I'm going to take a stab at this one- a real stab in the dark.

Hydro is different because there is such an excess of water and chemical components remain dissociated into their respective ions. Plus the water is supposed to be oxygenated by a bubble stone. RedOx chemistry is different.

In soil, especially cold, wet, nonporous soil, since there is not that water matrix plus there is too little oxygen, chemical components behave differently. That is why when you see pH problems in your soil-look at the FAQ to confirm this- most nutrient lockouts are exacerbated by poorly-draining soil.

I'm not familiar emough with the behavior of fertilizer component mixtures in water to really explain this properly.
stinkyattic Reviewed by stinkyattic on . Please help me understand the FAQ charts So, if I understand the FAQ chart correctly, I have not been letting my plants get any Phosphorus or Manganes because my PH is below 5.8. How is this possible? Wouldn't my plants be dead or extremely sleepy? I thought they needed that stuff. Am I reading the chart wrong? Also, I thought I remember posts about people keeping their PPM below 3000, but the charts say not to go above 1400. Is this what you guys do? Will they fry above 1400? Oh yeah, I'm growing in hydro. Rating: 5