Fertilizer Reports

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Beneficial Organisms for Nutrient Uptake
(2014-01) Bindraban, Prem S.; Nina Koele; Thomas W. Kuyper
Phosphorus (P) availability is a major global limiting factor in crop production. The global input of mineral P fertilizer in food production is significant, but its efficiency is low, with only approximately 20% of applied P being converted into consumed P in food. Moreover, excessive application of P can lead to its accumulation in soils. As P resources are finite, maximizing their efficient use and stimulating the uptake of newly applied P fertilizers is crucial. This study investigates the hypothesis that enhancing early plant growth can improve plant P uptake, regardless of soil P levels. Experiments demonstrate that the recovery of mineral P fertilizer by crops is generally low, often less than 30%. Much of the applied fertilizer becomes bound to the soil complex, rendering it unavailable for plant uptake. Soil chemical processes produce very low P concentrations in the soil solution, whereas root concentrations are significantly higher. P deficiency in soils produces low crop yields, particularly in developing countries. To address this, the P concentration in the soil solution must be increased, or plants should possess enhanced abilities to extract P from the soil complex. Increasing P availability in soils requires substantial P application over several years, exceeding the crop's yearly uptake. Soil "loading" with P can occur unintentionally in regions with nutrient surpluses, such as areas with concentrated livestock production. These fertile soils contain excessive amounts of P compared to the crop's annual uptake. Similarly, less fertile soils have lower total P content but also lower crop off-take. In both cases, soil P reserves are abundant and could sustain agricultural production for many years if made available to the crop. This study emphasizes the importance of enhancing early plant growth to improve P uptake efficiency and utilize indigenous soil resources effectively. By increasing our understanding of plant-soil interactions and developing strategies to optimize P availability and uptake, we can enhance agricultural productivity while minimizing the environmental impact of excessive P application.
Beyond N and P: Toward a Land Resource Ecology Perspective and Impactful Fertilizer Interventions in Sub-Saharan Africa
(2015-01) Bindraban, Prem S. ; Roelf L. Voortman
Crop plants require essential nutrients from the soil in specific quantities and proportions for optimal growth and yield. Inadequate nutrient availability can lead to poor crop performance. While soil may contain sufficient nutrients, it may not be readily accessible to plants. In such cases, plants employ nutrient acquisition mechanisms like root exudation or mutualistic interactions with soil biota. However, there are instances where one or more nutrients still need to be improved, necessitating fertilizer application to achieve significant yield improvements. This report focuses on the potential of impactful fertilizer interventions that result in substantial yield increases at low doses, making them more affordable for small-scale farmers in sub-Saharan Africa. It highlights the importance of considering a broader spectrum of essential plant nutrients beyond nitrogen and phosphorus, as these could be limiting factors in tropical soils. The research conducted in Africa has primarily concentrated on nitrogen and phosphorus fertilizers, despite evidence suggesting deficiencies in other essential nutrients. The paper examines the variability of crop yield responses to nitrogen and phosphorus fertilizers and emphasizes the need for site-specific fertilizer applications considering nutrient dose and composition. It presents case studies conducted in the Miombo woodland biome, a prevalent vegetation type in Central-South Africa, to assess soil fertility and key soil chemistry factors influencing nutrient deficiencies. These case studies explore the impact of essential nutrients like calcium, potassium, magnesium, sulfur, and micronutrients (boron, copper, iron, manganese, molybdenum, nickel, and zinc) on crop yield. The report acknowledges the scarcity of comprehensive data and statistical analysis on combined nutrient impacts under prevailing soil and climatic conditions. However, it utilizes available data sets from selected case studies to gain insights into nutrient deficiencies beyond nitrogen and phosphorus. The findings emphasize the importance of addressing critical nutrient deficiencies and developing tailored fertilizer technologies specific to the Miombo biome and sub-Saharan Africa as a whole. Furthermore, the report compares soil fertility data from the Miombo biome with the Brazilian Cerrado, highlighting similarities and differences. It discusses the success of agricultural productivity advancements in Brazil and suggests a similar research approach for sub-Saharan Africa to identify nutrient deficiencies and develop appropriate fertilizer technologies.
