Water-stable Aggregates Research Articles

Amendment with Nanoparticulate Gypsum Enhances Spinach Growth in Saline-Sodic Soil

The use of nano-gypsum in low doses can be an innovative method to mitigate salinity-sodicity effects and enhance spinach growth in saline-sodic soil. We evaluated nano-gypsum in four low doses of 960, 480, 240, and 120 kg ha−1, in addition to the control and the recommended conventional gypsum dose (~ 30 t ha−1), in a randomized complete pot experiment. The pots of soil were incubated in a laboratory for 2 months and leached 5 times for another 2 months. Then, spinach was grown in the soil for 60 days. The nano-gypsum dose of 240 kg ha−1 with leaching was the best at improving the soil and spinach growth characteristics compared with the other doses and both control and conventional gypsum rate. Moreover, it was considered the critical nano-gypsum threshold rate. Compared to control after soil leaching, the critical rate increased the water-stable aggregate index and reduced bulk density by 57.39% and 16.30%, respectively; accordingly, the saturated hydraulic conductivity increased up to 2.34 times. Improved hydraulic conductivity led to a decrease in exchangeable Na ratio by 91% and reduced both soil salinity and pH by 83% and 1 unit, respectively. These great improvements in the soil properties favored the spinach growth indicators, which increased leaf area index, root hair index, and fresh yield by 2.20, 4.41, and 1.29 times, respectively, when compared to the recommended conventional gypsum rate. Accordingly, nano-gypsum in low doses is considered an innovative alternative to high doses of conventional gypsum to mitigate salinity-sodicity effects and enhance spinach growth in saline-sodic soil.

Agriculture management and seasonal impact on soil properties, water, sediment and chemicals transport in a hazelnut orchard (Croatia)

Soil and water conservation practices are key to agroecosystems sustainability and avoiding diffuse pollution. Here, we compare the impacts of different types of mulch, barley straw (Straw), wooden chips (Chip) and tillage (Till) on vegetation mulch cover (VMC); soil properties, bulk density (BD), mean weight diameter (MWD), water stable aggregates (WSA), soil water content (SWC), soil organic matter (SOM), pH and total phosphorous (P), potassium (K), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), Zinc (Zn) and lead (Pb). We also assessed the ponding time (PT), runoff time (RT), runoff, sediment concentration (SC), sediment loss (SL) and chemicals transport (the same studied in soil). A set of rainfall simulation experiments (90 in total) was applied in the different Spring, Summer, and Fall treatments. The results showed that mulch increased VMC in all the seasons, while other properties (BD; MWD, WSA SOM, pH) were not affected, especially in Spring. The biggest impact was observed in Fall, especially in the Till plot, due to the tillage practices applied in Summer. Mulch increased PT, RT and reduced runoff, SL and chemicals transport. Chemical losses were very much associated with SL, and the concentration of P and metals in soil depended on soil Ca and pH. SWC, MWD and runoff were inversely related to PT, RT and SC. Finally, BD, VMC and SOM were highly associated. Overall, tillage practices dramatically impact SL, and diffuse pollution and urgent measures are needed to reverse this. Mulching is excellent and cost-effective to mitigate the impacts of agriculture on land degradation and diffuse pollution.

Impact of Long Term Nutrient Management on Soil Quality Indices in Rice-Wheat System of Lower Indo-Gangetic Plain

Globally, soil degradation is an important issue for sustainable crop production. Soil quality indicators are the soil attributes that address the ecological functions of soil. Therefore, indicator-based soil quality assessment has been emphasized for quantifying the relative soil quality changes in different nutrient management systems. Soil quality underthe rice (Oryza sativa L.) and wheat (Triticum aestivam L.) cropping system was assessed using a modified “Soil Management Assessment Framework (SMAF)” model. Soil’s physical, chemical, nutritional, and biological indices were analyzed for different nutrient management strategies, viz., inorganic fertilizer (NPK), NPK + 7.5 Mg ha−1 farmyard manure (NPKF), NPK + 10.0 Mg ha−1 paddy straw (NPKP) and NPK + 8.0 Mg ha−1 Sesbania sesban L. green manure (NPKG). Nutrient management strategies significantly influenced soil quality indices. NPKF showed the highest SMAF score for soil physical quality index followed by NPKP > NPKG > NPK and control; whereas the score of soil chemical quality was greater in NPKP followed by NPKF/NPKG > NPK > control (p > 0.05). Overall, the soil nutritional quality index was greater in NPKF (0.96) followed by NPKG > NPKP > NPK, and the least was in control. The SMAF score of soil biological quality index was highest in NPKF compared to NPKG > NPKP > NPK > control. The wholesome index of SMAF (SQI) was developed withthehighest score in NPKF (0.94) followed by NPKG (0.90) > NPKP (0.89) > NPK (0.79) > control (0.71). The β-glucosidase activity, mineralizable C, KMnO4 oxidizable N, microbial biomass C, and total water-stable aggregates explained 82% variability in the dataset and represented a good agreement with system yield (R2 = 0.89, p < 0.05). This study concludes that the conjunctive application of NPK with manures restores the overall soil quality more than other management practices, and thatthe SQ indices can be utilized for screening the best management practices for rice-wheat and other similar cropping systems.

