June 20, 2008

Managing Nutrition In Spring Crops

The spring season presents some unique challenges for even the best growers. It can be a time of rapidly changing environmental conditions – some beyond the grower’s control – that may negatively impact crop quality. Often, growers plan multiple crop turns to meet desired shipping dates that are subject to last minute shifts due to fluctuating weather and market conditions. Plus, there are hundreds of different spring crops available, making even more it difficult to stay on top of their various nutritional needs. To further complicate matters, this enormous list of spring crops continues to expand every day. Managing the nutrition of spring crops can be compared to running a diner with a gigantic menu that includes various eclectic offerings from Italian to Chinese. I’ve often wondered how the cooks in those establishments are able to efficiently supply such a wide variety of meals on demand at a relatively low cost. […]

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June 19, 2008

Q&A On Controlled-Release

Pilon: What are the methods controlled-release fertilizers (CRF) are applied? Passchier: The two most common methods of applying controlled-release fertilizers in greenhouses and nurseries is to incorporate them into growing mixes prior to planting (incorporation) or placing the fertilizer on top of the potting substrate (topdressing). Topdressing entails placing a predetermined amount of fertilizer on top of the growing medium of each container. Generally, topdressing is reserved for second-season crops, but there are some growers who topdress crops just after planting new liners. Care should be taken with this practice to make sure you have a first-season fertilizer and not a second-season topdress fertilizer. The first method I was exposed to 15 years ago was the "big hand" method. The grower/owner would show the hired help how much fertilizer to put in their hands and then place it on the surface of the container. Needless to say, the size of […]

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June 18, 2008

Misconceptions About Controlled—Release Fertilizers

Delivering and managing nutrition is one of the primary tasks associated with producing greenhouse crops. Most growers deliver nutrients using various water-soluble fertilizers, some growers use controlled-release fertilizers (CRF), while others use a combination of controlled-release and water-soluble fertilizers. As I travel across the country to visit various growers, I’ve come to recognize that many growers would like to consider using controlled-release fertilizers at their facilities but do not understand these products well enough to implement them into their production systems. With a shift in irrigation and fertility practices, where growers must control leaching and water runoff from their production sites, the use of controlled release fertilizers will allow growers to produce high-quality crops and manage the nutrients that leave their production sites more effectively. From my perspective, there is a great need to educate growers of the benefits and risks associated with the use of controlled release technology. To help […]

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June 18, 2008

What’s In Controlled-Release?

In the first installment of this four-part series, we began to introduce several important aspects regarding controlled release fertilizers (CRFs). Slow-release fertilizers are reacted urea formaldehyde products. Each has its own characteristic chain of polymers, which are gradually broken off by microbial activity and then made available for roots to uptake. Controlled-release fertilizers are fertilizers with nutrients that are encapsulated or coated, similar to an M&M candy, where there is an outer candy coating and the good stuff inside the coating. Fertilizer is released when moisture is drawn into the covered coated prill and turns the fertilizer salt into a semi-soluble form. The release of nutrients from the prill varies slightly with the technology used to formulate the coating. All CRFs typically have either a resin or polymer coating. The main difference is how the water soluble fertilizer comes out of the prill. The rate of release is often a function […]

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June 18, 2008

Talking Temperature

Pilon: How does temperature affect release? Passchier: As we discussed previously (see the July 2007 issue), controlled release fertilizers can be compared to M&M candy since the good stuff is inside of the coating of each of these products. As the temperature increases so does the solubility of the candy and fertilizer on the inside. The main difference is the inside of the coated prill of the fertilizer contains some form of salt. Moisture needs to be present around the coated fertilizer prill in order for moisture to be drawn inside allowing the solid fertilizer salt to turn into a semi-soluble state. As the temperature increases, so does the solubility and the pressure inside the prill. Consequently, with higher temperatures and increased internal pressure, it requires less time for the fertilizer to come out of the prill and be available for plant uptake. The trick to formulating and using CRFs […]

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June 18, 2008

Fertilizing Containers

After water management, fertilization is the next most common problem with keeping large containerized plants alive through the summer. Most consumers do not fertilize their plants, or if they do, they don’t apply a sufficient amount to maintain the plants at good quality. In this article, we give specific recommendations about fertilizing of 10-inch baskets. For larger size pots and baskets, use these recommendations as a starting point for suggesting fertilizer rates. How much fertilizer does a 10-inch basket need? Assuming you start with a growing medium that contains preplant fertilizers, an additional 1.5 to 2 grams of nitrogen from a balanced fertilizer is sufficient to produce a 10-inch basket in 12 weeks with no leaching. That is equivalent to the application of 7 to 10 quarts of fertilizer with a concentration of about 200 ppm N. If you leach, you will need to use more fertilizer. Researchers at Michigan […]