Biochemical Nutrient Pathways in Plants Applied as Foliar Spray: Phosphorus and Iron
(2013-01) Bindraban, Prem S.; Renu Pandey; Vengavasi Krishnapriya
In plants, the roots are traditionally the primary site for water and inorganic nutrient absorption from the soil. However, recent research has shown that foliage, including leaves, stems, inflorescence, and fruits, can also affect nutrient uptake. This study aims to review the general pathways of foliar nutrient absorption and investigate the specific mechanisms involved in the penetration, absorption, and translocation of phosphorus (P) and iron (Fe) into various cell organelles. The physico-chemical properties of the spray formulation used for foliar application, such as pH, surface tension, polarity, spreading, and fluid retention, influence the efficacy of nutrient uptake. Additionally, the molecular size, ionic charge, and solubility of nutrient elements in the spray fluid, along with environmental factors such as relative humidity, temperature, light, and wind, affect the rate of foliar uptake. Plant-related factors like phenological stage, leaf morphology (shape, presence of hairs, stomatal characteristics), leaf surface architecture, chemistry, and nutrient mobility within the plant also contribute to foliar nutrient uptake efficiency. Soil fertilization of P and Fe is often limited by their low bioavailability, primarily influenced by soil pH. Slow diffusion and P fixation in soil result in limited availability of P, with plants absorbing only 10-20% of applied P during the growing season. Similarly, Fe availability is reduced at higher pH levels, and its deficiency is more pronounced in growing plant tissues. Foliar application of nutrients can effectively address the low bioavailability of P and Fe in soil and provide immediate relief from nutrient stress. Although foliar application cannot completely replace soil fertilization, it can enhance plant growth. This paper reviews and synthesizes existing literature on the pathways of foliar nutrient absorption and explores the biochemical processes involved in P and Fe penetration, absorption, and translocation within plant cells. Understanding these processes can aid in identifying effective nutrient compositions and developing advanced foliar fertilizers. The findings contribute to the knowledge of foliar nutrient uptake mechanisms and support the development of sustainable agricultural practices.
Digital Mapping of Soil Nutrients for the Republics of Burundi and Rwanda
(2015) Bindraban, Prem S. ; María Ruipérez González ; Kempen Bas ; Sandra Wolters; Cyrille Hicintuka; Zacharie Nzohabonayo; Wendt John ; Oscar Nduwimana; John Veerkamp
Lack of awareness about soil fertility constraints is a major limitation to developing sound liming and fertilizer recommendations in sub-Saharan Africa. Detailed maps of soil nutrient concentrations and soil acidity can help to identify areas with soil fertility constraints. For this purpose, maps of primary (P, K), secondary (Ca, Mg, S) and micronutrients (Cu, Zn, B), as well as pH, soil acidity (Al+H), effective CEC and organic matter were generated for the 0-20 cm soil layer by means of digital soil mapping using random forest models at a 250 m spatial resolution for Burundi and Rwanda. The models explained between 20% and 45% of the variation in the data.
Effect of Micronutrient Micnobit and Salt Fertilization on Lettuce
(2016-01) Bindraban, Prem S.; Christian O. Dimkpa; Jongschaap, R.E.E.; Vos, C.H.; Van der Lee, M.K.; Van der Werf, A.K.; De Visser, W.; M. Blom-Zandstra
Plants can absorb nano- and micro-size particles containing nutrients, opening the possibility for instantaneous uptake of nutrients supplied through roots or leaves. Here, we studied the uptake by lettuce (Lactuca sativa L.) of particulate nutrients from a micnobit (mixture of nanoparticles producing different nano and micro-scale sizes) formulation composed of ZnO, CuO, Fe3O4, MnO, and B2O3 used as fertilizers, in comparison to a similar mixture of their ionic equivalents from salts of Zn, Cu, Fe, Mn and boric acid at levels optimal for growth, yield, metabolism and nutritional quality attributes in food crops. In the case of Zn, the effect of a double dose compared to the basic fertilization was also studied to evaluate the possibility of increasing Zn levels in vegetable crops, as a potential strategy for alleviating Zn deficiency in human/animal diets. A greenhouse pot experiment was conducted using a sandy soil (pH 7.1) poor in most nutrients, including micronutrients but rich in calcium, and with very low content of organic matter to study the effects of micronutrient fertilization on lettuce. For application of