Long-term Application Of Organic Amendments Research Articles

Size and composition of colloidal phosphorus across agricultural soils amended with biochar, manure and biogas slurry

The long-term application of organic amendments like manure, biochar and biogas slurry can increase phosphorus (P) levels in agricultural soils; however, at present, it's not clear how this affects the P association with different mobile water-dispersible colloidal particles (Pcoll). Thus, this study aimed to assess the effects of the long-term application of different organic amendments on the abundance, size and compositional characteristics of Pcoll. For this purpose, a total of 12 soils amended with the above three organic amendments were sampled from the Zhejiang Province, China, and Pcoll were fractionated into nano-sized (NC; 1–20 nm), fine-sized (FC; 20–220 nm), and medium-sized (MC; 220–450 nm) by a combination of differential centrifugation and ultrafiltration steps. These three Pcoll forms together accounted for 74 ± 14% of the total soil solution dissolved P content, indicating that Pcoll release was a key process in the overland P transport from these soils. Soils treated with biochar showed lower Pcoll contents than those treated with manure or slurry alone; this effect should be further explored in a controlled inductive research approach. Compositional analysis showed that inorganic P was the predominant Pcoll form in the NC (54 ± 20%) and FC (63 ± 28%) fractions, but not in the MC (42 ± 26%) fraction. Among the three fractions, the organic carbon (OC)–calcium (Ca) complex was the major carrier of NC-bound Pcoll, MC-bound Pcoll was better correlated with OC–manganese/iron/aluminium colloids than with OC–Ca colloids, and both of these phenomena co-occurred in the FC fraction. The current study provides novel insights into the impact of various carbon amendments on the propensity for P loss associated with different soil mobile colloidal fractions, and will therefore, inform future agronomic and environmental-related policies and studies.

Long-term application of organic amendments changes heavy metals accumulation in wheat grains by affecting soil chemical properties and wheat yields

Long-term application of organic amendments changes heavy metals accumulation in wheat grains by affecting soil chemical properties and wheat yields

Effects of Long-Term Chemical and Organic Fertilizer Application on Soil Phosphorus Fractions in Lei Bamboo Plantations

Phosphorus (P) is a key nutrient in forest ecosystems in subtropical regions. However, the effects of the long-term application of organic amendments on P availability are poorly understood. Here, we compared the soil P fractions and associated soil properties in southern Chinese Lei bamboo plantations using both an intensive management system (IMS) and a traditional management system (TMS). The results show that the IMS significantly (p < 0.05) increased the soil total organic carbon (C), soil ammonium N (NH4-N), total P, and available potassium content; microbial biomass C and P content; P activation coefficient, and soil C:P ratios, while significantly (p < 0.05) decreasing pH and microbial C:P. The labile-P-to-total-phosphorus-content ratio increased significantly in the IMS (46%) compared with that in the TMS (32%). The selected soil properties (except nitrate [NO3−N]) were significantly related to soil P fractions (except for concentrated HCl-extracted organic P). The IMS had a higher C:P ratio and labile P content than the TMS, suggesting that the IMS could promote soil P transformation and availability. Overall, the IMS increased soil P availability and supply capacity, and the changes in P forms could be a risk factor for P loss.

Repeated applications of organic amendments promote beneficial microbiota, improve soil fertility and increase crop yield

Long-term adoption of intensive agricultural system negatively affects soil fertility, soil microbiome and may compromise the quality and amount of crop production. To avoid these problems, application of organic materials has been proposed as a potential alternative strategy for soil management. Therefore, the objective of this study was to compared the effects of conventional and organic soil management on crop yield of rocket (Eruca sativa), soil fertility, and microbiome structure through a 2-year long mesocosms experiment. Eight organic treatments, different in terms of organic amendment chemistry (i.e., alfalfa hay, biochar, glucose, manure) and application frequency, were compared with conventional management practices based on mineral fertilizer and chemical fumigation. Crop quality was assessed by measuring the NO3− content in leaves, whereas soil chemical and microbiological (i.e., FDA activity and functioning by BIOLOG EcoPlates™) properties were evaluated to understand their effects on soil fertility. Changes in soil microbiota were assessed by high-throughput sequencing of bacterial and fungal rRNA gene markers. Application of organic amendments significantly improved crop yield, especially when alfalfa and glucose were applied as a single dose. NO3− concentration in leaves was decreased with biochar and manure application, and this did not depend on the application frequency. Application of synthetic fertilizer and fumigation induced soil acidification, increased soil salinity, and reduced soil microbiota diversity, activity and functionality, with negative effects on crop yield. In conclusion, this study indicates that long-term application of organic amendments effectively improved soil fertility and promoted the development of a beneficial soil microbiota capable of supporting high plant yield under intensive agricultural system.

