Macronutrient Fertilizers Research Articles

Maize response to macronutrients and potential for profitability in sub-Saharan Africa

Sub-Saharan Africa (SSA) is plagued by low productivity and little research is available on the attainable responses and profitability to applied nutrients under variable environments. The objective of this study was to determine the attainable maize grain response to and potential of profitability of N, P and K application in SSA using boundary line approaches. Data from experiments conducted in SSA under AfSIS project (2009–2012) and from FAO trials database (1969–1996) in 15 countries and constituting over 375 different experimental locations and 6600 data points are used. Both response to fertilizer and value cost ratio (VCR) are highly variable and no more than 61 % cases for N, 43 % for P and 25 % for K attain VCR of 2 or more. Also, based on the recent AfSIS data, VCR exceeds 1 in just 67 % (N), 57 % (P) and 40 % (K) of the cases, even when best management practices are applied on a research farm, and interest rates are zero. Chances for profitability are highest when soil organic carbon is 1–2 % and control maize grain yield is 1–3 t ha−1 but also depends on relatively static soil properties (primarily texture and mineralogy) that are not under farmer control. We conclude that return on investment of macronutrient fertilizer is highly variable and can be substantially increased by helping farmers decide where to apply the fertilizers. Consequently, farmers need access to information on factors influencing economic returns of fertilizer use in order to make the right decisions.

Fate of Zinc Oxide Nanoparticles Coated onto Macronutrient Fertilizers in an Alkaline Calcareous Soil.

Zinc oxide (ZnO) nanoparticles may provide a more soluble and plant available source of Zn in Zn fertilizers due to their greater reactivity compared to equivalent micron- or millimetre-sized (bulk) particles. However, the effect of soil on solubility, spatial distribution and speciation of ZnO nanoparticles has not yet been investigated. In this study, we examined the diffusion and solid phase speciation of Zn in an alkaline calcareous soil following application of nanoparticulate and bulk ZnO coated fertilizer products (monoammonium phosphate (MAP) and urea) using laboratory-based x-ray techniques and synchrotron-based μ-x-ray fluorescence (μ–XRF) mapping and absorption fine structure spectroscopy (μ–XAFS). Mapping of the soil-fertilizer reaction zones revealed that most of the applied Zn for all treatments remained on the coated fertilizer granule or close to the point of application after five weeks of incubation in soil. Zinc precipitated mainly as scholzite (CaZn2(PO4)2.2H2O) and zinc ammonium phosphate (Zn(NH4)PO4) species at the surface of MAP granules. These reactions reduced dissolution and diffusion of Zn from the MAP granules. Although Zn remained as zincite (ZnO) at the surface of urea granules, limited diffusion of Zn from ZnO-coated urea granules was also observed for both bulk and nanoparticulate ZnO treatments. This might be due to either the high pH of urea granules, which reduced solubility of Zn, or aggregation (due to high ionic strength) of released ZnO nanoparticles around the granule/point of application. The relative proportion of Zn(OH)2 and ZnCO3 species increased for all Zn treatments with increasing distance from coated MAP and urea granules in the calcareous soil. When coated on macronutrient fertilizers, Zn from ZnO nanoparticles (without surface modifiers) was not more mobile or diffusible compared to bulk forms of ZnO. The results also suggest that risk associated with the presence of ZnO NPs in calcareous soils would be the same as bulk sources of ZnO.

English

The use of plant biostimulants jointly or without macro or micro fertilization may be an alternative to change plant metabolism and consequently, improve bean crop yield. Under this circumstance, we aim to evaluate the influence of biostimulants and its interaction with macro and micronutrient fertilizers on common bean var. Perola yield in Bahia State (BA). The research started on 12 December, 2013 in the experimental farm of the State University of Southwestern Bahia (UESB), campus in Vitoria da Conquista – BA, Brazil. The experimental design used was the total randomized block with three replications, arranged in a factorial scheme (2x2x4) under two macronutrient fertilization levels (present or absent) and four biostimulants (Control, Stimulate, Booster and Biozyme), in which doses followed manufacturer recommendation for common bean crop. The following traits were assessed: plant height, stem diameter, first pod height, pod number, pod length, grain per plant, 100-grain dry mass and yield. The data was submitted to variance analysis, and means were compared by “F” and Scott Knott tests at 5% probability. We found that biostimulants enhanced common bean yield with or without macro and/ or micronutrient supply. Key words: Plant regulators, nutrients, fertilization, yield and Phaseolus vulgaris L.

