In general, the minimum N rates (organic and/or mineral)
to achieve maximum grain and biomass yields coincided with
the minimum N losses and the minimum soil residual NO3-N contents, suggesting that the optimal N rate was also the most
environmentally friendly.
Recommendations for fertilisation should not be based on
fixed rates of N applications. Testing soil initial NO3
−-N levels
before basal N (organic or mineral) fertilisation could help to
produce more accurate N fertiliser recommendations.
In our study, maize fertilised with PS at a rate of 60m3 ha−1
without the addition of any other kind of mineral N sidedress
fertilisation, produced the maximum grain yields (from 12 to
16Mgha−1) suggesting that it is possible obtain optimal grain
yields just fertilising with PS. However, fertilising with 60m3 of
PS ha−1 in vulnerable areaswould contravene existingEUdirectives
on nitrate pollution (European Union, 1991; Diari Oficial
de la Generalitat de Catalunya, 1998, 2004). It was also possible
to obtain maximum yields and yet comply with EU directives by
applying only 30m3 ha−1 of PS complemented with the application
of 100 kgNha−1of mineral fertiliser at sidedress. Fertilising
maize with PS could increase crop profitability because PS is
cheap and abundant. Moreover, applying PS as a fertiliser could
help to solve the problem of PS disposal.
Satisfactory grain yields could be obtained by fertilising with
only PS. However, due to the great variability in the composition
of PS and the difficulty of achieving a homogeneous application,
achieving specific target rates forNapplication could prove
complicated. These problems could probably be partially solved
by analysing PS before its application and utilising precision
machinery such as the liquid manure injection system.
In general, the minimum N rates (organic and/or mineral)to achieve maximum grain and biomass yields coincided withthe minimum N losses and the minimum soil residual NO3-N contents, suggesting that the optimal N rate was also the mostenvironmentally friendly.Recommendations for fertilisation should not be based onfixed rates of N applications. Testing soil initial NO3−-N levelsbefore basal N (organic or mineral) fertilisation could help toproduce more accurate N fertiliser recommendations.In our study, maize fertilised with PS at a rate of 60m3 ha−1without the addition of any other kind of mineral N sidedressfertilisation, produced the maximum grain yields (from 12 to16Mgha−1) suggesting that it is possible obtain optimal grainyields just fertilising with PS. However, fertilising with 60m3 ofPS ha−1 in vulnerable areaswould contravene existingEUdirectiveson nitrate pollution (European Union, 1991; Diari Oficialde la Generalitat de Catalunya, 1998, 2004). It was also possibleto obtain maximum yields and yet comply with EU directives byapplying only 30m3 ha−1 of PS complemented with the applicationof 100 kgNha−1of mineral fertiliser at sidedress. Fertilisingmaize with PS could increase crop profitability because PS ischeap and abundant. Moreover, applying PS as a fertiliser couldhelp to solve the problem of PS disposal.Satisfactory grain yields could be obtained by fertilising withonly PS. However, due to the great variability in the compositionof PS and the difficulty of achieving a homogeneous application,achieving specific target rates forNapplication could provecomplicated. These problems could probably be partially solvedby analysing PS before its application and utilising precisionmachinery such as the liquid manure injection system.
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