Nutrient Release Rates Research Articles

New Straw Coating Material for Improving the Slow-Release Performance of Fertilizers.

In this work, we extracted cellulose from agricultural waste and produced a new straw coating material (ethyl cellulose, EC) through a series of modification operations. The slow-release properties of ethyl cellulose-coated urea (EU) and its absorption and utilization by plants were evaluated. The surface of EU can form a smooth and fine film, and the initial nutrient release rate is only 37.91% that of the uncoated fertilizer. Compared with common urea, the nitrogen of plants cultivated with EU increased by 17.69%, and the leached nitrogen decreased by 61.29%, indicating that EU can reduce nitrogen waste to the greatest extent and continuously supply nutrients to crops. Therefore, the application of EU could be a more practical, environmentally friendly, and sustainable alternative to nitrogen fertilizers.

Straw Return Decomposition Characteristics and Effects on Soil Nutrients and Maize Yield

Straw return benefits soil nutrient circulation and avoids the environmental pollution caused by incineration. The straw return effect is determined by many factors, such as the returning mode and tillage method. To find the most suitable straw return mode in the hilly areas of south China, we conducted experiments with preceding maize straw in Nanchong (Sichuan Province, China) for three years. Five treatments were tested: (A) rotary tillage without straw return (RT), (B) crushed straw return with rotary tillage (CRT), (C) crushed straw return without rotary tillage (CSR), (D) whole straw return with rotary tillage (WRT), and (E) whole straw return without rotary tillage (WSR). The results indicated that CRT had the fastest decomposition rate, followed by CSR. Moreover, CRT had the fastest nutrient release rates for nitrogen, phosphorus, potassium, cellulose, hemicellulose, and lignin, as well as the highest maize yield (6.62% higher than RT). CRT increased the content of organic matter, total nitrogen, total phosphorus, and total potassium in the soil, as well as improved the soil pH. Furthermore, the numbers of bacteria, Actinomycetes, and fungi in the soil under CRT, CSR, and WSR treatments were higher than those under the other two treatments. This study has important reference value for exploring the most favourable straw return method for improving farmland fertility.

Ecological Stoichiometric Characteristics of Plant–Soil–Microorganism of Grassland Ecosystems under Different Restoration Modes in the Karst Desertification Area

C, N and P are the key biogenic elements of terrestrial ecosystems, and their biogeochemical processes regulate nutrient cycling and play a key role in restoring degraded ecosystems. In this paper, the grassland ecosystem under artificial restoration measures (Dactylis glomerata (DG), Lolium perenne (LP), Lolium perenne + Trifolium repens (LT)), and the natural restoration measures (NG) in a typical karst plateau desertification control area of southwest China, were taken as the research object. The C, N, and P concentrations and the ecological stoichiometry of the plant–soil–microorganism system in grasslands under different restoration measures in the karst desertification area were explored. We established the following findings: (1) Compared with NG, the C, N and P concentrations of plants and soil in DG, LP and LT were higher, and LT was the highest. (2) The microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) concentrations in LT was also the highest. (3) The C:N ratio of plant and soil indicated that the N mineralization and nutrient release rate of DG, LP and LT were stronger than that of NG, and the plant growth of NG was most seriously limited by nitrogen. The N:P ratio in plant and soil indicated that the grassland was limited by P in the four treatments. (4) The result of correlation analysis showed that the cycling process of C, N and P in the plant–soil–microorganism system was coupled, and that the elements closely affected each other. In general, the effect of artificial restoration on a degraded ecosystem was relatively better than the natural restoration for increasing plant, soil and microbial nutrient concentrations, especially in the mixed-seed ecosystem of leguminous and gramineous forage. However, in the future, grassland management, appropriate N fertilizer or N-fixing plants and P fertilizer should be considered to improve the limitation of plant N and P, so as to realize the sustainable development of grasslands and the restoration of degraded ecosystems in the karst desertification control area.

Struvite Got by a Modified Technology as the Basis of an Environmentally Friendly Controlled-release MgNP-fertilizer

The results of a quantitative analysis of nutrients based on samples of struvite as a controlled release nitrogen-phosphorus fertilizer, obtained using two technology options, were presented. It was shown that the use of traditional struvite deposition technology leads to the formation of a coarse-grained product (average crystal size 578 μm). It was confirmed that the modified technology allows to obtain highly dispersed struvite (average crystal size 19 μm) with a more extended particle surface and an ammonium content of 98–99% of the theoretical value with a higher nutrient release rates compared to struvite got by conventional technology. Struvite synthesized by the modified technology was found to show improved performance as a controlled release MgNP fertilizer.

