Can you reduce fertiliser requirement by increasing the diversity of plants in grassland?

IncreasIng biodiversity in farmland is a major challenge and opportunity for the farming industry, which can offer benefits in terms of reducing environmental impact and improving public perceptions of agriculture. Whilst biodiversity conservation is extremely important, this must be balanced against the needs of farm businesses and the requirements for food production to ensure food security. evidence exists for the potential of species-rich grasslands to deliver multiple benefits to the farmer, such as reduced input of expensive materials such as fertilisers, whilst simultaneously providing the foundation for a more biodiverse ecosystem.

experiments have shown that rates of productivity in grassland systems and plant species richness are positively related. When comparing sets of sown grassland plots with different amounts of species, yield has been demonstrated to be higher in species rich grasslands than in species poor, and that this effect remained consistent in the long term (eight years).

In one study comparing productivity in grassland managed either as high-diversity (of plants) with low-input (of fertiliser) or as high-input low-diversity, yield was observed to increase as a result of higher plant diversity, which served to offset any yield gains from fertiliser input, resulting in similar yields from either system.

This positive effect on yield as a consequence of the amount of different plant species, has been attributed to the influence of resource partitioning, both above and below ground, which is where different growth forms allow for better usage of resources such as light or nutrients.

This can allow plants to utilise resources that a neighbouring plant is unable to capture (i.e. by having roots at different soil depths, which utilise nutrients at different levels in the soil profile) reducing the impact of competition. This is referred to as ‘niche complementarity’, where there are positive interactions amongst species by virtue of having numerous different plant species from a wide range of life histories.

In addition, the architecture of more complex plant communities, again both above and below ground, can also allow for greater density of vegetation as a consequence of the different growth forms being able to live in more close proximity, meaning more physical biomass.

Thecaseforreducingtheneedforfertiliserusage,byincreasing grassland plant species richness, is intriguing. This approach could potentially improve farm business efficiency whilst increasing biodiversity.

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