Nutrient Ratios for Modern Crops
by Erik Biksa
2009-08-01
Who has determined what the N-P-K values and ratios are that you feed your prized crop through the vegetative and bloom phases of growth? What about other important macro elements such as calcium and magnesium, and the complex relationships that trace elements such as boron, iron, zinc and manganese have with the other nutrient ions that influence the health and development of plants? There are 13 elements that are considered vital to plant growth, with many others showing to be beneficial. This gives a lot of possibilities in terms of the potential ratios and concentrations that these elements may have in a crop feeding nutrient solution; for example think, of the possible number of combinations you could have rolling 13 dice all at once.
As indoor growers we are applying too much phosphorous because the recommendations for applications and formulations have been based on outdoor field agriculture practices.
So, now back to the question: “Who has determined the nutrient values and ratios in your crop feeding program?” All right, well most folks are likely to say “the manufacturer.” Okay, so the manufacturer determined the nutrient ratios. That beckons the question of how they were able to determine what concentrations and ratios of plant nutrient elements to provide for your particular crop and at what times in the vegetative and bloom phases of growth. Well from there you can only guess, unless you have information that says otherwise.
Chances are that the nutrient solution was formulated based on previous research that was performed on the nutrient requirements of various crops. Obviously, any reputable nutrient manufacturer will have also tested their formulation and will make adjustments, as required. There are hydroponic crop feeding solutions that were formulated in 1865, although Hoagland appears to have created the first “complete” nutrient solution in the 1930s. Since then, modern scientists and horticulturalists have learned much about plants and their nutrient requirements. One of the key points of knowledge is that different types of plants use nutrients in different quantities and ratios; creating preferred nutrient profiles for various types of plants. On top of that, the same type of plants will use nutrients differently when grown using different cultural practices or when grown in different climatic conditions. For example, outdoor field crops in natural settings that take six months to reach maturity versus indoor crops grown in artificial environments that will require only three months to reach maturity are hardly playing on the same ball field.
What does this all mean, and where is this article going with it? Well, to put it bluntly, there are a surprising number of nutrient formulations that are simply “wrong” for modern indoor growing, and here’s why:
* The formulation(s) has been based on un-applicable or less relevant research information. The data gathered growing field crops using conventional methods tells us something, however, it cannot be accurately used to create optimal nutrient ratios for the unique requirements of modern crops grown indoors.
* For optimal results, crop formulas need to be created specifically for the type of crop being grown and the types of conditions it is being grown under; what’s optimal for one type of plant will not be optimal for another. One size does not fit all. However, nutrient components may be tailored by savvy growers to create the optimal profile for their particular plant type; provided that the grower knows what those ratios are.
* The optimal nutrient ratios change slightly through different crop developmental phases such as in the seedling/cutting phase versus the vegetative growth phase versus the bloom phase. It’s important to know what these changes are and to have them reflected in the crop feeding schedule.
In the end, most growers are putting a lot of trust in the manufacturer of their chosen nutrients. This is all well and good, as your success as a grower will be their success as a manufacturer. However, have you really stopped to think and ask: what exactly do they know, and where have they gotten their information from? Sure, if the plant is supplied the 13 major essential elements it requires it will live and grow. If the ratios of these elements are supplied at the correct times and mirror the plants demand for those nutrients and in those ratios, the plants can grow at optimal levels. It’s possible that many of us who have harvested very healthy and seemingly large yielding indoor crops were not in fact harvesting the optimal crop, leaving much more room for improvement than we may have realized. Just to back this point up a bit, consider 10 years ago that the majority of indoor growers were yielding ½ of what they can yield today, in the same space, using the same amount of electricity. Yes, of course there are exceptions, although that does appear to be the rule of thumb.
So, why the improvement? There are several reasons, including plant genetics. However, a large part of this increase can be attributed to nutrient formulations and grow gear that have started to evolve to specifically address artificial and intensive modern growing environments and the types of plants that people like to grow in them. This article is here to state that there is still much more to be done in the way of research and improvements in nutrient formulations that are intended for intensive artificial growing environments and the new breed of plants being grown in them. Products that have been developed through research on modern indoor crops are now available to indoor growers, while some growers continue to use out-dated technologies to achieve moderate harvests.
Now that’s a bold statement. Well, here’s a little dose of proof:
Ask an experienced grower what the most important crop element is in the bloom phase, and the vast majority of the time you will hear phosphorous, which is the “P” in “N-P-K”. Yes, phosphorous is important, now asking the grower a follow-up question along the lines of “why is that the most important element?” Chances are you will hear, “because it’s used the most in the bloom phase.”
Wrong. Due to archaic field crop research crossed over into nutrient formulations intended for modern high producing indoor crops, there are some really huge misconceptions about what is optimal for nutrient ratios in the bloom phase for indoor crops grown in artificial environments. The simplest way to illustrate this fact is to look at one of the most popular types of products in the hydroponics industry, and that’s the “bloom booster.”
The majority of bloom boosters contain very high levels of phosphorous and moderate to lower amounts of potassium. They may also contain other macro and micro elements including magnesium, sulfur and iron. Growers begin to apply these types of products through the early bloom phase and late into flowering prior to “flushing” the crop before harvest. There seems to be a general consensus that the modern indoor containerized (or “systemized,” if you prefer) plant in the bloom phase needs abundant amounts of phosphorous relative to other nutrients. Well the truth is that they do not, because:
1. Phosphorous is highly available to containerized or systemized plants grown indoors relative to outdoor conditions where it is quickly leeched away from the root zone via mass flow.
