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CROP PHYSIOLOGY & METABOLISM

Radiation Interception and Yield Response to Increased Leaflet Number in Early-Maturing Soybean Genotypes

^a North Carolina State Univ., Dep. of Crop Science, Williams Hall 4411, PO Box 7620, Raleigh, NC 27695-7620
^b Univ. of Arkansas, Dep. of Crop, Soil, and Environmental Sciences, 1366 W. Altheimer Drive, Fayetteville, AR 72704
^c Univ. of Arkansas, Agricultural Statistics Laboratory, Agriculture Annex 101, Fayetteville, AR 72701
^d Univ. of Arkansas, Dep. of Crop, Soil, and Environmental Sciences, 115 Plant Science Building, Fayetteville, AR 72701
^e 5601 Sunnyside Ave., Beltsville, MD 20705

^* Corresponding author (lpurcell{at}uark.edu).

Early-maturing soybean [Glycine max (L.) Merr.] cultivars require less irrigation than full-season cultivars and may mature before drought periods most often occur in the midsouthern United States. These cultivars require high plant-population densities for radiation interception and acceptable yields, which increase costs. We hypothesized that seven-leaflet genotypes would have greater leaf area per plant, resulting in more radiation interception and higher yield than near-isogenic three-leaflet genotypes at similar populations. Near-isogenic lines from maturity groups 00 to 1.8 were seeded at rates from 4 to 80 m^–2. The fraction of photosynthetically active radiation (PAR) intercepted by plots was measured using digital imagery and used to estimate cumulative intercepted PAR (CIPAR). Although seven-leaflet isolines had greater leaf area per leaf than three-leaflet isolines, leaf area per plant was similar between three- and seven-leaflet isolines because the three-leaflet isolines had a slightly greater number of main-stem leaves than seven-leaflet isolines. Generally, seven-leaflet isolines had 10 to 21% greater CIPAR at populations 40 m^–2 compared to three-leaflet isolines. At populations 20 m^–2, seven-leaflet isolines generally had higher yields than three-leaflet isolines, but yields at these low populations were inherently low and agronomically unacceptable.

Abbreviations: CIPAR, cumulative intercepted photosynthetically active radiation • DAE, days after emergence • FPARI, fraction of photosynthetically active radiation intercepted • GENO, genotype • LA, leaf area • LN, leaflet number • MG, maturity group • PAR, photosynthetically active radiation • PD, population density • REP, replication • Rs, solar radiation • SR, seeding rate