Soil & Tillage Research最新文献

As a dynamic process in the soil, soil aggregation has a direct impact on several vital functions, including microbial activity, greenhouse gas emissions, water storage, and nutrient availability. Biochar as a recalcitrant soil amendment could potentially regulate soil functions, especially aggregation. However, there have been conflicting studies regarding the effectiveness of biochar, its variations, and how it interacts with various soil conditions to affect aggregate status. In this regard a thorough meta-analysis was conducted, considering six categories of significant variables: soil texture, soil organic carbon (SOC), application rate, pyrolysis temperature, feedstock type, and various biochar use methodologies as well as various soil aggregation indices as impacted factors. Based on the results, wood-based biochar showed the highest efficiency above straw and manure-based biochar with a positive effect size of 15.4 % and 17.7 % for mean weight diameter (MWD) and macro-aggregate. The highest geometric mean diameter (GMD) was obtained from biochars pyrolyzed at 550< °C with 19.9 % effect size. Also, low pyrolysis temperature (<450 °C) resulted in the maximum formation of micro-aggregates with a positive effect size of 14.9 %. The moderate application of biochar (10–20 t ha⁻¹) resulted in the lowest micro-aggregates (−8.9 %) and the highest macro-aggregates (24.2 %). The single application of biochar resulted in a positive effect size in the case of macro-aggregate (17.2 %) significantly higher than the combined application of biochar with fertilizer (8.1 %). The highest MWD (12.8 %) and GMD (7.1 %) were obtained from biochar-treated soils with loamy texture. Also, the high availability of SOC (2<%) caused the highest macro-aggregate formation with a positive effect size of 28.2 %. Expanding our knowledge of biochar capability and soil functions could change soil aggregation scenarios, as the variety of biochar pyrolysis processes and its application strategies could directly modify soil's dynamic structure, through inducing functional groups, carbon linkage, and soil particle rearrangement.

Many farmers have adopted reduced tillage management practices. While the effectiveness of these practices at reducing soil erosion and enhancing soil health are well documented, the impact of reduced tillage on plant nutritional quality is not well understood. Current interest in the role of the fungal derived antioxidant ergothioneine (ERGO) in human health has driven efforts to understand the influence of different crop management practices on the transfer of ERGO from soil to plants and ultimately to human consumption. We sampled roots and plant tissue from soybeans (Glycine max) and wheat (Triticum aestivum) in a long-term (40+ year) side-by-side tillage trial and examined the extent to which moldboard plow (high intensity tillage), chisel/disk (intermediate tillage), and no-till (minimal disturbance) practices affected mycorrhizal colonization, ERGO concentration, mineral nutrient concentration, and yield. We found that high tillage intensity reduced the ERGO concentration of wheat grain by about half. The ERGO concentration of wheat was positively correlated with percent mycorrhizal colonization. Additional benefits of reduced tillage were increased concentration of soybean P, Mg, Cu, Zn, and increased soybean yield. These results demonstrate a possible link between soil health and human health through positive mycorrhizal influence on plant ERGO uptake.

Management of perennial weeds has become increasingly difficult with the reduction of herbicide use. Creeping perennials accumulate reserves in specialized belowground organs from which they regenerate new plants after a disturbance. Through tool selection, tillage operations could be optimized to reduce perennial-weed reserves and limit regeneration. In the present study, the effect of five tools on the fragmentation of the creeping roots of Cirsium arvense (L.) Scop. (Canada thistle), a major perennial weed in arable crops, were analysed. A field trial was set up to measure the lengths of the root fragments left after tillage. Five tools were tested: mouldboard ploughing, rotary harrow, disc harrow, rigid-tine cultivator and goose-foot cultivator. Fragment-length distribution varied according to the tool: rotary harrow left the smallest (3.7 cm on average) and least variable fragment lengths, mouldboard ploughing the longest (12.7 cm) and most variable ones. The other tools produced intermediate-sized fragments (8–10 cm). Based on these results and literature, a model was proposed to predict perennial-weed regeneration probability from storage-organ fragments after one tillage run. The effects of six factors, which were agronomic (tillage tool), environmental (soil conditions and temperature) and biological (storage-organ fragment diameter, maximal belowground-shoot length and pre-tillage storage-organ distribution), were tested through a sensitivity analysis. According to the model, the probability of fragment regeneration success is lower for the rotary harrow than for the mouldboard plough. The most important drivers of fragment regeneration success were the biological traits: fragment diameter and maximal belowground-shoot length per unit fragment biomass. The present model should be complemented to predict the effect of tillage on perennial-weed regrowth and help improving non-chemical weed-management strategies. To achieve this, further research is needed on plant regrowth potential from storage organs and their architecture in the soil.

