Superphosphate Research Articles

Effect of Continuous Application of Fertilizer and Manure on Distribution of Sulphur Fractions in a Vertisol

The fertilization experiment was started at Experimental field of Eklavya University, Damoh, Madhya Pradesh-India at a fixed location in the experimental field study was carried out. Under this study a randomized block design with eight treatments and four replications high used Urea, single super phosphate (SSP), muriate of potash, and DAP instead of SSP were employed as fertilizers in the sulphate-free treatment.

Evaluating the agronomic efficiency of alternative phosphorus sources applied in Brazilian tropical soils

Understanding the efficacy of alternative phosphorus (P) sources in tropical soils is crucial for sustainable farming, addressing resource constraints, mitigating environmental impact, improving crop productivity, and optimizing soil-specific solutions. While the topic holds great importance, current literature falls short in providing thorough, region-specific studies on the effectiveness of alternative P sources in Brazilian tropical soils for maize cultivation. Our aim was to assess the agronomic efficiency of alternative P sources concerning maize crop (Zea mays L.) attributes, including height, shoot dry weight, stem diameter, and nutrient accumulation, across five Brazilian tropical soils. In greenhouse conditions, we carried out a randomized complete block design, investigating two factors (soil type and P sources), evaluating five tropical soils with varying clay contents and three alternative sources of P, as well as a commercial source and a control group. We evaluated maize crop attributes such as height, dry weight biomass, and nutrient accumulation, P availability and agronomic efficiency. Our results showed that, although triple superphosphate (TSP) exhibited greater values than alternative P sources (precipitated phosphorus 1, precipitated phosphorus 2 and reactive phosphate) for maize crop attributes (e.g., height, stem diameter, shoot dry weight and phosphorus, nitrogen, sulfur, calcium and magnesium accumulation). For instance, PP1 source increased nutrient accumulation for phosphorus (P), nitrogen (N), and sulfur (S) by 37.05% and 75.98% (P), 34.39% and 72.07% (N), and 41.94% and 72.69% (S) in comparison to PP2 and RP, respectively. Additionally, PP1 substantially increased P availability in soils with high clay contents 15 days after planting (DAP), showing increases of 61.90%, 99.04%, and 38.09% greater than PP2, RP, and TSP. For Ca and Mg accumulation, the highest values were found in the COxisol2 soil when PP2 was applied, Ca = 44.31% and 69.48%; and Mg = 46.23 and 75.79%, greater than PP1 and RP, respectively. Finally, the highest values for relative agronomic efficiency were observed in COxisol2 when PP1 was applied. The precipitated phosphate sources (PP1 and PP2) exhibited a similar behavior to that of the commercial source (TSP), suggesting their potential use to reduce reliance on TSP fertilization, especially in soils with low clay contents. This study emphasized strategies for soil P management, aimed at assisting farmers in enhancing maize crop productivity while simultaneously addressing the effectiveness of alternative P sources of reduced costs.

A Comparative Study of Calcium Sulfate Alternatives in Compost Production for White Button Mushroom (Agaricus bisporus)

This study explores various potential substitutes for gypsum in the production of compost for white button mushrooms (Agaricus bisporus). During compost preparation, calcium sulfate (CaSO4) was replaced with calcium carbonate (CaCO3), ammonium sulfate ((NH4)2SO4), and monocalcium phosphate (Ca(H2PO4)2). Complete replacement of gypsum with calcium carbonate led to a significant pH increase during the second phase of composting, adversely affecting mushroom mycelium growth. Compost parameters were observed to be similar in scenarios where calcium sulfate was supplemented with calcium carbonate in 8:2 and 6:4 ratios, both with and without the presence of ammonium sulfate, and in 3:1 and 1:1 mixtures of calcium sulfate and monocalcium phosphate, when compared to traditional gypsum-based processes. All experimental compost mixtures yielded comparable mushroom crops in cultivation trials. Notably, the 8:2 mixture of calcium sulfate and calcium carbonate demonstrated superior performance in cultivation trials relative to the 6:4 mixture. However, supplementing these mixtures with ammonium sulfate resulted in similar crop yields. Monocalcium phosphate also emerged as a promising partial gypsum substitute, showing comparable crop production in both 3:1 and 1:1 ratios to the technological optimum. The exploration of alternative calcium sources like calcium carbonate and monocalcium phosphate reflects the adaptability of the industry in response to resource availability challenges. The potential use of byproducts like ammonium sulfate from the composting process itself offers a cost-effective and environmentally friendly approach to compost formulation, underscoring its worldwide relevance.

