Water-stable Macroaggregates Research Articles

Continuous plastic-film mulching increases soil aggregation but decreases soil pH in semiarid areas of China

Plastic-film mulch is a globally applied agricultural practice. However, its effects on soil aggregation and pH have been hardly studied. We assessed the effects of plastic-film mulch on soil aggregate water-stability and pH in fields used for maize (Zea mays L.) production, at two sites in a cold semiarid environment, China. Four treatments were used: (i) no plastic-film mulch and no straw incorporation, (ii) plastic-film mulch only, (iii) straw incorporation only, and (iv) straw incorporation plus mulch. Seven years after continuous treatment application, the use of plastic-film mulch increased the proportion of water-stable macroaggregates (>0.25mm) in the top 15-cm soil layer by 16–28%, across sampling times and sites. Straw incorporation similarly increased the proportion of water-stable macroaggregates. However, the effects of mulch, on increasing the mean weight diameter of aggregates were greater in non-straw-incorporated soils than in straw-incorporated soils, and vice versa. Soil bulk density in the top 15-cm soil layer marginally increased in the mulched treatments, relative to the non-mulched treatments, while it decreased in straw-incorporated treatments. In addition, there was a decrease in soil pH, by 0.19–0.54 units, in the mulched, relative to the non-mulched soils. Combining our previous results, we suggested that increases in maize root growth and microbial activity were linked to the increased soil aggregation while accumulation in soil nitrate resulting from the stimulated soil nitrogen mineralization was responsible for the marginally decreased soil pH in the plastic-film mulched relative to the non-mulched soils, due to increased soil hydrothermal conditions.

Influence of tillage practices and straw incorporation on soil aggregates, organic carbon, and crop yields in a rice-wheat rotation system.

In this study, a fixed-site field experiment was conducted to study the influence of different combinations of tillage and straw incorporation management on carbon storage in different-sized soil aggregates and on crop yield after three years of rice-wheat rotation. Compared to conventional tillage, the percentages of >2 mm macroaggregates and water-stable macroaggregates in rice-wheat double-conservation tillage (zero-tillage and straw incorporation) were increased 17.22% and 36.38% in the 0–15 cm soil layer and 28.93% and 66.34% in the 15–30 cm soil layer, respectively. Zero tillage and straw incorporation also increased the mean weight diameter and stability of the soil aggregates. In surface soil (0–15 cm), the maximum proportion of total aggregated carbon was retained with 0.25–0.106 mm aggregates, and rice-wheat double-conservation tillage had the greatest ability to hold the organic carbon (33.64 g kg−1). However, different forms occurred at higher levels in the 15–30 cm soil layer under the conventional tillage. In terms of crop yield, the rice grown under conventional tillage and the wheat under zero tillage showed improved equivalent rice yields of 8.77% and 6.17% compared to rice-wheat double-cropping under zero tillage or conventional tillage, respectively.

Newly-reclaimed alfalfa forage land improved soil properties comparison to farmland in wheat–maize cropping systems at the margins of oases

The increased demand for economic benefits has led to an extensive conversion of native sandy steppe at the margins of oases into alfalfa forage land and farmland in northwestern China. Understanding the impacts of alfalfa forage land and farmland on soil properties is crucial for maintaining the stability of oases. However, the effect of this newly-reclaimed alfalfa forage land and farmland on soil properties remains unknown. Native sandy steppe and 10-year-old alfalfa forage land and farmland (both converted from native sandy steppe) were chosen for use in this study. It was shown that the conversion of native sandy steppe to alfalfa forage land and farmland significantly increased the amounts of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP). Over the period of 10 years, the sequestrations of SOC, TN and TP were almost the same for both alfalfa forage land and farmland. After the period of 10 years, the soil water holding ability, water stable macro-aggregates aggregates, soil microbial biomass C (MBC) and microbial biomass N (MBN) contents and urease, β-glucosidase, and alkaline phosphatase activities were all significantly higher in the alfalfa forage land than in the farmland. These results suggest that the newly-reclaimed alfalfa forage land is more propitious for amending soil environments than farmland, thus it should be widely used to improve the soil properties at the margins of oases.

