Principles of Soil Management - Principles of Sustainable Soil Management in Agroecosystems - page 10

MRT or turnover rate of SOC by altering its accessibility to microbes (Dungait et
al. 2012). An objective of soil management is to moderate/control the accessibility
of SOC to soil biota.
Conservation agriculture or no-till (NT) farming, adopted in conjunction with cover
cropping and integrated nutrient management (INM), is another strategic option of
enhancing the SOC pool in the surface layer, reducing risks of soil erosion, and sustain-
ing productivity. Toliver et al. (2012) compared agronomic yields from 442 paired till-
age experiments across the United States. They observed that mean yields of sorghum
( Sorghum bicolor ) and wheat ( Triticum aestivum ) were higher with NT than plow tillage
(PT). Further, there was a trend of similar or more yield with NT than PT for crops
grown on loamy soils in the Southern Seaboard and Mississippi Portal regions. In con-
trast, NT performed poorly on sandy soils except for cotton ( Gossipium hirsutum ) and
corn ( Zea mays ). Toliver and colleagues concluded that soil and climatic factors impact
NT yields relative to PT. Another principal advantage of NT farming is the reduction in
diesel consumption for plowing. Labreuche et al. (2011) observed from long-term experi-
ments at Biogneville in the Paris basin (France) that diesel consumption was reduced by
28 L/ha with conversion from PT to reduced tillage and by 41 L/ha with conversion to
NT, reducing total energy consumption by 6%-11%. Further, the magnitude of savings
of diesel can be double this in heavy-textured (clayey) soils with a large draft power.
Considering higher NT 2 O emissions and more SOC storage in NT than PT, Labreuche et
al. (2011) estimated a decrease of 200 kg/ha/year of CO 2 equivalent with conversion from
PT to NT farming.
Grazing management is another important factor affecting soil quality. Over and
above the effects of grazing on the SOC pool and soil quality as discussed above
(du Preez et al. 2011a,b), grazing induces alterations in several parameters. In South
Africa, Keay-Bright and Boardman (2007) observed that high stock numbers and
less benign management practices in the nineteenth century and early twentieth cen-
tury underlie much of the degradation observed today. In Burkina-Faso, Savadogo
et al. (2007) observed that heavy grazing reduced the aboveground biomass and
vegetation cover and decreased water infiltrability because of the trampling pressure
(static load) exerted by the animals. Further, even the prescribed fire reduced the
soil water infiltration rate: 42.2 ± 27.5 mm/h in burnt areas versus 78 ± 70.5 mm/h
in unburnt areas. The adverse effects of overgrazing on soil quality are also docu-
mented by Mekuria et al. (2007) for the Tigray region of Ethiopia. Mekuria and
colleagues observed that exclosures of grazing are effective not only in restoring
vegetation but also in improving SOC concentration and nutrient status and reducing
the erosion hazard. Conversion of grazing areas to exclosures for an extended period
can restore the quality of degraded soils.
Thus, conversion to a restorative land use and adoption of BMPs can restore degraded/
desertified soils and advance sustainable management of soil and water resources.
1.5 PRINCIPLES OF SOIL MANAGEMENT
Assessing fertilizer/nutrient requirements for increasing crop yields has been a major
challenge ever since the Industrial Revolution of around 1750. Synthesis of a vast
amount of literature on sustainable management of soil would indicate several basic