No abstract

Soil amendments, such as straw mulch, organic fertilizers and superabsorbent polymer (SAP), are extensively applied to improve soil structure and porosity, and we reported the functional consequences of the individual application of these amendments in our previous study. However, whether combined amendments are more effective than their individual applications for improving soil pore structure is unknown. Here, we conducted X-ray computed tomography (CT) scanning on undisturbed soil columns to investigate the efficiency of two-amendment application, including straw mulch and organic manure, SAP and organic manure, or SAP and straw mulch, for improving soil pore properties and pore distribution. The X-ray CT technique allows us to accurately determine the number, morphology, and location of macropores (>1 mm in diameter) and smaller pores (0.13–1.0 mm). Compared to the control treatment, which showed the lowest increase in soil porosity, all the combined treatments led to an increase in the numbers of both macropores and smaller soil pores, causing a significant improvement in soil structure and porosity. Among these treatments, the application of both straw mulch and organic manure was the most effective for improving soil porosity and soil physical structure.

Root temperature has long been considered an essential environmental factor influencing the plant’s physiology. However, little is known about the effect of root temperature on the quality of the food produced by the plant, especially that of horticultural crops. To fill this gap, two independent root cooling experiments (15 °C vs. 20 °C and 10 °C vs. 20 °C) were conducted in autumn 2017 and spring 2018 in hydroponics with Chinese broccoli (Brassica oleracea var. alboglabra Bailey) under greenhouse conditions. The aim was to investigate the effect of root temperature on plant growth (biomass, height, yield) and food quality (soluble sugars, total chlorophyll, starch, minerals, glucosinolates). A negative impact on shoot growth parameters (yield, shoot biomass) was detected by lowering the root temperature to 10 °C. Chinese broccoli showed no response to 15 °C root temperature, except for an increase in root biomass. Low root temperature was in general associated with a higher concentration of soluble sugars and total chlorophyll, but lower mineral levels in stems and leaves. Ten individual glucosinolates were identified in the stems and leaves, including six aliphatic and four indolic glucosinolates. Increased levels of neoglucobrassicin in leaves tracked root cooling more closely in both experiments. Reduction of root temperature by cooling could be a potential method to improve certain quality characters of Chinese broccoli, including sugar and glucosinolate levels, although at the expense of shoot biomass.

Understanding the effects of root temperature on plant growth and key food components of horticultural crops under greenhouse conditions is important. Here, we assess the impact of root cooling on plant growth and fruit quality of two cocktail tomato cultivars (Lycopersicon esculentum cv “Amoroso” and cv “Delioso”) during the winter of 2017-2018 and the summer of 2018. Plants were grown hydroponically on rockwool under different root temperatures (16–27°C and 10°C) from the 2nd inflorescence to harvest inside the greenhouse. A root temperature of 10°C was controlled independently from air temperature (18–23°C in winter and 21–29°C in summer) by circulating cooling water. Reductions of marketable yield per plant (7.9–20.9%) in both cultivars were observed in response to root cooling in winter, but not significantly in summer. In most cases, root cooling had a positive effect on the functional quality (sugars, vitamin C, and carotenoids levels). In the case of “Delioso,” glucose concentration increased by 7.7–10.3%, vitamin C by 20–21%, and lycopene by 16.9–20.5% in both seasons. “Amoroso” exhibited only higher consistent values in glucose with increments between 6.9 and 7.8% in the two seasons. The levels of elements decreased by root cooling, with statistically significant reduction of N, P, S, and Fe by 12.1–15.7% in “Delioso” in winter and P and Zn by 9.1–22.2% in both cultivars in summer. Thus, manipulation of root temperature could be a feasible method to improve the overall fruit quality of cocktail tomato; however, this effect was also dependent on cultivars and other environmental factors.

Long‐term conventional tillage leads to soil compaction and formation of a plough layer, which affects soil physical properties, transport of water, and growth of crop roots toward deeper soil, resulting in soil degradation and a decline in crop productivity. Long‐term sub‐soiling tillage has proven to be an effective measure for remediating the plough layer and improving the structure and physical properties of the soil. In this study, we experimentally investigated the effects of long‐term sub‐soiling tillage in an arid region of Henan Province, China, along a deep soil (0–100 cm) profile over 8 years of sub‐soiling tillage at a depth of 30 cm and compared the results against conventional tillage at a depth of 15 cm. We measured soil pore distributions of macropores (> 1 mm in diameter), mesopores (0.16–1.0 mm), and total pores (> 0.16 mm) measured by X‐ray computed tomography (CT), soil total porosity (ϕ) and > 0.16 mm equivalent porosity measured by conventional methods, soil bulk density (ρs), soil organic carbon content (SOC), the proportion of macroaggregates (> 0.25 mm) (PMA), soil field moisture capacity (fc), available moisture content, and saturated hydraulic conductivity (Ksat). The results indicate that long‐term sub‐soiling tillage increased soil pore numbers at 0–35 cm depth (macropores, mesopores, and total pores), improved pore shape, and significantly increased porosity at 0–20 cm depth (macropores, mesopores, and total pores; p < 0.05) compared to conventional tillage. In addition, ϕ and > 0.16 mm equivalent porosity were increased by 10.4 and 87.1% at depths of 0–60 cm under sub‐soiling tillage, respectively. SOC (0–55 cm depth), fc (0–45 cm depth), available moisture content (0–40 cm depth), Ksat (0–40 cm depth), and PMA (0–50 cm depth) were increased by 16.7, 14.3, 23.8, 471.5, and 98.3%, respectively, and ρs (0–60 cm depth) was reduced by 8.6%. Observed correlations between SOC, soil pore parameters, and soil physical properties suggest that soil pore parameters and soil physical properties can be improved by increasing SOC. These correlations are stronger under sub‐soiling than that under conventional tillage. Therefore, sub‐soiling is an effective technique for improving soil pore characteristics and physical properties while preventing soil degradation.