Impact of precipitation upon nitrate leaching and crop yield at different pipe drainage spacing

The goal of three-year investigations was to determine the influence of precipitation upon drainage discharge and its duration, concentration of nitrate in drainage water, amount of nitrates leached and yields of crops grown: winter wheat ; oilseed rape and soybea, at different pipe drainage spacings (15 m, 20 m, 25 m and 30 m) on pseudogley-gley soil. Investigation were carried out at the experimental amelioration site in the middle of Posavina, in the period from October 2008 up to September 2011. total nitrogen rates Applied amounted to 183.6 kg/ha (2008/09), 175.5 kg/ha (2009/10) and 130 kg/ha (2011). Results show that drainage discharge and its duration depended on the amount and distribution of precipitations during the study period. The highest drainage discharge was determined at the narrowest pipe spacing (15 m), while its longest duration was observed at the widest spacing (30 m. Drainage discharge was not registered in the growing season of the dry 2011. The higest nitrate concentration in drainage water, in all pipe spacing variants, was recorded with the occurrence of the First drainage discharges and was higher than MAC (10 mg/L NO3-N). It was only after the autumn crop harvest that nitrate concentration was below from MAC. The amount of nitrates leached, in each year and at each pipe spacing, depended on the drainage discharge and nitrate concentration in drainage water. Crop yield were statistically significant between the set pipe spacings in the 2008/09 and 2009/10 year, while was not statistically significant in 2011. Effect of pipe in drainage surplus water from soil was positive in humid years, while in the dry year was not registered effect of pipes.