Agricultural Soils

1. Agricultural Soils October 3, 2012

2. Computer Lab Question • Schedule • Group A: Oct 5 • Group AA: Oct 12 • Group AAA: Oct 19 • Hourly Exam # 2: Oct 24

3. Computer Lab Answer • Schedule • Group A: Oct 5 – optional, but must sign up & make up one of the following days/times: • Oct 12, 4:30 – 5:20 • Oct 19, 4:30 – 5:20 • Group AA: Oct 12 (as scheduled, 3:30 – 4:20) • Group AAA: Oct 19 (as scheduled, 3:30 – 4:20) • If there are openings people in groups AA & AAA may attend one of the later labs

4. Dr. Whitford, Pesticides • Farm chemical inputs • Fuel • Pesticides • Fertilizer and manure • Oil, antifreeze and the like • We need to protect water and soil • It matters, because • Protect property values • Potential legal issues • Avoid regulatory fines • Protect the environment (humans, domestic animals, wildlife, plants)

5. Pesticide Management • Put all products in the right place • Follow the product (from delivery to use): think about how the product is transported and used • Conduct inspections, follow proper maintenance

6. Last Wednesday Lecture • Re: articles we read & reported on in class • Answers in the PPT (“More About Soils.pptx) • The Fate of our Nation's Soil Resource • World Food Prize Digs Deep for Hunger Relief Conservation Practices Help Correct Erosion Issues & New Conservation Program Protects Most Highly Erodible Croplands • No-till Practices Open Mississippi Hills to Crop Production & Gullies in Long-term No-till Fields can be Troublesome

7. SoilWeb – WSS App • New, free smartphone App • Gives users access soil survey information on iPhones and Androids • Combines online soil survey information with the GPS capabilities of smartphones • Particularly useful for those working in the field • Article: Smartphone app offers access to soil information

8. Soil Testing After a Dry Growing Season Illinois Ag Connection, www.croplife.com • Yield is the most important factor impacting P and K removal rates • Grain yields and nutrient removal levels are lower than normal due to the drought • Some fields were been baled or harvested for silage • Soil testing for P, K, and pH is used to determine the need for fertilization or limestone applications. • Corn and soybean return approximately one-fourth to one-third of the total P taken up, and about two-thirds of the total K taken up, to the soil. • It is not safe to assume that lower removal rates and lower yields will result in greater P and K levels in the soil this year • Drought limits the equilibration of nutrients in the soil • Plants have extracted P and K during the growing season • The soil has not been able to replenish those nutrients as well as in normal year

9. Soil Testing • Certified commercial laboratories offer plant and soil testing analysis services for growers in Indiana • Purdue Agronomy list: www.ag.purdue.edu/agry/extension/Pages/soil-testing-labs.aspx

10. Biology of Soil Compaction Hoorman, Carlos de MoraesSá, and Reeder, Crops & Soils magazine, July-August, 2011 • Soil compaction – soil particles are pressed together, limiting the space for air and water • Soil compaction can reduce farm yields and profits • Factors that contribute to compaction: • Farm machinery weight and traffic • Rain • Tillage

11. Biology of Soil Compaction • Results of Soil Compaction • Restricted root growth • Poor root zone aeration • Poor drainage, which causes • Less oxygen in the root zone • Increased loss of nitrogen (from denitrification)

12. Biology of Soil Compaction • Sub soil tillage to break up a compacted layer • Expensive, requires: fuel, labor, equipment and time • Used to reduce compaction and related problems (lack of water infiltration and aeration) • Soil is generally disturbed 12-18 inches deep • Additional compaction can occur if the soil is subsoiled when wet

13. Biology of Soil Compaction • Usually helps but effects are often temporary unless management changes • Re-compaction of soil is caused by • Equipment traffic • Rainfall, especially heavy rains • Gravity • Low organic matter (OM) which makes soil more susceptible to compaction

14. Biology of Soil Compaction • Organic Matter • Organic residues on the soil surface cushion the soil from compaction because they can be compressed and regain their shape • OM that is attached to soil particles (esp. clay) reduces soil compacting • OM binds microaggregates and macroaggregates in soil (macroaggreates improve soil tilth) • Excessive traffic will break up organic residues

15. Biology of Soil Compaction • Tillage has decreased soil organic levels and therefor soil organic carbon by 60% in the last hundred years • Carbon provides energy for soil microbes, stores nutrients, and recycles nutrients in the soil • Humus (old carbon, >1,000 years old) is the most stable carbon, and binds soil microparticles together to form microaggregates • Humus is not water soluble • Stabilizes microaggregates • Not readily consumed by microorganisms • More resistant to tillage and degradation than active carbon

