Relative Agronomic Efficiency Research Articles

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.

Phosphate solubilizing rhizobacteria inoculation to increase rock phosphates efficiency and improve maize growth

Rock phosphates are less soluble and agronomically not as efficient as the acidulated. However, some rhizobacteria can improve the solubilization of inorganic phosphates in the soil, raising the efficiency of the rock phosphates. The objective was to evaluate the development of maize plants in response to the application of soluble and rock P sources associated with rhizobacteria inoculation. A greenhouse experiment was carried out with six P sources: no P application; ​​Triple Superphosphate (TSPh); Gafsa rock phosphate (reactive); Itafós rock phosphate (non-reactive); TSPh + Gafsa; and TSPh + Itafós, and three inoculation forms: no inoculation, Burkholderia pickettii GN 2214 and Pseudomonas sp. fluorescens group P21. Plant height, stem diameter, leaf area, shoot dry weight (ShDW), root dry weight (RDW), total dry weight, cumulative P content in ShDW, RDW/ShDW ratio and relative agronomic efficiency were assessed. Agronomic efficiency and growth of the TSPh-treated plants were better than of those treated with rock phosphates. The association of TSPh with rock phosphates increases the agronomic efficiency and maize plant growth more than the isolated rock sources. Inoculation with P. fluorescens strain P21, improved the performance of maize fertilized with Gafsa phosphate, but had no effect when associated with Itafós phosphate. Together with TSPh, inoculation intensified shoot and root growth, indicating the potential to increase the efficiency of soluble sources as well.

Productivity and Agronomic Efficiency of Inundation Tolerance Rice in the Swampland: A Review

Swampland is one of the potential agroecosystems of rice production in Indonesia, but it is classified as marginal in terms of unpredictable inundation, primarily due to global climate change impact. Submergence-resistant variety’s high-yielding and efficient input are one of the efforts to overcome these constraints. The review aims to explore information on the availability and potentiality of immersion-resistant varieties, the efficiency of cultivation technology, and the availability and potentiality of local rice as a source of genes in creating immersion-resistant varieties. The review method is a reference study of different research results. The review results show that five varieties of swampland rice are mainly assembled to withstand immersion in all vegetative phases, namely for six days (Inpara 3) and fourteen days (Inpara 4-5, Inpari 29-30). Based on the Relative Agronomic Efficiency (RAE) parameter, cultivation technology is available. However, information on the research results and its implementation on these five varieties and other high-yielding rice varieties in the swampland is still limited. Sixteen local accessions of inundation tolerance have been identified. Further research is needed on different varieties of immersion resistance, RAE parameters-based cultivation technology, and new immersion-resistant varieties using available local varietal gene donors. This way the availability of effective technology and its dissemination efforts will have the opportunity to be adopted by the stakeholders, thus increasing their productivity and income.

Growth and yield respons of mungbean to different level of organic and inorganic fertilizer in North Sumatera

Integrated nutrient management is an alternative for the sustainable and cost-effective management of soil fertility by combined apply of organic with inorganic fertilizer resulting in rising soil fertility and productivity. This study aims (i) to determine the growth and yield respons of mungbean to different level of organic and inorganic fertilizer, and (ii) to measuring the effectiveness of organic fertilizer on mungbean production. The research was conducted at Pasar VI Kwala Mencirim Village, Sei Bingai District, Langkat Regency, North Sumatra in December 2020 to April 2021. This study used a Non-Factorial Randomize Complete Block design consisting of seven treatments and four replications, namely P0 (without fertilizer), P1 (100% dose of NPK fertilizer), P2 (75% dose of NPK fertilizer), P3 (50% dose of organic fertilizer + 75% NPK fertilizer) P4 (100% dose of organic fertilizer + 75% NPK fertilizer), P5 (150% dose of organic fertilizer + 75% NPK fertilizer), and P6 (1 dose of organic fertilizer + 100% NPK fertilizer). Plant height observations were carried out at 4, 6, and 8 weeks after planting and production observations were at harvest. Analysis of varian (ANOVA) was used to determined the effect of fertilizers treatment and followed by Duncan Multiple Range Test (DMRT) at 5% confidence interval for significant differences between treatment on plant growth and production. Organic fertilizer effectiveness was calculating using the Relative Agronomy Effectiveness (RAE). The results showed that organic fertilizer had a significant effect on mungbean growth and yield compared to controls. The highest mungbean production in P6 treatment of 1209 Kg/ha while the control treatment was 512 Kg/ha. Organic fertilizer was effective to increase mungbean production. The highest relative agronomic efficiency (RAE) was 438% in the treatment of organic fertilizer fertilizer at P6 of 100% dose of organic fertilizer +100% NPK fertilizer

