How do you approach fertilizing your crops? In response to this question, the number of answers is only limited to the number of people answering the question. Regardless of the fertilizer source used to provide mineral nutrients to your crops, fertilizer delivery falls into one of two approaches: 1) pre-plant; or 2) post-plant.

As the name implies, pre-plant fertilization programs are initiated prior to planting crops. One of the most ubiquitous forms of pre-plant fertilization comes in the form of a “starter charge” in your growing substrate. This starter charge is a small amount of fertilizer that is intended to provide nutrients to the crop immediately following planting for a short period of time. Depending on the length of the production schedule, other fertilizers can be added to provide all or most of the crop needs such as calcium nitrate, potassium nitrate, triple superphosphate and magnesium sulfate for primary and secondary macronutrients, and fritted micronutrients for trace elements, though this approach is used less frequently now. The most widely used fertilizers for pre-plant fertilization are controlled-release fertilizers (CRFs). Typically incorporated into substrate prior to planting (Fig. 1), CRFs meter out nutrients slowly throughout production, and their release rate is primarily governed by substrate temperature.

The biggest benefit of utilizing a pre-plant approach to fertilization is the potential to simplify managing mineral nutrition for your crops. There are a myriad of things you need to manage while growing your crops, and by providing your plants with their mineral nutrients before planting, you can check one more thing off your list. I like to refer to it as “crock pot fertilization”— set it and forget it (of course this is an oversimplification, but hopefully you get the gist). However, there are challenges with pre-plant fertilization as well. Fertilizers are provided at the start of a crop cycle and, as we all know, no two seasons are the same. While more fertilizer can be provided to plants one way or another, you cannot remove fertilizer from the substrate when it is incorporated before planting.

Post-plant fertilization programs are initiated after plants are transplanted. The primary method of applying fertilizers after crops are planted is using water-soluble fertilizers (WSF). The variety in WSF allows growers to have any number of different formulations at their fingertips, like a painter with a wide palate of colors to choose from. Whether you are looking for a fertilizer to raise or lower pH, one with extra calcium or micronutrients, one for cool or warm weather, there is a good chance there is a WSF for you. Some growers have multiple fertilizer lines, each dedicated to a specific fertilizer (Fig. 2, top). However, since fertilizer injectors are widely used and are flexible, changing between fertilizers using a single injector is easy (Fig. 2, bottom). Controlled-release fertilizers may be applied to crops after planting, but this practice should be discouraged unless absolutely necessary. It is not that CRFs are an inappropriate fertilizer to apply after planting; rather, top-dressing is the only approach to applying CRFs post-planting and is a labor-intensive task that should be avoided when possible to minimize additional costs.

The primary benefit of post-plant fertilization programs with WSF is flexibility: You can respond to greenhouse conditions and crop growth differently with each application. The drawback is that this more dynamic approach to fertilization requires more diligence as a grower, in that you need to determine what to provide your plants as the greenhouse environment and crop growth changes.

Up until this point, I have approached fertilization as a binomial decision, choosing either pre- or post-plant strategies. However, this is a false dichotomy; you can use a combination of both pre- and post-plant fertilization approaches to keep your crops fertilized and healthy throughout production. For example, a smaller amount of CRF such as one or two pounds could be added to each cubic yard of substrate; then, after planting your crops, a WSF at a low concentration like 50 ppm N could be used. This approach of “splitting the difference” between CRF and WSF has the advantage of providing a base-level amount of fertilizer consistently with the CRF, supplementing with WSF with irrigation when the substrate is dry due to water uptake by plants and/or environmental conditions that are conducive to plant growth such as warm temperatures and bright light.

This “split” approach of using both CRF and WSF can also help accommodate species-specific fertilizer requirements for crops grown in the same environment and irrigated from the same source. Let’s use the example of a greenhouse section that has a mix of crops with low and high nutrient requirements. The heavy-feeding crop could be planted in a substrate with pre-plant additions of CRF and the light feeding crop could be planted in a substrate with no CRF, and both could be irrigated with a solution containing WSF; the CRF and WSF together could provide adequate nutrients to the heavy-feeding crop, while the WSF alone would suffice for the light-feeding crop.

Pre- and post-planting fertilizer programs have their own advantages and disadvantages. Each of the approaches appeals to different growers, and a combination of both can be used during production. Take some time this spring to evaluate if your current approach to fertilization is working for you and your crops, as there may be an opportunity to make changes that can benefit both.