the micronutrients, four fertilizer treatments were used: i) traditional (ionic) fertilizer; ii) micnobit particle coated seeds, iii) micnobit foliar application (spraying treatment), and iv) micnobit soil application. The lettuce plants were grown for 73 days and harvested periodically to study fresh and dry weight production and leaf greenness by SPAD measurements over time. Shoot or root materials from the final harvest was used to determine contents of micronutriënts, leaf chlorophyll and biomolecules (vitamins, flavonoids, phenolics, and antioxidants). Values from SPAD measurements significantly differed between the harvests and showed an increase with time up to 59 days after sowing. Differences between the treatments were less distinct, but showed the highest values between the Priming and Control treatments. Chlorophyll contents did not significantly differ between the treatments. The lettuce plants showed S-shaped growth under all treatments, although the foliar applications, both with micnobits and ions, caused necrosis at the leaf edges in the long run. Also, Foliar application with micnobits caused deposition and showed black spots on the leaves that could not be removed by rinsing methods described in the literature. Growth analysis, i.e. production of fresh weight, dry weight and root-total weight ratio over time, showed that for both shoot and root, the Control treatment resulted in the best growth. Priming of seeds resulted in similar growth as at the Control treatment. Addition of micronutrients to soil or leaves, both applied as ions or as micnobits, even decreased fresh weight and dry weight production of lettuce. Moreover, the shoots and roots of plants in the Control treatment also showed accumulation of micronutrients, while no micronutrients had been applied. No significant differences were found between the Foliar application and Soil treatments. Moreover, even no significant differences were found between application of micnobits or application of ions. Thus, we concluded that the soil - although very poor with a low content of micronutrients - was not lacking in the tested nutrients and the low availability of micronutrients in the soil was already sufficient for an optimal growth. The determination of micronutrient contents showed that ions and micnobits were taken up by both roots (Soil treatments) and by leaves (Foliar application). However, the amounts of micronutrients found in the leaves appeared to be higher than those described in literature for plant shoots with adequate growth. The contents of the micronutrients other than Fe varied between the treatments in both leaves and roots, suggesting excessive uptake that could have inhibited biomass production in these treatments. Foliar application with ions resulted in a higher micronutrient content than foliar application with micnobits. The fact that all treatments, whether applied to the leaves or to the soil or via priming, resulted in an accumulation of micronutrients in both shoots and roots, proved that the micronutrients had been transferred through the plants from the shoot to the roots (Foliar application) and from the roots to the shoot (Soil application). However, it could not be determined in which form, i.e. whether as ions, micnobits or metabolically processed, the micronutrients were transported through the plant. The presence of micnobits could only be detected for Fe2O3, CuO and MnO3. However, due to a high noise level in the ICP-MS sample analyses, it was not possible to quantify the content of the elements properly. Vitamin C content in leaves was highest in plants from the Control treatment, but not significant different from other treatments. No clear distinction could be made between the Soil and Foliar application, nor between treatments with ions or with micnobits. LCMS profiles of the lettuce leaves showed a relative intensity of 257 compounds present in the leaves. In the Soil and Foliar application, 80 out of the 237 metabolites (25%) had been changed significantly, although not annotated, from which 66 of them revealed a more than 2-fold difference. We conclude that this study with composite nanoparticles could not endorse the hypothesis that micnobits will be taken up more efficiently than ions, or that they will enhance growth in lettuce as reported in the literature for other crops. Furthermore, this study also clearly demonstrates the need for plant tissue testing as an important yardstick for supporting soil-based nutrient testing, prior to fertilizer recommendations.
Eliminating Zinc Deficiency in Rice-Based Systems
(2014-02) Andreas Duffner; Ellis Hoffland; Tjeerd Jan Stomph; Alida Melse-Boonstra; Bindraban, Prem S.
