The growth, and the development and trends of the nutrient content parameters of three different plant species (Phacelia tanacecifolia,Sinapis alba, Raphanus sativus) grown as secondary crops for green manure, as a function of two different fertiliser doses (0 kg/ha N; 50kg/ha N), was studied under unfavourable site conditions at the Crop Production and Biomass Utilisation Demonstration Centre of theSzent István University, Gödöllő, Hungary. The application of the small, 50 kg/ha dose of nitrogen increased the biomass yield in eachcase, to 2.78-3.11 times that of the control field. The dry matter content of the produce increased only by 2.11-2.66 times, as the watercontent of the green manure plants also increased as a result of the nitrogen supplement. The increased amount of nitrogen boosted theavailability of all of the other macro elements for the plants. In view of the present findings it can be recommend the application of somenitrogen fertiliser in the given site before growing some crop for use as green manure in all cases but where the straw after cereals is left onthe soil surface nitrogen should be applied to alleviate the pentosan effect and to increase the uptake of macro elements.
