Boron foliar fertilization of soybean and lychee: Effects of side of application and formulation adjuvants

Experiments to assess the rate of absorption and translocation of foliar‐applied, isotopically labeled boric acid (BA) were carried out with lychee (Litchi chinensis Sonn.) and soybean (Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl₂ and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of ¹⁰B to other leaf parts and no effect of adjuvants in increasing ¹⁰B absorption were recorded. In contrast, ¹⁰B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of ¹⁰B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased ¹⁰B absorption and enhanced acropetal ¹⁰B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl₂ in combination with 500 mM sorbitol decreased the rate of ¹⁰B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal ¹⁰B translocation was very limited. A distinct effect of B‐sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.     

Influence of phosphorus nutrition and root zone temperature on growth and mineral uptake of peach seedlings 1

Siberian C peach seedlings (Prunus persica L. Batsch) were grown for 35 days in all combinations of Long Ashton nutrient solution containing P concentrations of 0.05, 0.5, or 5.0 mM and root zone temperatures (RZT) of 8°C, 16°C, and 24°C. At harvest, a significant interaction between solution P concentration and RZT occurred for shoot and root dry weight, root length, shoot P concentration and shoot P uptake. At 8°C RZT, P concentration and uptake but not growth were increased by P. At 16°C and 24° C RZT, growth was depressed at the 5.0 mM P level with shoot P concentration and uptake lower at 24°C than 16°C. The inflow of P to the peach shoot per unit root length was increased at high P concentration and low temperatures but was lower than whole plant inflow rates for apples. The growth depression at high temperature‐high P was related to increased young leaf chlorosis, reduced shoot Fe and a possible P/Zn imbalance.     

Permeability of peach leaf cuticles to boron

Isolated leaf cuticles and intact plants of one‐year‐old potted ‘Red Haven’ trees grown in the greenhouse were used to study the permeability of leaf cuticles to boron (B). The isolated leaf cuticles were prepared enzymatically. Flux was determined using a transport cell. Permeability coefficient (P) was calculated and used as the parameter of cuticle permeability to B. For intact plant studies, enriched‐¹⁰B boric acid solution was evenly spread onto the abaxial or the adaxial side of a leaf. The trees were sacrificed three days after the treatment and selected plant parts were analyzed with ICP‐AES and ICP‐MS spectrometers. The ¹⁰B content was used as the parameter of B permeability in vivo. The permeability coefficient of peach leaf adaxial cuticle was in the order of 10^‐7 cm/sec. There were no difference in the permeability coefficients among B concentration and surtactant treatments. The pH had variable effect on B absorption through the cuticle of the adaxial side of the leaf. For the in vivo study of B uptake by peach leaves, the abaxial side was more efficient than the adaxial side, with the total ¹⁰B taken up four times greater in the abaxial side than the adaxial side. The absorption percentages of the total ¹⁰B applied in the abaxial and adaxial sides were 0.31% and 0.08%, respectively. Scratches on the treated leaves made the total ¹⁰B uptake and translocation higher than the control treatment.     

Cadmium uptake by Lupinus albus (L.): Cadmium excretion,a possible mechanism of cadmium tolerance

Cadmium (Cd) uptake by white lupin (Lupinus albus) was studied at low Cd concentrations (0.05nM to 5 μM) in hydroponic solution. Ten 12‐day old seedlings were pretreated in 0.5 mM CaCl₂ solution in presence and absence of metabolic inhibitors (DCCD, DNP or NaN3). Cadmium solutions were labelled with carrier free ¹⁰⁹CdCl2. Cadmium uptake was measured after a 2 h desorption in unlabelled CdCl2 solution. In the absence of any metabolic inhibitor and at 5 [μM Cd, roots absorbed 235.23 μg Cd/g root dry weight. Over the range of lnM to 5 μM Cd, exchangeable Cd represented approximately 5% of the absorbed fraction, and about 25 % of the total absorbed Cd was adsorbed to the root. Cadmium was passively absorbed to about 30% as observed in the presence of the inhibitor (DCCD). Ative absorption which represented 70% of Cd uptake involved H⁺‐ATPase carriers. Cadmium absorption was reduced to 30 and 20% in presence of lanthanum (La³⁺) and zinc (Zn²⁺), respectively which suggested that calcium (Ca), Cd, and Zn use the same carriers. Cadmium uptake in presence of DNP or NaN3 was approximately 4‐ fold that in control. Data showed presomption for an excretion of Cd out of root cells which could be the expression of a detoxification process limiting cell contamination.     

