Aggregate stability responses of three derived-savannah soils to poultry-droppings manure at different pulverisation-to-sampling time intervals

Deforestation effects on soil aggregate stability quantified by the high energy moisture characteristic method

The present study was carried out at JNKVV, Jabalpur (23010’ N latitude, 79057’ E longitudes and at elevation 393.0 meters above mean sea level). This study was carried out in 2019 that laid out in split plot design with nine main treatments of land use practices (forest land, perennial forage land, uncultivated land, aonla orchard, rice-wheat system, soybean-wheat system, guava orchard, mango orchard and citrus orchard) and three sub-plot treatments of soil depths (0-20, 20-40 and 40-60 cm) which were replicated three times. A total of 81 soil samples were subjected to determination of different size (> 5.0, 2.0-5.0, 1.0-2.0, 0.50-1.0, 0.25-0.50, 0.10-0.25 and <0.10 mm) water stable soil aggregates and mean weight diameter of soil aggregates. Results revealed that land use practices and soil depths significantly affect the mean weight diameter of soil aggregates, distribution of different size soil aggregates. It was noted that irrespective of soil depths, proportions of macro-aggregates (>0.50 mm size) and mean weight diameter were highest under forest land and lowest in soybean-wheat system. However, number of micro-aggregates (< 0.50 mm) increased with soil depths and macro-aggregates and mean weight diameter of soil aggregates were highest at 0-20 cm depth. It can be concluded that extent of soil disturbance significantly alters the proportion of macro-aggregates (>0.50 mm size) and mean weight diameter of water stable soil aggregates with higher in undisturbed (forest, uncultivated and perennial forage) land uses and lower in crop lands which decreased with increase in soil depths.

Wang, E., Cruse, R. M., Chen, X. and Daigh, A. 2012. Effects of moisture condition and freeze/thaw cycles on surface soil aggregate size distribution and stability. Can. J. Soil Sci. 92: 529–536. Freeze/thaw cycles can affect soil aggregate stability, which in turn impacts wind and water erosion. The objectives of this laboratory study were: (1) to determine the effect of variable freeze/thaw cycles and soil water conditions on aggregate size distribution and stability; and (2) to evaluate differences in aggregate size distribution and stability between disturbed soil and undisturbed soil cores as affected by freeze/thaw cycles and soil water conditions. Surface soil was collected before freezing in late fall of 2009. Aggregates isolated from disturbed soil or intact soil cores were subjected to a factorial combination of 3 gravimetric water content treatments: 0.15 m3 m−3, 0.23 m3 m−3 or 0.30 m3 m−3, and 3 freeze/thaw treatments: 0, 3, or 9 cycles. A freeze/thaw cycle involved soil freezing at –10∘C for 24 h, followed by thawing at 5∘C for 24 h. Most aggregate size classes were affected significantly (P<0.05) by freeze/thaw cycles except for wet-sieved aggregates >5 mm. Dry-sieved aggregates were relatively more sensitive to the freeze/thaw treatment than wet-sieved aggregates. The mean weight diameter (MWD) of dry-sieved aggregates was significantly (P<0.05) greater at 0.30 m3 m−3 than 0.15 m3 m−3 water content, but the opposite trend was observed for MWD of wet aggregates and aggregate stability. There was a significant (P<0.05) response of the MWD in dry-sieved aggregates to the interactive freeze/thaw×water content effect that differed for aggregates obtained from disturbed soil and those in the undisturbed soil core, but not for the MWD of wet-sieved aggregates and aggregate stability.