Zinc deficiency is a wide-spread and serious problem both in human populations and in crop production. It is a relevant issue in rice-based systems due to their extent and role in human nutrition worldwide. There is an urgent need to increase human Zn intake through biofortification strategies in these systems. Particularly in developing countries, there is a spatial correlation between human Zn deficiency and low Zn soils Main soil factors controlling plant-available Zn are pH, redox condition, organic matter content and concentrations of other trace elements. By far the biggest fraction of total Zn is adsorbed to the soil's solid phase in most soils. This requires management practices that avoid a risk for Zn fertilizer failure and/or a choice of rice cultivars that are able to mobilize Zn adsorbed by the soil's solid phase. Management practices could include balancing Zn with N and P fertilization, seed or follar application of Zn and effective organic matter management. On the plant level the rooting density, the root efflux (exudates) and influx (Zn) and Zn translocation are important factors. The translocation from aboveground vegetative tissues to the grain endosperm seems the most limiting step to reach higher Zn concentrations in grains. Genetic variation in several steps leading to grain Zn loading have been found, but options to align these do not seem to have been fully explored. It probably needs combination of breeding with Zn application treatments to both tackle Zn deficiencies at the crop growth stage and at grain Zn loading stages. The role of N fertilization in creating synergy also needs further investigations. To improve human Zn intake, several strategies can be applied, such as supplementation, dietary diversification and food fortification. Among these, biofortifying rice through breeding or agronomic management is the most sustainable strategy and unlikely to pose any adverse health effects on people. The few case studies available support this conclusion.
Establishing a Viable Fertilizer Quality Detection System
(2014-04) K. Perumal; J. Arunkuma; S. Ananthi; T.A. Sambanda Moorthy; B. Karthik; Bindraban, Prem S.; Upendra Singh
The proof of concept project entitled “Establishing the Viability of a Fertilizer Quality Detection System Using Alternative Analytical Technology (FAAT)” is aimed at developing a quick and robust methodology to determine the nutrient content in fertilizers. The methodology comprises the use of circular paper chromatography (CPC) and digital characterization of the corresponding chromatographic images incorporated in a database for automated assessments. One hundred (from the United States) and 22 (from India) different types of fertilizers were procured from the United States and India, and their nutrient properties were analyzed following conventional methods. These fertilizer samples were further diluted in 100 mL of 1% NaOH to obtain 3800 fertilizer concentrations. For the Indian fertilizers, 2200 samples were obtained with all 22 fertilizers by generating 100 different samples in incremental dilutions of 0.050g, up to 5 g. For the IFDC fertilizers, 1600 samples were similarly obtained from 80 of the 100 fertilizers, diluted up to 1 g. These fertilizer concentrations were analyzed using CPC. Three databases were created to serve as reference, comprising (i) the Indian fertilizer database with 1500 reference fertilizer sample images, (ii) the IFDC database with 563 samples and (iii) a combined database of 2063 samples. Finally, an unknown fertilizer chromatographic image from unknown fertilizer sample types was used for testing the accuracy of the methodology by comparing the chromatographic images with the images contained in the reference databases. Out of the 25 test samples from IFDC, 21 reported similarity between AAT methodology and conventional analytical methods for nutrient content determination, and hence on quality, implying that 84% were mimicked correctly. Out of the 18 fertilizers from India, 11 tested correctly when using the database with 1500 references, representing about 61% accuracy of retrieving the correct fertilizer type and quality. The consolidated database containing both IFDC and Indian fertilizer (2063) was tested and recorded 34 out of 43 test samples that were similar between the FAAT system and conventional analytical methods, indicating about 70% accuracy. The existing AAT software was fine-tuned and integrated as unique stand-alone software for the FAAT system and used for fertilizer testing. An investigation was also carried with two types of fertilizers: urea and single superphosphate (SSP), and deliberately adulterating them with low grade inputs. The urea fertilizer was adulterated with ammonium sulfate (AS) and single superphosphate in the ratios of 1:0, 1:1, 1:3 and 3:1. The adulterated fertilizers were blended using mortar and pestle and 0.500g and 1.000 g were taken for CPC image development. Both the urea fertilizer and SSP were adulterated with AS and gypsum and tested on the FAAT system based on CPC images. The adulterated samples were retrieved from the data base and indicated 100% and 71% accuracy, respectively. Our study shows that with further refinement, the use of AAT methodology for testing fertilizer nutrient content and the presence of contaminants, and hence quality of the fertilizer, is a promising technology.