A phospho-compost biological-based approach increases phosphate rock agronomic efficiency in faba bean as compared to chemical and physical treatments.

Under arid and semi-arid conditions, direct application of phosphate rock (PR) as a source of phosphorus (P) for crop production is likely influenced by agricultural practices and soil properties. Different approaches could be used to improve the agronomic efficiency of low-grade PR over a wider range of soils and crops. In this study, biological, physical, and chemical treatments of low-grade Moroccan PR were investigated and compared through agronomic trials on faba bean grown under alkaline soil conditions. The physical treatment was based on blending PR with triple superphosphate (TSP) at 75:25 and 50:50 ratios, the biological treatments involved co-application of PR with compost at 50:50 ratio and phospho-compost elaborated from PR (20%), sewage sludge (46%), and wheat residues (34%), while the chemical treatment was obtained by a 30% acidulation of PR by phosphoric acid. Control treatments consisting of zero P application (control), PR alone, and TSP alone were considered to assess the effectiveness of the abovementioned techniques to improve PR agronomic efficiency. A pot experiment was conducted in sandy soil (Jorf Lasfar, central Morocco) for 60 days in a completely randomized design considering eight treatments. All treatments, except the control, were amended with 52 mg kg-1 of P from different PR-based fertilizers before sowing. At the flowering stage (60-day-old plants), results indicated that all PR treatments significantly improved plant growth, root nodulation, and nutrient uptake compared to the control. The relative agronomic efficiency of pretreated PR was significantly higher with phospho-compost treatment (86%) than the partially acidulated PR (78%) or the PR/TSP blend 50:50 (64%). Likewise, P uptake, P use efficiency, number of root nodules, and N uptake all were improved under PR treatments. Our finding revealed that the biological technique based on phospho-compost yielded better compared to chemical and physical treatments.

Bio-activation of waste mica through potassium solubilizing bacteria and rice residue

This article aims to demonstrate the increase in availability of potassium (K) from mica through bio-activation using different strains of potassium solubilizing bacteria (KSB) and rice residue incorporation and comparing it with standard K-fertilizer i.e. muriate of potash (MOP). The effects of mica, rice residue and KSB on wheat biomass yield, K uptake and available K in soil were assessed through a pot culture study at research farm of ICAR-Indian Agricultural Research Institute, New Delhi (2019). Results reveal that mica application @ 50 and 100 mg/kg soil significantly improved the biomass yield and K uptake by wheat as compared to treatments without mica application. Rice residue incorporation @ 2 g/kg soil had significant role in improvement of biomass yield, K uptake by wheat and available K in soil as compared to no residue treatments. Amongst the two isolated strains of KSB (JHKSB1 and JHKSB4) and one standard strain (Bacillus sp.), all were found equally effective in improving K availability from mica to the wheat crop. Mica, bio-activated via rice residue and KSB was able to improve relative agronomic efficiency and per cent K recovery from soil but it was not as effective as MOP. Thus, inherent K content in mica may be available to crops partly after bio-activation and it can be applied in conjunction with MOP for meeting the K requirement of the crop.

