Biological nitrification inhibition by Brachiaria grasses mitigates soil nitrous oxide emissions from bovine urine patches. (April 2017)

• Record Type: Journal Article
• Authors: Byrnes, Ryan C.; Nùñez, Jonathan; Arenas, Laura; Rao, Idupulapati; Trujillo, Catalina; Alvarez, Carolina; Arango, Jacobo; Rasche, Frank; Chirinda, Ngonidzashe
• Is Part Of: Soil biology and biochemistry. Volume 107(2017)
• Page Start: 156
• Page End: 163
• Publication Date: 2017-04
• Subjects: Biological nitrification inhibition -- Bovine urine patches -- Brachiaria humidicola -- Ammonia oxidizing bacteria and archaea -- N2O emission factor; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2016.12.029
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: High nitrogen (N) concentration in bovine urine, which generally exceeds plant N uptake rates, results in the formation of hotspots of N loss when bovine urine is deposited on grazed pasture soils. High spatial variability in the distribution of urine patches in grazed pastures poses a major challenge to mitigate N losses. Some exudates from the roots of several tropical forage grasses were shown to inhibit the activity of soil nitrifiers; a process known as biological nitrification inhibition (BNI). We hypothesized that nitrate (NO3 − ) production and nitrous oxide (N2 O) emissions from urine patches deposited on soils under forage grasses with high BNI capacity are lower than those with forage grasses with low BNI capacity. This hypothesis was tested using field plots of two tropical forage grass cultivars, Brachiaria humidicola cv. Tully (BT) and interspecific Brachiaria hybrid cv. Mulato (BM) which, correspondingly, have high and low BNI capacity. Nitrification rates and amo A gene copy numbers of ammonia oxidizing archaea (AOA) and bacteria (AOB) in soils under the two forage grasses were quantified before and after urine and water (control) application, as well, an additional experiment was conducted to quantify denitrification potential. Moreover, soil N2 O emissions from simulated urine (0.123 kg N m −2 ) and water patches were monitored over a 29-day period. Results showed a greater suppression of nitrification, denitrification and AOA abundance in soils under BT than those under BM. Positive relationships (p < 0.05) existed between AOA and AOB abundance and NO3 − contents in soils under BM. Bovine urine resulted in higher cumulative N2 O fluxes from soils under BM (80 mg N2 O-N m −2 ) compared to those under BT (32 mg N2 O-N m −2 ). Consequently, N2 O emission factors were higher for soils under BM (0.07%) than under BT (0.00002%). We conclude that tropical forage grasses with high BNI capacity play a key role in mitigating N2 O emissions from bovine urine patches in archaea-dominated soils. This suggests that wide-spread adoption of tropical forage grasses with high BNI capacity may have a great potential to tighten N cycling in grazed pastures. Highlights: Biological nitrification inhibition-BNI suppresses N2 O emission from urine patches. BNI: Brachiaria humidicola cv. Tully (BT) > Brachiaria hybrid cv. Mulato (BM). Soil N2 O emission was lower from urine patches in soils under BT than BM. Ammonia oxidizing archaeal nitrifiers were particularly suppressed under BT. High BNI of tropical forage grasses tightens N cycling in archaea-dominated soils.