NATURAL WATER SUPPLY AND FERTILIZATION INTERACTIONS ON CROPS YIELD IN FRAGILE AGROECOSYSTEM

摘要

Drought and excess rainfall conditions result in the breakdown between man and his environment. The effects of drought and excess rainfall situations on a community require extraordinary efforts to cope, oftentimes with outside international aid. The effects of global climate change on water resources may be hidden by natural climate variability. With a warmer climate, drought and excess rainfall cases 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 high costs that result from these hazards. For these reasons, the effects of rainfall variation (quantity, distribution) and fertilization (N, P, K, Ca, Mg) on soil (Haplic Luvisol-acidic sandy brown forest soil) system was evaluated for crop yield (rye, potato, winter wheat, and triticale) as part of a 43-year field experiment that began in 1962 at Nyirlugos (Nyirseg, a fragile eco-region of Eastern Hungary). The ploughed soil (0-25 cm) had the following agrochemical characteristics: pH (H_2O) 5.9, pH (KCl) 4.7, hydrolytic acidity 8.4, hy_1 0.3, humus 0.7%, total N 34 mg· kg~(-1), ammonlactate (AL) soluble-P_2O_5 43 mg· kg~(-1), AL-K_2O 60 mg· kg~(-1). From 1962 to 1980 the experiment consisted of 2x16x4x4 = 512 plots and from 1980 of 32 x 4 = 128 plots in split-split-plot and factorial random block designs. The gross plot size was 50 m~2. The average fertilizer rates in kg· ha~(-1)year~(-1) were nitrogen 45, phosphorus 24 (P_2O_5), potassium 40 (K_2O), magnesium 7.5 (MgO) until 1980, and nitrogen 75, phosphorus 90 (P_2O_5), potassium 90 (K_2O), calcium 437.5 (CaCO_3) magnesium 140 (MgCO_3) after 1980. Averaged rainfall quantities over many years, in the experimental years, during phenological phases in the many years, and in the experimental years for rye were 567, 497, 509, 452 mm, and for winter wheat 586, 509, 518 and 467 mm. Rainfall deviations from the many years's average in the experimental years and during the phenological phases of potato were -3%, -13% and of triticale 2% and -3%. During the vegetation period, the relationships between rainfall quantity, nutrition (N, P, K, Ca, Mg), and yield were characterized by polynomial correlations (Rye, control: R = 0.99; N: R = 0.84; NP: R = 0.84; NK: R = 0.91; NPK: R = 0.85; NPKMg: R = 0.65. Potato, control: R = 0.98; N: R = 0.95; NP: R = 0.96; NK: R = 0.95; NPK: R = 0.98; NPKMg: R = 0.96. Winter wheat, control: R = 0.59; N: R = 0.57; NP: R = 0.76; NK: R = 0.54; NPK: R = 0.67; NPKMg: R = 0.71. Triticale, control: R = 0.35; N: R = 0.28; NP: R = 0.47; NK: R = 0.37; NPK: R = 0.63; NPKCa: R = 0.67; NPKMg: R = 0.67; NPKCaMg: R = 0.62). Maximum yields for rye: 4.0t ·ha~(-1), potato: 21.0t· ha~(-1), winter wheat: 3.4t· ha~(-1), and triticale: 5.0-6.0t· ha~(-1) 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, there was a corresponding quadratic reduction in the yield.