Water Treatment Residuals and Biosolids Co‐applications Affect Phosphatases in a Semi‐arid Rangeland Soil

Co‐application of biosolids and water treatment residuals (WTR) land has not been extensively studied but may be beneficial by sorbing excess biosolid‐borne or soil phosphorus (P) onto WTR, reducing the likelihood of off‐site movement. Reduction of excess soil P may affect the role of specific P‐cleaving enzymes. The research objective was to understand the long‐term effects of single co‐applications and the short‐term impacts of repeated co‐applications on soil acid phosphomonoesterase, phosphodiesterase, pyrophosphatase, and phytase enzyme activities. Test plots were 7.5 × 15 m with treatments consisting of three different WTR rates with a single biosolids rate (5, 10, and 21 Mg WTR ha^?1; 10 Mg biosolids ha^?1) surface co‐applied once in 1991 or reapplied in 2002. Control plots consisted of those that received no WTR–biosolids co‐applications and plots that received only 10 Mg biosolids ha^?1. Plots were sampled to a 5‐cm depth in 2003 and 2004, and soil phosphatases and phytase enzyme activities were measured. Soil phosphodiesterase activity decreased in WTR‐amended plots, and pyrophosphatase activity decreased with increasing WTR application rates. In contrast, acid phosphatase and phytase activity increased with WTR addition, with WTR application possibly triggering a deficiency response causing microorganisms or plants to secrete these enzymes. Biosolids and WTR co‐applications may affect enzymatic strategies for P mineralization in this study site. Reductions in phosphodiesterase activity suggest less P mineralization from biomass sources, including nucleic acids and phospholipids. Increased acid phosphatase and phytase activities indicate that ester‐P and inositol‐P may be important plant‐available P sources in soils amended with WTR.     

Improving the Physical and Chemical Properties of a Disturbed Soil Using Drying-bed Biosolids

Disturbed soils might be improved by increasing organic matter content. The objective of this study was to determine if a large application of drying-bed biosolids would improve soil productivity and promote bermudagrass (Cynodon dactylon) and establishment on the Trinity clay soil. Anaerobically digested, air-dried biosolids were applied to Trinity clay (very-fine, montmorillonitic, thermic, typic, pelludert) at rates of 0, 112, 560, and 1120 Mg ha^?1. The biosolids were incorporated into the top 15 cm of the soil and bermudagrass sprigs were planted. Biosolids significantly reduced soil bulk density and soil resistance to penetration when measured during the second and third years after the application. Biosolids increased soil concentrations of organic carbon, nutrients (nitrogen, phosphorus, copper, zinc, iron) and heavy metals (cadmium, chromium, nickel, lead). Bermudagrass biomass production and nutrient uptake were increased due to biosolids, but heavy metals were not significantly transferred from soil to above-ground plant tissue.     

Long‐Term Application of Biosolids on Apricot Production

Abstract

The use and disposal of biosolids, or wastewater treatment sludge, as a fertilizer and soil amendment is becoming increasingly widespread. We evaluated the multiyear use of biosolids in apricot (Prunus armeniaca L.) production, grown on productive agricultural soils. Class A biosolids were initially applied annually at rates of 0, 1.9, 5.8, and 11.7 Mg · ha^?1 (dry basis) to a 2‐year‐old apricot orchard on the USDA‐ARS research site on the eastern side of the San Joaquin Valley, CA. These application rates provided estimated rates of 0 (control), 57, 170, and 340 kg total N · ha^?1 yr^?1, respectively. Compared to the control treatment, the applications of biosolids significantly increased soil salinity (electrical conductivity from 1:1 soil–water extract) and total concentrations of nutrients [e.g., calcium (Ca), magnesium (Mg), sulfur (S), phosphorus (P), zinc (Zn), and copper (Cu)] after 7 years but did not increase the concentrations of selected metals [cadmium (Cd), chromium (Cr), cobalt (Co), nickel (Ni), and lead (Pb)] between 0‐ and 60‐cm soil depths. Mean concentrations of total nitrogen (N) and carbon (C) in soils (0‐ to 15‐cm depth) ranged from a low of 1.3 g kg^?1 to a high of 5.2 g · kg^?1 and from 14.1 g · kg^?1 to 45.7 g · kg^?1 for the control and high biosolids treated soils, respectively.