Effect of Silicon Nutrition on Yield, Uptake and Agronomic Efficiency of Paddy in Acid Lateritic Soils of Odisha

A field experiment was conducted in the central farm, Regional Research and Technology Transfer Station, Coastal Zone OUAT, Bhubaneswar during kharif 2020 using cv-Lalat variety of Rice. The experiment was laid out in randomized block design (RBD) with ten treatments and three replications. In this experiment BOF (Basic Oxygen Furnace) slag was used as a source of silica for application to rice crop. 200, 300 and 400 kg SiO2/ha was applied in combination with 50% STD and 75% STD in order to assess the efficacy of Silica with reduction in fertilizer dose by 50% and 25%. It was shown in case of grain yield, straw yield, and harvest index, 100% STD (T4) registered maximum (36.9q/ha) grain yield which was 29.4% more than that of control. Of course, grain yield in case of T9i.e., 75% STD+300kg SiO2/ha was at par 36.2q/ha indicated efficacy of silica application by reducing fertilizer dose. Harvest index was not significantly affected by Si treatments. However, maximum HI (0.478) was observed in T9. Available N, P, K and S status in post-harvest soil was increased significantly due to application of silica along with fertilizer over control indicated better availability of nutrients which plays a vital role in increasing production and productivity of rice. The content and uptake of N, P, K and Si was significantly increased over control due to application of silica with fertilizer. Though 100% STD (T4) was found to be very effective as compared to other treatments but 75% STD+300kgSiO2/ha was also equally effective so far as yield, yield attributing characters, available nutrient status, N, P, K and Si content and uptake along with Relative Agronomic Efficiency (RAE), Agronomic Efficiency (AE), Apparent Recovery (%) AR and Production Efficiency (PE) are concerned.

Closing global P cycles: The effect of dewatered fish sludge and manure solids as P fertiliser.

The aim of this study was to contribute to closing global phosphorus (P) cycles by investigating and explaining the effect of fish sludge (feed residues and faeces of farmed fish) and manure solids as P fertiliser. Phosphorus quality in 14 filtered and/or dried, composted, separated or pyrolysed products based on fish sludge or cattle or swine manure was studied by sequential chemical fractionation and in two two-year growth trials, a pot experiment with barley (Hordeum vulgare) and a field experiment with spring wheat (Triticum aestivum). In fish sludge, P was mainly solubilised in the HCl fraction (66±10%), commonly being associated with slowly soluble calcium phosphates, and mean relative agronomic efficiency (RAE) of fish sludge products during the first year of the pot experiment was only 47±24%. Low immediate P availability was not compensated for during the second year. Thus efforts are needed to optimise the P effects if fish sludge is to be transformed from a waste into a valuable fertiliser. In manure solids, P was mainly soluble in H2O and 0.5M NaHCO3 (72±14%), commonly being associated with plant-available P, and mean RAE during the first year of the pot experiment was 77±19%. Biochars based on fish sludge or manure had low concentrations of soluble P and low P fertilisation effects, confirming that treatment processes other than pyrolysis should be chosen for P-rich waste resources to allow efficient P recycling. The field experiment supported the results of the pot experiment, but provided little additional information.

Combined effect of rock phosphate with single super phosphate on yield and phosphorus use efficiency under maize-groundnut cropping sequence in Alfisols of Odisha

Aim: The present study was conducted to investigate the effect of combined application of rock phosphate with water soluble phosphorus fertilizers on its efficiency in relation to soil and crop production. Methodology: Rock phosphate and single super phosphate were used as supplemental source of phosphorus and applied in variable combinations at graded doses, with maize and groundnut as test crop. Lime was applied in combination with 100% SSP to analyse its effect. The composite surface (0-15 cm) soil samples were collected at critical growth stages of maize and groundnut and further analyzed for different physical and physico-chemical characteristics. The plant samples were collected from each treatment at harvest stage for nutrient analyses. Results: Application of rock Phosphate increased the available phosphorus in soil. The combined treatment significantly influenced the yield attributes and nutrient uptake of both maize and groundnut crops. Among the combination, equal proportion of soluble single super phosphate and insoluble rock phosphate source of P outreached the other combination ratios. The highest agronomic phosphorus use efficiency and relative agronomic efficiency of the cropping sequence was obtained with the combined treatment of Single super phosphate along with lime. Interpretation: Combination of rock phosphate which has been reported to be farmer’s pocket friendly along with single super phosphate under acid soil conditions holds the potential to produce better results as compared to use of lone conventional water soluble phosphatic fertilizer like single super phosphate.

