Soil management for raising crop water productivity in rainfed production systems in Lao PDR

This study investigated the impacts of organic- and clay-based soil amendments, and their combinations on crop water productivity (CWP) using maize as a test crop. On-station field trials were established over two consecutive years at the Naphok and Veunkham sites in Laos. At each site, 10 treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (10 t ha^?1), bentonite clay (10 t ha^?1), compost (4 t ha^?1), clay-manure compost (10 t ha^?1), rice husk biochar compost (10 t ha^?1), bentonite clay + biochar, bentonite-clay + compost, biochar + compost, and bentonite clay + biochar + compost. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in CWP and growing period evapotranspiration were determined. At Naphok, differences between the amended and control plots in CWP varied between 0.1 and 0.6 kg m^?3 in 2011 and from 0.1 to 0.4 kg m^?3 in 2012, whereas differences at Veunkham varied between 0.3 and 1.0 kg m^?3 in 2011 and from 0.05 to 0.29 kg m^?3 in 2012. At both sites, CWP in 2012 was significantly lower than 2011. Our results illustrate that organic- and clay-based soil amendments improve CWP, indicating that soil-based interventions could be suitable options for improving agricultural productivity.     

Effect of carbofuran on enzymatic activities and growth of tomato plants in natural,fertilized and vermicompost-amended soils

The effects of carbofuran, a widely used carbamate pesticide, on soil enzymatic activities such as fluorescein diacetate hydrolysis (FDAH), dehydrogenase, and acid and alkaline phosphatases were studied at different time intervals in unamended soil and soil amended with inorganic fertilizers and vermicompost, cropped with tomato plants. The results showed that all enzymatic activities varied with carbofuran application rates and increased significantly up to 1.0 kg active ingredient (a.i.) ha^?1 dose of carbofuran. The most significant increase was observed at 0.20 kg a.i. ha^?1 dose both in unamended and amended soils. This showed that carbofuran was not toxic to all enzymatic activities studied upto 1.0 kg a.i. ha^?1 dose of carbofuran in both systems. A significant decrease in all enzymatic activites were observed at higher dose of carbofuran both in unamended and amended soils relative to their respective controls. Highest enzymatic activities were observed in vermicompost amended soil and minimum in fertilized soil compared to control. The results indicated that the growth of tomato plants was significantly higher at 0.20 kg a.i. ha^?1 dose of carbofuran in all the cases and followed the order: fertilized soil > vermicompost amended soil > natural soil and was positively correlated with the enzyme activities.     

Sustainability of in situ remediation of Cu- and Cd-contaminated soils with one-time application of amendments in Guixi,China

Purpose

In situ immobilization of heavy metal-contaminated soils with the repeated incorporation of amendments can effectively reduce the bioavailability of soil heavy metals. However, the long-term application of amendments would lead to the destruction of soil structure and accumulation of soil toxic elements, ultimately affecting food security and quality. Thus, the sustainability of the amendments in a heavy metal-contaminated soil was evaluated from 2010 to 2012.

Materials and methods

Batch field experiments were conducted in the soils, which were amended with apatite (22.3 t ha^?1), lime (4.45 t ha^?1), and charcoal (66.8 t ha^?1), respectively. The amendments were applied only one time in 2009, and ryegrass was sown each year. Ryegrass and setaria glauca (a kind of weed) were harvested each year. Concentrations of copper (Cu) and cadmium (Cd) were determined by batch experiments. Five fractions of Cu and Cd were evaluated by a sequential extraction procedure.

Results and discussion

Ryegrass grew well in the amended soils in the first year, but it failed to grow in all the soils in the third year. However, setaria glauca could grow with higher biomass in all the amended soils. The treatment of apatite combined with plants was more effective than lime and charcoal treatments in removing Cu and Cd from the contaminated soils by taking biomass into account. Apatite had the best sustainable effect on alleviating soil acidification. The Cu and Cd concentrations of CaCl₂-extractable and exchangeable fractions decreased with the application of amendments. Moreover, apatite and lime could effectively maintain the bioavailability of Cu and Cd low.

Conclusions

Apatite had a better sustainable effect on the remediation of heavy metal-contaminated soils than lime and charcoal. Although all the amendment treated soils did not reduce soil total concentrations of Cu and Cd, they could effectively reduce the environmental risk of the contaminated soils. The findings could be effectively used for in situ remediation of heavy metal-contaminated soils.

