Monoammonium Phosphate Fertilizer Research Articles

Fertilizer price behavior in Brazil - 2018 to 2021

The aim of this paper is to track the behavior of fertilizer prices from 2018 to 2021, highlighting the determinants and consequences. We used data on the average monthly national prices of urea, potassium chloride and monoammonium phosphate fertilizers, obtained from the National Supply Company (CONAB). A comparative analysis was carried out to show the variation in prices over the period studied, taking into account indicators such as the dollar index, oil prices, agricultural production, fertilizer import data, national fertilizer production and freight rates. The results of the research indicate that Brazil's external dependence on fertilizer-exporting countries makes it susceptible to exchange rate fluctuations, the prices of raw materials, such as oil, and global political relations, in addition to the law of supply and demand in the market.

Micronutrients in coated phosphate fertilizer improve precision distribution and nutrient use efficiency of soybean

AbstractChallenges regarding uniform micronutrient distribution and P‐use efficiency in agricultural soils are common. Micronutrients can be added as coated P fertilizers, creating multi‐nutrient fertilizers for crops to address this issue. The objective of this study was to quantify the diffusion and availability of P, B, Cu, Mn, and Zn in coated P fertilizers. Another objective was to evaluate the nutrient uptake, partitioning, and yield of soybeans. Treatments were monoammonium phosphate and NPS (nitrogen, phosphorus, sulfur) fertilizer coated with Maxxi‐Phós and either Wolftrax, Microsol, or MIB Precise. Applied concentrations of B and Cu varied between 0.15% and 0.05%. The Mn and Zn ranged from 0.45% to 0.15%. Nutrient accumulation and recovery were assessed in the greenhouse and field trials. P diffusion ranged from 5.58 to 18.88 mm in 336 h. Micronutrient use efficiencies varied according to the soybean (Glycine max) phenological stages, with emphasis on the V4 stage, which resulted in the following values: B (0.65% to 13.89%), Cu (6.73% to 62.84%), Mn (0.73% to 3.36%), and Zn (0.01% to 2.34%). Nutrient exports were: 55.7 kg of P2O5 ha−1, 209.6 g of B ha−1, 109 g of Mn ha−1, 216.7 g of Zn ha−1, and 64.3 g of Cu ha−1. There was significant absorption (p ≤ 0.05) of B, Mn, and Zn at stages R1–R5.1 in the field trial, whereas it was from V4 to R1 for Cu. As a multi‐nutrient fertilizer for soybeans, micronutrient‐coated P fertilizers could replace exported nutrients.

Activated ZnCl2 biochar and humic acid as additives in monoammonium phosphate fertilizer: Physicochemical characterization and agronomic effectiveness

Activated zinc biochar (ZnBC) and humic acid (HA) were used as coating agents in a soluble monoammonium phosphate (MAP) to modify phosphorus (P) use efficiency by altering adsorption/desorption kinetics between the granule region and the soil. The coated treatments MAPZnBC and MAPHA were compared with MAP through P diffusivity, kinetics, and agronomic evaluation. Eucalyptus sawdust was used as biomass for biochar synthesis, and a pre-pyrolysis treatment with zinc chloride (ZnCl2) was applied. The P diffusivity was evaluated in the fertosphere zone. Adsorption and desorption potential of the ZnBC compared with control biochar (BC) was evaluated separately. Desorption kinetics of P from soil was assessed after incubation with MAPZnBC and MAPHA. The shoot dry matter yield (SDM), P uptake, and P use efficiency (PUE) were evaluated with a pot experiment in a clay Oxisol sown with maize and soybeans as successive plant trials, under glasshouse conditions. Surface area values of 940 and 305 m2 g−1 combined with adsorption capacities of 106 and 53 mg P g−1 for ZnBC and BC, respectively, confirm the increased capacity of activated biochar to adsorb P. Both MAPZnBC and MAPHA decreased P diffusivity compared to MAP after 20 days of incubation. Moreover, MAPZnBC and MAPHA presented 20% and 34% more water-soluble phosphorus recovery. MAPZnBC expressed an increase in SDM while MAPHA highlighted P uptake and PUE compared with MAP. Both kinetic studies and agronomic evaluations showed that ZnBC and HA are suitable as coatings for phosphate fertilizers in terms of increasing P efficiency in the fertosphere on high P-fixing soils.

