Join Date: Apr 2010
Location: between CB1 and the singularity.
wouldn't the NPK values for hemp be at or very near the values for cannabis since the two are so closely related?
did you not previously w/NSPB figure the ratios?
anyway, special acknowledgement for not sitting on your hands...kudos!
2.8 ~ Nutrients The general nutrient requirements of hemp can be satisfied with generous applications of manure. Cottonseed is considered to be a perfect fertilizer for hemp, and holds moisture and mechanically prepares the soil. It is applied at the rate of 500 to 1,000 lb/acre while plowing in autumn. If the preceding crop was soybeans or cowpeas, then 500 lb/acre is sufficient.
S.S. Boyce gave these recommendations for fertilizing hemp:
"An application of 200 pounds of bone-meal in November has the effect to warm the soil and hasten germination where hemp is sown early, and to stimulate the hemp to a quick, early growth, before it comes to assimilate the coarser foods, and to give an increase of a foot to a foot and a half in growth...
"Cotton seed and farm manures of equal proportions, with an addition of 10% of acid phosphate, [can be] applied according to the condition of the soil. The only other addition to the compost of 1,000 pounds of cotton seed, 1,000 pounds barn manure and 200 pounds of acid phosphate, would be 250 pounds of ammonium sulfate [per acre]... This would only be required upon old, exhausted cotton lands, while this amount would be sufficient for 4 or 5 acres, according to fertility, and for 10 acres, provided a crop of cowpeas broadcast had preceded."
Steep-water in which hemp has been retted contains: C (55.66%), H (8.21%), N (6.45%), O (29.68%). R. Antoniu, et al., reported that it makes a valuable fertilizer :
"The wastewaters from hemp retting may be used for irrigation without presenting the danger of polluting the phreatic waters with organic substances because these substances are nearly totally retained on the filtration field. The chloride content of the raw wastewater indicates small quantities that could not produce the soil salinization after irrigations. In the phreatic water below the experimental field, the chloride content is 10-fold reduced. While the waste water is acid, the water under the filtration and irrigated field has a neutral or slightly alkaline reaction. Wastewaters were utilized for the irrigation of seed corn, silo corn, sugar beet (furrow irrigation), and alfalfa. For irrigated seed corn there was an increased production (139-143%) in comparison with the non-irrigated. For silo corn increases varied between 133-177%, for sugar beet between 176-183%, and for alfalfa, 107-416%. For all cultures the irrigation norm varied between 2,250-3,550 m3/ha."
I. Popescu and I. Afusoae reported this finding from their study of retting:
"Fermentation can help turn hemp boon [hurds] into a suitable product for soil fertilization. During fermentation the boon reaches almost the same level of assimilable N, K, Mn and Cu as in barnyard manure."
If NPK fertilizers are used, it is necessary to know their proper amounts, effects and relationships. These considerations are determined by the class of soil in which the crop is grown, and the nutrient content of the soil.
Fertilizers cause changes in basic soil properties and hemp yield. N.Gorodnii conducted experiments with this problem. He cultivated hemp on two types of loam with 6 variants of nutrients (without fertilizers, with 20, 40, and 80 tons manure/ha/year, with NPK calculated on 40 tons manure/ha, and with N 12:P 90:K 60):
"With continuous cultivation of hemp on a background of ammonium sulfate, superphosphate, and sylvite, the total absorbed bases in the soil, the rate of Ca saturation, and the nitrification ability were decreased, saturation of the absorbing complex by N and NH4 ions and the exchange and hydrolytic acidity of the soil were increased: the physical properties of the soil deteriorated, the density increased and the percentage of water-resistant aggregates decreased. Applying mineral fertilizers during the first years increased the hemp seed yield 100%, in comparison with the same doses of manure. Application of manure, in comparison with the same doses of mineral fertilizers, increased the weight of common hemp 2-3 fold. " (35)
The nutrient uptake by cannabis reaches it maximum just before maturity and blossoming. Nitrogen and phosphorus uptake then increase up to 250%, and potassium requirements increase 400%. The uptake of calcium and magnesium increases 150%. Additional amounts of nutrients must be readily available to the plants at that time in order to produce maximum yields. Hemp consumes about 1 kg of nutrients for each kg of fiber it produces. At least twice as much nutrients must be available than will be removed from the soil by the harvested plants. If hemp is field-retted, nearly half of the nutrients are returned to the soil.
The 1897 USDA Year Book listed the amounts of fertilizing elements required to produce 100 pounds of hemp fibers from 600 lb of plant weight: N (6.27 lb), KOH (10.13 lb), H3PO4 (3.32 lb). For a yield of 1,500 lb of fiber/acre (9,000 lb of growth), the nutrient requirements would be: N (94.05 lb), KOH (151.95 lb), and H3PO4 (49.8 lb).