Biosolids applications did not lead to fruit yield reductions, although fruit maturation was generally delayed and more fruits appeared at picking times at the high rate of application. Yellow fruits collected from all biosolids applications were significantly firmer than were fruit collected from control trees, and they had higher concentrations of Ca, potassium (K), S, iron (Fe), and Zn in the fruit. Among the fruit quality parameters tested, the juice pH, total acidity, and fruit skin color were not significantly affected by biosolids applications. Malic acid concentrations decreased most of the time, while citric acid concentrations increased with increasing rates of biosolids applications. Overall, our results suggest that nonindustrial biosolids applied at an annual rate at or less than 11.7 Mg N · ha^?1 (340 kg N · ha^?1) can be safely used for apricot production on sandy loam soils.     

Utilization of Compost Increases Organic Carbon And Its Humin,Humic and Fulvic Acid Fractions In Calcareous Soil

Organic carbon sustainability in a gravelly calcareous soil is a great challenge under the humid conditions of south Florida. The beneficial effects of compost utilization on soil fertility prompted an investigation on (i) accumulation of total organic carbon and (ii) the soil organic carbon (SOC) in humin, humic acid (HA) and fulvic acid (FA) fractions in a gravelly calcareous soil amended with composts or inorganic fertilizer. In 1996 and 1998, compost from municipal solid waste (MSW) (100% MSW), Bedminster cocompost (75% MSW and 25% biosolids) and biosolids compost (100% biosolids) at 72, 82.7 and 15.5 Mg ha^?1, respectively, were each incorporated in soil beds and inorganic fertilizer (6-2.6-10) NPK at 2.8 Mg ha^?1. A control (no amendment) treatment was also included. Total organic carbon and various fractions of soil organic carbon were determined in two depths (0-10 and 10-22 cm) for both soil particles (< 2mm) and pebbles (> 2mm). Inorganic and organic soil amendments had decreased soil pH and increased soil electrical conductivity (EC) 19 months from initial application. Total organic carbon contents in soil particle were 4-, 3-, and 2-fold higher in MSW compost, Bedminster cocompost and biosolids compost treatments, respectively, than those in fertilizer treated or non-treated soils. MSW compost increased total organic carbon in pebbles by 4- and 3-fold in the 0-10 and 10-22 cm deep layers, respectively, more than other treatments. The soil organic carbon accumulation decreased with depth in all treatments in soil particles, but did not in pebbles. Amending soils with MSW compost significantly increased the organic carbon in humin, HA and FA fractions more than those treated with inorganic fertilizer or non-amended. MSW compost has a potential to be used as a soil amendment to increase and sustain the organic carbon in calcareous soils of south Florida.     

Nitrogen Availability for Maize from a Rolling Pampa Soil After Addition of Biosolids