Economic Feasibility of Management of Fertilization in the Soybean-Corn System Cultivated in Succession

Fertilization management is one of the agricultural practices that demand high investment. Thus, the objective was to evaluate the economic viability of using combinations of fertilizers applied to soybean and corn cultivated in succession in Goiás Savanna soil. The experiment was carried out in the field, in randomized blocks. The fertilization management consisted of the combination of monoammonium phosphate fertilizers; urea; 08:40:00 +9.3%S and 3.2% Ca; simple superphosphate; potassium chloride; elemental sulfur; polyhalite (37% K2O + 9.2% S, 5.8% Ca and 1.7% Mg) and polyhalite S (14% K2O + 19.2% S, 12% Ca and 3.6% Mg) which were applied in soybean sowing and evaluated the residual effect on corn. The economic assessment took into account crop productivity and fertilizer prices in the 2018/2019 agricultural year. For each treatment, the operating cost (COi) and profitability indicators were calculated: gross revenue (GRi); net revenue (NRi); profitability index (PITi); equilibrium production (Yei) and equilibrium price (Pei). Crop productivity was not influenced by fertilizer management, showing that economic indicators can help producers choose the management with the best return and that adjusts to the financial situation of the rural company. Thus, it is concluded that the management of MAP + KCl fertilization was economically outstanding in soybean cultivation and the MAP/S + KCl applied to soybeans, associated with nitrogen fertilization in corn coverage was the most viable for off-season corn. The economic indicators showed that the MAP+KCl fertilization performed on soybean, associated with urea in corn coverage, is the most viable management system for the soybean-corn production system cultivated in succession.

Assessing phosphorus nutritional status in maize plants using leaf-based hyperspectral measurements and multivariate analysis

ABSTRACT Remote sensing techniques have the potential to monitor physiological and biochemical changes caused by nutritional stress in plants. However, few studies have monitored the influence of foliar phosphorus levels on the spectral responses of plants, especially maize. This work aimed to assess phosphorus nutritional status in maize plants subjected to different sources and doses of phosphate fertilizer using leaf-based hyperspectral measurements and multivariate analysis. The specific goals addressed were a) the qualitative analysis of the spectral response, b) the identification of significant spectral wavelengths for differentiating doses of phosphate fertilizer, and c) the development of a spectral model for classifying the nutritional status of maize as an effective approach for crop nutritional assessment. Two experiments with different sources and doses of phosphate fertilizer were carried out: experiment 1 with monoammonium phosphate fertilizer (MAP) and experiment 2 with simple superphosphate fertilizer (SS). Hyperspectral reflectance (visible and near-infrared wavelengths) was collected at the V6 development stage of maize using an ASD Fieldspec 3 Jr Spectroradiometer, totalling 100 samples for each experiment. The collected data were submitted to principal component analysis (PCA) and linear discriminant analysis (LDA). The spectral signature of leaves showed higher reflectance values in the Vis spectral interval and lower reflectance in NIR under the absence of fertilization. For the other treatments, smaller differences in their spectral response were observed, especially for experiment 2. For experiment 1, the LDA achieved accuracy from 46 to 72% in the cross-validation step and from 50 to 75% in the external validation step. For experiment 2, the accuracy ranged from 25 to 82% in the cross-validation step and from 28 to 85% in the external validation step. In general, most misclassification was observed among treatments with similar fertilizer doses. These results suggest the potential of using hyperspectral data to monitor leaf P levels in maize, which contributes to the determination of crop management zones based on production variability under P limitation, in addition to optimizing the use of chemical inputs and guaranteeing greater sustainability of production systems.