Fertilizer trials conducted on six soil types at the Iowa Agricultural Experiment Station (1942-43) gave these results:
Where N (25 lb/acre), P (50 lb P2O5), and K (25 lb K2O) were applied singly and in combinations, average increases in acre yield of dry, rettted straw from fertilization ranged from 0.37 to 0.90 ton, P from 0.12 to 0.80 ton, and K from -0.32 to +0.25 ton N at 100 lb/acre produced substantial yield increases over N at 25 lb, which was not enough for maximum yields. Response to P was limited by N deficiency in a number of cases. N-P combinations produced higher yields than did either N or P or PK. In general, K did not increase hemp yields, [which] were usually highest on soil types which contained the greatest quantities of N and organic matter, provided drainage was adequate. (36)
Commercial hemp farmers in the temperate zones of Europe generally use a nutrient ratio of 2N:1P:4K. In hot, sunny, and tropical climes, hemp uses less potassium, and a ratio of 2N:1P:2K is more suitable. In areas having a winter or monsoon season, more K and less N is required, so the ratio 2N:1P:3K is used.
Other reports state that a high yield of fiber is obtained with about 160 kg N, 110 kg P, and 90 kg K per hectare. The highest quality bast fiber reportedly is obtained with about 70 kg of P and 60 kg of K per hectare, followed by a later dressing of 90 kg N, 70 kg P, and 60 kg K/ha. This also yields a 100% increase in fiber content in comparison to other NPK ratios. Canadian hemp farmers have applied N at 120 kg/ha, P at 100 kg/ha, and K at 160 kg/ha. M. Molina, who cultivated hemp for 13 years in Italy, stated:
"Fertilization with 300 kg of ammonium sulfate or 450 kg of dried blood, 500 kg superphosphate and 150 kg K-sulfate per hectare is recommended." (37)
Dr. Ivan Bocsa summarized the NPK requirements of hemp thus: Class I (rich soil) requires 16-43 lb N/short ton of stalk yield, 8-24 lb P/short ton, and 7-24 lb K/short ton. Soil Classes II and III require 20-46 lb N/short ton, 14-34 lb P/short ton, and 8-27 lb K/short ton.
G.R. Bedak tested the effectiveness of periodic and annual applications of fertilizers in a hemp-hemp and hemp-corn crop rotation. The application of P and K fertilizers every two years does not affect the quality of fiber, and the cost of storing, transporting and applying fertilizers are about 23% less than for annual application. (38)
L. Dobrounof reported these findings from his studies of critical periods in the mineral nutrition of hemp:
"There is a long period during which a given nutrient exerts its influence... Beginning when the hemp plant is 6-12 days old, it lasts (in relation to the fiber) in male plants 22-28 days (i.e., until the beginning of flowering) and in the female plants 32-38 days (i.e., until flowering is complete). Within the period, there exists a short critical period during which the mineral nutrition exerts its greatest influence on the direction and intensity of vegetative and reproductive development. In male plants this period is 4-5 days before the buds are completely formed, while in female plants it is the 8-10 days at the beginning of flowering. At the beginning of the period of effective action is the stage when the plant is passing from nutrition at the expense of the seed to independent root nutrition. This stage lasts 4-6 days and begins when the plants are 6-8 days old. (39)
N--- Approximately 100-150 kg N/ha (and 80-100 kg P/ha, and 100-180 kg K/ha) is required to obtain 10 tons of stems/hectare (10 kg N per ton of dry stalk).
Though the stem yield is high, the quality of fiber decreases with increasing amounts of N. Under low-light conditions, ammonium sulfate or nitrate stimulates stem growth. The absorption of N is most intensive from 20-25 days after germination. (40-46)
Cannabis is nitrophilic, but if the plant is grown for its resin, the supply should be kept under 400 ppm, and it must be reduced to about 100 ppm during flowering. The application of N should be reduced 20% in very hot weather.