Green construction and release mechanism of lignin-based double-layer coated urea

BackgroundLignin played an important role in the establishment of coated fertilizers coating material as a substitute for petrochemical raw materials. However, so far, the lignin-based coated fertilizers was limited in only the poor slow-release performance. To achieve good slow-release performance of lignin-based coated fertilizers, hydrophilic of lignin need to be resolved to establish an green and better controllable lignin-based coated fertilizers.ResultsIn the study, a novel green double layer coating with lignin-based polyurethane (LPU) as the inner coating and epoxy resin (EP) as the outer coating was effectively constructed for coated urea. Fourier transform infrared spectra confirmed that lignin and polycaprolactone diol successfully reacted with Hexamethylene diisocyanate. The loss weight and water contact angle (WCA, 75.6–63.6°) of the LPUs decreased with the increased lignin content. The average particle hardness of the lignin-based double-layer coated urea (LDCU) first increased from 58.1 N (lignin of 30%) to 67.0 N (lignin of 60%), but then decreased to 62.3 N (lignin of 70%). The release longevity of the coated urea was closely related to the preparation parameters of the coating material. The optimal cumulative nutrient release rate (79.4%) of LDCU was obtained (lignin of 50%, –CNO/–OH molar ratios of 1.15, EP of 35%, and coating ratio of 5%). The aggregates of hydrone on the LDCU caused the dissolution and swelling of nutrients, and then the diffusion of nutrients through the concentration gradient.ConclusionsA though the nutrient release of the LDCUs was affected by many factors, the successful development of the LDCUs will help improve the rapid development of the coated fertilizer industry.

Ammoniacal and Nitrate Nitrogen Release Pattern from Biochar and Biochar Blended Urea Fertilizers in Sandy Soil

Biochar, an organic product of thermal decomposition of biomass in an oxygen limited environment can be used as a nutrient carrier to delay the release of nutrients into the soil, reduce nutrient leaching, and improve the nutrient utilization efficiency of fertilizers. Nutritional enhancement of biochar through fertilizer blending could be a low cost but high efficiency solution compared to non-blended fertilizers. However, the rate of nutrient release from the blended biochar fertilizer in different soils is ambiguous. Hence a 12 month incubation study was conducted in sandy soil (ultisol) of Thiruvananthapuram district of Kerala to elucidate the ammoniacal and nitrate nitrogen release rate and pattern from the produced paddy husk biochar, biochar and biochar bentonite (1:1) each blended with urea fertilizer in different ratios (1:0.5, 1:1, 1:2) including an absolute control. The individual effects of biochar, biochar-bentonite and urea were also studied. Paddy husk biochar was produced by the process of slow pyrolysis and biochar- blended urea fertilizers by the adsorbent process. To evaluate the influence of bentonite clay on the nutrient release pattern of biochar, it was blended with biochar and urea fertilizer. The highest total nitrogen content among the produced fertilizers was recorded in biochar: urea in 1:2 (33.04%) followed by biochar-bentonite: urea in a 1:2 ratio (31.13%). The incubation study revealed that the maximum release of ammoniacal nitrogen from soil+ urea fertilizer was at 30 days (115.73 mg kg-1) followed by a sharp decline, maintaining a low value till the end of incubation, whereas the release was sustained and gradually increased to reach a maximum at the 180th day (117.6 mg kg-1) for soil+ biochar: urea in 1:1 ratio. Nitrate nitrogen also followed the same trend with the maximum release observed for biochar: urea in 1:1 on the 150th day (151.2 mg kg-1). The release of nitrate nitrogen was more than that of ammoniacal nitrogen throughout the incubation period for all the treatments. Among the blended fertilizers, content of both ammoniacal and nitrate nitrogen were comparatively less for biochar –bentonite blended urea fertilizers. Thus, blending of urea with biochar/ biochar-bentonite prolonged the duration of maximum nutrient release.

