Loss Of Soil Organic Matter Research Articles

Physico-Chemical Properties of Wetland Soils Affected by Crude Oil Spillage in Niger Delta Area, Nigeria

Loss of soil fertility through loss of soil organic matter, leaching of nutrients, loss of the nutrient-laden topsoil, changes in soil-pH, reduction in cation exchange capacity, salinization, water logging and other forms of soil degradation are major problems associated with agricultural productivity in the oil producing areas of Nigeria. This analysis investigated some selected physico-chemical properties of wetland soils affected by crude oil spillage in Bodo city in the Niger Delta region of Nigeria. Field reconnaissance survey using a handheld Geographic Positioning system (GPS) and survey technique involving random sampling, was used in siting soil profile pits. The unpolluted samples were collected 50 meters away from the polluted site but in the same geographic region and was used as control site. Soil samples were collected based on degree of horizon differentiation and analyzed using routine and special analytical techniques. Soil data were subjected to analysis of variance using Genstat program. Result shows that soil physical properties of the polluted site: moisture content, soil bulk density, and soil texture were highly significant (p=0.01 and 0.05) when compared to the unpolluted site while some chemical soil properties analysed especially soil pH, organic matter, carbon-nitrogen ratio, available phosphorus were affected by crude oil spillage. Results from this study affirm that crude oil can have detrimental effect on soil physico-chemical properties, which implies low soil fertility and thereby affect crop production and increase food insecurity within the study site. Further studies involving more edaphic properties, biotoxic metals and their bioaccessibility in crops growing on waterside affected by crude oil spill will surely enhance knowledge and management of the these highly industrially influenced soils. Also, international and national oil and gas companies should carry out their activities with international best practice.

Nutrient-doped synthetic silicates for enhanced weathering, remineralization and fertilization on agricultural lands of global cold regions- A perspective on the research ahead.

There is now a dire demand for negative emissions technologies (which sequester CO2 from the atmosphere) that can be rapidly deployed, are scalable, and are demonstrably safe and effective. Enhanced weathering of silicate minerals has demonstrated a significant potential for CO2 capture and sequestration by the formation of pedogenic carbonates in soils, subsoils, and sediments. This technique has also been shown to deliver fruitful results in terms of improving soil health, and in turn plant health, through remineralization. The silicate minerals that possess the highest weathering rates (e.g., wollastonite), are relatively rare in nature, whereas the abundant ones (e.g., anorthite and forsterite) have a slower pace of weathering, especially in colder and drier climates such as found in the extensive agricultural lands of Western Canada and the Western United States. Herein, we offer a perspective on the opportunities for computational studies targeting atomic-scale interaction of CO2 with silicates and synthesis of fast-weathering silicates (such as larnite and bredigite), whose composition can be tuned to also support soil fertilization and remineralization, and whose production must be integrated with green and carbon-neutral technologies to ensure net-negative life cycle emissions.

Soil organic matter formation and loss are mediated by root exudates in a temperate forest

Soil organic matter formation and loss are mediated by root exudates in a temperate forest

Soil organic matter gain by reduced tillage intensity: Storage, pools, and chemical composition

Soil organic matter (SOM) loss due to intensive cultivation is the focus of studies on climate change and food security. Dropping tillage intensity has been widely reported as a potential tool for SOM increase; however, the chemical composition, storage mechanisms, and vertical distribution of SOM gain are not fully understood, especially in calcareous soils. This study aimed to analyze the increased SOM conditions among pools and depths in an eighteen-year-long field experiment comparing SOM under conventional moldboard plowing (PT), deep cultivation (DC), and no tillage (NT) systems on a base-saturated Endocalcic Chernozem (Loamic). Soil samples were collected from the 0–10 cm and 30–40 cm soil layers and divided into mineral phase-associated organic matter (<63 µm, stable pool; MPAOM) and aggregate related organic matter (>63 µm, labile pool). The aggregate related organic matter was further divided into particulate organic matter (POM, <1.0 g cm-3) and aggregates-associated organic matter (AAOM, >1.0 g cm-3). Results indicated an overall increase in soil organic carbon (SOC) concentration in the topsoil in the order of PT<DC<NT. The surplus did not manifest as POM but as either MPAOM or AAOM fractions. This increase likely resulted from the surplus above-ground plant residue input, as the SOC content in the 30–40 cm layer did not change. The additional SOM, stabilized in the soil, did not affect SOM composition between depths and fractions, suggesting preferential SOM binding by the fine fraction and aggregates. This suggests preferential binding of the more aromatic and less complex SOM to the fine fraction, even for the surplus SOM in recent years. This fractionation maintains or even increases the difference between organic carbon pools (soil fractions) in terms of SOM composition. In addition, vertical differentiation as a result of tillage intensity mitigation was established by an increase in the stratification of aromaticity. These results suggest the key role of dissolved SOM movement in the profile as a potential driving force for the differentiation of aromaticity with depth. The results also emphasize the role of local conditions on OM composition changes, establishing the complexity of the process and difficulties of holistic model construction.