Predicting relative agronomic efficiency of phosphorus-rich organic residues

Relative agronomic efficiency (RAE) of phosphorus (P) in nutrient-rich residues with different chemical characteristics must be known in order to optimize their use as fertilizers, to avoid underfertilization of crops or eutrophication of surface waters due to overfertilization. In this study, we determined the chemical characteristics and RAE of manures (cattle, pig, fox) and sewage sludges subjected to different treatments (anaerobic digestion, composting, lime stabilization, thermal hydrolyzation, pyrolyzation, hydrothermal carbonization (HTC)) by growing barley (Hordeum vulgare, var. Elmeri) to maturity in three independent growth trials. All manures had high RAE (up to 189% in pig slurry), while RAE was only 6–17% for digested and composted sewage sludges when precipitation with Fe used for P removal from wastewater. Pyrolyzation and HTC further depressed RAE to 1–6%. Alternative wastewater treatment processes are therefore needed to increase P recycling potential. For cattle and pig manures and anaerobically digested or composted sewage sludges, molar ratio of (Fe + Al)/P, varying from 0.08 to 2.69, was the best predictor of RAE (R2 = 0.99), with negative correlations with grain yield. Sources in which calcium was more influential for P solubility (fox manure and lime-stabilized sewage sludge) and pyrolyzed and HTC-treated residues did not follow this trend. Conventional extraction methods (2% formic acid, 2% citric acid, neutral ammonium citrate, water and 0.5 M NaHCO3) either underestimated or overestimated RAE of P-rich organic residues, depending on their chemical characteristics.

Solubility and Efficiency of Rock Phosphate Fertilizers Partially Acidulated with Zeolite and Pillared Clay as Additives

Soluble phosphates are the most common sources currently used in crop production in tropical soils; however, they present low efficiency and are more expensive than natural rock phosphates. The objective was to develop new phosphate fertilizers with slow solubility through the partial acidification of rock phosphates (RPs), incorporating materials with adsorption characteristics to favor slow dissolution and prevent phosphorus (P) fixation in the soil. Three rock phosphates, Araxá (ARP), Bayovar (BRP) and Morocco (MRP), were evaluated at two acidulation levels (25 and 50% Ac.) and two additives; pillared clays (PILC) and zeolites (Zeo), plus triple superphosphate (TSP) and a control (nil-P). The soil diffusion was evaluated in concentric rings in Petri dishes. Solubility was evaluated in leaching columns and sampled in layers from surface for P forms in the soil profile. The relative agronomic efficiency (RAE) was evaluated in maize. Greater diffusion was provided by TSP, followed by BRP and MRP both with 50% Ac. + Zeo, and MRP with 50% Ac. + PILC. Percolated P was more pronounced under TSP, followed by RPs (BRP and MRP) with 50% Ac. + Zeo. BRP and MRP + 50% Ac. were the most promising sources with RAE above 74% compared to TSP.

Effect of Udaipur Rock Phosphate, Single Super Phosphate and Their Combinations on Yield and Total Nutrient Uptake by a Groundnut-Maize Cropping System on the Acid Alfisols of Odisha State, India

To find out the effect of low grade Udaipur rock phosphate on yield and nutrient dynamic in groundnut- maize cropping system, a field experiment was conducted in a randomized block design with three replications and eight treatments consisting of Udaipur rock phosphate (URP), single super phosphate (SSP) alone or in combinations with different ratios including phosphorus control from 2013-14 to 2015. The soil has a loam texture, a pH of 5.18, low available nitrogen and medium phosphorus and potassium. The highest maize equivalent yield of 6293 kg ha-1 and relative agronomic efficiency (RAE) of 159% was recorded in SSP+ lime (0.2LR) treatment followed by URP+SSP (1:1). Combined application of SSP+ lime recorded higher P, Ca, Mg and S uptake by groundnut-maize cropping system. When the crops received URP+SSP mixture in 1:1 ratio, the RAE values were increased above the standard SSP treatment (T3) being 102% for groundnut, 105% for maize and 103% for groundnut-maize cropping system. The yield in URP+SSP mixture (1:1) was higher than for the SSP treatment, but the difference was not statistically significant (P > 0.05). Thus, combined application of URP+SSP mixture (1:1) can safely be recommended in acid soils for short duration crops like maize and groundnut as against the more costly water soluble SSP fertilizer.