Estimation of Changes in the Nutrient Release Rate from Sediments after a Tsunami by an Incubation Experiment

A tsunami induced by the Nankai Trough earthquake may disturb marine sediments in the inner part of Osaka Bay. Since nutrient release from marine sediments has a significant impact on nu-trient concentrations in seawater, an incubation experiment was conducted to estimate the release rates of NH4-N and PO4-P in order to understand the present rates and to quantify the changes in the rates caused by tsunamis in Osaka Bay. The current release rate of NH4-N is an extension of the decreasing trend since 2000. The PO4-P release rate has remained at a low level since 2008. The release rate of redeposited sediments after exposure to the aerobic environment caused by a tsunami may decrease to approximately 70% of the current level for NH4-N and 60% for PO4-P. Nutrient concentrations and fishing have begun to decline in Osaka Bay. A reduction in the nutrient release rate by tsunamis may further limit primary production under the current situation where the contribution of release to nutrients in seawater is significant.

Quantification of Nutrient Fluxes from Sediments of Lake Hulun, China: Implications for Plateau Lake Management

Dramatic changes in lake water conditions may induce sensitive feedback in sediments, such as the release of phosphate and ammonia. There is a lack of the understanding of sediment nutrient release fluxes and their responses to various environmental factors in plateau lakes. In this study, nutrient contents in the water and sediment, sediment nutrient release rates, and their responses to various influential factors in a steppe shallow plateau lake, Lake Hulun, China, were investigated. Sediment is a large store of nutrients, with bioavailable phosphorus of 555 mg kg−1 in surface lake sediments. If water became anoxic, sediments will release appreciable amounts of phosphate (2.1 mg P m−2 d−1) and ammonia (40.0 mg N m−2 d−1), three times greater than those in oxic conditions. Raised temperatures greatly increased sediment phosphate release rates, while the highest temperature (23 °C) slightly decreased ammonia release rates due to strong nitrification. Assuming a whole year of internal loading, ammonia and dissolved reactive phosphorus concentrations in water column would increase by an estimated 0.22 mg N L−1 and 0.01 mg P L−1, respectively, which is equal to 2 and 0.5 times of their ambient concentrations. A pH increase from 8.4 to 9.4 significantly decreased internal nitrogen and phosphorus release rates by around three times. Overall, dissolved oxygen (DO) and pH had a greater impact on sediment nutrient release from lake sediments compared to temperature, and further increased the eutrophic status in the overlying water when these three parameters varied within the normal seasonal range (temperature: 1.9–23.1 °C, DO: oxic and anoxic; pH: 7.5–9.4). With the periodic low DO and frequency of drought in the future, lake management strategies that mitigate water eutrophication, such as water diversion, may need to be considered.

Microbial mechanism of crop residues addition in nitrogen leaching loss retention and soil ecosystem stability maintenance

Over fertilization is the main factor in excessive N leaching (NL) loss in greenhouse vegetable cultivation systems. Adjusting the fertilizer application rate and returning plant residues effectively reduce NL. However, the microbial mechanism of crop residues addition in NL loss retention remains largely unknown. This study established a tomato-cultivating soil column experiment with different organic fertilizer addition treatments: no organic amendment (CK), chicken manure application (CM), chicken manure ＋rice husk (CMR), and chicken manure ＋maize straw (CMM) to further explore the discrepancies in the microbial community composition and the microbial co-occurrence network structure. The results revealed that CM produced the highest yield when provided with just enough nutrients for the crop requirements. The CMR yield decreased by 26.0%, while CMM remained at the same level as CK. Although discrepancies were evident between the decomposition characteristics and nutrient release rates of the rice husk and maize straw, no differences were apparent between the mineral NL loss retention of the two materials after one growing season, exhibiting a 47.8% and 50.4% reduction compared to CM. Furthermore, crop residues addition induced rapid microbial growth, increased the microbial community richness, and caused lignocellulose degraders accumulation, with fewer operational taxonomic units (OTUs) associated with the nitrification process. The CMM treatment produced a more robust and complex microbial co-occurrence network that was absent in the CM treatment. The results implied an alleviating effect of the straw amendment on mineral NL loss and emphasized the importance of readily available C sources in stabilizing an ecosystem.

