Vermicomposts (VC) improve plant growth and development beyond that normally observed from just soil nutrient transformation and availability. These increases in plant productivity have been attributed to improved soil structure and soil microbial populations that have higher levels of activity and greater production of biological metabolites, such as plant growth regulators. Although there have been many studies on the benefits of VC as a fertilizer source, little research has focused on the effects and/or interactions of soil type and VC application rates on vegetable crop productivity. This paper identifies optimum application rate(s) of VC on tomato growth responses for three different textural classes of soils (loamy sand, silt loam, and silty clay). Soils with high VC rates (0.4 and 0.8 g/g) produced taller plants with more leaf and flower numbers, higher leaf chlorophyll content, greater plant biomass, and more total leaf area compared to soils with low VC rates (0.05, 0.1, and 0.2 g/g). Tomato growth increases were also observed at the low VC soil amendment rates compared to the nontreated control. Tomatoes grown in the sandy soil amended with VC generally had the greatest growth responses (plant height, leaf and flower number, and leaf chlorophyll content) compared to the clay or silt loam soils, with the silt loam soil generally providing the least response. This research indicated that VC is a suitable alternative fertilizer for tomato, with approximately 0.5–0.6 g/g VC added to soil resulting in optimal tomato plant growth. Moreover, this rate provided tomato growth results similar to the standard inorganic fertility program. The sandy soil with VC amendments generally increased tomato plant growth parameters the most compared to the clay and loam soils, with the loam soil generally providing the least.

Crop production in open fields is increasingly limited by weather extremes and water shortages, in addition to pests and soil-borne diseases. In order to increase crop yield, quality, and productivity, controlled environment agriculture (CEA) can play an important role as an alternative and supplemental production system to conventional open field production. CEA is any agricultural technology that enables growers to manipulate the growing environment for improved yield and quality. CEA production systems include high tunnels, greenhouses, and indoor vertical farming, as well as hydroponics and aquaponics. Currently, ‘low-tech’ CEA techniques such as high tunnels (plastic greenhouses with minimum or no cooling and heating) are primarily utilized in developing countries where labor costs are relatively low, and China has by far the largest area covered by high tunnels or ‘Chinese-style’ solar greenhouses. The most control-intensive ‘high-tech’ CEA approach, namely indoor vertical farming, has gained tremendous attention in the past decade by researchers and entrepreneurs around the world, owing to advancements in lighting technology, including use of light emitting diodes (LEDs), and increasing urbanization with new market opportunities. This special issue covers some of the CEA topics such as LED lighting, substrate, and hydroponics.

Blue light and ultra-violet (UV) light have been shown to influence plant growth, morphology, and quality. In this study, we investigated the effects of pre-harvest supplemental lighting using UV-A and blue (UV-A/Blue) light and red and blue (RB) light on growth and nutritional quality of lettuce grown hydroponically in two greenhouse experiments. The RB spectrum was applied pre-harvest for two days or nights, while the UV-A/Blue spectrum was applied pre-harvest for two or four days or nights. All pre-harvest supplemental lighting treatments had a same duration of 12 h with a photon flux density (PFD) of 171 μmol m⁻² s⁻¹. Results of both experiments showed that pre-harvest supplemental lighting using UV A/Blue or RB light can increase the growth and nutritional quality of lettuce grown hydroponically. The enhancement of lettuce growth and nutritional quality by the pre-harvest supplemental lighting was more effective under low daily light integral (DLI) compared to a high DLI and tended to be more effective when applied during the night, regardless of spectrum.

Castanea henryi is a ubiquitous hardwood chestnut species in southern China and is important both ecologically and economically. It is mainly cultivated for nut production, just like other chestnut species. However, the establishment of C. henryi seedlings in a new orchard has proven to be difficult because few seedlings survive transplanting due to the incompatibility of their coarse root architecture with nutrient-depleted red acid soils in southern China. Root architecture can be profoundly modified and nutrient can be stress alleviated due to the association of roots with ectomycorrhizal (ECM) fungi. Boletus edulis is an ECM fungus with edible and medicinal fruiting bodies. However, its impact on plant growth varies with the plant species it is associated with. In order to elucidate the role of B. edulis in C. henryi afforestation, we evaluated growth parameters and soil enzymatic activities, as well as seasonal variations in physiology and structure of ECM root tips. Growth responses and soil enzymatic activities were measured 6 months after inoculation. The physiological characteristics of root tips were also compared at various seasons throughout the year. B. edulis colonization of C. henryi roots was successful at a 60% colonization rate. Height, base diameter, and biomass (especially the underground part) of inoculated seedlings (JG) were higher than those of uninoculated seedlings (CK). JG had higher root total length, root surface area, root volume, root average diameter, and number of root tips than CK. Additionally, JG exhibited higher total nitrogen and phosphorus content. Abnormal mantle and Harting net were observed in winter. No matter the season, ECM tips had higher antioxidant enzyme activities, root activities, soluble protein content, and lower malondialdehyde compared to non-ECM tips (nE) and those without ECM tips (woE), and there were no differences between nE and woE. It is important to understand the growth of the host plant in response to ECM and that the seasonal variation of ECM root tips is important when growing high-quality C. henryi seedlings, due to the crucial role of B. edulis in improving seedling initial survival rate.

