Core Ideas: Rhizosphere soil enzymes activity showed an initial increase followed by a decrease. Soil aeration can enhance the activities of three rhizosphere soil enzymes. Aeration frequency and volume can significantly affect rhizosphere enzyme activities. Aeration can enhance the activities of non‐rhizosphere soil enzymes. Soil aeration can increase tomato yield. Artificial soil aeration can enhance soil enzyme activity, improve soil nutrient cycling, and increase crop growth and yield. We studied the response of soil microorganisms and soil enzyme activity to two levels of burial depths of subsurface tubing in combination with four levels of aeration volume and three frequency levels of supplemental soil aeration. The aeration volumes ( V ) were 0, 0.5, 1, and 1.5 times (CK, V ₁ , V ₂ , and V ₃ , respectively) the estimated porosity of the plot rhizosphere. Burial depths ( D ) of subsurface tubing were 15 and 40 cm ( D ₁₅ and D ₄₀ ). Aeration frequencies ( F ) levels were none and at 2‐ and 4‐d intervals (CK, F ₂ , and F ₄ ). The results demonstrated that aeration frequency and volume positively affected soil urease, phosphatase, and catalase activity and soil microbial abundance. The impact of aeration treatment on rhizosphere soil enzyme activity was greater than its impact on non‐rhizosphere activity. When the drip irrigation tube depth was 15 cm, V ₂ volume with 2‐d aeration intervals led to an increase in the mean yield of first picking fruit of 75.1% compared with the unaerated control. When V ₃ volume with 2‐d aeration intervals was performed with a 40‐cm irrigation tube, the mean yields of the first picking fruit increased by 135.5% compared with the unaerated control. These results suggest that artificial soil aeration can improve the plant root zone environment, increase microbial abundance and soil enzyme activity, and promote nutrient uptake, thus promoting plant growth and fruit output.

Salt stress is one of the environmental factors that greatly limits crop production worldwide because high salt concentrations in the soil affect morphological responses and physiological and metabolic processes, including root morphology and photosynthetic characteristics. Soil aeration has been reported to accelerate the growth of plants and increase crop yield. The objective of this study was to examine the effects of 3 NaCl salinity levels (28, 74 and 120 mM) and 3 aeration volume levels (2.3, 4.6 and 7.0 L/pot) versus non-aeration and salinity treatments on the root morphology, photosynthetic characteristics and chlorophyll content of potted tomato plants. The results showed that both aeration volume and salinity level affected the root parameters, photosynthetic characteristics and chlorophyll content of potted tomato plants. The total length, surface area and volume of roots increased with the increase in aeration volume under each NaCl stress level. The effect was more marked in the fine roots (especially in ≤1 mm diameter roots). Under each NaCl stress level, the photosynthetic rate and chlorophyll content of tomato significantly increased in response to the aeration treatments. The net photosynthetic rate and chlorophyll a and t content increased by 39.6, 26.9, and 17.9%, respectively, at 7.0 L/pot aeration volume compared with no aeration in the 28 mM NaCl treatment. We also found that aeration could reduce the death rate of potted tomato plants under high salinity stress conditions (120 mM NaCl). The results suggest that the negative effect of NaCl stress can be offset by soil aeration. Soil aeration can promote root growth and increase the photosynthetic rate and chlorophyll content, thus promoting plant growth and reducing the plant death rate under NaCl stress conditions.

Biochar’s underlying biochemical and physiological mechanisms in reducing irrigation and salinity stress are elusive. This paper investigates the effects of two types of biochar (wood biochar and poultry biochar) on the growth and physiology of tomato seedlings exposed to the combined effects of drought and salinity stress. Two types of biochar, wood biochar (WB) and poultry biochar (PB), were added to the soil separately, with three salinity gradients of 0, 100, and 200 mmol/L and two water supply conditions of full irrigation (FI) and deficit irrigation (DI). Results showed that biochar addition effectively improved the root water potential and osmotic potential of tomato plant under drought and salinity stress. Biochar application also mitigated leaf relative water content by 9.86% and 24.37% under drought and salinity stress, respectively. Furthermore, biochar application decreased abscisic acid concentrations in xylem sap under drought and salinity stress. Biochar altered the soil structure and increased field water holding capacity, indirectly increasing the soil water supply. While water use efficiency did not increase significantly after biochar application, a synergistic increase in seedling growth and water consumption occurred. In conclusion, biochar addition shows promise for promoting seedling growth to help mitigate the adverse impacts of drought and salinity stress on plant growth and physiology.

This study investigated the effects of 4 aeration levels (varied by injection of air to the soil through subsurface irrigation lines) at two subsurface irrigation line depths (15 and 40 cm) on plant growth, yield and nutritional quality of greenhouse tomato. In all experiments, fruit number, width and length, yield, vitamin C, lycopene and sugar/acid ratio of tomato markedly increased in response to the aeration treatments. Vitamin C, lycopene, and sugar/acid ratio increased by 41%, 2%, and 43%, respectively, in the 1.5 times standard aeration volume compared with the no-aeration treatment. An interaction between aeration level and depth of irrigation line was also observed with yield, fruit number, fruit length, vitamin C and sugar/acid ratio of greenhouse tomato increasing at each aeration level when irrigation lines were placed at 40 cm depth. However, when the irrigation lines were 15 cm deep, the trend of total fruit yields, fruit width, fruit length and sugar/acid ratio first increased and then decreased with increasing aeration level. Total soluble solids and titrable acid decreased with increasing aeration level both at 15 and 40 cm irrigation line placement. When all of the quality factors, yields and economic benefit are considered together, the combination of 40 cm line depth and “standard” aeration level was the optimum combination.