Soil Conservation

Soil Conservation Safeguarding soil from depletion or deterioration Sustainable Soil Use “A nation that destroys its soil destroys itself” Franklin D. Roosevelt, 1937

Soil Quality The capacity of a soil to sustain biological productivity and diversity, maintain environmental quality, and promote plant and animal health Anything that affects soil quality can affect sustainable use of soil

Limitations to sustainable soil use (Limitations first, then some solutions) 1. Soil Erosion 2. Salinization 3. Nutrient Removal 4. Urban Encroachment 5. Contamination / Pollution

Wind Erosion in New Zealand

Water erosion

Raindrop impact loosens soil particles-- particles can then either move down hill and knock other particles loose, or enter soil pores, plugging surface soil and encouraging more erosion

Erosion is also associated with roads, landings, wildfires… other areas with bare soil

Since 1945  11 % of earth’s vegetated surface ( area of China + India) has been degraded so badly it will be very expensive or impossible to fix. In many areas, subsistence agriculture is practiced. But once the land is eroded, the soil is ruined for farming and may be abandoned Nevertheless, populations are still increasing…. especially in areas where subsistence farming is important

It is estimated that 1/5 of the world’s topsoil has been lost since 1950!! • Bangledesh: • population increasing and urbanizing • soil degradation from ↑farming intensity • ↓SOM, ↓fertility; estimated cost of soil degradation is 7.7% of GDP (2007) US • Dust bowl of the 1930’s • China • 1/6 land area => serious erosion • Atmospheric scientists in Hawaii can tell within a few days when the spring plough starts in N. China.

Desertification: The spreading of desert conditions due to land degradation Hillel 1991

Earth's deserts and areas susceptible to desertification

Average soil formation rate: Geologic or natural erosion rate: ~.25 mm per year = 2.5 Mg ha-1 or ~ 1 ton per acre USDA tolerable soil loss per year: 11 Mg ha-1 !! or 5 tons per acre !! ~0.03 mm per year or ~ 0.3 Mg ha-1 or ~>0.1 ton per acre !!

Did you know that in Texas ~60 tons of topsoil is lost to produce 1 ton of cotton? Average annual soil erosion in the US. Erosion has declined but still exceeds the tolerable limit of 5 tons per acre per year. USDA, 1995

Predicting Soil Erosion Universal Soil Loss Equation (USLE) or Revised Universal Soil Loss Equation (RUSLE) A = RKLSCP A = metric tons of soil lost per hectare per year R = rainfall erosivity K = erodibility of soil L = length of slope S = steepness of slope C = cover type P = erosion control practices

Limitations to sustainable soil use 1. Soil Erosion 2. Salinization 3. Nutrient Removal 4. Urban Encroachment 5. Contamination / Pollution

2. Salinization Did you know ... Salt-affected soils are the 2nd largest cause of soil degradation (after erosion) ? Globally it removes about 3 hectares of land from production every minute.

The rising water table in a poorly-drained soil infuses the root zone with salts. Irrigation with water containing salts and over-fertilization lead to salinization Hillel 1991

Lake Eyre, Central Australia Murray River Basin, SE Australia

Limitations to sustainable soil use 1. Soil Erosion 2. Salinization 3. Nutrient Removal 4. Urban Encroachment 5. Contamination / Pollution

3. Nutrient Removal

Amounts of some nutrients removed by harvesting over a 50 year period compared with weathering release of nutrients in temperate areas (kg/ha)

4. Urban Encroachment For example, LAS VEGAS Las Vegas, 1972 pop. 273,000 Las Vegas, 1992 pop. 863,000 Las Vegas, 2000

5. Contamination FROM: • metals • toxic organics • over fertilization - nitrate, phosphate • solid wastes

toxicity symptoms in alder planted in mine tailings overfertilizing a lawn

Current population gain is 78 million people per year, or 214 000 /day = 8 904 /hour. It is predicted that world population will level off at about 10 Billion. In next 30 years humans will need as much food and fiber as they used in last 10 000 yrs.

Soil degradationPoverty “Soil degradation is among the fundamental causes of global unrest” Rattan Lal, 2007, President of SSSA Our challenge is to produce and distribute enough food, energy and necessities for all, without ruining the resources used to produce them.

So what do we do? Prevent damage!! Do the right thing at the right place Use the best management practices • Keep vegetation on site, • Use cover crops, • Conservation tillage, • Don't excessively fertilize, • Avoid compacting soil, • Use compost….. • Build roads sparingly and carefully e: erosion w: water s: shallow, rocky c: climate Land capability classes

What if damage is already there? Reclaim or restore soils

Repairing Soil For eroded soil: • stabilize land - prevent further erosion • establish vegetative or other cover • repair topsoil - add organic matter

For wind erosion, prevent further loss. Use windbreaks, or keep soil covered. Effect of a windbreak on wind velocity when planted perpendicular to prevaling winds. Chiras et al. 2002

For water erosion, keep soil infiltration high, control overland flow using vegetation, ditches, contour plowing etc. Decommisioning and restorating a logging road

After mining: • stabilize waste • stabilize or remove toxic metals • restablish vegetation • even better: begin restoration with mining, recontour, clean wastes, replace topsoil, plant native vegetation

Active gold mine New Zealand

With other types of contamination: • not always possible to repair- remove soil • bioremediation - microbial degradation (oil) • phytoremediation - using plants for reclamation

Restoration of mine tailings, Washington State

If soil develops salinity: • install drainage • leach slowly with clean water • may need to add Ca to displace Na If nutrient are being depleted: • replace nutrients with: • compost • organic wastes • fertilizers Urban encroachment • use zoning to protect: • floodplains, best soils, sensitive soils; reclaim soils

Soil Conservation