Soil nutrient release and microbial changes after burning of masticated fuels

AbstractSoil temperature extremes are not uncommon when woody fuels are ignited in prescribed burns or wildfires. Whether this leads to substantial loss of soil organic matter or microbial life is unclear. We created a soil heat gradient by burning four levels of masticated woody fuels (0, 34, 101, and 169 Mg ha−1) to determine if heat thresholds produce abrupt changes in soil C, N, microbial biomass, or fungal hyphae. Twenty‐four burns were conducted with masticated fuels overlaying a clay loam soil equilibrated at either 4 or 25% volumetric soil water content. Maximum temperatures ranged from 40 to 450 °C depending on fuel load and soil moisture content, with heat duration (&gt;60 °C) as great as 22 h. Moist soil quenched temperatures two‐ to threefold compared with dry soil at comparable fuel loads. A slight, gradual decline in total C and N was found with increasing temperature and heat duration, reaching a maximum loss of 14–18% of the total at the highest heat load. Available NH4 increased linearly starting at 150–175 °C and reached a maximum 15‐fold increase relative to unburned soil by 450 °C. Nitrification (30 d post‐fire) was low regardless of treatment and was essentially eliminated at the highest temperatures. Microbial biomass declined curvilinearly with increased heating, approaching 65% loss compared with unburned soil, and was most rapid in moist soil once temperatures exceeded 60–70 °C. Ultimately, we found no evidence of abrupt heat thresholds for these common soil properties. Instead, property changes followed a slightly declining trajectory (soil C, N, NO3, fungal hyphae) or a steady incremental increase (NH4) or decrease (microbial biomass).

Long-term experimental data and crop modelling to inform the ecological intensification of irrigated wheat production in South Africa

Wheat (Triticum aestivum L.) production is threatened by climate change and the decline in agricultural land available due to urbanisation, farmers switching to other crops, and environmental degradation. The aim of this study was to investigate the ecological intensification (EI) of irrigated wheat production in South Africa. Data from the long-term wheat trial at the University of Pretoria and an intensive growth analysis conducted in 2019 were used to calibrate and evaluate the APSIM model. Following adequate model performance, improved management scenarios including crop rotation, manure application, optimised inorganic nitrogen (N) fertiliser application rate, objectively scheduled irrigation, and a combination of all these improved management practices together, were tested. The adoption of all management practices simultaneously was shown to be the best practice, achieving an increase of 18% in yield and reducing deep drainage and N leaching by 31%. Whereas measured data indicated a decrease in soil organic matter (SOM) from 1.20% in 1950 to 0.58% in 2019, adopting EI measures could reduce the loss of SOM to only 0.68%. Farmers are encouraged to adopt one or more of these EI management practices as their site-specific situations allow.

Response of soil phosphorus fractions to land use change in the subalpine ecosystems of Southeast margin of Qinghai-Tibet Plateau, Southwest China