Decrease of soil organic matter stabilization with increasing inputs: Mechanisms and controls

Crop residue addition is a way to increase soil organic matter (SOM) level in croplands. However, organic matter input and SOM stocks are not linearly related. Consequently, adding high amounts of residues, such as straw, may increase SOM to only a small extent, and an alternative use of the residues may be justified. The objective of this study was to test how the level and type (above- or belowground) of residue addition affect SOM stabilization. We hypothesise that (1) root residues will be mineralised slower than leaf and stalk residues, (2) soil aggregate formation will increase with high additions, and (3) wheat residue addition will induce positive priming, with the magnitude depending on the residue level and type. Homogeneously 13C-labelled wheat residues (leaves, stalks, roots) were added to a silt-loam soil at levels of 1.40 and 5.04gDMkg−1 and CO2 release and δ13C signature were measured over 64days at 20°C. Water-stable macroaggregates (>250μm), microaggregates (53–250μm) and silt plus clay size fractions (<53μm) were separated and 13C incorporation from residue was quantified in each fraction after 64days. Aggregate formation generally increased with added residue amount, but the proportion of residues occluded within aggregates decreased with increasing addition level. The occlusion of residues from aboveground biomass was more reduced with addition level than that of roots. Residue mineralisation increased with the addition level, but this increase was less for roots compared to stalks and leaves. Priming effects were similar between residue types and mainly depended on the added amount: SOM mineralisation increased by 50% and 90% at low and high addition levels, respectively. We conclude that the proportion of residues physically protected within aggregates decreases and priming effects increase with increasing C input leading to decreasing rate of long-term C stabilization within SOM by increasing residue addition.

Impact of flue gas desulfurization gypsum and lignite humic acid application on soil organic matter and physical properties of a saline-sodic farmland soil in Eastern China

Appropriate land management is important for improving the soil quality and productivity of the saline-sodic farmland. A recent study has revealed that flue gas desulfurization (FGD) gypsum and lignite humic acid application enhanced the salt leaching and crop production. The purpose of this study was to investigate the effects of applied FGD gypsum and lignite humic acid (powder) on the soil organic matter (SOM) content and physical properties. This study was based on a field experiment of five consecutive rapeseed-maize rotations in a saline-sodic farmland soil (Aquic Halaquepts) at coastal area of North Jiangsu Province, China. The soil is sandy clay loam texture with pH of 8.43 and clay content of 185 g kg−1. Six treatments included three FGD gypsum rates (0, 1.6, and 3.2 Mg ha−1) and two lignite humic acid rates (0 and 1.5 Mg ha−1). The amendments were incorporated into 0–20 cm soil depth manually every year. Soil samples were collected from each treatment and analyzed for soil organic matter, water-stable aggregates (wet sieving method), bulk density (clod method), water retention capacity (pressure plate apparatus), total porosity (calculated from bulk density and particle density), and microporosity (calculated from water content at 0.01 MPa). After 5 years, the SOM and soil physical properties were significantly (P < 0.05) affected by the application of FGD gypsum and lignite humic acid, especially at the 0–20 cm soil depth. The highest amount of SOM with best soil physical condition was observed in the field which was treated with FGD gypsum at 3.2 Mg ha−1 with lignite humic acid, and the SOM, total porosity (TP), microporosity (MP), mean weight diameter (MWD), water-stable macroaggregate (WSMA), and available water content (AWC) were increased by 22.8, 6.34, 23.2, 48.1, 55.5, and 15.8 %, respectively, while the bulk density (BD) was decreased by 5.9 % compared to no amendments applied. The generalized linear regression analysis showed that the SOM explained 42.9, 55.0, 48.5, and 54.2 % of the variability for BD, MWD, WSMA, and MP, respectively. This study illustrates the benefits of applying FGD gypsum and lignite humic acid for increasing the soil organic matter content and improving the soil physical properties and suggests a great potential for ameliorating saline-sodic farmland soil (Aquic Halaquepts) by using combined amendment of FGD gypsum with lignite humic acid.

