Aizhen Liang

Short-term effects of tillage practices on soil aggregate fractions in a Chinese Mollisol

Abstract Soil aggregate-size distribution and soil aggregate stability are used to characterize soil structure. Quantifying the changes of structural stability of soil is an important element in assessing soil and crop management practices. A 5-year tillage experiment consisting of no till (NT), moldboard plow (MP) and ridge tillage (RT), was used to study soil water-stable aggregate size distribution, aggregate stability and aggregate-associated soil organic carbon (SOC) at four soil depths (0–5, 5–10, 10–20 and 20–30 cm) of a clay loam soil in northeast China. Nonlinear fractal dimension (Dm) was used to characterize soil aggregate stability. No tillage led to a significantly greater aggregation for >1 mm aggregate and significant SOC changes in this fraction at 0–5 cm depth. There were significant positive relationships between SOC and >1 mm aggregate, SOC in each aggregate fraction, but there was no relationship between soil aggregate parameters (the proportion of soil aggregates, aggregate-associated SOC and soil stability) and soil bulk density. After 5 years, there was no difference in Dm of soil aggregate size distribution among tillage treatments, which suggested that Dm could not be used as an indicator to assess short-term effects of tillage practices on soil aggregation. In the short term, > 1 mm soil aggregate was a better indicator to characterize the impacts of tillage practices on quality of a Chinese Mollisol, particularly in the near-surface layer of the soil.

An appropriate time-window for measuring soil CO2 efflux: a case study on a Black soil in north-east China

Abstract Soil CO2 efflux rate is influenced by soil temperature which varies with time within a day. In order to determine a measuring time-window which can represent the daily average soil CO2 efflux rate from a Black soil in north-east China, soil CO2 efflux rates from no-tillage (NT) and mouldboard plough tillage (MP) plots were measured at a 2-h interval over 48 h four times in the growing season of 2008. Results showed that during the course of measurements, NT soil had a higher soil CO2 efflux rate than MP soil. Daily average soil CO2 efflux rate was matched relatively well with the CO2 efflux rate occurring between 09:00 h and 13:00 h, and between 19:00 h and 23:00 h. Our results indicate that the soil CO2 efflux rate measured between 09:00 and 11:00 h represents the daily average soil CO2 efflux rate during sunny days. When the measurements were conducted outside this time window, a procedure to adjust the CO2 efflux rates measured between 07:00 and 21:00 h (outside of the optimum time-window) to estimate daily average soil CO2 efflux rate is described.

Short-Term Impacts of No Tillage on Aggregate-Associated C in Black Soil of Northeast China

In order to get a good indicator to evaluate the impacts of no tillage (NT) on soil structure and soil quality, we studied the dynamics of total soil organic carbon (SOC) and aggregate-associated SOC, and their relationships in the plow layer (30 cm) in black soil of Northeast China under NT practice. The tillage experiment was established in Dehui County, Jilin Province, China, in 2001. The total SOC and aggregate-associated SOC under 5-yr tillage treatments were measured. NT practices did not lead to the increase of average SOC content at 0-30 cm depth, but it did significantly increase SOC at the top soil (0-5 cm). In NT plots, the change of SOC in >1 000 mu m aggregate was the same with that of total SOC, but the effect of NT on SOC in >1 000 mu m aggregate was greater than the effect on total SOC, suggesting that >1 000 mu m aggregate had more sensitive response to the impact of tillage practices. Also, significant positive correlation occurred between total SOC and SOC in >1 000 mu m aggregate in black soil. Consequently, in the short term soil macroaggregate >1 000 mu m could be used as an indicator to evaluate the impacts of tillage practices on soil structure in black soil of Northeast China.

Effects of tillage management on infiltration and preferential flow in a black soil, Northeast China

The impacts of no-tillage (NT) and moldboard plough (MP) managements on infiltration rate and preferential flow were characterized using a combined technique of double-ring device and dye tracer on a black soil (Mollisols) in Northeast China. The objective of this study is to evaluate how tillage practices enhance soil water infiltration and preferential flow in favor of soil erosion control in the study area. The steady infiltration rates under NT management are 1.6 and 2.1 times as high as those under MP management in the 6th and 8th years of the tillage management in place, while the infiltrated water amounts under NT management are 1.4 and 2.0 times as high as those under MP management, respectively. The depth of methylene blue penetrated into NT soil increases from 43 cm in the 6th year to 57 cm in the 8th year, which are 16 cm and 19 cm deeper than those in MP soil, respectively. The results of morphologic image show that more biological macro-pores occur in NT soil than in MP soil. These macro-pores play a key role in enhancing preferential flow in NT soil, which in turn promotes water infiltration through preferential pathways in NT soil. The results are helpful to policy-making in popularizing NT and have the implications for tillage management in regard to soil erosion control in black soil region of China.

Spatial variation of penetration resistance and water content as affected by tillage and crop rotation in a black soil in Northeast China

Limited information is available for understanding the spatial variation of soil penetration resistance (SPR) and water content induced by different tillage methods and crop rotations in a black soil of Northeast China. A 11-year tillage experiment in Dehui County, Jilin Province, Northeast China was conducted to evaluate the effects of tillage treatments [no tillage (NT), moldboard plow (MP), and ridge tillage (RT)] and crop rotations (corn-soybean rotation and continuous corn) on SPR and water content in relation to horizontal and vertical variations. Effect of NT, MP, and RT differed on the spatial distributions of SPR and water content among the rows, shoulders, and inter-rows. Compared with MP, NT, and RT treatments increased SPR in row and inter-row positions at the depth of 2.5–17.5 and 2.5–15 cm, respectively (p < 0.05). NT and RT led to significant decrement of soil water content than MP treatment in the rows and inter-rows of 0–15 cm layer (p < 0.05). Greater variability of SPR and water content was found in MP than NT and RT plots. Crop rotation did not have a marked impact on SPR and water content (p > 0.05). Tillage, sampling position, along with depth greatly affected SPR and water content (p < 0.05).