Soil Slope Exposure Affects Physico-Chemical and Microbiological Properties in Soil Aggregate Size Fractions

Slope exposure is known to affect soil biogeochemical processes in mountainous forest ecosystems, but little attention has yet been paid to its influence at a soil aggregate scale. Therefore, we evaluated the effects of slope exposure (north- vs south-facing slope) on the physico-chemical and microbiological properties of bulk soil and dry-sieved and water-stable aggregate size fractions in both organic (OF) and mineral (AE) horizons in an Italian alpine forest. The changes in organic carbon (OC) and nitrogen (ON) fractions were assessed together with a battery of thirteen enzyme activities involved in the main nutrient cycles. In addition, soil biological properties including microbial biomass (estimated as double-stranded DNA content), and microbial activity (assessed as the ratio between the extra-(exDNA) and intracellular (iDNA) fractions of the total soil DNA pool) were determined. The OF horizon at the north-facing slope was enriched in recalcitrant and insoluble OC and ON fractions and characterized by a lower microbial activity, as indicated by the higher exDNA/iDNA ratio with respect to the south-facing slope. On the contrary, exDNA and iDNA contents, microbial biomass, as well as most of the enzyme activities, reached higher levels at the southern exposure in the AE horizon. These exposure-effects were bulk soil- and aggregate size fraction-specific. Overall, lower values of the chemical and microbiological parameters were found in the water-stable fraction. Our findings indicate that slope exposure (and thus topography), soil horizon, and aggregate size distinctly influence soil OC dynamics in mountain ecosystems.

Effects of the application of different improved materials on reclaimed soil structure and maize yield of Hollow Village in Loess Area.

In order to solve the soil problem of poor structure and low fertility after the abandoned homestead reclamation of Hollow Village in Loess Area and to improve the quality of the reclaimed soil in Hollow Village, a five-year field experiment was conducted here. In this experiment, the following seven treatments were applied: no modified material (CK), maturing agent (TM), fly ash (TF), organic fertilizer (TO), maturing agent + fly ash (TMF), maturing agent + organic fertilizer (TMO) and fly ash + organic fertilizer (TFO), and the effects of different improved materials on soil properties and crop yield were studied. The results showed that: soil organic matter (SOM) and total nitrogen contents increased significantly after the application of different improved materials, which promoted the cementation and aggregation of water-stable microaggregates (< 0.25 mm), and the water-stable macroaggregates showed an increasing trend. In the 0–0.15 m soil layer, the proportion of water-stable macroaggregates under TM, TF, TO, TMF, TMO, and TFO treatment increased by 328.2%, 130.0%, 87.8%, 81.1%, 36.7%, and 12.2% compared with CK, respectively. Meanwhile, TF, TO, TMF, TMO, TFO treatments significantly increased the mean weight diameter (MWD) and geometric mean diameter (GMD) values, reduced soil bulk density, the stable aggregate index (ELT) and fractal dimension (D) values (P < 0.05), and the stability of soil structure and the capacity of soil moisture retention has been significantly improved. The SOM content had a significant positive correlation with MWD, GMD, and > 2 mm water-stable aggregates and a significant negative correlation with the ELT, D, and water-stable microaggregates. In particular, the organic–inorganic coupling treatment of TFO showed the highest SOM content, soil moisture content, water-stable macroaggregates and maize yield, which was the most appropriate amendment for improving the reclaimed soil structure and fertility of Hollow Village in Loess Area.

