In order to optimally control and monitor the development of your plants, it is essential to provide the right nutrient solution and to have it analyzed regularly (at least 1x every 4 weeks). This applies to 'conventional' greenhouse vegetable and ornamental cultivation, but also to medicinal and recreational cannabis. After all, cannabis is just a crop.
With nutrition you can steer a lot in the development of your plants. Not in the speed of flowering, which remains the same and depends on other factors such as genetics, 24-hour temperature, light intensity and dark time. But nutrition is one of the factors that influences the structure of your plants and flowers.
Understanding nutrient solution
In general, you can say that a nutrient solution, in terms of main elements, should look like this: give an EC of +/- 2.5 and a pH of 5.6 to 5.8. The Calcium in your nutrient solution should not exceed the Potassium. In addition, due to the strong antagonistic effect of Ammonium on Calcium, you should not exceed your Ammonium level too much - in any case, no higher than 1.5 mmol with an EC dose of 2.5. Otherwise the absorption of Calcium will be blocked too much, which will eventually increase the flowers sensitivity to Botrytis.
In order to avoid a too lush of a crop, it is also important that you do not give too much Nitrogen. A lush crop is more sensitive to Botrytis, but also more sensitive to mildew and spider mites and aphids. Therefore, do not only use Nitrate-containing fertilizers (eg Potassium Nitrate, Calcium Nitrate and Magnesium Nitrate), but also use sufficient Chlorine and Sulphate-containing fertilizers (Bitter Salt, Calcium Chloride and Potassium Sulphate). The ultimate aim is to achieve a Nitrate dose of a maximum of 12.0 mmol with an EC dose of 2.5.
"Delphy's experience shows that many cannabis companies quickly add too much Magnesium and Phosphate in the nutrient solution," the Delphy team explains. "Both can hinder the absorption of Calcium: Magnesium due to its antagonistic effect on Calcium; Phosphate because calcium phosphates precipitate in the substrate. This increases the flower sensitivity to Botrtyis."
A look at coco-peat substrate
If you use coco-peat as a substrate, have your coco-peat analyzed regularly to see if it has been washed properly. Poorly washed coco peat contains too little calcium bound to the coco peat and too much sodium and potassium. Because the cultivation of cannabis is a short cultivation, you no longer control this imbalance during cultivation and you make it extra difficult for yourself to grow a good quality product.
"Finally, in the autumn of 2021, as Delphy, we will start a knowledge center for the cultivation of cannabis in collaboration with several other parties in Bleiswijk," they point out. "Research is one of the spearheads. One of possible research topics will certainly be the influence of fertilization on the ingredients. Much is being written about this at the moment, but measuring = knowing."
In addition, Delphy will start this spring with an online training course in which fertilization is one of the main topics in addition to plant physiology, climate and pests and diseases. Requesting more information or registering for this training is already possible.