Loblolly Pine Mid-Rotation Phosphorus Fertilization with Poultry Litter Ash or Triple Superphosphate

ABSTRACT Loblolly pine (Pinus taeda L.) grown on infertile coastal plain soils typically shows a growth response to N and P applied at mid-rotation. The objectives of this study were to determine whether less soluble poultry litter ash (PLA) provides an adequate supply of P compared to triple superphosphate (TSP), and assess effects on P mineralization and runoff loss. Effects of 56 kg P ha−1 as either PLA or TSP, and no fertilization were compared using an 11-year-old stand of two loblolly pine genotypes on a loamy sand in a completely randomized design. Tree height, diameter and foliar nutrients, soil Mehlich 3 P and phosphatase activity (A and E horizons), and P in surface runoff were monitored. Through more than two years, P fertilization had no effect on tree growth. Similar foliar P with PLA or TSP, together with increasing foliar and soil P over time, suggested that PLA is an adequate source of P for loblolly pine. Neither fertilizer suppressed P mineralization as measured by phosphatase activity. The advantage of PLA compared to TSP is potentially much less runoff P loss.

Parsley production using organic sources of phosphorus

Parsley is a condiment produced mainly by small producers, often in the organic system. Organic fertilizers make nutrients slowly available to plants when compared to inorganic fertilizers, an important quality for phosphorus (P), which is a nutrient that tends to fixate and adsorption. Thus, the objective of this work was to evaluate the production of parsley with the use of organic sources of phosphorus in different proportions. Fourteen treatments were evaluated, resulting from the factorial 6 x 2 + 2: six proportions of two phosphate fertilizers (thermophosphate Yoorin® (TY) and bone meal (BM)), two doses (recommended (180 kg.ha-1 of P2O5, and double this) + two controls (without phosphate fertilizer; and with inorganic triple superphosphate fertilizer (recommended dose)). The proportions were: 100% P with TY; 80% P with TY + 20% with BM; 60% P with TY + 40% with BM; 40% P with TY + 60% with BM; 20% P with TY + 80% with BM; 100% P with BM. Shoot height, number of leaves, fresh and dry weight of leaves in two harvests and the total of these two harvests were evaluated. No significant differences were obtained in the two harvests. The lack of effect to phosphate fertilization may be related to the high initial P content in the soil (123 mg.dm-3), which shows that in this case, fertilization with this nutrient is not necessary to produce parsley, despite the official recommendation to fertilize with phosphorus in a soil with a high P content.

Effect of Bone Char Application on Soil Quality, Soil Enzyme and in Enhancing Crop Yield in Agriculture: A Review

Soil quality, in contrast to air or water, exhibits a heightened level of heterogeneity and necessitates closer examination due to its impact on the well-being of flora, fauna, and human beings. Organic carbon is considered a fundamental indicator of soil quality, as it plays a significant role in strategies aimed at mitigating climate change. The generation of bone char arises from a thermochemical conversion process involving defatted bones. Specific attention is focused on the solubility of P compounds, which serves to classify bone chars as potential slow-release P fertilizers. The introduction of P into the soil can be enhanced through an "internal activation" process facilitated by the adsorption of reduced S compounds. Additional properties of agronomic significance originate from the porosity of bone char, which promotes water retention and provides a habitat function for soil microorganisms. The evaluation of soil quality has been a longstanding practice, involving an examination of physical and chemical characteristics such as pH, nitrogen levels, soil organic carbon, bulk density, accessible water, aggregate stability, particle size distribution, and soil structure. Recently, the concept of soil quality has been expanded to encompass the notion of soil health, which is perceived as a finite, non-renewable resource that undergoes constant change. Research also demonstrates the crucial role of soil biota in the assessment of soil quality, as they exhibit rapid responsiveness to disturbances. Animal bones undergo a process of defatting, degelatinization, and subsequent incineration at temperatures ranging from 600-800°C to produce bone char (BC). Reports indicate that typical BC contains 152 g P kg<sup>-1</sup>, 280 g Ca kg<sup>-1</sup>, and 6.5 g Mg kg<sup>-1</sup>, with carbon content typically falling below 100 g kg<sup>-1</sup>. The solubility of bone char in the soil depends on factors such as pH and the soil's capacity to absorb P, situating it within the range between rock phosphate and triple super phosphate (TSP). The application of bone char to the soil can enhance soil health, resulting in increased crop yield and improved quality.

