Effect of soybean plant density on stem blight incidence

Abstract

No-till system and high plant density are common practices in soybean crops of the Brazilian southern region, which has increased the incidence of stem and pod diseases. The objective of this study was to evaluate the effect of plant populations on stem blight incidence. The experiments were conducted in Muitos Capões Municipality, Rio Grande do Sul State, during the seasons 2006/07 and 2007/08, using cultivars BRS 255 RR and CD 213 RR. The evaluated populations had 12, 18, 24, 30 and 36 plants m-2, spaced 0.45 m between rows. The experimental plot units consisted of 5m width and 10m length, arranged in randomized blocks with four replicates. Stem blight incidence was quantified at phenological stages R5.1, R5.5, R6 and R7 and the collected data underwent regression analysis. Higher soybean plant densities caused a positive and significant increase on stem blight incidence in all four phenological stages for both cultivars and seasons. There was no significant difference for soybean grain yield according to the increase in plant population. Results indicated that soybean management preventing high plant densities can contribute to reduce stem blight incidence.

Agronomic optimal plant density for semiupright cowpea as a second crop in southeastern Brazil

“…By increasing plant density, perplant yield decreases but with an increase in per-unit area yield (Bezerra et al, 2008(Bezerra et al, , 2009Kamara et al, 2014;Li et al, 2020). Competition at high intensity in early stages of crop development can favor the emergence of unproductive plants and cause a decrease in the final productive stand and yield (Bezerra et al, 2008;Soratto et al, 2012) as well as increases the risk of lodging and impairing mechanized harvest procedures (Carciochi et al, 2019;Farias et al, 2019). Thus, the AOPD of a crop will be defined as the minimum number of plants per unit area for which resources are used most efficiently with a minimal competition among plants (Carciochi et al, 2019;Duncan, 1986).…”

“…Increasing the height for the pod insertion also facilitates mechanized harvest and reduces seed yield losses. Despite this potential benefit for increasing plant density, a parallel negative effect could occur by increasing the risk of lodging, potential canopy diseases, and seed costs (Carciochi et al, 2019;Farias et al, 2019).…”

Yield components of soybean cultivars under sowing densities

“…Possibly, these results reflect the increase in inter and intraspecific competition for soil resources, such as water and nutrients, caused by high sowing densities, which reduced the number of ramifications where reproductive gems develop, hence reducing the number of pods per plant, and therefore, the number of grains (Mauad et al, 2010;Ramos Junior et al, 2019). Another issue that should be taken into account is that population density increase can result in alterations in the microclimate inside the canopy (Masino et al, 2018), which might increase the incidence of pests and diseases (Farias et al, 2019). This could also affect yield components, especially considering the elevated accumulated rainfall amount observed on some days during the cycle (Figure 1).…”

Crop resilience via inter-plant spacing brings to the fore the productive ideotype

“…Reduced pollen-to-silking interval and increased harvest index, reflecting the partitioning of assimilates to the ear and grain, have been suggested as indicators of tolerance to drought (Duvick, 2005 ; Lopes et al, 2011 ). Crops grown at low populations are less susceptible to damage due to frost (Whaley et al, 2004 ), diseases (Jurke and Fernando, 2008 ; Farias et al, 2019 ; Omer et al, 2021 ), and lodging (Jurke and Fernando, 2008 ; Chauhan et al, 2021 ). The potential offset from the reduced population of lower seed cost is remarkable because seed represents one of the essential economic inputs (Spink et al, 2000 ); reasonably minimized seed waste might be significant concerning food adequacy and security in the future (Tokatlidis, 2014 ).…”