Sorption of radiolabelled glyphosate on biochar aged in contrasting soils.

Glyphosate mobility from terrestrial to aquatic environments has raised concerns about it. Utilizing soil's inherent properties along with sorption properties of aged biochar, we hypothesized that selective application of biochar would be more effective in economic terms for glyphosate sorption on contrasting soils. To test this hypothesis, batch experiments and liquid scintillation counting for 14 C labeled glyphosate were used. The sorption behavior of glyphosate was examined in four contrasting Australian soil types (Oxisol, Vertisol, Entisol, and Inceptisol) amended with aged biochar to determine glyphosate concentrations by measuring 14 C activity using liquid scintillation counting. Freundlich parameters were calculated for soil-soil/biochar combinations. The pattern of glyphosate sorption was Oxisol > Vertisol > Entisol > Inceptisol. Oxisol adsorbed approximately five times more glyphosate compared with Inceptisol. Oxisol soil system adsorbed maximum amount of glyphosate principally due to the presence of iron-aluminum oxides exhibiting variable charges which got increased due to the presence of aged biochar. Considering all the soil/soil-biochar systems, Inceptisol soil system showed the least adsorption of glyphosate. A significant contribution of char was observed only in the Entisol soil system and the finding is valuable as char can be applied in Entisol soil systems to control glyphosate mobility.

The genetic control of tolerance to aluminum toxicity in the 'Essex' by 'Forrest' recombinant inbred line population.

Aluminum (Al) toxicity to plant roots is a major problem of acidic soils. The main chemical reaction involved is Al hydrolysis. Application of lime or nitrate fertilizers to raise soil pH reduces Al toxicity but not as economically as a plant genotypes with natural tolerance against this stress. Ammonium fertilization of crops and assimilation of ammonium (even that derived from dinitrogen) are particularly acidifying of the root zone. The aims of the present study were to find genotypes of soybean tolerant to aluminum stress and identify QTL underlying that trait. Used were recombinant inbred lines (RILs) derived from the cross of 'Essex' by 'Forrest'. RILs were grown in a greenhouse for 3 weeks and then transferred to hydroponics in a growth chamber. Root lengths (RL) were measured before and 72 h after Al treatment. RL before and after Al treatment were measured and used to calculate root tolerance index (RTI) and relative mean growth (RMG). RILs 1, 85, 40 and 83 had significant (P<0.005) tolerance to Al stress judged by RL after Al, RTI and RMG. Eleven minor but significant marker-trait associations (P<0.05) were detected using one-way ANOVA but only two major loci were significant in composite interval maps (LOD>3.0). The QTL on linkage group F (chromosome 13) was in the interval Satt160-Satt252 with a peak at 24 cM (peak LOD was 3.3). The QTL underlay 31% of trait variation and the Essex allele provided an additional 1.61 cm of root growth over 72 h in the presence of Al. The QTL on linkage group C2 (probably chromosome 4) was in the interval from Satt202 to Satt371 with a peak at 3.2 cM (peak LOD was 14.7). The QTL underlay 34% of trait variation or 1.81 cm of growth over 72 h in the presence of Al. Both loci encompassed genes implicated in citrate metabolism, a method of aluminum detoxification known to vary among soybean cultivars. Two major loci and at least nine minor loci were inferred to underlie tolerance to Al. RILs and markers may be used to select alleles that increase tolerance to soybean against Al stress.