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Introduction
Soil salinity and sodicity, either individually or collectively are
D gOobDO SrobOeP Sosing significDnt threDts to the sXstDinDbOe
development of agriculture, in particular in the arid and
semiarid regions of the World.
A typical example of the problems caused by salinity and
sodicity can be readily found in Xinjiang, a typical arid region
oI 1orthZest &hinD Zhere sDOinizDtion Dnd sodificDtion oI
soils have been causing serious land degradation issues
for many years. It is estimated that one third of the arable
land of the region is affected, greatly reducing agricultural
output in the area.
The salinity problems of Xinjiang are exacerbated by the
region’s inland arid conditions and water resource shortages.
Under saline conditions, the reduced growth of crops is
caused by the effect of the osmosis, which greatly increases
clay dispersion and reduces aggregate stability, resulting
in D decOine in Dir SerPeDbiOity infiOtrDtion Dnd hydrDXOic
conductivity.
These factors will inevitably hinder root respiration, reducing
plant growth and activity of soil organisms.
Drip irrigation, thanks to its characteristic of applying water
at a low discharge rate and high frequency over a long
period of time provides consistent soil water levels in the
root zone, reducing salinity levels in soil water by leaching,
particularly in the region of drip emitters.
As a result of these factors, drip irrigation scheduling has
consistently been proven to be highly important in salt
OeDching eIficienc Zith SreYioXs reseDrch hDYing confirPed
its impact on different levels of soil matric potential (SMP)
to trigger drip irrigation in arid and semiarid regions
Previous studies on the subject have focussed in particular
on the damaging effects of soil salinity, sodicity and soil
hydraulic properties, with particular emphasis on improving
levels of soil salt movement and plant health.
Correspondingly, a limited number of studies have been
carried in an effort to gain a deeper understanding of the
actions of soil nutrients during the reclamation process
under drip irrigation.
It is generally understood that soil structure and root activity
decline with increasing sodicity in a saline-sodic soil, in the
process reducing nutrient mobilities and leading to nutrient
deficiencies OeDYing orgDnic PDtter Dnd PinerDO nXtrients
in saline-sodic soils are generally at low levels.
The objectives of this study were held in Xinjiang with the
following aims:
• To investigate the effects of drip irrigation triggered
by different SMP thresholds on the distribution of soil
mineral nutrients (inorganic N, available P and K);
• To measure the effects of different SMP thresholds
on soil carbon-to-nitrogen (C:N) ratio and seed cotton
yield during three years of land reclamation under drip
irrigation.
Materials and methods
7he fieOd e[SeriPents Zere condXcted oYer the sSDce oI
three years on a saline wasteland located in the middle
of the Jungger Basin situated in the Xinjiang Province,
Northwest China.
The area has a typical inland arid climate with annual
precipitation of about 105 mm, mainly concentrated in the
summer months, while the average depth to groundwater
Effects of different drip irrigation
regimes on cotton yield
in the saline–sodic soils
of Northwest China
Soil salinity and sodicity, either
individually or collectively are a
global problem posing significant
threats to the sustainable
development of agriculture