Plant versus microbial controls on soil aggregate stability in a seasonally dry ecosystem

The formation of water-stable macroaggregates in soil is beneficial for many reasons, including carbon (C) sequestration, nutrient retention, and erosion control. A mix of biotic (e.g., plant C input, microbial activity) and abiotic factors (e.g., water, mineral interactions) contribute to form macroaggregates. However, in order to better model and manage soil macroaggregates, we need to know more about the relative contributions of these mechanisms. Previous experiments to separate microbial and abiotic mechanisms have been hampered by the need to add sterilant dissolved in water, thus limiting our ability to draw conclusions about the role of soil moisture in controlling aggregation and preventing conclusions about dry soil. Our first goal was to quantify the contribution of plant growth (and fresh plant C inputs) by continuously removing plants for 2years in a seasonally dry grassland. Our second goal was to quantify microbial vs. abiotic contributions to macroaggregate formation under a range of soil moisture conditions by using chloroform vapor to sterilize soil without adding water or destroying soil structure. In the field, regardless of dry season length, removing plants reduced the average size of soil aggregates by 22–33%, which was primarily driven by a shift from large macroaggregates (2–9mm diameter) to small macroaggregates (0.25–2mm). In the laboratory, in sterile soils macroaggregate production increased with the moisture content. The resulting physicogenic aggregates appeared planar and angular at both macro- and micro-scales. In contrast, biogenic aggregates were formed most at intermediate moisture levels and were spherical. Our results suggest that—even in dry climates—soil macroaggregates are preserved by the presence of even dead plant roots, but are engineered by live microbes.

Increases in Soil Aggregation Following Phosphorus Additions in a Tropical Premontane Forest are Not Driven by Root and Arbuscular Mycorrhizal Fungal Abundances

Tropical ecosystems have an important role in global change scenarios, in part because they serve as a large terrestrial carbon pool. Carbon protection is mediated by soil aggregation processes, whereby biotic and abiotic factors influence the formation and stability of aggregates. Nutrient additions may affect soil structure indirectly by simultaneous shifts in biotic factors, mainly roots and fungal hyphae, but also via impacts on abiotic soil properties. Here, we tested the hypothesis that soil aggregation will be affected by nutrient additions primarily via changes in arbuscular mycorrhizal fungal (AMF) hyphae and root length in a pristine tropical forest system. Therefore, the percentage of water-stable macroaggregates (> 250µm) (WSA) and the soil mean weight diameter (MWD) was analyzed, as well as nutrient contents, pH, root length and AMF abundance. Phosphorus additions significantly increased the amount of WSA, which was consistent across two different sampling times. Despite a positive effect of phosphorus additions on extraradical AMF biomass, no relationship between WSA and extra-radical AMF nor roots was revealed by regression analyses, contrary to the proposed hypothesis. These findings emphasize the importance of analyzing soil structure in understudied tropical systems, since it might be affected by increasing nutrient deposition expected in the future.

Temperature sensitivity of carbon decomposition in soil aggregates along a climatic gradient

Global warming affects the carbon (C) pools in terrestrial ecosystems, accelerating biological processes that feed back into the phenomenon of climate change. Globally, grassland ecosystems accumulate large quantities of organic C into soils and are considered a corner stone for global warming mitigation. The aim of this study was to evaluate the temperature sensitivity of C decomposition in different soil aggregate fractions in grassland ecosystems across a north-south latitudinal gradient in Chile. Soil samples were collected from Mediterranean semi-arid (MSA; 32°31, to 34°19, south latitude), temperate semi-oceanic (TSO; 35°36, to 36°27, south latitude), temperate oceanic (TO; 40°36, to 43°03, south latitude) and subpolar semi-oceanic (SPSO; 43°57, to 47°40, south latitude) climate zones, and water-stable macroaggregates (250-2,000 µm) and free microaggregates (50-250 µm) were isolated. Two experiments were performed using short-term incubations (14 days). First, absolute soil respiration and specific soil respiration from isolated aggregates were assessed at 20 °C, and second, the isolated aggregates were incubated at different temperature levels (20-30 oC for MSA and TSO; 10-20 oC for TO and SPSO) to quantify the energy of activation (Ea) and temperature sensitivity (Q10). In general, the results do not provide evidence of differences between soil aggregate fractions in any of the evaluated parameters, but the soils differed across the latitudinal gradient. High absolute respiration rates and specific respiration, which were related to high grassland productivity, were observed in soils from TO and SPSO zones. The Q10 values demonstrated a strong positive correlation with annual precipitation, so C decomposition in soils from zones with high precipitation exhibits increased temperature sensitivity.

