Long-term studies of crop yields with changing rainfall and fertilization

The anthropogenic effects of global climate change on water resources may be masked by natural climate variability. With a warmer climate, drought and excess rainfall conditions could become more frequent, severe, and longer-lasting. The potential increase in these natural hazards is of concern, given the stresses they place on water resources and agricultural production, and the high costs that result from these hazards. For these reasons, long-term studies were conducted in Eastern Hungary from 1962-2001 in order to obtain the relationship between rainfall quantities, soil agrochemical properties, and mineral fertilization on yields of rye, potato, winter wheat and triticale. Averaged rainfall quantities over many years, experimental years, and phenological phases over many years and experimental years for rye were 567 mm, 497 turn, 509 mm and 452 mm; for potato 551 mm, 537 mm, 337 mm and 294 mm; for winter wheat 586 mm, 509 mm, 518 mm and 467 mm; for triticale 551 mm, 537 mm, 489 mm and 497 turn respectively. Rainfall deviations (+/-) from the average over many years in the experimental years and during the phenological phases for rye were -12 % and -11 %; for potato -3 % and -13 %; for winter wheat -13 % and -10 %; and for triticale -3 % and 2 %. During the vegetation period, the relationships between rainfall quantity, nutrition (N, P, K, Ca, Mg), and yield were characterized by polynomial correlations "R" (rye: 0.65-0.99, potato: 0.95-0.98, winter wheat: 0.54-0.76, triticale: 0.28-0.67). Maximum yields of 4.0 t ha(-1) for rye, 21.0 t ha(-1) for potato, 3.4 t ha(-1) for winter wheat, and 5.5 t ha(-1) for triticale were observed when the respective natural rainfall amount was in the range of 430-500, 280-330, 449-495 and 550-600 mm. At rainfall amounts above and below these ranges, crop yields are drastically reduced.