Evaluation of Nutrient Leaching Losses in Red Onion Grown on Sandy Regosols in Kalpitiya under Intensive Farming Systems
Gayathri Swarnathilake, Indika Herath, Radhika Gimhani and Lahiru Udayanga
Background: Red onion is a short-term crop cultivated in Kalpitiya with excessive use of fertilizer, leading to contamination of groundwater. Therefore, the current study aimed to evaluate the leaching potential of plant nutrients from red onion cultivations managed under grower managed fertilizer practices, compared to Department of Agriculture (DoA) recommendations.
Methods: This study was carried out in Kandakuliya, where lysimeters were installed below the soil surface of separated plots. The variety Jaffna Local was used in the experiment. Growers’ fertilizer practice was considered as the treatment 1 (T1). The DoA recommendation was used as treatment 2 (T2). The available P, total N, exchangeable K+, Ca+2, F–, NO3– and NH4+ concentrations in the initial soil samples and leachate were analyzed using standard methods. The two-sample t test was used for statistical analysis.
Results: The mean cumulative Ca+2, NO3– and P denoted significant differences, among the leachate collected from the two treatments. The concentration of NO3– in both treatments ranged from 35.1 mg/l to 160 mg/l. which was higher than the WHO permissible level of NO3– (50 mg/l) for drinking water. However, the mean values of cumulative leached NH4+ and K+ did not indicate significant differences between the treatments. The highest mean cumulative values of Ca+2 (659.6 kg/ha), F- (4.9 kg/ha) and P (26.4 kg/ha) were observed in the leachate collected from T1.
Conclusions: Among all the tested substances, NO3– was found to be the critical element in terms of leaching and contamination of groundwater. This emphasizes the pressing need for an improved nitrogen management strategy for the sustainable production of red onion grown in Kalpitiya.
Keywords: Fertilizer, Groundwater Contamination, Nutrient Leaching, Sandy Regosols