Subsoiling and plowing rotation increase soil C and N storage and crop yield on a semiarid Loess Plateau

Subsoiling loose subsoil, plowing loose topsoil, burying crop residue, the take turns used of subsoiling and plowing in years seem to be good methods to achieve the goal of regulating topsoil and subsoil structure and improving soil fertility and crop yield. However, the evaluation of the long-term effects of a subsoiling and plowing yearly rotation in a crop residue retention cropping system is lacking. Therefore, a 12-year (2007–2019) experiment was established to evaluate the influence of a subsoiling and plowing rotation with residue retention on water-stable aggregates (WSA), soil organic carbon (SOC), total nitrogen (TN) storage, and crop yield in a winter wheat-spring maize rotation field. Tillage treatment was 1-year subsoiling and 1-year plowing rotation (ST/CT), and continuous subsoiling (ST) and plowing (CT) were used as controls. During the 12-year experiment, the ST/CT rotation reduced the mean C input of winter wheat (5.4%) and spring maize (1.7%) at harvest compared with the ST treatment but significantly improved the mean C input of winter wheat (6.2%) and spring maize (10.9%) at harvest compared with the CT treatment. After 12 years of the experiment (2019), the ST/CT rotation significantly increased water-stable macroaggregates (6.6% and 7.7%) at 0–40 cm compared with the ST and CT treatments, respectively. In addition, the ST/CT rotation had a lower SOC (0.11 Mg·ha−1) and N (0.16 Mg·ha−1) storage at the 0–10 cm soil depth than the ST treatment. However, the ST/CT rotation had a higher SOC (0.51 and 2.77 Mg·ha−1) and N storage (0.11 and 0.18 Mg·ha−1) at the 10–20 and 20–40 cm soil depths than the ST treatment. When compared to the CT treatment, the ST/CT rotation significantly improved SOC and N storage at 0–10 cm (4.24 and 0.18 Mg·ha−1), 10–20 cm (0.50 and 0.14 Mg·ha−1), and 20–40 cm (2.66 and 0.22 Mg·ha−1), respectively. Additionally, the ST/CT rotation also significantly enhanced the yield of winter wheat (5.6% and 10.5%) and spring maize (8.4% and 12.7%) compared with the ST and CT treatments, respectively. Different tillage significantly influenced the yield stability and sustainability of winter wheat, but no marked differences were observed in spring maize. In addition, a nonlinear relationship indicated that maximal SOC storage-responsive C input levels ranged from 3580 kg·ha−1 to 6007 kg·ha−1 for winter wheat and spring maize. ST/CT rotation can increase SOC storage before C saturation to reach maximized yield. To improve and sustain nutrient storage and crop production in winter wheat-fallow-spring maize rotation fields, ST/CT rotation seems to be a more suitable tillage practice.

Effects of reduced nitrogen application on soil aeration and root nodule growth of relay strip intercropping soybean

<p id="C3">To study the effects of planting system and nitrogen application rate on soybean soil aeration environment and nodulation and nitrogen fixation, we adopted a two-factor split area experiment design, with the main area of planting pattern [soybean monoculture (SS), maize/soybean relay strip intercropping (MS)], and the sub-regions of different nitrogen application rates [no nitrogen application (NN: 0 kg hm^-2), reduced nitrogen application (RN: 45 kg hm^-2), and constant nitrogen application (CN: 60 kg hm^-2)]. The dynamic changes of soil O₂ content and soil respiration rate during soybean growth period was monitored, the differences of soil water-stable aggregates, bulk density, and porosity of each treatment were analyzed, and the variation characteristics of nodulation amount and nitrogen fixation capacity during soybean growth period were discussed. Two years’ data showed that, compared with monoculture soybean, relay strip intercropping soybeans increased soil O₂ content, the percentage of aggregates with a particle size &gt; 2 mm, significantly increased soil porosity and soil respiration rate during the late growth period in soybean; reduced the percentage of aggregates with a particle size of &lt; 1 mm and soil porosity. There was no significant difference in the dry weight of nodules at R5 stage, but the number of nodules was significantly increased by 39.9%. Nitrogenase activity and nitrogen fixation potential were also significantly higher than those of monocrops. Among the various nitrogen application rates, the soil O₂ content, the percentage content of 0.25-1.00 mm particle size, and the soil respiration rate of relay strip intercropping soybean were the highest in RN treatment. Nitrogen application decreased the percentage content of water-stable aggregates with particle size &lt; 0.25 mm and soil bulk density; nitrogen application significantly inhibited the nodulation amount, nitrogenase activity and nitrogen fixation potential of monoculture soybean in the early stage, but the inhibitory effect of nitrogen fertilizer was alleviated at R5 stage. Reduced nitrogen application increased nodulation at the late stage of relay strip intercropping soybean, and it could significantly enhance the nitrogenase activity and nitrogen fixation potential of soybeans during the growth period. Relay strip intercropping soybean combined with reduced nitrogen application promoted the formation of large aggregates, increased soil porosity, improved soybean soil aeration environment, maintained higher soil O₂ content, promoted soil respiration, and facilitated the nodulation and nitrogen fixation of soybean at later stages.