Assessment of Long-Term Compost Application on Physical, Chemical, and Biological Properties, as Well as Fertility, of Soil in a Field Subjected to Double Cropping

The aim of this article was to assess the influence of long-term application of compost on the physical, chemical, and biological properties, as well as the fertility, of soil in a field subjected to double cropping (paddy rice and barley), mainly by integrating previous studies of the effects of compost and manure on soil qualities. Continuous compost application, especially at a high level (30 Mg·ha-1·y-1), into the double cropping soils increased the activities of organic C-, N-, and P-decomposing enzymes and the contents of organic C, total N, and microbial biomass N, as well as the cation exchange capacity, thereby contributing to the enhancement of soil fertility. Also, the compost application increased the degree of water-stable soil macroaggregation (>0.25 mm), which was correlated significantly (r > 0.950, p < 0.05) with the contents of hydrolyzable carbohydrates (with negative charge) and active Al (with positive charge), and resulted in the modification of soil physical properties. Furthermore, the application increased the amount of soil organic matter, including humic acid with a low degree of darkening and fulvic acid, and contributed to C sequestration and storage. Physical fractionation of soil indicated that about 60% of soil organic C was distributed in the silt-sized (2 - 20 μm) aggregate and clay-sized (<2 μm) aggregate fractions, while about 30% existed in the decayed plant fractions (53 - 2000 μm). The results obtained unambiguously indicate that long-term application of compost can improve soil qualities in the field subjected to double cropping, depending on the amount applied.

Effects of long-term (23 years) mineral fertilizer and compost application on physical properties of fluvo-aquic soil in the North China Plain

The influence of compost and mineral fertilization on soil organic carbon (SOC) and physical properties varied greatly in previous studies because of differences in site conditions such as climate and soil. This study was conducted as a long-term (1989–2012) field experiment to evaluate the effects of mineral fertilization and compost application on SOC content and some physical properties of an intensively cultivated sandy loam soil in the North China Plain. The experiment consisted of seven treatments: organic compost (OM); half organic compost plus half mineral fertilizer NPK (1/2OM1/2NPK); mineral fertilizer NPK (NPK); mineral fertilizer NP (NP); mineral fertilizer PK (PK); mineral fertilizer NK (NK); and unfertilized control (CK), each with four replicates. Relative to CK, the SOC content was higher in all of the compost and mineral fertilizer treatments, but increments in SOC under the compost application treatments were higher than mineral fertilization application. Compost application (OM, 1/2OM1/2NPK) decreased soil bulk density and increased total porosity significantly in comparison with that in the CK plots. Soil bulk density and total porosity for the mineral fertilization treatments, except NP, did not significantly differ from CK. The lowest penetration resistance at 0–20cm soil depth was observed in the NK plots, and the highest penetration resistance was found in the CK plots. Compost application increased the total amount of water-stable macro-aggregates (>0.25mm); however, MWD was not significantly affected by compost application. The MWD in the NK treatment was lower than in CK by 0.2mm, while its variation among NPK, OM, 1/2OM1/2NPK, NP, PK, and CK was not significant. The compost- and mineral fertilizer-treated soil had 34.6–91.7% higher volume of macropores than the CK soil. The OM and 1/2OM1/2NPK-treated soil had a significantly higher proportion of small pores (<3.3μm), and the mineral fertilizer-treated soil did not differ from CK. The hydraulic conductivity in the balanced fertilization plots (OM, 1/2OM1/2NPK, NPK) tended to be higher than in the unbalanced fertilization treatments (NP, PK, and NK) and CK. The results indicated that supplementation with organic manure such as compost is more beneficial to enhance soil fertility and maintain the sustainability of crop production in the North China Plain.