Near-infrared spectroscopic assessment of hot water extractable and oxidizable organic carbon in cultivated and uncultivated Mollisols in China

Abstract The hot water extractable organic carbon (HWEOC) and K2Cr2O7 oxidizable organic carbon (OOC) have been suggested as indicators to assess soil management effects on soil organic matter; however, traditional methods for measuring these C fractions are costly and tedious. The potential of using near-infrared reflectance spectroscopy (NIRS) with partial least squares (PLS) regression to predict HWEOC and OOC concentrations in cultivated and uncultivated Mollisols in China were explored in this paper. The soil organic carbon (SOC), OOC, and HWEOC in 0–30 cm layer were 37.6, 41.2, and 58.8% lower in cultivated than in uncultivated soils. The HWEOC is more sensitive to soil management relative to SOC or OOC. HWEOC concentrations were accurately predicted using NIRS-PLS model, with high coefficient of determination (R 2=0.89), residual prediction deviation (RPD=3.69) for model calibration, and high R 2 (0.85), RPD (3.03), and correlation coefficient (r=0.92) of predicted and measured values in the validation set. Excellent prediction for OOC was acquired with R 2 and RPD at 0.97 and 6.11 for model calibration, respectively, and R 2 and RPD and r at 0.92, 5.75, and 0.97 for model validation, respectively. This study indicated that the HWEOC could be used to illustrate the impacts of agronomic management on soil quality. Both of HWEOC and OOC can be accurately quantified using NIRS-PLS approach.

Changes in soil organic carbon stocks under 10-year conservation tillage on a Black soil in Northeast China

Biased assessment of tillage impacts on soil organic carbon (SOC) sequestration are often associated with a lack of information on the initial level of SOC stocks. The present study reported the changes in SOC concentrations and stocks following 10-year different tillage practices relative to the initial SOC levels. The tillage trial included no tillage (NT), ridge tillage (RT) and mouldboard plough (MP) on a Black soil (Hapludolls) in Northeast China. Results showed that tillage, soil depth and time significantly affected SOC concentration and SOC stock. Tillage and crop residue retention had great impacts on the SOC concentrations in the top 0·1 m layer. Compared with MP and NT, RT resulted in higher SOC concentration and SOC stock in the plough layer (0–0·2 m), which became more obvious with time. The soil under NT and RT had higher stratification ratios (SR) of SOC (SR, the ratio of SOC concentration in 0–0·05 m to that in 0·1–0·2 m) than under MP. Significant positive and nearly identical linear relationships between the SR of SOC and the duration of tillage practices occurred for both NT and RT soils; the increased SR in NT resulted from both SOC increase in surface and SOC decrease in subsurface soils, but in RT, the increased SR was only from a substantial SOC increase in surface soil. Accordingly, the present study highlights that RT was more helpful than NT in carbon sequestration for the studied Black soil in Northeast China.

Short-Term Effects of Tillage Practices on Soil Organic Carbon Turnover Assessed by δ13C Abundance in Particle-Size Fractions of Black Soils from Northeast China

The combination of isotope trace technique and SOC fractionation allows a better understanding of SOC dynamics. A five-year tillage experiment consisting of no-tillage (NT) and mouldboard plough (MP) was used to study the changes in particle-size SOC fractions and corresponding δ 13C natural abundance to assess SOC turnover in the 0–20 cm layer of black soils under tillage practices. Compared to the initial level, total SOC tended to be stratified but showed a slight increase in the entire plough layer under short-term NT. MP had no significant impacts on SOC at any depth. Because of significant increases in coarse particulate organic carbon (POC) and decreases in fine POC, total POC did not remarkably decrease under NT and MP. A distinct increase in silt plus clay OC occurred in NT plots, but not in MP plots. However, the δ 13C abundances of both coarse and fine POC increased, while those of silt plus clay OC remained almost the same under NT. The C derived from C3 plants was mainly associated with fine particles and much less with coarse particles. These results suggested that short-term NT and MP preferentially enhanced the turnover of POC, which was considerably faster than that of silt plus clay OC.

Effect of tillage and crop residue on soil temperature following planting for a Black soil in Northeast China

Crop residue return is imperative to maintain soil health and productivity but some farmers resist adopting conservation tillage systems with residue return fearing reduced soil temperature following planting and crop yield. Soil temperatures were measured at 10 cm depth for one month following planting from 2004 to 2007 in a field experiment in Northeast China. Tillage treatments included mouldboard plough (MP), no till (NT), and ridge till (RT) with maize (Zea mays L.) and soybean (Glycine max Merr.) crops. Tillage had significant effects on soil temperature in 10 of 15 weekly periods. Weekly average NT soil temperature was 0–1.5 °C lower than MP, but the difference was significant (P < 0.05) only in 2007 when residue was not returned in MP the previous autumn. RT showed no clear advantage over NT in increasing soil temperature. Higher residue coverage caused lower soil temperature; the effect was greater for maize than soybean residue. Residue type had significant effect on soil temperature in 9 of 15 weekly periods with 0–1.9 °C lower soil temperature under maize than soybean residue. Both tillage and residue had small but inconsistent effect on soil temperature following planting in Northeast China representative of a cool to temperate zone.