Understanding land use effects on carbon sequestration in various soil fractions is vital to mitigating climate change and restoring soil functions. The objective of this study was to explore the effects of land use on soil organic carbon (SOC) fractions in different soil types. For this purpose, we studied the effects of long-term (>20 years) land use including dryland pasture (DP), irrigated pasture (IP) and irrigated cropland (IC) on SOC in water-stable aggregates, particle-size fractions, and their coupling relations at the surface soils (0–7.5 cm) in the Canterbury Plains, New Zealand. For each land use, three typical soil types with contrasting drainage levels (i.e. well drained Lismore soil, LIS; imperfectly drained Templeton soil, TEM; and poorly drained Waterton/Temuka soil, WAT) were selected. Macroaggregate-occluded mineral-associated organic carbon (M-MAOC) contributed to the majority of the total SOC difference and drove the response of SOC to land use change. On average, M-MAOC followed an order of IP > DP > IC. The effects of land use change from DP to IP and IC on M-MAOC varied, and these variations were dependent on soil type. The relative gain in M-MAOC with change in land use from DP to IP was the greatest in the well drained LIS soil, while both the relative and absolute loss in M-MAOC following the land use change to IC was the greatest in the poorly drained WAT soil. The interactive effects of managements (e.g. irrigation and cultivation) and soil type (e.g. soil water condition) on aggregate size distribution and macroaggregate-associated C concentration were important in explaining the responses of M-MAOC to land use change. This study advances the mechanistic understanding of total SOC dynamics in response to land use (changes) in different soil types. It also highlights the potential of M-MAOC to serve as a diagnostic fraction to reflect changes in total SOC, which may have application to global warming mitigation.

Straw return is a widespread agricultural practice for improving cropland nitrogen (N) stocks. However, the contribution of microbial N to the soil aggregate N pool and the underlying microbial metabolic regulation mechanisms remain uncertain. This study was based on a 13-year field experiment with rice (Oryza sativa L.) and wheat (Triticum aestivum L.) rotation, using only a chemical fertilizer alone (CF) as the control. We analyzed the effects of the chemical fertilizer combined with (CS, 9500 kg ha⁻¹ y⁻¹) and wheat (4000 kg ha⁻¹ y⁻¹) straw on microbial derived-N, microbial carbon (C) and N limitations. We also assessed microbial N use efficiency (NUE) in various aggregates of ferric lixisols (0–20 cm). Rotary tillage reached a depth of 20 cm. The CS significantly increased microbial-derived N concentrations in soil aggregates and enhanced the contribution of fungal residual N to the N pool in aggregates < 0.25 mm, but did not affect those > 0.25 mm. Conversely, the bacterial contribution to the N pool was not affected by CS. Meanwhile, CS significantly increased the soil organic C and microbial biomass in the aggregates. The results of our eco-enzymatic stoichiometric model revealed that the CS significantly alleviated microbial C limitations and increased microbial NUE in soil aggregates. Structural equation modeling further revealed that the microbial biomass and soil organic C contents are key drivers of the microbial C limitation. The increased contribution of fungal residual N to the N pools in < aggregates 0.25 mm was attributed to improved microbial NUE resulting from the straw, without altering net N mineralization rates or β-1,4-N-acetylglucosidase activity. Our findings suggest that straw return promotes microbial-derived N production and sequestration by alleviating microbial C limitation. The strategies governing these microbial-derived N responses in aggregates to straw return might vary. This might be valuable for designing cropland management practices to improve N storage.

