Fluctuation of Mineral Nitrogen Leaching when Applying Different Tillage

Abstract

Expanding economic activity of people has an increasing impact on nature. While implementing restructurization of country economy it is important to apply preventive measures that would help to improve the quality of all surface and subterranean waters including quality of water of all rivers because it significantly influences the condition of the Baltic Sea and Curonian Lagoon. Drainage of agricultural fields is not only a modern measure of removing the surplus of water but also a fair constituent part of water balance of open water bodies. Rainfall or water from melting precipitation percolate into the soil and leak to trenches and little rivers through drainage system. Dissolved chemical elements and residues of chemical plant protection substances in drainage water influence the quality of basin water. At atmospheric nutrition of soil the formation of drainage run-off depends not only on atmospheric conditions (amount of precipitation, their distribution, and regime of air temperature) and hydrological characteristics of soil, but also on technologies and terms of tillage. During the period of research from 2005 to 2010 the average annual height of drainage run-off in the field of reduced tillage fluctuated from 3.18 to 31.6 mm (run-off coefficient į fluctuated in the range from 0.047 to 0.64). The largest amount of water leaks through the drainage in winter (31.5 %), while 27.2 % of water leaks in autumn; 26.9 % in spring and 14.4 % in summer. Average annual drainage run-off in reduced tillage field reached 13.9 mm, i.e. 5.44 % less comparing to conventional tillage fields and 5.04 % higher in comparison to late tillage fields. When applying deep autumn ploughing in August - September, the concentration of mineral nitrogen in drainage water was 15.9 mg / l, i.e. 15.7 % higher comparing to reduced tillage fields. [...]