In this study we investigated the phosphorus (P) content of Baltic soils. In the first set of analyses, 99 soil samples from the Baltic states and Sweden (soil set 1, representing seven different catchments or experimental plots) were analysed for soil P using four extraction methods: ammonium lactate (PAL), double lactate (PDL), Mehlich 3 (PM3) and carbonate (POlsen) (r = 0.85–0.97). In absolute values, results from PM3, PDL and POlsen gave means of 71, 61 and 20%, respectively, of the value from the PAL extraction method. Significantly different relationships were found between P soil concentrations and pH of the extract. In addition, soil pH and organic matter content were found to be of importance. Secondly, we tested 110 soil samples (soil set 2) from five different Swedish monitoring fields with clay soils where PAL clearly correlated with soil P extracted in calcium chloride (PCaCl2) (r = 0.95). Values of a single‐point phosphorus sorption index (PSI) correlated with the aluminium concentration (AlAL) in the lactate extract (r = 0.91) and with (AlOX) in the oxalate extract (r = 0.96). None of the soil P tests with different extraction agents – calcium chloride (PCaCl2), water (Pw), POlsen or PAL– correlated with the mean annual flow‐weighted concentration (1999–2010) of dissolved reactive P (DRP) in drainage water. Neither was there any clear relationship between DRP concentration in drainage water and these tests combined with PSI or with other sorption indices including extracted Al and iron (Fe). However, DRP was related to the clay content of the topsoil (r = 0.91, P < 0.05).
The re-cultivation of abandoned areas creates weed control problems. The main problems in these areas are perennial weeds, such as Cirsium arvense L. but this perennial deep-rooted plant may have a beneficial effect on the physical properties of compacted soil. In order to study the effect of C. arvense's root system on soil properties, the field experiment and a survey of arable fields were conducted in Estonia. The soil bulk density and penetration resistance were measured from soils covered by C. arvense or spring barley (Hordeum vulgare L.) on compacted and un-compacted soil. The results showed significantly lower penetration resistance and bulk density underneath C. arvense than under barley in both the field experiment and a field survey on arable soils. The shoot mass of C. arvense was less affected than the shoot mass of barley by soil compaction and was caused by C. arvense's better ability to develop its root system in compacted soil. Wheat yield, on soils affected by C. arvense, was increased by 28% on loose soil and 37% on compacted soil. It may be concluded that in areas affected by deep-rooted weed species, such C. arvense, the soil's physical properties will improve at least in the first two years.
<p>The phosphorus is an essential element for plant growth. Therefore the pools of plant available P in soil are very important. From the environmental viewpoint, the high level of easily soluble P compounds in soil is a source of risk for leaching and contamination of waterbodies. Also, problems with depleting stock of phosphatic rock ores is increasingly on the agenda. &#160;Approximately 80% of mined phosphatic rocks are used for producing fertilizers and the peak of mining is estimated in 20-30 years. Therefore, it is very important to find other sources for phosphorus fertilizer production.<br>The intensive use of mineral fertilizers causes acidification in soils. To overcome the soil acidification, liming is used. Typically, limestone and chalk are used as liming agent. During several decades also many types of ashes are used for liming agriculturally used fields. In Estonia the oil shale fly ash is used as liming agent already from 1970-s. In 2020 5,1 million tons of oil shale ash as a byproduct was produced in Estonian power plants. The powdered fly ash is a troublesome material for transportation, storage and sowing. The granulation of fly ash helps to overcome these difficulties.&#160;<br>To give the added value to the granulated liming agent, the plant nutrient can be mixed into source material. For modifying granulated ashes also byproducts and residues of some other processes can be used. In our research, the oil shale ash granules were modified by using different ratios of biochar and bone meal. For the comparison, wooden ash with same impurities was used. In pot experiment, different doses of fertilizer were used. The changes in plant available P and pH in soil during 12 month in soil were investigated</p>
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