Energy minimisation in a protected cropping facility using multi-temperature acquisition points and control of ventilation settings

Energy management in protected cropping is critical due to the high cost of energy use in high-tech greenhouse facilities. The main purpose of this research was to investigate the optimal strategy to reduce cooling energy consumption, by regulating the settings (opening/closing) of either vents or curtains during the day, at the protected cropping facility at Western Sydney University. We measured daily changes in air temperature and energy consumption under four treatments (open/closed combinations of vents and shade screens) and developed an optimal cooling strategy for energy management using multi-temperature acquisition points at different heights within a greenhouse compartment. The optimal treatment (vents open/curtains closed) reduced energy load at the rooftop, thereby maintaining a desirable plant canopy temperature profile, and reducing cooling energy. Daily energy consumption was lowest for vents open/curtains closed (70.5 kWh) and highest for vents closed/curtains open (121 kWh). It was also found that delaying the operation of opening and closing of vents and curtains until the plant canopy temperature reached 25 ◦C reduced cooling energy consumption and decreased heating energy consumption in the morning (e.g., 08:00 to 10:00). The estimated savings of 1.83 kWh per 1 ◦C cooling between the optimal (vents open/curtains closed) and least optimal (vents closed/curtains open) conditions had the potential for significant energy savings at 494 kWh per ◦C over a crop cycle of nine months in warm weather conditions. However, selection of the optimal cooling strategy utilising control of vents and curtains must also account for the impact from other greenhouse environmental factors, including light, humidity, and CO2 concentration, which may be crop specific

A novel cover material improves cooling energy and fertigation efficiency for glasshouse eggplant production

Glasshouses hold the potential to improve global food security, but high energy costs are an ongoing challenge in bringing them to the forefront of agriculture in warm climates. Here, the energy-saving potential of a ‘Smart Glass’ (SG), diffuse glass fitted with ULR-80 film which permits transmission of 85% of photosynthetically-active light and blocks heat-generating radiation, was characterised for a warm-climate glasshouse. Two consecutive 6-month trials of eggplant crops were grown in a high-tech glasshouse to compare SG to standard diffuse glass (control) in both cool and warm climate conditions. The SG reduced cooling energy use by 4.4% and fertigation demand by 29% in cooler months, and reduced cooling energy use by 4.4% and fertigation demand by 18% in warmer months. The SG did not significantly affect ventilation or heating energy use, but substantially reduced fruit yield. SG may be beneficial for reducing nutrient/water use alongside minor energy savings in commercial glasshouses. However, re-engineering the spectral characteristics of SG could improve eggplant fruit yield while maintaining reductions in energy, nutrient, and water use in the glasshouse

Contrasting effects of two pesticides on motile arthropods in a citrus orchard canopy

Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-target motile foliage-dwelling arthropod communities that could be sampled by a portable suction system in a citrus orchard in the coastal region of New South Wales, Australia. Sprays of nC24 horticultural mineral oil (HMO) and an organophosphorous insecticide (methidathion) were applied at the level of whole blocks in the manner pertinent to successful control of (sessile) scale insects. The MDS model produced ordination figures for several sampling times before and after spray applications that showed that any effect of HMO was undetectable but methidathion was disruptive to the sampled motile foliage arthropod community for at least 18 weeks. This was confirmed with ANOVA of arthropod abundance. Thus if sprays were required several times per year it would be desirable to use HMOs to preserve biodiversity

Conservation of natural enemy fauna in citrus canopies by horticultural mineral oil : comparison with effects of carbaryl and methidathion treatments for control of armored scales

The disruptive effects of an nC24 horticultural mineral oil (HMO) and two other insecticides (carbaryl and methidathion) on two armored scale insects and natural enemy fauna were evaluated in two citrus orchards. In the first orchard, all three spray treatments and non-sprayed controls were distributed separately among individual trees in one block, whereas in the second orchard the control, HMO and methidathion treatments were applied at the level of whole blocks. The results in both orchards were similar. All three of the spray treatments had a lethal effect on the red scale insects and the effects of HMO and methidathion tested at the second site lasted for at least 19 weeks and for purple scale, at least 50 weeks. HMO did not have a significant effect on the abundance and species diversity of parasitoids and (for the most part) did not affect coccinellids and predatory mites. Both carbaryl and methidathion caused significant ongoing disruption to the above groups. No treatment resulted in the resurgence of the scale insects or the outbreak of phytophagous mites, even where whole blocks were sprayed

Growing lettuce and cucumber in a hydroponic system using food waste derived organic liquid fertiliser

Increased food waste (FW) production and resulting greenhouse gas production due to current disposal methods have promoted the need for recycling. This study describes an innovative method of recovering the nutrients from FW for use in hydroponic systems. The study evaluates the feasibility of using food waste-derived organic liquid fertiliser (FoodLift) for hydroponically producing lettuce and cucumber. The yield obtained using FoodLift was compared with that obtained using commercial liquid fertiliser (CLF). Growing cycles of lettuce and cucumber were completed in 42 and 119 days, respectively. In the case of lettuce, all parameters (such as fresh matter (FM) and dry matter (DM) yields) were similar for the plants grown using FoodLift and CLF. The average FM yields in the hydroponic system grown using FoodLift and CLF were 156 and 161 g/plant, respectively. Statistically insignificant differences (p > 0.05) between the two fertilisers indicate that FoodLift is as effective as CLF in growing hydroponic lettuce. However, the FM and DM yields of cucumber plants grown using FoodLift were significantly lower than those obtained using CLF. This may be attributed to lower phosphorus concentrations (about 2.5 times less) in the FoodLift feed solution during the cucumber plants flowering stage. This was associated with the significant abortion of flowers observed in the cucumber plants fed with FoodLift. Therefore, it is feasible to increase the yield through phosphorus addition into FoodLift to bring its phosphorus concentration at par with CLF. This study demonstrates the potential for applying circular economy principles for managing food waste