Radiation Use Efficiency and Biomass Production in Soybean at Different Plant Population Densities

Abstract

As population density (POP) increases in a soybean [Glycine max (L.) Merr.] crop, maximum light interception (LI) occurs earlier in the season. Earlier canopy closure would be expected to increase the cumulative radiation intercepted. We hypothesized that if radiation use efficiency (RUE) was constant across a range of population densities in a nonstressful environment, then increasing POP would increase biomass at the end of the season. To test this hypothesis, we evaluated the response of total biomass produced during the season to cumulative intercepted photosynthetically active radiation (PAR) in field experiments at Fayetteville, AR, with soybean cultivars selected from Maturity Groups (MGs) 00 to IV. Additionally, from field experiments at Keiser, AR, with MG IV soybean cultivars, we assessed the response of RUE to POP. At both locations with MG IV cultivars, a late sowing date shortened the life cycle of the crop by 13 to 25 d compared with an early sowing date, resulting in less PAR accumulated. Similarly, early maturing cultivars had less time for PAR and biomass accumulation relative to later maturing cultivars. At Keiser, in three of the four environments, RUE decreased linearly by 26 to 30% as the POP increased from 7 to 135 plants m(-2). Final biomass at the end of the season, as a function of PAR accumulated from emergence to the full-seed-size stage of development, responded linearly to intercepted PAR up to approximately 400 MJ m(-2). Above 400 MJ m(-2), the response was curvilinear with little increases in biomass>700 MJ m(-2). Our data clearly indicate that RUE decreased as POP increased and that maximum biomass production in these environments was not limited by intercepted PAR.

A high seed yield and associated attributes of dry matter production achieved by recent Japanese soybean cultivars

“…The reason for the inconsistencies between the current and previous studies would be attributed to the narrow range of planting density (12.8 and 18.5 plants m −2 in current study in comparison to the wide range (7 to 135 plants m −2 ) in Purcell et al (2002). Considering the RUE decrease with increasing planting densities was about .002 g MJ plant −1 (Purcell et al, 2002), the difference of planting density (ca. 6 plants m −2 ) in this study is too narrow to assess the difference of RUE having the standard error about .08 (Table 3).…”

“…Achieving complete ground cover by the R1 stage or shortly thereafter is required to achieve maximum yield (Andrade et al, 2002;Ball et al, 2000;Board, 2000;Lee et al, 2008;Purcell et al, 2002). The light interception in our experiment reached 80% about 1 week after R1 in 2014 and around R1 in 2015, and reached 90% at 10 d after R1 in 2014 and 2-6 d after R1 in 2015 (Tables 1 and 3).…”

“…On the other hand, Weber (1965, 1966) demonstrated constant RUE across a wide range of plant population, and Purcell et al (2002) found that RUE decreased with increasing density. The reason for the inconsistencies between the current and previous studies would be attributed to the narrow range of planting density (12.8 and 18.5 plants m −2 in current study in comparison to the wide range (7 to 135 plants m −2 ) in Purcell et al (2002). Considering the RUE decrease with increasing planting densities was about .002 g MJ plant −1 (Purcell et al, 2002), the difference of planting density (ca.…”

“…The 1-m probe was connected with the sunshine sensor using a 25-m cable and was attached to a handheld computer to store the data. The mean of five measurements per plot was used to calculate FIPAR according to Purcell (2000) and Purcell et al (2002): Daily total intercepted solar radiation was calculated based on the daily total solar radiation measured at the meteorological station, multiplied by the FIPAR value measured with the SunScan instrument. FIPAR for days on which no measurements were taken was estimated by means of linear interpolation between the two closest measurements.…”

The shoot dry matter accumulation and vertical distribution of soybean yield or yield components in response to light enrichment and shading

“…Increase of density to a certain extent in determinate area is an important way to achieve higher seed yield (Liu et al, 2008). However, excessive high density resulted in decrease of radiation use efficiency and hence the increase reached yield ceiling (Purcell et al, 2002). Under light-enriched treatment condition, the appropriate density for a certain soybean cultivar will increase and crop yield components also will change.…”