:Grain yield variability in soybean [Glycine max] under no-tilled systems in south, Santa Fe Argentina.

BACIGALUPPO, SILVINA; BALZARINI, MÓNICA; DARDANELLI, JULIO; GERSTER, GUILLERMO RAÚL; ANDRIANI, JOSÉ MIGUEL; ENRICO, JUAN MARTÍN; BODRERO, MARCELO L.

Beijing, China. CN.

Conferencia; :World Soybean Research Conference; 2009

Southern Santa Fe in Argentina, cultivates the 80% of the agricultural area (1.700.000 ha) with Soybean (Glycine max) and more than 90% is grown under continuous no tillage. Grain yield gaps are often observed among fields, even located at short distances. Argiudolls are the main soils in this area that usually show highly compacted layers in the upper horizons where macro-pores are lost (%Md). The objective of this work were identify the most important meteorological and soil variables that explain grain yield variation in soybean and quantify their relative impact, in the region. Data, including 175 soybean crops, were collected from farmer fields during 4 growing seasons, covering a wide range of soil management history and environmental conditions. Multiple linear regression and multivariate techniques were used to model soybean yield variability. Threshold values of 180 mm for cumulative rainfall in the reproductive stage (ppR2-R7) and 200 mm for soil water available at emergence, separated different situations: a) environments above these values where 48 to 51% of total variation in soybean yield was explained by mean temperature between R2-R5, cumulative solar radiation during the R5-R7 period, combined with soil variables like organic matter and %Md, or hydraulic conductivity (Ksat); and b) environments below the threshold where ppR2-R7 and %Md or Ksat accounted for 72-88% of soybean yield variability. The highest soybean yields were always achieved in fields that showed a better soil physical condition.

Keywords Glycine max, yield variability, environment, meteorological and soil variables.