Abstract

An experimental field was established during 1982-83 on a sandy soil at Mellby in the south-western part of Sweden. The field was divided into ten separate tile-drained plots, each with an area of 0.16 hectare. An investigation was carried out during a five year period wight the objective to elucidate the effects of different nitrogen fertilizer regimes on leaching losses of nitrogen from the root zone. The amount of drainage water from each plot was measured and water samples collected twice monthly for analysis of pH, electrical conductivity, nitrogen, phosphorus and ptassium. The losses of nitrogen by water percolating to the groundwater were estimated with a simulation model. The fertilizer regimes were: unfertilized, commercial N-fertilizer according to general recommendations (90-110 N kg/ha), liquid manure in spring (110 total-N kg/ha) with and without winter rye as a catch crop sown after the main crop, liquid maure in the early autumn; (55, 110 and 220 total-N kg/ha) and lage autumn (110 total-N kg/ha). All the manure treatments recived a complementary addition of commersial N-fertilizer in the spring according to 50 % of the general recommendations. The nitrogen losses from the unfertilized treatment were slightly reduced compared with the spring fertilized treatments. The amount of mineral nitrogen in the soil as well as the leaching losses were of the same order of magnitude from the treatment with commersial fertilizer and the treatment with spring application of liquid manure without catch crop. The catch crop reduced the amount of mineral nitrogen in the soil during the late autumn and winter and thereby reduced the leaching losses by almost half, providning the catch crop was well established in the autumn. Spreading of liquid manure in autumn resulted in high enrichment of leachable nitrate nitrogen in the soil during winter time. As a consequence, the leaching losses were always higher compared to spring application. There were only small and variable differences in leaching losses between the treatments with liquid manure application in early and late autumn. Increasing doses of liquid manure strongly increased leaching losses of nitrogen from the soil profile. The harvest from the unfertilized treatment was reduced to almost half of the spring fertilized treatments. The harvest from the treatments with commercial fertilizer and spring application of liquid manure, with and without cath crop, were of the same order of magnitude. Harvest from treatment with autumn application of liquid manure were reduced as a result of the nitrogen losses. Only in the treatment with the largest dose of liquid manure, was the harvest of approximatley the same order of magnitude as in spring fertilized treatments. Kväveutlakningen från åkermark är en av flera bidragande orsaker till de rapporterade algblomningarna och därav följande döda havsbottnar, som under längre eller kortare perioder förekommer längs kusterna (DSH 1989:2). Speciellt har situationen i Laholmsbukten blivit uppmärksammad (Rosenberg et al., 1990). Jordbruket i södra Halland kännetecknas av intensiv växtodling med stor andel vårsådda grödor. De lätta jordarna och den höga nederbörden med åtföljande hög avrinning medför att lättrörliga växtnäringsämnen löper stor risk att utlakas till yt- och grundvatten (Bring och Gustavsson, 1984; Fleischer et al., 1989). Den omfattande djurhållningen har många gånger medfört att mycket nötkreatursgödsel spridits på en förhållandevis liten area (Joelsson Pettersson, 1982). En del av gödseln har av utrymmes- och arbetstekniska skäl spridits under hösten och vintern. Vid denna tidpunkt har det oftast inte funnits någon växande gröda som kunnat tillgodogöra sig den del av kvävet i kreaturgödsel som är lätttillgänglig för växtupptag och utlakning.

Keywords

kväveutlakning; gödsel; växtnäringsläckage; växtnäringsutlakning

Published in

Ekohydrologi
1992,
ISBN: SLU-VV-EKOHYD--28--SE
Publisher: Avdelningen för vattenvårdslära, Sveriges lantbruksuniversitet

Permanent link to this page (URI)

https://res.slu.se/id/publ/125728