Felipe Gutheil Ferreira

Estimativa do potencial de rendimento por estrato do dossel da soja, em diferentes arranjos de plantas

The soybean yield potential can be modified by plant arrangement. This modification might be the result of the diferential contribution of the canopy strata for the potential determination. The experiment was conducted at the Agronomic Experimental Estation of the Universidade Federal do Rio Grande do Sul, in Eldorado do Sul, Rio Grande do Sul, Brazil, in the 2000/01 growing season. The objectives were to evaluate the yield potential by stratum of soybean canopy in different plant arrangement, under two water availability. The cultivar tested was BRS 137, in no-till planting. Water availability (irrigated an no irrigated), row spacing (20 and 40cm) and population levels (20, 30 and 40 plants m-2) were tested. The yield potential was estimated in the beginning of grain filling (R5). It was considered that all flowers and pods present at this stage were able to reach maturation, forming grains and contributing to yield. The canopy was divided in three strata by plans paralel to soil surface. The irrigated treatment (14976kg ha-1) presented larger total plant yield potential and yield in R8 (maturity) than without irrigation (12148kg ha-1), similar to what ocurred in all soybean canopy strata. The plant arrangement with 20cm of row spacing, independent of population, presented, on the average, larger yield potential in R5 (14970kg ha-1) compared to 40cm row spacing (12154kg ha-1). The same was also noticed at the medium soybean canopy stratum. At maturity the plant arrangement 20cm of row spacing and population of 20 plants m-2 yielded more than 40cm (6442kg ha-1 compared to 4396kg ha-1), due to larger yield at the medium and botom stratum. There was a linear decrease in yield potential with increase of plant population, with row spacing reduction (20cm), explained by the same behavior of the canopy strata. Similar response was obtained for yield in R8. The soybean canopy strata contributed differently to yield potential with the plant arrangement modification, due to the diferential number of reproductives structures (R5) and yield components (R8) alteration.

Potencial de rendimento da soja durante a ontogenia em razão da irrigação e arranjo de plantas

The quantification of reproductive structures during the ontogeny allows to estimate soybean yield potential (YP), making possible to quantify the effect of environmental factors and management practices on the production and fixation of these structures. This work aimed to determine the effect of water availability and plant arrangement on the YP and its components, during ontogeny of two soybean cultivars. Treatments were two water availability (irrigated and non irrigated), two cultivars (BRS 137 and BRS 138), and three row spacings (20 cm, 40 cm and 20 and 40 cm in skip row). The average YP obtained was of 15,295 kg ha-1 at blooming; 12,325 kg ha-1 during legume formation; 5,508 kg ha-1 at the beginning of grain filling and 4,315 kg ha-1 in maturation phase. The irrigated treatment had higher YP, due to the larger flower and pod production and fixation, more grains per pod and heavier grains, in relation to non irrigated treatment. There was no significant difference among the row spacings tested. The cultivar BRS 137 presented greater YP during the ontogeny than BRS 138, due to less flower abortion, heavier grains and more grains per pod.

Métodos para a estimativa do potencial de rendimento da soja durante a ontogenia

O objetivo deste trabalho foi estudar metodos para a estimativa do potencial de rendimento da soja durante a ontogenia. Os experimentos foram realizados em Eldorado do Sul, RS, durante as safras de 1996/1997, 1999/2000 e 2000/2001. Os tratamentos constaram de cinco cultivares de soja, FT-Saray, IAS 5, IAS 4, FT-Abyara e FEPAGRO RS-10. Cinco metodos foram utilizados para estimar o rendimento que seria obtido se todas as estruturas reprodutivas presentes no florescimento e no inicio do enchimento de graos, produzissem graos na maturacao. O potencial de rendimento no florescimento e no enchimento de graos, apresentou alta correlacao com o numero de flores e estruturas reprodutivas, respectivamente. Verificou-se, tambem, correspondencia entre os metodos. Nao houve, na maioria das vezes, correlacoes significativas entre o potencial, no florescimento e enchimento de graos, e o rendimento de graos na maturacao. Os metodos estudados constituem ferramentas importantes para o manejo, quando utilizados para comparar o potencial de rendimento durante a ontogenia.