Assimilatory Capacity Effects on Soybean Yield Components and Pod Number

Abstract

Soybean [Glycine max (L.) Merr.] yield is more restricted by assimilatory capacity (source strength) during the reproductive (R1 to R7) compared with vegetative period (emergence to R1). Although pod number (per unit ground area) is recognized as an important factor affecting yield, the period in which this yield component is source restricted has not been clearly identified. Therefore, the objective of this study was to determine this period by identifying yield components through which source strength affects pod number and finding when these yield components are determined. Field studies were conducted during 1991 and 1992 with ‘Centennial’ soybean at Baton Rouge, LA, on a Mhoon silty clay soil (fine‐silty, mixed, nonacid, thermic Typic Fluvaquent). Treatments were partial defoliations designed to create light interception differences during R1 to R7. Yield was reduced 23% by defoliation. Harvest index, which was 0.59 for the control, ranged from 0.56 to 0.60 for the defoliation treatments. Source strength influenced pod number (per unit ground area) through branch dry matter, branch number, branch node number, and pods per reproductive node on the whole plant. Pods per reproductive node were regulated by pod initiation (pods at least 0.5 cm long) and/or abortion initiated pods. Determination of final pod number occurred at 10 to 12 d after R5. In conclusion, pod number was source restricted from R1 to 10 to 12 d after R5. Stresses that restrict source strength during this period should be avoided to optimize pod number and yield.

ABA Increased Soybean Yield by Enhancing Production of Carbohydrates and Their Allocation in Seed

“…This period is called "critical period" since crop yield is established at this time (Egli, 1998). A close relationship has been found between the number of seeds per area unit and the plant growth rate during a critical period, especially between R3-R6, independently of the changes in growth for rest of the plant cycle (Jiang & Egli, 1995;Board & Tan, 1995). During the critical period both the production of reproductive organs and its survival are defined.…”

Efeitos De Níveis E Épocas De Desfolhamento Sobre O Rendimento E Os Componentes Do Rendimento De Grãos Da Soja

“…Pesquisas demonstram que o número de legumes por planta são mais responsivos a alterações na fonte que os outros dois [4], uma vez que o número de grãos por legume e peso do grão possuem maior controle genético e por isso apresentam menor amplitude de variação [6]. Estudos relatam que queda do rendimento promovida pela redução da área foliar está relacionada com o menor número de legumes por planta [4].…”

Interrelationships among yield components of chickpea in semiarid environments

“…This type of information is also useful for chickpea breeders to establish selection criteria in genetic manipulation. For example, selection for highyielding cultivars through specific traits requires knowledge not only on the mechanisms of seed yield formation but also on the physiological processes relative to setting pods (Egli and Yu 1991), forming the seed number (Board and Tan 1995), and filling these potential fruiting sites (Ball et al 2001).…”