Abstract
Canola (Brassica napus L. var oleifera) is a potential crop due to the growing world demand for vegetable oil. This work aims to evaluate the performance of five canola hybrids in three sowing dates in Jataí-GO. The experiment was conducted in the year of 2017, in a randomized block design, with subdivided plots and four replications. Plots were composed by three sowing dates (03/03, 03/10 and 03/17) and subplots by the canola hybrids Hyola 50, Hyola 61, Hyola 433, Hyola 571CL and Hyola 575CL. Seedling emergence, inicial and final plant population, flowering, maturation, plant height, plant survival index and grain yield were evaluated. The thermal sum calculation was performed with the phenological data. Results were submitted to analysis of variance and means were compared by Scott Knott test at 5% of probability. The plants survival index highlighted Hyola 433, Hyola 571CL and Hyola 575CL hybrids. Grain yield varied according to hybrid and sowing date. In the edaphoclimatic conditions of this study, in the year of 2017, the best agronomic performance was observed in the first sowing date for the canola hybrids Hyola 433 and Hyola 575CL and in the second sowing date for the canola hybrid Hyola 571CL.
Highlights
The main canola growers are European Union, Canada, China, India, and Australia (USDA, 2017), all of them located at high latitudes, between 35o and 55o
Genotypes cultivated in Brazil present lower photoperiod sensitivity and higher response to air temperature instead of rapeseed open pollination varieties grown in the past (MONTEIRO, 2009)
In the edaphoclimatic conditions of this study, in the year of 2017, the best agronomic performance was observed in the first sowing date for the canola hybrids Hyola 433 and Hyola 575CL and in the second sowing date for the canola hybrid Hyola 571CL
Summary
Canola (Brassica napus L. var. Oleifera) is one of the most important oilseeds in the world and one of the main sources of edible vegetable oil, being preferred because its low saturated fatty acid content (TAN et al, 2009). Over the past 40 years global canola production has grown rapidly, ranking from sixth to second most produced oilseed crop in the world (USDA, 2017). The main canola growers are European Union, Canada, China, India, and Australia (USDA, 2017), all of them located at high latitudes, between 35o and 55o. In Brazil, research on canola cultivation began in 1974 in Rio Grande do Sul State and in the 1980s in Paraná State, where it was grown the spring specie, Brassica napus, since it does not require vernalization and has low photoperiod sensitivity (MORI et al, 2014; TOMM et al, 2009b). Canola plant is originally adapted to mild conditions and regularly distributed rain throughout its growth period (MENDONÇA et al, 2016). Genotypes cultivated in Brazil present lower photoperiod sensitivity and higher response to air temperature (thermal sum) instead of rapeseed open pollination varieties grown in the past (MONTEIRO, 2009). The air temperature is the most important environmental factor in regulating canola growth and development (THOMAS, 2003). Commercial crops in Brazil are concentrated in the southern region. According to CONAB (2018), an average yield of 1,358 kg ha-1 is expected and a 48 thousand tons production in 35.5 thousand hectares area. Canola cultivation is expanding to lower latitudes in Brazil, a process called tropicalization. There was a commercial crop in Goiás, in 2004, partially encouraged by the results of a trial in five different places, in which it was obtained grain yields from 2,100 and 2,400 kg ha-1. In the southwest Goiás, canola crop can be an alternative for diversification and income generation as a second harvest (EMBRAPA, 2017). Brazilian demand for canola crop is a great incentive for research works, considering that there are limited technical scientific information regarding crop management in Brazil especially in low latitude regions. The highest grain yield is obtained when canola is cultivated at 17 cm between rows and density of 45 plants per square meter. Best yield results were observed by spacing rows until 45 cm (BANDEIRA et al, 2013; TOMM, 2007). According to Mendonça et al (2016) the best sowing period recommended for Goiás State is Received: 15/04/19 Accepted: 01/12/20 Biosci. J., Uberlândia, v. 36, Supplement 1, p. 36-47, Nov./Dec. 2020 http://dx.doi.org/ BJ-v36n0a2020-48258 Canola agronomic... from early February to mid-March, respecting agricultural zoning indications by the countrys agriculture department (BRASIL, 2012). Although its importance as an alternative crop in Brazils Midwest, there are few studies on canola cultivation at that important agricultural area, considering the most adapted hybrid to that edaphoclimatic condition and the best sowing dates. This work aims to evaluate the performance of five canola hybrids in three sowing dates in Jataí-GO. Each plot consisted of five sowing lines, five meters each, 0.45 m spacing and 62 seeds per m2. Sowing was handy done by the adhesive tape technique. In the laboratory, seeds were arranged in an adhesive tape, which were later taken to the field and placed in the planting line, previously prepared by an automatic planter. Planting fertilization was done by 30 kg ha-1 of N, 60 kg ha-1 of P2O5 and 50 kg ha-1 of K2O applied in the soil surface, using as source, urea, triple superphosphate and chloride potassium, respectively. When seedlings were in rosette stage, 50 kg ha-1 of nitrogen fertilizer was applied, using ammonium sulfate as source of N. Fertilization was performed according to results obtained from soil analysis and from the brasilian agricultural research companys recommendations (TOMM, 2007) for canola cultivation. During crop development, hand weeding, herbicides and insecticides were used for the control of weeds, Myzus persicae, Brevicoryne brassicae, Diabrotica speciosa and Ascia spp. Hybrids performance and sowing date influence were evaluated by the following phenological and phenometric variables: Seedlings emergence - when 50% of seedlings were emerged in each plot; Initial plant population - based on the number of plants in a row (4 meters long), one month after sowing; Flowering - when 50% of plants had at least one flower; Maturation – when 50% of seeds changed to dark color in pods located in the middle of the plants main raceme; Plant height - using a graduated ruler, plant height was measured from soil surface to the top of the largest raceme with pods; Final plant population - based on the number of plants harvested in the useful area (4.05 m2 on each subplot); Grain yield – grains from useful area were harvested, weighed and moisture was determined and corrected to canola moisture reference of 9% for yield calculation; Plants survival index was calculated by the survival percentage from early to late plant population. The accumulated thermal sum calculation was performed from the phenological data according to Arnold (1960): TS= ΣTSd; TSd= Ta-Tb; on what: TS = accumulated thermal sum; TSd = daily thermal sum; Ta = Average air temperature; Tb = basal temperature. The basal temperature of 5 °C was considered as indicated by Morrison et al (1989), Nanda et al (1995), Iriarte and Valetti, (2008) and Dalmago et al (2009). The thermal sum was obtained for the following development subperiods: emergence to early flowering (EM-EF), early to late flowering (EF-LF) and emergence to physiological maturation (EM-PM). Data were submitted to analysis of variance and means were compared by Scott Knott test at 5% of probability. Table 1 shows the results of the analysis of variance for initial and final plant population, plants survival index, days between emergence to early flowering (EM-EF), early to late flowering (EF-LF) emergence to physiological maturation (EM-PM), thermal sum for each subperiod expressed in degree-day, plant height, and grain yield of five canola hybrids, in three sowing dates.
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