Eija Lankinen

5 tips for beginners planning the fertilisation strategy for a soft fruit farm

When a decision is made on a farm to start cultivating berries in a tunnel or greenhouse and using growing media, one of the most important factors to consider is fertilization. When growing in containers, fertilization is done with irrigation. Usually, a technical expert will draw up a fertilization plan to guide the grower on how the fertilization should be carried out. In tunnel and greenhouse cultivation, fertilization can significantly affect the quantity and quality of the crop, so careful planning of irrigation and fertilization must be done. Next, I will cover five factors that need to be considered during the design phase.

1. Quality of irrigation water

Before planning fertilization, the quality of the irrigation water must be determined. There may be several options on the farm from where to get the irrigation water. A water analysis should be taken from all possible water sources. The analysis determines the conductivity, acidity, permanganate, alkalinity, or bicarbonate of the water as well as the concentrations of various nutrients.

All of these factors influence the design of a fertilizer recipe. The bicarbonate concentration tells you how much acid can or should be added to the irrigation water to keep the pH at the right level. For example, when sodium (Na) is abundant in nutrients, it can accumulate in the substrate during cultivation. This negatively affects plant growth.

It is important that the analysis is done thoroughly, because, not all types of water analyses provide all the necessary information.

2.  Automation of irrigation and fertigation

When growing in containers irrigation and fertigation need to be combined. Automation is essential because nutrient-infused irrigation water should be given via short irrigations of even amounts of liquid multiple times. Often even dozens of times a day.

Irrigation and fertilization are done according to the weather conditions and the growth stage of the plant. It is often asked whether it is better to use drippers or drip lines. Both irrigation techniques can be seen on the farms. Drippers are usually more accurate, as the same number of drops is obtained in each container. The number of drip holes in the dripper hose can vary, making irrigation and fertilization inaccurate.

The fertilizers are mixed into a stock solution tank, from which the correct amount is dispensed via more or less sophisticated automation. The costs of automation technologies vary a lot. Personally, I recommend thinking of an irrigation and fertilization system as a long-term investment. It is worth finding out in advance what kind of product support for automation will be available in the coming years as well. When planning the fertigation strategy, it is also necessary to take into account which stock solution tanks are used and how many tanks can be used.

Due to the risk of sedimentation, certain fertilizer raw materials must not be mixed, so it is important to follow the recipe prepared by a fertilizer expert. Possible clogging of drippers or drip holes must also be monitored during the growing season.

3. Plant species and varieties

Different plants have different nutrient needs. Different varieties of the same plant species also have different nutrient requirements. When starting to design a fertilizer recipe with an expert, you need to go through what plants and varieties are coming to the farm for the next season.

Everbearing strawberry varieties are becoming increasingly common. When fertilizing them, it must be borne in mind that during harvesting periods, new flowers are also constantly evolving. Everbearing varieties need their own kind of fertilization. There are also differences in the nutrient requirements of short-day varieties.

Fertilization instructions come from the plant breeder, although it is worth considering the local environmental conditions. In addition to plant species and varieties, the growth stage of the plant must be taken into account. The need for nutrients and the need for irrigation vary at different stages of growth. If fertilization is to be done accurately, these requirements need to be taken into account when selecting the number of stock solution tanks. The right fertilizer recipe for the right plant and variety affects not only the number of berries you’ll be able to harvest, but also the quality, and ultimately the profitability of the entire crop.

4. EC levels and growing media

The type of substrate that is used greatly affects how irrigation and fertigation are carried out. For example, a mixture of peat and moss retains water and nutrients differently than a more permeable mixture containing coir. Peat and moss mixtures usually require a lower water and fertilizer consumption.

There are different types of peat that can be used in substrates. Coarse peat is more permeable than fine peat, so if necessary, overwatering the substrate is possible when the conductivity has become too high. The amount of substrate within each container also affects irrigation and thus fertigation. When filling containers, make sure that the filling quantity is approximately the same in each pot. Excessive compaction can take up more liters of the substrate than looser filling. We recommend watering growing media based on peat and moss according to the volume of the substrate. That means that the amount of substrate in the container is an important factor influencing the calculation.

The conductivity of the substrate tells you how many nutrients are available in the substrate. The conductivity of the substrate can be monitored on the farm using various types of EC meters. Often, pressurized liquid meters are more accurate than spike meters. Calibration of the meters is very important in order to draw the right conclusions. It is worth keeping in mind that the conductivity of the substrate does not tell what nutrients are in there.

More detailed analyses of the growing media and plant samples can be taken a few times during the growing season through various companies specializing in horticultural analyses. The nutrient uptake of the plant is also affected by other factors, such as humidity, so it is the grower’s job to make the conditions as optimal as possible for the plant to grow.

5. Plans for the future

The last things to consider when planning fertilization are your own plans for the future. If the size of the growing area is to be kept small, it’s possible to manage with less technology and less top-quality automation. If, on the other hand, there are already plans for an expansion in the next few years, it should be carefully considered what kind of automation with expansion options to choose. In addition, you need to think in advance about how much water is sufficient for your growing business.

On the other hand, if the area is small, it needs to be considered how many different varieties or plants to cultivate. For small amounts, it is impossible to achieve accurate fertilization. Fertilization will then have to be carried out according to the average nutrient requirements of the different varieties, and it is likely that fertilization will suit one variety better than another.

So before thinking about fertilizer offerings and recipes, be sure to go through these:

  • raw water analysis,
  • plant species and varieties,
  • what kind of fertigation system there is on the farm,
  • and how many stock solution tanks there are.

Contact your Kekkilä Professional distributor if you have any questions about our substrates or fertilizers!

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