The effect of drought stress on yield and some morphological and agronomic traits of cactus (Opuntia ficus-indica L.) in Shahmaran region of Kerman

IntroductionLack of fodder for feeding livestock is one of the main problems of dry areas, especially in the southern regions of Iran. In this situation, the climate changes and the decrease of rainfall in the southeast of the country in recent years, have doubled the important of compatible plants with the potential to produce fodder in water shortage conditions. Fodder cactus is a drought-resistant plant that adapts to dry and low-water conditions as a source for fodder production in dry areas. This research was conducted to explore the effect of drought stress on yield, water productivity, and some agronomic characteristics of cactus as a new crop in the climatic conditions of Shahmaran region of Kerman, Iran. Materials and methodsThe experiment was carried out in the form of randomized complete block design with four replications. Three treatments of normal irrigation, moderate and severe drought stress were considered based on 160, 210 and 260 mm cumulative pan evaporation. The cladodes (Opuntia ficus-indica) used for planting, originating from Tunisia. In each plot, 32 cladodes were planted at a distance of 2 meters between rows and 1.5 meter between cladodes on a row. At the time of irrigation of each treatment, volumetric soil moisture was measured at the active depth of root development using a calibrated Time-Domain Reflectometry device (Trime-FM, IMKO, Ettlingen, Germany). To calculate the fodder yield of cactus, the cladodes produced on plants in each plot were harvested and weighed. For measuring the length, width, and thickness of the cladode in each plot, 10 cladodes were randomly selected, and the average of each trait was finally determined. Results and discussionThe number of pads produced under the influence of drought stress was significant. The highest number of pads per plant was observed in the normal irrigation treatment (27.7 pads per plant) and the lowest in the severe drought stress treatment (15 pads per plant). The maximum thickness of the pad under normal irrigation condition was 2.4 cm and the minimum thickness was observed under severe drought stress condition. The main reason in reducing the thickness of the pad in water stress condition was the decreasing of the pad moisture content.The effect of drought stress on the length and width of the pad, was significant. Minimum length and width of the pad was observed with 29.5 and 18 cm in severe drought stress treatment and the maximum with 37.7 and 24.7 cm in normal irrigation treatment.The percentage of pad dry matter at the time of sampling was significantly affected by water stress treatments. The dry matter percentage was the lowest in the normal irrigation treatment with 8% and the highest in the severe water stress treatment with 12.7%.The weight of the each pad and the yield of wet and dry fodder per hectare were significant under the influence of different water stress treatments. The wet weight of the pad per plant was the highest in the normal irrigation treatment with 1245 g and the lowest in the severe water stress treatment with 870 g. Normal irrigation treatment produced the highest yield by producing 112 and 8.97 t.ha-1 of fresh and dry fodder, respectively. The lowest wet and dry yield belonged to severe water stress treatment with production of 46.77 and 6.05 t.ha-1.The highest water productivity for wet and dry cactus fodder was 41.02 and 3.29 kg m-3 respectively, which belonged to the normal irrigation regime. There was no significant difference between moderate and severe water stress treatments for dry fodder in terms of water productivity. ConclusionOverall, the research results showed that drought stress has a significant effect on fodder yield, water productivity, cladode thickness, cladode length and width, cladode weight, and crude protein of cactus fodder. Despite the physiology of the cactus and its resistance to water stress, with the increase of drought stress, the wet and dry yield, water productivity, and fodder protein content showed a significant decline. According to the results, reduction of 58.2% in wet fodder yield and of 32.5% in dry fodder yield were seen in severe drought stress treatment compared to normal irrigation. The average water consumption was 2507.6 m3.ha-1. According to the results, in order to benefit from the potential of the cactus to produce fodder, it is necessary to avoid long-term and severe drought stress. The vegetative growth period of cactus was mainly found in spring and early summer. With the cooling of the air from late fall to early March, the plant is going to be entered the stage of growth stagnation. Due to the evergreen nature of the plant, the fodder of this plant can be used for feeding livestock in the fall and winter seasons, when there is a lack of fresh fodder. This research determined that there is a possibility of growing and developing cactus plant as a new plant in Shahmaran region with a subtropical climate. Also, through cultivation of this plant with low water consumption, part of the fodder shortage for livestock in Kerman province can be resolved.