Laura Alakukku

Continuous redox potential measurements in zero tilled and ploughed clay soils

Zero tillage with a crop covered soil surface change topsoil structure affecting soil physical conditions. In the present study, tTwo long-term tillage field experiments were utilized to investigate the effects of tillage intensity on soil properties. Our aim was to investigate the effects of tillage intensity change on the living conditions of soil microbes. Four identical measurement stations to determine soil conditions all year round were prepared on ploughed and zero tilled plots. In the present paper, the results of continuous soil redox potential and temperature determinations in the layer of 10–15 cm during one year (June 2009 to May 2010) are introduced. The variation of redox potential results was high as was expected. When the data of one year was examined, clear positive linear dependence between soil redox potential and temperature was observed. Based on the mean values of one year experimental period, no marked differences in topsoil redox potential between autumn ploughed and zero tilled soil were observed. Both during the growing season and outside the growing season after heavy showers, there were periods during which topsoil redox potential decreased rapidly and the change was longer than usually in connection with rapid changes. During these periods, there were differences in soil redox potential between tillage treatments caused probably by the differences in soil structure, temperature and moisture conditions, and the interaction between soil conditions and crop development stage.

Spatio-Temporal Testing Of New Crop Growth Model

The crop growth is highly dependent on growth conditions which are varying from year to year and cannot be known in the very beginning of the growing season. In order to optimize the fertilizer dose according to the growth circumstances it is it is necessary to provide the nutrients for the growth of the crop in separate events. To make this kind of fertilizer adjustment feasible it is necessary to have information on the recent crop growth and a crop growth model which can be used to estimate the amount of nutrients for optimal growth.

Surface Runoff and Soil Physical Properties as Affected by Subsurface Drainage Improvement of a Heavy Clay Soil

The percent of total runoff as surface runoff is an indicator of soil structure and functioning of subsurface drainage system in clay soils. Water logging due to low infiltration and low hydraulic conductivity of wet soil increases the risk of surface runoff, and thereby the risk of soil erosion and phosphorus leaching. Lowering groundwater table by efficient subsurface drainage has been found to enhance physical and biological processes that improve the structure of clayey soils. The effects of drainage improvement on surface runoff and soil physical properties have seldom been reported. We have studied the long-term effects of subsurface drainage improvement on soil physical properties and surface runoff on a heavy clay soil under boreal conditions. The runoff determinations were carried out for five years before and nine years after the drainage improvement. During the study period, the soil was autumn ploughed annually to 20 cm depth and spring cereals were grown. Before the drainage improvement, surface runoff constituted 60–80% of the total runoff but it declined to 10–40% after improvement. Mean values of macroporosity and saturated hydraulic conductivity for subsoil (20–60 cm layer) measured ten years after drainage improvement were higher than the mean values measured two years before drainage improvement, indicating that the processes relevant to the formation of clay soil structure were enhanced.

Nutrient Load from Two Drainage Systems on Clay Soil

In the southern and the south-western parts of Finland 75% of the arable land has subsurface drainage. The Finnish state subsidizes subsurface drainage on certain conditions including for example different envelope materials, drain depth and total drain length per hectare. The typical drain depth is 1.0-1.2 m and the drain spacing varies mostly between 12 and 26 meters depending on the soil type. Gravel is the most common envelope, but also synthetic and semisynthetic textile, cocos fibre and wood chips are used. The aim of this study is to find out how two different kind of drainage methods affect crop production and nutrient load in both drainage waters and surface runoff. In the method I gravel is used as an envelope and the drain spacing is 8 m. In the method II very thin textile (<1 mm) is used as an envelope and drain spacing is 6 m. The research is carried out on a field at Jokioinen in south-western Finland. The soil is heavy clay and the mean slope is 1%. The existing tile drainage pipes were laid in 1954 using 16 m spacing and an average depth of 1 m. The size of the field is 6 ha and it consists of 3 field sections each with a separate drainage system. In the summer of 2008, the additional drainage systems were built into two of the field sections using the methods I and II . The third one was left as a control plot. Runoff volume and water quality of subsurface and surface waters and crop yield from each field section have been measured. Concentrations of total phosphorus, dissolved orthophosphate, total nitrogen, ammonium nitrate, nitrate nitrogen and solid substances have been determined from the samples. In the paper runoff, nutrient load and crop yield from the calibration and testing periods are presented. The feasibility of the two drainage methods is evaluated from the point of view of crop production and nutrient loading to surface waters.