The use of heavy machinery is increasing in agricultural industries in
particular cotton farming systems, which induces an increased risk of
soil compaction and yield reduction. Hence, there is a need for a
technical solution to use available tools to measure projected soil
compaction due to farm machinery traffics. The aim of this work was to
compare the effects of static and dynamic loads on soil compaction. In
this study, three vertosols (common soil for cotton production) were
selected to examine soil compaction under a range of static and dynamic
loads using uniaxial compression equipment and a modified proctor test,
respectively. In general, soils behaved similarly under static and
dynamic loads with no significant difference between bulk density values
for all moisture contents with a high index of agreement (d=0.96, RMSE=
0.056). The results further indicate better agreement between soil
compaction for static and dynamic loads Uniaxial compression test
(static loads) produced higher compaction compared to the modified
proctor test (dynamic loads) in particular at moisture contents lower
than the plastic limit condition. The variation in soil compaction for
static and loads was often evident for loads ≥600 kPa, with the highest
soil compaction induced under loads ≥1200 kPa. The findings of this
study confirm the suitability of a modified proctor method to assess
soil compaction as an alternative tool under a range of moisture
contents and machinery loads for vertosols.
No tillage (NT) and spring ridge tillage (SRT) are two common applications of conservation tillage. Although conservation tillage is known to exert major control over soil microbial respiration (SMR), the growing-season SMR response to these two applications remains elusive. In order to better understand the influence of conservation tillage practices, this experiment was conducted in an experimental field using NT and SRT for 17 years. In situ measurements of SMR, soil temperature and soil water content (SWC) were performed. Soil samples were collected to analyze soil porosity, soil microbial biomass (SMB) and soil enzymatic activities. Results show that the two conservation tillage systems had a significant difference (p<0.05) in terms of SMR; the SMR of NT was 14.7 mg•C/m 2 •h higher than that of SRT. In terms of soil temperature and soil enzymatic activities, the two treatments were not significantly different (p>0.05). Despite SRT increasing the proportion of micro-porosities and meso-porosities, the soil macro-porosities for NT were 7.37% higher than that of SRT, which resulted in higher bacteria and fungi in NT. Owing to SRT damaged the hypha, which had disadvantage in soil microbe protection. Inversely, less soil disturbance was a unique advantage in NT, which was in favor of improving soil macro-pores and SWC. Redundancy analyses (RDA) showed SMR was positively correlated with soil macro-pores, SMB and SWC. Furthermore, the Pearson correlation test indicated that SMB and soil enzymatic activities did not have a significant correlation (p>0.05). This study results suggest that SRT is more conducive to carbon sequestration compared with NT in cropland.
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