The available nitrogen content in initial substrate of my study is about equal 27% total nitrogen. After vermicomposting process, it increased from 27% to 90%. I suspect the result was wrong because i had some problems in nitrogen analyzing process.
Vo , an interesting issue raised ....
C: N ratio somehwere near 20-25 ( preferably less than 25) is considered as a reliable index of compost maturity. Microbes require 1 part of nitrogen to decompose 30 part of carbon . The low reduction of organic carbon content during vermicomposting help retain higher total nitrogen in the vermincompost.. i feel , somewhere wrong method of total N estimation is followed..
Here is a relevant PDF , hope you find it useful..
Hi Prof, thank you for your answer and your paper. But it is out from the subject of my question. I am sorry you because may be my question was not clearly. I asked how much percentage of available nitrogen (soluble nitrogen in H2SO4 0.1M) can be accounted in total nitrogen (Soluble nitrogen in concentrated H2SO4)...
i am still not in a position to follow your question , do you want to know , how much percentage of total nitrogen from vermicompost is available to plants..?
The ratio (availble nitrogen/total nitrogen) was about 90%, i worried that that result is not true because the nitrogen analyzing devices had some problem.
In vermicompost different earthworm species are impacted differently. Vermicompost has 1.5-2.5% N, it is a product or process using various worms. The earthworm feed C:N ratio is 25:1 , the ratio is declining with time and after 60 days you may find 5:1. But the effect mainly depends on the type of earthworm use. For example, Eisenia fetida and Perionyx excavatus showed greater microbial activity in that case the ratio of available N/total N you may get up to 90% and I believe it may possible. But the problem is the results are very inconsistent. However the advantage is that these castings have been shown to contain reduced levels of contaminants and a higher saturation of nutrients. It is an excellent nutrient rich organic fertilizer.
Mr.Thien,Good question.The proportion of available N in total N depends on feed N and the transformation of N in the gut of earthworm and subsequently in the wormcasts during maturation period of composting.Many workers reported high amount of N in vermicompost ranging from 1.5 -3.5 % N(slightly higher than what Dr.Tarafdar has mentioned).I think that the C:N ratio of 5:1 is difficult to achieve(I have not comeacross in literature).It can be around 10:1.Because of gut enzymes and also microbiological activty the mineralization of N is fast and high in the gut .But the mineralized N can not be 90% of the total N in the vermicompost.It is also reported that the nitrate N content will be much higher than ammoniacal N(because of nitrification process).In one example from USA, the total N in vermicompost was 3.81%.The nitrate N was 4871 mg/kg and ammoniacal N 139 mg/kg.Total mineral N is 5010mg/kg or 5g/kg. Mineral N as a proportion of total N 3810:5.So mineral N can not be so high.However I am not familiar with the methods used for estimating total N and the mineral N by Mr.Thien.He can give more details of methods used.
Allen, John. 2016. Vermicomposting Guide H-164. New Mexico State University.
What stands out is Vermicompost in terms of pH is slightly acidic with pH 6.8 and leaf compost is quite alkaline pH7.8. In fact garden composts at this pH often give iron or manganese deficiency. Since this a log scale the difference is 10 times. Another major difference is vermicompost has 6 times the nitrate. Three times the electroconductivity and twice the TKN, Zinc, and Calcium and 50% more Potassium and Boron. A demonstratable superiority in standard grow mixtures are seen with as little as 5% vermicompost according Dr. Rhonda Sherman North Carolina State University.
Nice response Paul...
Here is an excellent review on vermicompost and its varied crop response...
Possible contribution of vermicompost on nutrient composition of plants
In order to produce a good crop, macronutrients available in the soil should be in the range of N (0.1 to 0.5%), P (0.08 to 0.5%), K (1.5 ti 3.0%) (Dutta, 2005). Adequate P is characterized by improved crop quality, increased root growth and earlier crop maturity (Grusak and DellaPenna, 1999). Although macronutrients such as Ca and Mg are used in smaller amounts, they are just as important to profitable crop production as the N, P and K. Exchangeable Ca in soils range 12 to 75% of CEC whereas exchangeable Mg in soils range 4 to 20% of CEC (Eckert and McLean, 1981). Magnesium is involved in numerous physiological and biochemical processes activating more enzymes than any other mineral nutrient, thus, making a significant contribution to plant growth and development (Epstein and Bloom, 2004). Calcium plays an important role in a wide range of physiological and biochemical processes in plants including the adjustments of ethylene responses in plants (Zhang et al., 2002), fruit ripening (Ferguson, 1984), flower senescence and flower abscission (Glenn et al., 1988). Micronutrients such as Fe, Cu, Zn, Mn, Mo and B assist in the formation of chlorophyll, cell division and growth, carbohydrate formation, as well as the maintenance of the plant’s enzyme system (Follet et al., 1981). Therefore, the type of organic or inorganic fertilizers used in agriculture with different quantities of macro and micronutrient has a significant effect on the nutrient value of the plants consumed.