Abstract

The objective of this paper was to evaluate the influence of different rates of biosolids on the soil nitrogen (N) availability for maize and its residuality. A field experiment was developed in a typic Argiudol located in the NE of the Buenos Aires Province. Maize was sown for two consecutive years 1997–1999. Biosolids from a sewage treatment plant of Buenos Aires outskirts were superficially applied to the soil and incorporated by plowing. There were eight treatments: Check; 8, 16, and 24 Mg of dry biosolid ha^?1; 8 and 16 Mg of dry biosolid ha^?1 applied one year before, 100 and 150 kg N ha^?1 of calcium ammonium nitrate (CAN). The sampling and determinations were done during the second maize cycle. At presowing (PS), sowing (S), 6 expanded leaves (V6), 12 expanded leaves (V12), and Flowering (Fl) composite soil samples from 0–40 cm depth were obtained to determine ammonium and nitrate contents. At Fl maize plants were sampled in order to determine total biomass and N content. The N‐nitrate content in the soil was significantly increased by the biosolids application (p < 0.05), and varied for each increment depending on the biosolids rates and the phenological stage. After 30 days from the incorporation the increases of 1.19, 1.34, and 2.05% were observed for N‐nitrates for 8, 16, and 24 Mg ha^?1, respectively. The contribution of mineral N from the biosolids was 2.48, 6.46, and 5.01 kg N Mg^?1 when the rates were incremented from 0–8, 8–16, and 16–24 Mg ha^?1, respectively. The nitrogen mineralization followed a release pattern with a maximum value of 296 kg N‐nitrate ha^?1 at sowing for 24 Mg ha^?1. Since then, the release of mineral nitrogen decreased significantly till Fl. The N‐nitrates values variation with the temperature adjusted to polinomic functions. The mineral N released from the biosolids increased as a response to the increment of soil temperature and then decreased due to the maize nitrogen absorption and the potentially mineralized nitrogen exhaustion. The application of 150 kg N ha^?1 as CAN incremented significantly the soil N‐nitrate content and equalized 16 and 24 Mg of dry biosolids ha^?1 at V6. But, no synchronism between the high nitrate releasing from biosolids and the increment in the nitrogen absorption by maize was observed. This fact generates a surplus of nitrate that incremented the potential of nitrogen loss by lixiviation. We observed a residual effect from the biosolids that were applied the previous year. This contribution represented the 35% of the maize requirements and was similar to the nitrate content observed in Bio 16. The biosolids might be a valuable source of nitrogen for maize crop if the synchronism between the soil supply and maize demand is observed in order to avoid nitrates surplus.     

Growth and metal uptake of edamame [Glycine max (L.) Merr.] on soil amended with biosolids and gypsum

ABSTRACT

Although biosolids are a rich source of plant nutrients, there is concern about the potential heavy metal uptake by crops grown on biosolid-amended soils. This study was conducted to determine the effects of limed or composted biosolids and flue gas desulfurization gypsum (FGDG) on edamame growth, nodule development, and metal uptake. Two consecutive crops of edamame were grown on 40 and 80 T ha^?1 biosolid-amended soil with and without 10 T ha^?1 FGDG. Biosolids with or without FGDG did not reduce biomass, nodules, or grain yields in the first harvest and increased yields of all three tissues in the second harvest. Lead and cadmium concentrations in grain and biomass were below the instrument detection limits. Copper, manganese, and zinc were within the ranges normally found in soybean grain. In this pot study, biosolids and FGDG did not reduce edamame growth or increase grain metal concentrations to levels of concern.     

Soil restoration in semiarid Patagonia: Chemical and biological response to different compost quality

Restoration of soils burned by a wildfire using composted amendments of different origin (biosolids and municipal organic wastes) and final particle size (screened and unscreened) was studied after 6 and 12 months of application in a field trial in semiarid NW Patagonia. Composts were applied at 40 Mg ha⁻¹. A fertilized treatment with soluble N (100 kg ha⁻¹) and P (35 kg ha⁻¹), and a non-treated control were also included. As indicators of soil response, chemical (electrical conductivity, pH, organic C, total N, extractable P), biological (potential microbial respiration, potential net N mineralization, N retained in microbial biomass) and physical (temperature and soil moisture) properties were evaluated. Plant soil cover was also estimated. Soil chemical and biological properties showed a high response to organic amendment addition, more evident after the wet season (12 months of application). Soil organic C, total N and extractable P increased significantly with biosolids composts (BC), and soil pH with municipal composts (MC). Potential microbial C respiration and net N mineralization were similar for both MC and BC, and significantly higher than in the control and the inorganic fertilized treatment; when calculated on C or N basis the highest values corresponded to MC. Results imply that in terms of organic C accretion, BC were more effective than MC due to higher amounts of total and recalcitrant C. Screened and unscreened composts did not differ significantly in their effects on soil properties. The increase of organic C with BC did not contribute to increase soil moisture, which was even higher in control plots after the wet season; higher plant cover and water consumption in amended plots could also explain this pattern. Inorganic fertilization enhanced higher plant cover than organic amendments, but did not contribute to soil restoration.     