Boron toxicity in kiwifruit plants (Actinidia deliciosa), treated with nitrate,ammonium, and a mixture of both

The objective of this research was to study the effects of nitrogen (N) forms (NO₃^–, 2.6 mM; NH₄⁺, 2.6 mM; NO₃^–, 1 mM + NH₄⁺, 1.6 mM) on the growth and mineral composition of kiwifruit plants exposed to three boron (B) levels (0.025, 0.1, 0.3 mM). The kiwifruit plants were grown in a 1:1 sand : perlite mixture and irrigated daily with nutrient solutions. Shoot height, mean shoot dry weight, the number of leaves, mean leaf dry weight, and N concentration of NH₄‐treated plants were significantly higher compared to the NO₃^– treatment at all B levels. The concentration of 0.3 mM B significantly reduced shoot height for all N treatments. Boron toxicity symptoms appeared 14 days after starting the experiment, when plants were treated with 0.1 and/or 0.3 mM B. The nitrate supply reduced the B concentration of roots, but B levels of different leaf parts were hardly affected by the N form. Furthermore, the NH₄‐N form significantly reduced the Mg concentration of the leaves.     

Effects of solution pH,temperature, nitrate/ammonium ratios,and inhibitors on ammonium and nitrate uptake by Arabica coffee in short‐term solution culture

Solution pH, temperature, nitrate (NO₃ ^‐)/yammonium (NH₄ ⁺) ratios, and inhibitors effects on the NO₃ ^‐ and NH₄ ⁺ uptake rates of coffee (Coffea arabica L.) roots were investigated in short‐term solution culture. At intermediate pH values (4.25 to 5.75) typical of coffee soils, NH₄ ⁺ and NO₃ ^‐ uptake rates were similar and nearly independent of pH. Nitrate uptake varied more with temperature than did ammonium. Nitrate uptake increased from 0.05 to 1.01 μmol g^‐1 FWh^‐1 between 4 and 16°C, and increased three‐fold between 16 to 22°C. Between 4 to 22°C, NH₄ ⁺ uptake rate increased more gradually from 1.00 to 3.25 μmol g^‐1 FW h^‐1. In the 22–40°C temperature range, NH₄ ⁺ and NO₃ ^‐ uptake rates were similar (averaging 3.65 and 3.56 umol g^‐1 FW h^‐1, respectively). At concentrations ranging from 0.5 to 3 mM, NO₃ ^‐ did not influence NH₄ ⁺ uptake rate. However, NO₃ ^‐ uptake was significantly reduced when NH₄ ⁺ was present at 3 mM concentration. Most importantly, total uptake (NO₃ ^‐+NH₄ ⁺) at any NO₃ ^‐/NH₄ ⁺ ratio was higher than that of plants fed solely with either NH₄ ⁺ or NO₄ ^‐. Anaerobic conditions reduced NO₃ ^‐ and NH₄ ⁺ uptake rate by 50 and 30%, respectively, whereas dinitrophenol almost completely inhibited both NH₄ ⁺ and NO₃ ^‐ uptake. These results suggest that Arabica coffee is well adapted to acidic soil conditions and can utilize the seasonally prevalent forms of inorganic N. These observations can help optimizing coffee N nutrition by recommending cultural practices maintaining roots in the temperature range optimum for both NH₄ ⁺ and NO₃ ^‐ uptake, and by advising N fertilization resulting in a balanced soil inorganic N availability.     

