New Grower Nitrogen (nonexplosive form) plant food

[GCase]

I had a short discussion with, I believe, Muddy or TBM pertaining to giving plants a shot of N during latter part of vegging. He had been discussing this with other senior growers because of the tendency of the Ps to deplete N and begin lower leaf wilting/yellowing. Anyway, I was looking for a good sources of N and had something in mind but just had to do some research. The following link is a summary in simple language all about N and the sources--to the right are some links for organic and conventional sources too. Thought some might like the info. for a bookmark. :thumbs: cg

http://www.ehow.com/about_5390862_sources-nitrogen-fertilizer.html

 

[Trifid]

In most cases nitrogen is already highly abundant in the growing medium - in fact, plant's are unlikely to deplete it entirely. It's not necessarily the nitrogen content leading to leaf abscission but rather it's availability. Changes to the soil chemistry (changes to relative carbon/nitrogen ratios) toward the end of the vegging cycle behave as signals to the plant inducing the biosynthesis of flowering hormones and the suppression of auxins which leads to changes in apical dominance, lower leaf abscission and the onset of bloom - alterations to the soil chemistry in this case are due primarily to the co-activities of the rhizosphere and associative micro-organisms which has an inhibitory effect on nitrogen availability.

Approximately 90% of the nitrogen in the surface layer of most soils exists in complexed (chelated) organic forms, with much of the remainder being present as free aqueous ammonia (NH4+) which is stable within the lattice structures of clay-minerals. The surface layer of most cultivated soils contains between 0.06 and 0.3% N from humic sources, where peat-based mediums have approximate N contents no greater than 3.5%.

The degradation of organic residues by soil-microorganisms leads to incorporation of carbon into microbial tissue with the remainder being liberated as CO2. As a general rule, about one-third of the applied C in fresh residues will remain in the soil after the first few months of decomposition. As bound phosphates become more readily available, the decay process is accompanied by conversion of organic forms of N to NH3 and NO3- and soil microorganisms utilize a percentage of this N for cellular processes. As a general rule it can be said that conditions which encourage the rapid decomposition of organic materials leads to narrowing of the C/N ratio. This is why nitrogen availability has a tendency to be inhibited in-concert with the onset of blooming. Thus one can assume that plants have adapted to use these chemical changes to their advantage - building their schedules around changes in soil chemistry which in the natural setting are dependent upon seasonal factors.

One way to enhance the availability of nitrogen to maintain prolific vegetation during early flowering while keeping the pH of the media within the optimal range for adequate phosphate chelation is moderate treatment with mineralized calcium @ 1000ppm (0.1%). In modern literature, calcium with vitamin-d has been shown to be an effective phosphate buffer saline for enhancing nitrogen availability in-vitro in tobacco and hop plants.

If the growing medium is adequately conditioned with calcium, macro-nutrient availability and absorption are better regulated by the assisting micro-flora as the plants undergo developmental transitions and pH is stabilized more effectively. Availability is Key.. When mineralized calcium levels are limited so are yields.

 

[Trifid]

In an effort to explain the superior performance of soluble calcium in comparison to large applications of limestone (>1 ton), it
was discovered that limestone contains less than 11 lbs. of soluble calcium per ton.

Gypsum fares a little better with 33 lbs. per ton. It is the soluble component which provides the calcium response. In this context, a few gallons of
liquid calcium will provide the same amount of soluble (available) calcium as a large amount of limestone

 

[Muddy]

Let me see if I understand this correctly. Sufficient N already exists in most soil but through the decomposition process it's ratio to calcium changes, causing the N to become less available to the plants. The correct ratio can be reestablished by the addition of mineralized calcium. What about the calcium supplements being sold that contain calcium nitrate and calcium chloride, are they an effective solution?

 

[Trifid]

Muddy - In this case, the C/N ratio refers to carbon/nitrogen content respectively. The C:N ratio of the organic material influences the rate of decomposition of organic matter which leads to either a release (mineralisation) or immobilization of soil nitrogen. If the decomposing organic material contains a higher fraction of nitrogen in proportion to carbon, then nitrogen is released into the soil in soluble forms - if the organic material has a less amount of nitrogen in relation to the carbon then the microorganisms will utilize the soil nitrogen for further decomposition and the soil nitrogen will be immobilized.

Since approx. 90% of the available nitrogen in the growing medium exists as organically bound residues (ie. carbon bonded compounds such as amines, amides ect..) the carbon fraction has a tendency to decrease during the vegetative periods due to consumption. It has been found that approx. one third of the carbon content in fresh residues will remain in the soil after the first few months of decomposition. As bound phosphates become more readily available and induce metabolic activity in soil flora, the decay process is accompanied by conversion of organic nitrogen to NH3 and NO3- by microorganisms that utilize a high percentage of this N for cellular processes - this has the effect of narrowing the C/N ratio and decreasing plant-nitrogen availability.The amount of carbon required for the microbes to perform celluar processes is approx. 75% of their consumption and a further 25% for synthetic processes. As a general rule, microbes require 1 kg of N for every 8 kg of carbon as the C:N ratio of microbes is 8:1.

Calcium mineralizaton in soils has the effect of increasing the solubility product of organic-nitrogen compounds enhancing their availability for plant processes. The major advantage to using calcium to effectively increase nitrogen mobility in the soil is that calcium has relatively minor influence over soil parameters such as pH, moisture retention and the mobility of other macro and micro nutrients. Calcium treatments (@ high ppm) may also be used in this way to effectively 'leech' nitrogen from soils in the case of toxicity.