Supplying Zinc Salt Tablets Increased Zinc Concentration and Yield of Coffee Trees

In Brazil there are two usual forms of supplying zinc (Zn) to coffee plants, in the soil with macronutrient fertilizers or by means of foliar sprayings. Both have limitations that compromise the Zn availability to the plant. This study examined the plant responses to the foliar sprays with ZnSO4 and insertion of Zn salt tablets, made with a mix of Zn sources, into the orthotropic branches of Coffea arabica L. Zinc supplied by foliar sprays or tablets inserted into the trunk both increased leaf Zn content, although the tablets provided more consistent Zn supply. Coffee production was higher with Zn treatments, regardless of the method of supply. The supply of Zn by the insertion of tablets into coffee tree trunks thus proved to be a promising way to supply Zn.

Implications of widespread algal biofuels production on macronutrient fertilizer supplies: Nutrient demand and evaluation of potential alternate nutrient sources

Biofuels from microalgae are currently the subject of many research projects to determine their feasibility as a replacement for fossil fuels. In order to be a successful candidate, there must be enough fertilizers available to support large scale production. Commercial fertilizers are available for biofuel production from the world fertilizer surplus, but due to nitrogen and phosphorus future production limitations, biofuels would ideally not use any of these resources to be a long term sustainable fuel. Nitrogen, phosphorus and potassium requirements were determined for two algal species, Chlorella and Nannochloropsis, to produce 19 billionl per year (BLPY). At this scale, both algal species would use 32–49%, 32–49% and less than 1% of the world surplus values of nitrogen, phosphorus and potassium, respectively. Nutrient recycling options and alternative sources of nutrients were evaluated to determine their potential contribution of lowering the synthetic fertilizer requirement. Results show that all of the recycling scenarios reduce the nutrient requirements, but catalytic hydrothermal gasification has the largest reduction of 95% of the nitrogen and 90% of the phosphorus. Contributions from all alternative sources can also provide only 5% or less of the required nitrogen when produced in the gulf region. For phosphorus in the same region, poultry concentrated animal feeding operations can provide up to 28% of the requirement of Chlorella. To find the least amount of nitrogen that may be used, catalytic hydrothermal gasification was combined with all of the alternative nutrients available in the gulf region. The maximum amount of biofuels that could be produced in this location without using any synthetic fertilizers is 50±20 BLPY from Chlorella and 45±19 BLPY from Nannochloropsis. This study shows that the nutrient requirement for biofuel production from microalgae will not be a limitation if recycling methods within the process chain and alternative sources of nutrients are utilized.

Formulation, synthesis and characterization of boron phosphate (BPO4) compounds as raw materials to develop slow‐release boron fertilizers

AbstractWe investigated the use of boron phosphate (BPO4) as a slow‐release boron (B) source. Boron phosphate compounds were synthesized by mixing boric acid (H3BO3) and phosphoric acid (H3PO4) and heating at temperatures of 25 to 1000°C for 1 or 24 h. X‐ray diffraction (XRD) patterns and chemical analysis confirmed the formation of BPO4. The crystallinity of these compounds increased with increasing temperature and heating time. The compounds synthesized at 300°C or less were hygroscopic and clumped together, while those synthesized at 500 to 1000°C were non‐hygroscopic and free‐flowing. The solubility of these compounds was assessed at different pH and P concentrations, and compared to the solubility of ulexite and colemanite. The solubility of the BPO4 compounds decreased with increasing synthesis temperature and with decreasing pH. The solubility and the kinetics of B release from BPO4 compounds synthesized at 500 and 800°C were slower than for most commonly used B sources. Given their slow dissolution, the BPO4 compounds may have potential to continuously supply B to crops in environments where B leaching is a problem. The compounds synthesized at 500 and 800°C show potential for co‐granulation with macronutrient fertilizers such as mono‐ammonium phosphate to produce slow‐release B‐enriched granules.