Land use change has a significant effect on soil nutrient cycling. However, data on soil phosphorus (P) fractions following land use change are scarce, especially in the subalpine ecosystem of China. Here, we investigated the influence of land use change on soil P fractions in the subalpine ecosystem of the Southeast margin of Qinghai-Tibet Plateau, Southwest China. In total, we took 168 soil samples from four land use types, including natural forest (NF), artificial forest (AF), farmland (FL), and shrubland (SL), at a depth of 0–20 and 20–40 cm. Phosphorus fractions were determined using Hedley fractionation procedures. The results showed that land use change and soil depths had a significant impact on the status of P fractions (p≤0.05). Organic P (Po) fraction significantly decreased following land use change but varied among land use types. Farmland soils showed the highest losses of Po fractions ranging from 23 to 54%, due to organic material reduction. Total P also decreased by 9.63% after the conversion of NF to AF (p≤0.05). Conversely, total P and inorganic P (Pi) fractions were significantly higher in FL soil than in other land uses (p≤0.05), likely due to the application of chemical fertilizers. Organic P extracted by NaOH was the dominant total Po fraction in all land uses, accounting for 63.3 to 73.14% of total Po, while Pi extracted by HCl was the dominant Pi fraction in FL soil, accounting for 42.74% of total P. Soil moisture content, pH, soil organic carbon (SOC), total nitrogen (total N), and calcium were key soil properties governing soil P fractions. Organic P fractions were strongly positively correlated with SOC and total N, implying that soil organic matter (SOM) plays a vital role in maintaining the soil P reserves. Generally, our findings shed light on how land use changes significantly affected P fractions. This result may have substantial implications for soil P management to maintain soil P reserves by reducing SOM losses.

Contrasting effects of maize litter and litter-derived biochar on the temperature sensitivity of paddy soil organic matter decomposition.

Organic matter input regulates the rate and temperature sensitivity (expressed as Q10) of soil organic matter (SOM) decomposition by changing microbial composition and activities. It remains unclear how the incorporation of litter-made biochar instead of litter affects the Q10 of SOM decomposition. Using a unique combination of two-and three-source partitioning methods (isotopic discrimination between C3/C4 pathways and 14C labeling), we investigated: (1) how maize litter versus litter-made biochar (of C4 origin) addition influenced the Q10 of SOM (C3 origin) under 10°C warming, and (2) how the litter or biochar amendments affected the Q10 of 14C-labeled fresh organic matter (FOM) after long-term incubation. Compared with biochar addition, litter increased the rates and Q10 of mass-specific respiration, SOM and FOM decomposition, as well as the contents of SOM-derived dissolved organic C (DOC) and total phospholipid fatty acids (PLFA). Litter-amended soils have much higher activities (Vmax) of β-glucosidase, N-acetyl-β-glucosaminidase, and leucine aminopeptidase, suggesting larger enzyme pools than in soils with biochar. The Q10 of enzyme Vmax (1.6–2.0) and Km (1.2–1.4) were similar between litter-and biochar-amended soils, and remained stable with warming. However, warming reduced microbial biomass (PLFA) and enzyme activity (Vmax), suggesting decreased enzyme production associated with smaller microbial biomass or faster enzyme turnover at higher temperatures. Reductions in PLFA content and enzyme Vmax due to warming were larger in litter-amended soils (by 31%) than in the control and biochar-amended soils (by 4–11%), implying the active litter-feeding microorganisms have a smaller degree of heat tolerance than the inactive microorganisms under biochar amendments. The reduction in enzyme activity (Vmax) by warming was lower in soils with biochar than in the control soil. Our modeling suggested that the higher Q10 in litter-amended soils was mainly caused by faster C loss under warming, linked to reductions in microbial biomass and growth efficiency, rather than the slightly increased SOM-originated substrate availability (DOC). Overall, using straw-made biochar instead of straw per se as a soil amendment lowers the Q10 of SOM and FOM by making microbial communities and enzyme pools more temperature-tolerant, and consequently reduces SOM losses under warming.

Pyrolyzed or Composted Sewage Sludge Application Induces Short-Term Changes in the Terra Rossa Soil Bacterial and Fungal Communities

The addition of compost or biochar to soils is a viable strategy to increase soil organic matter (SOM), especially if the amendments are produced from biomass wastes. The need for sustainable land management without sacrificing agricultural production is critical to alleviate negative impacts on soil quality, including loss of SOM and nutrients. Turning sewage sludge (SS) into compost or biochar can help in lowering its potential negative effects on soil and providing a viable strategy for SS management through its recycling in agriculture. The aim of this study was to evaluate the short-term impact of SS in its composted or biochar form on the fungal and bacterial communities of the Terra Rossa soil by high-throughput sequencing. A greenhouse pot trial was conducted using a 2-factor experiment consisting of amendment type (compost, biochar) and sampling time (Day 0, 30, and 60) as the main factors. The results showed no effect of SS addition on fungal and bacterial species richness, as well as a shift in relative abundance of the fungal phylum Zygomycota and bacterial phylum Firmicutes and Thermomicrobia. Both bacterial and fungal community analyses showed changes when composted sewage sludge was applied. However, only the fungal community differed from the control soil by the end of the 60-day vegetation period of Chinese cabbage.

