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. S oil microorganisms and soil enzymes are important components of agricultural ecosystems. Bacteria, fungi, and actinomycetes play important roles, including decomposing organic matter, degrading cellulose, and forming antibiotic substances. Nitrogen-fixing bacteria provide nitrogen sources for plants, whereas nitrobacteria prevent the accumulation of nitrite in the soil (Clarholm, 1985). Fungi are involved in the soil carbon cycle by decomposing cellulose, lignin, and pectin to release nutrients, and the development of the mycelium improves the physical structure of the soil (Tedersoo et al., 2014 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.

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Background 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. Results 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). Conclusions 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.

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Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27–33, 34–57, 58–85, 86–99, and 27–99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34–57 DAS) and enlargement (58–85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.

To determine the soil mechanism in root-zone caused by water saving and the production response to alternate drip irrigation (ADI), the present study investigated the effects of deficit ADI on tomato growth using the conventional surface drip irrigation (CDI) as a control. The interactions among the experimental treatments on root index, photosynthetic efficiency, biomass accumulation, yield, fruit quality and irrigation water use efficiency (IWUE) were assessed and the inner mechanism of root-soil effecting on tomato growth, photosynthate distribution, yield and quality was discussed. ADI significantly enhanced root-soil interaction, promoted soil nitrogen and phosphorus absorption by tomato and tomato growth. However, different soil moisture deficits significantly affected tomato photosynthate accumulation and distribution, as well as fruit quality. With irrigation amount of 50% field capacity (F), ADI significantly increased soluble sugar, total soluble solid and lycopene by 38.08%, 19.48% and 30.05%, respectively, compared to those of CDI, but decreased irrigation amounts by 29.86% in comparison with the CDI one. ADI of 70% F could significantly distribute more photosynthate to fruits, thus enhanced tomato yields by 24.6% and improved IWUE by 17.05% compared to that of CDI. In addition, ADI of 70% F improved tomato fruits quality, and in particular organic acid was decreased by 43.75% and sugar-acid ratio was increased by 97% compared to CDI. However, ADI of 60% F distributed more photosynthate to plant, showing no significant difference of yields in comparison with CDI and ADI of 70% F, but a higher IWUE by 19.54% than that of CDI. ADI of 60% F significantly enhanced soluble sugar, total soluble solid, soluble protein, lycopene and sugar-acid ratio in tomato fruits by 2.06, 1.26, 1.61, 1.4 and 3.2 times respectively compared to CDI. Therefore, ADI of 60% or 70% F can be overall recommended for tomato production in a greenhouse, plant growth, fruit yield and quality, and IWUE.

Tomato is an important economic crop that is widely consumed worldwide. Tomato production is mainly limited by the use of nitrogen fertilizer, sunlight, soil and water conditions. Biochar is one of the soil amendments, and it is recognized as a promising practice for improving crop production in agriculture. The effect of biochar on the photosynthetic traits and tomato yield under reduced nitrogen fertilizer application is still not well understood. The objective of this research is to investigate the influence of biochar application on the photosynthesis and yield of tomato under reduced nitrogen fertilizer application from the perspectives of the nutrient uptake of plants (nitrogen and phosphorus), leaf photosynthetic pigment and leaf gas exchange parameters. Two-year greenhouse experiments containing six biochar levels (0, 10, 30, 50, 70, and 90 t ha−1) and two nitrogen fertilizer application rates (190 and 250 kg ha−1) were conducted. Compared with C0, C50 significantly improved the nitrogen uptake (74–80%) and phosphorus uptake (76–95%) by tomato plants and further enhanced the photosynthetic traits of tomato leaves (net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr) and chlorophyll (2–60%), which lead to the highest gains in tomato yield (more than 50%) even when the applied nitrogen fertilizer was significantly reduced (from 250 kg ha−1 to 190 kg ha−1). The photosynthesis rate had a linear correlation with the total nitrogen and phosphorus accumulation and tomato yield. The results will enhance our understandings about the effect of biochar on the photosynthesis and yield of tomato and be of importance for practical agricultural management.

The present study evaluated responses of soil enzyme activity, soil micro-organisms, muskmelon root growth and muskmelon fruit yield and quality to different levels of film covering (full, half and no plastic film covering), drip pipe density (one pipe for one row (T1), three pipes for four rows (T3/4) and one pipe for two rows (T1/2)) and different lower limits of irrigation (60%, 70% and 80% of field capacity) in a greenhouse experiment using an orthogonal experimental design. Half film mulch cover resulted in higher muskmelon root activity (second only to full film covering) during the fruit swelling growth stage and promoted soil micro-organism growth. Compared with full and no film cover conditions, under half film cover mean soil urease activity was 25.16% and 1.46% higher, alkaline phosphatase (ALP) activity was 18.42% and 16.89% higher and catalase activity was 24.20% and 17.24% higher respectively. Compared with T1 and T3/4, under T1/2 mean soil ALP activity was 22.36% and 5.76% higher, catalase activity was 2.45% and 10.57% higher and muskmelon root activity during the fruit swelling period was 1.13- and 3.98-fold higher respectively. Irrigation at both 60% and 80% of field capacity improved muskmelon root length and area, soil micro-organism populations and soil urease, ALP and catalase activity. In addition, half film covering, irrigation at 80% field capacity and T1/2 improved the partial factor productivity for nitrogen, yield and fruit quality of muskmelons in the greenhouse. Therefore, these conditions appear to be the most appropriate agronomic configuration for muskmelon cultivation in greenhouses.