The relationship between plant diversity and two opposing nitrogen flows in an experimental pasture in a humid cool-temperate climate

Abstract

The nitrogen-conserving function of three sward types was tested in a plot experiment in Truro, Nova Scotia, Canada. Fertilized treatments showed a pronounced seasonal increase in NO₃-N in the soil solution from spring to mid-summer across sward types. The seasonal increase of nitrate leaching was most pronounced for the timothy sward ( Phleum pratense ) compared to the binary mixture of timothy and blue grass ( Poa pratensis ). The addition of meadow fescue ( Festuca pratensis ) and reed canary ( Phalaris arundinacea ) did not further reduce the leaching of nitrate. A seasonal increase in the relative dominance of white clover was most marked in timothy plots. High clover content and application of mineral N each appeared to exceed plant uptake and substantially increase nitrate leaching. Monitoring nitrate leaching using suction lysimeters proved useful in the assessment of the ecological performance of agroecosystems and to elucidate the relationship between plant diversity and ecosystem function.