Ran across this article yesterday, which says we may all be doing Phosphorous wrong...
Basically, plants may front-load P during the start and then use the stored P during flowering (vs. uptaking needed P from soil during late veg / flowering) - so may not really be a need to increase P feed levels at end of veg/through flowering.
"The researchers found that hemp plants front-end load P during the first half of the growing season as seen with the plant’s upward accumulation of P. At midseason, the total accumulation in the plant plateaus. This indicates that the plant uptakes limited additional P. Hemp relies upon those internal P reserves and translocates (moves) P if it is required in other parts of the plant. This suggests that adequate P levels should be provided to cannabis during the first half of the production cycle for the plant to accumulate an adequate reserve that can be translocated if needed later. Providing a P boost late in the growing season appears to not be needed. There is a need to conduct a scientifically based trial to clear up this uncertainty with greenhouse-grown cannabis.
While the target level of P required by greenhouse-grown cannabis is not currently known, we would speculate based on the scientific data from other species that levels of 15 ppm to 20 ppm P supplied on a constant basis should be all that is required. At North Carolina State University we have begun an experiment looking into optimal P rates supplied at a constant level throughout the cannabis crop cycle and will be able to further refine those recommendations in the near future."
Any thoughts?
Not sure anyone could really verify from experience unless you measure run-off P levels in a hydro set-up throughout the grow. In soils, maybe it's still useful to increase P in second half to maintain soil balance (i.e., replace P absorbed during first half) to prevent lock-out.
My take-away, at least, was an increase in the importance of myco to improve bio-availability of soil P from the start of the grow...
Basically, plants may front-load P during the start and then use the stored P during flowering (vs. uptaking needed P from soil during late veg / flowering) - so may not really be a need to increase P feed levels at end of veg/through flowering.
"The researchers found that hemp plants front-end load P during the first half of the growing season as seen with the plant’s upward accumulation of P. At midseason, the total accumulation in the plant plateaus. This indicates that the plant uptakes limited additional P. Hemp relies upon those internal P reserves and translocates (moves) P if it is required in other parts of the plant. This suggests that adequate P levels should be provided to cannabis during the first half of the production cycle for the plant to accumulate an adequate reserve that can be translocated if needed later. Providing a P boost late in the growing season appears to not be needed. There is a need to conduct a scientifically based trial to clear up this uncertainty with greenhouse-grown cannabis.
While the target level of P required by greenhouse-grown cannabis is not currently known, we would speculate based on the scientific data from other species that levels of 15 ppm to 20 ppm P supplied on a constant basis should be all that is required. At North Carolina State University we have begun an experiment looking into optimal P rates supplied at a constant level throughout the cannabis crop cycle and will be able to further refine those recommendations in the near future."
Any thoughts?
Not sure anyone could really verify from experience unless you measure run-off P levels in a hydro set-up throughout the grow. In soils, maybe it's still useful to increase P in second half to maintain soil balance (i.e., replace P absorbed during first half) to prevent lock-out.
My take-away, at least, was an increase in the importance of myco to improve bio-availability of soil P from the start of the grow...
