Performance of corn genotypes

Given the great diversity of corn genotypes on the agronomic market, a careful choice is necessary, which favors positive interaction with the specific growing environment.

The choice of hybrid corn is a fundamental action for the quality of a production system, which Generally speaking, it is responsible for 50% of final productivity. Corn is a crop of high economic importance, which requires studies with the aim of meeting its nutritional and soil-climatic requirements to obtain its productive potential. To this end, knowledge of the characteristics of each cultivar such as type of genetic improvement, resistance to lodging, cycle duration, thermal requirement, plant arrangement, among others (Farinelli et al., 2012).

As the improvement genetic corn hybrids are classified according to their genetic basis in single, double, triple hybrids and varieties (among others). Single or triple hybrids can be genetically modified or not, as there can also be a “top cross” which is the result of crossing of one variety and two intervarietal hybrids and one simple hybrid. You greater results with productivity are found in simple, triple hybrids and doubles, but the seed cost is higher, along with the management required to express productive potential (EMBRAPA, 2016).

Second recommendations from Embrapa, the cycles are divided according to the accumulation of heat units in degree days (GD) from emergence to flowering and are divided into super early (less than 830 GD), precocious (830 GD to 890 GD), semi-precocious and normal (greater than 890 GD). For the calculation of the thermal sum it is recommended to disregard the maximum temperatures that are equal to or greater than 30ºC and minimum temperatures lower than 10ºC, assigning these values ​​themselves. Another important aspect in productivity of corn is the arrangement of plants, which is represented by the adjustment in spacing and plant density (Farinelli et al., 2012). This is related to the chosen cultivar, sowing time and soil type. Currently it has been In practice, the increase in population density and the decrease in spacing, to meet the requirements of new cultivars that tend to be earlier, have a smaller size, more erect angulation and greater productivity. With high investment in technology, Demétrio et al. (2008) reports that the best spatial arrangement of plants is included in a population of 75000 plants/ha to 80000 plants/ha with 40cm spacing. Now Farinelli et al. (2012), corroborates the spacing between rows, but infers that the Optimal populations range from 60000 plants/ha to 80000 plants/ha.

To obtain sowing and quality growth, the different factors of pre-sowing and sowing, as characteristics of the cultivar (cycle, potential production and resistance to biotic and abiotic factors), in addition to the spacing between rows and choosing the best population density for the location. By virtue of these factors, the objective was to characterize the production of 19 corn hybrids for the edaphoclimatic conditions of Santa Maria, in Rio Grande do Sul.

O experiment was conducted in the 2015/16 summer harvest, at the Department of Phytotechnics at the Federal University of Santa Maria, RS ((29º42' S, 53º42' WW and 122 meters altitude). The soil in the area is classified as Red Argisol Arenic Dystrophic (EMBRAPA, 2006). The climate refers to the classification of Köppen, type Cfa, (humid subtropical without defined dry season and summers hot). The average air temperature for the months of June and July is 13,8 °C, and January is 24,7 °C. Normal annual precipitation is 1712,4 mm, evenly distributed throughout the four seasons (Heldwein et al., 2009).

Sowing was carried out on the day 19/10/2015, with a fertilizer seeder at a density of 7 seeds/m² and spacing between rows of 45 cm. Fertilization was carried out in accordance with the Soil Chemistry and Fertility (CQFS, 2004), based on chemical analysis of the collected soil. The management phytosanitary treatment was carried out in accordance with the technical indications for the crop (EMBRAPA, 2013). The harvest was carried out manually in the two central rows with a usable area of ​​6,97 m². Posteriorly mass of a thousand grains and total productivity were evaluated, being corrected to 13% of humidity. Analysis of variance (F test) and means were compared by the Scott-Knott Test, at a level of 5% error probability with the aid of the Sisvar software (FERREIRA, 2008).

In relation to grain productivity, the most productive were AG 8690 PRO3, AG 8789 PRO3, BG 7046, P 30F53 YHX, AG 9025 PRO3, NS 56 PRO and DKB 290 PRO3, with highlights for the first three mentioned producing, respectively, 10063 kg/ha, 10039 kg/ha and 9693 kg/ha (Table 1). This represents a 28% higher production compared to the average for Rio Grande do Sul (7160 kg/ha) and 56% compared to the national average (4389 kg/ha) (CONAB, 2016). Thus, these hybrids are suitable for the Santa Maria, presenting economically adequate productivity combined with a good management and environmental conditions. Some common aspects can be highlighted of these high-yielding hybrids as a genetic basis, early cycle and insect resistance technologies (Table 2). All hybrids plus productive devices are simple and, with the exception of the BG 7046, have VT PRO or Herculex I, providing resistance to insects of the lepidoptera order, such as cartridge caterpillar.

A hypothesis for some hybrids not obtaining high productivity may be related to the population of plants. For reasons of practicality in implementing the experiment, we chose for standardizing seed density for all cultivars. Each of these genotypes have different requirements regarding spacing and the population of plants, which can impact approximately 20% on production, the change in plant arrangement (Almeida et al., 2000).

In the mass variable of thousand grains according to Table 3, the cultivars with the highest results were AS 1666 PRO3, AG 9025 PRO3 and NS 56 PRO, with values ​​of 440g, 417,66g and 406,66g. These results are associated with the occurrence of lack of of rain during the grain filling period. As a result, some genotypes do not obtained a weight similar to that reported by the seed breeder. (FORSTHOFER et al., 2006; LEE; TOLLENAAR, 2007).

A diversity of corn genotypes in the agronomic market is great, as is It is necessary to make a careful choice that most favors positive interaction between genotype and specific environment. Attention is needed regarding the quality of seed and qualified supplier certification. Furthermore, for any specific doubts, it is recommended to contact an agronomist, and for greater knowledge of the genotype, it is important to contact representatives of the seeds.

Anderson da Costa Rossatto, Guilherme Bergeijer da Rosa, Lucas Bruning, Glauber Monçon Fipke, Thomas Newton Martin, UFSM

Article published in issue 228 of Cultivar Grandes Culturas, May, 2018.