Fertilization and carbon sequestration

DOI:10.15414/afz.2015.18.03.56–62 Received 20. February 2015 ǀ Accepted 6. May 2015 ǀ Available online 14. October 2015 The effect of fertilization on the dynamic change of soil organic matter (SOM) in loamy Haplic Luvisol was studied. In 2008-2011, soil samples were taken from following treatments: 1. C– non-fertilized, 2. PR+NPK – plant residues together with NPK fertilizers, and 3. NPK – NPK fertilizers. The results showed that the content of soil organic carbon in water-stable micro-aggregates (SOC in WSA mi ) increased by 11% and by 13% in PR+NPK and NPK treatments, respectively. The ratios of SOC in WSA mi /SOC in bulk soil in the NPK fertilized treatment and in PR+NPK were 14% and 4% higher than in the non-fertilized treatment, respectively. Overall the ratios of SOM in WSA/SOM in bulk soil were higher in macro-aggregates than micro-aggregates. In fertilized treatments, the statistical significant changes in dynamics of labile carbon in water-stable macro-aggregates (C L in WSA ma ) and in WSA ma 0.5-3 mm were observed. In fertilized treatments (PR+NPK and NPK) there were observed significant decrease of the C L in WSA ma . The ratios C L in WSA mi also WSA ma /C L in bulk soil decreased due to ploughed plant residues together with NPK fertilizers, the ratio of C L in WSA ma /C L in soil decreased due to added only NPK fertilizers also.

Changes in Soil Structure and Soil Organic Matter Due to Different Severities of Fire

Abstract The effect of different fire severity on the changes of the soil organic matter (SOM) and soil structure was evaluated. Soil samples were collected (May 2010) in the locality of Nitra-Dražovce (Slovakia) from the following plots: 1) control (unburned place), 2) low severity of fire and 3) higher severity of fire. The results showed that the content of water-stable microaggregates (WSAmi) increased by 20% in the area with a low severity of fire, but on the other hand, it decreased by 42% in the area with the higher severity of fire in comparison to control. The higher severity of fire resulted in a decrease of smaller size fractions of water-stable macroaggregates (WSAma) (0.5−0.25) and a low severity of fire resulted in the decrease of WSAma 2−0.5 mm. On the other hand, the content of WSAma in the size fraction &gt;5 mm was higher by 54% and by 32% in the lower and higher severity of fire, respectively, than in unburned soil. The higher severity of fire had a more positive effect on increases of the structure coefficient and coefficient of aggregate stability, as well as on the decrease of the vulnerability coefficient compared to the low severity of fire. After burning, the contents of soil organic carbon (Corg) and labile carbon were significantly increased by the severity of fire. However, the low severity of fire affected more markedly the increase of hot water-soluble and cold water-soluble carbon than the higher severity of fire. After burning and due to the severity of fire, both the carbon of humic and carbon of fulvic acids ratios and SOM stability increased. The parameters of SOM due to fire significantly increased also in WSA with the least changes in WSAmi. The results showed that a low severity of fire increased Corg mainly in WSAma &gt;2mm and WSAmi, whereas high severity fire increased Corg content in the smaller fraction of WSAma.

Effect of greenhouse soil management on soil aggregation and organic matter in northeast China

The effect of greenhouse soils on soil aggregation and soil organic carbon (SOC) cycling should be evaluated to maximize the benefits of solar greenhouses rationally. The relationship between aggregate stability and SOC fractions was investigated during a long-term greenhouse experiment for 16years in Shenyang, China. Wet-sieving method was used to determine aggregate size distribution, water-stable aggregates, and mean weight diameter (MWD) as indices of soil aggregate stability. SOC fractions were also determined. The stability of macroaggregates decreased within 5years of converting open vegetable fields to greenhouses, and a similar trend for MWD was observed. The stability of microaggregates also decreased. LF250 carbon in greenhouse soils was correlated with the amount of 2–0.25mm size classes (r=0.984⁎⁎). As a result, a labile SOC existed in macroaggregates and was susceptible to loss. Positive correlations were also determined between water-stable microaggregates and intra-microaggregate particulate organic matter (r=0.991⁎⁎), between water-stable macroaggregates and intra-microaggregate particulate organic matter within macroaggregates (r=0.998⁎⁎), and between intra-microaggregate mineral-associated organic matter within macroaggregates (r=0.971⁎⁎). This result indicated that greenhouse soil management significantly affected the stability of aggregation and the cycle of soil organic matter.