     

Effect of biochar amendment on soil physical,chemical and biological properties and groundnut yield in rainfed Alfisol of semi-arid tropics

The aim of this study was to evaluate the effect of biochar and organic soil amendments on soil physicochemical and microbial load, carbon sequestration potential, nutrient uptake and yield of groundnut in acidic red soil under rainfed condition. Biochar was prepared from red gram, cotton, maize stalk and mesquite wood using pilot scale slow pyrolysis biochar unit. The above sources of biochar at the rate of 2.5 and 5 t ha^?1 and enriched farmyard manure 0.75 t ha^?1, composted coir pith 10 t ha^?1 and arbuscular mycorrhizae 100 kg ha^?1 were applied as basal with required nitrogen, phosphorous and potassium fertilizer. Biochar amendment at the rate of 5 t ha^?1 reduced the bulk density from 1.41 to 1.36 g cm^?3 and increased the soil moisture 2.5%. With respect to soil chemical changes, it raised soil pH from 5.7 to 6.3; increased the cation exchange capacity 1.4 cmol⁺ kg^?1 and enhanced the carbon buildup 4.4 t ha^?1. The significant differences in bacteria, fungi and actinomycetes population were observed between biochar and control. The nitrogen, phosphorous and potassium were better utilized under biochar and composted coir pith, which was 21, 5 and 20 kg ha^?1 higher than control. The experimental results suggested that application of biochar to acidic red soil favoured good soil physical, chemical and biological environment, and these positive changes influenced growth and yield attributes and enhanced pod yield 29% over control.     

Remediation of a Sandy Soil Contaminated with Cadmium,Nickel, and Zinc using an Insoluble Polyacrylate Polymer

Abstract

This study was carried out to investigate whether an insoluble polyacrylate polymer could be used to remediate a sandy soil contaminated with cadmium (Cd) (30 and 60 mg Cd kg^?1 of soil), nickel (Ni) (50 and 100 mg Ni kg^?1 of soil), zinc (Zn) (250 and 400 mg Zn kg^?1 of soil), or the three elements together (30 mg Cd, 50 mg Ni, and 250 mg Zn kg^?1 of soil). Growth of perennial ryegrass was stimulated in the polymer‐amended soil contaminated with the greatest amounts of Ni or Zn, and when the three metals were present, compared with the unamended soil with the same levels of contamination. Shoots of plants cultivated in the amended soil had concentrations of the metals that were 24–67% of those in plants from the unamended contaminated soil. After ryegrass had been growing for 87 days, the amounts of water‐extractable metals present in the amended soil varied from 8 to 53% of those in the unamended soil. The results are consistent with soil remediation being achieved through removal of the metals from soil solution.     

Biochar use in a legume–rice rotation system: effects on soil fertility and crop performance

The aim of this study was to determine whether by applying biochar, it is possible to augment the beneficial effects of legume–crop rotation systems on soil fertility and crop performance. Repeated experiments were established in 2012 and 2013 in South-western Benin using a split-split plot design. Two legumes, Mucuna pruriens (mucuna) and Vigna unguiculata (cowpea), were planted for 42 days on biochar-amended and unamended plots and subsequently cut and applied as mulch 5 days before planting rice. Rice plants were either fertilized or not using a fertilizer rate of 60, 30, and 30 kg ha^?1 of N, P₂O₅, and K₂O, respectively. The results showed that the application of legume green manures and fertilizer, either singly or in combination, improved soil nutrient availability, CEC, shoot yield, and grain yield of rice on both biochar-amended and unamended plots. However, the effect was significantly (p < 0.05) greater on biochar-amended plots. The mean grain yield for all cropping seasons was 1.8 t ha^?1 for biochar-amended plots and 1.3 t ha^?1 for unamended plots. The greater grain yield of rice on biochar-amended plots was associated with improved soil fertility and increased N uptake.     

Long-term amendment of four different compost types on a loamy silt Cambisol: impact on soil organic matter,nutrients and yields

This study investigated the long-term effects of different composts (urban organic waste compost (OWC), green waste compost (GWC), cattle manure compost (MC) and sewage sludge compost (SSC)) compared to mineral fertilisation on a loamy silt Cambisol, after a 7-year start-up period. The compost application rate was 175 kg N ha^?1, with 80 kg mineral N ha^?1 and without. Soil characteristics (soil organic carbon (SOC), carbon-to-nitrogen (C/N) ratio and soil pH), nutrients (nitrogen (N), phosphorous (P) and potassium (K)) and crop yields were investigated between 1998 and 2012. SOC concentrations were increased by compost applications, being highest in the SSC treatments, as for soil pH. N contents were significantly higher with compost amendments compared to mineral fertilisation. The highest calcium-acetate-lactate (CAL)-extractable P concentrations were measured in the SSC treatments, and the highest CAL-extractable K concentrations in the MC treatments. Yields after compost amendment for winter barley and spring wheat were similar to 40 kg mineral N ha^?1 alone, whereas maize had comparable yields to 80 kg mineral N ha^?1 alone. We conclude that compost amendment improves soil quality, but that the overall carbon (C) and N cycling merits more detailed investigation.     