Chemical structure of humic acids in biosolids-amended soils as revealed by NMR spectroscopy

We used NMR spectroscopy to characterize humid acids extracted from soils that had received long-term application of 2 levels of biosolids to evaluate the soil organic matter (SOM) stability in biosolids-amended soils. The study also quantified fulvic acids (FAs), humic acids (HAs) and Fe/Al oxides. The soils were collected in 2004 from 7 fields, in Fulton County, southwestern Illinois, which received biosolids at a cumulative rate of 0 (control), 554 (low biosolids) and 1,066 (high biosolids) Mg ha⁻¹. The application of biosolids increased both FA and HA contents, but biosolids-amended soil and control soil did not differ in FA/HA ratio. Biosolids application had no effect on water-soluble organic carbon content. Biosolids application increased the presence of Fe/Al in the SOM complex and lowered its C/Fe and C/Al ratios. ¹³C NMR spectra showed increased alkyl C and decreased aromatic C content in soil HAs with the application of biosolids, and the extent of such changes was higher with high than low biosolids treatment. Under biosolids application, the soil HAs’ C structure shifts from O-alkyl-dominant to alkyl-dominant. Biosolids application does not decrease SOM stability but rather increases the stability of soil humic substances.     

Influence of compost/sludge application on sugarcane yield and nitrogen requirement on a sand soil

Mineral soils in southern Florida are very low in organic matter content and most of the nitrogen (N) for sugarcane (Saccharum spp.) must be supplied in split fertilizer applications. Information is needed regarding how the interaction of organic amendments and fertilizer N influences sugarcane yields. A field study on a sand soil (Alfisol) was established to determine (1) potential sugarcane yield benefits of a compost/sludge amendment, and (2) the influence of the amendment on N fertilizer requirement. A split-plot Latin square design was used with five N rates (main plots) and presence or absence of compost/sludge broadcast at 113 m³ ha^?1 (subplots). Annual N rates were 0, 67, 134, 202, and 269 kg N ha^?1. Compost/sludge application increased cumulative t sucrose ha^?1 by 36% averaged across N rates. The amendment also lowered annual N requirement by an average of 38%, but maintenance applications of compost/sludge will be required every four years.     

Effects of Biochar and Biosolid on Adsorption of Nitrogen,Phosphorus, and Potassium in Two Soils

Increasing the retention of nutrients by agricultural soils is of great interest to minimize losses of nutrients by leaching and/or surface runoff. Soil amendments play a role in nutrient retention by increasing the surface area and/or other chemical processes. Biochar (BC) is high carbon-containing by-product of pyrolysis of carbon-rich feedstocks to produce bioenergy. Biosolid is a by-product of wastewater treatment plant. Use of these by-products as amendments to agricultural soils is beneficial to improve soil properties, soil quality, and nutrient retention and enhance carbon sequestration. In this study, the adsorption of NH₄-N, P, and K by a sandy soil (Quincy fine sand (QFS)) and a silty clay loam soil (Warden silty loam (WSL)) with BC (0, 22.4, and 44.8 mg ha^?1) and biosolid (0 and 22.4 mg ha^?1) amendments were investigated. Adsorption of NH₄-N by the QFS soil increased with BC application at lower NH₄-N concentrations in equilibrium solution. For the WSL soil, NH₄-N adsorption peaked at 22.4 mg ha^?1 BC rate. Biosolid application increased NH₄-N adsorption by the WSL soil while decreased that in the QFS soil. Adsorption of P was greater by the WSL soil as compared to that by the QFS soil. Biosolid amendment significantly increased P adsorption capacity in both soils, while BC amendment had no significant effects. BC and biosolid amendments decreased K adsorption capacity by the WSL soil but had no effects on that by the QFS soil. Ca release with increasing addition of K was greater by the WSL soil as compared to that by the QFS soil. In both the soils, Ca release was not influenced by BC amendment while it increased with addition of biosolid. The fit of adsorption data for NH₄-N, P, and K across all treatments and in two soils was better with the Freundlich model than that with the Langmuir model. The nutrients retained by BC or biosolid amended soils are easily released, therefore are readily available for the root uptake in cropped soils.     