Water stability of soil aggregates and their ability to sequester carbon in soils of vineyards in Slovakia

Soil water-stable aggregation is an important process for carbon sequestration and is a key factor controlling soil sustainability and resilience; therefore, the objectives of the present study were to (1) evaluate the differences in soil organic matter state, its specific and labile fractions and their importance in the formation of water-stable aggregates in vineyard soils differing in their genesis and texture under different soil management (vineyard rows – tilled and grassed in-between strips), and (2) estimate the ability of the vineyard soils to sequester soil organic carbon (SOC) into water-stable macro-aggregates (WSAma). The results showed that the WSAma content of the soils ranged from 47% to 97%. Soils with grasses had a higher SOC and labile carbon (CL) contents than the bulk soil and, as a result, the higher total WSAma content. Soils ranged in a decreasing order in their ability to sequester SOC and CL from bulk soil to WSAma: Haplic and Stagni-Haplic Luvisols > Calcaric Fluvisol = Rendzic Leptosol > Haplic and Luvi-Haplic Chernozem > Dystric and Eutric Cambisols. Our results showed that the maximum ratio of SOC content in WSAma to that in bulk soil was 1.0 at the maximum WSAma content regardless of the soil type. An increase in the ratio above this threshold value (1.0) resulted in a decrease in WSAma content.

Effects of no-tillage systems on soil physical properties and carbon sequestration under long-term wheat–maize double cropping system

A thorough assessment of changes in soil quality associated with soil management practices is vital for the selection and establishment of sustainable agricultural management. The winter wheat (Triticum aestivum L.)–maize (Zea mays L.) double cropping system was used to study the integrated effects of a 9-year-old tillage coupled with fertilization on soil carbon sequestration and other physical properties in the Yellow River Delta (YRD). Three tillage systems were selected: no-tillage with straw cover plus recommended urea nitrogen rate (NTS), no-tillage with straw removed and manure applied plus recommended urea nitrogen rate (NTM), and conventional tillage with straw removed plus conventional urea nitrogen application rate (CT). There were three replicates of each treatment organized in a randomized block design. NTS and NTM treatments were found to result in a slightly decrease in the soil bulk density (BD), and significantly increased the proportion of water stable aggregates (WSA) (>2mm), as well as the water infiltration capacity. The proportion of water stable macroaggregates (>0.25mm), the mean weight diameter (MWD) and the geometric mean diameter (GMD) of aggregates in the 0–20cm layer were unchanged by NTS and NTM. The total soil organic carbon (SOC) stock at a depth of 0–60cm was not significantly different among the treatments. Both aggregate-associated SOC concentration and stocks (0–5cm) were significantly greater for NTS and NTM compared with CT, while CT led to a greater OC accumulation in the 20–60cm soil layer compared with NTS and in the 10–20cm compared with NTM. The mesoaggregate fraction (2–0.25mm) and its associated OC pool accounted for the highest percentages in the whole soil profile under the CT treatment. The NT system was found to have a positive effect on the investigated soil physical properties and increase soil carbon content in the soil surface layer. The CT system in conjunction with the wheat–maize double cropping system, however, improved soil aggregation in the soil profile (0–60cm) and also maintained a higher fraction of SOC in the subsoil compared with the NT systems.

