Effects of organic and inorganic fertilization on growth and yield of Physalis peruviana L. crop under Mediterranean conditions

Physalis peruviana L. is an Andean Solanaceae fruit crop with great nutraceutical qualities, potential health benefits and adaptability to Mediterranean climates. In the current study, a first approach on the effect of organic and inorganic fertilization on P. peruviana crop under Mediterranean semi-arid conditions was performed. A field experiment was laid out according to a completely randomized design, with three replicates and three fertilization treatments [untreated (control), organic fertilization (biocyclic humus soil) and inorganic fertilization (inorganic fertilizer 40-0-0+14.5 SO3)]. Phenological growth stages and their corresponded growing degree days were evaluated. In addition, some growth parameters, fruit yield and yield components were evaluated. The results indicated that the duration of phenological growth stages was in accordance with durations mentioned in tropical climate. The highest branches number per plant (24.4), leaf area per plant (1997.3 cm), fruit number per plant (41.52), fruit yield (7.51 t ha) and average fruit weight (5.32 g) were found in inorganic fertilization plots, whereas the highest plant height (44.15 g) and fruit diameter (12.52 mm) were recorded under organic fertilization; however, the differences between the organic and inorganic fertilization were not statistically significant. In terms of dry weight per plant, there were significant differences among the fertilization treatment with the values obtained under inorganic fertilization (81.24 g). To sum up, P. peruviana showed satisfying adaptability under Mediterranean climate conditions and has great potential in becoming an alternative cultivation for small and medium producers of Mediterranean countries. In addition, the results indicated that organic fertilization (with biocyclic humus soil) should be considered as an alternative to inorganic fertilizers for P. peruviana production.


Introduction
Physalis peruviana L. (Solanaceae) is an herbaceous, semi-shrub, upright, and annual in temperate zones (perennial in tropical zones) plant, and can grow to 1 m. It is indigenous to South America Andes, mainly Peru, Colombia, and Ecuador (Muniz et al., 2014). The cultivation of P. peruviana in South America can be traced back to the Inca Empire. This species has been grown in England since the end of the 18 th century, and in South Africa from the early 19 th century in the Cape Peninsula. P. peruviana, which was widely introduced in the 20 th century, is now cultivated or grows wild in temperate and tropical regions worldwide. In general, P. peruviana can grow in a wide variety of soil and climatic conditions and is considered a fairly tolerant plant due to its adaptation to Mediterranean climates and to several soil types (Fischer et al., 2011). P. peruviana produces a small orange, berry-shaped, and sweet fruit that is high in provitamin A and ascorbic acid, as well as alkaloids, flavonoids, carotenoids, fructose, sucrose esters, polyphenols and bioactive compounds (Muniz et al., 2014;Bertoncelli et al., 2017). P. peruviana fruit is often consumed fresh giving an acid-sweet balance to fruit and vegetable salads (Puente et al., 2011). At present, the fruit of P. peruviana is processed into a variety of products, including jams, juices and raisins (Ramadan and Moersel, 2007). It is used as an ornament in meals, salads, desserts, and cakes in European markets (Puente et al., 2011;Bertoncelli et al., 2017). P. peruviana has many therapeutic characteristics, including antispasmodic, diuretic, antiseptic, antidiabetic sedative, analgesic, aiding in optic nerve fortification, throat trouble relief, and elimination of intestinal parasites and amoeba (Cárdenas-Barboza et al., 2021). Moreover, the fruit of P. peruviana is used empirically in Peruvian traditional medicine to cure cancer and other ailments such as hepatitis, asthma, malaria, and dermatitis; nevertheless, their properties have not been scientifically verified (Mayorga-Cubillos et al., 2019). In addition, P. peruviana calyces (capsules) are widely utilized in traditional medicine for their anticancer, antibacterial, antipyretic, diuretic, and anti-inflammatory immunomodulatory effects (Puente et al., 2011;Cárdenas-Barboza et al., 2021). Although P. peruviana is gaining popularity among producers, there is a lack of work and research results to guide them in terms of cultural practices, productivity, and economic aspects of production. Currently, fertilizer management in P. peruviana crop is based on tomato crop recommendations (Muniz et al., 2014;Ariati et al., 2017;Bertoncelli et al., 2017). Only a few researchers have reported the use of organic compost in the cultivation of P. peruviana de Souza et al., 2021).
