Variations in the Natural ¹⁵N Abundance of Brassica chinensis Grown in Uncultivated Soil Affected by Different Nitrogen Fertilizers

Abstract

To further investigate the method of using δ(15)N as a marker for organic vegetable discrimination, the effects of different fertilizers on the δ(15)N in different growing stages of Brassica chinensis (B. chinensis) grown in uncultivated soil were investigated with a pot experiment. B. chinensis was planted with uncultivated soil and different fertilizer treatments and then harvested three times in three seasons consecutively. For the spring experiments in the years of 2011 and 2012, the δ(15)N value of B. chinensis, which increased due to organic manure application and decreased due to chemical fertilizer application, was significantly different (p < 0.05) with manure treatment and chemical treatment. The δ(15)N value of vegetables varied among three growing stages and ranged from +8.6‰ to +11.5‰ for the control, from +8.6‰ to +12.8‰ for the compost chicken manure treatment, from +2.8‰ to +7.7‰ for the chemical fertilizer urea treatment, and from +7.7‰ to +10.9‰ for the compost-chemical fertilizer treatment. However, the δ(15)N values observed in the autumn experiment of 2011 without any fertilizer application increased ranging from +13.4‰ to +15.4‰, + 11.2‰ to +17.7‰, +10.7‰ to +17.1‰, and +10.6‰ to +19.1‰, respectively, for the same treatments mentioned above. This result was not significantly different between manure treatment and chemical treatment. The δ(15)N values of soil obtained in the spring of 2011 during three growing stages were slightly affected by fertilizers and varied in the range of +1.6‰ to +2.5‰ for CK, +4.7‰ to +6.5‰ for compost treatment, +2.1‰ to +2.4‰ for chemical treatment, and +2.7‰ to +4.6‰ for chemical-compost treatment, respectively. High δ(15)N values of B. chinensis were observed in these experiments, which would be useful to supplement a δ(15)N database for discriminating organic vegetables. Although there was a significant difference between manure treatment and chemical treatment, it was still difficult to discriminate whether a labeled organic vegetable was really grown without chemical fertilizer just with a fixed high δ(15)N value, especially for the vegetables planted simultaneously with chemical and compost fertilizer.

Improved Discrimination for Brassica Vegetables Treated with Agricultural Fertilizers Using a Combined Chemometric Approach

“…The chemical composition of agricultural produce is affected by several factors such as crop species, cultivar, growth stages, soil fertility, climate, cultivation, rotation, and fertilization application. , It is now established that synthetic N fertilizer application results in δ 15 N values in the plants that are lower than those resulting form organic manures. − However, the δ 15 N value of crops is also affected by other factors such as fertilizer type, application amount and time, growth stages, and type of manure. , …”

“…Over the last ten years, many studies have used δ 15 N analysis to discriminate organically and conventionally grown vegetables such as carrots, tomatoes, lettuce, maize, Chinese cabbage, cabbage, onion, paprika, broccoli, and zucchini. − However, overlapping δ 15 N values are sometimes seen in some organic and conventional produce, ,, especially for slower-growing produce and produce fertilizer with mixed chemical–compost applications . This overlap in δ 15 N values was observed in a recent growth study of Brassica chinensis, where it was difficult to discriminate between organic and conventional production methods using nitrogen isotopes alone. Further limitations of this δ 15 N isotope discrimination method are that it does not easily discriminate synthetic nitrogen fertilizers from green manures (containing nitrogen-fixing legumes where δ 15 N air = 0‰) …”

Agricultural Product Authenticity and Geographical Origin Traceability

“…& Zhao J. 2015), chromatography technology (Zhang Z. et al 2016), mass spectrometry technology (Sparkman 2000, Downard 2004, Kondo N. et al 2016, biochip technology (Fan et al 2009), and stable isotope analysis (Yuan Y. et al 2014, Nakano A. & Uehara A.…”

Combined Stable Isotopes and Multi-element Analysis to Research the Difference Between Organic and Conventional Chicken

“…It is important for consumers to understand the differences of products from the two systems. Recently, there are some reports focusing on the differences of organic and conventional agro-products, including pork (Kim et al 2009), eggs (Giannenas et al 2009), milk (Erich et al 2015), and vegetables (Yuan et al 2012(Yuan et al , 2014Laursen et al 2014;Kelly and Bateman 2010). However, there have been few researches focusing on the differentiation of organic and conventional chicken.…”