Christopher is an assistant professor of horticulture in the Department of Horticulture at Iowa State University. ccurrey@iastate.edu

Biological control is a plant protection strategy that involves purchasing (from a distributor or supplier), and subsequently releasing or applying biological control agents or natural enemies (parasitoids, predators, entomopathogenic nematodes, or entomopathogenic fungi/bacteria) into a greenhouse in order to regulate existing insect and/or mite pest populations. Biological control is a preventative approach in managing insect and/or mite pests, which is somewhat different than the use of insecticides or miticides. For instance, in some cases, natural enemies are released prior to noticing insect or mite pests because once extensive pest populations are present and have become established — it is generally too late to use biological control.

There are a number of factors that can result in a biological control program failing to provide sufficient regulation of insect and mite pests. This article will address five factors including: 1) not implementing a reliable scouting program; 2) not conducting a quality assessment of purchased natural enemies; 3) not releasing enough natural enemies; 4) releasing natural enemies too late; and 5) applying pesticides that directly or indirectly affect natural enemies.

1. Not implementing a reliable scouting program

Since biological control is a preventative approach, it is important to develop a scouting/monitoring program that will allow you to determine the population dynamics (the relationship between pest populations and the environmental factors that may influence populations) and track trends in pest numbers during the growing season. Scouting/monitoring will result in more efficient timing of natural enemy releases. However, when releasing parasitoids, remove any yellow sticky cards for at least one week, as adult parasitoids are attracted to and will be captured on the yellow sticky cards.

2. Not conducting a quality assessment of purchased natural enemies

Quality assessment is essential in implementing a successful biological control program. The success of a biological control program is contingent on receiving functional natural enemies that are capable of locating and killing targeted hosts (prey). Shipments of natural enemies — both parasitoids and predators — should be stored for a minimal period of time upon receipt (no more than three days) so as to avoid any negative effects on fitness and foraging ability, which can impact the effectiveness of natural enemies in regulating pest populations. Therefore, in most cases, natural enemies should be released immediately upon receipt.

In addition, prior to release, always check to make certain that natural enemies are alive. For example, for predatory mites (e.g. Phytoseiulus persimilis) that are shipped in containers consisting of vermiculite or bran carriers, a small amount of the carrier can be placed on a white sheet of paper [8.5 x 11.0 inches (22.0 x 28.0 cm)], checked with a 10X hand-lens or if available, a dissecting microscope to determine if the predatory mites are active or not.

Parasitoids that are shipped as “parasitized pupae” or “mummied aphids” can be evaluated using a different method. For instance, whitefly parasitoids such as; Encarsia formosa and Eretmocerus eremicus that are shipped on release cards containing parasitized whitefly pupae or aphid parasitoids (Aphidius colemani and Aphidius ervi) shipped as “mummified aphids” in plastic containers can be assessed by placing a sample release card (for whitefly parasitoids) or small sample of carrier with “mummified aphids” (for aphid parasitoids) inside a glass Mason jar with a lid. A section of a yellow sticky card [1.0 x 1.0 inch (2.5 x 2.5 cm)] can be affixed to the bottom of the lid. The Mason jar should be checked regularly to ensure that adults are emerging from the pupae or “mummified aphids.” The number of potential functional parasitoids that emerged from pupae or “mummified aphids” can be assessed afterward when all the parasitoids have died in the Mason jar.

3. Not releasing enough natural enemies

Do not be “cheap” when purchasing natural enemies. Always release a sufficient number to ensure regulation of existing insect and/or mite pest populations. Releasing too few natural enemies will likely result in poor regulation of pest populations and subsequent damage occurring to greenhouse-grown horticultural crops. Refer to Table 1 for release rates of specific natural enemies based on biological control supplier information.

4. Releasing natural enemies too late

Biological control is a preventative approach and, as such, natural enemies are typically released before extensive insect and/or mite pest populations have become established. Therefore, order natural enemies in advance to ensure that you receive shipments at least every other week, so that you will receive a consistent shipment of natural enemies early in the production cycle.

5. Applying pesticides that directly or indirectly affect natural enemies

Pesticides (insecticides, miticides and even fungicides) registered for use in greenhouse production systems may directly or indirectly influence the effectiveness of natural enemies, consequently leading to insufficient regulation of insect and/or mite pest populations. Direct effects are affiliated with acute mortality or survival (longevity), over a specified period of time, of the life stages of natural enemies including: egg, larva, nymph, pupa, or adult. Indirect effects involve inhibiting feeding behavior (for predators), negatively impacting parasitism (for parasitoids), decreasing female reproduction, diminishing prey availability, and reducing foraging behavior or mobility.