Does inoculation with Rhizobium tropici and nitrogen fertilization increase chickpea production?

ABSTRACT Studies related to nitrogen fertilization and biological nitrogen fixation in the increase of chickpea production are considered scarce in tropical regions. This work aimed to evaluate the inoculation with Rhizobium tropici, and nitrogen fertilization, under irrigated tropical conditions, on the development of chickpea in low and high content of soil organic matter (SOM). The experimental design was in randomized blocks, with four replications, in a 2 x 6 factorial scheme. Treatments, consisted of the presence and absence of inoculation with R. tropici, and six N doses (0, 25, 50, 75, 100, and 125 kg ha-1) in the form of urea. The study was divided into two areas with distinct contents of SOM. In the area with the lowest content of SOM (3.55 dag kg-1), the inoculation with R. tropici or the fertilization with 125 kg ha-1 N increased the leaf content of nutrients (N, K, Mg, and P) and grain mass per plant, 100-grain mass, number of pods with two grains, dry mass of leaves, branches, chlorophyll index, and relative agronomic efficiency. Thus, the yield was increased in 65%, compared to the control treatment, recommending the application of 100 to 125 kg ha-1 of N with or without R. tropici. In the area with the highest content of SOM (7.37 dag kg-1), the inoculation with R. tropici provided a higher grain mass per plants, number of pods with one gain, dry mass of leaves, total dry mass, and chlorophyll index; nitrogen fertilization increased the leaf content of N and the chlorophyll index, although neither factor interfered with the yield, and are not recommended. Such results indicate the dependence of the nitrogen fertilization and inoculation with Rhizobium on the natural availability of N in the SOM.

Evaluation of Indian rock phosphates for predicting agronomic potential through chemical and biological methods

ABSTRACTThe chemical reactivity of Indian rock phosphates (RPs) was measured by five chemical extraction methods (i.e. water, neutral ammonium citrate (NCA), 2% citric acid (CA), 2% formic acid (FA) and absolute citrate solubility (ACS)). These measurements were assessed by agronomic response data obtained by growing ryegrass and palmarosa in two highly weathered acidic soils under pot culture experiment. The phosphorus (P) solubility value of RP measured by different methods followed the order: ACS > 2% CA > 2% FA > NAC > water. Considering triple superphosphate (TSP) as a standard reference P fertilizer, the agronomic response of RPs followed the order Udaipur RP > Jhabua RP ≥ Purulia RP > Mussorie RP. Methods based on citrate solubility (i.e. NAC, 2% CA and ACS) were significantly and positively correlated with agronomic response irrespective of the plant species and soil types. The best correlation value obtained with NCA indicated that P solubility in NAC solution may offer better prediction of agronomic effectiveness of RP in terms of biomass yield, relative agronomic efficiency (RAE) and P recovery efficiency. So, the present investigation will help to predict the agronomic effectiveness of low-grade RP based on chemical methods.

Agronomic efficiency of selected phosphorus fertilisers derived from secondary raw materials for European agriculture. A meta-analysis

Phosphorus (P) is a macronutrient essential for all living organisms. Food production has become highly dependent on mineral P-fertilisers derived from phosphate rock, a non-renewable and finite resource. Based on supply risk and economic importance for the European Union, phosphate rock and elemental P have been identified as critical raw materials. Moreover, P dissipation can lead to adverse impacts on the aquatic environment. The production and use of P-fertilisers derived from secondary raw materials could possibly contribute to a more sustainable agriculture in line with a circular economy. Biogenic and industrial resources and waste streams can be converted into value added materials, such as precipitated phosphate salts, thermal oxidation materials and derivates, and pyrolysis and gasification materials. A condition is, however, that the P must be recovered in a plant-available form and that the recovered P-fertiliser supports plant growth and nutrient uptake in European agroecosystems. Here, we review the agronomic efficiency of selected P-fertilisers derived from secondary raw materials by comparing plant responses relative to those after mined and synthetic P-fertiliser application in settings relevant for European agriculture, using meta-analyses. The major points are the following: (1) precipitated phosphate salts show similar agronomic efficiency to mined and synthetic P-fertilisers, with results that are consistent and generalisable across soil and crop types relevant for European agriculture; (2) thermal oxidation materials and derivates can deliver an effective alternative for mined and synthetic P-fertilisers, but the relative agronomic efficiency is dependent on the feedstock applied, possible post-combustion manufacturing processes, and the length of the plant growing season; (3) the agronomic efficiency of pyrolysis and gasification materials remains indeterminate due to a lack of available data for European settings. It is concluded that the agronomic efficiency of selected P-fertilisers derived from secondary raw materials supports their use in conventional and organic European agricultural sectors.

