Soil and Agriculture: Properties, Formation, and Sustainability, Exams of Environmental Science

Download Soil and Agriculture: Properties, Formation, and Sustainability and more Exams Environmental Science in PDF only on Docsity! 1 Announcements • Exam 2 starts this ~ 1:30 PM, ends Thursday, 10 AM • Extra-credit movies due next Thursday, March 5th • Topics for today: – Soil and agriculture – Review for exam International Service for the Acquisition of Agri-biotech Applications Agriculture and soils • Topics – Soil properties and formation – Erosion – mechanisms and consequences – Agriculture • History and development • Environmental impacts of modern agriculture • Alternatives – Organic farming, sustainable agriculture – (Ch. 13 and 14) Soil Composition See desktop projector 2 Soil composition • Mineral grains – Sand: 0.063 mm – 1 mm – Silt: 0.002 mm – 0.063 mm – Clay: ~0.0005 mm - 0.002 mm • Organic matter (humus) • Living organisms (bacteria, fungi, animals) • Ideal organic-matter concentration: ~ 5% • Best mineral composition: ~40% sand, 40% silt, 20% clay → loam Soil composition and fertility • Property Soil components • Water infiltration Sand • Aeration Sand • Workability Sand • Water-holding capacity Clay, humus • Nutrient-holding capacity Clay, humus • pH Buffering minerals • Salt content Sand Soil composition • Soil horizons: – O Horizon (organic) – A Horizon (top soil) – E Horizon (eluviation) – B Horizon (sub soil) – C Horizon (parent material) Soil development • Top soil formation ~ 1 cm per 100 y • Steps: 1: Weathering 2: Organic-matter addition and decomposition • Chemical weathering → clays Soil composition • Soil horizons: – O.M. from plant productivity – Decomposition generates CO2 (carbonic and organic acids) – Nutrients and dissolved minerals washed out of A – Clays in B horizon trap nutrients and minerals Soils lose soluble nutrients over time Soil formation and worms • Detritivory • Bioturbation 5 Organic farming • Ecosystem management rather than external inputs • Considers environmental and social impacts of fertilizer and pesticide use • Conserves water and soil • Certification: USDA accreditation (farms must be certified) • Organic products: 100%organic, organic (95%), > 70% organic, < 70% organic Does organic-farming work? • 21-y Swiss study (2002) – Yield – 20% less – Resource use reduced Fertilizer (34-53%) Pesticides (97%) – Increased biodiversity • Health benefits – WHO: 3.5-5 million pesticide poisonings per y – Nutrient content – Benefits to consumers? Pesticides in Seattle school children From Lu et al. 2006. Environmental Health Perspectives Concentrations of MDA (solid line) and TCPy (dashed line) correlate with fruit and vegetable consumption! Organic vegetables and fruit consumption resulted in lower concenrations From Lu et al. (2008) Pesticides in Seattle school children Agricultural revolutions • Neolithic revolution • Industrial revolution • Green revolution • Biotechnology revolution Switch in diet to maize (C-4 plant) lead to changes in isotopic composition of humans and drop in skeletal robsustness (From Larsen 1997.) Neolithic revolution 6 Neolithic revolution • Consequences of agricultural revolution on human health – Increase in cavities in human fossil teeth and tooth loss – Changes in skeletal structures (increased cranial lesions, slower growth rates, maxillary shrinkage) – Decrease in skeletal robustness • Other consequences – Increased human population densities – Development of cities and human cultures – Development of other technologies from Larsen 1998 Industrial revolution • Consequences – Increased agricultural productivity – Increased size of farms – Decreased workforce involved with agriculture – Dependence upon fossil fuels – Increased use of fertilizers and pesticides – Development of high-yielding plant varieties Green revolution • Export of developed world’s technology to the developing world (1960s and 70s) – Benefits: Alleviated hunger in much of the world – Problems: • Food production plateau, population size increases • More water required for high-yield crops, ↓ water supplies • Benefits large land owners at expense of subsistence farmers • Biased toward western staples (corn, wheat, rice) • Increased use of pesticides, herbicides, fossil fuels Current revolution - GMOs • Promise: – Disease and pest resistant – Herbicide and pest resistant (reduced tilling, pesticide use) – Higher yield – Increased nutrition (e.g., Vitamin A and iron in “Golden Rice”) – Increased shelf life – Better tasting crops • Problems: – Rapid development of GMO resistance in pests – Potential for gene transfer to non-target species (super weeds?) – Potential for human health problems (e.g., allergic reactions) – High cost to developing world – Lower cash value on the world market Trade issues and GMOs • Trade issues: EU bans some GMO crops entirely (such as corn) or requires labeling for foods with < 1% GMO content. US argues this hurts trade • WTO: EU rules violate trade agreements 7 US GMO regulation • FDA examines food safety GMOs that are "substantially equivalent" to existing crop, require little extra testing. • EPA examines effects of GMOs on environment • USDA examines the effects of GMOs on other crops • About half soybeans and ~ 25% of corn grown in the US has been genetically modified GMOs • Should we support the current revolution? • How can we support alternative agricultural methodologies such as organic farming? Exam review