Adenosine triphosphate (ATP) and microbial biomass in soil: Effects of storage at different temperatures and at different moisture levels

Abstract

On air‐drying, the ATP contents of two moist soils fell to about one quarter of their original values. When a freshly‐sampled soil (field temperature 5.5°C) was stored moist (43% water holding capacity) for 7 days at 25°C the ATP content increased from 4.54 to 7.84 μg ATP g^‐1 soil. Storage at 10°C caused a smaller increase; to 5.39 μg g^‐1 soil. Microbial biomass C also increased on storage but the relative increase was less than that of ATP. Thus the biomass C/ATP ratio fell from 234 in the freshly sampled soil to 168 in the soil stored moist for 7 days at 25°C. The ATP content declined to less than half its starting value if storage was under waterlogged conditions.

The ATP method for determining microbial biomass in soil depends on the use of a constant factor (5.85 mg ATP g^‐1 biomass C) for converting ATP content to biomass C. This factor came from work on soils that had been stored moist at 25°C for several days before biomass C and ATP measurements were made: it is only applicable to soils that have been stored in this way.     

Root‐zone temperature affects nutrient uptake and growth of snapdragon

Nutrient uptake by snapdragon (Antirrhinum majus L. ‘Peoria') was compared at five root‐zone temperatures: 8, 15, 22, 29, and 36°C. Uptake of nitrate (NO₃ ^‐‐N), ammonium (NH₄ ⁺‐N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), iron (Fe), manganese (Mn), and zinc (Zn) responded quadratically to increasing root‐zone temperature. Greatest nutrient uptake temperature varied with nutrient but ranged from 15 to 29°C. Uptake of copper (Cu) and molybdenum (Mo) were unaffected by root‐zone temperature. Dry weight gain and stem length also responded quadratically to increasing root‐zone temperature. Optimal temperatures for nutrient uptake and growth were similar, averaging 22°C. These results indicate increasing or maintaining root‐zone temperatures near 22°C maximizes growth and nutrient uptake of snapdragons.     

Boron Nutrition Studies with Cotton and Sunflower in Southern Turkey

Wide variations in boron (B) contents are typical of Turkish soils and plants, and most of the variation, 84% of the plant-soil B values are within the “normal.” Boron application on low B soils can make a contribution to yield in cotton and sunflower crops. Field experiments were carried out on clayey and medium-textured soils, which are Chromoxererts, Haploxererts, Xerochrepts, and Xerofluvents in Southern Turkey to study the effects of boron fertilization on irrigated cotton and rainfed sunflower growth, yield, and yield components. Four levels of boron—0, 1, 2, and 3 kg ha^?1—were applied at planting and the experimental design was completely randomized block design with four replications. There was a 31% and 31.9% increase in seedcotton yield at 3 kg and 2 kg ha^?1 of B, compared to the control only two out of four sites. There was an average increase of 61.4% in boll weight with 2 kg B ha^?1 application compared to the control. Effect of different application rates of B was not significant for fiber length, fiber strength, and fiber length uniformity. All levels of boron produced higher head diameters over control only one out of four sites. Boron applied at the level of 3 kg ha^?1 produced the highest 1000 seed weight of 47.5 g representing an 18% increase over the control. Boron applied at the level of 1 kg ha^?1 produced the highest seed yield, representing a 25% increase over the control only at one out of four sites. Boron was no value as a fertilizer for sunflower under given experimental conditions even though some uptake of boron was occurred. Boron fertilization may be regarded as effective in improving cotton yields.     

