Contour ploughing Contour ploughing orients furrows following the
contour lines of the farmed area. Furrows move left and right to maintain a constant altitude, which reduces
runoff. Contour plowing was practiced by the ancient
Phoenicians for slopes between two and ten percent. Contour plowing can increase crop yields from 10 to 50 percent, partially as a result of greater soil retention.
Terrace farming Terracing is the practice of creating nearly level areas in a hillside area. The terraces form a series of steps each at a higher level than the previous. Terraces are protected from erosion by other soil barriers. Terraced farming is more common on small farms. This involves creating a series of flat terraced levels on a sloping field.
Keyline design Keyline design is the enhancement of contour farming, where the total watershed properties are taken into account in forming the
contour lines.
Perimeter runoff control Trees,
shrubs and
ground-cover are effective perimeter treatment for
soil erosion prevention, by impeding surface flows. A special form of this perimeter or inter-row treatment is the use of a "
grass way" that both
channels and dissipates runoff through surface friction, impeding
surface runoff and encouraging infiltration of the slowed surface water.
Windbreaks Windbreaks are sufficiently dense rows of
trees at the
windward exposure of an agricultural field subject to
wind erosion.
Evergreen species provide year-round protection; however, as long as
foliage is present in the seasons of bare
soil surfaces, the effect of
deciduous trees may be adequate.
Cover crops/crop rotation Cover crops such as
nitrogen-fixing legumes, white turnips, radishes and other species are rotated with cash crops to blanket the soil year-round and act as
green manure that replenishes nitrogen and other critical nutrients. Cover crops also help to suppress weeds. Differentiated taxation schemes are among the options investigated in the academic literature to reducing their use.
Salinity management Salinity in soil is caused by irrigating with salty water. Water then evaporates from the soil leaving the salt behind. Salt breaks down the soil structure, causing infertility and reduced growth. The
ions responsible for salination are:
sodium (Na+),
potassium (K+),
calcium (Ca2+),
magnesium (Mg2+) and
chlorine (Cl−). Salinity is estimated to affect about one third of the earth's
arable land. Soil salinity adversely affects crop
metabolism and erosion usually follows. Salinity occurs on
drylands from
overirrigation and in areas with shallow saline water tables. Over-irrigation deposits salts in upper soil layers as a byproduct of soil
infiltration; irrigation merely increases the rate of salt deposition. The best-known case of shallow
saline water table
capillary action occurred in
Egypt after the 1970 construction of the
Aswan Dam. The change in the
groundwater level led to high salt concentrations in the water table. The continuous high level of the
water table led to
soil salination. Use of
humic acids may prevent excess salination, especially given excessive irrigation. Humic acids can fix both
anions and
cations and eliminate them from
root zones. Planting species that can tolerate saline conditions can be used to lower water tables and thus reduce the rate of capillary and evaporative enrichment of surface salts. Salt-tolerant plants include
saltbush, a plant found in much of
North America and in the
Mediterranean regions of
Europe.
Soil organisms that assists in organic decay When worms excrete
feces in the form of
casts, a balanced selection of minerals and plant nutrients is made into a form accessible for
root uptake.
Earthworm casts are five times richer in available
nitrogen, seven times richer in available
phosphates and eleven times richer in available
potash than the surrounding upper of soil. The weight of casts produced may be greater than 4.5 kg per worm per year. By burrowing, the earthworm improves soil
porosity, creating channels that enhance the processes of aeration and drainage. Other important soil organisms include
nematodes,
mycorrhiza and
bacteria. A quarter of all the animal species live underground. According to the 2020
Food and Agriculture Organization’s report "State of knowledge of
soil biodiversity – Status, challenges and potentialities", there are major gaps in knowledge about biodiversity in soils. Degraded soil requires
synthetic fertilizer to produce high yields. Lacking structure increases erosion and carries nitrogen and other pollutants into rivers and streams. Flooding can bring significant
sediments to an
alluvial plain. While this effect may not be desirable if floods endanger life or if the sediment originates from productive land, this process of addition to a
floodplain is a natural process that can rejuvenate soil chemistry through mineralization. ==See also==