Long-Term Field and Horticultural Crops Intensification in Semiarid Regions Influence the Soil Physiobiochemical Properties and Nutrients Status

The study was conducted to assess the long-term effects of predominant land uses on physicochemical properties, nutrient status and their interactions in soils of south-western Punjab representing the semi-arid soils of India. From each site, soil samples of three predominant land use viz. croplands, horticultural lands and uncultivated lands were collected from 0–15, 15–30, 30–60 and 60–90 cm depths. Soils of both croplands and horticultural lands were classified as sandy loam whereas uncultivated lands showed loamy sand texture with relatively higher pH, electrical conductivity (EC) and bulk density (Bd). Greater soil organic carbon (SOC), available nitrogen (N), phosphorus (P) and micronutrients (Zn, Cu, Fe and Mn) in horticulture might be due to the higher addition of OC and mineral nutrients through the decomposition of leaf litterfall and root deposits over their removal from soils while long-term use of potassic fertilizer raised the available K contents in croplands. Profile study up to 90 cm depicted the largest sequestration of 74.89 Mg C ha−1 under orchards which was 40 and 70% higher than croplands and uncultivated lands respectively. Significant variability in water-stable aggregates (WSA) (R2 = 0.5843, p &lt; 0.05) and mean weighted diameter (MWD) (R2 = 0.6497, p &lt; 0.01) with SOC indicated better soil stability in horticulture due to the presence of higher SOC. Positive relations of soil available micronutrients with SOC and finer soil particles were supported by the results of correlation, Principal component analysis and dendrogram indicating horticulture as a potent source of available micronutrients. An overall superiority of horticultural land use over the other two land uses in terms of nutrient status and soil stability suggests its inclusion as a positive strategy that could be taken into account in policymaking for maintaining productivity along with the sustainability of the concerned land degradation prone area.

Aggregate stability and size distribution regulate rainsplash erosion: Evidence from a humid tropical soil under different land-use regimes

Soil erosion by water is a serious global ecological issue that leads to land degradation and threatens ecosystem sustainability. Splash erosion resulting from raindrop impact is the first stage of the erosion process and is mainly responsible for the detachment and migration of soil surface aggregates. In humid tropical regions, however, there has been little quantitative analysis of the relations between splash erosion and variable aggregate characteristics such as stability, particle size distribution and organic matter content. The objective of the current study was to determine how rain splash erosion is related to soil aggregate characteristics under land-use change, i.e., the conversion of tropical rainforest (TR) into rubber plantation (RP). Splash cups containing dry-sieved aggregate samples with eight size classes were exposed to natural rainfall to measure the splash erosion rate. The results showed that the initial aggregate organic carbon, water-stable aggregate index (WSA) and mean weight diameter (MWD) decreased by 31%, 9% and 48%, respectively, after 32 years of rubber cultivation. These degenerations in aggregate properties increased the susceptibility of soil aggregates to erosion and mutually contributed to a higher average splash erosion rate in RP (1.20 kg m−2) than in TR (1.09 kg m−2), regardless of aggregate size fractions. Splash erosion rates for all aggregate sizes were significantly positively correlated with rainfall kinetic energy, rainfall amount and intensity during the study period. The average splash erosion rate of aggregates first increased and then decreased with a decline in aggregate size in both TR and RP. The minimum and maximum splash rates were observed within 10–8 mm and 0.5–0.25 mm size fractions, respectively. In particular, the proportion of small-sized aggregates (i.e., 1–0.15 mm) with a relatively high splash erosion rate increased remarkably after land-use change. This exerted a negative impact on splash erosion control as well as on the sustainable development of rubber cultivation. Increasing the additional input of organic materials (e.g., intercropping cash crops with rubber trees) may help to enhance large aggregate formation and stabilization, which could minimize the risk of splash erosion at the aggregate scale for eroded rubber plantation ecosystems.

GREEN MANURES AND NPK FERTILIZER APPLICATIONS EFFECT ON ORGANIC CARBON POOL, SOIL PHYSICAL PROPERTIES AND CUCUMBER PRODUCTION

Deterioration of soil physical properties and organic matter depletion resulting from continuous cultivation of tropical sandy loam soils, even with the regular applications of inorganic fertilizers is common. To regenerate the soil organic matter and maintain soil structural and hydraulic properties for crop production, the effects of different legumes green manures and NPK chemical fertilizer were evaluated after a 3-year field experiments at the University of Port Harcourt, Teaching and Research Farm (2018 – 2021). Treatments were: 5 tons ha-1Centrocema (Ce5), 5 tons ha-1 Gliricidia (Gl5), 5 tons ha-1Calapogonium (Ca5), NPK 20:10:10 (NPK) and the Control, arranged in a Randomized Complete Block Design (RCBD), in 5 replications. Results showed that three annual applications of Centrocema, Gliricidia, and Calapogonium increased soil organic carbon pool at the 0-30 cm topsoil, and reduced the bulk densities by 8.5%, 4.1%, and 7.0%, respectively, compared to the NPK fertilizer and control. The increased in bulk density in untreated plots led to decrease in water stable aggregates, low water holding capacity and low yield of cucumber crop. Green manures applications increased soil organic carbon pool, improved topsoil physical properties and cucumber yield, while NPK chemical fertilizer had negative effects on these properties.

