Adsorption Properties of Adsorption Tower Filled with Calcium Superphosphate on NH_3 Emitted from Composting System of Animal Wastes

[Objective] This study aimed to investigate the adsorption properties of the adsorption tower filled with calcium superphosphate on ammonia volatilized with aer- ation. [Method] Adsorption tower filled with calcium superphosphate was adopted as experimental apparatus, which was constructed by poly vinyl chloride （PVC） circular tubes. With hartshorn as the source of ammonia volatilization, the effect of different ratios of height to diameter of the tower filled with equal amount of calcium super-phosphate on ammonia adsorption was investigated. In addition, adsorption tower with height-diameter ratio of 9.9 was selected to adsorb the ammonia emitted from the composting systems of pig manure and chicken manure with optimized and reg- ulated carbon-nitrogen ratio. [Result] Under certain volatilization rate, calcium super- phosphate particles in the adsorption tower could effectively adsorb the ammonia, and the adsorption efficiency was enhanced with the increase of height-diameter ra-tio, which could reach above 90% with height-diameter ratio of more than 1.1; the ammonia emitted from composting systems of pig manure and chicken manure with optimized and regulated carbon-nitrogen ratio could be completely absorbed using adsorption tower with height-diameter ratio of 9.9 filled with calcium superphosphate accounting for about 8% of the weight of composting materials. [Conclusion] Experi- mental results of this study provided reference for the application of adsorption tower filled with calcium superphosphate in the treatment of waste gas emitted from com- posting materials.

Effects of Superphosphate Addition on NH_3 and Greenhouse Gas Emissions During Vegetable Waste Composting

To study the effects of superphosphate（SP） on the NH_3 and greenhouse gas emissions,vegetable waste composting was performed for 27 days using 6 different treatments. In addition to the controls,five vegetable waste mixtures（0.77m^3 each） were treated with different amounts of the SP additive, namely, 5%, 10%,15%, 20% and 25%. The ammonia volatilization loss and greenhouse gas emissions were measured during composting.Results indicated that the SP additive significantly decreased the ammonia volatilization and greenhouse gas emissions during vegetable waste composting. The additive reduced the total NH_3 emission by 4.0% to 16.7%. The total greenhouse gas emissions（CO_2-eq） of all treatments with SP additives were decreased by 10.2% to 20.8%, as compared with the controls. The NH_3 emission during vegetable waste composting had the highest contribution to the greenhouse effect caused by the four different gases.The amount of NH_3（CO_2-eq）from each treatment ranged from 59.90 to 81.58 kg/t; NH_3（CO_2-eq） accounted for 69% to 77% of the total emissions from the four gases. Therefore, SP is a cost-effective phosphorus-based fertilizer that can be used as an additive during vegetable waste composting to reduce the NH_3 and greenhouse gas emissions as well as to improve the value of compost as a fertilizer.

Does the long-term application of calcium superphosphate lead to an increase of the soil rare earth element contents？

In order to test whether the long-term application of calcium superphosphate leads to an increase of the soil rare earth element contents, superphosphate fertilized soils were sampled and compared with superphosphate-free soils. Spectrophlame inductively coupled argon plasma atomic emission spectrophotometer （ICP-AES） was applied to quantify the rare earth elements （REEs）. The total rare earth element contents in calcium superphosphate from Zhijin County, west part of Guizhou Province, China （produced by the sulphuric acid treatment of the apatites） are about 2.54 mg/g. Between 38 and 189 gREEs/hm^2 per year （available for plants, estimated by 2% citric acid） will be introduced into the soil solution when applying 320 kg superphosphate/hm^2 per year. The long-term application of the latter will increase the REE content by about 18% in the soil surface layer in these areas. A statistically significant increase of the content of the rare earths in some cultivated soils should not be neglected.

Mercury in some chemical fertilizers and the effect of calcium superphosphate on mercury uptake by corn seedlings (Zea mays L.)