Fertilizer application can affect the physicochemical properties of soil, such as the contents of large aggregates, humus, and exchangeable cations, thereby influencing soil erosion resistance. However, the rill erosion resistance and its key influencing factors of soil following long-term balanced fertilizer application remains unclear. This study aimed to analyze the change in rill erosion resistance following 44 years of balanced fertilizer application (No changes in the type of fertilizer) to non-calcareous soils and establish a Partial Least Squares Regression (PLSR) model of rill erodibility (k_d) and soil critical shear stress (τ_c) to changes in the physical and chemical properties of the soil. Five treatments were designed: (1) CK (no fertilizer applied), (2) N (nitrogen), (3) NP (nitrogen plus phosphorus), (4) NK (nitrogen plus potassium), and (5) NPK (nitrogen, phosphorus, and potassium). Compared to CK, the N, NP, NK, and NPK application significantly increased τ_c by 49.6, 96.7, 73.6, and 36.2 %, respectively. Whereas, k_d increased significantly only in the NPK treatment group. The optimal partial least squares regression model showed that mean weight diameter (MWD) had the greatest positive influence on soil critical shear stress, followed by fulvic acid (FA) content, whereas water-dissolved substances had a negative influence. Long-term balanced fertilizer application can increase MWD and τ_c by combining micro-aggregates and humus into large aggregates. Ca²⁺ content had the greatest positive effect on k_d. Compared with that of CK, exchangeable Ca²⁺ content increased significantly with NP and NPK application (7.9 and 34.3 %, respectively). Ca²⁺ can increase k_d by binding to the polar functional groups in FA to promote the shedding of hydration shells in large aggregates. Among all treatments, the NP treatment showed the best performance for reducing k_d and increasing τ_c. This study could contribute to the understanding of the rill erosion process and modeling in non-calcareous soils and offer a reference for agricultural erosion control treatments.

Sustainable cropland management requires preservation of soil organic matter (SOM). In spite of in depth understanding gained from ample field and laboratory studies, we have a poor understanding of landscape scale spatial variation of fresh organic matter (OM) decomposition and its conversion into soil organic carbon (SOC). Particularly, local topographic position may be expected to co-control these processes via soil hydrology. In this study, we sought to identify if such control is significant by setting up a field experiment with two contrasting positions across 10 gently sloping cropland fields covering three different soil texture groups, i.e. loamy sand, (sandy) loam and silt loam. We wanted to link OM decomposition to within-field differences in soil moisture, whilst keeping variation in other soil and management factors minimal. Specifically, mesocosms with ¹³C enriched ryegrass (the OM source) were incorporated in the fields for ten weeks and afterwards, soil was separated into > 500 µm, 53 – 500 µm and < 53 µm sized fractions. Overall, we found that lower located positions were wetter than higher positions with average differences of 11 %, 20 % and 16 % in water-filled pore space for the loamy sand, (sandy) loam and silt loam soil, respectively. Mineralization of added OM was surprisingly independent of landscape position, even though moisture conditions appeared wetter than optimal at the low but not at the high landscape positions. Remaining ryegrass residues > 500 µm did follow local topography-driven gradients in soil moisture with higher amounts in low landscape positions. In other words, drier conditions at high landscape positions improved coarse OM decomposition, with consequently more ryegrass-carbon (C) ending up in finer soil fractions (< 500 µm). Additionally, soil texture affected decomposition of the smallest fraction (< 53 µm) with a stabilizing effect for finer-textured (silt loam) soils. We conclude that, despite significant contrasts in moisture conditions between landscape positions, within-field spatial variability of OM mineralization was overall limited during the observed wet summer period. Nevertheless, landscape position affected the quality of remnant unmineralized C, with relatively more conversion of freshly added OM into OM associated with silt and clay at the drier higher positions, potentially improving the long-term stability of SOM. Likewise observations under different weather conditions are needed to evaluate the necessity of precise modelling of local soil hydrology for predicting SOC stock evolution on the landscape scale.