A green approach to the valorization of kraft lignin for the production of nanocomposite gels to control the release of fertilizer

AbstractThe valorization of industrial by‐products is a green approach. This work investigates the valorization of kraft liquor from paper pulping as a precursor in the production of lignin‐based nanocomposites to control the release of monoammonium phosphate (MAP) fertilizer. These nanocomposites were prepared from the stoichiometry of lignin nanoparticles (LNPs) and chitosan (Cs). The lignin nanoparticles were synthesized by solvent exchange and dialysis using two polar solvents: tetrahydrofuran (THF) and ethylene glycol (EG). These LNPs were characterized by transmission electron microscopy (TEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and textural techniques. The TEM images showed that the shapes of LNPs based on THF (LNPT) and LNPs based on EG (LNPE) were spherical, with an average particle size of 300 ± 40 nm and 23 ± 6.5 nm, respectively. Textural characteristics and FTIR revealed no change in the chemical nature of the two synthesized LNPs, and their Brunauer, Emmett and Teller (BET) surface area and average pore diameter ranged from 0.78 to 1.58 m2 g−1, and 4.069 to 5.20 nm, respectively. Swelling, functional groups, and the thermal, morphology, and MAP release characteristics were investigated for unloaded and loaded chitosan‐LNP nanocomposites (Cs‐LNPs). The water‐swelling capacity of the nanocomposite gel was about 200%. The data indicated that the Cs‐LNP gels can be used as controlled release systems for releasing MAP fertilizer, with maximum releasing value observed for chitosan‐LNPT gel (65%). The kinetic of MAP release from the investigated nanocomposites was followed by the Ritger‐Peppas model with Fickian and quasi‐Fickian diffusion mechanisms. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Biodegradable all-cellulose composite hydrogel as eco-friendly and efficient coating material for slow-release MAP fertilizer

In the attempt to develop a novel coated fertilizer with combined slow release and water retention properties, all-cellulose hydrogel formulation was applied as waterborne and swellable coating material of monoammonium phosphate fertilizer (MAP). The biodegradable formulation was prepared from sodium carboxymethyl cellulose/hydroxyethyl cellulose blend filled with 5% of spherical regenerated cellulose particles (CH@5RC). The coating process was performed in rotating pan and final coated products with two coating thicknesses and two crosslinking conditions were elaborated. A uniformly covered surface with increased crushing resistance up to 90.55 N and a positive impact on the soil water retention capacity were obtained after coating. Furthermore, the release experiment of phosphorus and nitrogen in water and soil media showed extended-release durations with maximal longevities of 12 h in water and 19–20 days in soil as compared to 1–2 h in water and 9–10 days in soil of uncoated MAP. The effect of the coating thickness and crosslinking condition on all investigated properties was taken into account. We assume in this work that cellulosic materials, being the main coating former of fertilizer, are capable to double the release time of MAP fertilizer with better preservation of the soil moisture.

Mono-Ammonium Phosphate Fertilizer Modified by Cadmium: An Efficient and Recyclable Catalyst for 2,3-Dihydroquinazolin-4(1H)-One Derivatives Synthesis

The present work reports a simple procedure for the preparation of cadmium pyrophosphate (Cd2P2O7) from the modification of mono-ammonium phosphate (MAP) fertilizer by cadmium chloride (CdCl2). The obtained support has been characterized by microscopic and spectroscopic methods, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared spectroscopy (IR). The catalytic activity of Cd2P2O7 has been evaluated by its application for the first time as a heterogeneous catalyst in the 2,3-dihydroquinazolin-4(1H)-one derivatives synthesis. This synthesis has been realized through the condensation of anthranilamide with different aromatic aldehydes. The optimum reaction conditions have been determined by studying the effect of the catalysts amount, the solvent nature, and the temperature. The results show that Cd2P2O7 possesses a high catalytic efficiency because of the excellent yields and the short reaction times obtained for the studied reactions. Furthermore, it presents a remarkable capacity for recovery and reusability, and therefore its application contributes to the green chemistry development.