Response of tef yield and yield components to nitrogen and phosphorus fertilizers.

The challenge facing Ethiopian farmers are the combination of low soil fertility and reduced agricultural productivity. The study aimed to quantify nitrogen and phosphorus-containing fertilizers for tef production in Sekota and Lasta-Lalibela districts, using four nitrogen and three phosphorus levels from urea and triple super phosphate sources. The Results showed that nitrogen and phosphorus fertilizers significantly affected tef yield and yield components. Application of nitrogen at the rate of 92 kg ha-1 increased tef grain yield by 131.01%, 87.78% and 182.23% in Woleh, Sayda and Lasta Lalibela districts, respectively, compared to control treatment. Similarly, 23 kg ha-1 phosphorus increased tef grain yield by 7.42 and 8.52% in Woleh and Lasta Lalibela, respectively. In Lalibela and Woleh, the application of 92 kg N ha-1 resulted in a maximum net benefits of 2099.6 and 2007 United States Dollar (USD) respectively. Furthermore, in Sayda, the application of 92 kg N ha-1 and 23 kg P2O5 ha-1 yielded a net benefit of 1812.55 USD. The marginal rate of return (MRR) from these applications was 539.6% in Lalibela, 781% in Woleh and 352.44% in Sayda. Therefore, application of 92 N and 23 kg P2O5 ha-1 is appropriate for maximum tef production in Sekota and Lasta districts of Amhara region. Further research and extension services should focus on promoting the adoption of these optimized fertilizer practices among smallholder farmers to maximize the sustainable production of tef.

Lignin-rich extracts as slow-release coating for phosphorus fertilizers

Lignin (L) is the most abundant three-dimensional polymer with versatile yet attractive structural features and chemical properties for applicability as a coating. The properties of lignin are mainly related to its botanical origin, structure and extraction method. Although there has been a lot of interest in using lignin in fertilizing systems, only limited attempts have been dedicated to studying the effect of the lignin structure and origin on the release of P fertilizer. Thus, the aim of this work was to study the effect of lignin polymers, extracted from different plant biomass, as coating materials for P fertilizers. Thus, the effect of the structural features originating from the botanical origin on the properties of coated fertilizers and their slow release were established. To this end, three lignocellulosic biomass, namely olive pomace (OP), barley straw (BS) and wood shavings (WS) were used as feedstock to extract lignin polymers. Those chemical compositions and thermochemical properties were characterized prior to their application as coating for triple super phosphate (TSP) fertilizer. Coated fertilizers were characterized for their morphology and coating thickness prior to their evaluation as slow release P-based fertilizer. A distinct slow P release behavior was reported for lignin-coated fertilizers with TSP@L-OP being the slowest as compared to TSP@L-WS, TSP@L-BS as well as pristine TSP, which confirm that the botanical origin and most likely the chemical structures of lignin has significant impact on the properties of the coating materiel. A 100 % release of P from the uncoated TSP was observed after 3 days, while the released amount ranged from only 16.9 % for TSP@L-OP up to 33.4 % for TSP@L-BS. The impact of these coated fertilizers on nutrients uptake and wheat growth was also scrutinized and an noticeable improvement of wheat shoot biomass was observed with the coated TSP treatments reaching up 57.8 % for TSP@BS, 78.1 % for TSP @WS and 93.7 % for TSP @OP, compared to uncoated TSP. This was concomitant to a slight increase of P concentration in shoots, roots and rhizosphere soil, which confirmed the positive effect of slow release P fertilizers on plant growth.