 

[Trifid]

What about the calcium supplements being sold that contain calcium nitrate and calcium chloride, are they an effective solution?

The calcium nitrate is commonly applied for these reasons and remains one of the most suitable forms for calcium supplementation

 

[Muddy]

Okay, bear with me, it's starting to sink in and make sense. I have a plant in my current grow that was showing signs of N toxicity. My response was to flush the plant, feed pHed water only the next feeding, which took the plant right to the time to switch to my lower N flowering nutes. It's still showing a little too much N, so a feeding of high ppm calcium would be beneficial? In my rain water, I would need approximately 25 ml per gallon to reach a ppm of 1000. Would that be sufficient?

What about soil less mixes like the Pro Mix that I use ? It's composed of 85% sphagnum peat moss, 15% perlite, dolomite lime and starter nutrients. Without the organic matter normally contained in soils does the same hold true?

 

[GCase]

Explains why ca/mag is so often stressed. Action/result oriented growers may not know the science but the growers must have some anecdotal basis for the cal/mag supps. Trifid--I yield to the scientifically minded. We appreciate your time and effort. Of course, we will need to read and re-reread your tread and then hang on to every word to get the gist. Unless, you have a copy of the "Cliff Notes." cg

 

[Trifid]

Muddy - Can you provide some specifics regarding your starter nutrients? Your addition of lime is likely to aid the solubility product and maintain optimal pH. In modern literature peat-moss soiless mixtures have a reported C/N ratio of 58:1. Research has revealed that the most efficient method for producing well balanced, fertile composts is to maintain a C:N ratio somewhere around 25 to 30 parts Carbon to 1 part Nitrogen, or 25-30:1.

If the C:N ratio is too high (excessive carbon content), decomposition rates have a tendency to decline - on the other hand, If the C:N ratio is too low (excess nitrogen) decomposition rates become elevated and degredation of organic materials occur rapidly. Growing mediums with excessive carbon content can create problems - in order to complete the nitrogen cycle and continue decomposition processes, the soil flora will subtract any available nitrogen in the proper proportion to make use of the available carbon. This is known as "robbing" the soil of nitrogen stores, which delays the availability of plant-nitrogen until late in the season when it is no longer required by the soil microorganisms.

When their energy stores (carbon) are less than that required for converting available nitrogen into protein, microorganisms make full use of the available carbon and eliminate the excess nitrogen as ammonia. This release of ammonia to the atmosphere leads to a further loss of nitrogen from the growing medium. A C:N ratio of 20:1 is the upper limit at which excessive uptake of nitrogen from the soil is minimised. If a considerable amount of carbon is in the form of lignin or other stable materials, the relative C:N ratio will be - in most cases, larger than 20. The C:N ratio is a critical factor in producing a balanced mix with tailored decomposition activities - serving to prevent nitrogen loss and nonavailability..

Since microorganisms use approx. 30 parts carbon to 1 part nitrogen, an initial C:N ratio of 30 promotes rapid composting and provides an ample quantity of nitrogen in an immediately available form in the finished product. Fertility studies have reported optimal values from 20 to 31:1. Modern literiture claims that for C:N ratios above 30 there will be little loss of nitrogen - studies of materials with initial C:N ratios varying from 20 to 78 with nitrogen contents varying from 0.50% - 1.80% indicate that initial C:N ratio of 30 to 35 was optimum.

Composting time has a tendancy to increase with C:N ratios in excess of 30 to 40. If the percentage of bound carbonates is small, the C:N ratio can be reduced dramatically by soil microorganisms to values <10 where values of 14 and 20 are common depending upon the original materials from which the humus was formed. These studies have shown that composting a material with a higher C:N ratio would not prove detrimental to the soil, since the remaining bound-carbon is made available only at a reduced rate such that nitrogen loss by microorganisms is minimized.

Here are a few of the C:N ratios in quoted in modern literature..

Sandy loam - 7:1

Humus -10:1

Alfalfa hay - 18:1

Vegetable trimmings - 25:1

Rotted manure - 20:1

Grass clippings - 19:1

Sandy loam - 25:1

Food scraps -15:1

decomposing vegetation - 30:1...80:1

Oak leaves - 26:1

Pine needles - 60:1.....110:1

Straw - 80:1

Peat moss - 58:1

Corn stalks - 60:1

Farm manure - 90:1

Newspaper - 170:1

Sawdust - 120:1

Weathered sawdust - 142:1

fir-tree bark - 491:1

 

[Trifid]

I have a plant in my current grow that was showing signs of N toxicity. My response was to flush the plant, feed pHed water only the next feeding, which took the plant right to the time to switch to my lower N flowering nutes. It's still showing a little too much N, so a feeding of high ppm calcium would be beneficial?

To tackle nitrogen toxicity I usually prepare 4 liters of mineralized calcium solution @ 300,000ppm (30%) - that's approx. 1g/ltr into a 10ltr bucket and leave the plant to soak, fully-submersed in the stock for 10-15 mins. This ensures the system reaches a state of equilibrium throughout the growing media serving to 'leech' the excess nitrogen. The container is then removed from the bucket and allowed to drain, one may choose to flush at this point to ensure calcium levels return to normal. The problem associated with flushing is that much of the available micro-nutrient content and beneficial micro-flora are eliminated also and subsequently must be replaced using a full-spectrum supplement.