Biochar is a promising carbon sequestration strategy, however, the mechanisms underlying the regulation of microbial-derived carbon (M-C) and plant-derived carbon (P-C) in soil organic carbon (SOC) formation and stabilisation remain elusive, constraining accurate predictions of the organic carbon pool. This study examined the soil biotic and abiotic factors that influence the plant and microbial biomarkers in SOC accumulation. A 5-year field experiment was conducted in a temperate wheat-maize agroecosystem in north-western China, with three treatments: (i) no straw incorporation (C), (ii) straw incorporation (S), and (iii) straw incorporation + biochar (SB). The results showed that M-C reached the microbial carrying capacity gradually, whereas P-C was selectively and continuously accumulated, displaying a complementary S-curve pattern. Straw incorporation increased SOC, microbial biomass carbon (MBC), and dissolved organic carbon (DOC) contents, which stimulated microbial richness and enzyme activities, resulting in a 29.1 % and 25.5 % increase in M-C and P-C in SOC, respectively. The stimulated SOC mineralisation (26.2 %) led to significantly lower SOC content in S compared to the SB practice. Biochar combined with straw decreased DOC content (18.5 %) in comparison with straw incorporation, which suppressed microbial and enzyme activities, particularly in Actinobacteriota (12.3 %) and β-N-acetyl-glucosaminidase (24.2 %). It resulted in a 10.9 % and 14.3 % increase in M-C and fungal-to-bacterial necromass carbon ratio (F/B), respectively, while decreasing P-C by 9.6 % over the 5 years. Overall, straw incorporation with biochar effectively enhanced M-C in SOC and reduced SOC mineralisation, suggesting its potential to augment the quantity and stability of SOC pools and mitigate global climate change.

Gully erosion, with an enormous threat to global economic development and ecological security, results from the comprehensive effect of soil inherent properties and external geo-environmental factors. Previous studies on gully causative factors were mainly conducted on a specific site, case, or region, and limited systematic investigation has been performed on their spatial variation. Based on gully inventory in the seven provinces of southern China, this study investigated the spatial variation of thresholds for fifteen potential causative factors by the frequency ratio model, and analyzed the contribution of these factors to gully erosion by the Boruta algorithm. The results showed that gully density generally increased from north to south, characterized by a clustered distribution within a specific range, but the threshold of each potential factor exhibited a slight difference. Particularly, gully formation was predominantly influenced by multi-year average rainfall erosivity, multi-year average rainfall, and population density. However, the relative importance of these factors to gully erosion showed significant spatial heterogeneity. The relative importance increased from north to south for the factors of rainfall erosivity (8.25 %-13.56 %), rainfall (8.62 %-12.01 %), and slope aspect (0.35 %-1.22 %), but decreased for the factors of slope gradient (2.93 %-6.24 %), temperature (5.23 %-8.89 %), normalized difference vegetation index (NDVI) (5.25 %-7.80 %), and fraction vegetation coverage (FVC) (4.11 %-7.23 %). Overall, climatic factors exhibited an increasing contribution to gully erosion from north to south, whereas the influence of topography and vegetation coverage decreased along the same gradient. These findings will facilitate a better gully erosion control in southern China.

Continuous rotary tillage has resulted in several issues, including a thin tillage layer with low soil organic carbon (SOC) and soil compaction, impeding crop root development and resulting in low crop yields, especially in clay soils. Although deep tillage can increase crop yields by loosening the soil structure and expanding the tillage layer it is rarely applied in soils with high clay contents (such as lime concretion black soil) because of its high energy consumption and low economic benefit. This study aimed at investigating the modified tillage practice with lower energy consumption (combining rotary and deep tillage to return crop straw into different depths among different years) in the higher crop yield on a clay soil. We conducted a 5-year (2017–2021) field experiment in a lime concretion black soil with high clay content. The experiment included four treatments: conventional tillage (CT) to return crop straw into the 15-cm layer without and with fertilizer addition, modified tillage (MT) to return crop straw into different depths (i.e., 35 cm in 2017, 20 cm in 2018, 10 cm in 2019, and 20 cm in 2020) with fertilizer addition, and MT combined with fertilizer and activator addition. We investigated the crop yields, soil physicochemical properties, and microbial communities at the topsoil (0–15 cm) and subsoil (15–30 cm) layers. Compared with CT, MT increased maize (Zea mays Linn.) and wheat (Triticum aestivum L.) yields by 9.8 % and 11.4 %, respectively, by enhancing the SOC content and improving the soil physical properties of the subsoil (i.e., aggregate stability, macroaggregate proportion, soil porosity, and the proportion of large and small pores). We suggest a scientific tillage practice for future attempts to increase SOC sequestration and promote crop productivity in agricultural soils, especially those with a high clay content.