Any direct and/or indirect effects of pesticides on natural enemies may be influenced by the following factors: 1) product formulation, 2) application rate, 3) natural enemy type (parasitoid or predator) and species, 4) life stage exposed (egg, larva, nymph, pupa, or adult), and 5) environmental conditions (temperature, relative humidity, or photoperiod). In addition, biological parameters that may be indirectly affected are: host acceptance, foraging behavior, and reproduction. Therefore, it may be prudent to time applications prior to releasing natural enemies or after natural enemies have become established. Be sure to check pesticide labels for specific information regarding direct effects on natural enemies, or contact a university-based extension entomologist.

Raymond is a professor and extension specialist in horticultural entomology/plant protection in the Department of Entomology at Kansas State University. His research and extension program involves plant protection in greenhouses, nurseries, landscapes, conservatories and vegetables and fruits. rcloyd@ksu.edu or 785-532-4750

Low-cost growing structures are used by many growers for short-term production space or winter plant protection. These are not usually heated, but sometimes minimal heat is needed to keep the temperature above freezing.

The amount of heat needed can be approximated by the formula HL = A x U x ?T where:

• HL = Heat loss (Btu/hr)
• A = Surface area of structure (sq ft), U = U-value — heat loss factor (Btu/hr – sq ft-°F) — Use 1.25 for single layer glazing, 0.8 for double layer, or 0.7 for double wall polycarbonate.
• ?T = temperature difference between inside and outside (°F) on the coldest night.

The following discusses some of the options that growers must provide heat.

Hot air systems – Compared to water systems, air heating systems have the advantage of being low cost and easy to shut down when heat is no longer needed. Most have a blower that provides some heat distribution. Installing horizontal air flow (HAF) or perforated poly ducting can increase the uniformity of the heat in longer structures. A disadvantage to heated air systems is that very little heat gets down to the root zone in plants placed on the floor. Vented equipment should be selected to exhaust flue gases that may contain sulfur or ethylene. Because these heaters will have limited use, look for used equipment.

Unit heaters – These are available in many sizes to accommodate most protected areas. They are usually supported from the hoops or from a frame that gets them above the plants. The fuel source can be natural gas, propane or fuel oil. High efficiency condensing gas heaters (93 percent) are available but these may have problems with the condensate freezing in cold weather unless they are drained.

Floor furnaces – These furnaces are available in sizes from 50,000 to 500,000 Btu/hr that can be fired with fossil fuels. A model with a blower instead of a fan that is attached to perforated poly ducting works well for under bench heat.

Hot water systems – There are more options with water systems. The advantages include better distribution of heat with the resulting more uniform temperature. The disadvantages include generally more expensive equipment and the system may have to be drained or blown out if it is shut down during freezing weather.

Root zone heat – Locating the distribution system on benches, on the floor or buried underground will provide heat throughout the whole plant area. Heat sources can be low-cost domestic water heaters, in-line instantaneous water heaters or high-efficiency condensing boilers. An additional heat source may be needed on very cold nights as there is limited heat from the root zone. Storing the excess heat from a greenhouse heating system in an insulated heat storage tank during the day and then using this heated water at night may make an economical system.

A biomass-fired outdoor boiler could also provide hot water. A disadvantage is that it requires recharging late in the evening and early in the morning on cold nights. Distribution of heat could be low-output fin radiation, PEX or virgin black poly tubing or an EPDM tubing heat mat.

Heat exchangers – Water to air heat exchangers, available in many outputs, can provide heat distribution if you have a good supply of hot water. They are inexpensive compared to fossil-fired unit heaters. Location is important to get good heat distribution in low or narrow structures. Installing HAF fans can help to distribute the heat.

Low output aluminum fin radiation – This may be a good choice in cold frames or overwintering houses where a limited amount of heat is needed. Depending on the style, these have an output of 50 to 150 Btu/linear foot at 150-degrees °F water temperature. They need to be installed so that they can be drained or blown out if the system is shut down during cold weather.

Temperature control for this heating equipment should be accurate electronic thermostats located in the center of the growing area. If freezing temperature is the main concern, locate the thermostat just above plant height. Be sure that the structure is tight to reduce cold infiltration air. Place some max-min thermometers in the growing area to monitor temperature extremes.

John is an agricultural engineer, an emeritus extension professor at the University of Connecticut and a regular contributor to Greenhouse Management. He is an author, consultant and certified technical service provider doing greenhouse energy audits for USDA grant programs in New England. jbartok@rcn.com

Digital marketing is the advertising of choice for many growers these days. It simply requires a smart phone, an internet connection and someone familiar with using different digital platforms. The best part: It is free to use.

“In our situation, we believe the most effective and most cost-efficient means of targeting our audience is through digital marketing,” says Tim Moore, director of sales and marketing at Lucas Greenhouses, a wholesale-only operation in southern New Jersey.