Application of Adjoint-based Forecast Sensitivities to Asian Dust Transport Events in Korea

Phytoremediation is an attractive, economic alternative to soil removal and burial methods to remediate contaminated soil. However, it is also a slow process. The effect of humic acid in enhancing B and Pb phytoextraction from contaminated soils was studied (pot experiment) using transplanted vetiver grass (Vetiveria zizanioides (L.) Nash). Boron was applied at 0, 45, 90 and 180 kg B ha^?1 soil (as H₃BO₃) in 16 replicates. Of the 64 pots, four pots each were treated with 0, 100, 200 and 400 kg ha^?1 humic acid (HA) solution. In a separate experiment, Pb was applied (as Pb(NO₃)₂) at 0, 45, 90 and 180 kg Pb ha^?1 prior to addition of HA solutions at levels identical to the B experiment. Experiments were conducted using a randomized complete block design with four replicates. Vetiver grass was harvested 90 days after planting. Lead addition beyond 45 kg Pb ha^?1 decreased Pb uptake mostly due to a yield decline. Humic acid application increased Pb availability in soil and enhanced Pb uptake while maintaining or enhancing yield. An application of 200 kg HA ha^?1 was optimal for maintaining yield at elevated Pb levels. Boron application did not impact yield but greatly increased B content of roots and shoot. Boron uptake was greatest upon addition of 400 kg HA ha^?1. We conclude that HA addition to vetiver grass can be an effective way to enhance phytoremediation of B and Pb but optimum rates differ depending on soil B and Pb contamination levels.     

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.     

Effect of Municipal Solid Waste Compost and Farmyard Manure Application on Heavy‐Metal Uptake in Wheat

The risks related to municipal solid waste compost application in comparison to farmyard manure and mineral fertilizers on durum wheat were investigated on a short‐term experiment. Compost was applied at 40 t ha^?1 and 80 t ha^?1 with or without chemical fertilizers. Analogously, farmyard manure was applied at 40 t ha^?1. Both compost and farmyard manure improved plant growth and nutrient uptake. However, compost amendment showed more effectiveness, especially at 80 t ha^?1. Alternatively, this dose of compost involved an increase of plant copper, cadmium, and zinc concentrations in plant tissues. Metal accumulation did not thwart the enhancement of wheat yield. Furthermore, grain translocation factor reached 1 only in the case of copper; however, it showed a significant decrease following compost application (ranged between 0.57 and 0.69). Bioconcentration factor showed a significant decrease with municipal solid waste compost supply, constituting an internal detoxification mechanism.     

Influence of organic amendments on dissipation kinetics of two different pesticides in soil: a case study

A study was undertaken to investigate the remedial effect of some soil amendments (farmyard manure (FYM), press mud compost (PMC), cereal straw (CS) at 5 t ha^?1 and fresh cow dung slurry (FCD) @ 0.5 t ha^?1) on dissipation kinetics of imidacloprid and sulfosulfuron under laboratory conditions. Incorporation of CS or FCD was found to be most effective in degrading both the pesticides at faster rates. Dissipation of both the pesticides could be well accounted by two component (1 + 1) first order kinetics. The computed values of parameters revealed that use of organic amendments increased the dissipated fraction of imidacloprid and sulfosulfuron. Incorporation of CS or FCD in soil maintained relatively higher dissipation rate constants for both faster and slower dissipation processes of pesticides in comparison to control. Hence, eco-friendly practices of CS or FCD incorporation as soil amendment in soil can play a vital role in preventing soil and water pollution.     