Nutritional composition of hazelnut (Corylus avellana L.) as influenced by basic fertilization

Nitrogen (N), phosphorus (P), and potassium (K) deficiencies are a widespread phenomenon throughout the world, and are one of the most common nutritional disorders in Turkish hazelnut (Corylus avellana L.) cultivation. In this research, the effects of macronutrient fertilizers on mineral contents and some biochemical contents of ‘Tombul’ hazelnut (Corylus avellana L.) variety cultivated in the Black Sea Region of Turkey were investigated, and the contribution of these nuts to human nutrition was determined. The trials were carried out at ‘Tombul’ hazelnut orchards, and the hazelnuts were fertilized with five different doses of nitrogen, phosphorus, and potassium in each year for three consecutive years. The basic fertilizers (N, P2O5, and K2O) significantly affected some biochemical contents and mineral compositions of the hazelnuts. In order to improve the biochemical and mineral compositions of hazelnut, 200 kg ha−1 and 400 kg ha−1 N fertilizations, 120 kg ha−1 and 160 kg ha−1 P2O5 fertilizations, and 400 kg ha−1 and 600 kg ha−1 K2O fertilizations could be recommended for practice. According to the daily mineral element requirements, 100 g of hazelnuts provided about 43.5% P, 13.2% K, 19.4% Ca, 37.0% Mg, 0.2% Na, 53.8% Fe, 24.5% Zn, 14.5% B, and 66.7% Mo of the recommended dietary allowances. Cu and Mn contents of 100 g hazelnut were higher than the respective daily requirements. These results indicated that the mineral composition of hazelnut depended not only on the variety but also on the cultivation techniques such as soil condition and especially basic fertilization practices.

Studies on Macronutrient Fertilization in Pomegranate under Sub-Tropical Plains

An investigation was carried out to study the influence of different levels of NPK fertilizers on plant growth, fruit yield and quality, and leaf NPK content in pomegranate cv. Kandhari under sub-tropical conditions. Graded doses of nitrogen (0-300g/plant), phosphorus (0-150g/plant) and potassium (0-300g/plant) fertilizers were applied through soil, in addition to a basal dose of FYM. Control plants were fed FYM only. Maximum increase in plant growth and fruit yield was recorded in plants receiving NPK @ 300:50:100g/plant, while Control plants registered least growth and yield. Potassium levels improved fruit weight over the Control. Higher dose of potassium also improved fruit colour and enhanced peel thickness and grain weight. Maximum TSS:acid ratio was seen with NPK @ 200:50:100g/plant. Reducing sugars were not affected by any treatment. Leaf N, P and K content increased with application of the respective nutrient.

Nutrient limitation of native and invasive N2-fixing plants in northwest prairies.

Nutrient rich conditions often promote plant invasions, yet additions of non-nitrogen (N) nutrients may provide a novel approach for conserving native symbiotic N-fixing plants in otherwise N-limited ecosystems. Lupinus oreganus is a threatened N-fixing plant endemic to prairies in western Oregon and southwest Washington (USA). We tested the effect of non-N fertilizers on the growth, reproduction, tissue N content, and stable isotope δ15N composition of Lupinus at three sites that differed in soil phosphorus (P) and N availability. We also examined changes in other Fabaceae (primarily Vicia sativa and V. hirsuta) and cover of all plant species. Variation in background soil P and N availability shaped patterns of nutrient limitation across sites. Where soil P and N were low, P additions increased Lupinus tissue N and altered foliar δ15N, suggesting P limitation of N fixation. Where soil P was low but N was high, P addition stimulated growth and reproduction in Lupinus. At a third site, with higher soil P, only micro- and macronutrient fertilization without N and P increased Lupinus growth and tissue N. Lupinus foliar δ15N averaged −0.010‰ across all treatments and varied little with tissue N, suggesting consistent use of fixed N. In contrast, foliar δ15N of Vicia spp. shifted towards 0‰ as tissue N increased, suggesting that conditions fostering N fixation may benefit these exotic species. Fertilization increased cover, N fixation, and tissue N of non-target, exotic Fabaceae, but overall plant community structure shifted at only one site, and only after the dominant Lupinus was excluded from analyses. Our finding that non-N fertilization increased the performance of Lupinus with few community effects suggests a potential strategy to aid populations of threatened legume species. The increase in exotic Fabaceae species that occurred with fertilization further suggests that monitoring and adaptive management should accompany any large scale applications.