Residual Effects of Microbial Treated Paddy Residues Applied to Zero Till Maize on Growth and Yield of Summer Greengram

Background: Farmers’ conventional tillage and residue removal practices in rice-maize-greengram systems in India are input-intensive, costly and soil degradative. A number of soil quality issues have emerged due to continuous cropping and burning of residues threatening the sustainability of rice based cropping systems for the last more than four decades. Nevertheless, the in-situ or in-field decomposition of crop residue using microbial inoculum is rarely studied. This necessitated the use of microbial consortia developed by a combination of potent strains of fungi which can perform harmoniously for rapid decomposition of crop residues. Methods: A field experiment was conducted during 2020-21 and 2021-22 with eight residue-management treatments and three fertility levels to zero till maize at college farm, Rajendranagar, PJTSAU using strip plot design and the residual effect on the succeeding greengram was studied. Result: Greengram growth and yield were significantly higher under residual effect of incorporation of residues treated with microbial consortia consisting of Trichoderma viridae, Aspergillus awamori and Phanerocheate spp. along with 300:100:100 kg ha-1 of N, P2O5 and K2O (125% RDF) and P supplied in the form of single super phosphate (SSP) under zero tillage during summer, 2021 and 2022. Growth parameters like plant height, leaf area index, dry matter production and yield attributes like number of pods plant-1, pod length and number of seeds pod-1 in greengram were higher under residue incorporated plots compared to residue burning, removal and retention plots with 125% RDF.

Primary and residual impacts of phosphoric acid modified biochar on growth and concentrations of essential and non-essential elements in lettuce and second crop arugula

The study aimed to explore how phosphoric acid-modified rice husk biochar (PBC) affects the growth and concentrations of essential and non-essential elements in two crops: lettuce as the primary crop and arugula as the secondary crop. The treatments consisted of a no P fertilized control and 250 mg P kg−1 sourced either from PBC, triple super phosphate (TSP) or phosphoric acid (PA). When subjected to phosphorus (P) sources, both lettuce and arugula exhibited a noteworthy rise in their dry weights compared to the control plants. PBC treatments significantly increased P concentration in both plants. Although the PBC treatment decreased lettuce nitrogen (N) concentration, it had no impact on arugula N concentration. Phosphorus treatments resulted in a decrease in lettuce K concentration, whereas it increased in arugula. Calcium (Ca), magnesium (Mg) and sulfur (S) concentrations in both plants were not affected by P sources. The zinc (Zn) concentrations of the plants notably decreased with P treatments. Moreover, P treatments led to a reduction in manganese (Mn) concentration specifically in arugula. PBC significantly increased the silicon (Si) concentrations of lettuce plants. The application of PA significantly increased the vanadium (V) concentration in arugula. Phosphoric acid treatments resulted in an increase in the plant bromine (Br) concentrations. To conclude, PBC may serve as an alternative P source, potentially being as effective as or even more effective than other P sources in influencing plant nutrition, without causing an undesirable elevation of non-essential elements in plants.

Scarcity of P-fertilisers: Humic-complexed phosphate as an adaptive solution for wheat and maize under rainfed conditions

The current context of food security and global geopolitical crises calls for proactive efforts to seek adaptive strategies for limited resources in agriculture. The production of phosphatic-based fertilisers has caused a substantial depletion of natural phosphorus (P) reserves, raising concerns about price increases due to the growing demand for P. The aim of the study is to assess whether the use of liquid organo-mineral P-complexes can be an adaptive strategy to address the issue of the limited P-fertiliser resource. A complete randomised block design was implemented with three replicates, spanning two contrasting cropping seasons under a Mediterranean climate with reduced tillage and rainfed conditions. The study aimed to assess the response of a durum wheat–maize rotation to various rates of liquid organo-mineral P-complexes (humic-complexed phosphate; HCP) in comparison to granular triple superphosphate (TSP). The evaluation focused on several parameters, including P availability, plant architecture, dry matter accumulation, grain yield and yield components and P use efficiency (PUE) for both durum wheat and maize. The results revealed that applying HCP at a rate of 4 or 8 kg ha−1 increased soil P availability on average by 66% and 144%, respectively, compared to the control (no P-fertilisation), although a significant interaction with the monitoring year emerged. For wheat, applying HCP at a rate of 8 kg ha−1 of P resulted in higher grain yield (+15%), protein content (+0.9%) and P uptake (+48%) than the control on average considering both monitoring years. In the season characterised by favourable rainfall patterns, the application of HCP at 5 or 10 kg ha−1 of P for maize showed similar effects in terms of soil P availability, dry matter accumulation, grain yields and PUE. Conversely, in the season marked by a deficiency in summer precipitation, low PUE for maize was observed for HCP fertilisers, although they remained positive, unlike the case of TSP. Using HCP in conservation agriculture appears promising as an adaptive solution to address P-fertiliser scarcity, especially amid food security challenges and global crises. However, further studies are required to validate these findings in diverse pedo-climatic contexts and cropping systems.

