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Sustainable agriculture implies the use of biological resources. Farmyard manuring (FYM) and ploughing in plant residues have an important role in maintaining soil fertility. Our aim was to study the effect of various combinations of organic and mineral N-fertilizers on the C org content of the soil, grain yield, dry matter production, and N uptake of barley. A model pot experiment was set up with spring barley. Large pots were filled with 46 kg sandy loam soil originating from the plots of the "International Long-term Experiments for Investigating the Effect of Organic and Inorganic Fertilisers," Keszthely, Hungary. The field experiment, which was set up in 1983, contains three crop rotations with winter wheat, winter barley, and maize. Treatments: 1) inorganic fertilizers only with increasing N doses (N); 2) FYM in every 3rd yr þ N; 3) stalk, straw, or green manure þ N. Yield results gained in the field experiment with winter barley were also evaluated. In the 18th yr of the experiment, FYM þ N resulted in significantly higher C org content than with treatments 1 and 3. Grain yields in the field trial were the lowest in treatments without organic matter recycling. In the pot experiment, dry matter production and N uptake of the grains and vegetative plant parts were significantly higher in treatments with FYM þ N. Our results clearly prove the advantage of FYM combined with mineral fertilization over the other treatments.

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Corn (Zea mays L.) leaf weight, leaf P concentrations at flowering stage, 0.01 M CaCl 2 -, Olsen-, LE-, and AL-soluble soil P contents were determined in a network of uniformed 27-year-old Hungarian long-term field trials (the so-called National Longterm Field Trials, NLFT) with four P fertilization rates on nine locations, representing various agro-ecological and soil conditions of the country.A 4 -5 fold increase in soluble P contents was found in all soil P-tests, while the absolute values of dissolved P varied greatly (CaCl 2 -P: 0.1 -3.7; Olsen-P: 3.7 -47.7; and AL-P: 3085Soil and plant P analyses data proved to be useful tools in adapting the results of long-term field trials for improved, environmentally sound fertilizer recommendations. CONCLUSIONSThe correlation between Olsen P and corn leaf P indicate that both methods are suitable for evaluating soil and corn P status under the agro-ecological conditions of Hungary. Soil test methods less dependent of soil texture and reaction status show better correlation with plant P contents and responses to P than methods more dependent.Soil and plant P analyses data are useful tools in adapting the results of long-term field trials for developing fertilizer recommendations. ACKNOWLEDGMENTSThe scientific board for planning and development of the the experiments included Professors G. Láng (chairman), E

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