Biological nitrification inhibition (BNI)—is it a widespread phenomenon?
- First Online:
- 995 Downloads
Regulating nitrification could be a key strategy in improving nitrogen (N) recovery and agronomic N-use efficiency in situations where the loss of N following nitrification is significant. A highly sensitive bioassay using recombinant luminescent Nitrosomonas europaea, has been developed that can detect and quantify the amount of nitrification inhibitors produced by plants (hereafter referred to as BNI activity). A number of species including tropical and temperate pastures, cereals and legumes were tested for BNI in their root exudate. There was a wide range in BNI capacity among the 18 species tested; specific BNI (AT units activity g−1 root dry wt) ranged from 0 (i.e. no detectable activity) to 18.3 AT units. Among the tested cereal and legume crops, sorghum [Sorghum bicolor (L.)], pearl millet [Pennisetum glaucum (L.) R. Br.], and groundnut [Arachis hypogaea (L.)] showed detectable BNI in root exudate. Among pasture grasses, Brachiaria humidicola (Rendle) Schweick, B. decumbens Stapf showed the highest BNI capacity. Several high- and low-BNI genotypes were identified within the B. humidicola species. Soil collected from field plots of 10 year-old high-BNI genotypes of B. humidicola, showed a near total suppression (>90%) of nitrification; most of the soil inorganic N remained in the NH4+ form after 30 days of incubation. In contrast, soils collected from low-BNI genotypes did not show any inhibitory effect; most of the soil inorganic N was converted to NO3– after 30 days of incubation. In both the high- and low-BNI genotypes, BNI was detected in root exudate only when plants were grown with NH4+, but not when grown with NO3– as the sole source of N. BNI compounds when added to the soil inhibited nitrification and the relationship was linear (r2 = 0.92**; n = 12). The BNI from high- and low-BNI types when added to N. europaea in pure culture, blocked both the ammonia monooxygenase (AMO) and the hydroxylamine oxidoreductase (HAO) pathways. Our results indicated that BNI capacity varies widely among and within species; and that some degree of BNI capacity is likely a widespread phenomenon in tropical pasture grasses. We suggest that the BNI capacity could either be managed and/or introduced into pastures/crops with an expression of this phenomenon, via genetic improvement approaches that combine high productivity along with some capacity to regulate soil nitrification process.
KeywordsBiological nitrification inhibition (BNI) Brachiaria BNI activity Inter-specific variation Intra-specific variation Mode of inhibition Nitrification Nitrosomonas europaea Root exudate
- Anon (1974) Technicon Autoanalyzer II, Technicon Industrial Systems. Tarrytown, NY, 10591Google Scholar
- Bock E, Koops HP, Harms H, Ahlers B (1991) The biochemistry of nitrifying organisms. In: Shively JM, Barton LL (eds) Variations in autotrophic life. Academic Press, San diego, CA, pp 171–200Google Scholar
- Hauck RD (1980) Mode of nitrification inhibitors. In: Nitrification inhibitors—potentials and limitations. ASA Special Publication No. 38, American Society of Agronomy, Madison, Wisconsin, pp19–32Google Scholar
- Lata JC, Guillaume K, Degrange V, Abbadie L, Lensi R (2000) Relationships between root density of the African grass Hyparrhenia diplandra and nitrification at the decimetric scale: an inhibition–stimulation balance hypothesis. Proc Royal Soc London Series B, Biological Sci 267:1–6CrossRefGoogle Scholar
- Prasad R, Power JF (1995) Nitrification inhibitors for agriculture, health, and the environment. Adv Agron 54:233–281Google Scholar
- Rao IM, Kerridge PC, Macedo M (1996) Adaptation to low fertility acid soils and nutritional requirements of Brachiaria. In: Miles JW, Maass BL, do valle CB (eds) The biology, agronomy and improvement of Brachiaria. CIAT, Cali, Colombia, pp 53–71Google Scholar
- Sahrawat KL, Keeney DR (1985) Perspectives for research on development of nitrification inhibitors. Commun Soil Sci Plant Anal 16:517–524 Google Scholar
- Subbarao GV, Ishikawa T, Ito O, Nakahara K, Wang HY, Berry WL (2006b) A bioluminescence assay to detect nitrification inhibitors released from plant roots—A case study with Brachiaria humidicola. Plant Soil. Online first http://www.springerlink.com/content/r435654g2r514044.
- Subbarao GV, Wang HY, Ito O, Nakahara K, Berry WL (2006c) NH4+ triggers the synthesis and release of BNI (biological nitrification inhibition) compounds in B. humidicola roots. Plant Soil (in press) Google Scholar
- Theron JJ (1963) The mineralization of nitrogen in soils under grass. S Afr J Agr Sci 6:155–164Google Scholar