Agricultural systems produce both detrimental and beneficial effects on soil quality (SQ). We compared soil physical properties of long-term conventional (CON) and alternative (ALT) cropping systems near Akron, Colorado (CO); Brookings, South Dakota (SD); Bushland, Texas (TX); Fargo, North Dakota (ND); Mandan (ND); Mead, Nebraska (NE); Sidney, Montana (MT); and Swift Current, Saskatchewan (SK), Canada. Objectives were to quantify the changes in soil physical attributes in cropping systems and assess the potential of individual soil attributes as sensitive indicators of change in SQ. Soil samples were collected three times per year from each treatment at each site for one rotation cycle (4 years at Brookings and Mead). Water infiltration rates were measured. Soil bulk density (BD) and gravimetric water were measured at 0–7.5, 7.5–15, and 15–30 cm depth increments and water-filled pore space ratio (WFPS) was calculated. At six locations, a rotary sieve was used to separate soil (top 5 cm) into six aggregate size groups and calculate mean weight diameter (MWD) of dry aggregates. Under the CON system at Brookings, dry aggregates (>19 mm) abraded into the smallest size class (<0.4 mm) on sieving. In contrast, the large aggregates from the ALT system abraded into size classes between 2 and 6 mm. Dry aggregate size distribution (DASD) shows promise as an indicator of SQ related to susceptibility of soil to wind erosion. Aggregates from CON were least stable in water. Soil C was greater under ALT than CON for both Brookings and Mead. At other locations, MWD of aggregates under continuous crop or no tillage (ALT systems) was greater than MWD under CON. There was no crop system effect on water infiltration rates for locations having the same tillage within cropping system. Tillage resulted in increased, decreased, or unchanged near-surface BD. Because there was significant temporal variation in water infiltration, MWD, and BD, conclusions based on a single point-in-time observation should be avoided. Elevated WFPS at Fargo, Brookings, and Mead may have resulted in anaerobic soil conditions during a portion of the year. Repeated measurements of WFPS or DASD revealed important temporal characteristics of SQ that could be used to judge soil condition as affected by management.

The potential of using flue gas desulfurization by‐products (FGD) for the reclamation of acid minespoil was assessed in Tuscarawas County of Ohio, USA. In Treatment 1, 280 Mg ha −1 of FGD was incorporated into the graded spoil to a depth of 20 cm. In Treatment 2, 280 Mg ha −1 of FGD and 112 Mg ha −1 of yard waste compost were incorporated into the graded spoil (FGDC). In Treatment 3, 112 Mg ha −1 of limestone was incorporated into the graded spoil and was covered with 20 cm of graded borrowed topsoil (BTS). Six cores and six bulk soil samples were obtained from each treatment for the 0‐ to 10‐cm depth in summer 2002. From the 10‐ to 20‐cm depth, only bulk soil samples were obtained. Bulk and core soil samples were also collected from an unreclaimed spoil (SP) and a nearby unmined soil (UMS). Among the three reclamation treatments, BTS showed better soil quality with higher soil organic C (28.5 Mg ha −1 ), water‐stable aggregation (556 g kg −1 ), and mean weight diameter (3.2 mm) of aggregates than FGDC or FGD treatments. The FGDC had higher soil inorganic and organic C than FGD. However, saturated hydraulic conductivity ( K s ), cumulative infiltration ( I ), infiltration rates at 5 min ( i 5 ) and 2.5 h ( i c ), and soil pH were similar among three treatments. Among treatments and controls, soil bulk density (ρ b ) was lower for FGD, FGDC, and UMS than BTS and SP; and water‐stable aggregation and mean weight diameter of the aggregates was higher for UMS and BTS than FGDC, FGD, and SP for both depths. The I and i c were similar among UMS and treatments. Reclamation improved the soil quality with higher soil pH (≈7) and inorganic and soil organic C than in the SP. With respect to FGD, the soil organic C in FGDC increased at the rate of 0.64 Mg ha −1 yr −1 for the 0‐ to 10‐cm depth. Overall, BTS was the best reclamation treatment. However, if topsoil is unavailable or transport is expensive, FGDC can be used as an effective reclamation material.

