Although understood differently in different parts of the world, conservation tillage usually includes leaving crop residues on the soil surface to reduce tillage. Through a global review of long-term conservation tillage research, this paper discusses the long-term effect of conservation tillage on sustainable land use, nutrient availability and crop yield response. Research has shown several potential benefits associated with conservation tillage, such as potential carbon sequestration, nutrient availability, and yield response. This research would provide a better perspective of the role of soil conservation tillage and hold promise in promoting application of practical technologies for dryland farming systems in China
Conservation tillage generally refers to “methods of tillage that maintain a cover of crop residues on
the soil surface and either reduce the amount of tilling (reduced tillage or minimal tillage) or eliminate
it altogether (no-till)’’ (Acton and Gregorich, 1995). However, due to regional, technical, economical
and institutional differences, the term “conservation tillage” is understood differently in various parts
of the world. The US Conservation Technology Information Center developed the first widely accepted
definition of conservation tillage as “any tillage and planting system that covers at least 30 percent of
the soil surface with crop residue, after planting, in order to reduce soil erosion by water” (CTIC, 1999).
Mannering and Fenster (1983) suggested that “a common characteristic of any conservation tillage is
its potential to reduce soil and water loss relative to conventional tillage”. Conservation agriculture
in Europe refers to “several practices, which permit the management of the soil for agrarian uses,
altering its composition, structure and natural biodiversity as little as possible and defending it from
degradation processes (such as soil erosion and compaction) and generally it includes any practice, which
reduces, changes or eliminates soil tillage and avoids residue burning to maintain enough surface residue
throughout the year” (ECAF, 1999).
Thus, conservation tillage may be interpreted as “any system that promotes good crop yields while at
the same time maintaining soil fertility, minimizing soil and nutrient loss, and saving energy/fuel inputs”.
For example, in Scandinavia conservation tillage normally involves some form of reduced tillage, which
covers alternatives ranging from systems that include thorough stubble cultivation in autumn followedby harrowing in spring to direct drilling systems with no cultivation at all prior to sowing (Riley et
al., 1994). Concerning the different climate conditions, soil types and cropping systems, conservation
tillage does not necessarily mean less tillage; rather it needs to be suited to local agroecosystems in both
space and time (Carter, 1994), where it serves to reduce soil and water loss as well as conserve natural
resources relative to conventional tillage. A broad definition of conservation tillage given by Wittmus et
al. (1973), namely “conservation tillage includes tillage systems that create as good an environment as
possible for the growing crop and that optimize the conservation of soil and water resources, consistent
with sound economic practices,” seems to be well recognized and accepted.
This research, then, is aimed at gaining an improved understanding of the long-term impacts of
conservation tillage practices on sustainable land use, nutrient availability and yield response through
a global review of long-term conservation tillage research. This would provide a better perception of
the role of soil conservation tillage and may promote application of practical technologies for dryland
farming systems in China.
