much of that fertilizer you should put on your plant what are the instructions on the boxes of fertilizer are those instructions complete enough so you can actually follow them and how do they compare to the advice given from professional people in agriculture in this program I'm going to answer those questions I'm going to have a look at several commercial products that are popular products that gardeners use and I'm going to compare them to see if they're adding the same amount of nutrients for your tomato then I'm going to compare that data to the expert data for that I'm going to use extension offices and research centers that know exactly what kind of fertilizer they should be using for agriculture I mean if they're trying to produce maximum yield they must know what they're doing right how does that compare to commercial gardening product fertilizing correctly requires two bits of information the mpk ratio and the quantity that you're going to add now the tomato is the most popular food crop and several manufacturers make so-called tomato fertilizer but they all use a different mpk the three products that I'm going to look at in this program are an 18821 a 346 and a 364 the 18821 is essentially balanced it has the same amount in nitrogen phosphate and potach which is the pottassium the 346 is relatively high in potash and the 364 is relatively high in phosphate how can all of these be the best fertilizer for tomatoes there's a really important concept gardeners need to understand when we're fertilizing the m PK depends on the soil not the crop your goal is to replace the nutrients that are missing in soil you do not feed plants and for that reason there really is no such thing as tomato fertilizer you have to match the fertilizer to your soil not the plants now in a soilless mix uh one you might use for seeding Tomatoes you don't get any nutrients from the material in the mix it's usually Pete Moss core or maybe decomposed wood and so there's no nutrients in that material even in the case where the manufacturer adds some fertilizer the amounts are very small so in that case you want to add an mpk ratio that matches what plants need which is 312 but in real soil the right mpk depends on the soil and every Garden is different without a soil test you don't know which mpk to use if your soil is quite good and it contains a reasonable amount of organic matter you probably have enough p and K in which case you only have to add the nitrogen growing plants need enough of all of the required 20 nutrients but the nutrient that is almost always limiting growth is nitrogen there are several reasons for this nitrogen is mobile which means that it moves with water and it's easily washed through the soil everything living in soil needs it including plants insects worms and microbes and thirdly it's not provided by the minerals in soil now nitrogen is also the nutrient that is not measured by most commercial soil tests it can be measured by home soil kits but they're so inacurate that the results really don't help very much that means that gardeners never know how much nitrogen to add but I'm going to give you some guidance for that the nitrogen and fertilizer is provided in different chemical form some are soluble also called plant available because they can be used right away by the plant these include nitrate ammonium and Ura other forms of nitrogen are tied up in large organic molecules like protein and these need to decompose before nitrogen is available to plants manufacturers call this insoluble nitrogen the problem with insoluble nitrogen is that you don't know how quickly it becomes available to plants some might be available in a few weeks but it probably takes several years for all of it to become available insoluble nitrogen can't be counted on to provide nitrogen to your plants in this growing season too little or too much nitrogen results in poorly growing plants it is therefore important to get the nitrogen level correct and in order to do that you need to know the application rate for the fertilizer you're using the application rate depends on three things the mpk value of the fertilizer that gives you the percent nitrogen in the fertilizer the area that you're going to fertilize and the quantity of fertilizer that's going to be applied for any given area if the fertilizer is to be made up as a liquid you also need to know the ratio of fertilizer to water to make up that mixture as you'll see in some of the comments in this program this information is rarely provided complete enough on fertilizer packages for you to add the right amount of fertilizer let's have a look at some commercial tomato fertilizers what do they recommend I selected three gardening products based on the fact that they are popular brands and that I could find most of the data I needed to do the calculation it's quite surprising that several other brands that I looked at don't provide basic information about how to use their product some didn't even provide the mpk pay value don't buy such products each of the selected products use different methods of application different coverage areas and different units of measurement making it difficult to compare products each also contains different amounts of soluble nitrogen for the purpose of the comparison I've normalized the recommendations and calculated the amount of soluble nitrogen that is applied to one tomato plant I have assumed that this tomato plant grows in a 2X 2T space and that you're growing it for a 4mon season here's the products I selected the first one is Miracle Grow tomato plant food this is an 18821 fertilizer that is all soluble nitrogen based on Ura the instructions say to mix it at a rate of 1 and 1 12 tablespoon per 1 and 1/2 gallons of water and to apply it twice a month by soaking the base of the plant that seems like a good set of instructions but here are the issues I have you really don't know how much to apply should you apply the whole 1 and 1/2 gallons for each plant do you use the 1 and 1/2 gallons for 10 plants a statement like soaking the base of a plant is pretty much useless to a gardener to make sure that they're applying the right amount of nitrogen for my calculations I've used half a gallon per tomato plant the second product I looked at was the burp organic tomato plus vegetable fertilizer it's a granular 364 fertilizer that has 