Formulation of anti-dust coating agent for monoammonium phosphate fertilizer using experimental design

Granular fertilizer production presents several kinds of problems. The caking phenomenon and moisture absorption are the critical ones that affect the physical quality of granules and make them unsuitable for their intended uses. Another frequent problem observed during granular fertilizers manufacturing, is the dust emission, which is generated during handling, storage and transport. The mechanical abrasion, chemical composition and storage conditions can be defined as the direct sources of this problem. For these reasons, the formulation of anti-dust coating compositions, capable of reducing the dust emission of monoammonium phosphate fertilizer, is the main goal of this study. To assess the usefulness of our perception, we used two types of experimental designs. First, we started with a mixture screening design, to select, from a list of five anti-dust coating components those that would further reduce the dust emission of the fertilizer. The second step was the application of a mixture design to formulate anti-dust coating compositions based on three components chosen by the screening design as the most effective ones. The mixture design results show that we were able to formulate several anti-dust coating compositions capable of reducing the dust emission of fertilizer granules by up to 29%, which has significantly improved their physical qualities.

Application method influences the oxidation rate of biologically and chemically produced elemental sulfur fertilizers

AbstractElemental sulfur (ES) is commonly used as a fertilizer S source but needs to be oxidized to sulfate to become plant‐available. We assessed how placement (surface applied or incorporated) affects the oxidation of ES fertilizers. The fertilizers included an ES powder, a suspension of biogenic ES particles, and three granular fertilizers: two ES–bentonite pastilles and one monoammonium phosphate fertilizer cogranulated with ES. The fertilizers were applied either on the surface (broadcast) or incorporated into two different soils in a column experiment, incubated at 25 °C. Prior to broadcasting, the granular fertilizers were dispersed in water for 48 h to simulate the effect of 30 to 40 mm of precipitation. The columns were leached weekly and the concentration of sulfates derived through ES oxidation was measured in the leachates. The half‐lives of oxidation for the ES powder were 76 and 111 d for the incorporation and broadcast applications, respectively. The diluted biological ES suspension showed faster oxidation (8 and 30 d for incorporated and broadcast), probably because of its smaller particle size. Unlike the ES particles, the ES oxidation rates of the granular fertilizers were higher for the broadcast application than when incorporated in soil, particularly when they dispersed easily. One type of ES pastille showed little dispersion and its estimated half‐life of oxidation was >1,000 d even when broadcast. Overall, the results show that ES oxidation depends on the degree of dispersion in the soil and that this is strongly affected by the fertilizer type and application method.

Long-term fate of fertilizer sulfate- and elemental S in co-granulated fertilizers

In previous studies, we assessed sulfur (S) uptake by crops from elemental S (ES) and sulfate-S (SO4-S) in S-fortified monoammonium phosphate fertilizers over two years. The recovery by the crop ranged from 16 to 28% for ES and from 9 to 86% for SO4-S. Here, we used a model which takes into account organic S cycling, SO4-S leaching and ES oxidation to explain the observed recoveries. Higher recoveries of ES than SO4-S in two of the four sites could be explained by partial leaching of SO4-S and relatively fast oxidation of ES, due to a warm climate and high S-oxidizing soils. The same model was used for longer-term (5-year) predictions, and a sensitivity analysis was carried out. The size of the labile soil S pool and total S uptake strongly affected the recovery of both SO4-S and ES. Predicted recoveries after 5 years were over threefold higher for a small than for a large labile organic S pool and for a high-uptake than for a low-uptake scenario. Leaching mainly affected SO4-S, with predicted recoveries halved under a high-leaching scenario. Slow oxidation resulted in recoveries in the first year being fourfold lower for ES than for SO4-S or even lower in case of a long lag-time. However, it is predicted that total recoveries of ES will eventually reach those of SO4-S or exceed them if there is SO4-S leaching. Our model demonstrates that long-term trials are needed to evaluate the true effectiveness of a slow-release fertilizer source such as ES.