POTENCIAL DE INÓCULO MICORRÍZICO E IMPORTÂNCIA DO COMPRIMENTO DO MICÉLIO PARA A AGREGAÇÃO DE SOLOS DE AMBIENTE FLUVIAL

Os fungos micorrízicos arbusculares (FMAs) desempenham importante papel nos ecossistemas naturais pelo seus impactos na nutrição vegetal e estrutura do solo. O objetivo deste estudo foi determinar o potencial do inóculo micorrízico e a relação do comprimento do micélio micorrízico (CMM) dos FMAs na agregação de solos de ambientes fluviais. Foram realizadas coletas em áreas de ambiente fluvial da bacia hidrográfica do rio Itajaí-Açu, entre os municípios de Gaspar e Navegantes, em Santa Catarina. Oito áreas foram amostradas em três classes de solos, sendo elas: Cambissolo (C), Gleissolo (G) e Organossolo (O). Nos solos coletados, foram avaliadas as seguintes variáveis: potencial de inóculo micorrízico, número de esporos, CMM e análise dos atributos físicos e químicos do solo. A porcentagem de colonização micorrízica da Brachiaria brizantha no ensaio do potencial de inóculo variou de 13,8 a 55,3 % e nenhum padrão foi observado de acordo com a classe de solo. O CMM no solo variou de 10,48 a 44,67 mg g-1. O número de esporos em 100 cm3 de solo variou de 2,4 a 80. Foi observada correlação negativa entre o CMM e a proporção de macroagregados estáveis em água e correlação positiva entre CMM com microagregados. Este trabalho demonstrou que os solos da bacia do rio Itajaí-Açu possuem potencial de inóculo micorrízico suficiente para iniciar a colonização das raízes das plantas em curto período de tempo, o que pode ser importante facilitador no crescimento de espécies arbóreas usadas no processo de recuperação desses ambientes.

Long-term Effect of Organic Manures and Biofertilizers on Physical and Chemical Properties of Soil and Productivity of Rice-Wheat System

A field experiment was conducted at the research farm of Indian Agricultural Research Institute, New Delhi on a sandy clay-loam soil (Typic Ustochrept) starting from Kharif-2003 under organic amendments to rice-wheat cropping system. The experiment was laid out in a randomized block design with three replications and six treatments in a set. The treatments consisted of control (T1), farmyard manure (FYM) (T2); green manure (GM) (T3); GM+biofertilizers (B) (T4); GM+FYM (T5); and GM+FYM+B (T6). In this study, the effect of organic amendments were evaluated on some physical soil properties and yield of the respective system by sampling the soil from three depths (0–15, 15–30 and 30–60 cm) at the end of Rabi 2011–2012. The results of the study revealed that the plots where, farm yard manure (FYM) was incorporated along with green manure (GM) and biofertilizer (B), the yield of rice and wheat had substantially improved. The combination of B with GM+FYM had not only led to better soil bulk density but even prove superior to FYM alone or GM alone. Soil aggregation was significantly affected by organic amendments; particularly mean weight diameter (MWD) and geometric mean diameter (GMD) were increased to a tune of 73.5% and 34.6% over control in 0–15 cm soil layer. The water stable macroaggregate (WSMA)>0.25mm ranged from 54.60% under control to 71.27% under T6 in the surface soil (0–15 cm). The combined applications of FYM along with GM and B showed the highest contents of available N, P, K and S in soil. It is thus certain that the cumulative effect of GM+FYM+B proved to be the one that leads to increased productivity as well as increased soil physical properties.

Effect of Carbonates and Bivalent Cations and Their Relationships with Soil Organic Matter from the View Point of Aggregate Formation

