Reduced tillage was compared with traditional ploughing in terms of erosion and phosphorus (P) and nitrogen (N) losses in an experimental field in southern Finland. One part of the field has been ploughed (treatment PF) and the other part harrowed (treatment NPF) every autumn since 1986. Flow volume and water quality data was collected separately from surface runoff and subsurface drainage waters during 1991-1995 (surface runoff volume since 1993). Erosion was higher in PF (on average 234 kg ha-1yr-1 in drainage flow and 479 kg ha-1 yr-1 in surface runoff) than in NPF (158 kg ha-1yr-1 in drainage flow and 160 kg ha-1yr-1 in surface runoff). Total N loss in drainage flow was also higher in PF (7.2 kg ha-1yr-1) than in NPF (4.6 kg ha-1yr-1). Total P losses did not differ much

The present study was carried out in summer 1970, when a rainy July following upon a dry June caused abundant detrimental late tillering among spring cereals in large parts of South Finland, and in part also in Central and North Finland. In four irrigation experiments, established in the clay area of South Finland, the irrigation performed in the middle of June (2 x 30 mm) increased the yield of two rowed barley by 1750 kg/ha on an average or by 71 % (variation range 49—104 %). In addition irrigation improved the quality of barley significantly by preventing detrimental late tillering. The irrigated evenly ripened barley was at harvesting time on an average 12.3 per cent units drier, with a hectolitre weight that was 3,6 kg higher when compared to the non-irrigated green grained barley. Analyses of the sheaves collected from the fields indicated that irrigated barley when compared to non-irrigated barley contained: a) equally many individuals per square meter, b) 14% less ears per individual, c) 83 % more grains per ear, d) 9 % heavier grains; in fact the total result was a 70 % higher grain yield. Causes of late tillering and the significance of irrigation in preventing this detrimental phenomenon are discussed. It is further established that in years when no late tillering occurs, irrigation affects the grain yield components in ways that differ from those established in the present study.

The aim of this study was to elucidate the effects of freezing on some structural properties of clay soils. The laboratory analyses were based on field observations including measurements of soil temperature and frost depth. The daily temperatures showed remarkable variations on the very soil surface both in the autumn and spring, ranging from below zero at night-time to above 10°C at daytime. The depth of soil frost was deepest in the ploughed field, whilst the straw cowers on the soil surface not only strongly reduced its depth, but also slowed up the thawing. Eight clay soil samples were analyzed in the laboratory. At the potentials of —0.001 to —0.1 bar the water retention capability of soil was reduced by freezing. Disruption of the 5 —10 mm aggregates by freezing, analyzed with wet and dry sievings and waterdrop analysis was strongly dependent on the water potential, the Water potential of 1.0 bar or lower having in general no effect. The total pore volume of aggregates Was dependent on the water potential when it exceeded —15.0 bar. Freezing had a minor effect on the pore volume of the aggregates, if they were let to thaw before drying. The freeze-dried aggregates showed a clear increase of pore volume when the water potential at freezing exceeded —1.0 bar. The movement of water due to ice formation was studied with small and big soil cylinders. It showed a great effect on the structure, if total pore volume, determined with a mercury method, is considered the standard of judgement. Thus it was concluded that the water movement even at a short freezing period is one of the most essential factors determining the structural formation of ploughed clay soil.