Soil enzyme activities,microbial community composition and function after 47 years of continuous green manuring

Green manuring practices can influence soil microbial community composition and function and there is a need to investigate the influence compared with other types of organic amendment. This study reports long-term effects of green manure amendments on soil microbial properties, based on a field experiment started in 1956. In the experiment, various organic amendments, including green manure, have been applied at a rate of 4 t C ha⁻¹ every second year. Phospholipid fatty acid analysis (PLFA) indicated that the biomass of bacteria, fungi and total microbial biomass, but not arbuscular mycorrhizal (AM) fungi, generally increased due to green manuring compared with soils receiving no organic amendments. Some differences in abundance of different microbial groups were also found compared with other organic amendments (farmyard manure and sawdust) such as a higher fungal biomass and consequently a higher fungal/bacterial ratio compared with amendment with farmyard manure. The microbial community composition (PLFA profile) in the green manure treatment differed from the other treatments, but there was no effect on microbial substrate-utilization potential, determined using the Biolog EcoPlate. Protease and arylsulphatase activities in the green manure treatment were comparable to a mineral fertilized treatment receiving no additional C, whereas acid phosphatase activity increased. It can be concluded that green manuring had a beneficial impact on soil microbial properties, but differed in some aspects to other organic amendments which might be attributed to differences in quality of the amendments.     

On-Site Assessment of Extractable Soil Nutrients after Long-Term Biosolid Applications to Perennial Forage

The objective of this study was to evaluate soil nutrient loading and depth distributions of extractable nitrogen (N), phosphorus (P), and potassium (K) after long-term, continuous annual surface applications of anaerobically digested class B biosolids at a municipal recycling facility in central Texas. Commercial forage production fields of coastal bermudagrass (Cynodon dactylon L.) were surface applied at 0, 20, 40, or 60 Mg dry biosolids ha^?1 y^?1 for 8 years. Application duration was evaluated in fields treated with 20 Mg dry biosolids ha^?1 y^?1 for 0, 8, or 20 years. Total soil loads of extractable inorganic N and P increased linearly with application rate, but only extractable P increased with duration. Neither total load nor soil distribution of extractable K was affected by biosolid applications. Mineralization of biosolid-derived organic N and P likely contributed to elevated concentrations of nitrate throughout the soil profile (0–110 cm) and orthophosphate in surface soils (0–40 cm).     

Clay addition to lime-amended biosolids overcomes water repellence and provides nitrogen supply in an acid sandy soil