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June 17, 2008

Combination Fertilizer Programs

    There are several types of fertilizers commercially available to growers: water soluble fertilizers (WSFs) and controlled release fertilizers (CRFs). Historically, WSFs have been used mostly in greenhouse production while CRFs have been used mostly in nursery crops grown outdoors. Both types of fertilizers offer advantages and disadvantages depending on the application. WSFs are dissolved in water and drenched into the growing media. They provide an immediately available dose of nutrients to the crop and offer great flexibility. A grower can vary the timing, concentration or type of fertilizer formulation applied at any fertigation. Since any single application does not persist for very long in the root zone, WSFs must be continuously applied to provide the crop with adequate nutrients. This can be labor intensive and crop problems can arise unless careful monitoring and application adjustments are made. Also, WSFs can only be applied when crops need to be irrigated […]

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June 16, 2008

Troubleshooting Your Spring Crops

Growing media pH impacts nutrient uptake and utilization. Pictured is an example of high pH, low micronutrients on the left. Spring is a very busy time for most greenhouse growers. Multiple activities are taking place simultaneously: potting, shipping, merchandising, spacing, growing, monitoring crop quality, spraying, etc. Weather is ever-changing and can throw a monkey wrench into even the best of scheduling plans. With the soaring cost of heating fuel, growers are trying to pack more plants into their growing spaces. In northern climates, growers are waiting longer to start their crops, further compressing the spring growing season. Consumer demands dictating the need for crop diversity also continue to increase, presenting the grower with a multitude of diverse nutrient requirements in the same operation, taxing injector and plumbing setups. Combination containers can result in plants with different nutrient requirements being grown in the same pot. It is easy to see how […]

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June 16, 2008

Understanding Plant Nutrition: Limestone and pH

In last month’s article, we stated that cation exchange capacity (CEC) does not play an important role in pH, calcium and magnesium buffering. The question should then be asked: Is growing in a soilless media similar to hydroponics when it comes to pH or nutritional management? Growing in a soilless root medium is not the same as growing with hydroponics because there are sources of buffering found in container media. One of the strongest buffers for long-term pH and nutritional management is limestone. In this article, we will focus on the effect limestone has on pH management by discussing why limestone needs to be added to a soilless media, and the difference between reactive and residual limestone.  Figure 1. Particle size distribution of 29 lime materials and reagent grade CaCO3. Dry sieving method was used for carbonate liming samples (calcitic: C1-8, dolomitic: D1-17 and reagent grade CaCO3: R), whereas wet […]

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June 16, 2008

Growing Green: Water Soluble’s Place In Sustainability

It is not often that you see the words “mineral fertilizer” and “sustainability” in the same sentence. Responsible use of nutrients in regards to fertilization should be one of the main factors you consider when evaluating how your operation can become more sustainable. Is organic the only way to go or are there other solutions in regards to fertility? When overall plant quality is a concern in potted plant production, is it feasible to produce your best plant material without the control that typical mineral-water-soluble fertilizers provide? Mineral fertilizers have played a huge part in the construction of what our horticulture industry is today. In the early part of the 1950s, greenhouses were popping up all over our country as the love of gardening moved out of the farm and into suburbia. Home consumers searched for attractive flowers to beautify their homes in expansive flower beds. The commercial greenhouse grower […]

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June 12, 2008

Understanding Plant Nutrition: Irrigation Water As A Nutrient Source

Nutrient concentration varies dramatically between greenhouse operations (Table 1), and it has a major effect on your choice of fertilizer. Irrigation water rarely contains high enough concentrations of the primary macronutrients (nitrogen, phosphorus or potassium) to be considered significant for plant growth. However, water can contain significant concentrations of the secondary macronutrients calcium (Ca), magnesium (Mg) and sulfur (S) and micronutrients such as boron (B). The nutrients supplied to a crop are a combination of several sources, including the irrigation water, acid and chemical fertilizers. For example, it is more important to select a fertilizer that contains calcium and magnesium if your irrigation water already contains 10 ppm Ca and 2 ppm Mg than if your water contains 75 ppm Ca and 30 ppm Mg.  Acidifying Water Can Add Further Nutrients Adding mineral acids to the irrigation water to neutralize alkalinity can also add nutrients. Sulfuric acid (H2SO4), phosphoric acid […]

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June 12, 2008

Understanding Plant Nutrition: An Introduction

Understanding nutrient management can help you prevent both crop quality and environmental problems. When nutrient imbalances arise, deficiencies or toxicities affect plant quality and profitability. The use of high fertilizer concentrations (300 to 400 ppm N) combined with heavy leaching is no longer environmentally acceptable because of the potential runoff of fertilizers, chemicals and water resources. Our goal in this series is to help you make informed decisions about the nutritional program you use to grow the crop. We will explain how different management factors influence plant nutrition, how to develop an overall fertilizer strategy that minimizes risk and outline actions you can take to recognize and correct common nutritional problems. In this first article, we describe the essential nutrients for plant growth. These nutrients must be provided from some source (such as fertilizers, media components or irrigation water) for healthy plant growth. Future articles will expand on each of […]

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