SUMMARY The fate of both faecal Escherichia coli and E. coli O157 in slurry following application to arable and grass plots on a clay loam soil was studied. Slurry (5% dry matter) containing 53 × 104 ml−1 E. coli and 30 E. coli O157 100 ml−1 was spread in early March. Initially, almost all E. coli were retained in the upper layers of the soil. Escherichia coli numbers steadily declined to less than 1% of those applied by day 29, and E. coli O157 were only detected in the soil and on the grass for the first week after application. There was some transport of bacteria to deeper layers of the soil, but this was approximately 2% of the total; transport to drains over the same period was mainly associated with rainfall events and amounted to approximately 7% of applied E. coli. However, there were indications that periods of heavy rainfall could cause significant losses of E. coli by both leaching and run‐off. Experimental studies showed that E. coli O157 on grass, which was subsequently ensiled in conditions allowing aerobic spoilage, could multiply to numbers exceeding 106 g−1 in the silage.

The loss of P in subsurface drainage from lysimeters (0.5 ha), managed as either monoculture grass or grass‐clover for the last 9 yr have been quantified. Both systems received two to three cattle slurry applications annually and were cut two to three times before being grazed by dairy cattle. Mineral fertilizer‐P was applied only to the grass‐clover (about 25 kg P ha−1 yr−1). After 9 yr, NaHCO3‐soluble P in the topsoil (0–10 cm) averaged 38 and 47 mg P kg−1 for the grass and grass‐clover respectively, giving an average increase of 1.0 mg OIsen‐P kg−1 yr−1 in the grass‐clover. Drainage‐weighted molybdate‐reactive phosphorus (MRP) and total phosphorus (TP) concentrations ranged from 0.16 to 0.38 mg P L−1 and 0.45 to 0.79 mg P L−1, respectively during the 2‐yr study period. The MRP and TP losses in subsurface‐flow from the grass‐clover (1.68–2.03 and 3.47–5.03 kg P ha−1 yr−1, respectively) were significantly larger than those from the grass (1.27–1.34 and 2.97–3.58 kg P ha−1 yr−1, respectively). Averaged across years and pastures, MRP accounted for 42% of the TP loss, while a non‐MRP form accounted for 41% of the TP loss through field drains. Particulate‐associated P represented about 17% of the TP loss. The P losses in subsurface runoff measured in the present study were much larger than previous estimates. The results also showed that, despite the subsoil having much larger P‐sorption capacity than the topsoil, significant amounts of P losses could occur through preferential hydrological pathways.

Aims: Investigations were carried out to observe the influence of winter/spring and summer periods on the survival of Salmonella typhimurium and indicator bacteria (psychrophilic, mesophilic, coliform and faecal coliform bacteria and faecal streptococci) in the solid fraction of pig slurry from agricultural wastewater treatment plant. Methods and Results: Leather squares and PVC bottles with openings served as test carriers. They were inoculated with broth culture of Salm. typhimurium and introduced directly into the solid fraction. During the experiment, quantitative and qualitative examinations were carried out to determine the presence of Salm. typhimurium and observe the dynamics of indicator bacteria in the solid fraction. Conclusions: Salmonella typhimurium survived for 26 d in summer and for 85 d in winter/spring. The T90 values of indicator bacteria in summer ranged from 35·44 d (coliform bacteria) up to 100·29 d (mesophilic bacteria). The winter T90 values of indicator bacteria ranged from 74·58 d (faecal coliform bacteria) to 233·07 d (coliform bacteria). Significance and Impact of the Study: The present study demonstrated that it is necessary to pay increased attention to the manipulation of slurry solid fraction.

Abstract. Slurry from farm animals may contaminate water supplies, rivers and bathing waters with faecal coliforms, such as Escherichia coli. Where animals harbour the O157 strain the hazard to human health is particularly high, but both the hazard level, and the low incidence and sporadic nature of the excretion of E. coli O157 make it difficult to study this strain under field conditions. The survival of total E. coli and of E. coli O157 were compared in the laboratory for two soils under controlled temperature and moisture. E. coli O157 die‐off rate was the same as or quicker than for total E. coli. This result meant that field experiments studying the fate of total E. coli should give a satisfactory evaluation of the risk of water contamination by the O157 strain. In four field experiments at three sites, slurry containing total E. coli numbers of 2.2 × 104 to 5.7 × 105 colony forming units per mL (c.f.u. mL–1) was applied to drained field plots. Field die‐off was faster than expected from laboratory experiments, especially in one experiment where two weeks dry weather followed application. In all but this experiment, the first drain flow events after slurry application led to very high E. coli concentrations in the drains (103 to 104 c.f.u. mL–1). E. coli O157 was present in the slurry used for two of the experiments (33 c.f.u. per 100 mL in each case). However the proportion of E.coli O157 was very low (about 1 in 105) and it was not detected in the drainage water. After the first week E. coli drainage water numbers decreased rapidly but they were 1–10 c.f.u. mL–1 for much of the sampling period after slurry application (1–3 months).

Changes in the weed seedbank were monitored between 1991 and 1998 in two experiments that were established to compare organic crop rotations at two sites in NE Scotland. Two rotations, replicated twice at each site, were compared and all courses of both rotations were present every year. There were relatively minor changes in weed species diversity over time, but major changes in seedbank abundance. Weed seed numbers were relatively low in rotations with a high proportion of grass/clover ley. Differences in level of seedbank across the rotation were relatively predictable at Tulloch but much less so at Woodside where factors such as the effect of the grass/clover ley seemed to play a lesser role. Other factors, such as weather and its influence on the effectiveness of weed control operations, and higher populations of ground-living arthropods, may be affecting the Woodside seedbanks.