The addition of clay to lime-amended biosolids has been proposed as a soil amendment (LaBC^®) for remediating acidic-sandy soil. We investigated whether the presence of clay in LaBC^® altered soil microbial processes over a 30-week period. Aerobic-incubation and CO₂ respiration assays were used to monitor water repellence and chemical and microbiological properties of amended soil. Dry LaBC^® was applied at equivalent wet weight of 50, 100 and 150 t ha^?1. In addition, dry components of LaBC^® (lime, clay, lime + clay (LAC) and lime + biosolids (LAB)) were applied separately at rates equivalent to their fractions within LaBC^®. Inclusion of clay in LaBC^® was effective in eliminating water repellence at all application rates. Inclusion of clay in LaBC^® decreased nitrogen (N) release from the biosolids (by 58 %), even at 50 t ha^?1, but only during the first 2 weeks of incubation. LaBC^® consistently decreased soil microbial respiration compared with LAB alone when applied at 150 t ha^?1 thereby protecting organic matter decomposition. There was no significant N release with lime and clay amendment alone or in combination (LAC) in the absence of the biosolids. There may be a complex interaction between clay, lime and organic matter, but each may have had a role in altering N release from biosolids at different times during the 30-week incubation. Addition of clay to LAB increased its effectiveness in remediating this water-repellent, acidic-sandy soil and prolonged the N release from the biosolids following soil amendment.     

Changes in cadmium and zinc phytoavailability in agricultural soil after amendment with papermill sludge and biosolids

Abstract

The co‐disposal of papermill sludge with biosolids is seen as an alternative soil amendment to papermill sludge and inorganic fertilizer. The objectives of this study were to assess the suitability of co‐disposal of papermill sludge and biosolids by measuring changes in the soil physicochemical properties and the phytoavailability of cadmium (Cd) and zinc (Zn). Biosolids were applied with papermill sludge as an alternative source of N to inorganic fertilizers at rates calculated on the basis of C:N ratios of the amendments and common papermill sludge disposal practices. Perennial ryegrass (Lolium perenne L.) was grown on amended soils for 6 months under glasshouse conditions. The papermill sludge amendment alone increased soil pH and the rate of carbon degradation compared to the control (no amendment) and biosolid co‐disposal amendment. There was no difference in dry matter yield per pot of ryegrass between the treatments. Cadmium concentrations in plant tissue increased through the trial with the application of biosolids and papermill sludge. These findings were correlated well with the sorption properties of the soils for Cd as derived from isotherms. However, Zn uptake was unaffected by the application of the papermill sludge and biosolids.     

Improving Soil Quality and Increasing Peanut Production by Addition of Composted Green Waste and Carbonized Rice Hull Amendments

Increased population pressure coupled with unsustainable cropland management has resulted in soil degradation and a decline in crop productivity in China. This study tested the hypothesis that the soil with combined addition of composted green waste (CGW) and carbonized rice hulls (CRHs) as amendments will improve soil properties and increase peanut production. Some selected parameters of soil and peanut plant were measured, which were best if the soil was amended with 35 t ha^?1 CGW and 10 t ha^?1 CRH and were worst in the nonamended soil. Relative to the soil without amendment addition, amendment of the soil with 35 t ha^?1 CGW and 10 t ha^?1 CRH increased seed yield, total pod yield, root nodule number, and nodule dry weight by 50.0, 52.4, 55.4, and 57.9%, respectively, and increased total Kjeldahl nitrogen, total phosphorus, total potassium, and total chlorophyll content of plants by 53.2, 54.4, 53.7, and 56.8%, respectively.     

A glass house trial to investigate the impact of water treatment sludge and green waste compost to enhance the revegetation of contaminated sites

This study investigated the use of waste amendments (green waste compost (GWC) and water treatment sludge (WTS) cake) in improving the nutrient and revegetation status of contaminated soil obtained from a former industrial site that has heavy metal and hydrocarbon contamination. The waste amendments were mixed with the contaminated soil at application rates equivalent to 90 and 180 t ha^?1 (wet weight) and placed in plastic pots. The unamended soil serves as the control. Reed canary grass and white mustard were allowed to grow on the amended and unamended contaminated soil in the glass house. After a 30- day growth period, soil nutrient status was observed and was found to be higher in the amended contaminated soil than the control. In the amended soil, organic matter, total nitrogen, total potassium and soil nitrate were highest in contaminated soil amended with GWC at 180 t ha^?1 and lowest in contaminated soil amended with WTS cake at 90 t ha^?1. Above-ground dry mass of reed canary grass and white mustard grown on amended contaminated soil increased by 120–222% and 130–337%, respectively, as compared to the control, showing that improved fertility of contaminated soils thereafter, enhanced revegetation.     

