Increased eutrophication
and nutrient imbalances in the
agricultural soil of
NE Catalonia, Spain
J. Penuelas*1, J. Sardans1,
J.M. Alcaniz2 and J.M. Poch3
1Plant Ecophysiology and Global Change
Unit CSIC-CEAB-CREAF, CREAF (Center for Ecological Research and Forestry
Applications). Autonomous University of Barcelona,
E-08193 Bellaterra,
Spain
2CREAF (Centre forEcological Research and
Forestry Applications), Autonomous University of Barcelona, E-08193 Bellaterra, Spain
3Oficial College
of Agricultural Engineers of Catalonia, Girona
Delegation, C/Santa Eugenia, 102-104, esc C, entl. 1a,
17006, Girona,
Spain
(Received: June 23, 2008; Revised
received: September
25, 2008; Accepted: October 11, 2008)
Abstract: The soil C, N, P and K content of
agricultural soil were measured over the last 4 decades in NE Catalonia (NE Spain). Plant-available P and K increased by ca 109
and 105% respectively and total N decreased by 30%. The increases in
plant-available P content are in accordance with the increasingly used pig
slurry being very rich in P, and with P tendency to be retained in soils, since
it is less mobile than N. The total soil N (Ntot) decrease occurred
in the first decade (by 41%). The uptake and withdrawal of mineral N by crops and
the leaching of mineral N into groundwater and rivers after torrential
rainfalls were the two likely major pathways of N-loss from the soil. After the
first decade, there has been no further decrease of Ntot as a result
of the increasing fertilization of these fields, including the increasing
applications of pig slurry. These results show an increasing P eutrophication in Mediterranean agricultural soils and will
have several consequences for the next decades with (i)
an increasing unbalance between N and P (and K) in soils that might affect crop
productivity, (ii) an increasing leaching of N as nitrate to continental
waters, both ground and surface waters, and (iii) a consequent need for the
establishment of another fertilization strategy based on lowering the use of
pig slurry and on increasing the use of fertilizers of slow mineralization that
increase soil organic matter, and stabilise the soil
N and P contents.
Key
words: Fertilization, Girona, K, Nitrogen, P, Pig slurry, Soil
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