production under arid conditions is hydroponics. Hydroponics is a technology that
allows the production of crops in soilless systems using a balanced liquid nutrient
solution. In hydroponic systems, the source of nutrients is mainly chemical inorganic
fertilizers, which are usually very expensive and beyond reach of resource-poor
farmers, especially in developing countries (Aboutalebi et al. 2013; Mowa 2015).
Research focusing on generating optimized organic nutrient sources utilizing abundant animal (goat, cow and donkey) manures that can be effectively used in
hydroponics can be crucial in enhancing adoption of hydroponics even amongst
the resource-poor farmers. Research on organic nutrient sources in hydroponics is
currently very limited. Table 18.4 summarizes some of the research that has been
done so far.
As highlighted in Table 18.4, though several researchers have attempted to make
use of different organic nutrient sources in hydroponics, there is still paucity of
information on the development of an optimized organic nutrient formula. Despite
being a great challenge, a holistic approach that considers the following (1) the
nutritional composition of the organic materials used, (2) optimization and standardization of organic nutrient solution method of preparation and (3) development of
effective models can allow researchers to predict final nutrient composition of
organic nutrient solutions, as proposed by Son and Okuya (1991). Research that
optimizes organic hydroponic solution preparation and utilization is required to
allow for adoption of these cheaper nutrient solutions.
In generating organic nutrient sources, one technology highlighted already with
ability to enhance nutrient mineralization, creating a nutrient-rich final product, is
vermicomposting (Bhat et al. 2017; Garcia-Sanchez et al. 2017). However, during
vermicomposting research, most researchers have focused on the nutrient composition of the solid vermicompost itself (Malinska et al. 2017; Mupambwa et al. 2016),
with limited interest in the vermi-leachate. During vermicomposting, excess water
called vermi-leachate or vermi-wash can be collected. Unlike nutrient solutions
produced directly from organic substances such as biogas digestates, vermileachates have great potential as effective nutrient sources in soilless crop production, due to their superior quality. These vermi-leachates are superior as they contain
significant concentrations of macro- and micronutrients, several enzymes, plant
growth hormones and can also increase plant disease resistance (Verma et al.
2017; Quaik et al. 2012). However, very limited studies have been carried out to
evaluate the potential organic nutrient value of vermi-leachates, particularly in
hydroponics (Quaik et al. 2012). Furthermore, the nutrient quality of vermi-leachates
is highly dependent on factors such as chemical composition of original organic
materials, vermicomposting process and moisture content of the vermicompost.
Integrated research that involves optimization of the vermicomposting process,
identifying optimum organic materials and vermicompost leaching frequency can
allow for the development of commercially effective vermi-leachates as liquid
fertilizers (Quaik and Ibrahim 2013). Research in this direction will be crucial in
driving the adoption of cheap nutrient sources for hydroponics among resource-poor
in developing countries.
18 Some Perspectives on Vermicompost Utilization in Organic Agriculture
321
allows the production of crops in soilless systems using a balanced liquid nutrient
solution. In hydroponic systems, the source of nutrients is mainly chemical inorganic
fertilizers, which are usually very expensive and beyond reach of resource-poor
farmers, especially in developing countries (Aboutalebi et al. 2013; Mowa 2015).
Research focusing on generating optimized organic nutrient sources utilizing abundant animal (goat, cow and donkey) manures that can be effectively used in
hydroponics can be crucial in enhancing adoption of hydroponics even amongst
the resource-poor farmers. Research on organic nutrient sources in hydroponics is
currently very limited. Table 18.4 summarizes some of the research that has been
done so far.
As highlighted in Table 18.4, though several researchers have attempted to make
use of different organic nutrient sources in hydroponics, there is still paucity of
information on the development of an optimized organic nutrient formula. Despite
being a great challenge, a holistic approach that considers the following (1) the
nutritional composition of the organic materials used, (2) optimization and standardization of organic nutrient solution method of preparation and (3) development of
effective models can allow researchers to predict final nutrient composition of
organic nutrient solutions, as proposed by Son and Okuya (1991). Research that
optimizes organic hydroponic solution preparation and utilization is required to
allow for adoption of these cheaper nutrient solutions.
In generating organic nutrient sources, one technology highlighted already with
ability to enhance nutrient mineralization, creating a nutrient-rich final product, is
vermicomposting (Bhat et al. 2017; Garcia-Sanchez et al. 2017). However, during
vermicomposting research, most researchers have focused on the nutrient composition of the solid vermicompost itself (Malinska et al. 2017; Mupambwa et al. 2016),
with limited interest in the vermi-leachate. During vermicomposting, excess water
called vermi-leachate or vermi-wash can be collected. Unlike nutrient solutions
produced directly from organic substances such as biogas digestates, vermileachates have great potential as effective nutrient sources in soilless crop production, due to their superior quality. These vermi-leachates are superior as they contain
significant concentrations of macro- and micronutrients, several enzymes, plant
growth hormones and can also increase plant disease resistance (Verma et al.
2017; Quaik et al. 2012). However, very limited studies have been carried out to
evaluate the potential organic nutrient value of vermi-leachates, particularly in
hydroponics (Quaik et al. 2012). Furthermore, the nutrient quality of vermi-leachates
is highly dependent on factors such as chemical composition of original organic
materials, vermicomposting process and moisture content of the vermicompost.
Integrated research that involves optimization of the vermicomposting process,
identifying optimum organic materials and vermicompost leaching frequency can
allow for the development of commercially effective vermi-leachates as liquid
fertilizers (Quaik and Ibrahim 2013). Research in this direction will be crucial in
driving the adoption of cheap nutrient sources for hydroponics among resource-poor
in developing countries.
18 Some Perspectives on Vermicompost Utilization in Organic Agriculture
321