Effects of Organic Amendments on the Transformation of Fe (Oxyhydr)Oxides and Soil Organic Carbon Storage

Organic amendments from animal production are commonly used for promoting soil fertility, and their impacts on the residual soil organic carbon (SOC) are of both agricultural and environmental interest. Iron (Fe) in the form of (oxyhydr)oxides has been proposed to play a critical role in long-term SOC preservation by forming Fe-organic associations, though currently a comprehensive understanding of how these Fe-organic associations are regulated by long-term organic amendments is limited. Here, we synthesize information to link Fe (oxyhydr)oxides, SOC sequestration, and long-term organic inputs from both field and laboratory studies. The results show that vigorous Fe mobilization can be regulated by long-term application of organic amendments, and these organically amended soils contained significantly higher concentrations of poorly crystalline Fe that was closely related to SOC storage in both upland and paddy soils. Potential mechanisms are proposed as follows: (1) DOM from the organically-amended soils is more likely to co-precipitate with poorly crystalline Fe, and DOM from the inorganically-fertilized soils is to a larger extent adsorbed on poorly crystalline Fe. The co-precipitated Fe-OM complexes are more resistant to desorption than the adsorbed OM. (2) DOM extracts from soils treated with organic amendments exhibit a stronger inhibitory effect on the crystallization of poorly crystalline Fe than DOM from inorganically fertilized soils, which may be the consequence of increased numbers of aromatic functional groups. Organic acids in root exudates increased soil mineral availability and the formation of poorly crystalline minerals. Compared to inorganic fertilizers, organic amendments significantly increase (> 20%, p < 0.05) the concentration of poorly crystalline minerals in the presence of actual roots. (3) Microbially-mediated Fe cycling is strongly linked to the Fe mineralogy in soils, and regulated by long-term organic amendments. Greater consumption of poorly crystalline Fe was observed in inorganically-fertilized soil than that in organically amended soil, due to a higher relative abundance of Fe(III) reducers. Conversely, Fe(II) oxidizers were more abundant, and produced higher levels of poorly crystalline Fe under organic amendments. In conclusion, continuous organic amendments initialize a positive feedback loop for the maintenance of poorly crystalline Fe in soils, which can contribute to enhanced SOC storage.

Effects of Soil Management on Aggregation and Organic Matter Dynamics in sub-Saharan Africa

Maintenance of soil organic matter (SOM) is important for soil quality and agricultural productivity. However, little is known about the effects of management practices of different intensities on soil aggregation and SOM dynamics in tropical arable cropping systems of sub-Saharan Africa. We investigated the influence of land use practices and management intensity on soil aggregation and SOM dynamics across 12 long-term field experiments in eastern and western Africa. Aggregate size distribution and SOM were measured in arable systems under contrasting management intensities of high carbon, low carbon and a fallow. Aggregate stability indices and SOM were generally higher in the fallow compared to the arable systems. Fallowing and high carbon inputs in arable soils, significantly improved aggregate stability and carbon (C) and nitrogen (N) stabilization in whole soil, and in aggregate fractions. In contrast, no significant improvements in soil aggregation and C and N stabilization were found when organic inputs were either applied in low quantities or not applied at all, thus resulting in low carbon in soils. Our study showed that fallowing and long-term application of organic amendments alone or in combination with mineral fertilizers were the best among the practices tested in this study, for enhanced C and N stabilization in soils with the subsequent benefits of improving soil physical and chemical properties. These results emphasize the importance of management for sustaining soil quality. It is recommended that fallowing be an integral part of sustainable soil management strategies in these regions. Keywords: Soil aggregation, soil organic matter, carbon, nitrogen, management intensity

Changes of soil properties and carbon fractions after long-term application of organic amendments in Mollisols

Land degradation threatens soil fertility as well as environmental security. To assess the extent of degradation of black Mollisols in northeast China, chemical and microbial indicators of soil quality were determined after long-term application of organic amendments combined with chemical fertilizers. The application of high amounts of organic manure plus chemical fertilizer (NPK) significantly increased soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and mineral nitrogen (Nmin), as well as microbial biomass carbon (MBC), extractable dissolved organic carbon (DOC), microbial quotient (qMIC), carbon (C) in free light fraction (fLF) and its percentage of total soil C. Soil C/N ratio and C portion in heavy fraction (HF) both decreased significantly, which might have resulted from accelerated mineralization of stable C. Application of straw at a low rate plus NPK significantly increased Nmin and MBC concentrations and qMIC. Compared with the unamended control, no negligible differences were found for most of the selected parameters under the treatments NPK alone, high-rate straw plus NPK, and low-rate manure plus NPK. These results indicated that NPK along with either a high rate of manure or a low rate of straw profoundly changed certain key soil chemical and microbial properties. Despite these apparent benefits in soil properties, however, high rates of manure application is likely contributing little to soil C stabilization. Low rates of organic amendments, especially crop straw, are therefore recommended, as this practice can improve or at least maintain soil properties in degraded Mollisols, while minimizing the adverse impacts of more intense applications.

