| Abstract | Intenzivni uzgoj povrća zahtjeva primjenu većih količina gnojiva, posebno dušičnih.
Dušik kao nitratni ion nema sposobnost vezanja za adsorpcijski kompleks tla, te je sklon
ispiranju u dublje slojeve i u podzemne vode. Ispiranje nitrata iz tla uslijed pretjerane
gnojidbe predstavlja ne samo ekonomski, već i ekološki problem na što su posebno osjetljiva
krška područja. Cilj rada bio je utvrditi utjecaj gnojidbe dušikom i načina pokrivenosti tla na
ispiranje nitrata iz tla, pri uzgoju lubenica u agroekološkim uvjetima Valture. Pokus je
postavljen po split-plot shemi, sa tri razine gnojidbe dušikom (60, 120 i 180 kg/ha) kao
glavnim faktorom i tri različita načina pokrivenosti tla (golo tlo, slama, crni PE film) kao
sporednim faktorom. Prosječni uzorci tla (0-30 cm) uzorkovani su 4 puta tijekom vegetacije
lubenice po varijantama pokusa, a uzorci vode mjesečno iz gravitacijskih lizimetara.
Koncentracije nitratnog dušika u tlu određene su pomoću kompleksa žute boje
fenoldisulfonskom kiselinom (APHA, 1992), a nitratni dušik u vodama određen je metodom
Chapman-a i Pratt-a (1961). Povećanje gnojidbe (60 – 180 kg N/ha) rezultiralo je očekivanim
porastom koncentracija nitrata u oraničnom sloju tla (1,07 do 14,72 mg NO3
-/100 g tla) uz
signifikantne razlike do sredine vegetacije, dok pri kraju vegetacije nije bilo značajnih razlika.
Koncentracije nitratnog dušika u procjednoj vodi lizimetra varirale su od 11,90 mg NO3
-/l do
čak 568,50 mg NO3
-/l ovisno o gnojidbi, pokrivenosti tla i količini procjedne vode, te fenofazi
lubenice. U čak 78,9 % analiziranih uzoraka procjedne vode, utvrđene koncentracije nitrata
prelazile su maksimalno dozvoljenu koncentraciju za pitke vode od 50,0 mg NO3
-/l. Porastom
gnojidbe je raslo i godišnje ispiranje nitrata od 0,03 do 6,46 kg N/ha. Primjena crnog PE filma
smanjuje ispiranje nitratnog dušika iz tla. Najviši prinosi lubenice (69,8 t/ha) ostvareni su
gnojidbom od 180 kg N/ha, ali razlika u visini prinosa u odnosu na ostale varijante gnojidbe
nije bila signifikantna. Primjenom crnog PE filma za malčiranje značajno se povisio prinos
lubenice u odnosu na ostale varijante pokrivenosti tla. |
| Abstract (english) | Intenzivne cultivation of vegetables requires the application of large quantities of
fertilizer, particularly nitrogen. Nitrogen as nitrate ion has no capability for connecting to the
adsorption complex of soil, and it is prone to leaching to deeper layers and groundwater.
Leaching of nitrates from the soil due during fertlization is not only economic but also
environmental problem especially in sensitive karst areas. The objective of this study was, to
determine the effect of nitrogen fertilization and levels of coverage soil on nitrate leaching
from the soil in the cultivation of watermelon in agroecological conditions of Valtura area.
The experimental design was split-plot scheme, with three levels of nitrogen fertilization (60,
120 and 180 kg/ha) as the main factor and three different coverage of the soil (bare soil, straw,
black PE film) as a secondary factor. Average soil samples (0-30 cm) were sampled four
times during the growing of watermelons and a sample of water per month from gravity
lysimeters. The concentrations of nitrate nitrogen in the soil are determined using a complex
yellow color with fenoldisulfonic acid (APHA, 1992), and nitrate nitrogen in the water is
determined by the method of Chapman and Pratt (1961). Increasing fertilizer (60-180 kg
N/ha) developed as expected with increased nitrate concentration in the upper layers of the
soil (from 1.07 to 14.72 mg NO3
-/100 g soil), with significant differences to the middle of the
growing season, until the end of the growing season was not significant differences. The
concentrations of nitrate in percolating water of lysimeters ranged from 11.90 mg NO3
-/l up to
568.50 mg NO3/l depending on fertilization, soil coverage, the amount of percolation water
and stage of development of watermelon. In even in 78.9 % of the analyzed samples of
percolation water, determined concentrations of nitrates are exceed the maximum allowable
level for drinking water of 50.0 mg NO3
-/ l. The increase of fertilization caused increased
nitrate leaching from 0.03 to 6.46 kg N/ha per year. The use of black PE film significantly
reduces the nitrate leaching from the soil. The highest yield of watermelon (69.8 t/ha) was
obtained by applaying 180 kg N/ha, but the difference in yields compared to other variants of
fertilization were not significant. The application of black PE film for mulching significantly
increased the yield of watermelon compared to other variants of soil coverage. |