Leachability of Nitrate from Sandy Soil using Waste Amendments

Environmental issues associated with intensive use of nitrogenous fertilizers have generated an interest in alternative management systems. An experiment was conducted to mitigate nitrate leaching from sandy soil using different waste materials such as charcoal, manure, sawdust, wood ash, and control (no amendment). Urea was applied at the rate of 300 kg nitrogen (N) ha^?1. Nitrate was determined during six leaching events. During an incubation experiment, nitrate release was also determined in soil amended with charcoal at the rates of 0, 10, 20, and 40 t ha^?1. Urea was applied at the rates of 0, 100, 200, 400, and 1000 ppm N. Results indicated that urea application increased nitrate (NO₃) concentration in leachate. Soil amendments substantially reduced NO₃ in leachates irrespective of the type of material used. Waste amendments differed for NO₃ leaching as follows: charcoal < wood ash < sawdust < manure. Leaching of NO₃ enhanced up to the fourth leaching event and thereafter reduced significantly. Nitrate retention in soil varied among material in the order of manure > charcoal > wood ash > sawdust. Nitrate accumulation occurred in the lower layer (25–50 cm) of soil column after the leaching process. Application of charcoal retained greater NO₃ level as compared to control soil during an incubation. Enhanced urea applications also enhanced NO₃ release. This experiment suggests that waste material can be viably recycled to mitigate NO₃ concentration in water.     

协助自然修复微量元素污染酸性土壤研究：8年田间试验

There are many remediation techniques for organic contaminated soils,but relatively few of them are applicable to trace elementcontaminated soils.A field experiment was carried out to investigate assisted natural remediation（ANR） of an acid soil contaminated by As,Cd,Cu,Zn and Pb using one inorganic amendment,sugar beet lime（SL）,and two organic amendments,biosolid compost（BC）and leonardeite（LE）.The experiment was arranged in a completely randomized block design with four treatments in three replicates:1) a non-amended control（NA）;2) SL amended at 30 Mg ha^-1 year^-1;3) BC amended at 30 Mg ha^-1 year^-1 and 4) LE amended at 20 Mg ha^-1 year^-1 plus SL amended at 10 Mg ha^-1 year^-1（LESL）.The amended plots received two doses of each amendment（DO2）:one in October 2002 and another in October 2003.The plots were then divided in half into two subpolts and one subplot received another two doses of the same amendments（DO4） in October 2005 and October 2006.In 2011,the pH values of the amended soils were greater than that of the NA soil,with the SL-amended soil showing the highest pH.Total organic carbon（TOC） was also greater in the amended soil,and greater with DO4 than with DO2.Amendments reduced the concentrations of 0.01 mol L^-1 CaCl₂-extractable Cd,Cu and Zn,especially in the SL-amended soil.Plant cover of colonizing vegetation was enhanced by amendments,but was independent of amendment doses.Changes in soil properties from 2003 to 2011 showed that the first amendment application of DO2 caused a high differentiation between all the amendment treatments and the NA treatment.After the second application of DO2,soil pH and TOC continued increasing slowly.Further two applications of amendments（DO4） caused differences only in the organic treatments.Plant cover increased over time in all the treatments including NA.It could be concluded that the slow and steady natural remediation of this soil could be enhanced by amendment application（ANR）.     

