Abstract

This work is a part of a larger project together with Danisco Sugar AB, which tries to prevent compaction in the subsoil when using heavy sugar beet harvesters. The work is based on measuring the water con tent during a growing season (1997) and to calculate the water content with the simulation model SOIL. After that, the water con tent has been simulated from weather data for a longer period, and the risk for compaction in the autumn has been calculated. Agriculture has gone through a lot of changes since the second world war, for example the machines have become larger and heavier. The purpose of the project was to examine how often soil compaction in the subsoil should arise by measuring and calculating the water con tent. We have measured the water content every 14th day during the growing season 1997 on two sites: Elvireborg east of Landskrona and Kronoslätt dose to Hemmesdynge in the very south of Sweden. At Elvireborg sampling was made in sugar beets and spring wheat, and at Kronoslätt in sugar beets and spring barley. The soil at Elvireborg is a sandy day loam with a porosity of 38 % (vol/vol) with 18,4 % (vol/vol) water at permanent wilting point and 15,6 % plant available water. The soil has a good hydraulic conductivity in the topsoil (O - 30 cm), but much lower in the lower part of the subsoil (60-100 cm). During dry summers the hydraulic conductivity will improve by crack formation. Kronoslätt is a sandy loam with a porosity of 36,7 % with 12,6 % (vol/vol) water at permanent wilting point and 20,9 % plant available water. Kronoslätt has a strongly reduced hydraulic conductivity in the subsoil (30 - 100 cm) in comparison with the topsoil (O - 30 cm). An opened cylinder drill or an Ultuna drill was used to take out the soil samples to determine the water content at every 10th centimeter to one meter depth. Soil cores were sampled to one meter depth to determine saturated hydraulic conductivity and soil water retention. The water content was used to calibrate the simulation model (SOIL). Weather data for 1997 was collected from Jordberga sugar factory for Kronoslätt and from Svalöv weather station for Elvireborg. In the simulations the daily mean values were used for temperature, precipitation and sun radiation. Calculations have been done for changes in water content in 1997 and for the period 1963 - 1988 with 1997 as a calibration year. The precompression stress (Casagrande, 1936) was determined at four water tensions, and a logarithmic function was made between precompression stress and water tension. By combining this function with the soil water simulation, the susceptibility to compaction was estimated. The cereal crops took up less water than the sugar beets, and the sugar beets took up water during a longer period of the year, depending on a longer growing season. In the end of July practically all plant available water in the profile had been used in 1997. The measured water con tent was sometimes below permanent wilting point and lower than the simulated values. However, in general there was good correlation between measured and simulated values. Calculations were also made for the vertical soil stress in the soil, for a wheel load of 8 tons and 220 kPa ground contact pressure corresponding to a fully loaded sugar beet harvester. The soil was considered susceptible to compaction when the stress at a certain depth was higher than the precompression stress of the soil at that specific water content. Driving late in the autumn involves a big risk of compaction of the subsoil both at Elvireborg and Kronoslätt. From the middle of October there was a compaction risk in the subsoil at 50 cm depth for half of the years. In the results over the whole year, the Elvireborg site was more susceptible to subsoil compaction than Kronoslätt. This could be due to Kronoslätt being a more compact soil with a higher precompression stress

Keywords

jordbearbetning; alvpackning; betupptagare; sockerbetsskörd; vattenhalt; SOIL-modell; väderdata

Published in

Meddelanden från Jordbearbetningsavdelningen
1999, number: 28
Publisher: Institutionen för markvetenskap, Avdelningen för jordbearbetning, Sveriges lantbruksuniversitet

UKÄ Subject classification

Agricultural Science

Permanent link to this page (URI)

https://res.slu.se/id/publ/30024