Crop nutrition is the most important component to consider in an agricultural production system since it directly affects crop performance, requiring soils with high nitrogen, potassium, calcium, and boron availability (Muniz et al., 2014;Xin et al., 2016;Bertoncelli et al., 2017). However, in typical cropping systems, excessive use of fertilizers and chemical fertilizers, as well as poor soil management, result in water contamination (Xin et al., 2016;Cihangir and Oktem, 2019). In order to reduce these environmental repercussions, the search for sustainable alternatives such as organic agriculture arises, as this approach is beneficial to crop productivity as well as life quality (Xin et al., 2016;de Souza et al., 2021).
Literature survey revealed that there was no information available concerning the performance of P. peruviana growth cultivated under Mediterranean semi-arid conditions and organic cropping system. As a result, the purpose of the present study aimed to investigate the effect of organic and inorganic fertilization on plant growth and yield of. P. peruviana in Mediterranean field conditions.

Materials and Methods
A P. peruviana crop was established in the organic experimental field of the Agricultural University of Athens (Latitude: 37°59′ N, Longitude: 23°42′ E, Altitude: 30 m above sea level) from April to August 2019. The soil was a clay loam (29.2% clay, 35.1% silt and 35.7% sand) with pH (1:1 H2O) 7.38, nitrate-nitrogen (NO3-N) 12.6 mg kg -1 soil, available phosphorus (P) 13.6 mg kg -1 soil, available potassium (K) 203 mg kg -1 soil, 15.83% CaCO3 and 1.86% organic matter. The site was managed according to organic agricultural guidelines (EC 834/2007). Weather data (mean air temperature and precipitation) pertaining to the experimental period were recorded by the automatic weather station (Davis Vantage Pro2 Weather Station; Davis Instruments Corporation, California, USA) of the Agricultural University of Athens and are presented in Figure 1. Initially, five polystyrene floating trays with 198 cells per tray (17 cm 3 per cell) were filled with organic peat. On each individual cell, one seed of P. peruviana was sown. The polystyrene trays were then placed in a 250 L basin filled with water. In the basin, 2.5 L of organic water-soluble fertilizer (Fishfert, 2-4-0.5 and other trace elements; Humofert Co., Athens, Greece), as well as 25 g of organic enhancer (Trianum-P; Koppert BV, Berkel en Rodenrijs, The Netherlands) for plant protection were added. When the seedlings presented two pairs of true leaves with approximately 15 cm, which takes 25 days after sowing, they were transplanted to the final position in the field. The transplanting of the seedlings was done on 14 th May 2019. The soil was prepared by mould-board ploughing at a depth of 0.25 m and the experiment was arranged in a completely randomized design (CRD) with three replications and three fertilization treatments: control-untreated, inorganic fertilization and organic fertilization with biocyclic humus soil. The plot size was 12.25 m 2 (3.5 m × 3.5 m). In each plot, 88 seedlings were transplanted at a spacing of 40 cm × 30 cm. One day before transplanting of P. peruviana 250 kg ha -1 of the inorganic fertilizer (Nutrimore Winner 40-0-0+14.5 SO3, Gavriel Ltd.) was applied manually. The biocyclic humus soil was also applied by hand into the planting rows with 44 L in each, which is 4 L for each plant. Inorganic fertilizer and biocyclic humus soil were incorporated with the soil by harrowing. In addition, a drip irrigation system was also set up in the experimental field. The total quality of water applied during the cultivation period was 678 mm. Throughout the experimental periods, there was no incidence of pest or disease on P. peruviana crop. Weeds were controlled by hand-hoeing when needed.