Hydrophobic coatings for granular fertilizers to improve physical handling and nutrient delivery

Globally, fertilizer agglomeration (caking) during transport and storage leads to irreversible breakdown, dust, equipment blockages and inconsistent field application. Coatings which are hydrophobic reduce moisture uptake at high humidity and reduce caking but still need to release plant nutrients. Here, natural and synthetic waxes coated onto fertilizer granules with powders to impart surface roughness reduced contact between condensed water droplets and the surface, lowering moisture ingress. The adhesive strength of the coatings and rate of nutrient release are shown with degree of roughness quantified using laser surface microscopy. The wax-only coatings on potassium chloride fertilizer (MOP, 50% K) reduced moisture uptake by up to 30%, while for coatings with wax and roughener reductions were between 56% and 80%. Beeswax with micronutrient rougheners reduced moisture uptake by over 65% whilst maintaining uninterrupted nutrient supply. Thus, these hydrophobic coatings can improve physical characteristics of fertilizer without compromising the kinetics of nutrient release.

New Urea Controlled-Release Fertilizers Based on Bentonite and Carnauba Wax

Controlled-release fertilizers are interesting alternatives to current commercial chemical fertilizers, which present a higher nutrient release rate, and can negatively impact the ecosystem. In this work, two urea controlled-release fertilizer types were manufactured from carnauba wax (CW), commercial granulated urea (U), and natural and sodium bentonite (Bent-R and Bent-Na, respectively). In the first type, the mechanochemical method produced fertilizers in bars, from a mixture containing different proportions of U, Bent-R, and Bent-Na. In the second type, the dip-coating method was used to coat urea bars with coatings containing different proportions of the Bent-R, Bent-Na, and CW. The cumulative urea release was evaluated over the 30-day incubation period, through soil columns tests and UV/visible spectroscopy. Overall, both fertilizers developed in this work presented lower cumulative urea release than standard fertilizers. On the other hand, the new fertilizers produced from the dip-coating method, provided cumulative urea release lower than that obtained by the mechanochemical method. In summary, carnauba wax and bentonite (raw and sodium modified) are promising materials for developing new urea controlled-release fertilizers. Furthermore, both carnauba wax and bentonite are non-toxic, biodegradable, relatively inexpensive, and created from materials that are easily purchased in Brazil, indicating that the new fertilizers developed in this work have the potential to be produced on a large scale.

Effect of nano nitrogen, nano zinc and nano copper on certain growth and yield characters of ridge gourd (Luffa acutangula L.) cv. COH 1

The nutrient release rate in nano fertilizers can be controlled as per environmental conditions like soil moisture percentage, temperature fluctuations and soil acidity level to effectively increase the efficiency of nutrients for plant growth. An experiment was conducted during the year 2021 to find out the best combination in nano nitrogen, nano Zn and nano Cu on certain growth and yield characters of ridge gourd (Luffa acutangula L.) cv. COH 1 at Chidambaram,Tamil Nadu, India. The data collected for the growth and yield parameters were put through to analysis of variance for randomized block design (RBD). The treatments were scheduled as follows: T1–100% RDF, T2- 50% RD-N+100% RD-P+100% RD-K+nano N, T3–25% RD-N+100% RD-P+100% RD-K+nano N,T4–T2+nano Zn (a)+nano Cu (a), T5–T2+nano Zn (b)+nano Cu (a), T6–T2+nano Zn (a)+nano Cu (b), T7–T2+nano Zn (b)+nano Cu (b), T8–T3+nano Zn (a)+nano Cu (a), T9–T3+nano Zn (a)+nano Cu (a), T10–T3+ nano Zn (a)+nano Cu (b) and T11–T3+nano Zn (b)+nano Cu (b). The results generated from the experiment were statistically significant (P≥0.05) for all the growth and yield characters recorded. The combination of 50% RDF with nano nitrogen @ 2.5 ml, nano zinc @ 4 ml and nano copper @ 4 ml was observed to be significantly superior over other treatments. It recorded profuse growth and yield in respect of maximum vine length (9.69 m), number of primary branches (7.87/vine), number of leaves (251.65/vine), number of fruits (26.60/plant), fruit length (52.36 cm) and fruit weight (472.74 g) were found significantly superior over all the other treatments. This study identified that the combined application of 50% RDF along with nano nitrogen, nano zinc and nano copper had significant influence on certain growth and yield characters on ridge gourd.

