INTERNATIONAL SIMPOSIUM 1996 MICROFERTIGATION Dr. Andres Rrevalo Fuentes EURONOVEOHDES RCRICOLBS SPfllK
simposiuin internacional 199G HON. PRINCIPAL HDVflNTEGES RND DISRDVRNTRGES OF FER- ADVANTAGES: * Nutrition is regulating applying an equilibrium of adequate iones. * Tasks are made easy due to the eveness. * Precocity due to a higher growth. * Total control over nutrition (chelates and humic acids). * Easy handling and less danger in the use of fumigators by means of dripping DISADVANTAGES: * If there isn't a closed circuit, it will exist a lot of contamination due to nutrients lixiviation. * Root illnesses may appear due to the absence of a mechanism of defense in the substrates. * More precision is required in the feeding of the plant because certain errors can affect it. * High costs in the irrigating installation. C n m m «H D B A chelant agent is a substance that protects metal from blocking in the soil. 28
Simposium international 1996 NATURAL SOIL CHELANTS STANCES ISt. GROUP - Organic acids - Polyphenols - Amino acids - Peptides - Proteins - Polysaccharides SUB- 5.- Chelated metal in 95-9 6.- Special chelation EDDHMA SPECIAL CH ELET10 N E D H M R 2Nd. GROUP - Humic acids - Phulvic acids CHELATES CLASSES EDTA Ethylendiaminetetracetic acid DTPA Diethylenriaminepentaacetic acid HEDTA Hydroxide ethylendiaminetri acetic acid EDDHA Ethylendiaminehydroxidephenylacetic acid EDDHMA Ethylendiaminehydroxidemethylacetic acid CHARACTERISTICS OF THE CHETALES 1.- Solubility 2.- Stability with a basic ph 3.- Stability to Ca Mg 4.- Richness ORTO ISOMER [STRBLE] PflRfl ISOMER [LESS STRBLE] PRRH METRYL ROSORPTION OF IRON H Q NH? Apexes of the roots. The absorption of the nutrients has to be done through the apexes of the roots, that is why it is of interest that a good radical system be big enough as to absorb given to the soil. Releasing of H+. everything The root releases a substance 29
simposiuin internacional 199G made up H+, which reduces the ph of the zone near to the apex of the root and makes releasing chelate of the salt, being absorb by the plant. VEGETAL MHTERIflL Very slow absorption. Depending on the chelation of the salt and the number of available roots, the absorption will be more or less slow. Oxide Reduction Process. Fe +3 Fe +2 When the process of oxide reduction is produced, the absorption, especially of iron, is solwer. Foliar means: Photodescomposition process. Through foliar means the process of separation of the chelate and the salt is by photodescomposition, when contact with light the chelate is descomposed. HUMIC ACIDS Brown - nearly polimerized Insoluble in an acid medium Soluble in an alkaline medium PHLUVIC ACIDS Gray - Very polimerized Soluble in an acid medium CHELATE ABSORPTION BY THE PLANT j j j j ^ ^ J I CULTURE nus 0RPJI0N T. Iron Tomato 8 % - 24 Hours Manganese Tomato 24-36 Hours Zinc Tomato 24 Hours HUMINE Isoluble in any medium (Not very known). Very difficult to extract due to the strong binding with the clays. CRENIC ACIDS Water soluble phluvic acids HIMATHOMELANIC ACIDS Alcohol soluble humic acids NOTE: The alkaline salts (HUMATES- PHULVATES) are soluble in water. 30
simposiuin internacional 199G HUMIC HCIDS CHHRHCTEHISTICS GROUND LEVEL GROUND LEVEL Color: The dark color is due to the humic chemical compounds rich in conjugated double bonds, that absorb more efficiently the infrared rays favoring the heatin of the soil. STRUCTURE: Humic substances have a bonding capacity with the inorganic particles of the soil, forming aggregates of a certain stability. The formation of these aggregates and its stability helps heavy soils to be less dense y those that are lighter more compact. The ideal dimensions of these aggregates fluctuate between 1 to 5 mm., being inconvenient and secondaries in humid and rainy zones. HYDRIC RETENTION CAPACITY: Humic substances besides contributing to the increase of the capacity of hydric retention of the soil through out the formation of aggregates, as we have seen before, have the capacity to imbibe and retain great quantities of water due to its coloidal properties and its possibility to form water and hydrogen bonds that will parcially be disopose off later. CATIONIC EXCHANGE: Another property of the huminc substances is that of improving the capacity of exchange of the cations of the soil, this property consists in the absorption of cationic nutrients from the soil (H+, K+, NH4+, Ca, Mn, Al, Fe, and Fe+++), having them later disposed to plants. In this way, the lost of these can avoided by lixiviation or by unassimilability. The humates and phluvates, rather than the clays, have an important capacity to bond and retain anions (N03,-, SO-, CI, OH, PO, P04-, P04-) per having amino and amido groups, pestidic bounds and other nitrogened groups. These anions well bond directly or through a metal, in the case of phosphates, are easily assimilated by the plant whenever needed. SOLUBILITY: The insolubility of the humic substances is due greatly to its association with clays and also that the salts that forms with di- and tri-valent metals are insoluble; the result is a small portion lost of this material by means of lixiviation. TAMPON ACTION: Humus presents a tampon action in slightly acids, neutral and alkaline soils, maintaining the soil a uniform reaction. 131
simposiuin internacional 199G COMPLEXING AND CHELATING: Humic acids have the possibility to form complexes and chelates relatively stable with polivalent cations like Cu++, Mn++, Zn, ++Fe++, etc., increasing the possibility to be assimilated by the plants. MINERALIZATION: The degradation of humic substances in the soil brings with it the libeartion of C02, H20, N02,. ORGANIC MOLECULE COMBINA- TION: This property acts upon the bioactivity, persistance and biodegradability of pesticides, modifies the proportion of its applications and effectiveness, due basically to the actions that the humic substances have upon the plant, specially, permeability and translocation. BIOLOGICAL ACTION: The humic acids act directly over bacterias or nitrogen fixers and increase the biological fertility of the soil. RADICLE SYSTEM: Humic substances can have a physiological effect over plants. This way, humic and phulvic acids can have a rizogenetic action, promoting the development and growth of roots and radical filaments, increasing thus the radicle surface. PERMEABILITY - RESPIRATION: It has been demonstrated that humic acids and its derivatives increase the permeability of the membrane of the plant's roots, providing thus the absorption of nutrients. PHYTOHORMONAL ACTION: It is also been observed that the humic fraction has certain auxinic action providing vegetable development. WATER ABSORPTION EFFECT: It has been demonstrated that humates have a stimulating effect over the transportation of water in the plant and induces a plant to have a larger content of humidity and a slower lost of water. PLANT LEVEL GERMINATION: Humic and phulvic acids stimulate the germination of a great number of seeds. The immersion of seeds in a sodic liumate solution increases the germination velocity. CHLOROPHYLL, CHLOROSIS AND PHOTOSYNTHESIS: Humic compounds increase the contents of chlorophyll in the plants, and prevent and correct chlorosis due to the stimulation over the radicular ansorption of iron and the translocation of this element to the leaves. Also it has been demonstrated a positive effect over the photosynthetic 32
simposium international 199B activity, through a major consumption of carbonic anhydride. SUGAR CONTENTS EFFECTS: The resistance to the withering of the plants that it is developed in the presence of humic acids is due to the increase of an osmotic pressure in the cell by the intracellular accumulation of sugar reducers. VEGETABLES RIPENESS EFFECTS: It acts on the ripeness without altering the normal growth of the plant.