Reuse of Soils Fertilized with Ash as Recycling Derived Fertilizer Revealed Strong Stimulation of Microbial Communities Involved in P Mobilization in Lolium perenne Rhizospheres

Circular economy recycling-derived fertilizers (RDF) have the potential to replace linear economy fertilizers such as unsustainable superphosphates. Here, effects of ash RDF treatments in Irish grassland cultivation were investigated in a simulated second growing season. Soil fertilized in a preceding pot trial with superphosphate (SP), poultry-litter ash (PLA) and sewage-sludge ash (SSA) at P concentration of 60 kg P ha−1 and a P-free control (SP0) was reused in a microcosm trial. Lolium perenne was cultivated for 54 days in six replicates with a full complement of micro- and macro-nutrients other than P. PLA treatments provided higher dry weight shoot yields than SP0, while SSA and SP overlapped with SP0 and PLA. Most probable number (MPN) analysis showed that phosphonate- and phytate-utilizing bacterial abundance was significantly increased in PLA. Alkaline (phoD) phosphomonoesterase gene fragments were significantly more abundant (qPCR) in the ashes than the superphosphate or P-free control. Bacterial communities were significantly affected by the P application. Similarly, a significant separation of treatments was confirmed in a canonical correspondence analysis of the phoD-harboring community. The genera Streptomyces and Xanthomonas were significantly higher in abundance in the ash RDFs. These results demonstrated the potential benefits of ash RDF treatments as an alternative P source.

Unexpectedly, triple super phosphate fertilizer induces maize drought resilience

Phosphorus fertilizer is commonly applied to soils in crop production as diammonium phosphate (DAP). To decrease ammonium addition to the environment, triple super phosphate (TSP) is being considered as a DAP replacement. This study was undertaken to compare the response of maize plants to soil fertilization with TSP vs. DAP under well-watered conditions, under soil-drying conditions, and root hydraulic conductance. It was found for well-watered conditions in a controlled environment that there was no difference in plant growth between DAP to TSP treatments. In soil dry-down experiments, however, the initiation of the decrease in transpiration rate was unexpectedly quite different between DAP and TSP treatments. The soil water content threshold for initiation of decrease in transpiration rate with DAP treatment (average fraction transpirable soil water for two experiments = 0.285) was consistent with common observations, but the threshold associated with TSP treatment occurred at an unusually high soil water content (average fraction transpirable soil water for two experiments = 0.545). The higher threshold with TSP resulted in an extended period of soil water use, i.e. soil water conservation. Soil water conservation resulting from the TSP treatment was associated with a 27% greater shoot mass accumulation following a 4-wk re-watering period after the water-deficit treatment than measured with the DAP treatment. The high threshold for decrease in transpiration resulting from TSP was consistent with measured lower root hydraulic conductance as compared to DAP treatment. The unexpected discovery of TSP-induced initiation of transpiration rate decrease at high soil water content is consistent with greater crop drought resilience.

