STUDY ON THE EFFECT OF CUMULATIVE NPK FER TILIZATION IN WHEAT-MAIZE DICULTURE

As a part of a National Fertilization Trial established in the second half of the 1960s, on lime coated chernozem soil at Nagyhorcsok, conta ining 3% humus, 5% CaCO3, originally supplied moderately with N and K, and poorly with P and Zn, between the 13th and 20th years of the Tria l No. B 17, studies were made on the long-term effect of N, P and K fe rtilizations in winter wheat-maize diculture. During that period also the trend in AL-soluble PK contents was followed. The main results can be summed up as followe: On the soil originally with a poor P supply, the cumulative P fertilization with a P2O5 rate of 50 kg/ha/year incr eased significantly the grain yield of winter wheat by 1,9-3,0 t/ha, o f maize by 0,8-3,0 t/ha, of sunflower by 0,4 t/ha between 13-20th year s of the trial. By increasing the rate of P to 100 kg P2O5/ha/year the grain yield of winter wheat rose additionally by 0,1-0,6 t/ha, while it had no influence on the yield of sunflower, in maize it resulted ev en in a significant decrease of 0,4-0,7 t/ha on the poorly supplied Zn soil, due to Zn deficiency induced by P. By raising the N fertilizer level from 50 kg/ha/year to 100 kg/ha/year it gave a significant incre ase in 3 cases from 4 winter wheat years (0,1-1,0 t/ha), in maize in o ne case from 3 years (0,1-0,6 t/ha), and also in the 9ne sunflower yea r (0,2 t/ha). The rise of N rate from 100 to 150 kg/ha/year achieved, however, in winter wheat a further yield surplus of only 0,1-0,2 t/ha, in maize 0,0-0,7 t/ha, in sunflower 0,0 t/ha. The effects of K fertil ization were generally depending on weather and kind of crop. The rate of 100 kg/ha K2O had a yield increasing effect in 2 years from the 4 winter wheat years (0,0-1,0 t/ha), also in 2 years from the 3 maize pr oducing years (0,4-0,6 t/ha), and in the one sunflower year it was als o significant (0,3 t/ha). Among the interactions, the N x P was the st rongest; it was, apart from one year, always statistically proved. In the ploughed layer the AL-P2O5 content of the soil during the 8 years in the non-fertilized treatment fell from 70 to 60 mg/kg, in the ferti lization treatment of 50 kg/ha/year P2O5 from 110 to 100 mg/kg, and re mained further on at the level of poor, moderate, resp. supply. During the two rotations at 150 kg/ha P2O5 level the AL-P2O5 content rose fr om 170 to 190 mg/kg, at P2O5 level of 200 kg/ha/year it rose from 180 to 240 mg/kg, what showed already a good, even a very good P supply. I n the ploughed layer of plots without K fertilization, the AL-K2O cont ent decrease from 180 to 130 mg/kg during the 8 years, between the 13t h and 20th years of the trial. That meant a change from the upper limi t of the moderate supply category to the lower limit ot the same categ ory. On the effect of the yearly fertilization of 100 kg/ha K2O, as a result of the positive K balance, the AL-K2O content rose from 210 to 230 mg/kg indicating a good K supply. The results of the long-term tri al prove that besides the genetic characteristics of the crops, the si ze of the yields vary mainly according to the nutrient and water suppl ies of the soil.