Soil, cultivation practices and seeds sources
Two experiments were conducted in greenhouse conditions at the University of Missouri, Columbia, MO, USA,between July and October, 2009. Temperatures were maintained at 26–30 : 22–26C
(day ⁄ night) with a 12-h photoperiod of full sunlight (midday irradiance of 400–700 nm) and a photosynthetic photon flux density of1500 lmol m)2s)1at the top of the leaf canopy. Plants were grown in 5-dm)3 clay pots filled with sieved (5 mm)
air dry soil from the A horizon of a Mexico silt loam soil(fine, smectitic, mesic Aeric Vertic Epiaqualfs).
Soil in allpots was maintained at water content of 80% water-hold-ing capacity (0Æ33 g ⁄ g) with N-free water throughout the experiment. The soil physicochemical properties were(Corg:25Æ2gkg)1;P:15Æ87; K: 45Æ86; Ca: 1782Æ64;
Mg:123Æ89; Fe: 80Æ70; Mn: 43Æ23; B: 14Æ06; Cu: 1Æ78; Zn: 9Æ82;Mo: 1Æ61 mg kg)1;pHCaCl2:6Æ77).
Seeds of ‘BRS 242’ (GR1) and ‘AG3539’ (GR2) soybean cultivars were sterilized for 2 min in 2% NaClO and then inoculated with a mixed culture of Bradyrhizobium japonicum, strains SEMIA587 and SEMIA 5019 (100 ml50 kg)1seed) at a concentration of 5 · 109 rhizobia pergram. This inoculation rate resulted in effective root nodules clustered on the upper tap roots of soybean by 14 days after emergence, indicating efficient N fixation bythe B. japonicum inoculant strains. Six seeds were sown per pot at 3 cm depth and thinned to one plant per potat the one-leaf (V1) growth stage.
Soil, cultivation practices and seeds sourcesTwo experiments were conducted in greenhouse conditions at the University of Missouri, Columbia, MO, USA,between July and October, 2009. Temperatures were maintained at 26–30 : 22–26C (day ⁄ night) with a 12-h photoperiod of full sunlight (midday irradiance of 400–700 nm) and a photosynthetic photon flux density of1500 lmol m)2s)1at the top of the leaf canopy. Plants were grown in 5-dm)3 clay pots filled with sieved (5 mm)air dry soil from the A horizon of a Mexico silt loam soil(fine, smectitic, mesic Aeric Vertic Epiaqualfs). Soil in allpots was maintained at water content of 80% water-hold-ing capacity (0Æ33 g ⁄ g) with N-free water throughout the experiment. The soil physicochemical properties were(Corg:25Æ2gkg)1;P:15Æ87; K: 45Æ86; Ca: 1782Æ64; Mg:123Æ89; Fe: 80Æ70; Mn: 43Æ23; B: 14Æ06; Cu: 1Æ78; Zn: 9Æ82;Mo: 1Æ61 mg kg)1;pHCaCl2:6Æ77).Seeds of ‘BRS 242’ (GR1) and ‘AG3539’ (GR2) soybean cultivars were sterilized for 2 min in 2% NaClO and then inoculated with a mixed culture of Bradyrhizobium japonicum, strains SEMIA587 and SEMIA 5019 (100 ml50 kg)1seed) at a concentration of 5 · 109 rhizobia pergram. This inoculation rate resulted in effective root nodules clustered on the upper tap roots of soybean by 14 days after emergence, indicating efficient N fixation bythe B. japonicum inoculant strains. Six seeds were sown per pot at 3 cm depth and thinned to one plant per potat the one-leaf (V1) growth stage.
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