The biocyclic humus soil, which was used in this experiment and sourced from Biocycle Vegan Company, is made entirely of plant materials, primarily by-products of olive oil mills. The raw materials consisted of 50% olive leaves, 30% olive pomace, 10% grape pomace, and 10% ripe humus soil. First, an aerobe composting process was carried out in rows 1.5 m high and 2.5 m wide. The raw materials were aerated and hydrated using a compost windrow turner. A ripe compost of substrate quality was obtained after 5 to 6 months of composting. A three-year ripening process was followed to convert the ripe compost into humus soil. The resulting material is beyond the substrate maturity and has a more soil-like structure that is suitable for direct planting. The biocyclic humus soil contained 2.8 g total nitrogen, 0.8 g P2O5 soluble in inorganic acids (total), 0.6 g total potassium, 7.6 units electrical conductivity (1:5) pH and 91.9 cation exchange capacity (C.E.C.) meq Na per 100 g humus soil. It was certified in accordance with the Biocyclic Vegan Standard, which became a global standard in December 2017 and a full member of the IFOAM's Organic Family of Standards (Eisenbach et al., 2019).
Plant height, number of branches per plant, leaf area per plant and dry weight per plant were determined on ten randomly selected plants from each plot at 80 days after transplanting (DAT). Dry weight was determined after drying for 48 h at 64°C. An automatic leaf area meter was used to calculate leaf area (Delta-T Devices Ltd., Burwell, Cambridge, UK). Moreover, fruit yield, fruit number per plant, average fruit weight and fruit diameter (without the capsule) were determined by plants derived from the middle sub-plot area (1 m 2 ) at fruit maturity on 30 th August 2019 (128 DAT).
Finally, heat accumulation in growing degree days (GDDs) from transplanting until fruit maturity, summing the growing degree days in each time period evaluated (Pathak and Stoddard, 2018). Growing Degree Days (GDD) was calculated as: where, GDDi is the accumulated growing degree days, Tmin and Tmax are the minimum and maximum air temperature, respectively. Tbase is P. peruviana base temperature (Tbase = 6.29°C) (Salazar et al., 2008).
The experimental data were checked for normality and subjected to statistical analysis using the SigmaPlot 12 statistical software (Systat Software Inc., San Jose, CA, USA) according to the completely randomized design (CRD). The differences between means were separated using Least Significance Difference (LSD) test. All comparisons were made at the 5% level of significance.

Results and Discussion
Thermal Time and Phenological Growth Stages P. peruviana seedlings, consisted of 4-5 leaves each, were transplanted on 14 th May 2019 (12.81 GDD; Table 1). After 556.23 GDD, plants entered fast development and leaf growth during the first half of June (vegetative stage). This stage lasted around one month from the first half of June to the first half of July. Flowering began around the first half of July after obtaining 1217.63 GDD (Figure 2a). Fruit formation was initiated during the first half of August and this stage received 1922.99 GDD. At this time period flowering and fruit formation were occurring simultaneously, proving the fact that P. peruviana has a tendency of indeterminate growth. Moreover, when the measurement of specific plant characteristics took place, fruit maturity was at a middle stage (fruit: yellow to orange) with a total obtainment of 2267.14 GDD.  (Table 1). Moreover, 128 days after transplanting, fruit maturity was at a middle stage (fruit: yellow to orange) thus assuming that harvesting of ripe fruits could potentially start around the time period mentioned from NRC (1989). Miranda (2005) reported the duration of phenological stages of P. peruviana as a monoculture in Colombia. The flowering is initiated after 2 months of transplanting seedling of P. peruviana in final field position. In continuation with this stage, fruit formation begins 1 month after flowering and 1.5 months after fruits have formed occurs fruit maturity. Harvesting of fruits arises around 2.5 months after fruit formation. The duration of the phenological growth stages that were observed in this study are in accordance with Miranda (2005). Flowering stage of P. peruviana occurred around 2 months after the day of transplanting (Table 1). In addition, fruit formation took place approximately 1 month after flowering and a middle stage of fruit maturing was spotted on the day of measurement.  