Brachiaria species are the most widely planted tropical forage grasses in the world. The socio-economic impacts of new hybrids of Brachiaria that can suppress nitrification would be immense in terms of increased feed resources in the tropics, more efficient use of purchased inputs, more efficient use of land resources, increased integration of crops and livestock in agricultural systems, and mitigation of climate change through reduced atmospheric buildup of GHGs.
The effects could be strongly felt throughout Latin America where Brachiaria pastures are the main feed resource to livestock production. Significant spillover to Southeast Asia and Sub-Saharan Africa can also be expected, as these regions are dominated by low fertility soils where crop-livestock systems including Brachiaria have a niche.
Exploiting the BNI phenomenon through integration of crop-livestock systems could become a powerful strategy towards the development of low--nitrifying agronomic systems, benefiting both agriculture and the environment and improving the eco-efficiency of agricultural systems. We envision intensive production systems where both annual crops and grazed pastures occupy the same land area –in temporal rotation– to the mutual benefit of both activities.
Pastures will benefit from the residual effect of fertilizer applied to a preceding crop. Annual crop production will benefit from the conservation of N owing to BNI as well as the more general benefits of well managed grazed pastures on nutrient cycling, build-up of soil organic matter, and improvement in soil structure from deep-rooting pasture grasses. The improved B. humidicola hy-brids can readily be propagated vegetatively. One example of this is from the Colombian Llanos where many thousands of hectares of B. humidicola pastures were established, in the absence of commercial seed and even prior to formal release and institutional promotion. By integrating B. humidicola hybrids with BNI function into smallholder crop-livestock systems, farmers could benefit
Strategic management for forage production and mitigation of environmental effects: Development of Brachiaria grasses to inhibit nitrification in soil 96
economically from reduced losses of N fertilizer from their farms. And socie-ty at large will benefit from a decrease in both groundwater and atmospheric pollution caused by agricultural N losses. A major challenge is to explore with stakeholders (a wide range of public and private sector partners) the options for dissemination of novel Brachiaria hybrids to contribute to eco-efficient agriculture in the tropics.
Acknowledgements: We are grateful to the partial funding support from the CGIAR Research Programs (CRPs) of Livestock & Fish, Climate Change and Humid Tropics; BMZ-GIZ, Germany; MAFF, Japan; and Sida, Sweden.
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Figure 1. Schematic representation where biological nitrifi cation inhibition (BNI) interfaces with the nitrogen cycle. BNI’s produced by the root inhibits the process that converts ammonium to nitrate (Modifi ed from Philippot and Hallin, 2011).
0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000
B. humidicola Cropped area Native savanna
Grain yield (kg/ha)
Land use
60 N 120 N 240 N
39.68 26.21
15.33
10.27 17.70
15.38
24.06
17.38 9.73
Figure 2. Grain yield (kg/ha) from maize plots fertilized with 60, 120, and 240 kg N/ha where a long term (15 years-old) Brachiaria humidicola pasture, cropped area (maize rotated with soybean), and native savanna were previous land use systems. Agronomic nitrogen use efficiency (kg of grain yield/kg of N applied) values are shown above the S.E.
bars. Values are means ± SE from three replications (Adapted from Moreta et al., 2014).
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