Abstract
BASF's lysimeter facility at Limburgerhof was 50 years old in 1977. Approximately 130,000 percolate samples from 232 outdoor plots have been removed and measured there to date. About 1.5 million analyses of substances in soil and percolate have been carried out, as have about 190,000 analyses of substances in crops. Thirty-nine publications on the subjects of fertilization and crop protection provide evidence of the comprehensive work in agricultural chemistry, as well as in crop and environmental protection. These publications discuss nutrient supply and nutrient behavior in the soil and their relation to the most varied growing conditions. The speed with which the substances migrate in the soil and their degradation are of special importance when studying the active ingredients of crop protection. The numerous results at Limburgerhof allow the following conclusions to be drawn. 1. The most accurate methodical aid for establishing nutrient balances for the plant-soil system remains the lysimeter trial, although great care must be taken in interpreting the results for practical conditions. 2. The percolate is of decisive importance as a means for transporting the substances moving into the soil. The formation of percolate is influenced considerbly by weather, soil type, vegetative cover, and rooting intensity. More percolate is released into deeper levels when the soil is light, the crop cover thin, and porecipitation plentiful (especially if poorly distributed) than when the soil is heavy with vigorously growing vegetation. Crop type and cropping method (intercropping) have an influence on these relationships. 3. Of the primary nutrients, nitrogen is most easily displaced in the soil. What the plants do not take up is leached into the soil or released by denitrification. The nitrogen removed with the percolate is almost completely in the form of nitrate. Most of this comes from the nitrogen reserves in the soil; only 5 to 7 percent comes from fertilizer. The nitrogen balances of the soils were negative; exceptions occurred only under extreme circumstances. High, unfavorably distributed precipitation increased the migration of nitrogen, especially in light soils; dense plant covers (intercropping) decreased it. The combined effect of nitrogen fertilization and irrigation helped to counteract leaching losses. 4. Phsosphorus is the least mobile primary nutrient in the soil; most of it removed by the crop stands. The relatively small amount that is leached is largely independent of the crop type and the amount and form of phosphate fertilizer. It does vary, however, with the type of soil and the amount of water supplied. Therefore, increasing phosphate dressing frequently brings about a positive P balance in the soil. 5. Potassium is more mobile in the soil than phsophorus, but it is less mobile than nitrate nitrogen. The quantities of potash removed by the plants and the percolate were relatively high in Limburgerhof, but they came from the fertilizer only when the potash dressings were heavy. The K balances of the soils were usually negative. 6. In humid climates the amount of calcium leached considerably exceeds that extracted by the crops, even with crops that consume lime. In the long term, the percolation losses from applied fertilizer lime are distinctly influenced by the form of the fertilizer. Although the irrigaiton water partially counteracted the losses, the CaO balances of the soils were very negative. 7. Magnesium behaves somewhat like calcium in the soil, but it is much less mobile. The amount taken up by the crop exceeds the amount leached. As sodium, sulfur, and chlorine are more subject to leaching, the soil balances for these nutrients are negative, except for areas close to industrial zones. In the case of micronutrients, the percolation losses were insignificant in comparison to the amounts extracted by crops. 8. The nutrients from organic fertlizers have to be minieralized in the soil before they can be taken up by the plants. Since the course of this process does not necessarily correspond with the vegetative growth, the leaching losses, especially for nitrogen, are usually much more severe than from mineral fertilizers. Green manuring (intercropping), on the other hand, exerts a positive influence on the soil's nutrient status by creating a favorable rotation effect and increasing the mass of vegetation remaining in the soil. 9. None of the hormone weedkillers (2,4-D, 2,4-DP, MCPA, CMPP, 2,4,5-T) were detected analytically (limit of determination 0.5 ppb) in any sample of percolate. The soil herbicides chloridazon (Pyramin) and fluchloralin (Basalin) were not measurable in the percolate either, at most, traces were discernible in the metabolite. Neither was it possible to detect the plant growth regulator chlormequat chloride (Cycocel) at a depth of 1 m with a limit of determination of 0.002 ppm. © Williams & Wilkins 1979. All Rights Reserved.