An inexpensive method for identifying high phosphorus (P) loads on ditches carrying water from critical source areas ("hot spots", i.e. manure-affected areas) was tested. Water flowing from the hot-spot areas is rich in dissolved nutrients (e.g. P) and nutrient-rich eroded material. In this study the water from hot spots contained an average of 2.2 mg/l dissolved reactive P but field ditch water 0.14 mg/l. We selected 62 ditches with varying P-load levels for sediment analysis. Five ponds and 16 lakes were also studied. The sediment samples were analysed by the AAAc-extraction (0.5 M ammonium acetate, 0.5 M acetic acid, pH 4.65) method used for routine soil testing in Finland. The analysis of sediment AAAc-P proved to be a useful method for identifying ditches carrying high P waters from hot spots. Half of the ditch sediments in the hot spot ditches showed high or excessive P concentrations. AAAc extraction of the sediment is less expensive than water analysis and the sampling can be extended to periods when no water flows in the ditches.;
Abstract. Manganese was extracted with a solution containing 0.5 M NH"-acetate, 0.5 M acetic acid and 0.02 M Na 2 -EDTA at pH 4.65 (AAAc-EDTA) from 86 soil samples collected from plough layers in Finland. The results were compared to the quantities of exchangeable, reducible (three methods) and total Mn of the soil samples as well as to Mn uptake in a pot experiment in which four yields of ryegrass were grown. Mn AAAc . EDTA ranged from 1.8 to 158.8 mg/kg, mean 32.2 mg/kg. correlated more closely with reducible Mn (r = o.B2*** -o.B7***) than with total Mn (r = o.so***) or exchangeable Mn (r = o.4s***), suggesting a relationship between reducible Mn and Mn AAAcEDTA . In order to take into account the effect of pH on plant-availability of the indices were multiplied by two different pH correction coefficients. The pH correction resulted in a closer correlation between Mn AAActDTA and exchangeable Mn, but in a poorer correlation between Mn AAAc . EDTA and reducible Mn. The pH-corrected indices or exchangeable Mn explained the variation in the Mn content of the first ryegrass yield to a higher degree (R 2 = 33-38 %) than did the original indices (R 2 = 3 "Id). However, the original indices explained 38 -55 % of the variation in the Mn content of subsequent ryegrass yields, whereas the pH-corrected indices explained only 16-34 % of the variation. Thus, Mn AAAcEDTA is an indicator of the potentially plant-available reserves of Mn, while the pH-corrected indices reflect the quantity of the readily available Mn in the soil.
The aim of the study was to determine the plant-available manganese in the soil and to study which factors regulate the plant-available manganese. The material consisted of 193 mineral soils and 17 organogenic soils. Oats (Avena saliva L.), Italian ryegrass (Lolium multiflorum Lam.) and turnip rape (Brassica campestris oleifera L.) were used as the test plants in the pot experiments. A cation exchange resin method was developed for extracting soil manganese. The method enabled both exchangeable and reducible manganese to be determined. Exchangeable manganese comprised the manganese which was freely present in the soil solution in cationic form, and the manganese in cationic form which could be exchanged from the soil. Reducible manganese was the manganese reducible to the oxidation state, Mn2+, by the action of hydroquinone, hydroxylammonium chloride or ascorbic acid. The content of exchangeable manganese in the soil explained 33,7 % of the variation in the manganese content of the first yield of ryegrass. The greater the number of yields harvested, the smaller was the significance of the content of exchangeable manganese in the soil as an independent variable. On the other hand, when the content of reducible manganese in the soil was used as the independent variable, then the greater the number of yields harvested, the better it explained the variation in the manganese content of the yield. The content of manganese reduced by hydroxylammonium chloride explained 68,6 % of the variation in the manganese content of the fourth yield. The contents of exchangeable manganese and manganese reducible by ascorbic acid explained 73,4 % of the variation in the manganese content of the roots. The pH, the organic carbon content and the content of hydroquinone-reducible manganese in the soil explained 67,0 % of the variation in the content of exchangeable manganese in the plough layer of the mineral soils. The content of "total" manganese in the plough layer of the mineral soils explained 27,6 % of the variation in the content of ascorbic acid-reducible manganese. The plant stands increased the content of exchangeable manganese in the soil and decreased the redox potential of the soil in comparison to the incubated soils. The content of exchangeable manganese started to increase when the redox potential of the soil fell below 0,59 V. Adding glucose promoted the reduction of manganese in the soil, reduction appearing to be both biological and non-biological in origin. Soil moisture increased the content of exchangeable manganese when the moisture was higher than the field capacity. Liming decreased the content of exchangeable manganese in the soil more than would have been expected on the basis of the change in pH values. The manganese content and manganese uptake of the crop were also reduced. Adding large amounts of manganese (Mn 51,5 kg/ha*20 cm) did not prevent liming (calcite 14 t/ha*20cm) from reducing the manganese content of the yield.
Increasing concentrations of arsenic and heavy metals in agricultural soils are becoming a growing problem in industrialized countries. These harmful elements represent the basis of a range of problems in the food chain, and are a potential hazard for animal and human health. It is therefore important to gauge their absolute and relative concentrations in soils that are used for crop production. In this study the arsenic and heavy metal concentrations in 274 mineral soil samples and 38 organogenic soil samples taken from South Savo province in 2000 were determined using the aqua regia extraction technique. The soil samples were collected from 23 farms.The elements analyzed were arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc. The median concentrations in the mineral soils were:As 2.90 mg kg 1, Cd 0.084 mg kg 1, Cr 17.0 mg kg 1, Cu 13.0 mg kg 1, Hg 0.060 mg kg 1, Ni 5.4 mg kg 1, Pb 7.7 mg kg 1, Zn 36.5 mg kg 1. The corresponding values in the organogenic soils were:As 2.80 mg kg 1, Cd 0.265 mg kg 1, Cr 15.0 mg kg 1, Cu 29.0 mg kg 1, Hg 0.200 mg kg 1, Ni 5.9 mg kg 1, Pb 11.0 mg kg 1, Zn 25.5 mg kg 1. The results indicated that cadmium and mercury concentrations in the mineral and organogenic soils differed. Some of the arsenic, cadmium and mercury concentrations exceeded the normative values but did not exceed limit values. Most of the agricultural fields in South Savo province contained only small amounts of arsenic and heavy metals and could be classified as Clean Soil. A draft for the target values of arsenic and heavy metal concentrations in Clean Soil is presented.;
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