Productive performance of soybean cultivars

The choice of cultivars suitable for the technological level that will be used by the soybean farmer is one of the decisive factors in the formation of grain productivity components. Therefore, it is essential to know the main characteristics and productive stability of the genetic material, in order to position it according to the cultivation conditions.

Choosing the cultivar to be sown is an essential decision to begin good crop management. It is estimated that in the selection, sowing and establishment process, 50% of the productivity of the soybean crop is defined. Currently, more than 300 soybean cultivars (out of 1486 registered cultivars) are sold throughout the country. Some of its particularities need to be well clarified and attested for each cultivation condition. They are, the maturation group, the type of growth, the response to fertilization, the rusticity to diseases, among others. In order to resolve some of these responses, an experiment was conducted with soybean cultivars, with the aim of making the productive characterization of each of these materials, for the edaphoclimatic conditions of Santa Maria, Rio Grande do Sul.

The experiment was conducted in the experimental area of ​​the Department of Phytotechnics at the Federal University of Santa Maria (UFSM). The soil in the area is classified as Dystrophic Red Argisol, belonging to the São Pedro Mapping Unit (EMBRAPA, 2006). The region's climate, according to the Köppen classification, is type Cfa (HELDWEIN et al., 2009).

Sowing was carried out on November 10, 2014 with a direct planting fertilizer seeder, using 20 suitable seeds m/linear, spaced 0,45m apart and 350 kg/ha, of NPK formulated fertilizer (05-20-20). The seeds were treated with insecticide and fungicide and inoculated with bacteria of the genus Bradyrhizobium spp. on the day of sowing. Other crop management was carried out in accordance with technical recommendations.

42 soybean cultivars were evaluated, as described in Table 1. The experimental design was randomized blocks with four replications. The experimental unit totaled 15,75m². The harvest was carried out according to a maturation physiological of each cultivar, with its humidity adjusted to 13%. Grain mass was determined by directly counting eight replicates of 100 grains. Analysis of variance (F test) and mean comparison test were carried out Skott-Knott (α≤0,05) with the help of SISVAR software^® (FERREIRA, 2008).

Regarding grain productivity (Table 1), the cultivars DM 5958 RSF IPRO, TMG 7062 IPRO, SYN 1365 RR and M 5947 IPRO. All mentioned exceeded the mark of 4,2 t/ ha (70 bags/ ha). These brands represent 50% more than the average for the state of Rio Grande do Sul (2835 kg/ha) and 42% more grain productivity in the country (2998 kg/ha). They were placed under the same cultivation conditions for all materials, therefore, it is considered that these four cultivars have high productive capacity and have adapted well to this year's conditions in the Santa Maria region.

Some common aspects can be highlighted among these cultivars, such as genetic basis, relative maturity group, type of growth, among others. With the use of new added technologies, seeds, cultivars have increase in productivity; protection for main caterpillars that attack soybean cultivation; It is glyphosate tolerance. All four cultivars have the indeterminate growth type and medium cycle (GMR = 5.8 - 6.5). It should be noted that the SYN 1365 RR cultivar does not have the INTACTA technology, and is also not recommended for cultivation in the RS 101 region, even though it corresponds to high grain productivity. The TMG 7062 IPRO cultivar also incorporates INOX technology into its genetic base, where there is the presence of a gene resistant to Asian rust (Phakopsora pachyrhizie), combined with maximum expression of productive potential and high grain mass.

However, it should be noted that plantability management, especially the number and distribution of plants, must be adjusted and observed for each cultivar and this was not always possible for this experiment. Once this adaptation is carried out, the plant will adjust the emission of leaf branches and lengthening of the internodes, providing better productive performance for the cultivars (MUNDSTOCK; THOMAS, 2005). The correct arrangement of plants is essential in reducing intraspecific competition.

Competition between plants has been a subject of research for many years, to standardize the canopy from seed germination, maturation and harvest. The works indicate changes in plant architecture inherent to the reduction of spacing between rows (VENTIMIGLIA et al., 1999) and adjustment of the plant population (PIRES, COSTA; THOMAS, 1998). The effects of different levels of vigor between seeds within a batch (KOLCHINSKI, SCHUCH; PESKE, 2005); uniformity in emergence (MEROTTO JUNIOR et al., 1999); the initial size of the seedlings (VANZOLINI et al. 2007); seed yield of individual plants within communities (SCHUCH; KOLCHINSKI; FINATTO, 2009); among others.

As for grain mass, cultivars were observed TMG 7062, BMX TURBO RR, TEC 6029 IPRO, TEC 5936 IPRO and FUNDACEP 66 RR, with emphasis on the latter with 223 grams/thousand grains. Just like the number of grains per pod, grain mass is a characteristic value for each cultivar, however, this does not prevent this value from changing depending on the environmental and management conditions to which the crop is subjected (SILVA et al. , 2011).

The cultivars TEC 7849 IPRO and TEC 5718 IPRO, for example, had technical information from the distributor 148 grams/thousand grains at 176 grams/thousand grains and 182 grams/thousand grains to 210 grams/thousand grains, respectively. In the experiment, a divergent value of 119 was found grams/thousand grains and 142 grams/thousand grains, respectively. The increase in population density caused plasticity in the plant (etiolation/lodging), modifying it in a way that harmed grain filling. Authors such as PIRES et al. (1998) proved that there is a change in grain mass when an inadequate plant population is used. Another aspect concerns the increase in grain mass and size when the spacing between plants is equidistant, and this increase also occurs with a decrease in population (MOORE, 1991).

Therefore, the choice of the appropriate cultivar for the technological level that will be used by the soybean farmer, as well as favorable environmental factors (biotic and abiotic) are decisive in the formation of grain productivity components. Therefore, the importance of knowing the main characteristics and productive stability of the genetic material is highlighted, positioning it according to the cultivation conditions.

 

Soy and productivity challenges

Brazil ended the 2014/15 harvest as second in the world in soybean production, with 95 million tons, surpassed only by the 108 million tons produced in the USA (USDA, 2015). The sown area in Brazil was 32 million hectares, with an average productivity of approximately 3 t/ha (±50 sc/ha). In Rio Grande do Sul, there was an increase in the area cultivated with the oilseed (5,6%) in relation to the previous harvest, with productivity below the national average (2,8 t/ha) (CONAB, 2015). The Rio Grande do Sul crop has been increasing its average grain yields (8,1% compared to the previous harvest), however, it is still far from the national averages. This may be linked mainly to the different crop management conditions arising from the relief conditions. Rio Grande do Sul belongs to soybean macro-region number 01, with edaphoclimatic regions identified as 101, 102 and 103 (EMBRAPA, 2014). The edaphoclimatic region 101 covers most of the state's territory, with the predominance of municipalities for cultivation in lowland areas. Due to the characteristics of the soil, generally argisols, there is excess humidity and poor straw management. Adapting cultivation to lowland areas can also result in lower yields. On the other hand, the other regions 102 and 103 predominate in more technical areas and the adoption of the long-standing direct sowing system means that the average productivity is higher in relation to region 101. Management practices must be adopted for each situation, seeking always, maximum economic return in the short term (productivity in R$/ha) and in the long term (conservation of resources).

 

Glauber Monçon Fipke, Fabiano Colet, Anderson da Costa Rossatto and Thomas Newton Martin, UFSM

Article published in issue 203 of Cultivar Grandes Culturas.