Smokin Moose
Fallen Cannabis Warrior & Ex Moderator
Most growers show a keen interest in fertilising, since it is one factor over which they have some control. Most growers also feel that nutrients, which play such an important part in plant growth, probably have a relationship to the potency, and this is a reasonable assumption. In marijuana lore, potency is sometimes attributed to particular soil types (for instance, red dirt, which is iron-rich) or to presence or lack or certain nutrients (for examples, nitrogen or potassium deficiency).
The relationship of potency to soil conditions, in particular the nutrient content, has been looked at recently by several research groups. In two such studies, (71,74) the cannabinoid content of naturalised weedy hemp stands in the Midwest was examined. Variations in potency were then correlated to soil properties, such as N, P, and K content. The two papers came to similar conclusions. First, stands growing in areas where they were under stress tended to produce less biomass (yield) but were more potent overall. Second, when nutrients or other growth factors, such as height and weight of plants or root size, were correlated with potency, potency was almost always correlated positively with positive growth factors. That is, higher potency occurred when the plants were growing with adequate or high amounts of nutrients present, not when nutrients were inadequate.
What appears to be a contradiction (stress leads to higher potency, or good growing condition lead to higher potency) may be explainable in terms of what these experiments actually measured.
A basic assumption in these studies was that all the plants were relatively homogeneous genetically, since they may have originated from a single stock of hemp grown during World War II. Assuming this is true, then variations between stands would be due to differences in local environmental factors. However, since environmental condition differed locally for separate stands, one cannot tell whether variations in potency between stands are due to present environmental factors (phenotypic responses) or reflect thirty years of adaption by each stand to its local environment (genotypic shifts).
It may be that positive growth factors are associated with higher potency in phenotypes (plants now growing), whereas stress leads to higher potency in succeeding generations, because of selective pressure. It is interesting that both papers reported strong positive correlations between higher potency and competition from other weeds, since competition between plants does exert strong selective pressures.
The following list of possible effects of nutrients on potency has been adapted from these four studies. (63,71,74,231)
Nitrogen
Nitrogen was positively correlated with higher potency. Once controversy in marijuana lore is whether a nitrogen deficiency during flowering increases potency. We have grown plants with N deficiencies, and they seemed no more potent than those grown with high amounts of nitrogen available. However, the N-deficient plants did produce a much smaller harvest.
Phosphorus
P has been correlated positively with higher potency in all studies that have examined this factor. Phosphorus is necessary for good flower development and seed production. Give the plants a steady supply of phosphorus throughout growth and in particular during flowering.
Potassium
K has been correlated both positively and negatively with potency. More often, it has been found to be negatively correlated. As discussed previously, plants that show some potassium deficiencies may grow well; so you may choose not to treat minor symptoms of K deficiency often grows vigorously with little harm other than the spotting and the loss of some lower leaves. It should not be necessary to fertilise with potassium during flowering unless deficiency symptoms are severe and the plant has ceased growing.
Calcium
Abundant Ca levels have been consistently correlated with higher potency.
Magnesium
Mg has been negatively correlated with potency. However, this may have been dur to the interaction of Ca and Mg, and may reflect Ca's strong positive correlation to potency, rather than the negative effects of Mg per se. Plants that show Mg deficiencies must be fertilised, or they will quickly lose most of their leaves and barely remain alive.
The relationship of potency to soil conditions, in particular the nutrient content, has been looked at recently by several research groups. In two such studies, (71,74) the cannabinoid content of naturalised weedy hemp stands in the Midwest was examined. Variations in potency were then correlated to soil properties, such as N, P, and K content. The two papers came to similar conclusions. First, stands growing in areas where they were under stress tended to produce less biomass (yield) but were more potent overall. Second, when nutrients or other growth factors, such as height and weight of plants or root size, were correlated with potency, potency was almost always correlated positively with positive growth factors. That is, higher potency occurred when the plants were growing with adequate or high amounts of nutrients present, not when nutrients were inadequate.
What appears to be a contradiction (stress leads to higher potency, or good growing condition lead to higher potency) may be explainable in terms of what these experiments actually measured.
A basic assumption in these studies was that all the plants were relatively homogeneous genetically, since they may have originated from a single stock of hemp grown during World War II. Assuming this is true, then variations between stands would be due to differences in local environmental factors. However, since environmental condition differed locally for separate stands, one cannot tell whether variations in potency between stands are due to present environmental factors (phenotypic responses) or reflect thirty years of adaption by each stand to its local environment (genotypic shifts).
It may be that positive growth factors are associated with higher potency in phenotypes (plants now growing), whereas stress leads to higher potency in succeeding generations, because of selective pressure. It is interesting that both papers reported strong positive correlations between higher potency and competition from other weeds, since competition between plants does exert strong selective pressures.
The following list of possible effects of nutrients on potency has been adapted from these four studies. (63,71,74,231)
Nitrogen
Nitrogen was positively correlated with higher potency. Once controversy in marijuana lore is whether a nitrogen deficiency during flowering increases potency. We have grown plants with N deficiencies, and they seemed no more potent than those grown with high amounts of nitrogen available. However, the N-deficient plants did produce a much smaller harvest.
Phosphorus
P has been correlated positively with higher potency in all studies that have examined this factor. Phosphorus is necessary for good flower development and seed production. Give the plants a steady supply of phosphorus throughout growth and in particular during flowering.
Potassium
K has been correlated both positively and negatively with potency. More often, it has been found to be negatively correlated. As discussed previously, plants that show some potassium deficiencies may grow well; so you may choose not to treat minor symptoms of K deficiency often grows vigorously with little harm other than the spotting and the loss of some lower leaves. It should not be necessary to fertilise with potassium during flowering unless deficiency symptoms are severe and the plant has ceased growing.
Calcium
Abundant Ca levels have been consistently correlated with higher potency.
Magnesium
Mg has been negatively correlated with potency. However, this may have been dur to the interaction of Ca and Mg, and may reflect Ca's strong positive correlation to potency, rather than the negative effects of Mg per se. Plants that show Mg deficiencies must be fertilised, or they will quickly lose most of their leaves and barely remain alive.