High night temperature stimulates photosynthesis,biomass production and growth during the vegetative stage of rice plants

Abstract

The effects of night temperature on biomass accumulation and plant morphology were examined in rice (Oryza sativa L.) during vegetative growth. Plants were grown under three different night temperatures (17, 22 and 27°C) for 63 days. The day temperature was maintained at 27°C in all treatments. The final biomass of the plants was greatest in the plants grown at the highest night temperature. Total leaf area and tiller number were also the greatest in this treatment. Growth analysis indicated that the relative growth rate in the 27°C night-temperature treatment was maximal between days 21–42 and this was caused by increases in leaf area ratio, leaf weight ratio and specific leaf area. Plant total nitrogen contents did not differ among treatments. However, nitrogen allocation to the leaf blades was highest and the accumulation of sucrose and starch in the leaf blades and sheaths was the lowest in the 27°C night-temperature treatment by day 42. Despite this, dark respiration was also highest, and both the gross and net rates of CO₂ uptake at the level of the whole plant at day 63 were the highest in the 27°C night-temperature treatment. Thus, high night temperature strongly stimulated the growth of leaf blades during the early stage of rice plant growth, leading to increased biomass during the vegetative stage of the rice plants. As the CO₂ uptake rate per total leaf area was higher, photosynthesis at the level of the whole plant was also stimulated by a high night temperature.     

Time course study on the mobility and pattern of distribution of foliar‐applied boron in peaches

One‐year‐old Red Haven’ peach (Prunus Persica) trees grown in pots in the greenhouse were used to study the time course mobility and pattern of distribution of boron (B). Enriched‐¹⁰B boric acid solution was evenly spread onto the abaxial side of the fifth leaf (numbered acropetally). After harvesting at different time intervals, selected plant parts were analyzed for ¹⁰B using an ICP‐MASS spectrometer. The results showed that within 4 hours, B could be taken up and translocated bidirectionally to all plant parts, except for the fine roots. Treated leaf, green stem, and fine root were the tissues having high ¹⁰B concentrations in comparison to the other tissues. The highest ¹⁰B concentrations in the fed leaf, green stem, and fine root were reached in 12 hours, at the 4th week, and in 72 hours, respectively. The total ¹⁰B absorbed averaged 0.3% of the total ¹⁰B applied, with the highest total percent recovery of 0.43%, which was reached in 72 hours. The total amount of ¹⁰B exported from the fed leaf was more than 50% of the ¹⁰B absorbed. A comparison of the ¹⁰B/¹¹B ratio and the ¹⁰B content was used as the parameter of B movement. The method of data expression is also discussed.     

Antagonistic effects of root zone temperature and iron on phosphorus uptake by bush bean

Radiophosphorus (³²P) and hydroponically‐grown bush bean were used to study P absorption kinetics as affected by root zone temperature (RZT) and iron (Fe). Phosphorus uptake increased significantly (p < 0.05) at each successive 10°C rise in RZT from 15 to 35°C, and quadratic regression equations were highly correlated (R² = 0.98) between the uptake amount and exposure time. An estimated Q₁₀ value of 1.5, and the corresponding Arrhenius constant μ of 31 kJ/mol for P uptake were within range for a diffusion process in an aqueous solution. A concentration of 5 μmol/L Fe significantly (p < 0.05) reduced P uptake from 6 h on at the RZTs studied, and Q10 and μ values were estimated at 1.2 and 14 kJ/mol, respectively.     

Micronutrient toxicity in buffalograss

The growth responses of buffalograss [Buchloe dactyloides (Nutt.) Engelm.] to elevated micronutrient levels in the fertilizer solution were investigated. Seedling plants established in peat‐lite mix in 11‐cm (0.6 L) pots in the greenhouse were irrigated with solutions containing 0.5, 1, 2, 4, 6, 8, or 12 mM of boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn). The control solution contained (in μM): 20 B, 0.5 Cu, 40 Fe, 10 Mn, 0.5 Mo, and 4 Zn. A standard macronutrient concentration was used for all treatment solutions. Boron and Mo induced visual toxicity symptoms more readily than other micronutrients. Boron toxicity was characterized by chlorosis often accompanied by bleached leaf tips, while Mo toxicity resulted in leaf necrosis. The lowest levels that induced visual foliar toxicity were 0.5 mM B, 2 mM Cu, 4 mM Fe, 6 mM Mn, 1 mM Mo, and 4 mM Zn. Chloride did not induce foliar abnormalities in the concentration range tested. Biomass yield was reduced when the nutrient solution contained 2 mM B, 6 mM Cu, or 2 mM Mo. Elevated levels of Cl, Fe, Mn, and Zn did not alter dry matter yield. The relationship between the nutrient and tissue concentrations was determined for each microelement.     

