PDMA enhancement of peanut Fe nutrition in calcareous soil
To investigate the effect of PDMA on peanut plants, we applied a PDMA or PDMA–Fe solution into the peanut rhizosphere in a pot assay. Application of PDMA or PDMA–Fe significantly enhanced plant growth and the SPAD value in young peanut leaves (Fig. 1). At 90 dps, the PDMA and PDMA–Fe treatments resulted in a higher dry-mass weight of the shoot; it was increased by 51.9% and 44.0% compared with the control, respectively. These two treatments produced slightly higher results than did the EDTA–Fe treatment, although the differences were not significant (Fig. 1b).
The application of PDMA or PDMA–Fe had no effect on the SPAD value of young leaves compared with the control at 40 dps (flowering stage) (Fig. 1c). At 55 dps (early pod-bearing stage), increases in the SPAD value of young leaves of 20.4% and 22.6% under PDMA and EDTA–Fe application compared with the control, respectively, were observed. Moreover, at 72 dps (late pod-bearing stage), the SPAD values of young leaves were increased greatly by 51.6%, 52.8%, and 60.5% compared with the control following PDMA, PDMA–Fe, and EDTA–Fe application, respectively. Positive effects on the SPAD value of young leaves were also observed at 90 dps (fruit-ripening stage) following the PDMA, PDMA–Fe, and EDTA–Fe treatments, which showed enhancements of 42.7%, 40.8%, and 59.2%, respectively. In terms of peanut growth, PDMA and PDMA–Fe diminished chlorosis of the leaves and promoted plant growth. These positive effects were similar to those of traditional Fe fertilizers.