Purified monoammonium phosphate fertilizer promotes the yield and reduces heavy metals accumulation in tomato (Lycopersicon esculentum L.)

Monoammonium phosphate is a commonly used fertilizer for better crop production. However, its repeated application causes the accumulation of harmful metals levels in plants and soil over time. Here, the impact of the purification of monoammonium phosphate fertilizer on vegetative growth and yield of tomato plants (Lycopersicon esculentum L.), and the heavy metals accumulation in both soil mix and tomato fruits was investigated through a pot experiment on three different concentrations of purified and unpurified monoammonium phosphate fertilizer. This study showed that the purification of monoammonium phosphate led to a significant enhancement on vegetative growth and yield attributes, mainly for 1 g/L of purified fertilizer. Importantly, the physicochemical investigations showed a significant reduction in heavy metals accumulation (Pb, Cr, Cd, Ni, and V) in the fruits and the soil mix treated with purified monoammonium phosphate. This study confirms that the use of purified monoammonium phosphate fertilizer improves the fruit yield and at the same time reduces the impact of toxicity of heavy metals present in the environment, which can be classified as a part of an environmental management systems.

Sulfur Uptake from Fertilizer Fortified with Sulfate and Elemental S in Three Contrasting Climatic Zones

Field trials with labeled fertilizers can be used to provide information on fertilizer efficiency, residual value, and nutrient fate. We assessed the uptake from elemental S (ES) and sulfate S (SO4-S) in S-fortified monoammonium phosphate fertilizers by various crops at three sites in Argentina, Brazil, and Canada. The S sources were labeled with 34S, and the 34S abundance in the plant tissue was analyzed at an early stage and at maturity over two consecutive years. At the sites in Argentina and Canada, the recovery of ES in the crop was smaller than that of SO4-S in the first year, while the opposite was true in the second year. At the Brazilian site, the recovery of ES was similar to that of SO4-S in the first year, but higher in the second year. In the Argentina and Canada sites, the cumulative recovery of SO4-S was >65% and that of ES was 20−25%. In the Brazilian site, the cumulative recovery of SO4-S was 9% and that of ES 16%. The higher recovery of ES than of SO4-S in the Brazilian site was attributed to leaching of added SO4-S and relatively fast oxidation of ES due to the warm climate. These results suggest that ES may be more suitable than SO4-S as a fertilizer S source in warm humid climates, while inclusion of SO4-S in the fertilizer is recommended in colder climates as slow oxidation limits the initial availability of ES.

Cadmium Content and Accumulation in Lettuce Grown on Different Types of Soil

This study was conducted on a pseudogley (pH 5.0) and a vertisol (pH 6.9) to analyze their total and available Cd levels and Cd accumulation by lettuce for risk assessment of potential human health impacts. Total Cd levels in both soil types were below maximum allowable concentrations, and showed a high dependence on soil pH (R=-0.974). Monoammonium phosphate (MAP) fertilizers containing various amounts of cadmium led to an increase in cadmium uptake, with higher concentrations accumulated in lettuce roots than in leaves. The transfer factor showed that Cd uptake from the pseudogley was much higher than from the vertisol, and its values indicated that lettuce is a cadmium hyperaccumulator. Lettuce head weight decreased with increasing cadmium rates and was highly negatively correlated with Cd concentration in the leaves (R=-0.818).

Quantitative Analysis of Total Nitrogen Content in Monoammonium Phosphate Fertilizer Using Visible-Near Infrared Spectroscopy and Least Squares Support Vector Machine

А quantitative analysis method to determine the total nitrogen content in monoammonium phosphate (MAP) fertilizer using visible-near infrared (Vis-NIR) spectroscopy and least squares support vector machine (LS-SVM) is proposed. Sample set partitioning based on the joint x–y distance (SPXY) was used to select the calibration set. Fourteen spectral pre-processing methods were then employed to deal with the spectral data including Savitzky–Golay (SG) smoothing, fi rst derivative (D1) and second derivative (D2) with SG smoothing, multiplicative scatter correction (MSC), standard normal variate (SNV), wavelet, and combination thereof. Next, the LS-SVM model with radial basis function kernel was established with the best pre-processing method, and its performance was compared with that of partial least squares (PLS) model. The results revealed LS-SVM calibration with the discrete wavelet transform provided the best prediction for total nitrogen content in MAP fertilizer, yielding R2, root mean square error of prediction (RMSEP), and ratio of performance to deviation (RPD) values of 0.91, 0.101, and 3.34, respectively.

