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[AGE27-P15] Water Distribution in Tomato Grown Rockwool and Coconut Coir in Tropical Region
Keywords:rockwool, coconut coir, drip irrigation, greenhouse, yield
Rockwool, instead of soil, has been used for growing tomatoes and leafy vegetables
in a greenhouse. Recently, rockwool which is industrial waste after growing season is getting
replaced with coconut coir since the carbon cycle by using organic material is enhanced.
Greenhouse is not common practice in tropical area since cooling and dehumidifying, due to
hot and humid weather, should be essential and moreover construction materials are too costly.
Therefore, irrigation management is not established for greenhouse in tropical regions. We
investigated the relationship between water distribution in growing medium, rockwool and
coconut coir, irrigated by drip irrigation, to obtain an irrigation manual for a side-opened
greenhouse in tropical Indonesia.
We grow cherry tomatoe in a rockwool cube placed on coconut coir substrates (Fig.
1) in the side-opened greenhouse. Seedlings begin 30 days after sowing were transplanted to
rockwool cubes. Tomato was irrigated automatically hourly with liquid fertilizer containing
nitrogen, phosphorous, and potassium by drip irrigation system from sunrise to sunset. Liquid
fertilizer concentration was varied according to plant growth stage. Irrigation amount (Ir) was
applied equally from the beginning of October in 2022 until beginning of December in 2022
and converted to 25%, 57%, 100%, 114%, and 142% of local commercial cultivation. Tomato
fruits harvesting period was from beginning to end of December in 2022, and the frequency
was 1-2 times a week. Volumetric water content were measured using TEROS-12 (Meter
Group Inc., US) horizontally installed in the middle of the rockwool cube called “cube” as
shown in Fig. 1. Similarly, the sensor was employed in the coconut coir substrate at called
“center” and “slub” where are between rockwool cubes and under the rockwool cube,
respectively (Fig. 1).
We compared volumetric water content at each measured location in each Ir
treatment (Fig.2). The time changes in volumetric water content at each measured location
differed in each Ir treatment, and larger Ir did not show higher values. Fig.3 shows time
variation of relative volumetric water content to measurements at each Ir treatment on the
day irrigation trial was started. The relative values at each measured location drifted stably
between 0.8 and 1.2. Those results stated above shows that the volumetric water content at
each measured location changes stably whereas the volumetric water content at each
measured location is not same even if Ir is different. The volumetric water content in Ir of 25
and 57% eventually decreased after starting different irrigation applications. The volumetric
water content in Ir of 100, 114, and 142% was stable after different irrigation applications
began. Those results show that the proper Ir would be higher than 100% of local commercial
irrigation treatment. Still, a suitable irrigation amount could be higher than Ir of 57% or lower
than Ir of 100%. Fig 4 shows time series of fresh tomato fruit yield through harvesting. The
yield was not comparably different even after irrigation amount was changed. To conclude,
volumetric water content should be measured in different irrigation management in a
greenhouse, and longer havesting period should be examined to be found out the relationship
between irrigation amount and tomato fruits productivity.
in a greenhouse. Recently, rockwool which is industrial waste after growing season is getting
replaced with coconut coir since the carbon cycle by using organic material is enhanced.
Greenhouse is not common practice in tropical area since cooling and dehumidifying, due to
hot and humid weather, should be essential and moreover construction materials are too costly.
Therefore, irrigation management is not established for greenhouse in tropical regions. We
investigated the relationship between water distribution in growing medium, rockwool and
coconut coir, irrigated by drip irrigation, to obtain an irrigation manual for a side-opened
greenhouse in tropical Indonesia.
We grow cherry tomatoe in a rockwool cube placed on coconut coir substrates (Fig.
1) in the side-opened greenhouse. Seedlings begin 30 days after sowing were transplanted to
rockwool cubes. Tomato was irrigated automatically hourly with liquid fertilizer containing
nitrogen, phosphorous, and potassium by drip irrigation system from sunrise to sunset. Liquid
fertilizer concentration was varied according to plant growth stage. Irrigation amount (Ir) was
applied equally from the beginning of October in 2022 until beginning of December in 2022
and converted to 25%, 57%, 100%, 114%, and 142% of local commercial cultivation. Tomato
fruits harvesting period was from beginning to end of December in 2022, and the frequency
was 1-2 times a week. Volumetric water content were measured using TEROS-12 (Meter
Group Inc., US) horizontally installed in the middle of the rockwool cube called “cube” as
shown in Fig. 1. Similarly, the sensor was employed in the coconut coir substrate at called
“center” and “slub” where are between rockwool cubes and under the rockwool cube,
respectively (Fig. 1).
We compared volumetric water content at each measured location in each Ir
treatment (Fig.2). The time changes in volumetric water content at each measured location
differed in each Ir treatment, and larger Ir did not show higher values. Fig.3 shows time
variation of relative volumetric water content to measurements at each Ir treatment on the
day irrigation trial was started. The relative values at each measured location drifted stably
between 0.8 and 1.2. Those results stated above shows that the volumetric water content at
each measured location changes stably whereas the volumetric water content at each
measured location is not same even if Ir is different. The volumetric water content in Ir of 25
and 57% eventually decreased after starting different irrigation applications. The volumetric
water content in Ir of 100, 114, and 142% was stable after different irrigation applications
began. Those results show that the proper Ir would be higher than 100% of local commercial
irrigation treatment. Still, a suitable irrigation amount could be higher than Ir of 57% or lower
than Ir of 100%. Fig 4 shows time series of fresh tomato fruit yield through harvesting. The
yield was not comparably different even after irrigation amount was changed. To conclude,
volumetric water content should be measured in different irrigation management in a
greenhouse, and longer havesting period should be examined to be found out the relationship
between irrigation amount and tomato fruits productivity.