Summary Climate change has altered global precipitation regimes in terms of intensity and frequency of drought stress and, consequently, it is likely to affect soil moisture and soil aggregation. However, we know little about the effects of drought on soil aggregate size, distribution and stability, and how that affects carbon sequestration. A drought manipulation experiment was conducted by throughfall exclusion treatment (TET) of 50% in two planted forests ( Pinus massoniana Lamb. and Castanopsis hystrix A.DC.) in subtropical China. The aim was to investigate the effects of a reduction in throughfall on aggregate size, distribution and stability. The results from the 4‐year experiment show that the TET affected soil moisture content significantly (with 14.5 and 20.4% decreases in the P. massoniana and C. hystrix plantations, respectively) compared with the control. Soil temperature at 0–5‐cm soil depth and soil texture were not affected significantly. Soil porosity in the TET plots was greater than that of the control, whereas soil bulk density and free Al oxide content were less. The mass fractions of macroaggregates (> 0.25 mm) and mean weight diameter (MWD) of aggregates, an indicator of aggregate stability, decreased in the TET compared with the control. Variation in aggregate size, distribution and stability can be caused by Fe and Al oxides, soil texture, bulk density and porosity. Our results indicated that TET reduced soil aggregate stability in subtropical plantations because of a decrease in free Al oxide and an increase in porosity. Slaking effects from variation in soil moisture were also possible for the decreased MWD. This study suggests disturbance of forest soils should be minimized in the context of a decline in precipitation. Highlights Size, distribution and stability of forest soil aggregates were evaluated under throughfall exclusion. TET reduced free Al oxide content but increased soil porosity, leading to breakdown of macroaggregates. Soil aggregate stability was reduced by TET. Fe and Al oxides and soil texture contributed more than SOC to aggregate size and stability.

Changes in Soil Aggregate, Carbon, and Nitrogen Storages Following the Conversion of Cropland to Alfalfa Forage Land in the Marginal Oasis of Northwest China

Residue retention and minimum tillage improve physical environment of the soil in croplands: A global meta-analysis

The study aims to elucidate the impact of organic inputs on strength and structural stability of aggregates in a sandy loam soil. Tensile strength, friability and water stability of aggregates, and the carbon contents in bulk soil and in large macro (>2 mm), small macro (0.25-2 mm), micro (0.053-0.25 mm) and silt+clay size (<0.053) aggregates were evaluated in soils from a long-term experiment with rice-wheat rotation at Modipuram, India, with different sources and amounts of organic C inputs as partial substitution of N fertilizer. Addition of organic substrates significantly improved soil organic C contents, but the type and source of inputs had different impacts. Tensile strength of aggregates decreased and friability increased through organic inputs, with a maximum effect under green gram residue (rice)-farmyard manure (wheat) substitution. Higher macroaggregates in the crop residue- and farmyard manure-treated soils resulted in a higher aggregate mean weight diameter, which also had higher soil organic C contents. The bulk soil organic C had a strong relation with the mean weight diameter of aggregates, but the soil organic C content in all aggregate fractions was not necessarily effective for aggregate stability. The soil organic C content in large macroaggregates (2-8 mm) had a significant positive effect on aggregate stability, although a reverse effect was observed for aggregates <0.25 mm. Partial substitution of nitrogen by organic substrates improved aggregate properties and the soil organic C content in bulk soil and aggregate fractions, although the relative effect varied with the source and amount of the organic inputs.