Nutrient deficiency symptoms and boron uptake mechanisms of rice

There is little agreement on the leaf and shoot boron (B) requirement of rice (Oryza saliva L.) and the optimum hydroponic solution B concentration for rice. Questions on the mechanism of B uptake active or passive are also unresolved. We grew rice in hydroponic solutions in a growth chamber for six weeks with B at 0, 0.05, 0.2, 1, 5, 10, 25, and 50 μM. Transpirational flow, dry matter yields and tissue B were determined. Results indicated that B deficiency occurred when there was <7.3 mg kg^‐1 B in the flag leaves, <3.6 mg kg^‐1 B in shoots, and <0.2 μM B in the nutrient solutions. Boron additions increased dry matter and plant height. Typical B‐deficiency symptoms were a light color or chlorosis on almost all of the youngest leaves and stems, an unthriftiness, leaf tip burn, and pale bands 2–3 mm wide on leaves, particularly on the moderately B‐deficient plants. Whitish and twisted new leaf tips occurred at >0.05 μM B. A mass balance analysis that compared the total mass of B in the plant versus B provided via transpirational flow showed that at high hydroponic B supply, passive uptake and active excretion of B, or, active blockage of B may have occurred, for > 10‐fold differences existed between the B mass in plant and B mass that could be provided via transpirational flow. Thus, B uptake was against a concentration gradient and high B supply, and as other evidence indicated, at low B supply.     

Zinc‐boron interaction effects in oilseed rape

The interaction effect of applied zinc (Zn) and boron (B) on early vegetative growth and uptake of Zn and B by two oilseed rape (canola) (Brassica napus L.) genotypes was investigated in a sand culture experiment under controlled environmental conditions. Two genotypes (Yickadee and Dunkeld) were grown at three Zn levels (0.05, 0.25, and 2.0 mg kg^‐1 soil) and two B levels (0.05 mg kg^‐1 soil and 0.5 mg kg^‐1 soil). Dunkeld produced significantly higher shoot and root dry matter than Yickadee at low Zn and low B supply indicating the superiority of Dunkeld over Yickadee for tolerance to both low Zn and low B supply. Chlorophyll content of fresh leaf tissue was increased significantly by an increase in Zn and B supply. Zinc deficiency enhanced B concentration in younger and older leaves. Boron concentration was higher in older leaves than in the younger leaves irrespective of B deficiency and sufficiency indicating immobility of B in two oilseed rape genotypes tested. Zinc concentration was higher in younger leaves than in the older leaves indicating mobility of Zn. An increased supply of Zn enhanced B uptake under high boron supply only. Zinc uptake in Dunkeld was enhanced significantly with an increased rate of B supply under high Zn supply, while the effect was not significant in Yickadee. Dunkeld proved to be more efficient in Zn and B uptake than Yickadee.     

Boron availability and uptake in huanglongbing-affected citrus trees on a Florida entisol

Abstract

Florida sandy soils, particularly, Entisols are low in boron (B) and occasionally have B deficiency for citrus. A study was set-up at Citrus Research and Education Center, Lake Alfred, Florida, on a Candler fine sand to determine the availability and uptake of B in a high-density citrus planting of Huanglongbing (HLB)-affected trees. Boron was applied at 1.12?kg ha^?1 in three splits, at University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) recommended rate (1×), and at 2× the recommended rate using foliar and soil application methods. Soil samples were taken from soil surface to 60?cm depth in 15-cm increments within the irrigated and non-irrigated zones. Soil and leaf samples were analyzed for B using Mehlich III extraction method and acid digestion, respectively. Results showed the leaf B concentration for soil applied rate 1× was significantly higher (P?<?0.001) than that of foliar applied either at single or double rate but both were in the optimum range recommended by UF/IFAS. The sorption study revealed that there was no sorption (K_D < 0.2?L kg^?1) but K_D at 0–15-cm depth was 3× greater than that at 15–60?cm depths. The concentration of B in the leaf tissue remained in the recommended optimum critical range. Sorption coefficients showed negligible B sorption which means most applied B would be prone to leaching under heavy rains or saturated soil conditions on Florida sandy soils thus requiring judicious management for optimizing tree performance and sustaining environmental quality.     