The effect of winery solid waste compost application on maize growth,biomass yield,and nutrient content under greenhouse conditions

A greenhouse study was conducted to assess the fertilizer value and determine the optimum application rate of five winery solid waste (WSW) composts containing varied filter material (FM) mixed proportions with grape marc and pruning canes using maize. The composts comprised of 4, 10, 20, 30, and 40% FM (w/w) designated C4FM, C10FM, C20FM, C30FM, and C40FM, respectively. Application rates of 5, 10, 20, 40, and 80 t ha^?1 were used; while unamended control and inorganic NPK fertilizer treatments were included as references. The results showed that application of composts with 20% FM or more at 80 t ha^?1 significantly increased the dry matter yield more than NPK fertilizer but full potential was not reached due to inadequate nitrogen supply. Maize shoot K content from compost treatments exceeded the critical nutrient level while the shoot Zn content from compost treatments with 20% FM or less also exceeded the critical level. The results revealed that these composts could serve as potential good sources of K and Zn for maize production, particularly, in sandy soils where these nutrients are often reported to be deficient. Quantitative estimate of the optimum rate of the composts for dry matter production ranged from 75 to 307 t ha^?1.     

Mudflat soil amendment by sewage sludge: Soil physicochemical properties,perennial ryegrass growth,and metal uptake

Abstract

The fast pace of cropland loss in China is causing alarm over food security and China’s ability to remain self-reliant in crop production. Mudflats after organic amendment can be an important alternative cropland in China. Land application of sewage sludge has become a popular organic amendment to croplands in many countries. Nevertheless, the land application of sludge to mudflats has received little attention. Therefore, the objective of the present work was to investigate the impact of sewage sludge amendment (SSA) at 0, 30, 75, 150 and 300 t ha^?1 rates on soil physicochemical properties, perennial ryegrass (Lolium perenne L.) growth and heavy metal accumulation in mudflat soil. The results showed that the application of sewage sludge increased organic matter (OM) content by 3.5-fold while reducing salinity by 76.3% at the 300 t ha^?1 rate as compared to unamended soil. The SSA reduced pH, electric conductivity (EC) and bulk density in mudflat soil, increased porosity, cation exchange capacity (CEC) and contents of nitrogen (N), phosphorus (P), exchangeable potassium ions (K⁺), sodium ions (Na⁺), calcium ions (Ca²⁺) and magnesium ions (Mg²⁺) in comparison to unamended soil. There were 98.0, 146.6, 291.4 and 429.2% increases in fresh weight and 92.5, 132.4, 258.6 and 418.9% increases in dry weight of perennial ryegrass at 30, 75, 150, and 300 t ha^?1, respectively, relative to unamended soil. The SSA increased metal concentrations of aboveground and root parts of perennial ryegrass (p < 0.05). The metal concentrations in perennial ryegrass were Zn > Cr > Mn > Cu > Cd > Ni, and the metal concentrations in roots were significantly higher than aboveground parts. The metal accumulation in perennial ryegrass correlated positively with sludge application rates and available metal concentrations in mudflat soil. Land application of sewage sludge was proved to be an effective soil amendment that improved soil fertility and promoted perennial ryegrass growth in mudflat soil. However, heavy metal accumulation in plants may cause food safety concern.     

Growth and nutrition of Holcus lanatus in bauxite residue amended with combinations of spent mushroom compost and gypsum

Bauxite residues are very slow to naturally vegetate due to nutrient deficiency and high sodicity. In order to test the effectiveness of amendments at promoting revegetation, bauxite residue was amended with varying rates of compost to increase fertility (0, 60, 80 and 120 t ha⁻¹) and gypsum to reduce sodicity (0, 40 and 90 t ha⁻¹). Amended residue was sown with Holcus lanatus, a perennial grass. Following a 1‐year growth period, substrate properties, plant performance and plant nutrient uptake were assessed. Compost application substantially increased substrate N, P, K and Mn concentrations, while gypsum application greatly reduced sodicity and improved nutrient uptake for Mn and P. Compost amendment was essential for sustainable plant growth. Foliar deficiencies in N, P and Mg may persist with lower compost application rates, requiring the addition of supplemental fertiliser for healthy plant growth. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects of cotton (Gossypium hirsutum L.) straw and its biochar application on NH3 volatilization and N use efficiency in a drip-irrigated cotton field

Reducing ammonia (NH₃) volatilization is a practical way to increase nitrogen (N) fertilizer use efficiency (NUE). In this field study, soil was amended once with either cotton (Gossypium hirsutum L.) straw (6 t ha^?1) or its biochar (3.7 t ha^?1) unfertilized (0 kg N ha^?1) or fertilized (450 kg N ha^?1), and then soil inorganic N concentration and distribution, NH₃ volatilization, cotton yield and NUE were measured during the next two growing seasons. In unfertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 38–40% and 42–46%, respectively, less than that in control (i.e., unamended soil) during the two growing seasons. In the fertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 30–39% and 43–54%, respectively, less than that in the control. Straw amendment increased inorganic N concentrations, cotton yield, cotton N uptake and NUE during the first cropping season after application, but not during the second. In contrast, biochar increased cotton N uptake and NUE during both the first and the second cropping seasons after application. Furthermore, the effects of biochar on cotton N uptake and NUE were greater in the second year than in the first year. These results indicate that cotton straw and cotton straw biochar can both reduce NH₃ volatilization and also increase cotton yield, N uptake and NUE. In addition, the positive effects of one application of cotton straw biochar were more long-lasting than those of cotton straw.     