Foliar Fertilizer Application – Preliminary Review
(2013-02) Bindraban, Prem S.; Wim Voogt; Chris Blok; Barbara Eveleens; Leo Marcelis
Plant nutrient uptake primarily occurs through the roots, but leaves can absorb certain nutrients through foliar sprays or deposition on the leaf surface. This is particularly important for plants like epiphytes or aquatic species that rely heavily on leaf nutrient uptake. Foliar sprays are commonly used when soil conditions limit nutrient availability or in specific crop situations. However, the effectiveness of foliar sprays and the mechanisms of foliar nutrient uptake are poorly understood. This study aims to provide an overview of the current scientific knowledge, practical experiences, and gaps in understanding regarding foliar nutrient application. The study conducted a literature review using agricultural, soil science, and plant nutrition databases to gather recent publications and scientific data on foliar applications. Additionally, interviews with crop and soil consultants were conducted to gather information on standard practices and recommendations. The focus was on greenhouse crops, field crops, fruit crops, citrus, tropical fruits, and cereals. The findings highlight the need to better understand the physiological mechanisms of nutrient uptake through leaves and stems. This knowledge can help identify effective nutrient compositions, determine the need for coating or chelation, and maximize nutrient uptake potential through foliar application. The study also emphasizes the necessity of distinguishing between factual information and beliefs or myths surrounding foliar application to improve fertilizer use efficiency.
Methodology to Assess the Impact of Fertilizer Strategies on Planetary Boundaries
(2013-03) Conijn, J.G; F.J. de Ruijter; J.J. Schröder; Bindraban, Prem S.
Fertilizers affect plant growth fundamentally and are essential to feed the world's population. Yet, fertilizer use also causes eutrophication and greenhouse gas emissions Overuse will aggravate these side effects, but underuse leads to the agro-ecosystem's degradation, poverty and hunger. Nitrogen and phosphorus fertilizers have been identified as one of the driving forces that push the Earth from its stable geological era of the Holocene into the Anthropocene with unknown implications for life on Earth. Curtailing nutrient losses will have far-reaching implications on the Earth's ecosystem and human health and well-being. This report describes a methodology to quantitatively link global N and P cycles to four other global change drivers: land-system change, freshwater use, climate change and stratospheric ozone depletion. This will allow the assessment of the impact of fertilizer interventions on these drivers revealing synergies and trade-offs concerning food security and the environment.
Nutrient Delivery System in Crop Plants to Augment Acquisition, Translocation and Utilization Efficiency
(2016-01) Renu Pandey; Sandeep Sharma; Mandira Barman; Bindraban, Prem S.
Efficient delivery of nutrients to plants is crucial for optimal growth and development. This publication investigates two nutrient delivery systems: through the root and via foliage. While the root system is primarily responsible for nutrient absorption, foliage can also be an efficient organ for nutrient uptake. The authors explore the possibility of enhancing nutrient absorption by modifying nutrient molecules to be charge-neutral, allowing them to pass through the plasma membrane unhindered. They highlight the negative environmental impacts of commonly used synthetic chelates and propose using artificially synthesized siderophores as a more sustainable alternative. The study investigates the potential of chelated iron foliar application and its impact on gene expression related to iron uptake. Furthermore, the authors emphasize the need for detailed investigation into the efficacy of foliar sprays with Fe-siderophore complexes and the confirmation of charge-neutral molecule passage through leaf plasma membranes. In addition, the publication addresses the challenges associated with inorganic phosphate (Pi) fixation in soil, which limits its availability to root cells. The authors propose a controlled-release technology utilizing nano-clay polymer composites to overcome this issue. By examining the interaction between clay and surface cross-linking polymers, they aim to enhance the slow-release properties of fertilizers, thus reducing P fixation and loss through runoff. Although previous studies have investigated the release behavior of P from nano-composites, crops' response to applying P-loaded nano-composites remains largely unexplored. The publication highlights the scarcity of reports evaluating crop yield response to polymer hydrogels and emphasizes the need to understand the mechanisms underlying nutrient mobilization from these polymers. The authors propose the development of a seed-coating material utilizing nutrient-loaded clay polymer composites, specifically targeting phosphorus (P) delivery to plants during the initial stages of growth. By loading the seed coating material with P, organic acid, and phosphorus-solubilizing bacteria, the researchers aim to improve root growth and seed establishment. The publication outlines the objectives of the study, which include evaluating the efficacy of Fe complexes applied as a foliar spray, identifying novel proteins involved in Fe absorption and translocation, studying the release behavior of the seed coating material loaded with phosphorus, investigating its impact on P uptake efficiency in crops, and finally, combining the most effective seed coating material with the optimal foliar formulation to enhance nutrient uptake efficiency in field conditions. This comprehensive study aims to contribute to developing advanced nutrient delivery systems to improve crop productivity while minimizing environmental impact.
