Effects of tillage measures on soil loss
Both Hr and Cm could alleviate soil erosion, mainly by improving the
microtopography to increase soil
surface roughness (Rodríguez-Caballero et al., 2012; Vermang et al.,
2015), and improve soil physico-chemical properties. Moreover, Vr should
be circumvented as it augments both soil loss rate and amount (Kader et
al., 2017; Mulumba & Lal, 2008).
When there was no ridge rupture during the rainfall, Hr effectively
reduced sediment yield and soil loss rate, as shown in previous studies
(García-Orenes et al., 2012). However, after ridge rupture, the impacts
on sediment loss were much more severe than on runoff,
e.g., the runoff rate was amplified
22.6 times compared to its neighboring point, while the sediment loss
rate was amplified 94.7 times after ridge rupture occurred in Hr under a
rainfall intensity of 100 mm h-1. This outcome may
have occurred because the broken ridges, which were normally big soil
blocks, were prone to being
directly swept and, thus, lost via
runoff (Xu et al., 2018). The residual ridge remaining to be washed
continuously by runoff would also increase the sediment concentration in
runoff after the ridge rupture, leading to a higher soil loss rate. Soil
loss would be further amplified if ridge rupture occurred in the top
section of the plot and thus likely triggered successive ruptures.
Our study found that Cm was more
reliable than Hr in controlling soil loss (Kader et al., 2017;
Prosdocimi et al., 2016b), as it could restrict both the sediment yield
and soil loss rate to very low levels (García-Orenes et al., 2012). The
reason might be that the flow could accumulate sufficient power to
detach and transport particles with mulching (Mannering & Meyer, 1963;
Poesen & Lavee, 1991). In addition, Cm could postpone the soil loss
rate that increasingly responded to rainfall intensity enhancement,
which is an important effect on soil erosion because
rainfall has a short duration but
high intensity during the maize seeding stage in Northeastern China (Sun
et al., 2000; Zhang et al., 2010). This postponing effect would
counteract or even eliminate the instantaneous serious destruction due
to torrential rain. Hence, Hr+Cm significantly prevented soil loss,
especially under light rainfall intensity conditions, and thus, in
practice, should be suggested to reduce soil erosion.