Three-stage carbon release model during macrophyte decomposition

Carbon release during macrophyte decomposing is critical for the carbon cycle in the aquatic ecosystems. Previous mechanic researches have demonstrated the different release rates of nutrients in different stages, e.g., the fast-leaching stage (in initial 4–10 days), the microbe conditioning stage with slow decay rate (from winter to spring with low temperature). Nevertheless, models for predicting these processes are still not available and the conventional used model inherently assumes a constant relative release rate. Here, we conducted a one-year in-situ decomposition experiment using the conventional (net) litterbag technique. The credibility of experimental data is increased by using fresh debris to avoid alternation of material traits caused by the conventional drying pretreatment, which is originally used in experiments for terrestrial debris. Our results demonstrated that the carbon release process showed an obvious three-stage pattern, which can be universally depicted by a piecewise three-stage exponential decaying model (r2 > 0.9). More importantly, contributions of the three key factor (i.e., leaching, microbe and macroinvertebrate) can be explicitly reflected by the corresponding relative release rate (ki, i denote i th decomposition stage), which variate greatly between different stages, with k1/k2 > 11.8 and k3/k2 > 2.63. More importantly, k3 can be further conveniently decomposed into microbe-induced k3-1 and macroinvertebrate-induced k3-2, correspondingly. Also, k3-2 showed an exponential increase with the number of macroinvertebrate (r2 > 0.95). The contributions of the microbe and macroinvertebrate can then be depicted by these two parameters. In conclusion, our model greatly increases the model realism and generality in simulating the carbon release process; Also, the explicit physical meaning of model parameters make the model mechanism clearer. This not only created the chance to further develop a mechanism-based model, but also facilitate the mechanistic study of the impacts of environmental factors (e.g., pH, dissolved oxygen) on k1, k2, k3-1 and k3-2 concerning different kinds of macrophyte, in which the parameters k1, k2, k3-1 and k3-2 acts as important ecological indicators in depicting the relative release rates caused by specific driving forces. These ecological indicators facilitate the future mechanical researches for the impacts of environmental factors on the carbon release.

Preparation and Properties of a Novel Biodegradable Composite Hydrogel Derived from Gelatin/Chitosan and Polylactic Acid as Slow-Release N Fertilizer

To improve the efficient use of nitrogen and decrease the environmental pollution of N losses, a novel and biodegradable composite hydrogel was prepared by chemical cross-linking synthesis using gelatin (Gel), chitosan (CS) and polylactic acid (PLA) as raw materials. Urea as the nitrogen source was loaded into this new biodegradable hydrogel using the solution immersion method. The chemical structures of the composite hydrogels were characterized and their properties were analyzed by XRD and XPS. The regulation of urea loading and the swelling behavior of the composite hydrogel under different temperature conditions were investigated; the release behavior and release model of the composite hydrogel in the aqueous phase was explored. The results show that the loading of urea is controllable in aqueous urea solution with different concentrations. In the water phase, it shows a three-stage sustained release behavior, that is, the initial release rate of urea is relatively fast, and the medium release rate of urea gradually slows down, and finally the nutrient release rate tends to be flat. The release behavior in the water phase fits to the Ritger-Peppas model. Within 10 min, 180 min and 900 min, the cumulative nutrient release rate of gelatin/chitosan/PLA-urea (GCPU) composite hydrogel is 20%, 70% and 86%, respectively. Compared with pure urea, The urea diffusion time of GCPU was extended by 1350-times. In addition, the GCPU also has good water absorption and water retention properties, in which average water content can reach as high as 4448%. All of the results in this work showed that GCPU hydrogel had good water absorption and retention and N slow-release properties, which are expected to be widely used in sustainable agriculture and forestry, especially in arid and degraded land.

Effect of Enzyme Activity Changes on Decomposition Characteristics of Leaf Litter Mixed Decomposition of Configurated Tree Species in Ecological Tea Garden

In the management of eco-tea gardens, the recycling of weathered leaves of the configured tree species plays an important role in the nutrients of the tea garden ecosystem. The in situ decomposition method was used to analyze the decomposition rate, elemental release, and enzymatic activity of different combinations of leaf litter in tea garden soil. The results showed that mixed decomposition accelerates the decomposition turnover period of Jiu’an ecological tea garden. The higher release rate of the litter improved the nutrient effectiveness in the ecological tea garden. The trends of CAT (catalase), AP (acid phosphatase), and PPO (polyphenol oxidase) activities were similar during the decomposition of different mixed leaf litters, while all other enzyme activities showed some differences. There were also some differences in the relationship between the enzyme activity and decomposition rate of leaf litter and the nutrient release rate related to the substrate mass content during the decomposition of leaf litter. Overall, the changes in the nutrient content of the leaf litter during decomposition promoted an increase in enzyme activity, which in turn promoted the release of leaf litter elements, shortened the turnover period of leaf litter decomposition, and accelerated the recycling of elements in the ecological tea garden.