Macroaggregates Serve as Micro-Hotspots Enriched With Functional and Networked Microbial Communities and Enhanced Under Organic/Inorganic Fertilization in a Paddy Topsoil From Southeastern China.

Microbial communities of soil aggregate-size fractions were explored with molecular and networking assays for topsoil samples from a clayey rice paddy under long-term fertilization treatments. The treatments included no fertilizer (NF) as control, chemical fertilizer only (CF), chemical fertilizer with swine manure (CFM), and chemical fertilizer with rice straw return (CFS). Following a wet-sieving protocol, water-stable aggregates were separated into size fractions of large macroaggregates (L-MacA, >2,000 μm), macroaggregates (MacA, 2,000–250 μm), microaggregates (MicA, 250–53 μm), fine microaggregates (F-MicA, 53–2 μm), and fine clay (F-Clay, <2 μm). Mass proportion was 32.3–38.2% for F-MicA, 23.0–31.5% for MacA, 19.0–23.1% for MicA, 9.1–12.0% for L-MacA, and 4.9–7.5% for F-Clay, respectively. The proportion of MacA was increased, but F-Clay was reduced by fertilization, whereas the mean weight diameter was increased by 8.0–16.2% from 534.8 μm under NF to 621.5 μm under CFM. Fertilization affected bacterial 16S rRNA and fungal 18S rRNA gene abundance in F-MicA and F-Clay but not in aggregates in size larger than 53 μm. However, bacterial and fungal community α-diversities and community structures were quite more divergent among the fertilization treatments in all size fractions. Organic carbon and gene abundance of bacteria and fungi were enriched in both L-MacA and MacA but depleted in F-Clay, whereas microbial Shannon diversity was rarely changed by fraction size under the four treatments. L-MacA and MacA contained more bacteria of r-strategists and copiotrophs, whereas F-MicA and F-Clay were demonstrated with a higher abundance of K-strategists and oligotrophs. Guilds of parasitic and litter saprotrophic fungi were enriched in F-MicA but depleted in L-MacA. Furthermore, most of bacterial and fungal operational taxonomic units were strongly interacted in L-MacA and MacA rather than in MicA and F-Clay. Thus, MacA acted as micro-hotspots enriched with functional and networked microbial communities, which were enhanced with organic/inorganic fertilization in the rice paddy.

Effects of large-grained activated humic acid fertilizer on soil aggregates and organic carbon in apple orchard soil

The new large-grained activated humic acid fertilizer (LAF) can significantly reduce the amount of chemical fertilizer application and stable fruit yield. Understanding its impacts on soil aggregates and organic carbon is an important basis for revealing its role in driving soil structure of apple orchard. There were four LAF treatments: LAF1 (full fertilization, fertilization period and mass ratio (the same below), germination stage: fruit expansion stage: maturity stage=3:4:3), LAF2 (full fertilization, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF3 (fertilizer application reduction by 1/4, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF4 (fertilizer application reduction by 1/3, germination stage: fruit expansion stage: maturity stage=2:3:5); with no fertilization as control (CK). In a four-year pot experiment, we examined the composition, stabi-lity and organic carbon content of soil aggregates under different fertilization treatments. The results showed that: 1) compared with CK, each treatment of LAF increased the content of &gt;2 mm and 2-0.25 mm aggregate by 53.4%-77.5% and 12.3%-17.0%, respectively. The application of LAF significantly increased the content of soil water stable aggregates, and such effects were positively related with application amount. The content of soil water stable aggregate was the highest in the LAF1 treatment. 2) There was no significant difference in aggregate content of each particle size among LAF treatments, with the proportion of aggregate content of 2-0.25 mm particle size being the highest. 3) Compared with CK, all LAF treatments significantly increased the average weight diameter (MWD) and geometric mean diameter (GMD), and reduced the fractal dimension (D). LAF1 treatment had the highest MWD and GMD values, and had the strongest effect on the stability of soil aggregates. 4) Except for LAF4 treatment, the content of soil organic carbon in other LAF treatments was significantly higher than that in CK, and the content of soil organic carbon in LAF2 treatment was the highest. All LAF treatments increased the organic carbon content of soil aggregates with each particle size. LAF1, LAF2, and LAF3 treatments significantly increased the organic carbon of aggregates with particle size &gt;2 mm. Particle size &gt;2 mm had the highest contribution to the total organic carbon. The contribution rate of water stable large aggregate organic carbon to total organic carbon of LAF treatment was significantly higher than that of CK, which was all higher than 66.0%, and that of LAF1 treatment was the highest. In conclusion, the application of LAF enhanced the formation and stability of water stable aggregates and increased organic carbon content of aggregates in apple orchard soil, with the best performance of the full application. The application of LAF could be used as an effective measure to improve soil structure and fertility in apple orchard.

