Nils Brink

Effects of differentiated applications of fertilizer N on leaching losses and distribution of inorganic N in the soil

SummaryNitrogen fertilizer was applied to field plots at rates of 0, 50, 100, 150 and 200 N kg/ha yr, in order to determine the effects of differentiated N applications on drainage water and groundwater quality. Water samples, collected monthly or bimonthly from 1974 to 1983, were analysed for inorganic and total N content. In order to see the impact of residual N on leaching losses, soil samples were collected to a depth of 2 m in the N0, N100 and N200 plots, usually in September and April.Leaching of nitrate was moderate to the N100 level but increased substantially with increasing fertilization, up to 91 N kg/(ha-yr) for the highest application rate (N200), during the wet year of 1980/81. The losses were greatest during the fall, mainly due to high levels of N remaining in the soil after harvest combined with high precipitation. The N content of the groundwater did not show any significant correlation to the fertilization intensity.A buildup of inorganic N in the soil occurred only when excessive amounts of fertilizer were applied (N200), while the contents of the N0 and N100 treatments fluctuated around states of balance, approximately 45 and 70 N kg/ha respectively.Spring rape followed by winter wheat showed a great ability to reduce N contents in the tile effluent from highly fertilized plots (N150 and N200), even though the plots had received excessive amounts of fertilizer for several years.Results of this experiment in central Sweden demonstrate the importance of applying nitrogen fertilizer in balance with crop needs and of maintaining a growing crop cover as much of the time as possible in order to minimize water pollution.

Composting of Food Waste with Straw and other Carbon Sources for Nitrogen Catching

Abstract Food waste, straw, paper and topsoil were composted in different combinations. The catching of nitrogen was more than 90% when using different amounts of straw and of a small amount of paper. It was above 50% in paper composts at high maximum temperature and below 46% at low temperatures. A cultivation test with tomato, cucumber and white cabbage in one of the paper composts gave good yields. A comparison is made with the nitrogen catching in earlier experiments.

Relations between element-concentrations and water discharge in agricultural basins

Summary 1. The relation beween water discharge and concentration of NO 3 -N, TP, DRP, K, Ca, Cl, and SO 4 -S was tested for three Swedish (FL, NA, SK) and one Czechoslovak (-BE) agricultural catchments. The relation was described by a hyperbola. 2. The relation was positive up to a discharge of 5–8 mm/day for NO 3 in all catchments, and was highly significant. NO 3 -N increased with discharge similarly but from different starting points depending on soil type and intensity of fertilization. Deviation to low NO 3 -N concentrations at the same discharge occured after previous washing-out of soil NO 3 -N at high discharge, cropping of effective nitrate utilizers, and short periods without vegetation cover. Deviation to high nitrate concentrations occured after long dry periods, N 2 fixation by legumes, and luxury N fertilization. 3. A significant positive relation was found for phosphorus (TP and DRP) for the clay soil FL only, during a period of slowly changing discharge and frequent sampling. The losses of P there were related to the intensity of erosion. At BE, with a soil similar to that of FL, erosion was minimized by a grass rim along the lower end of the field. 4. The concentration of potassium was also positively related to flow rate at FL after ploughing-in ley or after application of manure. Less significance was observed for the rest of the FL data, a negative one forNA and none for SK. 5. Sulphate and chloride were positively related to flow rate in two Swedish areas in a short pulse in years following fertilization, and eventually changed to negative relations in subsequent years. Both Cl and SO 4 -S were positively related to flow rate in the Czechoslovak catchment. This discrepancy may be related to a more or less regular application of the elements, different field slope and different water flow pattern in soil.

Composting of Food Waste, Waste Paper and Milk Carton, and Cultivation in Ready Compost

Abstract Food waste from a hospital was composted with waste paper, milk carton and topsoil in different combinations. The ready compost reflected the high content of N, P, K, S, Cl, Na and K in the food waste and that of Mg in the soil. There was a great deal of Ca in all the raw materials. The topsoils content of heavy metals was decisive for the levels in the ready compost: these levels were very low. The leachate was strongly polluted, but the run-off was negligible. The loss of nitrogen was at least 50%. Cultivation tests with tomato showed that the plants responded well in a diluted ready compost of paper, and that there were distinct toxic symptoms on plants in the compost made of milk carton.

Composting of Food Waste and Catching Nitrogen

Abstract Food waste from a school and a restaurant was composted with topsoil only and together with topsoil, cattle manure, stock compost and sewage water in different combinations. The temperature maximum reached 46–55 °C in composts with 50% wet weight, and 33–36 °C in composts with 20–30% wet weight. Leachate was strongly polluted. The loss of elements in that way was negligible. The loss of dry matter (DM) was 9–19%, and that of carbon (C) was 36–62%. The loss of nitrogen to the air was less than 10% in a compost containing biodynamic stock compost, and 40–47% in the other. The amount of topsoil and stock compost seems to be decisive.