Nutrient Limitation
Nutrients are essential for organisms to grow since they form part of many different biomolecules.
Photosynthetic organisms, specifically, need different nutrients to grow and flourish. Carbon, nitrogen, phosphorus, sulfur and potassium compounds are among the most important nutrients for photosynthetic organisms.
Normally, it is not easy to determine which nutrient is limiting organisms growth. Ideally, we would monitor the concentration of the main nutrients in the soil and analyze if there is a limitation in the supply of any of them.
To analyze whether the organisms are limited by any of the nutrients it is important to focus on any trends. If any of the nutrients decrease constantly over time and reach very low concentrations while the rest of them maintain their concentration and/or experience no decrease, then probably the organisms will be limited by the first.
If it is determined that the organism is limited by one nutrient in particular, one possible solution is to use a fertilizer that is enriched in the limiting nutrient.