Maize Nutrient Accumulation and Partitioning in Response to Plant Density and Nitrogen Rate: II. Calcium, Magnesium, and Micronutrients

Maize (Zea mays L.) yields have advanced through breeding complemented with evolving management technologies including plant density (PD) and macronutrient fertilizer inputs. Little is known about management‐induced changes in plant uptake or allocation of nutrients other than macronutrients. Therefore, impacts of both PD and N rate at three levels (low, medium, and high) on Ca, Mg, and micronutrient partitioning (for pertinent plant organs at six growth stages) were investigated at four environments in Indiana. Grain Ca, Mg, Fe, and Zn contents at maturity were primarily influenced by N rate, while the PD × N rate interaction influenced those of Mn and Cu. At the whole‐plant scale, PD and N rate significantly influenced all nutrient contents, and vegetative‐stage nutrient accumulation averaged 91% (Ca), 51% (Fe), 47% (Zn), and 73% (Mn, Mg, and Cu) of corresponding nutrient contents at maturity. During the vegetative phase, three modes of leaf vs. stem nutrient partitioning were: (i) preferential allocation of Mg and Zn to stems; (ii) preferential allocation of Fe and Ca to leaves; and (iii) isometric partitioning of Cu and Mn. Isometric nutrient concentration patterns between Mg and Zn were documented in leaf, stem (vegetative phase), and ear (reproductive phase). Early‐reproductive‐stage nutrient partitioning from plant to ear was greatest for Zn and Mg and mirrored their respective harvest indices (HIs) at maturity. Nutrient HIs, concentrations (grain + stover), and internal efficiencies at maturity were positively impacted by N rate but negatively by PD. Reliable micronutrient requirement estimations for maize under diverse management and yield levels help inform future balanced‐nutrient input decisions.

Zinc for the improvement of crop production and human health

Zinc (Zn) is an exceptional micronutrient regarding itsrelevance in biological systems because it is the onlytrace metal represented in all classes of enzymes(Broadley et al. 2007). A large diversity of essentialcellular functions and metabolic pathways are directlyinfluenced by Zn including function and structural sta-bilityofproteins,integrityofbiologicalmembranesandprotection against reactive oxygen species (Cakmak,2000). Nearly 2800 proteins in biological systems re-quire Zn for their activity and structural stability(Andreini et al. 2009).It is, therefore, not surprising that crop plants showrapid and particular disturbances in growth and devel-opmentwhentheyaregrowingonlowZnsoils.Atleastone-third of the cultivated soils globally is estimated tocontain too low amounts of bioavailable Zn (Sillanpaaand Vlek 1985) for optimal crop production. Low bio-availability of Zn not only reduces plant productivity, italsoimpairsnutritionalqualityoftheharvestedproductsby lowering Zn density in seeds/grains.These problems in crop production, food qualityand human health associated with Zn deficiency andthe environmental issues related to Zn were addressedat the 3rd International Zinc Symposium held inHyderabad, India, 10–14 October, 2011, with 195participants from 30 countries. The event was jointlyorganized by the International Zinc Association (IZA),the International Fertilizer Industry Association (IFA),Fertilizer Association of India (FAI) and HarvestPlus.The symposium consisted of 6 sessions devoted tothe following topics.& human nutrition and health,& soil and crop management,& zinc fertilizers and crop nutrition,& plant physiology& genetics and molecular biology& environmental issuesThis short article summarizes the main findings ofthis symposium. Details of the findings and conclu-sions can be found in the articles in this special issue.Low Zn supply by soils to crops is becoming moreprominent due to the use of high yielding cultivarsand/or application of macronutrient fertilizers unbal-anced by Zn fertilization. In cropping areas with in-tensified farming, additional management practices(e.g., Zn fertilization) are often required to avoid Zndepletion of soils to sustain crop productivity andnutritional quality of the harvested product. The deter-mination of soil bioavailable Zn, however, is not

Dissolution Kinetics of Macronutrient Fertilizers Coated with Manufactured Zinc Oxide Nanoparticles

