mg/kg) Lime sulfur (aka calcium polysulfide) and sulfur are considered to be allowed, synthetic materials (LD50: 820 mg/kg) Neem oil is used as an insect repellant in India; since it contains azadirachtin its use is restricted in the UK and Europe. Pyrethrin comes from chemicals extracted from flowers of the genus PyrethrumPyrethrum (LD50 of 370 mg/kg). Its potent toxicity is used to control insects. Food quality and safety While there may be some differences in the amounts of nutrients and anti-nutrients when organically produced food and conventionally-produced food are compared, the variable nature of food production and handling makes it difficult to generalize results, and there is insufficient evidence to make claims that organic food is safer or healthier than conventional food.Blair, Robert. (2012). Organic Production and Food Quality: A Down to Earth Analysis. Wiley-Blackwell, Oxford, UK. Claims that organic food tastes better are not supported by evidence. Soil conservation Supporters claim that organically-managed soil has a higher quality and higher water retention. This may help increase yields for organic farms in drought years. Organic farming can build up soil organic matter better than conventional no-till farming, which suggests long-term yield benefits from organic farming. An 18-year study of organic methods on nutrient-depleted soil concluded that conventional methods were superior for soil fertility and yield for nutrient-depleted soils in cold-temperate climates, arguing that much of the benefit from organic farming derives from imported materials that could not be regarded as self-sustaining. In Dirt: The Erosion of Civilizations, geomorphologist David Montgomery outlines a coming crisis from soil erosion. Agriculture relies on roughly one meter of topsoil, and that is being depleted ten times faster than it is being replaced. No-till farming, which some claim depends upon pesticides, is one way to minimize erosion. However, a 2007 study by the USDA's Agricultural Research Service has found that manure applications in tilled organic farming are better at building up the soil than no-till.Hepperly, Paul, Jeff Moyer, and Dave Wilson. "Developments in Organic No-till Agriculture." Acres USA: The Voice of Eco-agriculture September 2008: 16-19. And Roberts, Paul. "The End of Food: Investigating a Global Crisis." Interview with Acres USA. Acres USA: The Voice of Eco-Agriculture October 2008: 56-63. Gunsmoke Farms, a organic farming project in South Dakota, suffered from massive soil erosion as result of tiling after it switched to organic farming. Biodiversity The conservation of natural resources and biodiversity is a core principle