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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June 12, 2008

Understanding Plant Nutrition: Irrigation Water Alkalinity & pH

Water quality is a key factor affecting pH and nutritional management in container-grown crops. Understanding a few technical details about water quality will help you improve nutrient management appropriate for your own greenhouse. In this article, we will discuss the difference between water pH and alkalinity. We will also discuss how to interpret water pH and alkalinity results, and adjust your pH management strategies accordingly.  pH And Alkalinity Are Two Different Aspects Of Water Quality The term pH is a direct measurement of the balance between acidic hydrogen ions (H+) and basic hydroxide ions (OH-), and can be measured with a pH meter. The pH of a solution can range between 0 (very acidic) and 14 (very basic). At a pH of 7.0, the concentrations of H+ and OH- are equal, and the solution is said to be neutral. When the pH is above 7.0, the concentration of OH- is higher […]

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June 12, 2008

Feeding The Global Market

As senior vice president of Scotts Professional Global with a home base in The Netherlands, Fred Bosch keeps an eye on the North American market, as well as those in Europe and Africa. Bosch has seen the global view from that role for slightly less than a year and shares his views of the global market.  Feeding A Different Consumer Market At the consumer level, the big difference between the United States and Europe in selling plants and flowers is that Europe is more complex from a business perspective, Bosch says. With all the different countries and cultural backgrounds of European consumers, marketing efforts need to target different audiences in different ways, a need that isn’t as great in the United States. The types of gardeners found in the States are different that those found in Europe. “In southern Europe, most people live in apartments, so they don’t even have […]

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June 11, 2008

Understanding Plant Nutrition: Nutrient Sources: Media Cation Exchange Capacity

Figure 1. Examples of how cation exchange capacity buffers media pH and nutrient concentrations. (A) is an example of an acidic sphagnum peat particle. The peat particle contains several negative charges (exchanged sites) at the surface. In unlimed peat, these exchange sites are usually filled with hydrogen ions. (B) is an example of the same peat after the application of some limestone. The CO3-2 of the limestone has neutralized most of the hydrogen ions in the soil solution as well as at the exchange sites, causing the pH to increase. Some of the calcium and magnesium (both cations) from the neutralized lime are attracted to the exchange sites. (C) is an example of the same limed peat, but after the application of an acidic fertilizer. The acidic fertilizer has produced excess hydrogen ions. If these hydrogen ions remained in solution, then the solution pH would be reduced. In this case, […]

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June 11, 2008

Feeding Hardy Mums

Hardy mums and other fall crops are grown in the summer months for late summer/fall sale, providing many growers with a second income stream during this period. These crops are unusual when compared to most greenhouse crops, as they are most often grown outside in field conditions with fewer environmental controls. This scenario is positive from an economic point of view. It can, however, result in some production challenges. Careful planning and implementation of a fertilizer program, combined with close observation, will ensure high-quality fall crops. Mums – as well as asters, ornamental cabbage and kale – are relatively heavy feeders. The mum plant canopy is primarily built during the vegetative stage of production (the first 1.5 months). If nutrients are lacking during this time, the mums will not achieve their full size or color potential. After flowers are formed, nutrient demand diminishes greatly. If you are using a water-soluble […]

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