INFLUENCE OF HIGH TEMPERATURE AND UREA FERTILIZATION WITH N-(N-BUTYL) THIOPHOSPHORIC TRIAMIDE AND DICYANDIAMINDE ON COTTON GROWTH AND PHYSIOLOGY

The objective of this growth chamber study was to evaluate the effect of adding N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiaminde (DCD) to urea fertilizer, on the physiology and growth of cotton (Gossypiumhirsutum L.) under normal and high temperatures. Treatments consisted of two day temperature regimes, 30°C and 38°C, and five nitrogen fertilization applications: unfertilized control, 125 kg ha^?1 of urea, 93 kg ha^?1 of urea, 93 kg ha^?1 urea + NBPT, and 93 kg ha^?1 urea + NBPT + DCD. The addition of NBPT to urea fertilizer had positive effects on leaf chlorophyll, leaf area, dry matter, nitrogen (N) uptake, and N use efficiency. The absence of a significant interaction effect indicated that N fertilization was not influenced by temperature. Deficiency of N significantly decreased leaf chlorophyll, increased glutathione reductase, decreased protein and increased leaf nitrate reductase. Physiological changes under high temperature included increased plant N uptake, glutamine synthetase, leaf chlorophyll, protein content, plant height and leaf area were due to high N uptake and utilization.     

Effects of atmospheric nitrogen dioxide on uptake and assimilation of ammonium in soybean plants

Twelve‐day‐old soybean plants were supplied with 1 mM ammonium chloride (NH₄C1) to roots and exposed to 0.2–0.25 μL.L^‐1 nitrogen dioxide (NO₂) for seven days. Amount and rate of ammonium uptake were decreased by NO₂ exposure. However, the ammonium concentration in leaves and leaf pH of exposed plants were increased by NO₂ exposure. These results suggest that the decrease in ammonium uptake may be due to the decline in hydrogen (H⁺) ion concentration in exposed plants which resulted from the reduction of the nitrate and nitrite from NO₂ absorption. They also suggest that the decrease in ammonium uptake and the competition for energy between nitrate reduction and ammonium assimilation may limit ammonium assimilation to organic nitrogen (N) which would further inhibit acidity increase in exposed plants and ammonium uptake by roots.     

Soil Application of Boron Improves the Tillering,Leaf Elongation,Panicle Fertility,Yield and its Grain Enrichment in Fine-Grain Aromatic Rice

Boron (B) is one of the essential micronutrients having a specific role, particularly during reproductive phase, in rice. In a previous experiment on aerobic rice, panicle sterility was noted as one of the major challenges. This experiment was conducted to evaluate the influence of soil-applied B on tillering, panicle sterility, water relations, and grain enrichment in fine-grain aromatic rice cultivars ‘Super Basmati’ and ‘Shaheen Basmati’. Boron was soil applied at 0.50, 0.75, 1, 1.25, and 1.50 kg ha^?1 while the control treatment did not receive B. Rate of leaf emergence and elongation and tiller appearance were significantly improved by B application. Likewise, B application also improved the leaf chlorophyll contents and water relations in both rice cultivars. Substantial improvement in kernel yield and yield contributing traits was also observed by B application owing to decrease in panicle sterility. A linear increase in leaf and kernel B contents was observed with increase in B application rate. However, the range for an optimum B application rate is very narrow and increase of B application beyond 1 kg ha^?1 was toxic. In conclusion, soil application of B is an effective way to decrease panicle sterility and increase the kernel yield and grain B enrichment in rice.     

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

We 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.