Tillage and Farming Systems - Soils and Soil Supplements - Lecture Slides, Slides of Biology

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Unit 12: Tillage & Farming Systems Docsity.com Objectives • Historical trends in tillage • Investigate reasons for tillage • Different types of tillage • Advantages/impacts of alternative tillage management • Role of organic farming • Uses & issues of transgenic crops Docsity.com Purposes for Tillage – Tillage incorporates crop residue • Difficult to plant through much residue – Seed may be left in residue, not in soil – Seed likely to die – Poor, erratic stand • Weed Control – Weeds compete for soil water, nutrients, light – Tillage essential to deter weeds • Especially before herbicides Docsity.com Purposes for Tillage – Today – herbicides more effective at controlling weeds than tillage • Also: – Eliminate field passes – Preserve soil moisture – Reduce damage to crop roots – Less developed countries = more hand tillage/cultivation – Farmers prefer aesthetically pleasing fields Docsity.com Purposes for Tillage • Loosening the Soil – Excessive tillage can cause extensive compaction • Plow or Tillage Pan – zone of compaction just below tillage zone • Greatly decreased infiltration rates, aeration, root penetration – Need corrective tillage to remedy, or grasslands Docsity.com Purposes for Tillage • Improving Water Relations – Break soil crusts, loosens soil, increases infiltration – Storage of even a little more water can be difference in profitable/unprofitable yields – Using subsoiler that leaves soil surface w/ little disturbance may increase water storage 3” through winter Docsity.com Purposes for Tillage • Aerating & Warming – Compacted, crusted soils have poor air exchange – Limits root growth, plant productivity – Poor microbe efficiency – Can speed temp warming, if desired (early spring planting) – Dries soil if excessively wet • What is the risk of working wet soils? Docsity.com Purposes for Tillage • Reasons to Reduce Tillage or Eliminate Tillage – Must keep food production economical for producers & consumers – Reasons to reduce tillage: • Eliminate/reduce erosion – Critical to keep topsoil in place for ag’s future – Gov’t pressure/regulation will force more conservation techniques Docsity.com Tillage Terminology • Primary tillage – first & deepest tillage operation – Loosens soil – Moldboard plow, disc, chisel plow • Secondary tillage – follow primary tillage – Disks, cultivator, harrow – Kill weeds, incorporate chemical/fertilizer – Prepare seedbed Docsity.com Tillage Terminology • Chisel – narrow shank pulled through soil to rip • Chisel plow – rips soil 6 – 12” depth • Conservation tillage – any tillage system that leaves >30% of surface covered by residue for erosion control Docsity.com Tillage Terminology • Conventional tillage – traditional moldboard plow, disc, harrow, seeding – Any tillage leaving <15% of surface covered by residue • Coulter – disk w/ straight/fluted edge for slicing open soil • Cultivator – small sweeps pulled between crop rows to kill weeds Docsity.com Reducing or Eliminating Tillage Tillage started to improve on nature’s methods of crop growth – Ability to grow more crop/land area – Option to grow a single crop in a field • Physical Properties of Soil – Any traffic increases compaction – Tillage loosens soil to depth of tillage, but increases compaction on subsoil Docsity.com Reducing or Eliminating Tillage – No-till – increases #/size of soil pores, soil protection & aggregation are improved w/ crop residue – Reduced & conservation till fields cooler & wetter in the spring • Delays planting • Reduces germination & early seedling growth Docsity.com Reducing or Eliminating Tillage – Earthworms • Improves population • Greater positive effect on soil matrix – Water infiltration – Soil aeration – Deep tillage • Still feasible to help open subsoil • Rip at 12 – 16” depth • Deep rooted crops can also help w/ compaction & reduce tillage Docsity.com Reducing or Eliminating Tillage • Pest Control – Minimal tillage increases burden of weed control on herbicides – Will increased herbicide usage delete fuel/labor savings? – Maximize crop rotation effects – No-till may decrease weed stands long term • Don’t work weed seeds into soil during tillage • Reduced ability for weed seed to germinate – They need the same seed/soil contact as crops Docsity.com Reducing or Eliminating Tillage – Increased dependence on insecticides as well • More favorable environment to harbor them • Bigger problem w/ soil insects, less opportunity to disturb their life cycle – What other risks are there if we depend more on chemicals for control of weeds/insects? Docsity.com Reducing or Eliminating Tillage • Fertilizer & Lime Applications – Reduced tillage limits ability to incorporate P, K, lime into the soil – Can result in a concentrated zone of nutrients in top 3” of soil • May be acidified by N • May cause shallow rooting Docsity.com Reducing or Eliminating Tillage • Erosion Control – Greatly decreased wind erosion w/ reduced tillage – Advances in chemical technology allows for easier use of cover crops & burndown – Slows ability of water to wash soil from surface as easily Docsity.com Farming Systems & Environmental Quality Reduced tillage increases dependence on chemical control of pests • Typically increases pesticide use 15-40% Erosion of N, P and pesticides increased w/ reduced tillage • Due to zone of accumulation nearer soil surface than conventional tillage Tillage itself is erosive Docsity.com Farming Systems & Environmental Quality • Carbon Sequestering – putting C back into the soil • Driven by global warming theory – Elevated levels of CO2 • Soil used to/can be source of atmospheric C – w/ reduced tillage, becomes a recipient of atmospheric C Docsity.com Transgenic Crops – Bt Cotton • Cotton resistant to the very damaging bollworm • Insecticides often kill both damaging & beneficial insects – Bt Corn • Bacillus thuringensis – protein that is toxic to the corn borer • Pollen from Bt corn found to be lethal to monarch butterflies – Should it remain approved for use? Why? Docsity.com Transgenic Crops • Risks Associated w/ GMO’s – Potential for herbicide resistant plant or pollen to develop – Difficulty controlling escape of GMO pollen – Consumer concern over GMO grain entering human food system – Much debate over safety – no known health risks to humans or animals Docsity.com Transgenic Crops • Present Status & Trends – Most countries approve planting of GMO crops – Very little used in Japan, China, Europe – Government concerns • Backlash from religious & environmental groups – Company risks • Fear gov’t’s inability to enforce contracts • Loss of their technology to competition Docsity.com Sustainable Agriculture & Organic Farming • Objectives of Organic Farming – Avoid inputs of synthetic substances – Produce healthy foods untainted by unnatural substances – Strategies: • Use of manure & legumes for plant nutrients • Tillage, crop rotation, manual labor for weed control • Natural suppressants, repellants, & predators for insect & disease control Docsity.com Sustainable Agriculture & Organic Farming • Mixed Reviews for Organic Farming – Clearly less environmental problems • Although may increase N loss to groundwater – Some decrease in energy use – Food quality superiority unfounded – 20-45% reduction in yields (European study) • Increased demand for land, w/ decreased output/ac Docsity.com Sustainable Agriculture & Organic Farming • Organic Food Marketing – Sales increasing sharply (especially in wealthy countries) – Fastest growing sector of world agriculture – Large export market for countries w/ highest % organic farming (Asia, Australia, Latin America) • Ironic because of amount of fuel needed for transportation Docsity.com Sustainable Agriculture & Organic Farming – Four levels of organic labeling • 100% organic – seal on package • 95-100% organic – seal on package • 70-95% organic – can claim organic, but no seal • <70% organic – can list organic ingredients, no organic claim or labeling Docsity.com Assignment Docsity.com