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Die Bodenkultur - Journal for Land Management, Food and Environment
I. Šimunić, F. Tomić, M. Mesić and I. Kolak:
Nitrogen Leaching from Meliorated Soil
The research object was to investigate the influence of different pipe drainage systems on the concentration and quantity of nitrogen leached in the production of agricultural crops on hydroameliorated Gleyic Podzoluvisol in the central Sava Valley. Nitrogen leaching was investigated in four different variants of drainpipe spacing (15 m, 20 m, 25 m and 30 m). The same crop was grown and the same agricultural practices applied in all trial variants and in all trial years.
The results achieved indicate that the quantity of precipitation in the trial period had a substantial influence on the dynamics of nitrogen leaching in all trial variants. Differences in the total quantity of drainage discharge were recorded both between the tested variants in each trial year and between trial years. In 1996 drainage discharge ranged from 77 l.m-2 (8.4 % of total annual precipitation) to 82 l.m-2 (8.9 %), in 1997 from 13 l.m-2 (1.6 %) to 23 l.m-2 (2.8 %), and in 1998 from 185 l.m-2 (18.5 %) to 194 l.m-2 (19.4 %).
Maximum concentrations of NO3-N were over 10 mg/l in all variants, while the average NO3-N concentrations were either lower or higher than 10 mg/l. NO3-N concentrations over 10 mg/l were recorded during rainy periods, after fertilizer application. The average NH4-N concentration was generally higher than 0.1 mg/l, while its maximum value went up to 2.9 mg/l.
Quantities of leached nitrogen varied per years and per trial variants. The lowest nitrogen leaching was recorded in 1997, the quantities ranging from 3.1 kg/ha (1.8 % of the total nitrogen added with fertilization) to 5.5 kg/ha (3.2 %). The highest leaching occurred in 1998, the N quantities ranging from 15.5 kg/ha (7.6 %) to 19.8 kg/ha (9.8 %).
Analysis of variance did not render any statistically significant differences in drainage water concentrations of NO3-N and NH4-N for any of the trial years, and neither in the quantity of leached nitrogen between the tested variants of pipe drainage spacing, at P = 0.05 and 0.01.
Different quantities of leached nitrogen were conditioned by the climate, that is, the quantity and distribution of precipitation, crops grown, that is, crop development stages in crop rotation, as well as by the agricultural practices and the time when each particular practice was applied.
Key words: leaching, nitrogen, waters, Gleyic Podzoluvisol.