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Grasslands cover ca. 30% of the global land surface and provide critical ecosystem services. Among them, carbon storage is one of the most important. However, grasslands are increasingly threatened by drought and overgrazing which might negatively affect soil carbon stocks. Despite this threat, there is a dearth of information on how drought and grazing jointly impact soil carbon stocks and CO 2 fluxes in dryland grasslands. With the aid of a large field experiment, we studied the combined effects of a 5-year extreme drought and moderate grazing on soil carbon stocks, CO 2 fluxes and soil chemical properties. Extreme drought was induced by reducing ambient rainfall by 66% using large rainout shelters. We found CO 2 fluxes to strongly respond to the 5-year experimental drought. Extreme drought reduced CO 2 emission rates by 32% compared to ambient conditions. CO 2 fluxes averaged 5.7 mg m −2 min −1 under drought compared to 8.3 mg m −2 min −1 under ambient conditions. CO 2 fluxes were, however, not influenced by grazing. At the end of the growth period, grazed plots under ambient rainfall had released 16.3 tons of CO 2 ha −1 which was 58% higher than observed on grazed plots subjected to severe drought. Soil carbon stocks were higher under drought conditions due to slower decomposition rates. Drought resulted in increased concentrations of primary macronutrients (N, P, and K), micronutrients (Zn and Mn) and pH in the top 30 cm of the soil relative to ambient conditions. The results also showed that grazing reduced the concentration of N and P in the topsoil compared to the ungrazed plots. This study provided insights on the soil carbon storage, CO 2 emission rates and nutrient dynamics in a semi-arid dryland grassland as influenced by both drought and grazing. Our study also revealed that long-term extreme drought may be favorable in terms of preserving the existing soil carbon stocks through reduced CO 2 release. This finding is critical for understanding future soil carbon dynamics in dryland grasslands in the face of climate change.

Preharvest factors such as poor orchard management and field sanitation can lead to pathological infection of the tree fruit being grown as well as insect pest infestation, resulting in poor postharvest fruit quality. Wind and hail damage may cause significant tree fruit abrasions and blemishes. Consequently, these preharvest factors may reduce yield and cause market and economic losses. One of the most successful methods used to manage tree fruit pathogens and insect infestation is the application of agrochemicals, predominantly fungicides and insecticides. However, this method has recently been criticized due to the adverse effects on field workers’ safety, consumers’ health, and the environment. The development and use of preharvest bagging are among the most environmentally friendly technologies intended for safe enhancement of tree fruit quality. The technique protects tree fruit against pathogens, insect pests, physiological disorders, agrochemical residues, fruit abrasions, sunburn, and bird damage, and it further modifies the microenvironment for fruit development with its various beneficial effects on its external and internal quality. Furthermore, because of the global restrictions of agrochemicals and social awareness, this technique provides extensive relief to growers and consumers. However, bagging is labor-intensive and expensive; therefore, its benefits or advantages and disadvantages must be thoroughly investigated if it is to be promoted commercially. This review examines the improvement of tree fruit quality by the application of preharvest bagging during early stages of fruit growth and development. The latest advances in the development and use of tree fruit bagging and its economic impact and cost–benefit ratio are discussed, as are recommendations for the formulation of bagging materials that could be valuable in the future.

Purpose To investigate whether soil clay content, cultivar and seasonal variation have any effect on soil CO2 emission rates and leaf CO2 assimilation rates in a drip-irrigated commercial Citrus sinensis orchard. Methods The study was carried out in the field as a randomised complete block design in a 2 × 2 factorial consisting of two soil types and two citrus cultivars on a drip-irrigated commercial Citrus sinensis orchards with 2-week interval measurements of soil CO2 emission and leaf gas exchanges for a year. Results Soil clay content did not influence plant CO2 assimilation rates and soil CO2 emission rates in irrigated citrus. However, seasonal variation significantly influenced both processes. Soil CO2 emission rates were highest in summer and were more than double the rates observed in winter while leaf CO2 assimilation rates were highest in autumn and four times higher than the winter season rates. Mean seasonal soil CO2 emission rates were strongly influenced by mean minimum seasonal temperatures while leaf CO2 assimilation rates only showed a relatively weak relationship with mean maximum seasonal temperatures. Conclusions Soil clay content did not influence soil CO2 emission and assimilation rates in drip irrigated citrus suggesting a non-significant effect of clay content for soils subjected to similar management practices. Citrus CO2 assimilation rate peaks in the autumn while soil CO2 emission rates peak in summer. A snapshot analysis of CO2 sequestration rates suggests that irrigated citrus orchards are net sinks of CO2 in summer, autumn and winter season.

