4.1. Effects of conservation tillage methods on winter
wheat
Averaged across all locations, conservation tillage methods overall
increased winter wheat PSE, SWSp, grain yield, ET and WUE by 22.6%,
17.8%, 24.1%, 6.5% and 12.1%, respectively (P ≤ 0.05 Figure
2) which corresponds to a recent meta-analysis by Adil et al. (2022)
that described the positive effects of conservation tillage methods and
fallow mulching in dry lad cropping systems, and also to the results
obtained by Li et al., (2007) who described that conservation tillage
methods are effective in increasing soil water storage and crop yield.
The positive effect of conservation tillage methods on soil water
storage compared to conventional tillage clearly confirmed our
1st hypothesis that conservation tillage methods will
improve soil water storage during fallow period which is probably due to
the reduced soil disturbance, reduced soil bulk density and improved
aggregate stability by NT (Oyedeleet al., 1999; Zhang et al., 2007).
Similarly, conservation tillage methods are effective conservation
tillage methods (Li et al., 2007; He et al., 2009) that reduced the soil
compaction, improved soil structure which eventually increased yield and
WUE (Pikul Jr and Aase, 1999; Pikul and Aase, 2003). Moreover, previous
studies in Chinese Loess Plateau also reported higher water content and
yield with conservation tillage methods during fallow period compared to
CT (Liang et al., 2002; Wang et al., 2003) and is consistent with the
results of current meta-analysis that also corresponds to the previous
studies conducted in other areas including Victoria (Australia),
Nebraska (USA) (Lyon et al., 1998; Cantero-Martinez et al., 1999), and
Texas (USA) (Baumhardt and Jones, 2002), Great Plains of the Northern
USA (Lenssen et al., 2007), semi-arid Kenya (Gicheru et al., 2004).
In our study, RT increased wheat PSE by 25.1% compared to CT and this
effect was slightly more than that of ST (23.9% increase compared to
CT) (Figure 2). ST had good results than CT may be due to the deep
loosening of the soil which resulted in better infiltration and the
breaching up of the permanency of flow paths in the soil (Hillel, 1998).
Although, NT increased PSE by 10.9% compared to CT (Figure 2), which is
in accordance with (Halvorson et al., 2000) who described the effect of
NT and CT under dry conditions. In our study, 24.1% increase IN wheat
yield was obtained with NT compared to CT and the similar results were
obtained by Jin et al. ( 2007) who described that after 6 years of
experiment, NT showed highest yield by improving soil physical and
chemical properties and stabilizing the bulk density of soil after 5
years of NT practice (Fabrizziet al., 2005).