Plant Exudates for Nutrient Uptake
(2015-03) D.H. Keuskamp; Richard Kimber; Bindraban, Prem S.; Christian O. Dimkpa; W.D.C. Schenkeveld
Plants require nutrients for unimpaired growth. Many plant strategies for acquiring nutrients from the soil involve root exudates that facilitate the detachment from the soil solid phase and the transport to the plant root. In this report, root exudation related to acquisition of nutrients other than nitrogen (N) and phosphate (P) has been considered. In this context, three important classes of root exudates can be identified: low molecular weight organic acids (LMWOA), phytosiderophores (PS) and reductants. The mechanisms by which these exudates can enhance bioavailability include ligand exchange, ligand-promoted dissolution, mineral dissolution by lowering solution saturation state through complexation, co-exudation of protons and chemical reduction. These mechanisms are not specific to a certain class of exudates, and a single class of exudates can be involved in multiple mechanisms. The efficiency of exudates in mobilizing nutrients from soil depends on the chemical affinity of the exudate ligand for the targeted nutrient element (the denticity of the exudate ligand plays an important role in this respect), the characteristics of the soil, and the susceptibility of the exudate to microbial degradation, adsorption and binding of non-targeted elements. A meta-analysis of available literature data on the response of root exudation levels by different crop species to the availability of specific nutrients was carried out. The relative change in root exudation level as a result of a decrease in the availability of specific nutrients was investigated. The responsiveness and the magnitude of these responses seem to be strongly plant species, cultivar and nutrient specific. Available data on exudation proved biased towards certain nutrients, specifically iron (Fe) and zinc (Zn), and comparisons between studies were often complicated due to differences in experimental approach. Furthermore, at present there are very few published data on exudation under actual rhizosphere conditions. Despite the shortage of data, the potential for utilizing root exudates for making better use of soil nutrient reserves and improving nutrient acquisition, e.g., in intercropping systems, looks promising and needs to be further explored.
Plant Strategies and Cultural Practices to Improve the Uptake of Indigenous Soil P and the Efficiency of Fertilization
(2013-04) Bindraban, Prem S.; A.L. Smit ; M. Blom-Zandstra; A. van der Werf
Phosphorus (P) availability is a significant constraint in global crop production. Current annual mineral P fertilizer input exceeds the actual uptake by crops, leading to P accumulation in soils and inefficient resource utilization. This study investigates the hypothesis that enhancing early plant growth can improve P uptake from indigenous soil resources and fertilizer P. The low recovery rate of applied mineral P fertilizer, typically less than 30%, is attributed to its binding with soil complexes, making it less available for plant uptake. The soil solution often exhibits very low P concentrations compared to root concentrations, emphasizing the need to increase P availability or enhance plants' ability to extract P from soil complexes. In regions with P-deficient soils, substantial P applications are required to improve fertility and enhance crop yields. Similarly, unintentional excess P application occurs in areas with nutrient surpluses, resulting from concentrated livestock production and subsequent manure application. These fertile soils can contain excessive total soil P, far exceeding the annual crop uptake. If these soil P reserves were fully available to crops, they could sustain agricultural production for several hundred years. Case studies in Africa demonstrate the relationship between total soil P content and maize grain yield, indicating the potential longevity of soil P reserves in sustaining production. Even soils with relatively low fertility levels have sufficient total P content to support production for over a hundred years. However, the assumed P content in crop biomass may be lower at these sites, implying even longer sustainability. By enhancing early plant growth, this study aims to improve plant P uptake efficiency, effectively utilize accumulated soil P, and optimize the uptake of newly applied P fertilizers. The findings of this research contribute to developing strategies for sustainable P management, promoting efficient resource utilization and improved crop productivity.
