Effects of crop residue managements and tillage practices on variations of soil penetration resistance in sloping farmland of Mollisols

Soil penetration resistance(SPR)is one of the major indicators of soil physical properties.Crop residue managements,tillage practices and their interactions exert significant effects on the SPR.However,rare information is available in the sloping farmland of Mollisols.Field experiments were conducted to investigate the variations of the SPR as affected by crop residue managements and tillage practices on the sloping land in Northeast China from 2015 to 2019.The split-plot experiment was arranged with two crop residue managements(removed,REM and retained,RET),and three tillage practices(no tillage,NT;rotary tillage,RT;plow tillage,PT).SPR data in 0-80 cm soil depth was measured at the end of harvest of maize monoculture.Results showed that the two crop residue managements induced significant variations in the SPR at 0-15 cm,15-30 cm and 0-80 cm soil depths under NT,RT,and PT treatments,respectively.In comparison with RET treatment,the average values of the SPR under REM treatment were 10.9%and 8.9%higher in 45-60 cm and 60-80 cm soil depths,respectively.The average values of the SPR under PT treatment were 12.4%and 14.1%lower in 0-15 cm soil depth,and 23.9%and 10.4%lower in 15-30 cm soil depth than those under NT and RT treatments.However,the average value of the SPR under PT treatment was 11.2%and 22.0%higher in 60-80 cm soil depth than those under NT and RT treatments,respectively.The SPR generally decreased with the slope position declined in the deeper soil depth(except for the NT+RET treatment).The findings from this research can provide a scientific reference for the establishment of rational cultivation and the sustainable development of productivity on the sloping land of Mollisols in cold regions.

Effects of soil compaction on growth variables in Cappadocian maple(Acer cappadocicum) seedlings

This study investigates the effects of increasing soil penetration resistance(SPR) on seedling morphology and seedling architecture. When seedlings of deciduous Cappadocian maple(Acer cappadocicum Gled.) were grown in a greenhouse in a loamy soil under a wide range of soil compactions, all morphological variables studied changed significantly with increasing SPR. The relationships between increasing SPR and all morphological responses except lateral root length followed a negative quadratic curve. All biomass variables except lateral root biomass showed a bell-shaped response with respect to SPR, with a maximum biomass variable between 0.6 and1.2 MPa, decreasing at higher soil compaction values. All allocation ratios were significantly affected by soil penetration resistance. Biomass allocation to roots was also affected by soil compaction. There was not a significant relationship between the specific stem length and increasing soil penetration resistance. The specific root length showed two trends to increasing SPR; it first decreased in response to the moderate compaction treatment(up to about 1.2 MPa), then increased significantly. We concluded that increasing soil compaction caused morphological changes to root and shoot sections of A.cappadocicum seedlings.

Retention of eucalyptus harvest residues reduces soil compaction caused by deep subsoiling

Eucalyptus harvesting,forwarding and soil tillage operations are among the main causes for compaction of forest soils,with potential impacts on productivity.This concern is especially important in areas with soils that are naturally compacted(fragipans and duripans).In these soils,tillage operations include the use of subsoilers that can reach depths of more than one meter and require heavy tractors that exert high pressure on the soil.One of the ways to try to minimize the effect of this compaction is by retaining harvest residues.The objective of this study was to evaluate the impacts of eucalyptus harvesting on soil physical attributes,as well as to determine the potential of different types of residue management to reduce compaction from the soil tillage operation.Two experiments were conducted in the same area with a Yellow Argisol.In the first experiment,compaction caused by mechanized harvesting with harvester+forwarder was evaluated.In the second experiment,different managements of harvest residues were examined as potential modifiers of soil compaction during tillage for new plantings.For this,three managements systems were tested:(1)retention of all harvest residues and litter from the previous rotation(HR+L),(2)retention of litter from the previous rotation(L),and(3)removal of harvest residues and litter from the previous rotation(WR).Before and after harvest,sampling was carried out in the planting rows and inter-rows,and after tillage,samples were collected in the traffic line of the subsoiler-tractor set.In both experiments,undisturbed soil samples were collected from the center of the 0-10,10-20,20-40,40-60,and 60-100 cm layers to determine soil density and total porosity.In each period and site of evaluation,mechanical resistance to penetration up to the 60-cm depth was also determined.The harvesting operation increased soil density at 0-10 and 60-100 cm depths only in the inter-rows.Retention of harvest residues and litter(HR+L)after harvesting avoided increases in soil density and penetration resistance caused by machine traffic during tillage.The results indicate the importance of retaining harvest residues on forest soils for achieving sustainable utilization and for conserving soil quality.