Article 1-2 Efficient Nutrients
Gardeners can take advantage of their good growing conditions by supplying their crops with the right strength and the right formula of their nutrients as their crops grow. Use a good hydroponic nutrient designed for your grow medium - some fertilizers are mixed especially for soilless potting mixes, but they will not work well for crops growing in rockwool. Use green growth fertilizer mix until you shorten your light hours; then change to a flowering or crop production food.
With intense light levels, C02 enrichment, and good air movement already established in the garden, increasing food strength is worth considering. First, evaluate the growing conditions and the condition of the plants. If everything is going well ,and plants are in a period of active growth, increase food strength gradually while carefully watching crops for signs of stress. Since the green growth stage is so brief - usually only 10 to 14 days there isn't a lot of time to increase food strengths during this stage. Most growers are satisfied with reaching 'full strength' level (1400-1800 PPM) by the end of their green growth period.
During the "transition" period - after shortening the day length, but before flowers begin to show - excessive growth is unwanted, and many gardeners actually reduce the strength of their fertilizer until plants begin to show flowers. To avoid 'stretching' -long, thin shoots - growers may reduce the Nitrogen levels in their flowering formula until the flowers begin to appear.
Once plants are producing flowers, they are entering a period of active growth and increasing the strength of the nutrient mix can be very helpful. Do this carefully and gradually! Increase food strength by about 200 PPM, then watch crops closely to be sure they are able to adjust to the stronger mix. After a few days, if everything is going well, increase the strength of the nutrients again by the same amount. By carefully watching the plants to learn their reaction to the increased nutrient levels, growers can quickly learn what food strength is right for their plants and their garden.