Unit 2 : Food Production – Techniques, Issues & Health Impacts Topic 5 : Agriculture Lesson 1 : Agricultural Science I Photosynthesis - Without it, there would be no life; agriculture is based upon photosynthesis - It is a rxn whereby plants take up water, CO 2 , & light and produce oxygen + all the chemicals that make up the plant - Important b/c that’s what we eat sometimes indirectly . When we eat meat, we eat the plants through the animal Agriculture - 50 years ago, 70% of the world were farmers… now its 2% w/o farmers, we wouldn’t have any food to eat - Developed through domestication of plants & animals that enabled us to grow crops - This led to growth in population, which led to growth in agriculture - We need to increase use of fertilizers and pesticides to feed increasing population (10 billion ppl coming to dinner by 2050) but right now, we are having trouble feeding everyone in the world - Pesticides are there to kill pests, weeds & fungi w/o them & fertilizers we wouldn’t be able to produce enough food - Pesticides is a term that encompasses herbicides (specific to plants), fungicides (specific to fungi) and insecticides (specific to insects & animals) It would be great if all the food could be grown organically o Organic means growing crops w/o the use of synthetic fertilizers, w/o using synthetic pesticides, and essentially relying on natural means to control insects This can be done by planting various kinds of crops using nothing but natural techniques BUT on a larger scale, it becomes very difficult What we would use as a fertilizer, for ex, in organic agriculture would be manure o Manure decomposes, it releases various kinds of nutrients that are needed for growth of crops BUT there’s NOT enough manure in the world to sustain all of the crops that are needed , thus, we need to look at this in a more scientific basis Justus von Liebig - 1 st scientist to look at fertilizer, mid 1800s (19 th C) - He asked the Q: what is it really in manure that allows for crops to grow? - He did a chemical analysis & discovered that various kinds of nutrients that were needed & he was able to actually grow crops and take away some nutrients and see whether or not the crops would falter
- He came to the conclusion that there were 4 major nutrients that were needed in manure that allowed crops to grow Major ones: nitrogen, phosphorus, potassium & various other elements needed in smaller amounts - The 3 numbers on fertilizer packaging indicate the ratio nitrogen to phosphorus to potassium b/c various different kinds of plants require a different ratio o Liebig was the 1 st to figure this out BUT he was NOT adept at making novel fertilizers. He still had to rely on what nature provided Fritz Haber - Came along in the latter part of the 19 th century it was then that developments began to move quickly in the area of fertilizer - He found a way to combine nitrogen & hydrogen to make ammonia synthetically ( N 2 + 3H 2 2NH 3 ) Nitrogen is one of the most important components of any fertilizer. Up to that time,
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