ISHS Acta Horticulturae 627: XXVI International Horticultural Congress: Toward Ecologically Sound Fertilization Strategies for Field Vegetable Production
USE OF SUCTION CUP LYSIMETERS IN FIELD EXPERIMENTS WITH ORGANIC FERTILISERS |
| Author: | U. Gertsson |
| Keywords: | mineralisation, nitrogen, Nmin, phosphorous |
| Abstract:
It is important to be able to follow the soil content of plant available nutrients during field experiments with vegetables. Soil samples are generally used for this purpose. The frequently used extraction methods for easily plant available nutrients are not adapted to micronutrients. When organic fertilisers are used, there is also a risk of fertiliser material contaminating the soil samples. An alternative approach is to collect soil water instead of soil samples. The aim of this paper was to compare the values of mineralised nitrogen analysed in soil water samples collected by suction cup lysimeters with corresponding analyses of soil column samples. The crop at the experimental field, direct sown onions, was organically grown. The preceding crop was either barley or barley with clover-grass. The suction cup lysimeters used were made of porous PTFE (teflon) mixed with silica flour. Their length was 95 mm and their diameter 21 mm. The lysimeters were installed with the lowest point at 25 cm deep, forming a 45 degree angle with the soil surface. They were surrounded by a silica slurry to get good contact with the soil. Soil and soil water samples were taken every second week. On the sampling occasions, the field was irrigated on the first day and on the following day the lysimeters were put under vacuum (0.7 bar) and the soil water was collected in bottles above ground. The results clearly show that it is necessary to use multiple samples to estimate the soil water content in one treatment. When the mean values from four lysimeters were used for each point, there was reasonably good correlation between the Nmin values in soil samples and in soil water samples (r2 = 0.75-0.81). Furthermore, it was shown that soil water samples could be used to estimate the plant available P. This seems also to be the case for other plant nutrients. | |
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