Mercury （Hg） contents in ten chemical fertilizers were determined, and the effect of calcium superphosphate （CSP） on the uptake and translocation of Hg in corn seedlings was investigated by pot experiments. CSP was applied at the levels of 0, 66.7, and 133.4 mg P2O5/kg to Hg-treated （2 mg/kg） and untreated soils. CSP had the highest Hg content （5.1 mg/kg）, followed by the NPK compound fertilizer 15-5-5 （15% N, 5% P2O5, 5% K2O） （1.2 mg/kg）, then by nitrogen fertilizers （except for ammonia sulfate） and potassium fertilizers. Application of CSP did not obviously iuence the biomass of corn roots, but it significantly increased the biomass of corn shoots in Hg-treated soil. Application of CSP at the levels of 66.7 and 133.4 mg P2O5/kg did not obviously iuence the uptake of Hg by corn seedlings on soils without Hg treatment, but it decreased the Hg uptake of corn seedlings significantly on Hg-treated soils. The transfer coefficient of Hg in corn seedlings improved slightly on soils without Hg treatment, but decreased slightly on Hg-treated soils with the application of CSP. These results implied that CSP could ameliorate Hg toxicity to corn seedlings by inhibiting the uptake and the translocation of Hg in plants on Hg-polluted soils.

Effects of Urea Ammonium Chloride of Different Fertilization Patterns on Maize Yield and Yield Components

[Objective] To understand the application effects of urea ammonium chloride fertilizer on maize production. [Methods] A field plot experiment was conducted to study the effects of urea ammonium chloride of different fertilization patterns on summer maize yield and yield components. [Results] Urea ammonium chloride had a long fertilizer effect and the same yield-increasing effect with urea, which could im- prove the agronomic traits and economic traits of maize apparently and the applica- tion of urea ammonium chloride with nutrient reduction of 40% （namely just use urea ammonium chloride equaled 60% pure nitrogen）, had the same yield-increasing effect with urea of traditional fertilization patterns, and input-output ratio was high and the economic benefit was remarkable. [Conclusion] To provide scientific theoretical direc- tion for large area popularization and application of urea ammonium chloride.

Effects and Mechanisms of P and K Nutrients on Yield and Protein Content of Fodder Rice

Effects and mechanisms of P and K nutrients on yield and protein content of Weiyou 56, a fodder hybrid rice combination,were studied through pot experiment and biochemical analysis. The results showed that the increase of P and K nutrients enhanced the activities of PEP carboxylase (PEPC), glutamine synthase (GS) and sucrose phosphate synthase (SPS) in leaves, sucrose synthase (SS), ADP glucose pyrophosphorylase (ADPGP) and GS in grains, and the chlorophyll content in leaves, soluble sugar and starch content in grains, protein N and total N content in leaves and grains. Howerer, they decreased soluble sugar content in leaves and led to an increase of protein content in brown rice, biomass, grain yield and harvest index. Excessive P nutrients slightly reduced SPS and ADPG activity in leaves and grains respectively.

Residual Effects of Phosphate Amendments on Rainfed Rice (Oryza sativa L.) Nutrition and Soil Properties in Three Agroecological Zones of Côte d’Ivoire

A study was conducted in Côte d’Ivoire to assess the after-effect of phosphate amendments on rice yields and soil properties. Eight types of amendments, composed of Moroccan phosphate rock (PRM) and triple superphosphate were tested in three agroecological zones over three consecutive years of cultivation. This study revealed that the application of Moroccan phosphate rock (PRM) and/or triple superphosphate (TSP) did not significantly affect soil cation exchange capacity (CEC) and organic carbon (Corg) content. However, there was a negative residual effect of PRM-rich treatments on soil pH and K and N content, but the impact varies depending on the characteristics of the soils studied. Furthermore, nutrient losses, notably nitrogen from −17.5 to −267.7 kg/ha and potassium (−0.1 to 0.7 kg/ha), were observed in all treatments. Only phosphorus showed a positive balance of +49.56 to +52 kg/ha in PRM-rich treatments. Treatment T3, composed of 80% RPM and 20% TSP, was the most effective in all zones, with a relative increase in grain yields of over 100% compared to the control. These results suggest that the input of natural phosphate rock can significantly improve rice yields and soil properties in the studied agroecological zones in Côte d’Ivoire.