Composts Produced From Pig Slurry Solids: Nutrient Efficiency and N-Leaching Risks in Amended Soils

Composts were prepared from the solid fraction of pig slurry (SPS) by mixing with cotton gin waste (CGW) in two different proportions. The aim was to assess the fertilizer value of the two composts and to evaluate potential pollution risks due to the heavy metal (Cu and Zn) concentrations in the composts and the nitrate leaching following their soil application. For this, a pot trial using Italian ryegrass (Lolium multiflorum Lam.) as a test plant was run in a glasshouse. Two composts, A and B, prepared with SPS:CGW ratios of 4:3 and 3:4 (v:v), respectively (OM 63 and 57 %, TN 36.1 and 32.7, and TP 15.3 and 10.8 g kg-1 in A and B, respectively), were applied to a sandy loam soil at two doses based on the N supplied (D1: 360 mg TN pot-1, equivalent to 52 kg N ha-1, and D2: 720 mg TN pot-1). They were compared with a soluble mineral fertilizer (3.62 g pot-1 of N:P:K 10:10:10; providing 360 mg N pot-1); unfertilized control soil was also tested. The potential risk of nitrate-N leaching in the soil after two simulated intense rainfall events was evaluated. The experiment was carried out in double-layer pots, which allowed the collection of leachates. Both composts were able to increase plant biomass production and soil TN and available-P with respect to the control; available Cu and Zn in the soil did not increase significantly with respect to the control soil and mineral fertilizer treatment, although N deficiency limited plant growth at harvests 2 and 3. The compost prepared with a higher proportion of SPS (A) was more efficient for N fertilization (relative agronomic efficiency: 38.1-47.6 %; nitrogen use efficiency: 34.1-41.9 % of TN), due to its greater inorganic-N concentration. To obtain high P and K efficiencies application rates based on compost TN are recommended, which also prevent Cu and Zn soil enrichment. Nitrate leaching was very low in all treatments (<0.5 % of TN applied). Therefore, both composts can be used as organic fertilizers in the partial substitution of mineral fertilizers, without a significant nitrate leaching risk.

Recycling potential of secondary phosphorus resources as assessed by integrating substance flow analysis and plant-availability

The plant-availability of phosphorus (P) plays a central role in the ability of secondary P resources to replace mineral fertilizer. This is because secondary P plant-availability varies, often with large fractions of residual P that has no immediate fertilization effect. Therefore, if low quality secondary P fertilizers are applied, they will accumulate in soils that, in the long run, may increase the risk of P runoff and eutrophication. Substance flow analyses (SFA), used to identify potentials for improved P management, have not considered this well-known quality barrier. We, therefore, argue that traditional SFA over-estimates the fertilizer potential of secondary P resources. Using Norway as a case, we present a plant-availability extended SFA methodology that integrates SFA and the concept of relative agronomic efficiency. To account for the plant-available soil P stock and long-term soil interactions, we adjust the Norwegian P fertilization demand based on soil P values. We found that, while the method has uncertainties particularly for long-term estimations, it more realistically estimates secondary P fertilizer potentials and is adaptable to other countries. For Norway, we found the overall secondary P fertilizer potential reduced by 6–55% when considering plant-availability. The most important secondary resource was manure, which had the highest P plant-availability and quantities large enough (10.9kt plant-available P/yr) to meet Norway's entire P fertilization demand (5.8kt plant-available P/yr). However, barriers related to its transportability need to be overcome to efficiently use this resource. Fish sludge was also an important product, with 6.1kt plant-available P/yr but with uncertain plant-availability data. We argue that high quality secondary P resources can theoretically meet Norway's P fertilization demand and, therefore, make Norway mineral P independent. However, it is important that their use is carefully regulated based on plant-availability to eliminate the soil accumulation of both available and residual P.