Both ectomycorrhizal fungi (ECMF) and inorganic phosphate (Pi) can improve plant growth. However, the relationship between Pi levels and mycorrhizal colonization rate is divergent, and information on the differential and interactive effects of Pi levels and ECMF on nutrient uptake and seedling quality is lacking. We conducted a study on 4-week-old Castanea henryi ‘You Zhen’ seedlings by inoculating with Scleroderma sp. (+ECM) to compare with uninoculated (-ECM), under low Pi level (-Pi) and high Pi level (+Pi). The mycorrhizal colonization rate, seedlings morphological and physiological parameters, nutrient uptake content, and the rhizosphere soil enzymatic activities and chemical properties were investigated. Results indicated that the mycorrhizal colonization rate at low Pi level (84 ± 2%) was higher than that at high Pi level (71 ± 2.52%). No matter the Pi level, inoculating with ECMF significantly improved seedling dry weight, height, diameter, and seedling quality index (SQI). The +ECM+Pi and +ECM-Pi treatments significantly increased SQI by 282.76% and 232.76% in comparison to the -ECM-Pi treatment, respectively. Applied Pi had no significant effect on SQI. ECMF inoculation significantly increased nitrogen (N), phosphorus (P), and potassium (K) uptake in roots, stems, and leaves, while Pi application increased the P uptake in roots only. There was no significant interaction between ECMF and Pi levels on seedling quality and nutrient uptake (except P uptake in leaf). Results indicated that ECMF is a suitable alternative to the use of phosphorus fertilizer in nursery production of C. henryi seedlings in terms of protecting the environment, saving resources, and reducing production costs.

Biostimulants play an active role in sustainable crop production. While biostimulants are thought to have long-term effects on plant growth, little research has been conducted to confirm this hypothesis. In this study, we investigated the long-term residual effects of biostimulants applied exclusively during the onion seedling stage on subsequent plant growth. Three onion cultivars (‘Carta Blanca’, ‘Don Victoro’, and ‘Sofire’) were evaluated with the application of nine microbial biostimulants (LALRISE Mycorrhizae, LALRISE Bacillus velezensis, Mighty Mycorrhizae, MycoApply, Spectrum, Spectrum DS, Spectrum Myco, Tribus Original, and Tribus Continuum), one seaweed extract (Kelpak), and two fertilizer types (conventional and organic fertilizer). Plant morphology and biomass were investigated during the early bulb stage of onion growth. Parameters such as plant height, neck diameter, bulb diameter, and the fresh and dry weights of the shoot, bulb, and root were measured. The results indicated significant cultivar-specific effects of microbial biostimulant and fertilizer type, as well as their interactions, on onion early bulb growth. While seaweed extract exhibited minimal residual impact, specific microbial biostimulants, such as Mighty Mycorrhizae and MycoApply, significantly enhanced bulb growth in the red onion ‘Sofire’. Tribus Continuum was found to increase bulb growth of the yellow onion ‘Don Victoro’. Positive effects of microbial biostimulants on onion growth were also observed with LALRISE Bacillus velezensis, Spectrum Myco, Spectrum, and LALRISE Mycorrizae. Furthermore, microbial biostimulants demonstrated more significant positive effects on onion growth when applied in conjunction with organic fertilizer. In conclusion, microbial biostimulants exhibited long-term positive effects on onion plant growth even when applied solely during the seedling stage prior to transplanting. However, these effects were significantly influenced by onion cultivar and fertilizer type, with the greatest benefits observed when combined with organic fertilizer. We recommend MycoApply and Mighty Mycorrhizae for growers seeking to enhance onion productivity, particularly in organic cultivation, as the two products enhanced bulb and leaf growth in ‘Sofire’ and ‘Don Victoro’.