Planting methods and depths for yacon (Smallanthus sonchifolius) crops Métodos y profundidades de siembra para el cultivo de yacón

Crop management is vital to sprouting, cycle and productivity in most plants of commercial interest. However, recommendations and information are scarce for yacon cultivation, especially for possible interferences form planting method and depth in crop development and production. Therefore, the objective was to study the influence of the planting methods and depths on yacon tuberous root development and production under high altitude conditions. This experiment used a randomized complete block design, with four replications, in a subdivided plot scheme. The plots consisted of three planting methods (groove, pit and ridge), and the subplots had four planting depths (5, 10, 15, and 20 cm). Evaluations were carried out starting with the sprouting process of the rhizophores to the yield of tuberous roots. The planting methods pit and ridge had lower seedling mortality rates (27.5 and 20.2% lower than groove) and higher yields of tuberous roots (31.2 and 21.4% higher than groove). The planting depths 5 and 10 cm for the rhizophores were more suitable for yacon cultivation with the three planting methods. Additional keywords: plantation crops; spacing; root vegetables; altitude; ridge tillage; planting depth. 1 Universidade Federal do Espírito Santo, Department of Plant Production, Alegre (Brazil). ORCID Quaresma, M.A.L.: 0000-0003-0622-0955; ORCID Oliveira, F.L.: 0000-0002-1711-6988; ORCID Amaral, J.F.T.: 0000-0003-3027-4830; ORCID Dalvi, L.P.: 0000-0002-2995-8007 2 Universidade Federal de Viçosa, Department of Crop Science, Viçosa (Brazil). ORCID Parajara, M.C.: 0000-0001-6266-883X 3 Instituto Federal do Espirito Santo, campus Santa Teresa, Department of Agronomy, Santa Teresa (Brazil) ORCID Teixeira, A.G.: 0000-0001-8742-521X 4 Corresponding author. arianyteixeira@yahoo.combr Yacon [Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson] confers several benefits, such as constipation relief, increased mineral absorption, strengthened immune system (Genta et al., 2010), decreased development of colon cancer (Santana and Cardoso, 2008) and disease inhibition, such as Diabetes Mellitus (Albuquerque and Rolim, 2012). As a result, interest in cultivation has increased, along with demand for a management method that conders bigger and more stable production. Harvest yield is diverse, ranging from 1 to 41 t ha-1 in Ecuador, 7 to 107 t ha-1 in Peru, 25 to 90 t ha-1 in the Czech Republic and 25 to 35 t ha-1 in the United States. In Brazil, yields from 20 to 100 t ha-1 were observed in the State of Espírito Santo, Brazil. Silva et al. (2018a) observed production variation because of edaphoclimatic conditions, with 97.50 t ha-1 (in the mountainous region) and 60.65 t ha-1 (in the lowland region). These variations in productive yield are attributed to issues related to environmental interference, especially temperature (Silva et al., 2018b) and water availability (Sumiyanto et al., 2012), as well as management, such as the season (Silva et al., 2018a), planting depth, nutrition, and spacing, among others (Seminário et al., 2003). In Brazil and in the world, technical recommendations are needed for yacon cultivation, especially the optimal method and planting depth for different edaphoclimatic conditions because they can influence crop productivity and vary according to the characteristics of the region. The method and planting depth can significantly interfere with the budding process and initial development of the plants (Grotta et al., 2008) and, consequently, crop production. The shape and depth of propagule propagation can expose them to different microenvironment conditions, interfering with the development of future plants (Rós, 2017) and affecting crop productivity (Modolo et al., 2010). Therefore, the objective was to study the influence of planting methods and depths on yacon tuberous root development and production under high altitude conditions. MATERIAL AND METHODS The experiment was carried out in 2016 in “Flor e Mel”, Patrimônio da Penha, a district of Divino de São Lourenço in the State of Espírito Santo, Brazil, with the geographic coordinates 20°35’6.0” South latitude RESUMEN El manejo del cultivo es decisivo en la brotación, el ciclo y productividad de la mayoría de las plantas de interés comercial. Sin embargo, para el cultivo de yacón las recomendaciones e información son escasas, especialmente en lo que respecta a los posibles efectos del método y la profundidad de siembra en el desarrollo y la producción del cultivo. Por lo anterior, el objetivo de este trabajo fue conocer la influencia de los métodos y profundidades de siembra en el desarrollo y producción de raíces tuberosas de yacón en condiciones de gran altitud. El diseño experimental adoptado fue en bloques al azar, con cuatro repeticiones, en un esquema de parcelas divididas, las parcelas principales consistieron de tres métodos de siembra (surcos, hoyos y camas) y las subparcelas