Fraud in organic farming may become an increasing concern as the sector experiences rapid year-on-year growth, leading scientists to develop ways to test whether synthetic fertilizers were used.

A new report, published this month in the Journal of Environmental Quality, demonstrated how scientists have successfully use nitrogen isotopic discrimination to determine if non-organic, synthetic fertilizers were used on sweet pepper plants.

"Isotipic discrimination has demonstrated that we can successfully identify fraud if synthetic N fertilizers are used in the organic production of sweet peppers," wrote the researches from the Instituto Murciano de Investigacion y Desarrollo Agrario y Alimentario jointly with the Instituto de Agrobiotecnologia in Spain.

"However, further studies including the effects of different soil characteristics, climate, and biotic or abiotic stress could be useful in determining the proper interval of 15N-values to exclude non-organic fertilization practices for certification policies," they added.

Moreover, the scientists, led by Francisco del Amor, found that regardless of the organic manure used, no additional fertilization (synthetic or organic) is required before 106 days after transplanting because plant fresh weight was not reduced.

This conclusion is important for conventional farmers who apply manure pre-planting for biofumigation with solarization because the use of methyl bromide is banned.

Organic farming

The world organic market has been growing by 20 per cent a year since the early 1990s, as concern has grown about food quality and safety. Consumers consider organic products to be safer for health due to the absence of pesticide residues.

Regulations on organic farming mean organic products are subject to controls by an accreditation and certification system. In particular, they must be recorded at each step of the production.

However, in managing organic farming, it could be difficult to establish a correct fertilization because of differing compositions of the manure used.

The study

Stable isotope abundances were determined in sweet pepper plants under controlled ambient and soil conditions in a greenhouse.

Leaves, stems, roots and fruits were analyzed in plants cultivated organically or with synthetic fertilizer amendments.

Three types of animal manures (sheep, hen or horse) were applied at preplanting, and during the crop cycle half of the plants in each manure zone received only water, and the other plants received chemical fertilizers as commonly used in conventional cultivation.

The results of this study showed that the use of synthetic fertilizers significantly reduced the ratio between the nitrogen isotopes 15N2 and 14N2, compared to what is observed naturally in the atmosphere.

Naturally, 99.64 percent is 14N with 0.36 percent 15N. Synthetic fertilizers typically have a 15N content close to zero.

It also showed that old leaves and fruits were more sensitive to the synthetic fertilizer additions and, independently of the organic manure used, no additional fertilization was required before 106 days after transplanting with the common dosage of manure, as plant fresh weight was not reduced.

Source: Food Navigator USA