The solubility of Zn in Zn fertilizers plays an important role in the agronomic effectiveness of the fertilizer. On the basis of thermodynamics, zinc oxide (ZnO) nanoparticles (NPs) should dissolve faster and to a greater extent than bulk ZnO particles (equivalent spherical diameter >100 nm). These novel solubility features of ZnO NPs might be exploited to improve the efficiency of Zn fertilizers. In this study, we compared the Zn solubility and dissolution kinetics of ZnO nanoparticles and bulk ZnO particles coated onto two selected granular macronutrient fertilizers, urea and monoammonium phosphate (MAP). The main Zn species on coated MAP and urea granules were zinc ammonium phosphate and ZnO, respectively. Coated MAP granules showed greater Zn solubility and faster dissolution rates in sand columns compared to coated urea granules, which may be related to pH differences in the solution surrounding the fertilizer granules. The kinetics of Zn dissolution was not affected by the size of the ZnO particles applied for coating of either fertilizer type, possibly because solubility was controlled by formation of the same compounds irrespective of the size of the original ZnO particles used for coating.

Evaluation of environmental impacts from microalgae cultivation in open-air raceway ponds: Analysis of the prior literature and investigation of wide variance in predicted impacts

It is often difficult to compare publications assessing the sustainability of algal biomass as a feedstock for biofuels, due to differences in data aggregation, life cycle boundaries, technical and life cycle assumptions, environmental metrics considered, and use of experimental, modeled or assumed data. Input data for the algae cultivation stage was collected from published studies, focusing on microalgae production in open-air raceway ponds. Input data was normalized to a consistent functional unit, 1kg of dry algal biomass. Environmental impacts were applied consistently to the different study inputs in order to eliminate this source of variation between the studies. Greenhouse gas emissions, fossil energy demand, and consumptive freshwater use were tabulated for the algal feedstock growth stage for open pond systems, and results were categorized (energy use, macronutrient fertilizers, and everything else) to compare the different studies in general terms. Environmental impacts for the cultivation of algal biomass in the considered reports varied by over two orders of magnitude. To illustrate impacts of variability in the cultivation stage on the ultimate environmental footprint of microalgae biofuels, algal oil harvesting, extraction and conversion to Green Jet Fuel was examined using the Renewable Jet Fuel process developed by Honeywell's UOP.

Timing of Macronutrient Supply during Cutting Propagation of Petunia

The objective was to quantify the effect of the timing of macronutrient applications on nutrient uptake, growth, and development of Petunia ×hybrida Hort. Vilm.-Andr. ‘Supertunia Royal Velvet’ during vegetative propagation. Starting with unrooted cuttings (Day 0), fertigation was applied continuously at three time intervals (Day 0 to 7, Day 8 to 14, or Day 15 to 21) using either a “complete” (C) water-soluble fertilizer containing (in mg·L−1) 75 NO3-N, 25 NH4-N, 12 phosphorus (P), 83 potassium (K), 20 calcium (Ca), 10 magnesium (Mg), 1.4 sulfur (S), 2 iron (Fe), 1 manganese (Mn), 1 zinc (Zn), 0.5 copper (Cu), 0.5 boron (B), and 0.2 molybdenum (Mo) or a micronutrient fertilizer (M) containing (in mg·L−1) 1.4 S, 2 Fe, 1 Mn, 1 Zn, 0.5 Cu, 0.5 B, and 0.2 Mo in a complete factorial arrangement. With constant fertigation using the C fertilizer, plant dry weight (DW) doubled from Day 0 (sticking of unrooted cuttings) to Day 7 (0.020 g to 0.047 g), root emergence was observed by Day 4, and by Day 7, the average length of primary roots was 2.6 cm. During any week that the M fertilizer was substituted for the C fertilizer, tissue N–P–K concentrations decreased compared with plants receiving the C fertilizer. For example, plants receiving the M fertilizer between Day 0 and 7 had 20% lower tissue-N concentration at Day 7 compared with those receiving the C fertilizer. Although both shoot DW and leaf count increased once macronutrient fertilization was resumed after Day 7, final shoot DW and leaf count were lower than plants receiving C fertilizer from Day 0 to 21. Time to first root emergence was unaffected by fertigation. Constant application of C resulted in a higher shoot-to-root ratio at Day 21 than all other treatments. Results emphasize the importance of early fertigation on petunia, a fast-rooting species, to maintain tissue nutrient levels within recommended ranges.