Differential Impacts of Acacia Invasion on Nutrient Fluxes in Two Distinct Bornean Lowland Tropical Rain Forests

Invasive Acacia species can alter nutrient cycling processes in forest ecosystems, particularly affecting total litterfall production and litter decomposition patterns. This study examined the effects of exotic Acacia mangium Willd. on total litterfall production, nutrient concentrations in leaf litterfall fractions, leaf litter decomposition, and nutrient release in lowland heath (HF) and mixed dipterocarp forests (MDF) in Brunei Darussalam, Borneo. Above-ground litterfall traps were installed in HF and MDF with and without invasive Acacia present, representing four habitat types in total, and monthly collections were conducted for 12 months. Litter decomposition bags were deployed to determine the rates of decomposition and nutrient release. Habitats invaded by Acacia exhibited higher total litterfall production, increased leaf litter concentrations of nitrogen, potassium, and calcium, and increased addition of all nutrients measured in litter (nitrogen, phosphorus, potassium, calcium, and magnesium, especially in the Acacia-invaded mixed dipterocarp forest (AMDF) and nitrogen and potassium in Acacia-invaded heath forest (AHF)), reduced nitrogen and potassium use efficiencies in AHF, and reduced stand-level nitrogen and calcium use efficiencies in AMDF. Litter decomposition rates and nutrient release were lower in AMDF than in the three other habitats. The significantly higher total litterfall production coupled with higher nutrient addition in the two Acacia-invaded habitats is expected to progressively increase the abilities of these habitats to produce large quantities of nutrient-rich litter and will likely eventually lead to an enrichment of nutrients in the soil, thus facilitating further invasion by Acacia, particularly in the MDF.

Decomposition and nutrient release patterns of municipal solid waste compost in two agro-ecological zones of Uganda

BackgroundDeteriorating soil fertility is a major constraint to agricultural production and food security among smallholder farmers in Uganda and throughout sub-Saharan Africa, where the majority of the population relies on subsistence farming for its livelihoods.Unfortunately, inorganic fertiliser used as a significant soil nutrient replenishment is unsustainable, causing adverse environmental effects, including soil acidification and pollution of water bodies. Therefore, finding alternative, more sustainable, low-cost nutrient management systems is vital. This study assessed the decomposition and nutrient release patterns of municipal solid waste compost (MSWC) in a 36 weeks litter bag experiment under field conditions in two agro-ecological zones (AEZs) of Uganda.ResultsWe found a higher rate of decomposition in the South-western Grass Farmlands (SGF) agro-ecological zone (0.041 week−1, with 20% of initial compost mass remaining after 36 weeks of decay) compared to Southern and Eastern Lake Kyoga Basin (SEKB) (0.043 week−1, 32% of initial litter mass remaining). The half-life values were 16 and 17 weeks for SGF and SEKB AEZs, respectively. The nutrient release rates differed between the two study sites. The macronutrient release pattern in both sites followed the order K > P > N. The secondary macronutrients release followed the order Ca > Mg in the SGF, while in SEKB, the order was reversed. The micronutrients followed the order Cu > Mn > Fe > Zn and Cu > Mn > Zn > Fe in SGF and SEKB AEZs, respectively. The MSWC mass loss during decomposition was negatively correlated with rainfall in both AEZs and with temperature in SGF AEZ, while it was positively correlated with temperature in SEKB AEZ. However, the relationship with nutrient release rates was inconsistent in both AEZs.ConclusionsOur results showed consistent release of nutrients in all AEZs throughout the study period, which coincides with the two cropping seasons in Uganda, suggesting that smallholder farmers can use MSWC as a soil amendment to address soil fertility decline and improve crop productivity. However, because most nutrients were released almost right away in both AEZs, planting should be done at the beginning of high rainfall months when soil moisture is high to synchronise nutrient release from MSWC with crop demand and maximise nutrient uptake by crops while minimising losses to the environment. Furthermore, the inconsistent relationships between the climatic variables and nutrient release suggest that other factors, such as site-specific microbial composition, influenced MSWC nutrient release. Therefore, long-term research is needed to examine other factors affecting nutrient release in these AEZs.

