Residual soil nitrate as affected by giant reed cultivationand cattle slurry fertilisation

摘要

The residual soil nitrate (RSN) is the amount of nitrate whichremains in soil profile after crop uptake has ceased, typically inthe autumn. The RSN is prone to leaching and therefore posesserious environmental concerns, especially in areas with intensivelivestock activities. Little is known about the ability of the energygrass giant reed in leaving low RSN. Such ability would add adesirable environmental benefit to giant reed cultivation. This articlereports on snapshot measurements of RSN across soil profilein the autumn of three consecutive years: 2010, 2011 and 2012.Soil nitrate content was measured on soil samples collected fromthe soil layers 0-0.2 m, 0.2-0.4 m, 0.4-0.6 m and 0.6-0.8 m. TheRSN of giant reed was compared with RSN of the energy cropssweet sorghum and poplar short rotation coppice (SRC). The threeenergy crops were treated with two fertilisation regimes: 0 kg Nha–1 (Control) and 20 mm of cattle slurry (CS20). Soil sampleswere also taken for a reference crop of winter wheat followingwinter wheat and receiving no N supply. Our findings for the threeyears of experiment can be summarised as follows: i) in case ofthe unfertilised Control, the three dedicated energy crops giantreed, sweet sorghum and poplar SRC left in soil profile in theautumn significantly lower amounts of RSN compared to the referencecrop of wheat. Hence, all the three energy crops providedin similar manner the environmental benefit of leaving lowerRSN; ii) in case of cattle slurry application the real advantage ofgiant reed cultivation became surprisingly evident. In fact, in threesubsequent years the treatment giant reed CS20 never determinedRSN significantly higher than RSN for giant reed Control. TheRSN for giant reed with treatment CS20 was significantly lowerthan that the reference crop of wheat in all the three years. Unlikepoplar SRC and sweet sorghum, giant reed exerted effective soilnitrate removal with a relatively high rate of cattle slurry application.Hence, this species can be regarded as suitable not only toutilise livestock effluents, but also to reduce the risk of nitrate pollutionin many land use situations dealing with nitrogen surplus.