Epsilon Archive for Student Projects

Abstract

Structural rationalizations and regionalization of the agricultural sector in Sweden has lead to unevenness in the
distribution of plant nutrients. Nutrients are lost from crop producing farms as harvest products are sold, while
farms with animal production often have manure in excess of their needs. In addition to this the retention of
water and nutrients in naturally occurring wetlands has decreased due to a reduction of wetlands in number and
size in the agricultural landscape. This increases nutrient levels in agricultural run-off and causes eutrophication
as well as nutrient losses from arable soils. One potential solution to both problems would be to store nutrientrich
surface water from agricultural areas and use it for irrigation of agricultural crops. This thesis is a study on
the water and nutrient flows between four irrigation ponds, the irrigated fields and the streams from which water
is pumped into storage. It was found that the amount of nitrogen (N) and phosphorus (P) that had been gathered
in the different ponds varied a lot between ponds, due to differences in nutrient levels in the streams and to
differences in when ponds were filled. A maximum of 98 kg of N and 0.4 kg of P were collected in one of the
ponds. Only small amounts of nutrients were brought back to the fields with irrigation, at the most 5 kg of N and
0.07 kg of P. It was concluded that the practice of irrigating agricultural crops with nutrient-rich surface water
did not contribute much to nutrient demand, but it decreased nutrient transport further downstream as effectively
as an average wetland.