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אסיף מאגר המחקר החקלאי
פותח על ידי קלירמאש פתרונות בע"מ -
Substrates and their analysis
Year:
2002
Authors :
בר-טל, אשר
;
.
זילבר, אבנר
;
.
רביב, מיכאל
;
.
Volume :
Co-Authors:

R. Wallach - The Seagram Center for Soil and Water Sciences, Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, ISRAEL

Facilitators :
From page:
25
To page:
101
(
Total pages:
77
)
Abstract:

Overall profitability of intensive (especially greenhouse) crops, grown in soilless substrates, is higher than those grown in soil. This is due to their superior physical and chemical properties, to their initial low infestation rate with pathogenic pests and due to their ease of disinfestation among growing cycles. The result is a worldwide rapid expansion of the use of substrates during the last decades. This chapter deals with the physical properties of substrates and their effect on irrigation regime and with the chemical properties of substrates and their effects on plant mineral nutrition. It also describes the main substrates that are currently in use and the way they are analysed. High content of available water and an adequate air supply have been considered as the most important physical characteristics required for container media in order to achieve optimal growth. Water availability to plant roots is strongly related to the hydraulic conductivity characteristics of the medium, which, in porous materials, drop dramatically with reduction in water content. Very high water content (near container capacity) is, thus, a prerequisite for optimal water availability. Means to maintain desired water content are discussed. The main factor that distinguishes fertilisation management of substrate- and soil-grown plants is the limited volume of substrates, which means a lower buffer capacity for pH and solution composition and a limited supply of nutrients. The limited root zone volume also results in decreased root size and increased root density, causing higher competition among roots and a bigger effect of root activity on the rhizosphere. Most growth substrates possess negative permanent and/or variable charged surfaces. Surface charge properties of substrates have a major effect on the chemical reactions taking place in the rhizosphere, on the availability of applied cations and on their uptake efficiency. Strong interaction between orthophosphate ions and solid phase constituents reduce solution P concentrations following fertilizer application. The main two mechanisms involved are: (i) fast - electrostatic reactions of adsorption onto the solid phase; and (ii) slow - formation of new solid metal-P compounds (precipitation). Thus, availability of phosphorus in the rhizosphere often determines the growth and productivity of crops. Frequent irrigation and continuous fertilisation should satisfy nutritional plant demands under most practical situations.

Note:
Related Files :
hydroponics
soilless culture
עוד תגיות
תוכן קשור
More details
DOI :
Article number:
0
Affiliations:
Database:
גוגל סקולר
Publication Type:
פרק מתוך ספר
;
.
Language:
אנגלית
Editors' remarks:
ID:
44509
Last updated date:
02/03/2022 17:27
Creation date:
30/10/2019 15:03
Scientific Publication
Substrates and their analysis

R. Wallach - The Seagram Center for Soil and Water Sciences, Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, ISRAEL

Overall profitability of intensive (especially greenhouse) crops, grown in soilless substrates, is higher than those grown in soil. This is due to their superior physical and chemical properties, to their initial low infestation rate with pathogenic pests and due to their ease of disinfestation among growing cycles. The result is a worldwide rapid expansion of the use of substrates during the last decades. This chapter deals with the physical properties of substrates and their effect on irrigation regime and with the chemical properties of substrates and their effects on plant mineral nutrition. It also describes the main substrates that are currently in use and the way they are analysed. High content of available water and an adequate air supply have been considered as the most important physical characteristics required for container media in order to achieve optimal growth. Water availability to plant roots is strongly related to the hydraulic conductivity characteristics of the medium, which, in porous materials, drop dramatically with reduction in water content. Very high water content (near container capacity) is, thus, a prerequisite for optimal water availability. Means to maintain desired water content are discussed. The main factor that distinguishes fertilisation management of substrate- and soil-grown plants is the limited volume of substrates, which means a lower buffer capacity for pH and solution composition and a limited supply of nutrients. The limited root zone volume also results in decreased root size and increased root density, causing higher competition among roots and a bigger effect of root activity on the rhizosphere. Most growth substrates possess negative permanent and/or variable charged surfaces. Surface charge properties of substrates have a major effect on the chemical reactions taking place in the rhizosphere, on the availability of applied cations and on their uptake efficiency. Strong interaction between orthophosphate ions and solid phase constituents reduce solution P concentrations following fertilizer application. The main two mechanisms involved are: (i) fast - electrostatic reactions of adsorption onto the solid phase; and (ii) slow - formation of new solid metal-P compounds (precipitation). Thus, availability of phosphorus in the rhizosphere often determines the growth and productivity of crops. Frequent irrigation and continuous fertilisation should satisfy nutritional plant demands under most practical situations.

Scientific Publication
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