The effect of shrublands degradation intensity on soil organic matter-associated properties in a semi-arid ecosystem

Vegetation degradation can have significant effects on organic matter fractions as well as various soil characteristics. All these can lead to the changes in soil microbial communities, which are main drivers of nutrient cycles. This is especially important for mountainous ecosystems that are very sensitive and fragile habitats due to their climatic conditions, but less attention has been paid to them. Thus, Mirkola mountainous region (northern Iran) with semi-arid climate and vegetation being dominated by Crataegus and Berberis shrubs were investigated in this study. Sites with different intensities of vegetation degradation [light (60–70 % coverage), moderate (30–40 % coverage) and heavy (0–10 % coverage)] and also non-degraded control sites (90–100 % coverage) were selected. In order to avoid pseudoreplication, three plots, each with an area of 1 ha (100 m × 100 m), were used for each of the four studied habitats. Soil (in three soil depths at 0–10 cm, 10–20 cm and 20–30 cm) samples were collected from the corners and also the center (n = 5) of the plots using iron frames (30 × 30 cm). A total of 180 soil samples (4 habitats × 15 sample × 3 depths) were transferred to the laboratory. Labile and non-labile contents of soil organic matter (SOM) (C and N in soil particles and aggregates, C and N stocks, particulate and dissolved organic matter, hot-water extractable carbohydrate, C and N mineralization) were measured in each of these sites. Results showed that vegetation degradation might result in both labile and non-labile SOM losses. SOM and its associated properties were highest in the non-degraded sites, whereas, lower values were common under degraded areas. Based on the obtained data, vegetation cover can enhance the amount of organic matter entering the soil (especially in the surface layers) and formation of fertile islands in ecosystems. Accordingly, vegetation protection is emphasized to maintain stability and provide ecosystem services in mountainous semi-arid regions.

Fertilizer quality and labile soil organic matter fractions are vital for organic carbon sequestration in temperate arable soils within a long-term trial in Switzerland

Agricultural management of soils has led to severe losses of soil organic matter (SOM), accompanied by an increased release of CO2 into the atmosphere and a reduction of soil fertility. Especially under the aspect of global warming and the increasing demand for food, there is a need for sustainable management options increasing soil organic carbon (SOC) storage in agricultural soils, but knowledge gaps exist regarding C persistence in, and its transfer between functional SOC pools, within different farming systems. Here we report on impacts of different farming systems on the temporal dynamics of SOM fractions within the DOK long-term trial (Switzerland), from 1982 to 2017. A purely minerally (CONMIN), a minerally and organically (CONFYM), and a purely organically fertilized farming system (BIODYN) were compared with an unfertilized control (NOFERT). We separated archived soils from the Haplic Luvisol (0–20 cm depth) into particulate (POM) and mineral-associated OM (MAOM) fractions, via physical fractionation, and analyzed the chemical composition of selected fractions via solid-state 13C CPMAS-NMR spectroscopy. We demonstrate that under none of the analyzed farming systems, additional SOC was sequestered in the clay-sized MAOM fraction (<6.3 µm) over a period of 36 years. In all fertilized systems, the amount of SOC in this pool did not change, but strongly decreased in NOFERT (-27%). Bulk SOC increased in BIODYN (+13%) and CONFYM (+5%), but decreased in CONMIN (-8%) and NOFERT (-20%). As no additional SOC accumulated in the clay-sized MAOM fraction, this implies that bulk SOC increases were solely stored within labile POM fractions. NMR spectra showed comparable POM chemical compositions between different systems. Differences in fertilizer quality (BIODYN = composted farmyard manure vs CONFYM = stacked farmyard manure + mineral fertilizer) and the omission of pesticides resulted in better conditions for POM stabilization and consequently significantly higher C contents of occluded POM (oPOM) within aggregates, in BIODYN. However, this labile fraction is at high risk of being lost within a few days, as illustrated by the strong annual oPOM-C content fluctuations depending on the timing of soil sampling after harvest. The highest post-harvest oPOM-C losses in BIODYN indicate the higher dynamics compared to CONFYM. It is anticipated that only sustainable fertilization methods with continuous application of solely organic fertilizers in the long-run can maintain SOC in the labile POM fractions at elevated levels, thereby ensuring soil fertility. It also illustrates the need for prevention of major losses by careful management of the labile POM fractions, as this OM could associate with fine mineral particles at a later stage and thus contribute to OC sequestration in the stable SOC pool. Overall, the potential of arable soils to accumulate stable OC for long-term sequestration is questioned.

