There's something you don't know about the selection of soilless solid substrates!

The use of solid matrix in soilless culture is an extremely important link.There are many kinds of solid matrix, such as coconut bran, peat, rock wool, vermiculite, perlite, bark, sawdust, sand, peat, rice husk, slag, ceramsite, various foam plastics, etc.The matrix can be used either alone or in combination.The suitable matrix can be selected according to the difficulty and price of material source.

(1) conditions for soilless culture substrate

1, to have a certain degree of water permeability and water retention.The permeability and water retention of matrix are determined by the size, property, shape and porosity of matrix particles.

2, non-toxic or does not contain toxic substances.The content of sodium ion and calcium ion should not be too high.

3. Stable chemical properties.When nutrient solution and water were added to the matrix, the pH and chemical properties of the matrix were stable.

4. Cheap and easy to get.

(ii) the role of matrix

1. Support anchoring plants.Plants are required to be rooted in a solid substrate and not to be buried or dumped.

Stay hydrated.

Breathe.There is a unity of opposites between air permeability and water holding in solid matrix, that is, when the air content in solid matrix is high, the water content is low, and vice versa.

4. Buffer effect.Buffering can make the environment of root growth more stable, that is, when foreign substances or some harmful substances produced in the process of root metabolism harm crop root system, buffering will dissolve these harms.

Physical properties of the matrix

The physical properties of substrates which have great influence on the growth of cultivated crops mainly include grain size, bulk density, total porosity, water holding capacity and pore ratio (gas-water ratio).

1, the particle size

The size of the substrate particle, usually in millimeters.The size of matrix particles directly affects the bulk density, total porosity and size porosity ratio of matrix.The finer the particles of the same matrix are, the smaller the bulk density is, the larger the total porosity is, and the smaller the pore ratio is.Therefore, the production requirements of the matrix particles should not be too thick, nor too fine.

2, bulk density,

Bulk density refers to the weight of a dry substrate per unit volume, expressed in grams per liter or grams per centimeter.The bulk density is mainly affected by the texture of the substrate and the size of the particles.The bulk density of matrix reflects the porosity and compactness of matrix.The bulk density of matrix varies greatly, and the bulk density of the same matrix is also greatly affected by the degree of compaction and particle size.

3. Total porosity

Total porosity is the sum of the water-holding and aerated pores in the matrix, expressed as the volume percentage (%) of the matrix.The total porosity can be calculated as follows:

Total porosity = (1 -- bulk density/specific gravity) 100%

The matrix with large total porosity is light and loose, which is conducive to the growth of crop roots. However, it has poor supporting and fixing effect on crop roots and is prone to lodging.The matrix with small total porosity is heavier and the total bulk density of water vapor is less.Therefore, the production practice is often several different particle size matrix mixed use.

4. Pore ratio

Macroporosity refers to the space occupied by air in the matrix, namely aerated pores.Small pores refer to the space occupied by the water fraction in the matrix, namely the water-holding pores.The ratio of aerated pores to water-holding pores is called the size porosity ratio.Can be expressed as follows:

Pore ratio = aerated pore (%)/water holding pore (%)

Aerated pores are generally defined as pores with a diameter of 0.Above 1 mm;Water-holding pores are generally defined as pores with a diameter of 0.00 l ~ 0.Pores within 1 mm.The size of the pore ratio can reflect the situation between water and gas in the matrix, usually the size of the pore ratio in the range of 1:1.5 ~ 4 crops can be good growth.