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.     

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.     

The accumulation of phytolith-occluded carbon in soils of different grasslands

Purpose

A better understanding of the role of grassland systems in producing and storing phytolith-occluded carbon (PhytOC) will provide crucial information in addressing global climate change caused by a rapid increase in the atmospheric CO₂ concentration.

Materials and methods

Soil samples of typical steppe, meadow steppe, and meadow in Inner Mongolia, China, were taken at 0–10-, 10–20-, 20–40-, and 40–60-cm depths in July and August of 2015. The soil phytoliths were isolated by heavy liquid (ZnBr₂), and the soil PhytOC was determined by the traditional potassium dichromate method.

Results and discussion

The results of our study showed that the storage of soil phytoliths was significantly higher in the meadow (33.44 ± 0.91 t ha^?1) cf. meadow steppe (26.8 ± 0.98 t ha^?1) and typical steppe (21.19 ± 4.91 t ha^?1), which were not different. The soil PhytOC storage was significantly different among grassland types, being: meadow (0.39 ± 0.01 t ha^?1) > meadow steppe (0.29 ± 0.02 t ha^?1) > typical steppe (0.23 ± 0.02 t ha^?1). PhytOC storage in typical steppe soil within the 0–60-cm soil layer is the lowest and that in meadow soils is the highest. The grassland type and the soil condition play significant roles in accumulation of phytoliths and PhytOC in different grassland soils. We suggest that the aboveground net primary productivity (ANPP) is important in soil phytolith accumulation and PhytOC content.

Conclusions

Phytolith and PhytOC storages in grassland soil are influenced by factors such as grass type, local climate and soil conditions, and management practices. Management practices to increase grass biomass production can significantly enhance phytolith C sequestration.

     

Biogas digestates based on lignin-rich feedstock – potential as fertilizer and soil amendment

With advances in biogas technology, lignocellulosic material may be increasingly included in feedstock due to the abundance of raw materials. The main goal of this study was to evaluate fertilizing and soil amendment effects of digestates based on lignin-rich feedstock. The digestates originated from reactors fed with manure co-digested with Salix, wheat straw or sugarcane bagasse, respectively. In pot experiments with three different soils, Italian ryegrass and reed canary grass were grown with 120 kg ha^?1 total nitrogen or 150 kg ha^?1 available nitrogen, respectively, given as either mineral fertilizer or digestate. Soil chemical and physical characteristics were determined after ended experiments. Additionally, an incubation study was carried out to estimate N mineralization from one digestate over time. Digestate addition resulted in similar yields compared to mineral fertilizer, varying from 0.5 (loam) to 1 kg dry matter m^?2 (silt) for Italian ryegrass and 1.2 (loam) to 2.3 kg m^?2 (silt) for reed canary grass. Digestates contributed to a favourable pH for plant growth, reduced bulk density in the loam and improved water retention characteristics in the sand. Biogas digestates based on lignin-rich feedstock appear promising as fertilizers and for soil amelioration but results have to be verified in field experiments.     

SEASONAL CHANGES IN NUTRIENT AVAILABILITY FOR SULFUR-AMENDED EVERGLADES SOILS UNDER SUGARCANE

The objective of this study was to evaluate effects of elemental sulfur (S) addition on soil pH and availability of macro- and micronutrients during the sugarcane growing season. Sulfur application did not significantly reduce soil pH when applied at 0 to 448 kg S ha^?1 due to the high soil buffering capacity. Water extractable phosphorus (P) and potassium (K) for soils receiving the highest S rate were 188% and 71% higher than for unamended soils only at two months after application, indicating a short-term enhancement of macronutrient availability. Soil amended with 448 kg S ha^?1 contained 134% more acetic acid-extractable zinc (Zn) than unamended soil, although stimulatory effects did not extend beyond two months. Sugar yield was not affected by S addition, averaging 17 Mg sugar ha^?1. The failure of S to enhance nutrient availability throughout the growing season indicates the limited benefit of applying elemental S to reduce pH and increase nutrient availability to sugarcane.