Effects of composite materials and revegetation on soil nutrients, chemical and microbial properties in rare earth tailings

The mining of ionic rare earth elements in Ganzhou left large area of barren tailings with severe vegetation destruction in pressing needs of remediation. However, the remediating effects of soil additives combined with revegetation on the preservation of nutrients in the tailings and microbial communities were rarely studied. For this purpose, pilot experiments were implemented in a field, with the control group (CK) only cultivating plants without adding materials, and three treatments including peanut straw biochar composite (T1), phosphorus‑magnesium composite (T2) and modified zeolite composite (T3) along with the cultivation of Medicago sativa L., Paspalum vaginatum Sw. and Lolium perenne L. Soil pH and organic matter in CK significantly decreased from 4.90 to 4.17 and from 6.62 g/kg to 3.87 g/kg after six months, respectively (p ≤ 0.05), while all the treatments could effectively buffer soil acidification (over 5.74) and delay the loss of soil organic matter. Soil cation exchange capacity was still below the detection limit in all the groups except T2. The results of rainfall runoff monitoring indicated that compared with CK, only T2 could significantly reduce the runoff loss of soil NO3− and SO42− by 45.61 %–75.78 % and 64.03 %–76.12 %, respectively (p ≤ 0.05). Compared with CK, the bacterial diversity in T2 and T3 significantly increased 21.18 % and 28.15 %, respectively (p ≤ 0.05), while T1 didn't change the bacterial or fungal diversity (p > 0.05). Co-occurrence network analysis showed that compared with CK, the whole microbial communities interacted more closely in the three treatments. Functional prediction of the microbial communities revealed all the treatments were dominated by carbon transforming bacteria and saprotrophic fungi except T2. This study demonstrated that the composite materials combined with revegetation couldn't retain soil nitrogen compounds and sulfate in rare earth tailings in the long term.

Residential and agricultural soils dominate soil organic matter loss in a typical agricultural watershed of subtropical China

Soil organic matter (SOM) loss in agricultural watersheds driven by hydrology threatens the aquatic environment, and increases the risk of greenhouse gas emissions from aquatic systems, and will be detrimental to both the green development of agriculture and the achievement of the national “carbon peaking and carbon neutrality” goal of China. Consequently, we explored the use of δ13C, δ15N, and the carbon to nitrogen ratio (C/N) as end-members and combined this with a Bayesian stable-isotope mixed model to quantitatively estimate the contribution of typical land-use types (i.e., forest, rice, vegetable, tea, and residential soils) to sedimentary organic matter in a typical agricultural watershed in subtropical China. The results indicated that there was significant spatial variation of δ13C, δ15N, and the C/N in the target sediment mixture and its sources. The range of sediment δ13C (−26.2‰ to −23.8‰) and δ15N (3.9–7.9‰) were within the ranges of the sources, with δ13C and δ15N ranges of − 29.3‰ to − 20‰ and − 1.2‰ to 9‰, respectively. The average C/N of sediment was 11.1 ± 0.52, which was significantly higher than all source samples. The spatial distribution of δ13C and δ15N indicated that SOM loss in this catchment may primarily be attributed to vegetable and residential soils. According to the qualitative identification from dual fingerprint mark composite graphs of the C/N and δ15N, as well as δ13C and δ15N, the sedimentary SOM in the Tuojia watershed was mainly derived from sewage. Furthermore, Bayesian stable-isotope mixed model analysis indicated that residential soil was the main contributor to the SOM loss in the watershed, with a contribution rate of 75.8 %, followed by agricultural land (rice and vegetable soils) with a combined input of 12 %. The findings highlight that anthropogenic life and agricultural production have a vital impact on the carbon and nitrogen cycle in this agricultural catchment, and improving the rural habitation environment may play a key role in the control of SOM loss in subtropical agricultural watersheds.