The effect of phosphorus utilization efficiency on durum wheat cultivars under semi-arid environmental conditions

Faced with the high cost of phosphate fertilisers in several African countries, including Algeria, and in order to better select varieties according to their fertiliser use efficiency, this study was proposed. The goal of the study was to determine how “variety” impacts durum wheat's capacity to utilize phosphorus effectively and to try to pinpoint the agro-morphological factors that contribute to this efficiency so that they can be taken into consideration when choosing which varieties to sow in semi-arid environments. The experimental setup consisted of a split plot with two investigated factors and three repetitions, with the main plot receiving the phosphate treatment while the sub plot receives the variety. The trial set up consisted of 11 durum wheat varieties, which were cultivated over two years successively. The PUE of the fertiliser, provided in 46% triple superphosphate (TSP) granules, and agro-morphological parameters like aerial biomass, plant height, grain yield and yield components were determined. The findings demonstrated that triple superphosphate, a type of phosphorus fertilizer, increases grain yield by between 40 and 60% for all varieties examined as compared to the phosphorus-free control at the average dose employed in this field trial, or 20 kg P2O5.ha-1. This increase in yield is due to an increase: from 20 to 22% in the number of ears per m², 41.5% in the number of grains per ear, and 9% in the average weight of the grain. The PUE is strongly correlated to the yield components (Number of ears per square meter- NEM, Number of grains per ear- NGE, thousand grain weight- TGW and Yield) but also to the height at heading (r=0.86) and dry matter (r=0.85). Phosphorus use efficiency is also strongly correlated to flag leaf length and width as well as leaf area. Also, that genotypes with higher weight of thousand grains (WTG) showed better use of available phosphorus. The principal component analysis (PCA) confirms that the efficiency of phosphorus use by the varieties tested explains a large portion of the variation noted in these varieties. This genetic variation in PUE was associated with plant height and phosphorus content of the sown grains. These results could be of a significant impact in improving rainfed durum wheat productivity in semi-arid areas and preserving the environment as well. Key words: Durum wheat, Phosphorus use efficiency, Plant’s height, Genetic variation, Fertilizers’ reduction

Water regime and fertilizer‐phosphorus source effects on greenhouse gas emissions from rice

AbstractGreenhouse gas (GHG) emissions from rice (Oryza sativa) systems have been correlated to water management practice, but to date, no study has directly evaluated three main GHGs (i.e., methane [CH4], nitrous oxide [N2O], and carbon dioxide [CO2]) under flood‐ and furrow‐irrigated conditions at the same time as affected by various fertilizer‐phosphorus (P) sources, in particular the reportedly slow‐release struvite‐P source. Therefore, the objective of this study was to evaluate the effect of water regime (flooded and furrow‐irrigated) and fertilizer‐P source (diammonium phosphate, chemically precipitated struvite, electrochemically precipitated struvite [ECST], triple superphosphate, and an unamended control) on GHG emissions and two‐ and three‐gas global warming potentials (GWP* and GWP, respectively) in the greenhouse. Methane emissions were 10 times greater (p < 0.05) under flooded (29.4 kg CH4 ha−1 season−1) than under furrow‐irrigated conditions (2.9 kg CH4 ha−1 season−1), and four times lower (p < 0.05) with ECST (3.4 kg CH4 ha−1 season−1) than other fertilizer‐P sources, while CO2 emissions were three times greater (p < 0.05) under furrow‐irrigated (23,428 kg CO2 ha−1 season−1) than under flooded (8290 kg CO2 ha−1 season−1) conditions. The GWP* under furrow‐irrigated conditions was almost 40% lower (p < 0.05) than under flooded conditions. Although N2O emissions were unaffected by fertilizer‐P source, the N2O contribution to GWP* was more than 80% under furrow‐irrigated conditions. Flood‐ and furrow‐irrigated water regimes require diversified approaches in GHG mitigation, where the best management for ECST needs to be more fully evaluated.

Trade-Off Strategy for Usage of Phosphorus Fertilizer in Calcareous Soil-Grown Winter Wheat: Yield, Phosphorus Use Efficiency, and Zinc Nutrition Response