Effects of saline-water furrow irrigation on the stability of soil water-stable aggregates in cotton field

It is of great importance to explore the effects of saline-water furrow irrigation on soil water-stable aggregates for safe and efficient utilization of saline water resources. We conducted a long-term cotton experiment with six levels of saline-water furrow irrigation (1, 2, 4, 6, 8, 10 g·L-1) since 2006 and analyzed the variations of soil salinity and water-stable aggregates in the 10th and 15th years under saline irrigation. The results showed that soil salinity in the 0-30 cm layer at the ditch increased with increasing salinity level of irrigation water. There were significant differences between the 6, 8, 10 g·L-1 and 1 g·L-1 treatments. Soil salinity in each treatment increased gradually with increasing soil depth. Saline-water furrow irrigation tended to reduce the stability of soil water-stable aggregates. When the salinity level of the irrigation water was ≥6 g·L-1, the mass fraction of macroaggregates (&gt;0.25 mm), the mean weight diameter and geometric mean diameter of water-stable aggregates significantly decreased. In contrast, the fractal dimension and mean weight specific surface area increased significantly. The stability of soil water-stable aggregates decreased with soil depth in all treatments. Under the condition of saline-water furrow irrigation for several years, there was no accumulation of soil salinity and instability of water-stable aggregates in the 0-30 cm soil layer at the ditch with each passing year. With the irrigation scheduling of this study, saline-water furrow irrigation with salinity ≤4 g·L-1 did not affect soil salinity and water-stable aggregate stability of cotton field in this area.

О влиянии амплитуды вибрации на разрушение почвенных агрегатов при определении их водоустойчивости при ситовом анализе

The paper presents method to determine soil aggregates water stability. Its main stages are vacuuming of aggregates to eliminate the uncontrolled influence of trapped air on their destruction, subsequent saturation of aggregates with water in vacuum to values of soil moisture potential close to zero, and the use of vibration, to accelerate the destruction of aggregates. The influence of the vibration amplitude on the water stability of soil aggregates of the zonal series was studied using the developed method. It is shown that obtained curves have a general form for all the studied types of soil, a weak destruction of aggregates with vibration increase at the initial stage is replaced by a sharp acceleration of their destruction when the maximum value of the impact is reached. Despite the lower information content in comparison with traditional methods of sieving method, the proposed approach for assessing water stability has a noticeably higher performance and can be used as an express method for determining aggregate water stability and techniques for increasing it.

Evaluating Land Sustainability Indicators Through Structural Stability Changes In Deforested Land

Structural stability of soils is an important indicator for land sustainability because it controls the depth of topsoil and soil quality, particularly in deforested areas. The objective of this research was to evaluate the dynamics of soil structure across five common indigenous ecosystems (banana-, rubber-, and coffee-agroforests, Imperata cylindrica grassland, and secondary forest). Wet and dry sieving techniques were performed to assess aggregate size distribution and aggregate stability. The highest amount of water stable aggregates was observed in the I. cylindrica grassland and secondary forest at 55% and 53%, respectively. The greatest dry aggregate stability was found in rubber agroforest (78%), banana agroforest (77%) and secondary forest (74%). Both mean weight diameters and geometric mean diameters of aggregate in the soil profile of 30 cm were highest in agroforests compared to other ecosystems. Aggregate size distributions and their stability were positively correlated with soil organic C. The data showed a positive significant correlation between the mean weight diameter, geometric diameter, and soil organic carbon content. This study indicates that structural stability provides better indicator for soil quality improvement or degradation compared to soil organic C measurement. The dynamics of soil structure were relatively sensitive to cultivation practices. Therefore, soil aggregation is recommended to be used as soil quality indicator before the change of soil organic C can be detected.