2. When examining analytical reports charting the nutrient profile of a high yielding indoor crop at harvest (plant tissue analysis) it becomes clear that even in a variety of strains within the same plant type, that the plant requires nearly five times more each nitrogen and potassium relative to phosphorous.
For example, if the plants elemental profile at harvest time was analyzed to reveal that healthy yields consisted primarily of nitrogen, potassium and calcium relative to phosphorous, why then are growers applying so much phosphorous (relative to other nutrient elements) in the bloom phase, and more importantly, what effect is this over abundance of phosphorous having on crops?
To answer the first part of the question, as indoor growers we are applying too much phosphorous because the recommendations for applications and formulations have been based on outdoor field agriculture practices, which simply don’t apply directly to indoor gardens. In nature the soil is very deep, and roots do not occupy the entire body of soil as they do in containers, beds or systems found with indoor gardens. Phosphorous leeches from the root zone in natural soils quickly, washing away from the contact zone with plant roots, as it drains with water further into the depths of the earth. To ensure a healthy supply of phosphorous, outdoor conventional field agricultural growers do a sort of “over-application” of phosphorous, because it has been determined that much of it will be quickly leeched away from the plant roots; what remains at any given time can be taken up by the crop. From this, we can learn that excessive “P” values in our N-P-Ks are not necessary for indoor growers, where phosphorous maintains a high level of contact within the root zone of plants grown in artificial soils and in containers, beds and systems commonly found with intensive indoor growing environments.
Now what affects can excessive phosphorous levels have on crops? Firstly, excessive levels of phosphorous can create nutrient imbalances in the root zone, and consequently inside the plant. This creates a form of stress in the plant which can diminish yield potential and increase the plant’s susceptibility to problems such as insects and diseases. Conversely, it can also be said that a slight stress induction from excess phosphorous may have some benefits in the late bloom/ripening phase as the plants reach maturity. However, creating this stress from early in the bloom phase and continuing it throughout will not create the correct nutrient profile for optimal harvest potential. This is not to say that growers should not supply phosphorous throughout the bloom phase, although it is to say that grower’s crops will yield larger harvests if phosphorus is supplied in the correct and balanced ratios with other nutrients, as determined through careful tissue analysis of indoor crops versus conventional field agricultural data.
In simple terms, based on the macro and micro nutrient profile analysis of a healthy, high yielding indoor crop (plant tissue analysis) growers have some options with how best to address the nutritional requirements of their favorite crop to get bigger yields than they have ever been able to achieve before.
Firstly, don’t apply bloom boosters with high phosphorous to potassium ratios continually through the bloom phase. For the first week of flowering to help trigger the natural plant stresses that amplify the plant’s flowering process, it’s okay to give the crop a dose of bloom boosters that have higher P to K ratios in the NPK values stated on the label. Usually, these types of bloom boosters that are formulated for indoor crops at the onset of flowering will also have other components in the formulation that help to control vertical growth; stacking internodes and flowering sites tighter together for each foot of vertical growth to give maximum yields.
After the first week of flowering where a “trigger” bloom booster maybe used to help ignite the bloom phase, you may begin to apply a balanced P:K bloom booster in conjunction with a balanced base nutrient program. If you have gleamed anything from this article, you will be wondering what the appropriate P:K ratio would be for indoor flowering crops, and current research has been demonstrating that a 1:2 ratio seems to work best, the polar opposite of some of the bloom boosters currently being used by indoor growers. To build the biggest and heaviest flowers and fruits, bloom boosters should supply more than just the correct P:K ratios. Additions of L-amino acids and other forms of reduced nitrogen will further amplify and enhance the plant’s natural reproductive response, leading to bigger and heavier harvests of higher quality. Magnesium and sulfur are also very important components in the bloom process of most indoor crops.
In the late flowering phase, when the plant is ripening, and in some instances producing elevated levels of essential oils, a slight “spike” in phosphorous levels will induce a level of stress that can help to enhance crop quality. For example, this is when a 2:1 P:K ratio may be appropriate. Note that at this time, the plant is not developing structurally anymore. All crops should be sufficiently flushed of excess nutrients, beginning at least one week before the anticipated date of harvest. This is accomplished by applying a leeching agent to the growing medium or system and then running straight water possibly with digestive enzymes and/or humates for the final days before harvest.
Three part base nutrient systems have been widely used and accepted through the indoor gardening community, and have been delivering great results for years. Based on modern research conducted on indoor grown high yielding crops, it was determined that using the three part nutrient system actually produced better results when being applied in a 1:1:1 ratio versus the common 3:2:1 ratio, especially when bloom boosters intended for indoor crops were used in conjunction with the three part nutrient system. 2:1 ratios of three part base nutrients were the least effective of all (where the “grow” component was omitted entirely through the bloom phase).
Upon analyzing the nutrient levels and ratios achieved in the nutrient solution for feeding indoor crops in the bloom phase, applying the base nutrients in a 1:1:1 ratio using popular three part nutrient components, the level and ratios much more closely resembled those of the internal nutrient levels and ratios of the plant being grown versus using the three part nutrient components in the common 3:2:1 method.
After all is said and done, there is only really one way to find out what is going to give you the biggest and best quality harvests, and that’s to experiment a little. If anything, it’s the hope of this article that you will begin to question where the nutrient values you are using having been derived from, and if they are in fact correct for your modern indoor crop. You just may find that by tinkering with the products you are already using or better yet, by adopting more modern formulations, that you are able to surpass even your largest yield expectations. So, if in the last decade we have been able to nearly double yields through research and experimentation on indoor crops, just imagine the types of harvest we may have in another 10 years. This advancement cannot continue, however, without growers who are willing to push the limits and boundaries of what is held as the “common truth” of the times, because more often than not, it won’t remain “the truth” forever.
