Abstract
Subirrigation of containerized vegetable crops is a promising strategy to increase water and nutrient use efficiency, however, the longer growing seasons for cultivation of vegetable species may cause marked changes in the physical and chemical substrate properties. This study determined the effects of the irrigation system, subirrigation vs. drip-irrigation, and the concentration of the nutrient solution on the substrate physical and chemical properties in containerized tomato plants. Plants were irrigated with solutions at concentrations of −0.072, −0.058 and −0.043 MPa. Root dry weight of subirrigated plants was decreased by 35% in the substrate top layer when the highest concentration was used. Substrate electrical conductivity increased while pH was acidified as solution concentration increased and from the bottom to the top substrate layers in subirrigated plants. Salts buildup was associated with increased concentration of oxalic and tartaric acids and pH acidification. The improved substrate physical and chemical properties in subirrigated plants were associated with higher fruit yield (11.0 kg per plant) provided nutrient solution concentration was reduced to −0.043 MPa; in contrast, the highest yield in drip-irrigated plants (10.1 kg per plant) was obtained when the solution concentration was −0.072 MPa. In conclusion, subirrigation with reuse of the nutrient solution is a promising strategy to reduce water waste through runoff and leaching as water use efficiency increases due to greater water retention properties in the substrate, the maintenance of an EC within a range the plants can tolerate, and a lower acidification of substrate pH.
Highlights
Greenhouse tomato production demands extensive water inputs to achieve high fruit yield and quality as surface/open irrigation systems are used; such systems waste vast volumes of water through runoff and/or leaching, resulting in low plant water use efficiency
Root dry weight was affected by the interaction between the irrigation method and nutrient solution concentration as well as by the irrigation method with the substrate layer
Thethe higher total pore space in the substrate of decreased aeration water retention higher total pore space in the substrate subirrigated plantsplants was associated with higher water water retention properties as there water of subirrigated was associated with higher retention properties as was therea higher was a higher retention capacity as a resultasofathe higher hardly available andwater total available water retention capacity result of the higher hardly water available and total water; available water; we did not detect effects on substrate aeration
Summary
Greenhouse tomato production demands extensive water inputs to achieve high fruit yield and quality as surface/open irrigation systems are used; such systems waste vast volumes of water through runoff and/or leaching, resulting in low plant water use efficiency. Gravitational forces move water and nutrients downwards from the top of the container [6], affecting air and water retention capacities [2] and resulting in salt buildup in the lower portion of the growing media profile [6]. Subirrigation systems are based on the upward movement of water (capillary action) from the lower portion of the growing medium profile to the top of the container [6,7], thereby allowing a more uniform distribution of the nutrient solution throughout the substrate profile. The capillary movement of the nutrient solution in subirrigated containerized-plants reduces compaction of the growing media when compared to surface irrigation systems [8,9,10]. Salt buildup in the upper layer of the medium negatively affects root and shoot growth, quality, and yield, especially in sensitive plants [7]
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