Quality of Different Papaya Cultivars Grown in the Greenhouse throughout the Year in Subtropical Regions

Harvest time is one of the factors affecting postharvest fruit quality. Under the subtropical condition, greenhouse cultivation allows a year-round harvest. However, the crop should meet the quality and the marketing criteria for overall customer satisfaction. This study aims to determine the impact of the harvest season on the quality characteristics of papaya fruit. For this purpose, two different cultivars (Sel-42 and Tainung) were grown in the greenhouse and harvested in the winter, the summer, the spring, and the autumn of two years. Sampling was carried out at the same visual maturity stage at each season. The two cultivars had soft fruit flesh almost throughout the year, although the fruit harvested in the winter had a better visual appeal in terms of color. Both fruit cultivars harvested in the autumn had higher soluble solids and lower acidity. The highest concentrations of total phenolic content and L-ascorbic acid were observed in the spring and summer season harvested fruits although there was no significant difference between those (P > 0.05). It was concluded that the growth in the greenhouse minimizes the harvest season effects on papaya fruit quality. Thus, greenhouse cultivation is recommended for a higher quality product, especially in a subtropical climate.

Changes in Sugar Accumulation and Related Enzyme Activities of Red Bayberry (Myrica rubra) in Greenhouse Cultivation

The harvest period of bayberry fruit cultivated in the open field is short and often suffers from continuous cloudy and rainy days, leading to a decrease in yield and a decline in fruit quality. However, cultivating bayberries in greenhouses could avoid the harm due to rain, improve fruit quality and prolong the supply period, thus significantly increasing economic returns. Bayberry fruit quality, assessed by single fruit weight, vertical and horizontal diameters, soluble solids content and sugar-acid ratios, was significantly superior in fruit produced under greenhouse conditions than in fruit produced in the open field. Analysis of the soluble sugar components and the related enzyme activities indicated that the sucrose accumulation and metabolism of bayberry fruit were significantly improved by greenhouse cultivation, possibly owing to differences in sucrose-phosphate synthase and acid invertase activities.

Rhizosphere Microbiome Regulates the Growth of Mustard under Organic Greenhouse Cultivation

Organic cultivation can improve soil fertility and biodiversity through the preservation of soil organic matter. Meanwhile, greenhouse cultivation can provide a controlled environment and therefore enables the management of every aspect of plant growth. In recent years, the combination of organic and greenhouse cultivation has slowly become a popular option in tropical regions to prevent the unpredictable impact of weather. Although it is known that organic cultivation significantly increases the density and species of microorganisms, the impact of soil microbiome on short-term vegetable growth under organic greenhouse cultivation is still not elucidated. In this study, we examined soil physiochemical properties as well as the rhizosphere microbiome from healthy and diseased mustard plants under organic greenhouse cultivation. Through next generation sequencing (NGS) analysis, our results revealed that the rhizosphere microbiome structure of healthy mustard plants was significantly different from those of the diseased mustard plants under organic greenhouse cultivation. Our findings suggest that soil microbiome composition can influence the growth of the vegetable significantly. As such, we have shown the impact of soil microbiome on vegetable growth under organic greenhouse cultivation and provide a possible strategy for sustainable agriculture.

Seasonal Nitrous Oxide Emissions From Hydroponic Tomato and Cucumber Cultivation in a Commercial Greenhouse Company

Nitrous oxide (N2O) is considered as the most critical greenhouse gas (GHG) emitted by agricultural and horticultural food production. Hydroponic vegetable cultivation in greenhouse systems has a high potential for N2O emissions due to the intense application of nitrogen-containing fertilizers. Previous studies on model hydroponic systems indicate that N2O emissions per unit area can be several times higher than typically found during field cultivation. However, reliable data from production-scale hydroponic systems is missing. Here we report our findings from monitoring the N2O emissions in a commercial production greenhouse, located in the east of Germany, over a period of 1 year. We used the static chamber method to estimate N2O fluxes in the root zones of hydroponic tomato and cucumber cultures on rock wool growing bags with drip fertigation. Regular sampling intervals (weekly-biweekly) were used to calculate whole season cumulative N2O emissions and N2O emission factors (EFs) based on the amount of nitrogen fertilizer applied. Our results indicate that the seasonal N2O emissions from hydroponic greenhouse cultivation are considerably smaller than expected from previous studies. In total, we estimated average cumulative N2O emissions of 2.3 and 1.5 kg N2O–N ha−1 yr−1 for tomato and cucumber cultures, respectively. Average EFs were 0.31% for tomato cultivation with drain re-use (closed hydroponic system), and 0.13% for cucumber cultivation without drain re-use (open hydroponic system). These values lie below the general EF for N2O from agricultural soils, noted with 1% by the intergovernmental panel on climate change (IPCC). In conclusion, considering the high yield of greenhouse cultivation, hydroponic systems provide a way of producing vegetables climate-friendly, in terms of direct GHG emissions. Further attention should be given to reducing energy inputs, e.g., by using regenerative sources or thermal discharge from industrial processes, and to increasing circularity, e.g., by using recycling fertilizers derived from waste streams. Especially in urban and peri-urban areas, the use of hydroponics is promising to increase local and sustainable food production.