Is the plant response to available nitrogen forms in soil vary among vegetable crops?
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Date
2019-09-12
Authors
Nawarathna, K. K. K.
Dandeniya, W. S.
Dharmakeerthi, R. S.
Hansika, K. D.
Weerasingha, P.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
Matching preferential needs of crop during fertilization could contribute to increase nutrient use efficiency. A study was conducted to assess crop responses to form/s of N available in root environment of selected vegetable crops. Six crops (Lettuce, Carrot, Capsicum, Tomato, Knolkhol and Cabbage) were grown in a pot experiment with different percentages of NH₄⁺ and NO₃⁻ supplying N (NH₄⁺ and NO₃⁻ as 0:100. 25:75, 50:50, 75:25 and100:0 percent ratio) in sand-culture. Biomass accumulation and uptake of K, P and N were analyzed at the end of vegetative stage. Dicyanamide (DCD), a nitrification inhibitor, was added to maintain desired NH₄⁺ :NO₃⁻ ratio. In another pot experiment, Tomato and Capsicum were grown on soils (Ultisol) collected from two fields (SF1 and SF2) with three N-treatments; T1-control (no urea), T2-Urea and T3- Urea+DCD. Free drainage was not allowed until harvest at 45 days after transplanting. A third pot experiment was conducted repeating same N-treatments with soil SF1 and Capsicum as test crop. In this treatment, free drainage was allowed after irrigation and leachate was analyzed for NO3 - . Biomass accumulation and uptake of N and K were significantly (p <0.05) affected by crop type, N treatment and their interaction. Highest biomass accumulation for Tomato and Capsicum were under 100% NO3 - and 100% NH4 + , respectively. Carrot was not affected by form of N. Lettuce and knolkhol accumulated highest biomass under 75:25 treatment and cabbage performed well under 25:75 treatment. Availability of NH4 + in soils significantly increased under T3 compared to T2 but had no significant effect on biomass accumulation of capsicum and tomato. Leachate from pots contained NO3 - and values were lower under T3 than T2. Vegetable crops have preferential N forms but response to relative abundance of N forms can be different when cultivate in soil.
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Keywords
Ammonium , Biomass accumulation , Nitrate , Nitrogen forms , Vegetable crops