Effects of economic fruit forest planting on the stability of red soil aggregates in the subtropical hilly area

The stability of aggregates is of great significance to evaluate water and soil environment in regions plan-ting economic fruit forest. We explored the effects of economic fruit forest types on the structure and stability of soil aggregates in the 0-50 cm soil layer from 5-year-old Amygdalus persica, Pyrus sorotina, Citrus reticulata, Camellia oleifera and Actinidia chinensis forests in the hilly area in northern Hunan. The content, distribution characteristics and stability indices of soil aggregates from each economic fruit forest were quantitatively analyzed by the Shavinov method. The results showed that most soil aggregates were mechanically stable, with a minimum content of 92.3%. After wet sieving, the size of water-stable aggregates in the soil from Camellia oleifera forest was mainly &gt;2 mm, accounting for 55.9% of the total aggregates. The 0.25-2 mm aggregates were the dominant particles in the A. persica, P. sorotina, C. reticulata and A. chinensis forest soils, with contributions higher than 43.6%. The mean weight diameter (MWD) and the geometric mean diameter (GMD) of soil aggregates for the five economic fruit forest types ranged from 1.10 to 3.19 mm and 0.61 to 2.28 mm, respectively. Furthermore, the percentages of soil aggregate destruction (PAD) and fractal dimension (D) were in the range of 2.9%-37.3% and 2.30-2.68, respectively. With the increases of soil depth, the stability of soil aggregates from A. persica, C. oleifera and A. chinensis forest soils became worse; MWD and GMD decreased by 1.7%-57.7% and 4.5%-65.8%, respectively; PAD and D increased by 0.4%-17.3% and 1.6%-11.1%, respectively. The effects of economic fruit forest types on the stability of soil aggregates decreased with increasing soil depth. Based on the stability indices, aggregate stability from five economic fruit forests followed the order of C. oleifera &gt; A. chinensis &gt; P. sorotina &gt; C. reticulata &gt; A. persica. The type of economic fruit forest improved the stability of soil structure mainly by affecting the content of large-size aggregates. In terms of improving the distribution and stability of soil aggregates, it was suggested that C. oleifera should be given the top priority as the economic fruit forest in the subtropical hilly area, followed by A. chinensis. Whereas A. persica planting might reduce the degree of soil agglomeration, thus, the protective measures of soil loss should be considered during planting. Our results could provide theoretical basis and application guidance for the development, utilization, and ecological management of economic fruit forests in subtropical hilly areas.

Effect of Long-Term Fertilization on Aggregate Size Distribution and Nutrient Accumulation in Aeolian Sandy Soil.

Soil aggregates are the material basis of soil structure and important carriers of nutrients. Long-term application of organic and inorganic fertilizers can affect the composition of soil aggregates to varying degrees, which in turn affects the distribution and storage of soil nutrients. We report the results of a 15-year long-term field-based test of aeolian sandy soil and used the wet sieve method to analyze the stability of water-stable aggregates, as well as the distribution characteristics of nutrients in different particle size aggregates. Our results show that long-term application of organic fertilizer (M3) and combined organic–inorganic treatments (NPK1-M1, NPK1-M2, and NPK1-M3) help to increase the amount of organic carbon, inorganic carbon, and cation exchange in the macro-aggregates, and the improvement rates are 92–103%, 8–28%, and 74–85%, respectively. The organic content of the fertilizers also promotes the formation of macro-aggregates, and the stability of aggregates increase from 0.24 to 0.45. In contrast, the application of inorganic fertilizers (NPK1, NPK2, and NPK3) has no marked effect on the formation and stability of macro-aggregates; the application of inorganic fertilizers can merely maintain the organic carbon content of the soil. Correlation analysis shows that the application of organic fertilizers and chemical (inorganic) fertilizers containing phosphorus and potassium can markedly increase the content and reserves of available phosphorus and potassium across all aggregate sizes, and there is a significant positive correlation between these parameters and the amount of applied fertilizer (p < 0.05). Aggregates of various sizes in aeolian sandy soils in arid areas have the potential for greater nutrient storage. Therefore, organic fertilizers can be used in the agricultural production process to improve soil structure and fertility.

Nutrient Characterization in Soil Aggregate Fractions with Different Fertilizer Treatments in Greenhouse Vegetable Cultivation

