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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Winter 2001 S SS SS oils are a living and breathing community of worms, plants, and billions of microorganisms. Like most living things, microorganisms require oxygen and water to survive. Some microorganisms digest residue, producing organic matter. Other bacteria break down organic matter into nutrients that feed crops. Compaction can severely reduce this activity. Without these billions of microorganisms, soil can become a lifeless piece of concrete. During compaction, soil aggregates and soil particles are crushed and packed closer together, squeezing out pore space (Figure 1). Instead of the ideal pore space of 50 percent, compacted soils may show only 30 percent pore space. The first pores to be lost are the large ones that carry air and water when the soil is wet. As the large pores collapse, smaller, less efficient pores are formed. Water penetrates at a slower rate. Drainage and aeration are reduced. Root growth is limited and so is nutrient uptake. Uncompacted soils (left, Figure 2) have adequate space for oxygen to enter and carbon dioxide to exit. Oxygen is necessary for the uptake of nutrients like phosphorus and nitrogen. Bacteria need oxygen to digest residue and organic matter. As the digestion process takes place, carbon dioxide is released. Since carbon dioxide is toxic to root systems, it needs to be eliminated from the soil. The highly compacted soil on the right in Figure 2 has reduced water- holding capacity. The soil is tight and drainage is restricted. Compacting soil is like squeezing a wet sponge. Porosity is decreased and the sponge becomes useless. Reducting Soil Compaction In Reduced-till Fields Compaction is our biggest enemy in reaching yield goals. Densely compacted soils have little space for roots, soil organisms, water or air. Visual symptoms: plants Purple/stunted corn. This can be mistaken as a symptom of other FFF Review Uncompacted Compacted (white space is air, light blue is moisture, brown is soil) Uncompacted Compacted O (air) 2 O (air) 2 CO2 CO2 Figure 2. Effect of compaction on aeration. Figure 1. Effect of compaction on page space.
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