Influence of Sludge Incineration Ash on Ryegrass Growth and Soil Phosphorus Status

Phosphorus(P) is a limited resource that could be depleted. Consequently, recycling the P contained in sewage sludge, including sewage sludge incineration ash(SIA), from wastewater treatment plants is a possibility to be explored. A greenhouse experiment using annual ryegrass(Lolium multiflorum L.) was performed with an experimental design of three completely randomized blocks of two soils and 29 treatments: one control without P and two levels of 9 and 26 kg total P ha^(-1) from 14 different sources: twelve SIAs(not contaminated by trace metals) from the US and Canada, one commercial synthetic fertilizer(triple superphosphate(TSP)), and one commercial rock phosphate(RP). Higher ryegrass biomass levels were achieved at the higher fertilization rate(26 kg total P ha^(-1))and when using the SIAs with the highest P solubility percentage(PSP)(≥ 54% of total P). The biomass increases following SIA application were as high as 29% and 59% more than the control for the sandy loam and clayey soil, respectively, but 40% less than in TSP for both soils. A similar behavior was observed for P uptake, with a maximum increase of 26% for the clayey soil, and 165% for the sandy loam soil. The ryegrass biomass and P uptake increases due to SIA application were larger than those due to RP application in the clayey soil, but similar to those in the sandy loam soil. The SIAs with a PSP of ≥ 54% significantly increased soil available P stocks and saturation. According to our findings, we conclude that the SIAs from municipal and agrifood industries have a potential for P agricultural recycling, but their efficiencies vary.

Application of phosphate-containing materials affects bioavailability of rare earth elements and bacterial community in soils

The exploitation and smelting of rare earths can cause serious pollution to the farmland around the mining area. The rare earth elements(REEs) are absorbed by crops and enter the human body through the food chain, which threatens people’s health. The effects of four phosphorus-containing materials-calcium superphosphate(SSP), phosphate rock(PR), calcium magnesium phosphate(CMP) and bone charcoal(BC) on rice growth and bacterial community structure in REE mining area of Xinfeng County were studied by pot experiment. The soil solution was collected during rice transplanting and harvest periods respectively, the rice and soil samples were collected and sequenced. The concentrations of water-soluble REEs were measured by inductively coupled plasma mass spectrometry(ICP-MS), and bacteria in soil was deeply sequenced by the Illumina Miseq sequencing platform. PR, CMP and BC promoted the growth of rice, improved the biomass of rice roots, shoots and grains, and significantly reduced absorption and accumulation of REEs in rice roots, shoots and grains. SSP treatment reduced the pH value of soil, significantly improved the concentration of REE solution in soil and improved biomass of rice roots, shoots and grains,and significantly improved the concentration of REEs in grain. The effects of phosphorus-containing materials on the absorption and accumulation of 15 REEs in rice roots, shoots and grains were very different, and significantly influenced the soil bacterial community. SSP reduced richness and diversity of bacteria. CMP improved the diversity of soil bacteria, but reduced their richness. PR and BC treatment improved the richness and diversity of soil bacteria, and significantly increased the abundance of Bacillus. The results showed that adding PR, CMP and BC to soil in the REE mining area of Xinfeng can improve food security and eco-environmental quality, and hence, are potential restorative materials;SSP is not recommended for use in acidic soils.

Kinetics of Soil Potassium Release Under Long-Term Imbalanced Fertilization in Calcareous Soils

Knowledge on potassium ion(K^+) release from soils makes K fertilizer recommendation more efficient and profitable.Kinetics of K^+release under continuous fertilization of no fertilizer(CK), urea(N), triple superphosphate(P), and urea + triple superphosphate(NP) without K fertilizer was investigated in calcareous(chloritic and kaolinitic) soils on the Miandarband Plain in Kermanshah Province of Iran.The results showed that the kinetics of K^+release included an initial reaction and a slow reaction.The phosphateand NH_4^+-induced K^+release followed the same rate process during the rapid(2–192 h) and slow release periods(192–1 090 h).There were no significant differences in the cumulative K^+released from the chloritic and kaolinitic soils among all the treatments.The cumulative K^+released was positively correlated with P adsorption capacity for the chloritic(r = 0.461, P < 0.05) and kaolinitic soils(r = 0.625, P < 0.01), and negatively correlated with K fixation potential for the chloritic(r = 0.720, P < 0.01) and kaolinitic soils(r =-0.513, P < 0.01).There was a significant(P < 0.001) interactive effect of K fixation potential × P adsorption capacity on the cumulative K^+released for both soil groups.The initial release rate(IRR) index(a·b, where a and b are the rate coefficients of the power function equation) for the chloritic soils was significantly(P < 0.05) higher under applications of P and NP than N and CK.The IRR index values among different fertilization treatments were in the order of NP = P > N = CK for the chloritic soils, and N =P > NP > CK for the kaolinitic soils.This study showed that K fixation potential and P adsorption capacities controlled K^+release from soils.This information will be helpful for precise fertilizer recommendations for the studied soils.