Abstract

Phosphorous losses with surface runoff are affected by how the soil is cultivated. In a plot study, located in central Sweden, eight different treatments were; conventional autumn plowing, spring plowing with and without catch crop, no tillage, deep cultivation (40 cm), direct drilling, ley alternating with autumn wheat, and addition of organic material. The two spring-plowed treatments had the lowest losses of total phosphorous; the catch crop did not develop sufficiently to affect the losses. The largest losses were from the autumn-plowed and the deep-cultivated plots, beeing almost twice those of the spring-plowed plots. The loss of phosphate-phosphorous were largest from the direct-drilled plot, where it contributed with half of the loss, compared to 10-20% in the other treatments. The treatments that gave the best ratio between phosphorous loss and harvest were the two spring-plowed plots and the one with addition of organic matter. --- As a part of nation-wide monitoring of the impact of agriculture on the aquatic system, total and dissolved phosphorus (P) transport was measured from eleven subsurface drained fields in Sweden between 1977-1998. The P leaching revealed marked spatial variation depending on soil type, P soil status and other factors. Notably leaching from three of the fields together accounted for another 19 %, while leaching from the other four fields was more or less negligible. During the investigation period a surplus of P added to the soil during the initial years was transformed to a slight underbalance of P. Leaching from most fields was found to be relatively constant, but two fields with highest P losses showed increasing trend during the 1970 and 1980. On average 0,4 kg/ha and year leached from all fields during the entire period. This figure may have been an underestimation, especially on clay soils, depending on the sampling technique. -- A database was set up covering analysis of pesticides in surface water and groundwater during the period January 1985 to June 1999. The data were obtained from more than 4000 water samples collected primarly by Swedish municipalities. Many of these samples were taken because either problems were expected, or pesticides had been detected earlier at the particular site. Pesticides were found in drinking water from 15 municipalities. The most frequently occurring pesticide found in drinking water was a metabolite from the herbicide dichlobenil; i.e. 2,6-dichlorobenzamide (abbreviated BAM). The greatest number of water localities containing pesticides was found in Skåne, the county with the highest number of investigations but also the county with the most intensive use of pesticides. The substances most often detected in surface water, apart from BAM were MCPA, atrazine, dichlorprop and mecoprop, and the median concentrations of detection were in the range 0.1-0.3 µg/l. An analytical method to detect glyphosate in water was developed in 1997, whereafter glyphosate was detected quite frequently in surface water samples. An additional 13 substances were recovered fairly frequently, and another 42 pesticides were occasionaly detected. There were indications that the concentrations of pesticides in surface water decreased during the period, though this could not be statistically demonstrated.

Keywords

bekämpningsmedel; fosfor; växtnäringsläckage; ytvatten; grundvatten; avrinning; utlakning

Published in

Ekohydrologi
2000,
Publisher: Avdelningen för vattenvårdslära, Sveriges lantbruksuniversitet

Permanent link to this page (URI)

https://res.slu.se/id/publ/125852