Preparation of tin-modified mono-ammonium phosphate fertilizer and its application as heterogeneous catalyst in the benzimidazoles and benzothiazoles synthesis

This work presents an efficient, easy and green method for the benzimidazoles and benzothiazoles synthesis by a condensation reaction of 1,2-diamino benzene and 2-amino thiophenol with various aromatic aldehydes using SnP2O7 as a new heterogeneous catalyst. This catalyst was prepared by adding MAP to the solution of SnCl2 and characterized by microscopic and spectroscopic methods namely X-ray diffraction, scanning electron microscopy and infrared which proved that the chemical structure of MAP has been modified when SnCl2 was added leading to the formation of SnP2O7. On the other hand, the reaction conditions were optimized namely the nature of the solvent and the mass of the catalyst. The high yields (85–97%) and very short reaction times (5–40 min) obtained for various benzimidazoles and benzothiazoles derivatives synthesis show that the new catalyst is very interesting because of its good catalytic activity and its reusability for at least five cycles without any degradation of its activity.

Rye cover crop increases earthworm populations and reduces losses of broadcast, fall-applied, fertilizers in surface runoff

Corn (Zea mays L.) silage and soybean [Glycine max (L.) Merr.] rotations in the US Upper Midwest leave minimal amounts of surface residues, which can contribute to soil degradation, increased surface runoff, and reduced water quality. Planting cover crops after harvest can reduce these concerns, but their effectiveness in reducing nutrient losses in surface runoff shortly after fall planting and fertilization has not been thoroughly investigated. Therefore, we applied 65 mm of simulated rainfall in 60 min to five replicate, 1.5 by 3.0 m, field plots in a no-till, corn silage-soybean rotation into which a rye (Secale cereale L.) cover crop was planted for 14 consecutive years and to five replicate plots with no cover crop history. Natural slope of the plots ranged from 0.1 to 2.7%. The study was conducted in October 2014, about one month after corn silage harvest and rye planting and ∼1 h after broadcast application of monoammonium phosphate and potassium chloride fertilizers. The living rye cover crop significantly (P ≤ 0.05) delayed surface runoff by 5.7 min and decreased total runoff by 65% compared to plots with no cover crop. This resulted in a significant 68% reduction in sediment loss and even greater significant reductions in fertilizer nutrient losses (i.e., NH4-N - 86%; total P - 83%; total dissolved P - 84%; K - 91%). Earthworm population and biomass, measured using electrical extraction shortly after the rainfall simulations, were 1.2 and 1.4 times greater in cover crop plots than in no cover plots and 3.2 and 2.5 times greater the following spring. Our results suggested that a living cover crop and their long-term usage can contribute to improvements in soil structure and increased earthworm populations that can substantially reduce sediment and nutrient losses in surface runoff due to a severe storm shortly after post-harvest broadcast application of fertilizer.

Graphene oxide-Fe(III) composite containing phosphate – A novel slow release fertilizer for improved agriculture management