The Russian agronomist B. Lesik showed that the form of N substantially affects the growth of hemp and the quality of its fiber:
"When ammonia N was applied, the plants passed through their development cycle more rapidly. The stalks were thinner and there was less development of wood. In comparison with nitrate N, ammonia N caused increases in the yield of long fibers, in the length of the elementary fibers, in flexibility, tensile strength, and uniformity of the fibers, and cellulose content, and there was a decrease in the amount of waste fibers. The retting process also proceeded more quickly, and a smaller amount of extractive substances (organic acids and N) accumulated in the retting fluid. Fertilization with the mixed form gave intermediate results. The thinness of the fibers did not depend on the form of N applied". (47)
High N has a "masculinizing" effect on the hemp phenotype; it stimulates the formation of male flowers. The proportion, degree, and number of monoecious flowers increases with increasing N, and the total N content is always higher in monoecious plants than in females, whatever the dose of N. (48)
Excessive N causes hemp to grow rapidly as seedlings, but the plants wilt, turn to copper-brown, and die when they begin to flower. High levels of N in the middle of the growth cycle will cause water uptake to increase, and induces a sex ratio as high as females 9:1 males. An excess of N is indicated by abnormally large, pulpy branches and veins, with few flowers. The stem turns brown, and terminal shoots stop developing. Leaves are spotted with dead areas, and they curl, pimple, and turn yellow between veins. The breaking strength of the fibers is reduced by about 15%. The stem texture is herbaceous with a hollow pith and short internodes. Excess N added during preparation of the soil inhibits stem development. Best results are obtained by adding half of the required N in the primary treatment, and the second half at the first feeding.
If the initial growth of a hempfield is slow, it can be aided by a foliar spray of 20 kg of urea in 400 liters of water/ha. The addition of ammonium sulfate or nitrate with sulfur before blooming occurs will increase the growth rate considerably. Ammonium nitrate is more effective than the sulfate. Sodium nitrate gives good results, but the quality of fiber is poor. Cannabis is very sensitive to chlorine; therefore, sulfate salts are recommended over chlorides or nitrates.
A deficiency of N causes the entire hemp plant to turn yellow (chlorosis) within a week. Lower leaves curl and shrivel, and veins turn purple. Stems are abnormally small and hollow with a woody pith. Growth and flowering are retarded, and the plants are mostly male. (49)
K. Tulaikova found bacterial cycles in the N metabolism of hemp:
"The requirements of hemp for abundant nitrogen fertilizers were found to be related to the development of numerous and diverse rhizobia on its roots, mainly ammonifying bacteria. During the germination stage, the bacteria are parasitic because they utilize not only the root excretions of plants but partly also the plastic matter which is being transported from leaves to roots. This is demonstrated by the weak development of the root during the first half of the growth period. If N feed is abundant, the relations between the hemp and bacteria are symbiotic... Simultaneous feeding on nitrates by both root bacteria and hemp induces N deficiency in the plants. Therefore, nitrate fertilizers are especially required for hemp development... An improvement in N status observed after bacterization with silica bacteria was probably due to the ability of the latter to fix atmospheric N." (50)
There are differences in the root microflora of hemp according to sex. Ammonifying and denitrifying bacteria which decompose organic P predominate on the roots of females, and greatly depend on the food reserves in the soil. Deficiency of soil nutrients increases the concentration of microbes on the roots; thus the number of ammonifying bacteria is much less on the roots of hemp grown in rich soil than in the roots of plants grown in exhausted soil. Silicate bacteria predominate on male roots, which absorb N and K more vigorously than the female up to the flowering phase. (51)
P --- Hemp growth, fiber yield, and concentration of THC are positively correlated with extractable phosphate. Cannabis uses 250% more phosphorus at flowering than during the vegetative phase. A deficiency of P shows as abnormally dark dull green leaves with a purple tint on the underside, and downward-curled margins. The stem gradually turns reddish, then black. The roots are long, with few laterals. The plants are slow to mature and set seed.
P. Gorshkov studied the peculiarities of P nutrition for hemp:
"To obtain high yields of hemp, it is necessary to assure the plants an easily accessible source of phosphoric acid by applying granulated superphosphate at the very beginning of development, before the plants have reached the phase of 6 pairs of leaves. At later phases of development the requirement for P may be met by soil P and by less soluble forms of P fertilizer." (52)
The Russian agronomist M. Khann confirmed the beneficial effect of superphosphate drilled in with hemp seeds:
"This method allowed for a 3-fold decrease of the superphosphate without lowering of the productivity. The increase in the yield of fiber obtained from 1 kg P2O5 drilled in with the seeds exceeded by 3-6 times the corresponding increases from broadcasting 1 kg P2O5. The corresponding seed yield increase was 3.5-4.7 times higher." (53)
K --- Either potassium sulfate or potash is recommended over KCl because the chloride ion interferes with fiber development. The combination of potash with manure increases yields up to 30%, and increases the availability of phosphorus by almost 200%. A combination of potash, Mg-sulfate and manure produces the greatest yield, increasing with higher levels of Mg. Potash strengthens the stalk and stems and increases the resistance of hemp to broom rape. The absorption of K is most intense in the 4th week after germination.