New technologies in pasture and grazing management in the face of climate change perspectives

The search for sustainable livestock farming has been the focus of several researches in Brazil and worldwide, in face of climate change. Livestock production is mostly explored in pastures in Brazil. It is estimated that a large part of these pastures presents some kind of degradation, as a result of its incorrect management. With this degradation, besides reducing productivity, there is loss of soil organic matter and CO2 emission to the atmosphere, with a reduction in carbon sequestration by the pasture. Consequently, there is the release of excess enteric methane, which occurs in the digestive process of ruminants, by fermentation of fibrous and poor quality food ingested by these animals from this pasture. Several studies propose new technologies to mitigate greenhouse gases, with intensive pasture management, processing and conservation of forage to reduce particle size and increase digestibility. Recovery and renovation of pastures, using integrated production systems with grain, forest, and forage production. Implementation of pasture with forage in suitable environments and use of grasses with better leaf/stem ratio. Use of rotational grazing with height control of animals entering and leaving each forage species in order to produce a better and more digestible forage. With this, reduce the precursors of greenhouse gases to mitigate the possible effects on climate change.

The viability test of phosphate solubilizing microbes on carriers during storage

Excessive use of inorganic fertilizers, especially during the green revolution, has caused pollution and contamination of the soil due to accumulated residues. The inorganic fertilizer residues then cause soil compaction, loss of available nutrients and soil organic matter, loss of soil biodiversity which indirectly reduces soil fertility and makes plants more susceptible to disease. Biofertilizers have the potential to optimize soil response to fertilization, improve soil health, and even reduce the need for inorganic fertilizers to achieve sustainable agriculture. One of the types of microbes contained in biological fertilizers that have been proven to be able to replace the need for inorganic P fertilizers and improve soil health and productivity is a group of phosphate solubilizing microbes. The quality of biofertilizers is also determined by the carrier material capable of supporting the growth of inoculants. The purpose of this study was to test the viability of phosphate solubilizing microbes on carriers during storage The microbes used were Bacillus subtilis, Pseudomonas mallei, Burkholderia sp, and Trichoderma harzianum, while the tested carrier material were hydrogel and kaolin. The results showed that hydrogel and kaolin as carriers were able to support the growth of P-solubilizing microbes inoculants during storage (until 126 day). The number of viable populations of each isolate that makes up the biofertilizer consortium was in the high population range up to 1012 cfu. g-1.

Effects of forest management on soil acidification in cedar plantation

Forest management practices such as clearcutting risk increasing the leaching loss of cations and soil acidification by increasing nitrification and reducing plant uptake. To evaluate the effect of two forest management practices, clearcutting and stem girdling, on soil acidification, we quantified proton budgets by measuring ion fluxes associated with solute leaching and plant uptake in a Japanese cedar plantation in Wakayama, Japan. In the control and girdling plots, the dissociation of organic acids was a major proton-generating process that promoted cation leaching from the organic horizon. Plant uptake of mobilized cations was a dominant soil-acidifying process in the control plot, whereas litterfall from tree dieback and loss of plant uptake led to soil alkalization via cation inputs to the mineral soil in the girdling plot. In the clearcut plot, in addition to cation removal due to harvesting, nitrification was a major proton-generating process that increased aluminum (Al) leaching in the first year following clearcutting. However, proton consumption via net mineralization (loss) of soil organic matter (SOM) could neutralize the acidity generated by nitrification. Forest management practices stimulate both proton-generating and -consuming processes. Soils under cedar plantation are affected by biological acidification of surface soil by plant uptake in the rooting zone and net cation leaching by carbonic acid below the rooting zone (subsoil and bedrock), but organic matter and Al and Fe oxides accumulated in plantation could mitigate acidification induced by disturbances.

