Growers have many options for fertilizing their crops, ranging from controlled-release fertilizers (CRFs) to water-soluble fertilizers (WSFs) or a combination of the two options. Optimizing fertilizer strategies to produce visually appealing plants while minimizing inputs is important. One source of plant-available nutrients that is commonly overlooked is pre-plant starter charges incorporated into the substrate at the time of mixing. Many commercially available substrates that are focused on the retail market advertise increased growth compared to their competitors. Often, this is a result of pre-plant fertilizer charges (both organic and non-organic) that are included in the substrate. However, how do these preplant charges impact the chemical properties of the substrate, and is a preplant charge needed for your spring transplant production system?
A pre-plant fertilizer charge is included during the manufacturing process, and it is intended to provide nutrients to the crop immediately following transplant for a short period. The composition of a preplant charge can be a variety of forms ranging from inorganic and organic granular nutrients to organic matter including compost. In contrast, post-plant fertilization is supplied by the grower after transplant. Post-plant fertilization programs can be implemented in many forms, ranging from water-soluble fertilizers to controlled-release or slow-release fertilizers. Additionally, growers can utilize a combination of these two strategies: a preplant fertilizer charge to help encourage plant growth initially, followed by post-plant fertilization. However, growers should test the chemical properties of their substrate to optimize their fertilization program if preplant charges are included. Matching your nitrogen (N) source for your desired plant characteristics is important, higher percentage nitrate fertilizers will produce more compact plants while fertilizers containing higher ammoniacial percentages will produce darker green more lush growth but with more stretch.
At NC State University we examined the effects of 10 different retail substrates' preplant charge on the substrate pH, EC, and plant growth without additional fertilizers for spring basil transplants. Growers should understand what nutrients are in their substrate so they can customize their fertility regime to optimize plant growth.
Read more at e-gro.org