Table 2). The highest mean plant height (44.15 cm) was observed in the organic treatment followed by the inorganic treatment (40.54 cm); however, the differences among these treatments were not statistically significant. Similarly, Ariati et al. (2016) found a slightly better response of organic fertilizer (poultry litter) on plant height of P. peruviana with issuing an average height of 180.9 cm in comparison with mineral fertilizer (167.7 cm). Although the results for plant height of the present study are according with the results of Ariati et al. (2016), the numerical differences observed between the plant heights may due to the fact that P. peruviana crop was cultivated in the region of Brazil in a tropical climate that favours the overall growth of this species, in contrast to the Mediterranean climate where P. peruviana only shows adaptability. De Souza et al. (2021) obtained different results at 45 days after transplanting (DAT) in P. peruviana crop with the highest plant height recorded with chemical fertilizer (28.66 cm) and the second highest on organic fertilizer that was contained in organic compost produced from cattle, goat manure, and tree pruning waste (27.38 cm). The results between inorganic and organic fertilization were not significantly different. This results difference could be explained by the fact that the organic fertilizer mentioned above was dissimilar with the one that was used in the present study. The number of branches per plant is presented in Table 2. The effect of different fertilization regimes was found to be statistically significant (F= 7.327, p= 0.0097). Specifically, the highest number of branches (24.4) was achieved in plots fertilized with inorganic fertilizer followed by organic fertilization (23.9). Similar results were also recorded in tomato crops by several researchers (Mehla et al., 2000;Bilalis et al., 2018;Roussis et al., 2019). Bertoncelli et al. (2017) also reported a significantly increased number of branches in the P.
peruviana crop with the increase of nitrogen doses (0 to 350 kg N ha -1 ), while this trait was not affected by phosphorus and potassium. The applied nutrients play a pivotal role in the assimilation of amino acids and nucleic acids, as well as the regulation of many metabolic processes, which increases photosynthetic efficiency . Increased soil fertility leads to increased availability of applied nutrients, particularly nitrogen, which promotes vigorous plant growth while limiting profuse branching and leaf production.
The analysis of variance revealed that leaf area per plant was actually affected by the different fertilization treatments (F= 12.223, p= 0.0232). In particular, the highest value (1997.3 cm 2 ) recorded in inorganic treatment, while the lowest value (1317.6 cm 2 ) obtained from the untreated (control) plot (Table 2). This is in accordance with previous studies in P. peruviana, confirming the positive response of this species to inorganic nitrogen fertilization (El-Tohamy et al., 2009;Bertoncelli et al., 2017). In general, higher nitrogen availability to plant result in greater leaf area, which leads to greater light absorption and further carbon fixation (Field and Mooney, 1986;Kakabouki et al., 2018).
Regarding the dry weight per plant, there were statistically significant differences among fertilization regimes (F= 9.463, p= 0.0074) and the highest value (81.24 g) was found in inorganic fertilization treatment (Table 2). In an experiment with P. peruviana, inorganic nitrogen fertilization also positively influenced the total plant mass, reaching 472.50 g per plant with the dose of 200 kg N ha -1 and 274.25 g per plant in 50 kg N ha -1 dose (El-Tohamy et al., 2009). Nitrogen fertilization increased vegetative growth and biomass accumulation since it increases photosynthate source capacity (Bilalis et al., 2018).