Nutrient Stratification in Uncultivated and Sugarcane-Cultivated Peatlands

Long-term sugarcane cultivation may alter nutrient distribution in the soil profile and contribute to deficiencies. The objective of this study was to determine how sugarcane cultivation altered nutrient stratification in peatlands. Soil pH decreased with depth for uncultivated soils but remained constant at 6.9 for sugarcane soils. Long-term fertilization did not result in accumulation of nitrogen (N) and phosphorus (P). Sugarcane soils had 74, 72, and 94% more zinc (Zn), manganese (Mn), and copper (Cu) than uncultivated soils 0–30 cm deep, indicating micronutrient fertilization rates were greater than their removal in harvested biomass. Total iron (Fe) concentrations were lower in sugarcane than uncultivated soils, indicating Fe removal in biomass exceeded fertilization rates. Macronutrient fertilization rates for sugarcane did not result in accumulation in soil, indicating close agreement with crop needs, while overapplication of most micronutrients, except Fe, occurred. Because of minimal environmental hazards associated with micronutrients, changes in their application rates may not be warranted.

Fertilization of Pinus pinea L. seedlings with a sewage sludge-based compost

Two experiments were conducted to evaluate the effect of a sewage sludge-based compost (SSC) on the growth and mineral composition of containerized Pinus pinea L. seedlings. In the first experiment, five different substrates were tested: four binary mixtures of SSC and peat (100% SSC, 75% SSC, 50% SSC and 25% SSC, by volume) without fertilization, and a control substrate (peat-based substrate + fertilizer). Seedlings growing in the 100% SSC substrate showed the lowest growth, a consequence of both the low water availability and the high electrical conductivity that made SSC unsuitable to be the only component of a growing-media for pine ;seedlings'. The 50% SSC substrate presented physical and chemical properties similar to the control substrate and near the acceptable range for a growing-media. Moreover, no significant differences were found between growth of seedlings from treatment 50% SSC (without mineral fertilization) and seedlings from control treatment (with mineral fertilization). In the second experiment, a fertilization assay was performed with two substrates selected from the first experiment (50% SSC and control). The two substrates were fertilized with three levels of a macronutrient fertilizer (0.5, 1.0 and 2.0 g L( -1)) and two levels of a micronutrient fertilizer (0 and 0.4 g L(-1) of fertilizer containing only micronutrients). Results obtained suggest that replacing 50% (by volume) of peat-based substrate by the sewage sludge-based compost allowed: maintenance of the commercial value of seedlings; reduction of the amount of peat used in the substrate; a need for only half the amount of macronutrient fertilizer applied in the basal fertilization; and omission of micronutrient fertilization.

Induced growth of phytoplankton using two fertilizers (NPK and agrolyser) under laboratory conditions

An investigation was carried out on the ability of two types of fertilizer; agrolyser-micronutrient and NPK (nitrogen, phosphorus, potassium)-macronutrient in inducing phytoplankton growth for sixteen days under laboratory conditions. The parameters studied were abundance, species diversity and occurrence of the phytoplankton. Twelve 14 L plastics tanks labeled A, B, C and D was used. Each letter represented a fertilizer treatment (three replicates): A, 0.27 g agrolyser; B, 200 g NPK; C, 200 g agrolyser + 0.27 g NPK; and D which is the control. Before the application of these fertilizers, water samples were taken for phytoplankton analyses using 250 ml wide mouth plastic containers. All the tanks were allowed to be naturally inoculated for 3 days. Samples were collected for phytoplankton and physicochemical parameters at an interval of 3 days except temperature which was measured twice daily (morning and evening). A total of 1244 phytoplankton made up of 20 species, belonging to three families: Bacillariophyceae (diatoms), Cyanophyceae (blue-green algae) and Euglenophyceae (euglenophytes) were observed. Out of these algae, tanks C had 51.7%, B 33.2%, A 10.6% and D 4.5% phytoplankters. In the various groups of tanks, the orders of abundance, species diversity and percentage distribution of species of algae were C>B>A>D, C>B>A=D and C>B>D>A, respectively. This paper intends to provide preliminary information to fish farmers that agrolyser should be combined with a macronutrient fertilizer for better fertilization of pond. Key words: Induced growth, phytoplankton, fertilizer, NPK, agrolyser.

