It is well known that most plants’ roots require an adequate and continuous supply of oxygen in soil to respire, grow,
develop, and function normally. Industrial agriculture has developed rapidly but is accompanied by excessive irrigation and
fertilization, minimal tillage and agricultural machinery driving over the soil. All these farming activities can result in soil
compaction. In compacted soil, the increase in soil bulk density and the accompanying decrease in porosity can hinder the
exchange of oxygen, carbon dioxide and other gases between the atmosphere and the soil, thereby causing hypoxic stress in
plant roots. In addition to compaction, some natural factors, such as extraordinarily high groundwater table, long-term rainfall
and tillage under clay or clay loam conditions, can often lead to soil oxygen content reduced, which limits crop yield and
quality improvement. Tomato plants (Solanum lycopersicum) are one of the most vulnerable mesophytes to hypoxia in the root
environment. Soil aeration has been found to be very useful in overcoming problems associated with hypoxia in the root-zone
of irrigated crops including tomato, cotton, cucumber and zucchini. Over a range of soil water contents and soil types, the
performance of crops can be improved under oxygen-deficient conditions. It is hypothesized that varying the aeration volume
and burial depths of drip irrigation tubes (aeration position) would result in the different soil air environment in the root-zone.
To date, there are no reports in the literature which specifically examined the sensitivity of tomato plants to soil aeration
volume and burial depths of drip irrigation tubes in Lou soil, and the effect on the photosynthetic characteristics and dry matter
accumulation. The experiments were conducted in a greenhouse at Yangling (E108°02′, N34°17′), Shaanxi, between October,
2014 and May, 2015. The tested variety of tomato was Fenyuyanggang (New Horizon Facilities Agricultural Development Co.
Ltd., Northwest A&F University, China). Air was used for soil aeration, and the soil for the test was a silty clay loam (soil
order was Inceptisol based on the USDA (United States Department of Agriculture) soil taxonomy). The volume of air in each
plot was injected into the drip tubing via a manifold connected to the air compressor. The experiment was designed to study
the responses of photosynthetic characteristics, chlorophyll content and dry matter accumulation of greenhouse-produced
tomato to 4 aeration volumes in combination with 2 depths of drip-tubing placed in the soil. The drip irrigation placement
depths were respectively 15 and 40 cm below the surface of the ridge. Artificial aeration treatments were 0, 24.6, 49.4 and
74.2 L/m2, respectively. Results showed that drip tubing placement and artificial aeration treatments significantly affected
photosynthetic characteristics, chlorophyll content and dry matter accumulation. The changing trend of net photosynthetic rate
showed an increase at first and then a decrease with the increase of aeration volume at both 15 and 40 cm depth of the tube.
Chlorophyll a and dry matter accumulation of tomato also showed an increase firstly and then a decrease with the increase of
aeration volume at 15 cm depth of the tube. However, chlorophyll a and dry matter accumulation increased with the increasing
of the volume of aeration at 40 cm depth of the tube. Synthesizing each kind of situation, both 15 and 40 cm depth of the tube
could apply to artificial soil aeration. The optimum artificial aeration volume was 49.4 L/m2 at the 15 cm deep of the tube.
However, at the 40 cm deep of the tube, 74.2 L/m2 aeration volume was better than the other treatments. For the observed
responses, the information on how the tomato adapts to artificial soil aeration will provide guidance for field production
practices as well as indications of possible mechanisms.