Preliminary Evaluation of the Feasibility of Using Geospatial Information to Refine Soil Fertility recommendations
(2015-06) Bindraban, Prem S.; Kempen Bas; Vereijken, P.F.G.; Keizer, L.P.C.; María Ruipérez González; Wendt John
IFDC carries out fertilizer field trials at hundreds of (georeferenced) locations throughout eastern and southern African countries. Yield data analyses from these trials typically focus on average yield responses and economic returns of specific fertilizer treatments with respect to control treatments. However, a deeper analysis of yield data might generate information about the spatial pattern of the response and provide insight in factors that cause differences in yield responses. These insights might be taken into account to make future fertilizer targeting more location or region- specific, as an alternative to blanket recommendations. The information may also be valuable for fertilizer companies and other actors in the chain at regional scale where to sell which fertilizer composition. The objective of this exploratory study was to gain insight into factors that cause differences in fertilizer response. which might aid in tailoring fertilizer recommendations to local or regional conditions. This is done through (1) a linear mixed model analysis of fertilizer field trial data using spatial soil and climatic data as covariates and (2) an exploratory geostatistical analysis of soil and fertilizer field trial data. The latter included the development of digital soil maps for eleven soil fertility parameters with random forest modeling and kriging. Soil and crop yield data for Burundi were used for these purposes. The results of the modeling exercises indicate that there is a general lack of correlation between soil type and climatic variables and yield. Based on these results, recommendations may not to be refined for Burundi, indicating that fertilizer formulations used in the omission trials may be valid throughout the study zone. The soil nutrient maps do not appear to be indicative of crop nutrient response, but are indicative of nutrient deficiencies that might be anticipated. We note, however, that eliminations of mistakes in the current datasets and used of more spatially and temporally synchronized covariate data would add value to the analysis. These findings may also prove different over more variable environments such as Rwanda, where soils are considerably more variable. The added value of geospatial analysis for improving fertilizer recommendations is not immediately evident from these exploratory analyses but the results and the lessons leamt can be used to scope a more robust and thorough strategy for further geospatial data gathering and analyses of fertilizer response trials and for anticipating required nutrient composition of fertilizers.
Se Fertilization: An Agro-Ecosystem Approach
(2014-03) Bindraban, Prem S.; G.H. Ros; A.M.D. van Rotterdam; G.D. Doppenberg; D.W. Bussink
Selenium (Se) is an essential micronutrient for humans, animals and certain lower plants, and its supply in global food systems is highly variable. The variation of Se status in humans largely depends on their diet, which is strongly related to the geographical variation in soil’s Se level. Selenium deficiency is regarded as a major health problem for 0.5 to 1 billion people worldwide. Whereas the global importance of selenium deficiency has been recognized for decades, strategic micronutrient interventions to overcome this deficiency are still limited. Basically, there are two groups of fortification strategies available to increase Se intake worldwide. First of all, human Se intake may be increased by supplementation of livestock, direct food fortification or supplementation with Se pills. Alternatively, agronomic strategies like plant breeding and fertilization can be used to increase Se uptake of staple food crops. We argue that the best strategy depends on the natural, societal and economic properties of local agro-ecosystems. Adapting the fortification strategy to the local properties of an agro-ecosystem is the way forward to solve Se deficiencies worldwide without resource exhaustion of the worlds’ scarce Se resources and potentially harmful environmental side-effects. An essential part of such an agro-ecosystem approach will be a robust and reliable fertilizer strategy that takes the spatial and temporal variability in climatic conditions, soil properties and cropping systems into consideration. Selecting the proper fertilizer strategy requires a mechanistic understanding of Se plant-soil-atmosphere cycling and insights in plant availability of added Se fertilizers. The research presented in this report aims to identify when applying Se fertilizer is effective in specific agroecosystems based on an inventory of specific production-ecological causes for its deficiency in relation to fertilizer application. Important factors controlling Se availability and uptake are identified using meta-analysis and are integrated in a framework for a decision support tool that guides users in the selection of effective fortification strategies. This research primarily focuses on fertilization as a fortification strategy, but other strategies are briefly introduced and evaluated. The review and meta-analysis indicate that fertilizer doses need to match crop demand with Se supply, given the capacity of soils to supply or retain Se during the growing season. Main soil properties controlling crop uptake efficiency of applied Se include acidity, redox potential, texture and organic matter. Agronomic practices such as liming, irrigation and basic fertilization (nitrogen, phosphorus and sulfur) additionally affect the crop uptake efficiency. Adapting fertilizer strategies to the local agronomic situation and soil properties can increase the crop uptake efficiency from 10% (common situation) up to 50%. Important fertilizer strategies include:  The use of a site specific fertilizer dose: Se fertilizer use should account for the Se supply and availability in the soil and any residual effects of former Se fertilizer applications.  