Who Thinks this is a Light Issue?

[NDfarmboy]

I've posted these pics on another thread but looking for more opinions. I use a 400 watt HPS to flower and keep it about 18" from plants (12/12 format). I think I do everything right ph and fert-wise. But, the top portion of the plants have leaves that are yellowing, crinkling on edges and ends - not all but many. Bottom leaves actually doing fine. Both plants are topped during veg. I've grown many times and can't remember having light issues. I've got air flowing thru light canopy and heat at top of plant seems good. I'm about 11 weeks in overall and 6 weeks in flower room. Maybe I'm pushing them too hard. I grow 'em smaller cause I have too.

 

[Week4Bytch]

I've posted these pics on another thread but looking for more opinions. I use a 400 watt HPS to flower and keep it about 18" from plants (12/12 format). I think I do everything right ph and fert-wise. But, the top portion of the plants have leaves that are yellowing, crinkling on edges and ends - not all but many. Bottom leaves actually doing fine. Both plants are topped during veg. I've grown many times and can't remember having light issues. I've got air flowing thru light canopy and heat at top of plant seems good. I'm about 11 weeks in overall and 6 weeks in flower room. Maybe I'm pushing them too hard. I grow 'em smaller cause I have too.

whats your PAR at the top there? And if you don't know, how close are your lights to the top? Ok, just read your OP.. raise your lights man, to 24 inches. your leaves are pointing down, trying to get away from the light. Flower looks nice and frosty. I susggest just raising the lights to 24 inches from the top of your plants, if you can't, reduce the flower on time to 11 hours on.

 

[NDfarmboy]

I'm not understand PAR and OP. Please enlighten (no pun intended).

 

[Mikedin]

I'm not understand PAR and OP. Please enlighten (no pun intended).

Par / PPFD (copy /paste for clarity lol)

What is PAR and why is it important for plant growth?​

PAR is the spectrum of light wavelengths that plants use for photosynthesis (400nm - 700nm). It is important for plant growth because it determines the rate of photosynthesis, which in turn affects plant growth and development.

TLDR: PAR is all the different kinds of light plants need.

‍

What is PPFD and why is it important for plant growth?​

PPFD stands for Photosynthetic Photon Flux Density. PPFD is a measure of the amount of PAR that is actually hitting a specific area per unit time, usually expressed in micromoles per square meter per second (μmol/m²/s). It is important for plant growth as it quantifies the amount of PAR, and is also a way to describe the intensity of light within the PAR range that plants need for photosynthesis.

TLDR: PPFD is how much of the light is actually hitting the plant.

‍

What is the difference between PAR & PPFD?​

PAR is the range of wavelengths of light that plants need for photosynthesis, while PPFD measures the amount of PAR that is actually hitting the plant at a specific location and time. So PAR is the type of light and PPFD is how much of that light there is.

Excellent video to watch and learn

OP= original post

 

[LoveGrowingIt]

Who Thinks this is a Light Issue?

I do.

 

[NDfarmboy]

Thanks for that educational information. I will study before next grow. I love to get these valuable lessons. Never stop learning.

 

[cannafarmer420]

Par / PPFD (copy /paste for clarity lol)

What is PAR and why is it important for plant growth?​

PAR is the spectrum of light wavelengths that plants use for photosynthesis (400nm - 700nm). It is important for plant growth because it determines the rate of photosynthesis, which in turn affects plant growth and development.

TLDR: PAR is all the different kinds of light plants need.

‍

What is PPFD and why is it important for plant growth?​

PPFD stands for Photosynthetic Photon Flux Density. PPFD is a measure of the amount of PAR that is actually hitting a specific area per unit time, usually expressed in micromoles per square meter per second (μmol/m²/s). It is important for plant growth as it quantifies the amount of PAR, and is also a way to describe the intensity of light within the PAR range that plants need for photosynthesis.

TLDR: PPFD is how much of the light is actually hitting the plant.

‍

What is the difference between PAR & PPFD?​

PAR is the range of wavelengths of light that plants need for photosynthesis, while PPFD measures the amount of PAR that is actually hitting the plant at a specific location and time. So PAR is the type of light and PPFD is how much of that light there is.

Excellent video to watch and learn

OP= original post

Dr bugbee!!!!!!!

 

[NDfarmboy]

I will study up, but I'm thinking I lost this crop. One of these plants has never been closer than 24" to 400 HPS light which is air cooled. Everything is happening up top like water & nutes not getting there. Haven't had this happen in 15 years! I suppose I could harvest early and see what I get? Deteriorated a lot day to day (look at pics earlier in thread). Damn!