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Carnarvon is a key horticultural district in Western Australia which is located approximately 900 km north of Perth and is characterised by a semi-arid climate. In Carnarvon, capsicum (Capsicum annuum L.) is the second most important vegetable crop after tomato, with approximately 3700 tonnes of capsicum fruit produced annually with a farm gate value of AUD 13.5 million. High temperatures, excessive sunlight, low air humidity, and strong wind in spring and summer are major impediments to the achievement of high yield and quality of capsicum in this region. Capsicums are usually planted between March (early autumn) and May (late autumn), and the harvest is usually finished by October (spring) of the same year when grown under shade net houses. However, the internal microenvironment in the shade net houses is sub-optimal for the crop in the early and late growing season due to excessive temperatures and low humidity, resulting in a shorter harvest window and lower production. This study was conducted to examine the possibilities to extend the cropping season for capsicum varieties (i.e., Chevello and Chevi) grown under the retractable roof production system (RRPS) and explore an alternative protected cropping structure that is more affordable and suitable to grow vegetable crops under Carnarvon weather conditions. Overall, the results showed that capsicums planted in February (planting 1) performed better than specimens planted later on in the season: planting 1 performed better and yielded the highest marketable fruit yield (102.6 t ha⁻¹) compared to those planted in early April (planting 2, 72.5 t ha⁻¹) and late May (planting 3, 36.1 t ha⁻¹). The RRPS effectively mitigated the adverse weather conditions and provided a more optimised internal microenvironment for vigorous crop establishment in late summer and an extended harvest in late spring, leading to a higher marketable fruit yield per crop. The total soluble solids were cultivar-specific, with the Brix level of Chevello changing with planting time while those of Chevi remained constant. The study identifies the potential for an alternative protected cropping structure, i.e., the modified multi-span polytunnels. The technical feasibility and affordability of the alternative protected cropping structure is also discussed. Full article

Capsicum (Capsicum annuum L.) belongs to the Solanaceae family and is an economically important vegetable crop. However, the crop is very sensitive to adverse weather conditions such as high temperatures and excessive sunlight, which cause flower and young fruit to drop and sunscald to mature fruits. Using protected cultivation such as shade covers or net houses is a feasible agronomic approach to protect the crop from high light intensity, which increases plant growth, reduces fruit damage, and increases marketable fruit yield and quality. Low-cost protected cropping options such as fixed-roof net houses have proved cost-effective and suitable for fruiting vegetable production in semi-arid climatic regions. However, this structure type is unable to protect the crops from rainfall, is prone to cyclone damage and is inflexible to accommodate various vegetable crops which have different requirements for healthy and productive growth. This study was conducted in Carnarvon, which has semi-arid climatic conditions and is a key horticultural district of Western Australia, to compare the Retractable Roof Production System (RRPS) and open field (OF) conditions in the production of capsicum. The data showed that the RRPS modified the internal light, temperature and humidity in favour of the capsicum crop. The RRPS-grown capsicum had higher plant height and lower canopy temperature on hot days than those in the OF. The mean marketable fruit yield of capsicum varieties grown in the RRPS was significantly higher than those in the OF with fruit yields of 97 t ha⁻¹ and 39.1 t ha⁻¹, respectively, but the fruit quality remained unchanged. Overall, the data suggest that the RRPS altered the internal microenvironment and enhanced capsicum crop growth, physiology and fruit yield by setting climatic parameters to automatically control the opening and closing of the roof, the insect net and side curtains, and activation of the fogging system. The future perspective of the deployment of RRPS for capsicum production under climatic conditions in Carnarvon was also discussed. Full article