topic8 - BIOL 1030 TOPIC 8 LECTURE NOTES Topic 8: Plant...

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BIOL 1030 – TOPIC 8 LECTURE NOTES Topic 8: Plant Nutrition (Chs. 36 and 37) I. PLANT NUTRIENTS A. nutrition overview 1. there are nutrients that plants must obtain from their environment 2. most nutrients are obtained from the soil 3. cultivation and fertilization practices affect soil quality 4. some plants have adaptations to aid survival in areas with nutrient limitations B. two classes: macronutrients (lots needed) and micronutrients C. listed as elements, but some elements must be in certain forms to be used (example: N works as NO 3 - or NH 4 + , not as N 2 ) D. macronutrients 1. 9 of them: C, O, H, N, K, Ca, Mg, P, S 2. each usually about 1% or more of dry weight 3. most abundant C, O (each 44% dry weight), H (6% dry weight) 4. nitrogen (N) is usually the most limiting factor (plants need lots of it, and in particular forms) E. micronutrients 1. 7 of them: Cl, Fe, Mn, Zn, B, Cu, Mo 2. needs range from one to several hundred parts per million 3. micronutrient needs so small they can be hard to study F. studies of nutrient deficiencies have revealed diagnostic symptoms (can be used to recommend treatments) II. SOIL A. natural soil is formed by the breakdown of rocks (weathering of Earth’s outer crust) B. rocks consist of many different minerals (inorganic compounds of elements) C. weathering includes physical and biological processes D. mineral particles 1. variety of sizes 2. in most soils, the most abundant particles range from coarse sand with visible particles (up to 2 mm diameter) to clay with very small particles (2 μ m or less) E. soil may also have humus – decaying organic material F. topsoil – a mixture of mineral particles, living organisms, and humus 1. where most roots are (some go deeper) 2. erosion = loss of topsoil may deprive plants of proper nutrients may deprive plants of consistent water supply may alter downstream environments G. about half of soil volume spaces or pores, which may have water H. water in soil 1. clay holds water very well (electrostatic attraction), often too well 2. sand allows rapid drainage 3. best soils typically a mix (called loams ) III. CULTIVATION AND FERTILIZATION A. natural processes to replace nutrients include decomposition, nitrogen fixation, fire B. sometimes, plants deplete the nutrients much faster than they can be replaced C. loss of fertility is a common problem with farms (nutrients leave when plants harvested) D. farming practices to keep or replenish soil fertility 1. crop rotation – alternating two or more crops that complement each other in nutrient usage and replenishment (example: alternate soybeans, which harbor nitrogen-fixing bacteria, with other crops) 2. plow under plant material – only remove what you need at harvest 3. leave fields “fallow” and plow under what grows
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topic8 - BIOL 1030 TOPIC 8 LECTURE NOTES Topic 8: Plant...

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