16. Biology of Soil Compaction • Active Carbon • Plant sugars, polysaccharides, and glomalin • Consumed by microbes for energy • Reduced with tillage • Stabilized under natural vegetation and no-till systems using a continuous living cover • Part of the “glue” that binds microaggregates into macroaggregates • Macroaggregationimproves soil structure and lowers bulk density (helping to keep soils from compacting)

17. Biology of Soil Compaction • What is a clod? • Made by humans – do not exist in the natural world • Tilling exposes clay to sunlight, heating and drying • Clods are formed… just like bricks and clay tile are formed by heating and drying wet clay • Moisture and organic residues keep clay particles from chemically binding by keeping clay particles physically apart

18. Biology of Soil Compaction • A continuous living soil cover plus continuous long-term no-till protects the soil from compaction, because: • Covered soil surface acts like a sponge to help absorb the weight of heavy equipment traffic • Plant roots create voids and macropores in the soil that allow air and water movement • Plant roots supply food for microorganisms (esp. fungi) • Organic residues (from decaying plants, animals, microbes) are lighter and less dense • Aids in combining microaggregates into macroaggregates which improves soil structure

19. Ways to Evaluate, Avoid Compaction Fyksen, AgriView.com • The amount of soil water present is a critical factor in soil compaction potential. • Spring is the best time of the year to measure soil compaction when the whole profile has usually been thoroughly moistened during the winter. • If the soil is too wet and muddy, compaction could be underestimated because the soil water acts as a lubricant. • If the soil is too dry, compaction could be overestimated because roots will be able to penetrate the soil when it re-wets.

20. Ways to Evaluate, Avoid Compaction • Check for soil compaction • Shovel – look for surface crust or platy soil structure • Soil probe – insert slowly, feeling for increased resistance • Soil pentrometer – push in (1 inch/sec.); resistance > 250-300 psi in moist soil is root-limiting

21. Ways to Evaluate, Avoid Compaction • Shallow, Surface Soil Compaction • Related to pressure on the soil surface • Normally removed by tillage operations • May be removed by freeze-thaw and wet-dry cycles • Control: • Better load distribution (larger tire size or more tires) • GPS can help maintain controlled traffic • Conventional or reduced tillage systems: avoid during planting • No-till system: avoid at all times

22. Ways to Evaluate, Avoid Compaction • Sub-surface Compaction • Related to maximum axle load • Will not be reduced by distributing equipment weight • Can only be avoided by limiting traffic with heavy axle loads • A maximum axle load of 10 tons is recommended • Note: a 1,000-bu grain cart can weigh more than 36 tons • Low-inflation tires with a large footprint (use minimum allowable tire pressure) may help

23. Ways to Evaluate, Avoid Compaction • Sidewall Compaction • Caused by planting when soil is too wet • Planter openers push on the side of the soil furrow, creating a compacted zone • Avoid by not planting when the soil is too wet* • Spoke wheel seed slot closers can be helpful • *Testing for moisture content – how?

24. Ways to Evaluate, Avoid Compaction • Fall-Planted Cover Crops • Provide support for livestock and/or manure spreaders over winter • Plant cover crops right after harvest of annual crops to keep living roots in the soil year-round • Sjoerd Duiker (quoted for this article): • “Living root systems are probably the best protection against compaction.” • “Avoiding compaction is a lot more cost-effective than causing it and then having to repair it.”

25. Ways to Evaluate, Avoid Compaction • Sjoerd Duiker: The Basics of Soil Compaction: • Use no-till to help your soil resist and bounce back from compaction • Increased organic matter accumulation at the soil surface • Permanent burrows of old root channels and prolific activity of earthworms and fungi in permanent no-till fields also helps make the soil resist compaction • Biological organisms also help alleviate compaction after it has been caused • Avoid causing compaction • Remediate compaction only if needed

26. Herbicide-resistant Weeds Threaten Soil Conservation Gains CAST* staff, Feb. 6, 2012 • The Flip Side: Herbicides & Conservation Tillage • Herbicides were developed for weed control (conventional tillage) • Highly effective herbicides and herbicide-resistant crops (e.g., glyphosate) allowed the development of conservation tillage and less soil damage • When any single herbicide mechanism is used repeatedly without alternative management, selection pressure becomes intense for plants that can tolerate the herbicide • Several weed species exhibit resistance to glyphosate and many are resistant to other herbicide mechanisms *CAST ~ Council for Ag Science and Technology (www.cast-science.org/)

27. Herbicide-resistant Weeds Threaten Soil Conservation Gains • Mitigating the impact of herbicide-resistant weeds • A diversity of strategies is necessary • Alternative tillage, including mechanical • Alternative herbicides • Crop rotation (depending on the crops and management practices used)