Articles
Effect of sodium concentrations in the root environment on yield and fruit quality of soilless grown tomato with closed-loop irrigation system
Article number
1377_76
Pages
623 – 630
Language
English
Abstract
Soilless cultivation allows high water and nutrient use efficiencies when drainage water is recycled.
However, a full closed-loop irrigation system is not easily achieved.
Among other issues, the drainage water quality can be worsened when recirculated due to sodium (Na) accumulation, occurring when the Na input concentration is higher than the actual Na uptake concentration.
This is considered to be the main reason for growers to discharge part of the drainage water.
In the Netherlands, recycling of drain water is obligatory and in the 1980s, standards for the maximum acceptable Na have been established by the Dutch Water Authorities, allowing discharge of a certain rate of the drainage, to keep Na concentration sufficiently low.
However, as a result of recently strengthened regulations, the discharge of effluents is limited.
We explored the limits for Na concentration in the drain water, which reflects the situation in the root environment, by testing the effects of Na concentrations on yield and product quality in long-term tomato crops with closed-loop soilless cultivation.
The space for increasing the Na concentration in the drain water, when keeping the EC equal, was created by proportional reduction of the concentrations of other cations (K, Ca, Mg), but not lower than the minimum nutrient concentrations for the crop growth.
This was assumed to correspond to a nutrient EC value of 1.3 dS m‑1, while keeping the commonly recommended EC-level in the drain water at 3.8 dS m‑1. Two experiments with tomato in consecutive years were conducted, with 5, 15, 20 and 25 mmol L‑1 Na as target concentrations in the root environment.
No significant yield reduction or decrease of fruit quality parameters were observed.
The results show that it is possible to cultivate tomato with much higher Na than the hitherto prevailing limits, provided that the concentrations of the other cations in the drain water do not decrease below the minimum required for crop growth.
However, a full closed-loop irrigation system is not easily achieved.
Among other issues, the drainage water quality can be worsened when recirculated due to sodium (Na) accumulation, occurring when the Na input concentration is higher than the actual Na uptake concentration.
This is considered to be the main reason for growers to discharge part of the drainage water.
In the Netherlands, recycling of drain water is obligatory and in the 1980s, standards for the maximum acceptable Na have been established by the Dutch Water Authorities, allowing discharge of a certain rate of the drainage, to keep Na concentration sufficiently low.
However, as a result of recently strengthened regulations, the discharge of effluents is limited.
We explored the limits for Na concentration in the drain water, which reflects the situation in the root environment, by testing the effects of Na concentrations on yield and product quality in long-term tomato crops with closed-loop soilless cultivation.
The space for increasing the Na concentration in the drain water, when keeping the EC equal, was created by proportional reduction of the concentrations of other cations (K, Ca, Mg), but not lower than the minimum nutrient concentrations for the crop growth.
This was assumed to correspond to a nutrient EC value of 1.3 dS m‑1, while keeping the commonly recommended EC-level in the drain water at 3.8 dS m‑1. Two experiments with tomato in consecutive years were conducted, with 5, 15, 20 and 25 mmol L‑1 Na as target concentrations in the root environment.
No significant yield reduction or decrease of fruit quality parameters were observed.
The results show that it is possible to cultivate tomato with much higher Na than the hitherto prevailing limits, provided that the concentrations of the other cations in the drain water do not decrease below the minimum required for crop growth.
Authors
W. Voogt, T. Barbagli, N. Oud, D. Andrea, L. Bo
Keywords
recycling water, sodium, sodium accumulation, EC gap, greenhouse horticulture, nutrient solution, soilless culture, water quality, salinity
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