Organic and inorganic phosphorus forms in soil as affected by long-term application of organic amendments

Organic amendments contribute significantly to the phosphorus (P) supply in agroecosystems. However, their long-term effects on specific P forms in soils are not completely understood. The objective of this study was to investigate the concentration of organic P forms and inorganic P pools in soil and the activity of enzymes involved in the P turnover in a long-term field experiment running since 1998 in Northern Germany as affected by P amendments. The following treatments with different P supplies were sampled in 2012, 14 years after the establishment of the experiment: control (no P), cattle manure (manure), biowaste compost (compost), and biowaste compost in combination with triple-superphosphate (compost + TSP). The classification of organic P forms by using enzyme additions to NaOH–EDTA soil extracts showed non-hydrolyzable organic P as the dominant form in soil followed by inositol hexakisphosphate (Ins6P)-like P. Non-hydrolyzable and total organic P concentrations in soil were highest in the combined compost + TSP treatment, which received the highest amount of inorganic P. The values of the bioavailable P pools (water-extractable P and double lactate-extractable P) were in accordance with the P balance (P addition with the amendments minus P removal with harvested crops) independently of the type of amendment. The results of this research suggest that the distribution of soil P forms is more reliant on the turnover processes in the soil than on the forms of P added.

Erratum: The Effects of Long-term Application of Organic Amendments on Soil Organic Carbon Accumulation

Application of organic amendments (e.g., biosolids[BS], composts) to soil may provide an effective method for accumulating considerable amounts of C, but the long term stability of such C is not well known. We investigated study sites in Virginia to determine the amounts of C remaining in soils 7 to 27 yr following amending with biosolids and composts. The first study employed a Fauquier silty clay loam (fine, mixed, active, mesic Ultic Hapludalf) to which four treatments (control, poultry litter-yard waste compost, biosolids compost, and poultry litter) were continuously applied during 2000–2004. The second study was conducted on a Davidson clay loam (fine, kaolinitic, thermic, Rhodic Kandiudult) to which six rates of aerobically digested biosolids (0, 42, 84, 126, 168, and 210 Mg ha–¹) were applied in 1984. The third study was on a Pamunkey sandy loam (fine-loamy, mixed, semiactive, thermic Ultic Hapludalfs) to which five rates of anaerobically digested biosolids (0, 14, 42, 70, and 98 Mg ha–¹), with and without sawdust, were applied in 1996. Total soil organic C concentration and bulk density were measured to calculate C accumulation. The organic amendment-treated soils increased C in the surface soil depth (<15 cm), ranging from 2 to 12% of C across all three sites. Soil C movement was limited to a depth of 15 cm. Evidence of C saturation was revealed in the third study site. These results demonstrate that organic amendments applied over a long time remain in soil and may contribute to C sequestration in the Mid-Atlantic region.

Management of organic amendments in rice-wheat cropping system determines the pool where carbon is sequestered

Aim To study the impact of long-term application of organic amendments and fertilizer nitrogen on C sequestration and its distribution among various physical pools of soil organic matter in rice-wheat system.

Effects of organic amendments on soil carbon sequestration in paddy fields of subtropical China

Purpose Although organic amendments have been recommended as one of the practices for crop production and soil carbon sequestration, little has been done to evaluate soil organic carbon (SOC) dynamics following long-term application of organic amendments. The objective of this research were to (1) assess the effect of long-term organic amendments on SOC dynamics in rice-based systems; (2) evaluate the relationship between soil carbon sequestration and carbon input based on various mineral and organic fertilization treatments.

Heavy Metal Accumulation in a Sandy Soil and in Pepper Fruit Following Long-term Application Of Organic Amendments

Heavy metals are toxic and persistent pollutants that may be present in organic waste materials used as soil amendments. Following accumulation in amended soil, crop plants could assimilate these pollutants in sufficient concentrations to pose a threat to humans consumers. The Federal Clean Water Act and additional state regulations set minimum standards for heavy metals in organic amendments. Cumulative amounts of heavy metal pollutants that may be added to soils through amendments are regulated through national and state environmental protection agencies and the Federal Food and Drug Administration regulate maximum tolerances of heavy metal contaminants in food. The objective of the research was to study the effects of long-term organic amendment application on the accumulation of heavy metal pollutants in soil and subsequent contamination in pepper fruits. Organic amendments were applied yearly to replicate large plots during 1996 to 2000. Controls received no amendments. Different organic amendments were applied every year to simulate grower organic amendment availability throughout long-term application. Although higher levels of extractable Cd, Cu, Ni, Pb, and Zn were observed from amended soils during 1996 to 2000, all were within acceptable levels. Furthermore, no accumulation of Cd, Cu, Pb, and Ni was observed in pepper fruit. Therefore, long-term application of organic amendments made from waste materials with pollutant content below maximum acceptable levels under state and federal regulations should be suitable for vegetable production.