How Growing Media and Greenhouse Sanitation Contribute to Crop Consistency
As part of a blog series on discussing common production issues and practical solutions, ONfloriculture looks at promoting disease control and crop uniformity, primarily through growing media selection and greenhouse sanitation practices.
Growing Media Selection
It’s tempting to have one potting mix for an entire operation. Having one mix saves time changing bales on the planting line, it’s less to store/organize, and alternate mixes can come at a higher price point.
One solution is to group crops based on their watering requirements and choose two or more mixes that work (depending on how many different plants a grower is producing). Making this change can help reduce incidences of disease (and shrink) and increase crop evenness.
Different plant species have varying requirements for drainage, moisture retention, and aeration, which means they need different media mixes to thrive. This decision is especially critical in crops, like kalanchoe, where growers typically stick a cutting directly into its finishing container.
To choose the right mix, there are two main questions to ask:
1. What are the media requirements for the crop that I’m growing?
To find the media requirements for a crop, consult with plant suppliers and crop production guides. Using Kalanchoe as an example, production guides (Syngenta) indicate that this plant is a succulent species requiring a fast-draining medium that’s high in organic matter. Typically, peat moss is the favorite choice among growers for the base mix. There are peat moss pre-mixes available with varying amounts of either organic (wood fiber) or inorganic (perlite, pumice, vermiculite, or sand) material that impact the drainage speed of the media.
2. What environmental influences are there in the production zone I’m growing in?
Determining how environmental factors in the growing zone influence water uptake — and consequently affect the media’s required water holding capacity — is complex and will likely need to be evaluated through in-house trials. For example, poly-covered greenhouses hold more heat and humidity than a glass-covered greenhouse. Under poly covering, the media is less likely to dry out due to reduced heat pipe activity and higher humidity levels, which also lower plant transpiration rates. As a result, plants grown in these conditions will require growing media with lower water-holding capacity compared to other environments. Other environmental factors to consider are fans, vents, gutter height, and growing location (i.e., flood floor vs. wire bench).
Greenhouse Sanitation Practices
Sanitizing the growing area between crops is one of the most important things to make a regular habit of in a production system. Skipping this step can affect the crop currently being grown, and may also lead to contaminating irrigation tanks when using recirculated feed water — potentially spreading disease to other crops irrigated from the same tank.
It’s also best practice to include sanitation measures during crop production (i.e., cleaning benches as they are emptied). Generally, this is widely adopted among growers. However, during the busy season, it can get pushed to the back burner and viewed as a non-necessary step when pressed for time.
If you’re pressed for time, at least do the bare minimum. A sweep of the growing area to remove any particulate matter, followed by a foaming disinfectant, will make a huge difference to help protect young plant material (and recycled feed water) from whatever was left behind from the last crop, whether it be pest or disease.
Once growers have more time and the zone is empty, more intensive sanitation should be followed. This includes not just sweeping particulate matter, but also making sure all organic matter is disposed of before adding in sanitizers, which will make them much more effective. Removing weeds that can harbor pests and diseases, and flushing irrigation systems, are also on the list.
In the case of Kalanchoe, phytophthora is the most common disease, and it can live in soil left behind on benches. In addition to living in soil, this disease is classified as a water mold, which means that it has the potential to spread through an irrigation system if left to recirculate. Sanitizing between crop cycles will give young plants the best chance of avoiding this common disease and may reduce the need for costly chemical fungicides later on.
For additional information and resources on picking the right growing media for crops and suggested changes to greenhouse sanitation protocols, please read the full article found on the ONfloriculture website.
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