Effects of the Decomposition of Mixed Plant Residues in Ecological Tea Garden Soil

(1) Background: Plant litter decomposition and its effect on soil nutrients are important parts of the ecosystem material cycle, and understanding these processes is key for species selection and allocation, to promote the effective use of litter in ecological tea gardens. (2) Methods: In situ decomposition was used in this study Changes in decomposition rate, element release, and soil properties during the decomposition of the mixed plant residues were measured. (3) Results: The decomposition rate (k) of the CCG (Camellia sinensis + Cinnamomum glanduliferum) mixed plant residue was significantly higher than that of the CS (Camellia sinensis) residue. The decomposition of the CCG, CPM (C. sinensis + Pinus massoniana), and CBL (C. sinensis + Betula luminifera) mixed plant residues showed an additive effect, whereas that of the CCL residue showed an antagonistic effect. The CBL mixed plant residue promoted the release of N; the decomposition of the CCG, CPM, CCL (C. sinensis + Cunninghamia lanceolata), and CBL residues promoted the release of TC (total carbon); and the decomposition of the CCG residue promoted the release of cellulose. After 428 d of decomposition, the four mixed plant residues had improved the soil nutrient contents to some extent. CCG and CBL residue decomposition resulted in greater improvements in soil nutrients. (4) Conclusions: The application of the mixture of material obtained by pruning C. glanduliferum, B. luminifera, and C. sinensis in an ecological tea garden accelerated the decomposition and nutrient release rates, increased soil nutrient contents, shortened the decomposition turnover period of plant residues, and accelerated the nutrient cycle of plant residues in the ecological tea garden.

Substances released during the decomposition of Vallisneria natans and Thalia dealbata

Two types of aquatic plants commonly used for the ecological restoration of rivers and lakes, Vallisneria natans (Lour.) Hara and Thalia dealbata Fraser ex Roscoe, were selected and grouped by plant parts (root, stem and foliage), and decomposing release experiments were conducted. The influence of the released substances on the water quality was analyzed, as well as the amount of nutrients released by each part of these two plants. The calculated maximum chemical oxygen demand releases from the foliage of V. natans and the foliage of T. dealbata were approximately 5.4 g/kg and 22.65 g/kg, respectively. Through three-dimensional fluorescence spectrum and parallel factor analyses, the different material compositions of the decomposing liquids from the plants were determined, and the main dissolved organic components of the decomposing liquid of V. natans were amino-acid-like and microbially derived humics, and those T. dealbata were soluble microbial by-product-like substances. The carbon-to-nitrogen ratio and humification index of each experimental group were compared. The experimental results showed that different parts of V. natans and T. dealbata had different rates of nutrient release. The dissolved organic matter in the decomposed solution can be utilized by microorganisms, which have the potential to become additional carbon sources. This study provides a new method for the treatment of aquatic plant litter. Different plant species can be used in combination according to their characteristics to ensure that better results are achieved during water treatment processes that use plant decomposing liquids as additional carbon sources.

Fe-Based Metal-Organic Frameworks for the Controlled Release of Fertilizer Nutrients.

Due to the controlled-delivery function of metal–organic frameworks (MOFs) for gases, drugs, and pesticides, iron-based MOFs (Fe-MOFs) were explored in the laboratory as a novel fertilizer, which showed potential for use in the fertilizer industry; the challenge in the industrial scale application of Fe-MOFs in practical crop production was mainly the impact of scaling-up to energy and heat transfer, as well as the reaction yield. In this study, Fe-MOFs were hydrothermally synthesized both in the laboratory scale and in the pilot scale, their structure and components were characterized using various spectroscopic techniques, and then their nutrient release and degradation behaviors were investigated. The results showed that Fe-MOFs were successfully synthesized in both scales with similar yields around 27%, and the Fe-MOFs showed a similar structure with the molecular formula of C2H15Fe2N2O18P3. The nutrients N, P, and Fe were present in the Fe-MOFs with the average contents of 6.03, 14.48, and 14.69%, respectively. Importantly, the nutrient release rate and pattern of Fe-MOFs well matched with the crop growth, which greatly promoted the rice yield. Therefore, the environmentally friendly compounds of Fe-MOFs could be industrially produced and used as an innovative fertilizer with unique features of varied nutrients and controlled release.