engleski

INFLUENCE OF TRADITIONAL AGRICULTURAL PRODUCTION ON NITROGEN AND PHOSPHORUS LEACHING IN EASTERN CROATIA

Water contamination caused by agricultural activities is an increasingly topical issue for the general public in Croatia, especially in the regions where there are problems of increased concentrations of nitrates, phosphates and pesticide residues in drinking water, but also in surface watercourses. The major aim of this study was to estimate the effects of traditional agricultural production in Eastern Croatia on nitrogen and phosphorus leaching, and thereby also on potential contamination of percolating water and groundwater in this agriculturally important region. Investigations were carried out in Eastern Croatia during the five-year period 2002-2006. The results obtained are based on lysimeter investigations, in which use was made of Zero Tension Pan Lysimeters. Analyses done in the studied period involved the amounts of nitrogen and phosphorus leached in lysimeter percolates in traditional production of major field crops (maize, wheat, alfalfa and natural meadow). Investigations were conducted on four separate locations. According to the indicators (mean values) obtained in five-year investigations, nitrogen and phosphorus fertilization of crops grown on monitored locations was as follows: 1. alfalfa 170 kg N/ha +80 kg P/ha, 2. wheat 180 kg N/ha + 60 kg P/ha, 3. maize 210 kg N/ha + 140 kg P/ha, and 4. natural meadow 180 kg N/ha + 60 kg P/ha. The average long-term precipitation sum for the studied period (2002-2006) was 675 mm. Average annual values of percolating water (percolate) from lysimeters, calculated for monitored locations and crops grown, were: location 1. (alfalfa) 155 mm ; location 2. (wheat) 178 mm ; location 3. (maize) 201 mm, and location 4. (natural meadow) 167 mm. Mean values of total nitrogen concentration in mg/ N/l in percolating water (percolate) from lysimeters for monitored locations were: locations: 1. (4.44) ; 2. (8.26) ; 3. (13.60), and 4. (3.71). The following average values of phosphorus concentration were also measured (mg P/l) on each location: 1. (0.46) ; 2. (0.44) ; 3. (1.81), and 4 (0.26). Indicators obtained over the five-year investigation period revealed that the highest nitrogen and phosphorus leaching occurred in the row crop (maize) and the lowest on natural meadow. In dependence on the crop grown, time and quantity of nitrogen applied to the soil by fertilization, amount and distribution of precipitation, amount of percolate and agrotechnical practices applied, the amounts of nitrogen leached ranged from the minimal 6.19 kg N/ha on location 4. (natural meadow) to maximal 27.33 kg N/ha on location 3. (maize). Low phosphorus leaching, ranging from 0.26 kg P/ha (meadow) to the maximal 1.81 kg P/ha (maize), was determined for the crops grown in the five-year investigations. The results of the five-year (2002-2006) lysimeter investigations and the obtained indicators allow the conclusion that traditional agricultural production in Eastern Croatia involves a potential risk of higher contamination of ground and surface water by nitrogen and, to a much lesser extent, by phosphorus.

agriculture; contamination; water; nitrogen; phosphorus; alfalfa; wheat; maize; meadow

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