Fallow replacement cover crops impact soil water and nitrogen dynamics in a semi-arid sub-tropical environment

Conventional dryland cropping systems rely upon frequent and lengthy fallow periods to conserve soil water and mineral nitrogen to stabilize crop production. However, this is associated with depletion of soil organic matter and decreased fallow efficiency. Intensifying cropping systems by planting cover crops has been touted as a means to stem soil organic matter loss and improve fallow efficiency. We investigated whether the manipulation of cover crop functional trait diversity and sowing proportions (utilizing Poaceae, Fabaceae, and Brassicaceae) could provide complementary functions that improve soil water and mineral N management during fallow. Grass-legume mixtures represented the best compromise between biomass production (> 4000 kg DM ha˗1), N retention (142 kg N ha˗1), N supply via biological N fixation (35 kg N ha˗1) and maintained an additional 70 mm of water at the end of fallow period. Regardless of functional trait type, cover crops increased N retention but maintained similar soil mineral N content at the end of fallow period. However, soil water effects were functional trait-specific, and there were significant soil water deficits with brassica-dominated cover crops. Soil water accumulation post cover crop termination was significantly higher in cover crops compared with conventional fallows, but the overall fallow efficiency was higher in the conventional fallow. This study demonstrates that cover crops are not universally beneficial, and careful selection of cover crop functional traits in mixtures could enhance fallow soil water and N management in semi-arid sub-tropical drylands.

Persistence of arable Chernozems and Chernic Rendzic Phaeozems in the eroded undulating loess plateau in Central Europe

Chernozems are considered to degrade under the temperate humid climate of Central Europe, particularly in the arable and undulating areas and, thus, exposed to erosion. The present study was carried out in the loess-covered Proszowice Plateau (southern Poland), which was found to have a continuous cover of chernozemic soils in the past. Ten soil profiles located in two neighbouring slope catenas have documented the sequence of chernozemic and non-chernozemic soils (Chernozems, Phaeozems, and Calcisols), impacted by water erosion under intense arable land use and spatially dependent on the relief intensity. Soils in elevated, strongly inclined (and, thus, intensely eroded) slope positions lost their mollic horizons and gained the features of Calcisols. However, soils in elevated, slightly inclined positions preserved the morphological and physicochemical features of Chernozems, even if their chernic horizons were thinned to a ploughing depth. Also the colluvial soils located on the short slopes, in close proximity to eroded hilltops, are saturated with secondary carbonates throughout the profile and retain their chernozemic features (Calcic Chernozems). Whereas, the colluvial soils located on the long, slightly inclined slopes, at a large distance to eroded hilltops, are deeply leached from carbonates and meet the criteria of Haplic Phaeozems (in well drained sites) or Gleyic Phaeozems (in poorly drained foothills and depressions). Moreover, the Chernic Rendzic Phaeozems with thick mollic/chernic horizons are present in elevated (thus expectedly eroded) parts of hills with thin loess overlying the limestone bedrock. The presence of chernic horizons in soils threatened by erosion indicates that the persistence of Chernozems and Chernic Rendzic Phaeozems is possible in undulating arable lands threatened by erosion in temperate humid climate of Central Europe if supported by sustainable agriculture, preventing soil erosion and organic matter loss from humus horizons.

Cropping leads to loss of soil organic matter: How can we prevent it?

Soil organic matter (SOM), which associates carbon (C) to key plant nutrients, has been stored in soil for thousands of years. Scientists have long recognised its positive impact on key environmental functions such as food production and climate regulation. As soon as a virgin land (forest or grassland) is cultivated, there is a tendency for the soil to lose its SOM, and we still largely misunderstand the underlying mechanisms, leading to inappropriate decisions being taken to fight soil, climate, and overall ecosystem degradation.

ASSESSMENT OF SOIL ORGANIC MATTER MANAGEMENT IN POLISH AGRICULTURE

The subject of this study was the analysis of the soil organic matter (SOM) management in Polish agriculture in 2017-2019. The comparative analysis in spatial arrangement was carried out at the level of polish voivodeships. SOM balance was prepared in a simplified way, using it is degradation and reproduction coefficients proposed by Eich and Kundler. During 2017-2019, the balance of SOM was at level of 0.07 t DM/ha arable land (ArL). Positive balance of SOM was found in most voivodeships of Poland, and by far the highest in two voivodeships: Podlaskie and Warmińsko-Mazurskie, where manure and slurry resources were the largest. The negative SOM balance ranged from -0.02 t DM/ha ArL in Lubuskie to -0.14 t DM/ha ArL in Dolnośląskie, and the main reason for this was low natural fertilizer supply. In those voivodships the amount of ploughed-in plant material was insufficient to cover the losses of SOM caused by plant cultivation. The analysis of SOM management confirmed high polarisation between individual voivodships, together with the processes of extensification of production organisation (specialisation), with a simultaneous increase in it is intensity and scale of concentration.