PDF enclosed for further reading ...
May be the nitrogen analysis process had problem as you suspect and on the other side consider if there was any incorporation of N-fixers through plant residues while vermicomposting which might have increased the nitrogen % by absorbing atmospheric N?
As mentioned by Drs. Tarafdar and Hepperly the vermicompost may contain higher amount of nitrate-N compared to other manures.The following references may be consulted.An evaluation of vermicompost as a fast acting nitrogen amendment to mitigate nitrogen deficiencies in organic vegetable production. Master Thesis May2015 Peter Dalton Austin The University of Vermont.
scholarworks.uvm.edu/cgi/viewcontent.cgi?article=1504&content=graddis
Nitrogen transformations as affected by application of nitrogen and vermicompost in the presence of herbicide:A review Sheoran,H.S. and Duhan,B.S.International Journal of Emerging Technology and Advanced Engineering 4,(11)December 2014.
http://www.ijetae.com/files/volume4issue11/IJETAE_1214_78.pdf
20 State-of-the-art and new perspectives on vermicomposting research by Jorge Dominguen
Jdguez.webs.uvigo.es/wp-content/uploads/2011/10/ewecologychapter.pdf
The nutrient composition of vermicompost is so varying , if different substrate is feed by one species of earthworm. Here is an abstract ..
Abstract ; In this experiment, earthworm, Eudrilus eugeniae was fed with different plant residues: grass clippings, sago waste and rice straw. These organic wastes were also left to decompose naturally as the control. Analysis on samples vermicompost showed that humic acid content was highest in rice straw, followed by grass clippings compared to those of sago wastes. Total phosphorus (P) was lower in vermicomposts as compared to the controls, however, highest extractable P was found in rice straw vermicompost (0.33 ± 0.00 g/kg). Sago waste vermicompost (22.79 ± 0.01 g/kg) contained highest total calcuim (Ca) compared to the grass clippings (1.39 ± 0.01 g/kg) and rice straw (8.22 ± 0.06 g/kg) vermicompost. Significant positive correlations between nutrient contents in raw plant residues and vermicompost were observed for total nitrogen (N) (r = 0.779), potassium (K) (r = 0.998) and Ca (r =0.997). The study showed that nutrient in initial wastes material affects the nutrient contents of vermicompost. This research suggested that among the plant residues studied, vermicomposting of rice straw produced vermicompost with the highest plant extractable nutrient contents.Source : Yan et al., African Journal of Biotechnology Vol. 12(17), pp. 2207-2214, 24 April, 2013 .PDF enclosed for further reading
Some vermicomposts have pH as high as 8.77 ( PDF enclosed ) , while others are buffered around 6.5. Do we need to acidify such composts ..? What are the defined quality parameters of quality vermicompost in terms of salt index..?
I do not know what the defined parameter in terms of pH and salt index for vermicompost.is. I do have some observations which might be useful however. . In the Spanish study the humic acid percentage for vermi products were very high. In the study of Khan which had the outlier of very high pH the pea growth of pit compost improved growth 20% while the vermicompost being the most salty and highest pH had the best growth with an increase of pea growth of 80% four times that increase of pit compost. We might put out there as a hypothesis that the effects of vermicompost above the levels of control and pit compost in a measurement of apparently high salt and pH might be explained by the protective and promoting effect of humic acid content and action of vermicompost material. Compared to the other tests this very high pH might well be an outlier. The work at New Mexico show worm compost or manure is only slightly acid and that more alkalinity is associated with pile garden compost. Just some thoughts. I have used the traditional garden compost and have found it can immobilize Iron and Manganese because of its pH but have used vermicompost and never experienced that issue. optimum pH for growth media is about 6 to 7 pH based on the influence on Phosphorus solubility. and allowing sufficient micronutrient available in most cases. When we use highly acidic or alkaline materials their use will modify our pH in ways that can be disruptive. When we bring soils and media to neutrality and then use neutral pH materials the issues of pH become less pressing for the agriculturalist. I urge us all to key tabs of pH because it has such pervasive impact on plant growth through nutrient availability.
Dear colleagues,based on published literature especially based on long term studies,one need not worry for pH increases in soil due manure/compost /vermicompost application(though manur/compost may have initial neutral to slightly alkaline pH).Three changes in soil pH are conspicuous with manure/compost application.In acid soils pH may increase because of complexing of exchangeable Al by organic acids or humic substances.Basic cations (Ca and Mg) may also play role in increasing pH.In soils having pH 6-7 range no conspicuous change is noticed over long term.In slightly to moderately alkaline soils the pH may decrease.The decrease in pH may be due to organic acids produced through degradation of organic compounds added with organic manures and CO2 generated from root and microbial activity leading to formation of H2CO3 formation.Undecomposed poultry litter may increase the soil pH due to addition of basic cations,ammonification and production of NH3 during decomposition of the added litter.Also moderate rates of manure may not increase EC but heavy rates may increase the EC of soils.
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