27
Dnd nXtrients Zere significDntOy DIIected by the soiO PDtric
potential thresholds under drip irrigation.
With the reclamation in both soil chemical and physical
properties, there were dramatic increases in soil N, P and
K concentration by the end of 3 years of the experiment.
The soil concentration of inorganic and total N, available P
and K was proportional to the SMP thresholds, as higher
603 resXOted in Pore eIficient soiO recODPDtion
2YerDOO considering the soiO recODPDtion eIficiency soiO
nutrient stocks and cotton yield, SMP thresholds of -5 and
-10 kPa were deemed the most effective to be used to
gDXge Ds eIIectiYe PeDsXres to trigger irrigDtion in the first
three years of saline-sodic soil reclamation in Xinjiang,
Northwest China.
Soil carbon-to-nitrogen (C:N) ratio was observed to be one
oI the Ney IDctors inÁXencing soiO orgDnic PDtter (SOM)
decomposition, with relatively high C:N ratio liable to result
in the competition for nitrogen meaning an adverse impact
on crop yields.
In saline-sodic soil, the sum of the osmotic and matric
stresses was seen to limit crop yields, while the amount of
applied N, P and K taken up by the crop and the amount
of C produced by the crop in the form of roots and foliage
was seen to increase. ■
Table Three: Irrigation treatments and amount
of applied water for each treatment during the
e[perimental stages in years one two and three
Year Treatments
Fresh
water for
seedlings
(mm)
During treatment
Irrigation
Times
Water
depth
(mm)
Year
One
S1 (-5kPa) 40 68 666
S2 (-10kPa) 40 47 460
S3 (-15kPa) 40 30 293
S4 (-20kPa) 40 28 274
S5 (-25kPa) 40 26 254
Year
Two
S1 (-5kPa) 40 65 636
S2 (-10kPa) 40 47 460
S3 (-15kPa) 40 38 372
S4 (-20kPa) 40 37 362
S5 (-25kPa) 40 25 244
Year
Three
S1 (-5kPa) 40 65 627
S2 (-10kPa) 40 56 541
S3 (-15kPa) 40 38 363
S4 (-20kPa) 40 28 274
S5 (-25kPa) 40 24 235
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