Additional K increases plant height, thickens the stem, and produces heavy, large, dark green leaves. The growth cycle is shortened by about one week, and the sex ratio is stabilized at about females 7:3 males. An excess of K after the 10th week, or when flowering occurs, will delay maturity and inhibit resin production. White spots appear on leaves, meristematic growth ceases, and the stem is woody and hollow. When cannabis is cultivated for resin, the supply of K should be reduced by 50% during flowering.
I. Berzak reported these results of his experiments on the effect of various K fertilizers on the yield and quality of hemp fibers:
"The highest yields of stems and fibers were obtained with kalimag (K-sulfate/Magnesia/Mg-sulfate), and with K-chloride/K-sulfate mixture, whereas the lowest was obtained with kainite (K-chloride/Mg-sulfate). Male hemp responded to K fertilizers much more than female hemp". (54)
Potassium deficiency is indicated by coppery mottling and curled, grey edges or a brown margin on leaves, followed by dark spots and bleaching between the veins. The symptoms first appear on bottom leaves. Old foliage turns dark gray, and new leaves turn yellow and die. Growth is retarded, and the roots and apical meristems turn pale yellow. The stem is herbaceous, and hollow in males, while females are solid. Deficiency can occur in acidic soil or in low-light conditions. The addition of a little detergent will increase the wetness of the nutrient solution and allow K to be more easily absorbed.
When K is deficient, transpiration is reduced, but water consumption is increased, especially in young plants. A deficiency of K decreases the yields of stems and fiber, but contributes the formation of strong, elastic fibers. (55)
Ca --- Calcium gives cannabis very strong, fibrous, short stems with dark green leaves and swollen flowers. An adequate supply is vital in the 6th-9th weeks of growth. The largest absorption of Ca is made possible when calcium carbonate is applied together with small doses of humus. (56)
Calcium-deficient plants are stunted, weak and flabby. Terminal buds die, and the stem becomes brittle and covered with dark areas. Upper leaves are darker than usual, yellow at the edges, and they crinkle, dry up, and fall off. Any new leaves that form will die. Brown and white spots appear on lower leaves.
Excessive Ca will stunt the early growth of cannabis, and causes terminal shoots to be weak and under-developed. Foliage is less abundant, and blackening occurs around the veins. The stems are fibrous and woody, with a hollow pith. The sex ratio changes to males 7:3 females.
Calcium affords plants considerable resistance to infection with Botrytis; the higher the level of calcium, the lower the incidence of Botrytis.
Trace Elements --- Micronutrient deficiencies often are caused by alkaline water, which prevents uptake by plants. Such deficiencies usually can be covered by the use of commercially available "transplanting solutions" and by adjusting the soil to neutral pH.
Mg --- Cannabis is very sensitive to magnesium deficiency, which is likely to occur in sandy soils and during seasons of heavy rainfall. Chlorosis begins on the bottom leaves. Grey-white patches, varicose veins, and yellow margins appear on the leaves, which curl and die on the edges. Growth is stunted, the stem is thin, and leaves drop off. The stem texture of males is woody, and females are herbaceous. The pith is hollow. A deficiency can be corrected with Mg-phosphate and brine (1 quart per 100 lb of compost), or with Epsom salts.
Hemp has an extraordinarily high requirement for Mg, and is exceptional in comparison to most other plants, which are killed by applications of Mg alone. Combinations of K and Mg give the highest yields, which increase considerably with an increase in the Mg. (57)
A. Haraszty conducted experiments for 10 years to augment the yield of hemp fiber with macro- and micronutrients (tested in over 50 combinations). He found significant effects with formulations containing K, Mn and Mg (applied in the form of their sulfates at 10 kg/ha), by which he achieved up to 32% increases in fiber quantity. The combination of K and Mn gave a 17% increase. (58)
Fe --- The symptoms of iron deficiency are the same as for magnesium, but they appear on the upper leaves first. Acidic soils dissolve and chelate iron, making it unavailable to plants. Powdered magnetite (magnetic iron oxide) will supply sufficient Fe, and it stimulates plant growth by the effect of magnetic energy. 10 ppm of Fe gives the best growth of hemp fiber; 5 ppm gives the best yield of cannabinoids.