Fertilization affects the formation and stability of soil aggregate, as well as the nutrient status of soil aggregate. However, the potential effect of compost on soil aggregate and its nutrient characteristics is still unclear. In view of this, we conducted a greenhouse vegetable cultivation experiment to evaluate soil water-stable aggregate (WSA) and its stability indices and aggregate nutrient stoichiometry characteristics at 0 to 20 cm soil depth with four treatments: (1) no fertilizer (CK), (2) chemical fertilizer (CF), (3) organic fertilizer (OF), and (4) chemical fertilizer plus organic fertilizer (CO). The results showed that the proportion of the 2 to 0.25 mm fraction was the greatest, followed by 0.25 to 0.053 mm, which accounted for 41.83 to 49.53% and 28.60 to 31.88% by weight, respectively. The mean weight diameter (MWD) value and the proportion of the &gt;0.25 mm fraction in the CF, OF, and CO treatments were significantly higher than in the CK treatment. Within the fertilization treatments, the MWD and the proportion of the &gt;0.25 mm fraction in the CO were significantly higher than those in CF and OF. Among all the aggregates, the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents were the highest in the fraction of 0.25 to 0.053 mm. The CF, OF, and CO treatments significantly increased the SOC, TN, and TP contents compared with the CK treatment. The SOC content of fractions &gt;2 mm and 0.25 to 0.053 mm in the CO treatment was significantly higher than that of the CF and OF treatments, and the TN and TP contents in all the aggregates (except &lt; 0.053 mm) were the highest in the CO treatment. The SOC, TN, and TP contents in the 2 to 0.25 mm and 0.25 to 0.053 mm components contributed greatly to the soil SOC, TN, and TP reserves. There was no noticeable difference in the nutrient stoichiometry of the soil aggregate between the different treatments. Redundancy analysis (RDA) revealed that the soil physicochemical factors, including SOC, TN, TP, and pH, significantly explained the stability of the soil aggregate. To summarize, chemical fertilizer combined with organic fertilizer positively affected the stability and nutrient accumulation of soil aggregates in greenhouse dryland.

Characterization of Mollisols after Long-Term N Fertilization at Successive Rates in Continuous and Rotated Corn Systems

Modern agricultural systems rely on inorganic nitrogen (N) fertilization to enhance crop yields, but its overuse may negatively impact soil properties. Soil properties to a depth of 90 cm were studied after 36 years of inorganic N fertilization at successive rates of 0, 202, and 269 kg N ha−1 (N0, N202, and N269) in continuous corn production [Zea mays L.] (CCC), and the corn (Cs) and soybean [Glycine max (L.) Merr.] (Sc) phases of a corn-soybean (CS) rotation. Experimental plots were arranged as a split-plot in a randomized complete block design with three replications. High levels of N fertilization under CCC acidified the topsoil (N0 pH 6.6 vs. N269 pH 4.9), and increased the nitrate level eight-fold compared to unfertilized controls. Under CCC, N0 had more than twice the available phosphorus level (P) and 40% more potassium (K) than the fertilized soils. Though treatments did not impact the soil organic carbon (SOC) content, water aggregate stability (WAS) decreased during the soybean phase of the rotated treatment (Sc) when compared to CCC. Fertilization affected soil bulk density (BD), which decreased by 5% from N0 to N269 across rotations. Averaged since the start of the study, corn yields increased by 60% with N fertilizer use compared to the unfertilized controls (N0). The corn grain yield benefited from the rotation with soybeans rendering 17% more grain yield in Cs than in CCC. Yet this benefit rose to 45% more grain yield on average, when no N fertilizer was used in Cs. Our results showed that there are important trade-offs with N fertilization and long-term use of corn monocultures, as its long-term use, even in the fertile and resilient soils on the Midwestern U.S., has led to P and K depletion, soil acidification, and potentially exacerbated N losses to the environment.

Integration of pelleted biosolids with cover crops for improving soil properties

AbstractMeasuring and assessing soil properties is critical for understanding how changes in agronomic practices affect the capability of soil to support cropping systems. A field study was conducted on a Marietta silt loam soil at the Plant Science Center at Mississippi State University to determine the effects of pelleted biosolids (PBS) relative to poultry litter (PL) and inorganic N fertilizer applied to corn (Zea mays L.) and cotton (Gossypium hirsutum L.) in the presence of winter wheat (Triticum aestivum L.) cover crop (WCC) and winter fallow (WF) on soil properties. Experimental design was a split‐plot randomized complete block with three replications. The whole plots were WCC and WF and the subplots were fertilization. Fertilization treatments included PBS and PL at 11.2 Mg ha–1 and 6.7 Mg ha–1 applied to corn and cotton, a one‐time single application at 37 Mg PBS ha–1 to corn in 2016, inorganic N fertilizer at the recommended rate, and an unfertilized control. Soil cores were collected after harvest and analyzed for nutrient concentrations, water stable aggregate (WSA), and enzyme activities. The WCC reduced bulk density (ρb) and penetration resistance (PR) and increased soil total C (TC), WSA, and infiltration rate, as compared with winter fallow (WF). Relative to inorganic N fertilizer, application of PBS decreased soil ρb and PR by 3 and 20%, respectively, and increased soil TC, WSA, and infiltration by 19, 23, and 45%, respectively. A combination of PBS and WCC improved soil physical and chemical properties under southeast agroecosystems.