1081 AJCS 15(07):1081-1088 (2021) ISSN:1835-2707 doi: 10.21475/ajcs.21.15.07.p3289 Performance of potato cultivars in an organic farming system using organic fertilizers, vermicompost and azolla Amal K. Abou El-Goud 1 , Fahad R. Al-Masoodi 2 , Karam A. Elzopy 3* , Mona M. Yousry 2 1 Department of Botany (Organic Agriculture), Agriculture Faculty, Damietta University, Egypt 2 Plant Production Dept., Faculty of Agriculture (Saba-Basha), Alexandria University, Egypt 3 Department of Soil Science and Agricultural Chemistry, Faculty of Agriculture (Saba-Basha) Alexandria University, Egypt *Corresponding author: karam2016@alexu.edu.eg Abstract The challenges of food shortages and environmental pollution require the development of safe and effective alternatives to chemical fertilizers. Two field experiments were conducted during the summer season of 2019/2020 in two locations on a private farm to evaluate the performance of three potato cultivars (Sponta, Cara, and Elbieda) under different fertilizer treatments. The experiment was laid out in a split-plot design replicated thrice. The main plots had three potato cultivars, while the sub plots were comprised of seven fertilizer treatments. The results showed that the highest vegetative growth characters, viz. plant height, leaf chlorophyll index, and plant dry weight were produced by Sponta, followed by Cara, while the lowest growth attributes were recorded in Elbeida. Compared to the NPK inorganic fertilizer, organic fertilizers significantly improved the vegetative growth characteristics of potato in all treatments. Among the organic treatments, the highest growth parameters were recorded with the application of mixed organic fertilizer, vermicompost, and Azollapinnata (T1). The highest yield, viz. tuber yield, number of tubers per plant, and tuber weight, and yield quality characteristics, viz. total carbohydrates, starch, and TSS, were also recorded in T1. Our results demonstrate that the Sponta cultivar grown with the application of mixed organic fertilizer, vermicompost, and Azollapinnata (T1) produced the highest growth, yield, and quality of potato tubers. Thus, we recommend this treatment combination as a sustainable agricultural practice for potato production in similar areas. Keywords: Potato; Organic Fertilizers; Vermicompost; Azolla. Introduction Globally, potato (SolanumtuberosumL.) tuber productivity was 377 million tonnes in 2016, ranking as the fourth most productive crop after maize, wheat, and rice (FAO, 2017). Potato yields about 175 kg N/ha, 25 kg P/ha, and 250 kg K/ha (Meena et al., 2016; Romero et al., 2017). Approximately 80% of the tuber weight is water, and starches comprise approximately 70% of the total solids. Due to the high carbohydrate content, potato is a good energy source. Potato is also inexpensive, with high nutritional value and high productivity; thus, contributing to reducing global food shortages and providing food security for a growing world population (Zhang et al., 2018). Vermicompost is the final product of the biological decomposition of organic materials by earth worms (Meghvansi et al., 2011). This process, called vermicomposting, is widely used to treat various types of organic residues. Vermicomposting is a sustainable, ecologically friendly, and cost-effective process for organic waste management that produces an environmentally safe organic fertilizer for sustainable agricultural practices (Brown, 1995; Tajbakhsh et al., 2011; Chaulagain et al., 2017; Abou El- Goud, 2020a, b, and c). Moreover, several studies have demonstrated the favorable effects of vermicompost organic fertilizer on the growth and yield of crops such as African marigold (Sharma et al., 2017), pakchoi (Churilova and Midmore, 2019), canola (Rashtbari et al., 2020), tomato (Ravindran et al., 2019), and potato (Pérez-Gómez et al., 2017; Darabi et al., 2018). Azolla, also known as water fern, water velvet, or duckweed, is a genus of aquatic plants normally distributed in pools, streams, and paddy water. Azollais is known for its rapid biomass production and bioremediatory potential (Miranda et al., 2016). Azollaspecies symbiotically coexist with Anabaena azollae alga (Razavipour et al., 2018); the nitrogen- fixing capacity of Anabaena azollae provides fixed nitrogen for Azolla, while Azolla provides fixed carbon and shelter for the algae (Peters, 1978; Pereira et al., 2014). Azolla is a highly efficient biofertilizer due to its rapid growth and high nitrogen-fixation capacity (Wagner, 1997). Azollacan double its biomass every 3–5 daysand fix between 70 and 110 kg N ha −1 (Ventura et al., 1993). Used as abiofertilizer, Azolla increases N, P, K, and micronutrient contents in the soil and enhances microbial activity, porosity, soil water-holding capacity, and water infiltration rate (Mishra et al., 2013; Jumadi et al., 2014). Azolla has been used for centuries as green manure for rice in Vietnam (Lumpkin and Plucknett,