C. Olsen studied Fe absorption by hemp in hydroponic beds:
"When hemp is cultured in solutions low in Ca and with Fe-sulfate as Fe source, increasing growth inhibition due to Fe intoxication is observed when the pH of the solution decreases from 6 to 4. This is due to the fact that the ferric ion concentration in the solution increases greatly when the pH is lowered to 4. The same is true in soil. Even so, hemp can develop quite normally in solution of pH 4 provided the Ca ion concentration is high, resulting in a sufficient lowering of the rate of Fe absorption to preclude intoxication. This antagonistic situation does not occur in nature since soil of low pH and high Ca concentration does not exist." (59)
Mn --- A deficiency of manganese will stunt the growth and flowering of hemp. Leaves appear mottled with grey-brown necrotic spots. The plants lack vitamin C; there are some deaths. Signs of deficiency first appear on shoots. Leaf margins remain green while the rest of the leaf turns yellow or white.
S --- Sulfur stimulates root growth and seed production. S-deficient hemp is pale green, with purple veins. The stem is stiff, woody, and thin; the seeds are immature.
B --- Hemp requires 250 grams of boron per acre. When sufficient P and K are available, an additional application of boric acid (1 kg/ha), Cu-sulfate (1 kg/ha), and Mn-sulfate (10 kg/ha) will produce a significant increase in yields and in the quality of fiber and seeds. A deficiency of B is revealed by cracked, stunted stems and dry rot. Leaves turn purple, terminal shoots curl and die, petioles become brittle, and the flowers are covered with dry areas. New shoots turn gray or brown and die with a burnt appearance. The situation can be corrected with a foliar spray of boric acid.
Cu --- Cannabis does not have a high tolerance for copper, but supplementary Cu-sulfate will improve the quality and yield of hemp, especially in peat, which often is deficient in this element. A deficiency causes stems to weaken and break. Treatment of a field with 10 kg/yoke (1.42 acres) will increase the fiber bundle diameter up to 15%; when the Cu is combined with cobalt, the bundle diameter will increase up to 23%.
Mo --- A deficiency of molybdenum is indicated by yellowing between veins on leaves. The middle leaves turn yellow.
Zn --- A deficiency of zinc is indicated by chlorosis between the veins at the base of shoots, and by the accompanying twist of leaf blades. Flowering is inhibited.
Over-watering produces symptoms resembling nutrient deficiencies or excesses. These usually can be corrected by reducing the water supply, or by drainage.
Table 2.3 ~ Symptoms of Nutrient Deficiency/Excess
2.9 ~ Cultivating for Cannabinoids
According to a United Nations study, 5 factors are necessary for the "cultivation of Cannabis for a high resin production": (1) genotype, (2) photoperiod, (3) N-P-K, (4) at least 60-80 cm separation between plants, and (5) "optimal temperature of the ground at the time of sowing". Resin production is minimal at 44o F (See also 2.5 and 2.10).
The production of cannabinoids (THC, CBN, CBD, etc.) is greatly influenced by nutrients. As soil N increases relative to Mg, CBD increases relative to CBN. Increasingthe ratio of N to Cu increases the level of CBD. Increasing amounts of P convert CBN to THC. Low to medium levels of P produces a high level of CBD, but CBD decreases with high levels of P. Low levels (levels less than 40 ppm) of Mg produce more CBD than do high levels of Mg. As levels of Mg increase relative to Ca, the concentration of THC decreases. The concentration of Mg and Fe in leaves is positively correlated to THC levels. Potassium increases the concentration of CBN by effecting the dehydrogenation of THC. An excess of K in the 3rd month will inhibit resin production. Excess Ca will inhibit resin production, and it increases the production of CBD in the resin is produced. Either an excess or deficiency of Mg produces more CBD. 5 ppm Fe gives highest yields of THC.
The recommended "ideal" pattern of nutrient application for cannabinoid production is said to be: high N and K, low Ca, and medium Mg during the first 2 months of growth, continued high N and K, medium Mg, and increased Ca during the next 6-8 weeks, followed by decreased N, K, and Ca, and increased Mg through the flowering phase. Many growers use a commercial 15-30-30 formula throughout the season.
Mel Frank offers this micronutrient formula for high cannabinoid production: Fe-sulfate (5 mg/gal), Cu-sulfate (0.2 mg/gal), Mn-sulfate (2 mg/gal), Zn-sulfate (0.2 mg/gal), Boric acid (2 mg/gal), Molybdenic acid (0.1 mg/gal). Use 1 tspn/gal of nutrient solution, once monthly.
Bill Drake gives this recipe in Marijuana: The Cultivator’s Handbook: Ca-sulfate (6 oz), mono-Ca-phosphate (4 oz), Mg-sulfate (6 oz), K-nitrate (8 oz), and Fe-sulfate (1 gr). Use 1 tspn/gal.
Many marijuana growers reportedly use a commercial 15-30-30 NPK mixture successfully throughout the growing season.
"I'm not always a dick...but when I am, I drink cheap beer".