No abstract

Purpose To investigate whether soil clay content, cultivar and seasonal variation have any effect on soil CO2 emission rates and leaf CO2 assimilation rates in a drip-irrigated commercial Citrus sinensis orchard. Methods The study was carried out in the field as a randomised complete block design in 2x2 factorial consisting of two soil types and two citrus cultivars on a drip-irrigated commercial Citrus sinensis orchards with 2-week interval measurements of soil CO2 emission and leaf gas exchanges over period of a year. Results Soil clay content did not influence plant CO2 assimilation rates and soil CO2 emission rates in irrigated citrus. However, seasonal variation significantly influenced both processes. Soil CO2 emission rates were highest in summer and were more than double the rates observed in winter while leaf CO2 assimilation rates were highest in autumn and four times higher than the winter season rates. Mean seasonal soil CO2 emission rates were strongly influenced by mean minimum seasonal temperatures while leaf CO2 assimilation rates only showed a relatively weak relationship with mean maximum seasonal temperatures. Conclusions Soil clay content did not influence soil CO2 emission and assimilation rates in drip irrigated irrigated citrus. Citrus CO2 assimilation rate peaks in the autumn while soil CO2 emission rates peak in summer.Snapshot analysis of CO2 sequestration rates suggests that irrigated citrus orchards are net sinks of CO2. Empirically measured CO2 flux rates in a commercial drip-irrigated citrus orchard are presented.

Poor exocarp colour development is a common postharvest problem for early harvested "Hass" avocado fruit during ripening, which affects fruit quality and consumer preference. Therefore, measures to improve "Hass" avocado fruit colour developments are of great importance in the industry. This study investigated the effectiveness of postharvest methyl jasmonate treatment to improve early matured "Hass" avocado fruit exocarp colour during ripening. The results showed that T1 (10 µmol•L −1 ) and T2 (100 µmol•L −1 ) MeJA treatment increased visual colour, and decreased objective colour parameters (L*, C* and h˚) during ripening when compared with control fruit. Moreover, MeJA treated "Hass" avocado fruits had lower total chlorophyll content and higher total anthocyanin and cyanidin-3-O-glucoside concentration during ripening. In conclusion, "Hass" avocado fruit post-harvest treated with either T1 (10 µmol•L −1 ) or T2 (100 µmol•L −1 ) MeJA concentration improved exocarp quality attributes such as colour parameters (L*, C* h˚ and visual colour) and pigments (total anthocyanin and cyanidin-3-O-glucoside) during ripening, therefore, can be recommended for avocado fruit.

The production of cherry tomato (Solanum lycopersicum var. cerasiforme) is negatively affected by harsh environmental conditions such as extremely high and low temperatures, wind and hail damage, and pest and disease infestation. These factors delay maturity and cause uneven ripening, fruit abrasion, and blemishes, which consequently result in poor fruit quality and reduced shelf life. Preharvest bagging is an environmentally friendly alternative technique for enhancement of fruit quality and hence alleviates the stated problems. The study evaluated the physico-chemical quality of ‘Tinker’ and ‘Roma VF’ cherry tomato as influenced by preharvest bagging (transparent and blue plastics) during 8 days of shelf life at ambient conditions. Five clusters of fruit per plant per cultivar with a diameter of 1.5 to 2.0 cm were bagged after 16 days of fruit set and harvested at the green maturity stage, 12 days after preharvest bagging for the assessment of postharvest quality. Preharvest bagging effectively accelerated fruit maturity and ripening as indicated by enhanced fruit size, uniform color development, high pH, dry matter (DM) content, soluble solid content (SSC), and low titratable acidity (TA) during shelf life. Bagged fruit had higher loss of firmness and weight mainly due to ripening and showed very slight incidence of diseases during shelf life of 8 days. Unbagged cherry tomato had delayed maturity and ripening; small-sized fruit; uneven color development; low pH, SSC, and DM; and high TA. Although unbagged cherry tomato had lower firmness and weight loss due to delayed ripening, fruit showed moderate to severe incidence of tomato bacterial canker disease (Clavibacter michiganensis subsp. michiganensis) during shelf life. These results indicated that preharvest bagging accelerated fruit maturity and ripening, improved physico-chemical quality, and reduced disease infestation on cherry tomato during shelf life.