On or off the ground
Many substrates are constituted by a mixture of particles with different sizes, being of fundamental importance the granulometric characteristic of the materials, since the size of the particles affects the growth of the plants through the size of the pores.
In October of 2009 the results of the study were announced: "Elaboration of specialized substrates for agricultural use, from bioprocessed organic waste", financed by the Fund for the Promotion of Scientific and Technological Development, Fondef, of Chile. This study was directed by Pablo Alvarado, from the University of Chile and was supported by eleven nurseries of fruit trees and vegetable seedlings, two companies that process organic waste and two service companies, among which were Agrocompost Ltda., Agrolab Ltda. ., Agromillora Sur SA, Agroorganic Mostazal Ltda., Biogram SA, Neopark, Plantec, Limagrain Seeds of Chile Ltda., Amancay Nurseries, Biotechnology Nurseries, El Tambo Nurseries Ltda., La Serena Nurseries, Los Olmos Nursery and San Jose Nursery and Nursery Sur, or Sociedad Agrícola Pehuén de Curicó SA
In this study, which was carried out over three years (2004-2007), it was stated that the materials used in the country - at that time - as substrates for the production of fruit and horticultural plants did not possess appropriate qualitative characteristics for the propagation of materials high-value vegetables, which requires high productivity modern horticulture. In the text it is argued that the absence of specialized substrates for professional use, has prevented the fruit and vegetable nursery industry from having adequate substrates and that users solve the problem using poor quality materials or whose extraction causes serious environmental damage, or, resort to to imported high-cost materials.
In this context, with the problems described above, this study was carried out whose specific objective was to develop specialized agricultural substrates of controlled quality for different uses from bioprocessed agricultural and agroindustrial waste. The methodology contemplated a first phase aimed at ensuring the quality of raw materials, followed by a second phase of substrate development, to finish with a third phase of evaluation of the substrates prepared at the level of commercial nurseries.
Blueberries
The results of the project were the obtaining of raw materials of organic origin, stable, homogeneous and uniform throughout the year, and the elaboration at the pilot level, of formulas of specialized substrates for seven products, among them blueberries.
This work was a pioneer in research and development of organic substrates in Chile, delivering concrete results to the productive sector and contributing to the sustainability of the sector.
Regarding the specialized substrate for blueberries, it corresponded to a prototype of controlled quality and with expected stability, homogeneity and uniformity characteristics, to be used by nurseries for the propagation of blueberries. The main functional and productive difference of this prototype with respect to the competition - sustains the study - is the specificity of the product, “that will allow to obtain plants with better adaptation and resistance to adverse conditions, with a greater growth and development, and a better establishment in the field" The study characterizes the blueberry substrate prototype for its low bulk density (Da) and high porosity, associated with a high water retention capacity.
In the technology of the substrates, the factors that regulate the aeration are fundamental, so that the Da, the pore size distribution, the stability of the aggregates, and the relative distribution of the size of particles that make up the substrate, directly affect in a larger surface of the roots. The study concluded that "the plants that grow in the prototype substrate have a high number of shoots and a length such that, ultimately, determine plants with a large amount of foliage and very active apices, denoting the potential for elongation and branching of the plants. This, unlike plants that grow in other mixtures, that can reach a higher height, but only present a pair of buds or a single bud. The presence of large amount of foliage and number of active apices of the plants that grew in the prototype, is a very important characteristic in the commercialization of the same, since the buyer knows that a blueberry plant with a large amount of leaves, will result in a plant with earlier growth and development ".
Aeration and humidity
Today, after almost ten years of that study, the technology regarding substrates has not changed too much, the concept is the same. The most important variables in that and in any study are related to aeration and moisture retention. It is recommended, in the area of the roots, a proportion of the 30% of materials and an 70% of empty space, which will be occupied in equal parts by air and water, and the solid part of the substrate can be reduced to an 10%.
In this perspective there is a material that is an indispensable guest in the composition of any substrate, all other components may vary, according to specific needs, but pearlite is present in all or almost all variants. Of all the materials used for cultivation, expanded mineral perlite is the most important of all.
Perlite
Many substrates are constituted by a mixture of particles with different sizes, being of fundamental importance the granulometric characteristic of the materials, since the size of the particles affects the growth of the plants through the size of the pores.
The particle and pore size distribution determines the balance between the water and air content of the substrate.
According to the scientific literature, thick-textured materials, with a particle size greater than 0,9 mm, with large pores, greater than 100 um, retain small amounts of water but are well aerated. Fine materials, on the other hand, with particles smaller than 0,25 mm and pore sizes smaller than 30 um, retain large quantities of water that is not readily available and are poorly aerated, so the best substrate they advise is composed of medium texture material. thick, with a pore size distribution between 30 um and 300 um, equivalent to particles between 0,25 mm and 2,5 mm, which retains enough water and has an adequate air content.
We must also distinguish the two ways in which substrate materials retain moisture, and that basically are those that retain moisture only on its surface, such as gravel or sand, and those that store moisture inside, in the pores .
Perlite is a volcanic glass that has a high water content, between 2% and 5%, and has the uncommon property of greatly expanding when temperatures above 800 ° C are applied, due to the fact that the water contained in the interior vaporizes causing the material to expand tens of times over its original volume, giving rise to an inert and glassy material that maintains its ability to retain water, since this cellular structure is formed on the exterior by multiple fractured bubbles that They impart a large surface area to each particle, which allows it to retain up to five times its own weight in liquids, such as water, herbicides, fertilizers, fungicides, or other products used in plant growth.
Perlite is inorganic and sterile, because in its manufacturing process the temperature exceeds 800º C, so it is a material not contaminated with fungi or bacteria that could affect the root of the plant. It is a homogeneous product, because the size of the particle is uniform, unlike other natural rocks and other substrates, thus benefiting the even development of the plant.
It is an incombustible material, reducing the risk of fire during storage and is insulating, protecting the root of the plant from changes in temperature, acting as a retardant of root heating.
It is durable and neutral, the pH oscillates between 6.5 and 7.0, so it is compatible with any fertilizer solution without influencing the acidity or alkalinity of it, and does not contain salts that could influence the ionic and cation exchange of the In addition, it is inert, so it does not react with fertilizer solutions or form salts.
Perlite is a lightweight material and provides the root with a convenient means for its development and strengthening, avoiding the caking of the substrate and is very easy to handle, mixing well with other components such as coconut fiber, peat or other components of substrates for growing in pots.
Source: Blueberrieschile.cl - Blueberriesconsulting.com
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