Drivers of Phosphorus Uptake by Barley Following Secondary Resource Application.

Minable rock phosphate is a finite resource. Replacing mineral phosphorus (P) fertilizer with P-rich secondary resources is one way to manage P more efficiently, but the importance of physicochemical and microbial soil processes induced by secondary resources for plant P uptake is still poorly understood. Using radioactive-labeling techniques, the fertilization effects of dairy manure, fish sludge, meat bone meal, and wood ash were studied as P uptake by barley after 44 days and compared with those of water-soluble mineral P (MinP) and an unfertilized control (NoP) in a pot experiment with an agricultural soil containing little available P at two soil pH levels, approximately pH 5.3 (unlimed soil) and pH 6.2 (limed soil). In a parallel incubation experiment, the effects of the secondary resources on physicochemical and microbial soil processes were studied. The results showed that the relative agronomic efficiency compared with MinP decreased in the order: manure ≥fish sludge ≥wood ash ≥meat bone meal. The solubility of inorganic P in secondary resources was the main driver for P uptake by barley (Hordeum vulgare). The effects of secondary resources on physicochemical and microbial soil processes were of little overall importance. Application of organic carbon with manure resulted in microbial P immobilization and decreased uptake by barley of P derived from the soil. On both soils, P uptake by barley was best explained by a positive linear relationship with the H2O + NaHCO3-soluble inorganic P fraction in fertilizers or by a linear negative relationship with the HCl-soluble inorganic P fraction in fertilizers.

PHYTOAVAILABILITY OF COPPER IN INDUSTRIAL BY-PRODUCTS AND MINERAL FERTILIZERS

Alternative copper (Cu) sources could be used in fertilizer production, although the bioavailability of copper in these materials is unknown. The objective of this study was to evaluate the extractants neutral ammonium citrate (NAC), 2 % citric acid, 1 % acetic acid, 10 % HCl, 10 % H2SO4, buffer solution pH 6.0, DTPA, EDTA, water, and hot water in the quantification of available Cu content in several sources, relating them to the relative agronomic efficiency (RAE) of wheat grown in a clayey Latossolo Vermelho eutrófico (Oxisol) and Neossolo Quartzarênico (Typic Quartzipsamment). Copper was applied at the rate of 1.5 mg kg-1 as scrap slag, brass slag, Cu ore, granulated copper, and copper sulfate. The extractants 10 % HCl, 10 % H2SO4, and NAC extracted higher Cu concentrations. The RAE values of brass slag and Cu ore were similar to or higher than those of Cu sulfate and granulated Cu. Solubility in the 2nd NAC extractant, officially required for mineral fertilizers with Cu, was lower than 60 % for the scrap slag, Cu ore, and granulated copper sources. This fact indicates that adoption of the NAC extractant may be ineffective for industrial by-products, although no extractant was more efficient in predicting Cu availability for wheat fertilized with the Cu sources tested.

Alternative Potash Fertilizer Source for Millet Crop

Millet is a grass that responds to potassium fertilization and Alfa 01 and Alfa 02 are potential sources of this nutrient. Thus, the aim of this study was to evaluate the potential of as potassium sources by measuring accumulation of this nutrient in millet. The crop was grown in Ustoxic Quartzipsamment (RQo) soil. The experiment was set up in randomized blocks with three repetitions. The treatments consisting of three sources (KCl, Alfa 02, Alfa 01), two rates (200 and 400 kg ha−1 K2O) and with no K fertilization (control). Potassium chloride was used as the standard to which the other sources of potassium were compared. Two consecutive crops of millet were grown in the same pots. The first crop received potassium source application but not the second. At the end of experiment, shoot dry matter production, shoot potassium concentration, shoot accumulated potassium, soil potassium and relative agronomic efficiency were determined. The relative agronomic efficiency, calculated from crops, was 100% for KCl, was 84% for Alfa 02 and was 11% for Alfa 01. In the shoot dry matter production and accumulated potassium only Alfa 01 was not statistically different of control. Millet absorbed potassium from the Alfa 02 source in both the first and second crops.