Influence of cover crops on soil aggregate stability, size distribution and related factors in a no-till field

Sawah, an Indo-Malaysian word for rice paddy, is used in West Africa to refer to a lowland rice field that is bunded, puddled and levelled for ease of water control and management. There are insufficient data on lowland soil and rice responses to sawah preparation intensity, defined by relative completeness of these three land preparation activities (bunding + puddling + levelling). This study assessed soil physical properties and rice grain yield under sawah preparation intensities [complete (bunded, puddled, levelled), quasi-complete (bunded, slightly puddled, levelled) and incomplete (bunded, non-puddled/levelled) sawah, and control] and soil amendments [NPK, poultry droppings (PD), rice husk (RH), its ash (RHA) and control] in southeastern Nigeria for 3 years. At rice maturity, soil bulk density increased with decreasing intensity of sawah preparation and was lower with than without amendments, being lowest in RH-amended plots. Aggregate sizes were adversely affected in the three sawah plots and by soil amendments, mainly NPK. Mean-weight diameter of aggregates was always highest in complete sawah, while showing lowest and highest values in NPK and PD plots, respectively. Sawah bunding/puddling and amendments positively affected soil water content. Saturated hydraulic conductivity was always highest in complete sawah plus PD and lowest in the control. Rice grain yield did not always increase with sawah preparation intensity but all sawah plots out-yielded the control after the first year. All amended plots always out-yielded the control, with higher values due to PD/RH compared with RHA/NPK in the third year. Soil physical control of rice grain yield revealed strengths (R2, 0.847–0.420) in decreasing order of conductivity, bulk density/water content, <0.25-mm aggregates and mean-weight diameter. Only soil bulk density related inversely to grain yield up till a critical value of 1.05 g cm−3. Complete sawah or, where improved soil structure after rice is not desired, quasi-complete/incomplete sawah can be combined with organic amendments (PD/RH) to grow lowland rice.

Ectomycorrhizal fungi in association with Pinus sylvestris seedlings promote soil aggregation and soil water repellency

Agricultural practices that alter the soil organic matter (SOM) content are expected to cause changes in soil stability and aggregation. The objective of this study was to evaluate short‐term (&lt;2 yr) changes in water‐stable aggregates (WSA) in a silt‐loam soil under different management regimes. The interactive effects of tillage (no‐till and conventional tillage), crop rotations (continuous corn, corn‐soybean rotation) and composted cattle manure applications [0, 15, 30, and 45 Mg (wet weight) ha −1 ] on WSA were assessed in a factorial (tillage × crop rotation) split plot (compost) experiment. The proportion of WSA &gt;4 mm was greater in compost‐amended than unamended soils within 1 yr, and the mean weight diameter (MWD) of aggregates increased with increasing compost application rates. By the second year of the study, no‐till soils under continuous corn and the soybean phase of the corn‐soybean rotation had more WSA &gt;4 mm and a greater MWD than any crop rotation in conventionally tilled soils. Increasing the C input to soil increased the MWD of aggregates. The MWD of aggregates was related to the C content of soils under no‐till, but not conventional tillage, suggesting more physical stabilization of organic matter (OM) in no‐till than conventional tillage agroecosystems. Our findings indicate rapid improvements in aggregation of a silt‐loam in the first 2 yr after compost application and the adoption of no‐tillage practices.

Soil structural stability often decreases as the intensity of cultivation increases. The effect of three different management systems (grass, no‐till, and till) on soil aggregate stability and sizes were studied in six Ustolls and two Usterts on central South Dakota farms. Soil structure was morphologically described throughout the profile. Stability of dry and wet aggregates in the topsoil was tested by dry and wet sieving. Most structural changes were observed in the top 0 to 0.20 m. Granular structure was dominant under grass, whereas plates, blocks, and compacted layers were most common in conventionally tilled and no‐till soils. The largest mean weight diameters (MWD) of dry aggregates were found in no‐till soils (10 mm vs. 7 in till and 6 in grass). Wet aggregate stability was higher in grass (87%) than in cultivated soils (70%). After about 10 yr of no‐till management, no‐till soil aggregates were significantly more stable (5% for wet and 32% for dry aggregates) than till aggregates only in the top 0 to 0.05 m. The structural stability of cultivated soils was greater in Usterts than in Ustolls.

Physical and chemical properties of soils under some piñon-juniper-oak canopies in a semi-arid ecosystem in New Mexico