The choice for a specific Se fertilizer: Selenate is about 8 times more effective on the short term than selenite and has smaller residual effects.  Application technique: Both foliar- and soil-applied fertilizers are able to enhance Se uptake, but foliar application is more resource efficient. Seed coating can be an alternative, but the crop uptake efficiency is usually less than 10%.  Application timing: Fertilizer application during the growing season results in higher Se levels in the crop in comparison with fertilizer applications before the growing season. By far, the most resource-efficient way to increase the Se intake in the world’s population appears to be by adding Se to food products along the production chain. The positive effects of food processing is however limited by the fact that a limited number of people have access to processed foods, particularly in developing countries. Fortification through agronomic practices can therefore be an efficient and effective approach to increase human (and animal) Se intake through simple techniques that can be integrated in current farm management. Plant breeding for enhanced Se uptake efficiency and Se fertilization are currently the most promising agronomic strategies to increase Se status of human populations as they can deliver increased Se to a whole population safely, effectively, efficiently and in the most suitable chemical forms. These strategies might also be complementary to fortification strategies like food processing. Social and economic factors such as the availability of Se-enriched fertilizers and governmental incentives and regulations are needed to increase farmers and public acceptance of fortification programs and Se-enriched food products. The developed decision support tool integrates all these aspects in such a way that it can be applied to any agro-ecosystem. In summary, agro-ecosystem-dependent fortification strategies are necessary to increase human Se intake without exhaustion of the worlds’ scarce Se resources. The use of Se fertilizers is currently one of the most promising strategies, in particular when the fertilizer strategy (dose, formulation, application and timing) is adapted to the local properties of an agro-ecosystem.
The Application of Nanotechnology for Micronutrients in Soil-Plant Systems
(2015-03) Bindraban, Prem S. ; C.M. Monreal; M. DeRosa; S.C. Mallubhotla; Christian O. Dimkpa
Micronutrients (MNs) are important to world agriculture and human health. Over 3 billion people across the world suffer from micronutrient deficiencies. Zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) have become yieldlimiting factors and are partly responsible for low food nutrition. Although crops use low amounts of MNs (<2.4 kg/ha), about half of the cultivated world’s soils are deficient in plant bioavailable MNs, due to their slow replenishment from the weathering of soil minerals, soil cultivation for thousands of years and insufficient crop fertilization. Relevant MN deficiencies occur more frequently in neutral to alkaline soils, under anaerobic conditions and in arid or semi-arid regions. The MN use efficiency (MUE) of most commercial fertilizers added to soils or foliage is 2.5% to 5% of applied, due to their rapid stabilization by soil components, low leaf penetration and low mobility in plants. In soil-plant systems, fertilizer-MNs interact with macronutrients resulting in synergistic, antagonistic or neutral response affecting yield and food quality. Thus far, conventional and newer fertilizer technologies and products are unable to synchronize the MN release from fertilizer according to crop demand during the growing season, resulting in low MUE. New efforts to improve crop yield, food nutrition and fertilizer-MUE involve the use of micro- and nanoencapsulation, nanomaterials (NMs), nanodevices and nanoparticles (NPs) of Zn, Fe, Mn and Cu oxides. Fertilizer products appear to increase MUE as follows: soluble salts < chelates < microcapsules ≤ nanocapsules = nanoparticles. Many of the effects of the new fertilizer materials on crop yield and quality, human health and environmental risks remain largely unknown. Nanobiotechnology will occupy a prominent place in transforming agricultural systems and food production worldwide in the coming years. This report proposes that the development of a MN intelligent nanofertilizer (INF) delivery platform may result in significant increases of MUE and food quality by enabling the synchronization of MN release from fertilizers according to crop demand. The novel MN-INF product development needs adequate financial support and a multidisciplinary team of scientists.

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Browsing Fertilizer Reports by Author "Bindraban, Prem S."

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