fueron las cuatro profundidades de siembra (5, 10, 15 y 20 cm). Las evaluaciones se llevaron a cabo desde el proceso de brotación de los rizóforos hasta el rendimiento de las raíces tuberosas. Los métodos de siembra en hoyos y camas mostraron las tasas de mortalidad de plántulas más bajas (27,5 y 20,2% más bajas que la siembra en surcos) y los rendimientos más altos de raíces tuberosas (31,2 y 21,4% más altas que plantación de surcos). Se demostró que las profundidades de 5 y 10 cm de rizóforos fueron las más adecuadas para el cultivo de yacón para los tres métodos de plantación. Palabras clave adicionales: siembra de cultivos; espaciamiento de plantas; vegetales de raíz; altitud; labranza en camas; profundidad de plantación. Received for publication: 30-05-2019 Accepted for publication: 11-06-2020 INTRODUCTION 250 QUARESMA / OLIVEIRA / AMARAL / PARAJARA / DALVI / TEIXEIRA Rev. Colomb. Cienc. Hortic. and 41°46’18.2’’ West longitude, and an altitude of 1,098 m a.s.l. This municipality is in the mountain region of Espírito Santo, which has a mountain climate (tropical altitude) with two well-defined seasons during the year, one hot and rainy in October to March and the other cold and dry in April to September (Pezzopane et al., 2012). The maximum monthly temperatures ranged from 26 to 28°C, and the minimum temperatures were 12 to 18°C. The total rainfall during the experiment was 760 mm, with uneven distribution and low volume between the months of May to August (INMET, 2016). The area was fallow for nine months, with a high number of ferns (Pteridium arachnoideum (Kaulf.) Maxon), a soil indicator of high acidity. For the initial soil tillage, weeding was done with a costal brush, and, after one week, the soil was plowed three times to about 20 cm using a hoe, incorporating the weed biomass to the soil. The soil of the area was classified as Cambisolo Tb Distrophic, loamy clay texture (Santos et al., 2013), and the chemical and physical analysis showed the following characteristics in the 0 to 20 cm layer: pH 5.21 in water; 3.58 mg dm-3 of P (Mehlich1); 22.00 mg dm-3 of K; 2.59 cmolc dm-3 of Ca; 0.84 cmolc dm-3 of Mg; 0.05 cmolc dm-3 of Al; 7.59 cmolc dm-3 of H+ Al; 4.41 cmolc dm-3 of SB; 4.46 cmolc dm-3 of t; 12.00 cmolc dm-3 of T; 36.76% V; 23% sand, 26% silt, 51% clay and 1.20 dag kg-1 of OM. Yacon rhizophores from a production area in the municipality of Santa Maria do Jetibá/ES were harvested 3 d before planting. The rhizophores were selected and fractionated into 40-50 g pieces, washed in running water and immersed in a sodium hypochlorite solution (5% v/v) for 10 min. After treatment, the rhizophores were dried for 2 d in a ventilated and shaded place. The yacon was planted in April, which is a more productive period Silva et al. (2018a), in crops in this region, with cultivation extended to December, ending with the harvest. The fertilization was carried out by applying 200 g of tanned bovine manure at planting and 150 g for the cover fertilization, 90 d after sowing. This amount was equivalent to 152.24 kg ha-1 of nitrogen (approximating the 150 kg ha-1 recommended by Amaya (2000) based on nutrient contents in manure (1.74 N, 0.63 K2O and 0.35% P2O5)). After planting, monthly weeding was done with costal brush cutters, cutting between the plants, keeping residues below the soil surface. Sprinkler irrigation was used to supplement the monthly precipitation. However, during the months of May to August, there was a severe drought in the region that limited the use of irrigation. The experiment design was a randomized complete block design, with four replications, in a subdivided plot scheme. The plots consisted of three planting methods: grooved, pit, and ridges. The subplots had four planting depths: 5, 10, 15, and 20 cm. The planting grooves were 20 cm wide and 20 cm deep, and the ridges were 50 cm wide and 40 cm high (both done with hoes). The pits had a radius of 10 cm and depth of 20 cm (made with hand diggers). The experiment subplot had 28 plants, with an area of 11.2 m2 (3.5 x 3.2 m), providing 10 useful plants for the evaluations, for a total of 600 useful plants out of 1,680 plants in 672 m2. The planting was carried out at a spacing of 0.8 m between cultivation lines and 0.5 m between plants, representing a planting density of 25,000 plants/ha, based on the planting densities described by Seminário et al. (2003). The following characteristics were analyzed: sprouting rate index (SRI), vigorous sprouting rate (VSR), average sprouting time (AST), seedling mortality rate (SMR), leaf area at 120 and 240 d after planting (LA1 and LA2), dry mass of tuberous roots (DMTR), number of rhizophores and tuberous roots per plant (NR and TRP), leaf dry matter, and tuberous root yield (TRY). The initial development was evaluated every 15 d, always at the same time (8 h), for 75 d after planting (DAP). The evaluation methodology from Maguire (1962) was used, according to the vegetative stages: “Green Tip” (GT), appearance of bud coloring modifications, with a greenish tip