Enhancement of oceanic uptake of anthropogenic CO2 by macronutrient fertilization

A global three‐dimensional ocean carbon cycle model was used to investigate the use of macronutrient fertilization of the ocean to increase the oceanic uptake of CO2. To simulate macronutrient fertilization, phosphate was added to the 18°–50°S surface ocean. The carbon sequestration efficiency of fertilization was determined from the ratio of increased ocean uptake of anthropogenic CO2 to the rate of phosphate addition to the upper ocean (converted to carbon units using the C/P ratio of organic matter, 106). The model simulation produced a maximum efficiency of 78%. However, the simulations demonstrated that changes in calcium carbon production with macronutrient fertilization could significantly reduce carbon sequestration efficiency. When calcium carbonate production increases at the same rate as export production, the carbon sequestration efficiency is reduced by 25% when compared to a simulation where calcium carbonate production is held constant. The study also discusses several other potential process that could impact the efficiency phosphate fertilization to sequester carbon in the ocean and the potential consequences of large‐scale macronutrient fertilization of the ocean.

RESPONSE OF THE COMMON CABBAGE (Brassica oleracea L. var. capitata L.) TO BORON FERTILIZATION

The response of the common cabbage (Brassica oleracea L. var. capitata L.) to boron fertilization in soils of the state of Paranii, Brazil, is provided Six types of soils, LRd; LRe, Ca1; Ca2, TRd, and LEd were selected, treated with macronutrient fertilizer, their pH was corrected, according to routine. The experiment was conducted in 2.5-L capacity pots, with 2 kg of each soil, in a greenhouse. Each type of soil, in triplicate samples, received boron treatment with boric acid: 0.0 g; 0.1 g; 0.2 g. Pots were kept at 70% water capacity retention for 7 days, after which they received 6 cabbage shoots. Two shoots were maintained and later only one was kept in each pot. The duration of the experiment was 8 weeks, after which harvest was undertaken. Plants were dried in stoves, weighted, ground, and conditioned for further analysis. Extractor HCl 0.05 mol L-1 was used to determine boron in soils. Although soils Ca1, LRd, and LEd gave significant responses to treatments, concentrations of available boron over 4 μg g-1 were toxic to cabbages.

Automated management of nutrient solutions based on target electrical conductivity, ph, and nutrient concentration ratios

An algorithm to automatically formulate the composition and prepare nutrient solutions for soilless cultures based on desired characteristics given as target values is proposed. To formulate the complete ionic composition of a nutrient solution, standard recommendations referring to the following solution characteristics should be available: (i) electrical conductivity (EC), (ii) pH, (iii) concentration ratios of macronutrients (meq basis), and (iv) micronutrient concentrations. Moreover, the mineral composition of the water used to prepare the nutrient solution should be taken into account. To develop the main steps of the algorithm, the total salt concentration (meq L‐1) of the nutrient solution is related to the desired electrical conductivity. The target pH indicates the concentration of HCO3 − in the nutrient solution, whereas the absolute concentration of each macronutrient is derived from the desired concentration ratios and the total salt concentration. The necessary calculations are standardized through the development of formulae. Furthermore, the differences in nutrient concentrations between desired levels in the solution and those found in the tap water represent the amounts of nutrients per volume nutrient solution (meq L−1) which should be added through fertilizers. The above described steps of the algorithm have been tabulated to facilitate their implementation. Moreover, a numerical example concerning the composition of a nutrient solution for cucumbers is given. In the final steps of the algorithm, two standard formulae are used to calculate the quantities of individual macronutrient and micronutrients fertilizers needed to prepare particular volumes of stock solutions. Alternatively, when stock solutions of single fertilizers having known concentrations are used, the composition of the nutrient solution can be automatically adapted to new target values. This task can be performed without replacing the existing stock solutions by rearranging the formulae used in the last steps of the algorithm to calculate dilution ratios instead of fertilizer quantities.