Biological nitrification inhibition activity in a soil-grown biparental population of the forage grass, Brachiaria humidicola
Utilization of biological nitrification inhibition (BNI) strategy can reduce nitrogen losses in agricultural systems. This study is aimed at characterizing BNI activity in a plant-soil system using a biparental hybrid population of Brachiaria humidicola (Bh), a forage grass with high BNI potential but of low nutritional quality.
Soil nitrification rates and BNI potential in root-tissue were analyzed in a hybrid population (117), obtained from two contrasting Bh parents, namely CIAT 26146 and CIAT 16888, with low and high BNI activity, respectively. Observed BNI activity was validated by measuring archaeal (AOA) and bacterial (AOB) nitrifier abundance in the rhizosphere soil of parents and contrasting hybrids. Comparisons of the BNI potential of four forage grasses were conducted to evaluate the feasibility of using nitrification rates to measure BNI activity under field and pot grown conditions.
High BNI activity was the phenotype most commonly observed in the hybrid population (72%). BNI activity showed a similar tendency for genotypes grown in pots and in the field. A reduction in AOA abundance was found for contrasting hybrids with low nitrification rates and high BNI potential.
Bh hybrids with high levels of BNI activity were identified. Our results demonstrate that the microcosm incubation and the in vitro bioassay may be used as complementary methods for effectively assessing BNI activity. The full expression of BNI potential of Bh genotypes grown in the soil (i.e. low nitrification rates) requires up to one year to develop, after planting.
KeywordsAmmonia oxidation Bioassay Brachiaria hybrids Microcosm incubation Plant soil interaction Rhizosphere
We very much appreciate the financial support of the project “Climate-smart crop-livestock systems for smallholders in the tropics: Integration of new forage hybrids to intensify agriculture and to mitigate climate change through regulation of nitrification in soil” by the Federal Ministry for Economic Cooperation and Development (BMZ, Germany). This study was undertaken as part of the LivestockPlus project funded by CGIAR Research Program (CRP) on Climate Change, Agriculture and Food Security (CCAFS), which is a strategic partnership of CGIAR and Future Earth. In addition, this work was, in part, conducted as part of the Livestock CRP. We thank all donors that globally support the work of the program through their contributions to the CGIAR system. We would like to thank Lucia Chavez, Maria Eugenia Recio, Aracelly Vidal and Edwin Palma for their technical assistance in performing this research. We thank the two anonymous reviewers for their valuable and constructive comments.
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