The nitrate content in lettuce leaves depending on the type and the application rate of nitrogen fertilizers

Abstract

Mineral fertilisers, nitrogen ones in particular, have been increasingly used to help achieving high and stable yields of cultivated plants. In terms of the soil nitrogen supply, nitrogen fertilizers have positive effects on yields, but they are often applied inappropriately and at an excessive rate, adversely affecting the nitrate accumulation in the soil and, hence, inducing an increased uptake by the plant. Lettuce is a nitrophilous vegetable that has a pronounced tendency to uptake nitrates. Therefore, the objective of this study was to determine the effect of different types and application rates of nitrogen fertilizers on the lettuce yield and the nitrate accumulation in lettuce leaves. The trials were established at Trbušani, Čačak, in high greenhouses without additional heating on vertisol during the growing seasons of 2007 and 2008. The trial involved the Dutch lettuce cultivar Sportivo and two types of nitrogen fertilisers, KAN and Urea, at rates of 50, 100 and 200 kg N ha-1. The highest yield was produced by the KAN treatment at a nitrogen rate of 200 kg ha-1, and the lowest in the control treatment. The nitrate content in lettuce leaves showed a tendency to increase with the increasing nitrogen application rate. The content was lower under the Urea treatment than under KAN. The lowest nitrate content was found in the control (196 mg kg-1), whereas the highest was obtained at the highest rate of the KAN application (12,684 mg kg-1), followed by the highest rate of Urea (9,464 mg kg-1). .

U cilju postizanja visokih i stabilnih prinosa gajenih biljaka sve se više primenjuju mineralna đubriva, posebno azotna. Sa aspekta obezbeđenja zemljišta ovim hranivom upotreba azotnih đubriva ima pozitivan efekat, ali se veoma često nestručno primenjuju visoke doze ovih đubriva što se negativno odražava na akumulaciju nitrata u zemljištima, a time i povećano usvajanje od strane biljaka. Salata je jedna od povrtarskih vrsta koja pripada grupi nitrofilnog povrća i koja ima izraženu sklonost ka usvajanju nitrata, tako da je cilj ovih istraživanja bio da se utvrdi u kojoj meri različite vrste i doze azotnih đubriva utiču na postizanje visokih prinosa, ali i akumulaciju nitrata u listu salate. Ogledi su postavljeni u mestu Trbušani kod Čačka, u visokim plastenicima bez dopunskog zagrevanja, na zemljištu tipa smonica, tokom vegetacionih sezona 2007. i 2008. godine. U ogledu je korišćena holandska sorta salate sportivo, a primenjene su dve vrste azotnog đubriva KAN i urea, u dozama od 50, 100 i 200 kg N/ha. Najveći prinos ostvaren je primenom KAN sa dozom azota od 200 kg/ha, a najniži na kontrolnoj varijanti. Sadržaj nitrata u listu salate je pokazivao tendenciju porasta sa rastućim dozama azota, pri čemu je niži sadržaj nitrata utvrđen pri đubrenju sa ureom u odnosu na KAN. Najniži sadržaj nitrata utvrđen je na kontrolnoj varijanti (196 mg/kg), dok je najviši sadržaj utvrđen pri đubrenju sa najvećom dozom KAN (12.684 mg/kg), a zatim primenom najveće doze uree (9.464 mg/kg). .