Optimalization of Oxygen Levels in Root Systems as Effective Cultivation Tool

Abstract

To investigate the influence of oxygen concentrations in the root system on plant development, young cucumber plants were grown during three weeks on stone wool blocks. A continuous flow of nutrient solution (0.75 L h-1), containing 0.5, 3.5 or 10 mg L-1 dissolved oxygen, was led through the substrates. Already after 3 days, the impact of the various oxygen levels in the root systems became evident. Plant development was reduced when plants were subjected to the lowest oxygen concentration. In time, increasing differences in leaf area were observed when plants were grown under different oxygen levels, showing largest leaf area at 10 mg L-1 oxygen. Also, root mass was significantly reduced when plants were grown under low oxygen conditions. Bacteria and other microorganisms that consume oxygen can reduce oxygen levels. Oxygen consumption was detected in samples that were taken at different places in greenhouses, e.g. irrigation water storage tanks, irrigation supply system and substrates. During the winter period, the contribution of microorganisms in oxygen consumption was low. However, in April oxygen consumption in the samples was significantly higher. Sometimes, oxygen in nutrient solution, present in the substrates, was fully consumed within 30 minutes, indicating that roots would suffer anoxia. Frequent refreshment of nutrient solution in the irrigation supply system had a major impact on oxygen levels. Continuous measurements showed that during the day oxygen levels in the irrigation system were high just after refreshment of the nutrient solution, but between two refreshments oxygen levels in the system dropped towards very low oxygen values. If technically feasible, in future the control of oxygen levels in root systems may become a new tool for growers to manage cultivation in horticulture, in addition to light, temperature, carbon dioxide, nutrition and water.

Oxygen enrichment of nutrient solution of substrate-grown vegetable crops under Mediterranean greenhouse conditions: oxygen content dynamics and crop response

“…However, we believe that further research is required to conf irm the effectiveness of this technique for commercial spring melon crops grown on rockwool slabs, including a better characterization of oxygen status and availability within the medium. The latter, could be achieved by increasing the number of measurement points and/or with continuous measurements (Holtman et al, 2005). By contrast, the absence of yield response to oxyfertigation in the melon crop grown on perlite grow-bags appears to be clear, as no differences were found between oxygen treatments for any of the oxygenation, growth and productivity parameters assessed.…”

“…No significant differences were found between oxygen treatments for any productivity parameter for the melon grown on perlite grow-bags (Table 3), whereas a significant 7% increase in total and marketable yield, associated with a higher fruit number, was observed for the oxygen enriched treatment grown on rockwool slabs. For hydroponically-grown vegetable crops, the critical Nutrient solution oxygen enrichment of substrate-grown greenhouse crops 1239 oxygen partial pressure of the nutrient solution was between 4-6% (Schapira et al, 1990;Morard, 1995), which corresponds to DO concentration values of around 3 mg L -1 (Gislerod and Kempton, 1983;Zeroni et al, 1983;Holtman et al, 2005). However, the critical DO value should be considered with caution.…”

Irrigation Strategies for Greenhouse Tomato Production on Rockwool

“…The reduction in the rate of transpiration in T3 and T4 relative to T1 and T2 could be the result of reduced water uptake, which might be attributed to inadequate oxygen availability for root respiration resulting from the presence of excess water (Holtman et al, 2005). On the other hand, a lower transpiration rate with T5 relative to T6 could be the result of excessive drop of water content in T5 (down to 50% to 55%) and the consequent water and salt stress.…”

Oxygenation of Irrigation Water during Propagation and Container Production of Bedding Plants

“…Pepper fruit yield was unaffected by water oxygenation and cucumber fruit yield was increased by oxygenated water in one of three trials. However, in some other published studies, oxygenation of nutrient solution has resulted in improved yield compared with plants grown in hypoxic to anoxic conditions, in addition to reduced root necrosis (Marf a et al, 2005), increased leaf area and root mass (Holtman et al, 2005), increased macronutrient uptake (Marf a et al, 2005), and increased shelf life in cucumber (Ehret et al, 2010) and pepper (Ehret et al, 2010;Marf a et al, 2005). For example, Lei et al (2016) found that corn yield increased by oxygenation of irrigation water for plants grown in a completely water-logged vermiculite substrate under warm water temperature (averaging 27.7°C), where DO in the ambient irrigation water at times decreased to 1 mg • L -1 in the substrate.…”