Plant and Soil Responses to the Combined Application of Organic Amendments and Inorganic Fertilizers in Degraded Sodic Soils of Indo-Gangetic Plains

ABSTRACT

Soil degradation due to salinization and sodication is the paramount threat in Indo-Gangetic plains. The studies on reclamation and management of such soils can provide a pragmatic solution for improving fertility and productivity of these soils. Lack of organic matter and poor availability of nutrients are the major factors for low productivity of sodic soils. Rice-wheat is a major cropping system in Indo-Gangetic alluvial plain region even in reclaimed sodic soils and farmers used inorganic fertilizers only to get higher yields. In this study, we used different organic sources of amendments in conjunction with different nitrogen (N) doses supplied through inorganic fertilizers to investigate the combined effect of organic and inorganic amendments on soil fertility and the productivity of rice- wheat system in sodic soils. Salt tolerant varieties of rice and wheat were grown in sodic soil (pH: 9.30, EC: 1.12 dSm^?1 and exchangeable sodium percentage, ESP: 52) during 2014–15 to 2016–17 in a field experiment with 13 treatment combinations of organic and inorganic amendments (T₁- (control) 100% of recommended dose of N (RDN), T₂-municipal solid waste compost (MSWC) @10 t ha^?1 + 50%RDN, T₃- MSWC @10 t ha^?1 + 75% RDN,T₄- MSWC @10 t ha^?1 + 100%RDN, T₅-Vermicompost (VC) @10 t ha^?1 + 50% RDN, T₆- VC @10 t ha^?1 + 75% RDN, T₇-VC@10 t ha^?1 + 100% RDN, T₈- Farm yard manure (FYM) @ 10 t ha^?1 + 50% RDN,T₉- FYM@10 t ha^?1 + 75%RDN, T₁₀- FYM@10 t ha^?1 + 100% RDN, T₁₁-Pressmud (PM) @10 t ha^?1 + 50% RDN, T₁₂-PM@10 t ha^?1 + 75%RDN, and T₁₃- PM @ 10 t ha^?1 + 100% RDN). Use of organic amendments supplemented with reduced dose of N through inorganic fertilizer has significantly improved soil bio-physical and chemical properties. Application of VC@10 t ha^?1 + 100% RDN (T₇) decreased soil bulk density, pH, EC, ESP and Na content to 2.0, 4.2, 26.5, 42.8, and 56.6% respectively and increased soil organic carbon by 34.6% over control (T₁). Soil fertility in terms of available N, P, K, Ca, and Mg increased by 20.5, 33.0, 36.4, and 44%, respectively, over control (T₁). Soil microbial biomass carbon, nitrogen, and phosphorus also improved significantly due to combined use of organic amendments and inorganic fertilizers over the only use of inorganic fertilizers. Decreasing in soil sodicity and increasing soil fertility showed significant increase (P < 0.05) in crop growth, growth indices, and grain yields of rice and wheat. The study revealed that combined use of VC or MSW compost @10 t ha^?1 in conjunction with 75% RDN through inorganic fertilizers in sodic soils proved sustainable technology for restoration of degraded sodic soils and improving crop productivity.     

Sugarcane yield response to calcium silicate on Florida mineral soils

Abstract

Silicon (Si) is a beneficial nutrient for sugarcane (Saccharum spp.) and yield responses to Si amendment have been determined on soils with low soluble Si. Because a soil test Si calibration has not been published for sugarcane grown on Florida mineral soils, the objectives were to determine sugarcane yield response to silicon soil amendment on two mineral soils (Entisol and Spodosol) and to relate sucrose yield to soil-extractable Si. Calcium silicate application rates were 0, 3.4, and 6.7?Mg ha^?1 (Site 1) and 0, 2.2, 4.5, and 6.7?Mg ha^?1 (Site 2) in small-plot (120 m² plot^?1) experiments, with Si application resulting in significant increases in biomass and sucrose ha^?1. Calcium silicate requirements of 6.7 and 4.3?Mg ha^?1 were determined with initial acetic acid-extractable Si of 21 and 46?g m^?3, respectively. Nonlinear models indicated that Si amendments will be required with acetic acid-extractable Si <105?g m^?3.