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| Home > Publications database > Mean nutrient uptake depths of cereal crops change with compost incorporation into subsoil – evidence from 87Sr/86Sr ratios and potential for Mg stable isotopes |
| Home > Publications database > Mean nutrient uptake depths of cereal crops change with compost incorporation into subsoil – evidence from 87Sr/86Sr ratios and potential for Mg stable isotopes |
| Conference Presentation (Other) | FZJ-2023-02131 |
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2023
Abstract: Root restricting layers often hinder crops from accessing the large reservoir of bioavailable mineral nutrients situated in the subsoil. This study aimed i) at exploring changes in the mean nutrient uptake depth of cereal crops by means of 87Sr/86Sr ratios when removing root restricting layers through subsoil management, and ii) at testing Mg stable isotopes as a new analytical proxy in plant/soil sciences to simultaneously identify changes in the mean nutrient uptake depth and to quantify the Mg use efficiency of crops defined here, as the ratio of Mg uptake versus Mg supply.Subsoil management was performed by deep loosening, cultivation of lucerne as deep-rooting pre-crop, and their combination with compost incorporation. Management effects were evaluated by means of shoot biomass and element concentrations in shoots and soil compartments. The mean nutrient uptake depth was fingerprinted by matching the 87Sr/86Sr ratios in shoots with the 87Sr/86Sr ratios in the exchangeable fraction in soil. The feasibility of Mg stable isotopes was demonstrated conceptually by simulating subsoil management on soils with low, middle, and high inventories of bioavailable Mg and crops typically cultivated in Germany, which was further validated in the field trials of this study.Shoot biomass remained constant in management and control plots. The mean nutrient uptake depth, inferred from 87Sr/86Sr ratios, changed with subsoil management in the order: deep loosening < control < deep loosening with compost incorporation. The latter coincided with a reallocation of compost-derived sodium and hence resulted in increased levels of bioavailable Na below the depth of compost incorporation. This increased level of bioavailable sodium at depth may have led to an improved water use efficiency of the crops, and thus triggered the deepening of the mean uptake depth of water and nutrients. Moreover, nutrient uplift from depth into topsoil was evident 21 months after subsoiling as suggested by both 87Sr/86Sr ratios and the Mg isotope composition of soil compartments.Subsoil management by deep loosening with compost incorporation provides a sustainable use of soil resources because otherwise unused deep geogenic-derived nutrient reservoirs can be additionally involved in crop nutrition. The application of Mg stable isotopes as a new geochemical routine for agronomy is promising but requires future work focussing on isotope fractionation factors related to crop uptake and intra-plant translocation of Mg, which may depend on species, environmental conditions, and nutrient status, to allow minimally invasive sampling of the soil-plant system and to reduce sample sets.
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