Although phosphorus (P) fertilizer application is widely used to improve production, irrational P application has a negative impact on the zinc (Zn) nutrition of cereal crops. Previous researchers observed and confirmed that P application decreases grain Zn concentrations and bioavailability in cereal crops. However, it remains unclear whether different P fertilizer types can alleviate the antagonism of P and Zn in the soil and grain and, thus, enhance the Zn nutritional level of cereal crops while maintaining production. Thus, a completely randomized pot experiment was conducted on winter wheat grown in two calcareous soils (lime concretion black soil and fluvo-aquic soil). Five P fertilizer types (single superphosphate, diammonium phosphate, fused calcium–magnesium phosphate, triple superphosphate, and ammonium polyphosphate, abbreviated, respectively, as SSP, DAP, FMP, TSP, and APP) were applied to each soil compared to no P fertilizer (CK). Plant and topsoil samples were collected during the flowering and maturity stages of winter wheat, and biomass, Zn concentrations in each organ, and grain phytic acid concentrations were analyzed. Grain yield was not affected by the application of different P fertilizer types to lime concretion black soil, while it was significantly increased by the application of TSP and APP to fluvo-aquic soil. The application of DAP and APP effectively promoted soil available Zn concentrations in both calcareous soils. In lime concretion black soil, the application of FMP significantly increased Zn remobilization to grains, while the application of DAP increased post-anthesis Zn uptake, thereby increasing grain Zn concentrations and its bioavailability. In fluvo-aquic soil, post-anthesis Zn remobilization and uptake were significantly increased by the application of TSP and APP, finally achieving higher grain Zn concentrations and Zn harvest index and effectively promoting grain Zn bioavailability. In conclusion, the rational application of DAP to wheat grown in lime concretion black soil and of TSP or APP to fluvo-aquic soil can achieve superior grain Zn nutrition quality while concurrently retaining high production and high P use efficiency, reducing micronutrient deficiency and further contributing to green agricultural development and human health.

Methods for testing short- and long-term phosphorus fertilizing efficiency of products with varying solubility

Phosphorus (P) recovery from nutrient-rich side streams (NRSS) and derived products is crucial to ensure sustainable food production in the future and to enhance the circular economy, but the agronomic efficiency of these products needs to be validated to reach these targets. In this study, we used a Hedley fractionation scheme and the diffusive gradient in thin film (DGT) method to determine P availability in 83 NRSS and derived products originating from Finland, Sweden, and Germany. Furthermore, two independent short- and long-term growth experiments with barley (Hordeum vulgare L.) and ryegrass (Lolium perenne L.), respectively, were conducted to evaluate P availability in 15 selected NRSS. In addition to the DGT soil test, different fertilizer extractants, 2 % formic acid (FA), 2 % citric acid, and neutral ammonium citrate, were tested for predicting P availability in growth experiments. Livestock manures and slurries were found to contain a notable portion of labile P and were comparable to superphosphate (SP). Despite the low shares of labile P in struvite (7.2 %) and AshDec® (1.3 %), they exhibited P availability comparable to SP fertilizer, as indicated by DGT (99 % and 238 % of SP equivalence, respectively). This suggests that factors other than solubility influenced P availability in these side streams. The DGT method as a promising soil test predicted both short- and long-term P availability better than the selected conventional chemical extraction methods did. The 2 % FA extract exhibited the poorest performance, overestimating P availability in some nutrient sources while underestimating others in long-term. These findings enhance our understanding of P availability in potential raw materials for fertilizers, facilitating more effective P management strategies in the circular economy.

Struvite-phosphorus effects on greenhouse gas emissions and plant and soil response in a furrow-irrigated rice production system in eastern Arkansas

Phosphorus (P) fertilizers with low water solubility, like struvite (MgNH4PO4·6H2O), have been identified to possibly reduce nutrient losses in furrow-irrigated cropping systems. However, there is a lack of research on the impacts of P and nitrogen (N) fertilization on greenhouse gas [GHG; i.e., methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)] production in furrow-irrigated rice (Oryza sativa). The objective of this study was to evaluate the effects of electrochemically precipitated struvite (ECST), chemically precipitated struvite (CPST), triple superphosphate (TSP), diammonium phosphate (DAP), environmentally smart nitrogen (ESN), and an unamended control (CT) on GHG emissions, global warming potential (GWP), and plant and soil responses at the up-slope position of a furrow-irrigated rice field in east-central Arkansas. Seasonal CH4 and CO2 emissions did not differ (P > 0.05) among fertilizer treatments, while N2O emissions were greater (P = 0.02) from CT (i.e., 5.97 kg ha−1 season−1), which did not differ from ECST, and were lowest from ESN (1.50 kg ha−1 season−1), which did not differ from TSP, CPST, ECST, and DAP. Global warming potential was greatest (P < 0.05) from CT (1612 kg CO2 eq. ha−1 season−1), which did not differ from ECST, and was lowest from ESN (436 kg CO2 eq. ha−1 season−1), which did not differ from TSP, ECST, CPST, and DAP. The combination of numerically greater yield and lower N2O emissions from CPST and ESN suggested that slow-release fertilizers could constitute an effective mitigation tool to reduce GHG emissions, maintain production, and improve sustainability in furrow-irrigated rice systems.

