EFFECT OF DIFFERENT ORGANIC MANURES AND GARDEN WASTE COMPOST ON THE NITRATE DYNAMICS IN SOIL, N UPTAKE AND YIELD OF WINTER-WHEAT

The different ratios of organic to inorganic nitrogen of organic fertilizers affect the nitrate dynamics in soil as well as the yield of crops. To examine this, winter wheat was cultivated on loess in Therwil near Basel (Switzerland). The plots were amended with stacked, composted and rotted manure, garden waste compost, slurry or mineral fertilizer (mineral control). In additional treatments, a top dressing with slurry was applied. Nitrate concentration in soil water was measured with ceramic cups. The N uptake of winter wheat was determined at three growing stages: tillering, flowering and at harvest. The nitrate dynamics in soil water were not significantly influenced by the different organic manures. Only the top dressing with slurry led to slightly enhanced nitrate concentration in the soil water. After sowing in autumn and the following winter period, the organically fertilized plots showed the same nitrate concentrations in soil water in 110 cm depth as the minerally fertilized control. This indicates a similar potential of nitrogen losses in all treatments. The different organic manures strongly affected the winter wheat plants both in the rate of N uptake during the growing season and in the growth rate. However, a high potential of the plants to compensate in later growing stages led to comparable yields in all organically manured treatments. The increased yield in the top dressed plots compared to the plots without top dressing was about 7%.