Leigh Ann Centeno, sales manager at Parks Brothers, a large grower-retailer operation in Van Buren, Arkansas, echoed Moore’s sentiments.

“We have found that it works better than any other media — newspaper or radio — to attract our customers,” she says.

Choose your platform

Companies must experiment to discover which social media platforms or channels work best for them. Parks Brothers mostly utilizes Facebook, posting photos and pertinent articles to customers who come into their own garden center. They’ve also dabbled with Instagram and Pinterest.

Much of their digital marketing is targeted at potential customers for their garden center, where they sell annuals, perennials and poinsettias. Although Parks uses Facebook to attract customers to their retail store, they’ve found that they’ve inadvertently picked up a few wholesale accounts from Facebook.

“We get a lot of followers and some of those turn out to be full-time customers,” says Centeno. “They’ll ask questions and I’ll direct them to call the office for more information.”

“A lot of times, we’ll video people planting in the seed houses,” Centeno explains. “My mother likes to build interest in the wintertime, so she’ll go out and take video of them planting seed and transplanting to the greenhouses.” She said her niece targets potential wholesale customers by posting pictures of their products to Instagram.

Lucas Greenhouses is using social media platforms strictly for garnering leads for their wholesale operation. They’ve been utilizing Facebook, Instagram and YouTube, and may give Snapchat a try.

YouTube is an important part of the mix at Lucas Greenhouses, where staff posts a video once a week during the spring season. The video accompanies a plant availability list and is used to highlight certain crops and show customers what’s available, Moore says.

He says they’ve recently added customer testimonials to their website and social media channels.

“That is where our marketing focus will be in the coming year as we look to connect potential customers with the experiences of our current customers,” Moore says. All of the marketing efforts at Lucas Greenhouses are aimed at directing people back to the company website.

Moore adds that you must identify the best digital avenues or platforms for your company, not just the ones that appeal to you. It’s also okay that not all of their Facebook followers are potential customers.

“We believe anything that is promoting what our industry can bring to homes and gardens is beneficial to all of us in the industry,” Moore says.

Assign someone to the task

Parks Brothers is a third-generation family business, and will soon include a fourth generation when Centeno’s son completes his horticulture degree and jumps on board. Centeno’s mother, Claudette Parks, runs the garden center business and also does much of the social media marketing, taking photos daily with her iPhone and iPad and uploading them to Facebook. The arrangement has worked well for this company, which swore off selling to big-box stores several years ago to focus on independent garden centers. They’re currently the largest greenhouse plant wholesaler in Arkansas.

“My mother does a lot of the posting, what’s current at Parks” says Centeno. “She has the most time to do that but all of us, including myself and Jason Parks, do it.”

Moore says they designate people to different digital marketing tasks. The Facebook and Instagram accounts are managed by Corey Goetsch, who collaborates with Danielle Fleming on video and the website.

Still, some companies might be hesitant or intimidated by the technology or perhaps just confused over the myriad of choices available to market digitally.

“If you are new to digital marketing, or don’t feel like you are social media-savvy, ask for help from the younger generation,” Centeno says. “They are social media experts. Try to focus on posting pictures of product, any new items, special events, new arrivals, etc. to generate excitement with your followers and bring in traffic.”

Consistency is the key

Both companies understand the importance of posting consistently to different platforms to keep their customers informed of current offerings while keeping them engaged with the company.

“We put together a list each week on what we want to focus on for the video for our customers; Corey does a lot of photography that we will intertwine with that,” Moore says. Lucas Greenhouses also posts a steady stream of photos throughout the growing season on Facebook and Instagram.

Parks posts daily, highlighting new products and what’s currently on sale. Centeno, who says their posts have reached more than 11,000 potential customers, receives comments almost daily, which they do their best to answer.

“I believe that when using social media, it is important to post regularly — at least once daily,” she says.

Measure results

Targeting your market and measuring the results of your digital marketing activity will ensure that you’re investing your time in a way that will provide the biggest ROI. Both companies can do this by monitoring web traffic to their websites as well as using the tools provided by these social media platforms.

“Whatever avenues you focus on, make sure you can measure success,” Moore advises. “If not, then you are really just throwing spaghetti against a wall hoping some of it sticks. We live in a digital world now. Most potential customers are going to visit you virtually before you ever see them in person. We want our customers out in front telling their story and how Lucas Greenhouses has been a vital part of it.”

“The beauty of social media is the ability to advertise your product through images,” says Centeno. “Who doesn’t want to see how beautiful your Wave petunias are on Facebook or Instagram before coming out to shop?”

Neil is a horticulturist and freelance writer and copywriter for the green industry. greenindustrywriter.com