Abstract Novel materials offer opportunities to develop new types of fertilizers which could potentially increase efficiency of nutrient use in agriculture. Slow-release fertilizers can be more effective than traditional nutrient sources and simultaneously reduce negative impacts of nutrients to the environment. Using low-cost, abundant natural material, graphite rock, a functionalized graphene oxide (GO)/iron (GO-Fe) composite was synthetised and examined as a new carrier of phosphate ions in order to improve nutrient delivery to plants. The morphology of the composite was examined with scanning electron microscopy (SEM), and X-ray diffraction (XRD) was used to determine the presence of crystal phases. The composite was also characterised with thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). We found that the presence of ferric ions was responsible for attachment of phosphate ions onto the GO-Fe composite, providing a loading capacity of 48 mg P/g. The kinetics of P release were examined using a column perfusion test while P diffusion in three different types of soils was examined using a visualization technique and chemical analysis. Compared with commercial monoammonium phosphate (MAP) fertilizer, application of GO-Fe composite loaded with phosphate (GO-Fe-P) resulted in slower release of P, thus reducing the possibility for leaching or runoff of soluble P to surface and groundwaters.

Limited Dissolved Phosphorus Runoff Losses from Layered Double Hydroxide and Struvite Fertilizers in a Rainfall Simulation Study.

The enrichment of P in surface waters has been linked to P runoff from agricultural fields amended with fertilizers. Novel slow-release mineral fertilizers, such as struvite and P-exchanged layered double hydroxides (LDHs), have received increasing attention for P recycling from waste streams, and these fertilizers may potentially reduce the risk of runoff losses. Here, a rainfall simulation experiment was performed to evaluate P runoff associated with the application of recycled slow-release fertilizers relative to that of a soluble fertilizer. Monoammonium phosphate (MAP), struvite, and LDH granular fertilizers were broadcasted at equal total P doses on soil packed in trays (5% slope) and covered with perennial ryegrass ( L.). Four rainfall simulation events of 30 min were performed at 1, 5, 15, and 30 d after the fertilizer application. Runoff water from the trays was collected, filtered, and analyzed for dissolved P. For the MAP treatment, P runoff losses were high in the first two rain events and leveled off in later rain events. In total, 42% of the applied P in the MAP treatment was lost due to runoff. In the slow-release fertilizer treatments, P runoff losses were limited to 1.9 (struvite) and 2.4% (LDH) of the applied doses and were more similar over the different rain events. The use of these novel P fertilizer forms could be beneficial in areas with a high risk of surface water eutrophication and a history of intensive fertilization.

Fertilizer placement and tillage effects on phosphorus concentration in leachate from fine-textured soils

Adoption of no-tillage in agricultural watersheds has resulted in substantial reductions in sediment and particulate phosphorus (P) transport in surface runoff. No-tillage, however, may result in increased losses of dissolved P in tile-drained landscapes due to the accumulation of P in surface soil layers and prevalence of preferential flow pathways. The objective of this study was to examine the effect of fertilizer placement and tillage on P leaching in fine-textured soils following fertilizer application. Rainfall simulations (90 min; 3.8 cm rainfall depth) immediately following application of monoammonium phosphate fertilizer (75 kg P ha−1) were conducted on 9 m2 plots with pan lysimeters (0.6 m depth) in four agricultural fields located in northwestern Ohio, USA. Three fertilizer placement treatments that covered a range of soil disturbance and soil-fertilizer mixing (broadcasted, injected, and tilled) were replicated on each field. Stable water isotopes were used to separate leachate into preferential and matrix flow components. Results showed that leachate dissolved P concentration was significantly greater when fertilizer was surface broadcast on no-tilled plots (43.7 mg L−1) compared to when the fertilizer was either injected (14.9 mg L−1) or tilled (11.0 mg L−1) into the soil. Event water comprised between 6 and 46% (mean = 22%) of lysimeter leachate and did not vary among treatments. Similar event water contributions among treatments suggest that the disruption of the macropore network was not likely the main mechanism responsible for decreased P concentration in leachate, but rather increased soil-fertilizer contact and decreased interaction between the highly soluble fertilizer and ponded surface water were likely responsible for decreased P concentrations observed for the injected and tilled treatments compared to the broadcasted treatment. Findings indicate that subsurface injection of fertilizer has the potential to limit dissolved P leaching compared to surface broadcast applications and also minimize soil disturbance relative to tillage; thus, it should be considered a promising conservation practice to help meet water quality goals in tile-drained landscapes.