1.8% insoluble nitrogen which means that only 1.2% of the nitrogen is available to plants it's applied at 1/2 cup per 10 square ft for bedding plants and one and 1/3 cup per 10t Row for establish vegetable Gard a cup is equal to about a half a pound this product should be applied every 2 months again this seems like good instructions but here are some problems with this 2/3 of the nitrogen is not plant available and there is no data to let you know how quickly it becomes available this is a problem with organic products such as the Burpee organic tomatal fertilizer the width of the 10t row is also not defined so you really can't calculate at the fertilizer per given area the third product I looked at was the espoma Tomato tone it's a granular organic fertilizer with an mpk of 346 that is 2.1% insoluble nitrogen one pound equals 3 cups and the instructions say that you should apply three tablespoons per plant twice per month application should be made in a narrow band 3 in from the stem sounds like good instructions but I have issues with this as well 2/3 of the nitrogen is not plan available and there is no data to let you know how quickly it will become available this is a problem with organic products the instructions say to apply the fertilizer 3 in from the stem the problem is that the feeder roots for tomato plants are not right beside the stem you really should be providing this fertilizer farther away from the plant I went through and calculated the amount of nitrogen that's added to plants for each of these three products Miracle Grow and Burpee apply about 1 gram per plant while asoma only applies .3 G per plant so there's quite a variation between these manufacturers the total amount of nitrogen added for each product was about the same around 7 G per plant the synthetic fertilizer Miracle Grow adds this amount in the form of soluble nitrogen so that it is immediately available to plant the organic fertilizers add the NIT as insoluble nitrogen if these materials are similar to composts The insoluble nitrogen will be released slowly over the next 5 years that doesn't help this year's crop so the organic products are adding less nitrogen to the plants than the synthetic fertilizer if the soil is low in nitrogen and organic matter as is the case for many new Gardens the plants are probably under fertilized and need to rely on the applied fertilizer for all of their nitrogen needs this means organic fertilizers need to be applied in higher amounts than are recommended on the package now in a mature garden that has lots of organic matter plants will get some of their nitrogen from the soil and the rest from fertilizer organic fertilizer can be used in this case so what do the experts say I also checked with three extension offices in the US to see what they recommend for nitrogen application almost all of their recommendations use soluble nitrogen the offices I looked at were Colorado State University of Missouri and Kansas State what I found is that there's quite a bit of variation from one office to the next and that was a surprise to me some of this variation may be due to Regional soil differences but I suspect other factors are play if you know why they're so different please let me know in the comments the average suggestion from these sources for nitrogen is 2 G per plant for each application and the total amount for the season is about 6 G the science of applying nitrogen is certainly well studied for agriculture but we're still fine-tuning that system a study in 2006 looked at increasing yields of tomatoes by applying more nitrogen and that study was done in Ontario and it found that application rates of 200 lb per acre or 8 G per plant produce the best yields this value is two to three times higher than the recommendation at that time it is also higher than the recommendation that the three extension officers gave now how do the extension offices compare to commercial products the extension offices are starting plants off with three times as much nitrogen as the commercial products with the total seasonal amount being 50% higher now in a soiless mix like Pete Moss the extension offices recommend a value of 200 parts per million and that's about twice what most fertilizer manufacturers recommend for gardeners so to summarize this commercial rates are much lower than agricultural rates on a season basis they're half as much when it comes to fertiliz ing newly planted Tomatoes commercial rates are about oneir of what the experts recommend why is there such a difference I suspect there are a couple of reasons gardeners tend to over fertilize and they don't measure very accurately by recommending a lower raate the fertilizer is less likely to harm the plant gardeners are also less interested in maximizing yield one less tomato per plant won't make much difference in a backyard and will hardly be be noticed by gardeners but that is very significant on a 50 Acre Farm there's another key difference between gardeners and agriculture gardeners use a lot more organic material to amend soil which in turn increases the amount of available nitrogen that means less fertilizer needs to be applied to provide a good level of nitrogen if you're careful about measuring fertilizer you can add more than the Box suggests provided you have not already added added a lot of organic material this would be of value to new gardeners starting a new garden bed but as the soil improves over time you don't really need higher levels of nitrogen if you're finding your plants aren't producing very well try increasing the amount of nitrogen now what about fertilizing other crops now each crop is a little bit different but for backyard gardeners you really don't have to worry about the differences even many tomato fertilizers mention other crops right on the label use the tomato fertilizer for all of your crops remember there is no such thing as a tomato fertilizer do you have questions about fertilizer what does that mpk really mean should you be using a balanced fertilizer like a 101010 I have a whole series of videos that answer all kinds of questions about fertilizing your garden and they're available in this list right here Happy Garden

Channel: Garden Fundamentals

Views: 52,743

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Id: TKuOUaTrEwU

Length: 14min 57sec (897 seconds)

Published: Tue May 28 2024