Impacts of Organic and Non-organic Paddy Farming Practices on Surface Water Quality in Selected Areas

Paddy (Oryza sativa L.) cultivation plays major role in Sri Lanka. Mainly Organic and Non-organic paddy farming methods are conducted. Organic paddy farming method only used organic fertilizers and non-organic paddy farming method used chemical fertilizers which are Urea, Triple Super Phosphates. Therefore, farming practices can be affected to the surface water quality creating various health hazards. The study was conducted from November 2021 to February 2022 (Maha season) to assess the impact of organic and non-organic paddy farming practices on surface water quality in Wallewala, Homagama, and Kottawa paddy agricultural lands by analyzing pH, EC, TDS, DO, BOD, COD, total hardness, nitrate, nitrite, phosphate, sulfate, chloride, potassium, zinc, and chromium. Wallewala is newly created environment sensitive agricultural land in less human influence. Both organic and non-organic paddy lands are in that area. Kottawa paddy lands are cultivated only chemical fertilizers and the Homagama paddy lands are cultivated by organic fertilizers. Randomly, six and nine surface water samples were collected from paddy irrigated systems in Wallewala area represent to organic and non-organic paddy lands respectively. Randomly, five and six surface water samples were collected from paddy irrigated systems in Homagama Organic, and Kottawa non-organic paddy lands respectively. The water from both paddy systems, min pH (5.25±0.04), max EC (315±1.00 μScm-1 ), min DO (6.13±0.06 mgL-1), max BOD5 (2.82±0.06 mgL-1), max sulfate (205.76 ppm), max chloride (45.91 ppm), max K (5.63 ppm), and max Zn (0.12 ppm) were found, while the study revealed that all the water quality parameters were not exceeded the reported ambient water quality standards for inland waters in Sri Lanka for irrigation purposes. Further EC, TDS, COD, total hardness, sulfates, chloride, potassium, and zinc were greater in non-organic paddy lands in both Wallewala and Kottawa areas. According to the obtained data, there was no water pollution from the paddy cultivation in respective areas. But these results indicate that water quality parameters vary with the utilized fertilizers. 
 Keywords: Paddy cultivation, Water quality, Organic paddy farming, Non-organic 

Different extractable pools of Cd and Pb in agricultural soil under amendments: Water-soluble concentration sensitively indicates metal availability

Identification of the most appropriate chemically extractable pool for evaluating Cd and Pb availability remains elusive, hindering accurate assessment on environmental risks and effectiveness of remediation strategies. This study evaluated the feasibility of European Community Bureau of Reference (BCR) sequential extraction, Ca(NO3)2 extraction, and water extraction on assessing Cd and Pb availability in agricultural soil amended with slaked lime, magnesium hydroxide, corn stover biochar, and calcium dihydrogen phosphate. Moreover, the enriched isotope tracing technique (112Cd and 206Pb) was employed to evaluate the aging process of newly introduced Cd and Pb within 56 days’ incubation. Results demonstrated that extractable pools by BCR and Ca(NO3)2 extraction were little impacted by amendments and showed little correlation with soil pH. This is notable because soil pH is closely linked to metal availability, indicating these extraction methods may not adequately reflect metal availability. Conversely, water-soluble concentrations of Cd and Pb were markedly influenced by amendments and exhibited strong correlations with pH (Pearson's r: -0.908 to -0.825, P < 0.001), suggesting water extraction as a more sensitive approach. Furthermore, newly introduced metals underwent a more evident aging process as demonstrated by acid-soluble and water-soluble pools. Additionally, water-soluble concentrations of essential metals were impacted by soil amendments, raising caution on their potential effects on plant growth. These findings suggest water extraction as a promising and attractive method to evaluate Cd and Pb availability, which will help provide assessment guidance for environmental risks caused by heavy metals and develop efficient remediation strategies.