In order to obtain this potential the environmental conditions must be perfect, which very rarely happen. Apart from the environment, several agronomic factors influence the crop yield, such as soil plowing, pests and diseases control, planting system, physical and chemical soil properties. Plant nutrition is an essential factor to obtain high yields.
The seed no. is directly influenced by the number of nodes per plant, and the pods developing at these nodes. The most sensitive stage development of pods is between R1 and R6, when the flowering and flower abscission occur.
The number of nodes/plant is also influenced by the plant density (plants/m²), the number of seeds/pod can hardly be influenced by agricultural practices.
In conclusion, the main factor for yield development is a high number of nodes and pods on the plant, which can be reached by optimum plant growth.
The most required nutrients have specific functions to boost higher yields.
Soybeans have a large requirement for nitrogen, but can obtain the majority of this from the air via Rhizobium bacteria forming nodules on their root system. Soybean seed needs to be inoculated with group H rhizobia to get effective nodulation and ensure adequate nitrogen nutrition to the plant.
Phosphorus is particularly important for root development and for a good crop establishment.
Potassium, like nitrogen, also drives the crop development, and large amounts are taken up during plant development. Its supply needs to be balanced with N along the cycle. A good potassium nutrition can also help to minimize frost effects and avoid lodging. Potassium is important for stomata closure regulating and low supplies may result in water losses.
Magnesium, sulfur and iron increase the photosynthetic activity and maintain good growth. Calcium ensures good strengthening of cell walls, protecting roots, sheet and stems production. Boron is required for the pollen tube development and ensures good fruit set. Zinc is important for photosynthetic activity.
The unavailability of any other micronutrient can also restrict processes of growth and yield consequently therefore, a balanced crop nutrition strategy is key in achieving high yields.