13and keeping the soil covered with crop residues were developed and the term conser-
vation tillage was introduced to reflect such practices aimed at soil protection. As
discussed above, concepts for reducing tillage and keeping soil covered were devel-
oped and the term conservation tillage was introduced to reflect such practices aimed
at soil protection. Unger ( 2006 ) stated that conservation tillage is any combination of
tillage and planting practices that generally reduces the loss of soil and water relative
to losses with conventional tillage. McCarthy et al. ( 1993 ) reported that conservation
tillage is any tillage/planting system which leaves at least 30 percent of the field sur-
face covered with crop residue after planting has been completed, and that this
amount of cover will reduce erosion by at least 50 percent compared to bare, fallow
soil.
In dryland farming areas, even when no-tillage is used between crops, there are
often sufficient crop residues remaining after planting the next crop to cover 30 %
of the soil surface. This is particularly true when only one crop is produced every
two years, or two crops every three years, that result in long fallow periods between
crops. As a result, current definitions of conservation tillage often do not include the
30 % minimum cover requirement. For example, CTIC ( 2015 ) states “conservation
tillage is a system of crop production with little, if any, tillage. It increases the resi-
due from the crop that remains in the field after harvest through planting. This
results in increased natural recycling of crop residues.” The emphasis is on leaving
Fig. 4 Mean annual temperature and precipitation for various locations and temperature/precipi-
tation as and “index” indicating the difficulty of developing a sustainable agriculture system
(Stewart et al. 1991 )
Dryland Farming: Concept, Origin and Brief History