Mitigating the Adverse Effects of Semi-Arid Climate on Capsicum Cultivation by Using the Retractable Roof Production System

Abstract

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.

Extending the Capsicum Growing Season under Semi-Arid Climate by Using a Suitable Protected Cropping Structure

“…According to the multi-year statistics of the Australian Bureau of Meteorology, the annual means of maximum and minimum temperatures were 27.4 • C and 17.2 • C, respectively, and the average annual rainfall was 221.6 mm. The soil inside the RRPS was red silty loam soil and was prepared before planting, as previously described by Nguyen et al [5]. In brief, the raised beds of 60 cm wide and 10 cm high, spaced 1.2 m, were created by the tractor.…”

“…The gypsum basal fertilisation was applied before laying the plastic mulch, and the weekly fertigation began one week after the planting. The pruning and training of capsicum plants to the horizontal trellis were carried out fortnightly, commencing three weeks after planting and following the method described previously [5]. Insect pests and diseases were monitored every second day and controlled by using appropriate methods such as biologicals and chemicals.…”

“…Capsicum is the second most important vegetable crop after tomato in the district, with approximately 3,700 tonnes produced annually and having a total farm gate value of AUD 13.5 million [4]. High temperatures and excessive sunlight, low air humidity, and high wind speed in spring and summer are the main limitations to the attainment of stable, high yield, and high quality capsicums in Carnarvon [5]. The shade net house is a popular protected cropping structure currently used in this area to cope with the adverse weather conditions.…”

“…Among the protective structures suitable for Carnarvon weather conditions is the RRPS, which consists of a retractable roof, a retractable insect net below the roof, retractable curtains at all four sides, and a fogging system. The fine-tuned operation of these elements provides a modifiable growing environment that can protect crops from unpredictable weather extremes [5]. Our previous studies demonstrated that capsicum crops grown in the RRPS outperformed those in the open field (OF) for fruit yield and quality owing to the ability to modify the internal growing environment [5].…”

“…The fine-tuned operation of these elements provides a modifiable growing environment that can protect crops from unpredictable weather extremes [5]. Our previous studies demonstrated that capsicum crops grown in the RRPS outperformed those in the open field (OF) for fruit yield and quality owing to the ability to modify the internal growing environment [5]. However, the optimum planting dates under the RRPS remain to be identified for crop yield per unit area improvement, as well as the extension of the supply season to target the high-priced market windows, increasing the return on investment.…”