Nitrogen is often applied in excessive quantities, causing nitrogen losses. In recent years, the management of large quantities of manure and slurry compounds has become a challenge. The aim of this study was to assess the usefulness of the proxy tools Yara N-testerTMand RapidScan CS-45 for diagnosing the N nutritional status of wheat crops when farmyard manures were applied. Our second objective was to start designing a N fertilization strategy based on these measurements. To achieve these objectives, three annual field trials were established at three close locations with similar soils. Three kinds of initial fertilizers [dairy slurry (40 t ha-1), sheep manure (40 t ha-1) and conventional (no organic fertilizer on basal dressing and 40 kg N ha-1at tillering)] were added and five N mineral fertilization dose applied at stem elongation for each kind of initial fertilization. The proxy tools were used at stem elongation (GS-30) before applying the mineral N. Proxy tool readings look promising in order to adjust the N application rate at stem elongation. In dairy slurry, when both proxy tool values were 60 - 65 % the optimum N rate at stem elongation for achieving the maximum yield was 118 - 128 kg N ha-1. In dairy slurry and conventional treatments when readings were 85 - 90 % the optimum N rate was 100 - 110 kg N ha-1. However, at the sheep manure treatment, it is more difficult to find a relationship between sensor readings and yield. Moreover, when organic fertilizers were applied before sowing, the usual first N topdressing at the beginning of tillering could be avoided in years with humid spring.