According to the analysis of variance, the number of fruits per plant was significantly affected (F= 6.757, p= 0.0008) by different fertilization treatments (Table 3). The highest fruit number (37.53) obtained in the inorganic fertilization treatment followed by organic fertilization with biocyclic humus soil (37.53), while the lowest value (12.47) was observed in untreated (control) plants. Generally, the apparent deficiency of an adequate supply of plant-available nitrogen from organic fertilizers, caused by a slow rate of mineralization, leads crop yield and its components to be lower in fields treated with organic fertilizers than in those treated with inorganic fertilizers (Blatt, 1991). The fruit yield differed among the fertilization regimes (F= 42.622, p= 0.0387) with the highest value (7.51 t ha -1 ) observed in the inorganic treatment followed by organic fertilization (6.89 t ha -1 ). The lowest value (3.69 t ha -1 ) was recorded in the untreated plots. The higher yield in inorganic fertilization is attributed to increased availability of nitrogen with elevated soil fertility levels as applied nutrients help in the vigorous growth of plants with an increased number of branches, flowers, and fruits. In an experiment developed by Bertoncelli et al. (2017) with P. peruviana plants, the authors obtained an increase in fruit yield per plant, as well as in the fruit mass, as a function of increase in nitrogen dose, a similar trend with the nitrogen availability observed in the current study. According to El-Tohamy et al. (2009), the increase in the number of fruits per plant, in P. peruviana, with an increase of available nitrogen is probably due to the fact that nitrogen is the element absorbed in greater quantity and with a fundamental importance for the growth and development of P. peruviana plants.
The results of the present study indicated that the effect of organic and inorganic fertilization on average fruit weight was statistically significant (F= 24.214, p= 0.0217). The highest average fruit weight (5.32 g) was observed in the inorganic treatment followed by the organic treatment (4.93 g). Bertoncelli et al. (2017) had confirmed that the average weight of P. peruviana fruits was increased with the elevation of the available nitrogen to the plant. In tomato crop, Bilalis et al. (2018) observed that the mean fruit weight was not influenced by fertilization; however, significant differences could be due to the variation in cultivars, soil type, temperature and precipitation during the cultivation period.
Fruit diameter (without the capsule) of P. peruviana was significantly affected by fertilization (F= 34.121, p= 0.0026) and the highest value (12.52 mm) observed in organic fertilization with biocyclic humus soil followed by inorganic fertilization (12.03 mm). These results are in line with those observed by Muniz et al. (2011), that when evaluating the effect of inorganic fertilizer (NPK 5-20-10) and organic (50% bovine manure compost and 50% swine) in P. peruviana obtained larger diameter fruit in plants fertilized with the organic fertilizer (21.14 mm with capsule) and the inorganic resulted in fruits with a mean diameter of 19.98 mm. On the contrary, Ariati et al. (2017), as they recorded an average fruit diameter (without the capsule) for P. peruviana of 18.75 mm with inorganic fertilizer, 18.30 mm with organic and 17.81 mm with control. In tomato plant, it was observed that this attribute is highly dependent on genetic factors linked to cultivars (Bilalis et al., 2018).

Conclusions
The results of the current research study on P. peruviana confirmed that this species presents substantial adaptability to Mediterranean climate condition, as the durations of most phenological growth stages were similar with those mentioned in areas with tropical climate where this plant is indigenous. In addition, the current results also confirmed that growth, yield and yield parameters were affected by fertilization. Specifically, the highest branches number per plant, leaf area per plant, fruit number per plant, fruit yield and average fruit weight were found in inorganic fertilization plots, whereas the highest plant height and fruit diameter were recorded under organic fertilization; however, the differences between the organic and inorganic fertilization were not statistically significant. In terms of dry weight per plant, there were significant differences among the fertilization treatment with the values obtained under inorganic fertilization. To sum up, P. peruviana presents considerable adaptability to Mediterranean climates. It has great potential in becoming alternative cultivation for small and medium producers of Mediterranean countries. Moreover, the current study indicated that organic fertilization (with biocyclic humus soil) should be considered as an alternative to inorganic fertilizers for P. peruviana production. Further experimentation on this plant species is required regarding the appropriate cropping techniques in order to ensure its effective organic cultivation in Mediterranean areas. Ethical approval (for researches involving animals or humans) Not applicable.