Beneficial Role of Humic Acids

	Back to Home
Organic Matter Decomposition Degradation of Plant Residues Humus Genera of Microorganisms Capable of Utilising Different Components of Organic Matter Humic Acids Beneficial Role of Humic Acids

Beneficial Role of Humic Acids

Beneficial Role of Humic Acids
The benefits of humic substances are reflected in improved seed germination, root growth, uptake of minerals by plants and other physiological effects on plant growth. Optimum levels of sodium humate are known to increase the percentage of germination of seeds in wheat, maize, gram, peas and beans. Root growth in tomato plants has been shown to be increased by the application of humic and fulvic acids at low concentrations. There are several reports to show that mobilization of N, P and K from the soil into the root system is increased in the presence of humus substances. The application of humic acid to soil is also known to decrease phosphorus fixation in soil, particularly in calcareous soil.

The uptake of trace elements by plants is increased by the application of humus substances since the latter is known to effectively chelate with trace metals, especially iron. A combination of fulvic acid and iron is known to be more effective in increasing lateral root formation in plants than iron alone. The chelating ability of humates suggests that they playa role similar to EDTA (ethylene-diamino tetraacetic acid), the well-known synthetic chelator.

Enzyme actions involved in plant metabolism have been linked with humus complexes since humic acids function as hydrogen acceptors. The growth stimulatory activity of humus complexes on wheat roots has been attributed to the noticeably increased cytochrome oxidase activity in the root system.

Similarly, humic acids are known to increase the activity of glutamic acid transaminase and phosphorylase enzymes and also the synthesis of deoxyribose and ribose nucleic acids. Several reports indicate a shift in carbohydrate metabolism of plants mediated by changes in aldolase, saccharase, phosphatase and amylase by the application of humic acids. Apart from the chelating effect of humic acids on trace elements, the beneficial influence of humic acids on iron uptake by roots may also be attributed to the permeability changes in the plasma membrane as is evident from several experiments with plants grown on mineral solutions supplemented with humus substances. Experiments with foliar sprays of sodium humate have shown that the vigour and yield of certain plants can be enhanced by such treatments.

Effect of spraying sodium humate and hydroquinone on grain yield and nitrogen uptake by Glycine max var. Bragg and on yield of Solanum lycopersicum var. Heinz, 1370 (Average of four replications; from Varshney and Gaur, 1974)

Treatment	Soybean Grain		Tomato
	Yield/plot (g)	Nitrogen (%)	Nitrogen plot uptake (g)	Yield/plot (g)
Control	200.7	6.23	12.5	661.7
Hydroquinone 10 ppm	218.5	6.15	13.4	1309.7
Hydroquinone 50 ppm	209.2	6.50	13.6	798.9
Humate 10 ppm	248.4	6.50	16.4	1383.4
Humate 50 ppm	229.0	6.60	14.6	1347.4
C.D. at 5%	6.17			157.9

Humic acids are known to influence the growth and proliferation of microorganisms. The growth of Aspergillus niger, Penicillium glaucum, Bacillus mycoides and Scenedesmus spp. is enhanced by additions of humus substances. The number of Azotobacter cells and the amount of nitrogen fixed by them are enhanced by the application of humic acid. Similar beneficial effects have also been noticed on the growth of Rhizobium and nodulation of legume roots inoculated with R. trifolii, R. meliloti, R. leguminosarum and R. japonicum. In fact, legume inoculants containing viable cells of rhizobia intended for artificial inoculation of leguminous seeds are often prepared on humus-type materials.

	Back to Home
Mineralization and Immobilization Process Effects of Residues of Crops on Plant Growth Soil Sickness Composting Vermicomposting Green Manure Anaerobic Decomposition of Organic Matter Biogas Degradation of Hydrocarbons

Home | Site map | Submit Article | Directory | Search