Abstract The effect of carbonates on soil structure has not been sufficiently studied yet, despite the fact that in the literature their positive impact is mentioned mostly. Carbonates are the source of bivalent cations in soil solution and may be involved in stabilization of the aggregates, because negatively charged organic materials can be adsorbed onto the surface of clay by bivalent or polyvalent cations. We studied the effect of carbonates and bivalent cations and their relationships with soil organic matter (SOM) from the point of view of aggregate formation. The studies were carried out in several fields located on loamy Calcaric Chernozem, loamy Haplic and Mollic Fluvisols. The results showed that between exchangeable Mg2+ and water-stable macro-aggregates (WSAma) in size fractions &gt;2 mm, positive correlations were found; however, the content of Mg2+ negative correlated with the contents of WSAma in &lt;1 mm fractions as well as with waterstable micro-aggregates (WSAmi). The threshold limit for Mg2+ content for the formation of water-stable macro-aggregates was at 11.5 cmol/kg if all loamy soils were assessed together. A further increase resulted in a lower content of WSAma. If all investigated soils were assessed separately, these results did not enable us to distinguish the maximum formation of WSAma by Mg2+ in individual soils. We observed a positive correlation between the sum of basic exchangeable cations (SBC) as well as between cation exchange capacity (CEC) and larger size fractions of WSAma &gt;2 mm; however, between SBC as well as CEC and smaller size fractions of WSAma &gt;1 mm and WSAmi negative correlations were observed. Statistically significant negative correlations were observed between SOM content in WSA and carbonate content, and this effect was stronger in relation to the labile carbon. There were also positive correlations between SOM in WSA and SBC and CEC found if all loamy soils were assessed together.

Soil crust in agricultural land

DOI: 10.15414/afz.2014.17.04.109–114 Received 5. June 2014 ǀ Accepted 1. October 2014 ǀ Available online 24. November 2014 We evaluated the effects of exogenous and endogenous factors on the formation of soil crust in arable soils ofSlovakia. Soil samples for determination of selected soil organic matter parameters, physical properties – particularly soil crust, were collected from localities Dražovce, Bucany and Jacovce (different soil – climatic conditions on each site) in spring 2012. The results showed that organic fertilization decreased the formation and thickness of soil crust. According to the susceptibility to crust formation, studied soils were ranged in a decreasing order: Calcaric Chernozem > Stagni-Haplic Luvisol > Rendzic Leptosol > Mollic Fluvisol. The thickness of soil crust significantly depended on cultivated crops. The most favourable value of index of crusting was calculated in the field with grown spring barley, following by pea < oil rape < winter wheat. We determined negative correlation between clay and index of crusting (r=-0.880, P≤0.01). Higher formation of soil crust was determined in soil with higher content of water-stable micro-aggregates (r=0.799, P≤0.05) and smaller size fractions of water-stable macro-aggregates in size fractions 0.25-0.5 mm(r=0.865, P≤0.01). Higher content of soil organic matter of rather stabile than labile form resulted to reduction of crust thickness as well as decreased the index of crusting. Keywords : index of crusting, soil structure, soil organic matter, soil types, organic fertilization, crops

Surface soil quality in five midwestern cropland Conservation Effects Assessment Project watersheds

Soil quality (SQ) assessment is a proactive process for evaluating soil and crop management effects on biological, chemical, and physical indicators of soil health. Our objectives were to evaluate several SQ indicators within five Agricultural Research Service (ARS) experimental watersheds (WS) and determine if those indicators were affected by manure, tillage, or crop rotation histories. Ten soil quality indicators were measured within each of 600 0 to 5 cm (0 to 2 in) depth and 398 5 to 15 cm (2 to 6 in) depth increment samples, evaluated statistically, and then scored using the Soil Management Assessment Framework. Except for soil organic carbon (C) at both depth increments or microbial biomass C and β-glucosidase within the 5 to 15 cm increment, the indicators showed significant WS differences. Except for surface soil-test phosphorous (P), Soil Management Assessment Framework indicator scores and overall soil quality index values also showed significant (p ≤ 0.05) WS differences. Microbial biomass C was significantly affected by crop rotation at both sampling depths and by WS within the surface 5 cm. β-glucosidase was significantly affected by all four factors (WS, manure, tillage, and crop rotation) and their interactions within the 0 to 5 cm increment. The water-stable macroaggregate indictor within the 0 to 5 cm increment and within the 5 to 15 cm increment, however, were not significantly different for the tillage and manure application treatments, respectively. Our study showed that the ARS Conservation Effects Assessment Project (CEAP) watersheds provided a moderately controlled example that watershed-scale monitoring of soil quality is feasible and should be used to monitor soil health and/or conservation program effectiveness.