Single Superphosphate Fertilizer Research Articles

Application of different phosphatic fertilizers influences the different phosphorus fractions and morphophysiological traits of wheat in saline sodic soil

Nutrient constraints in salt-affected soils are one of the limiting factors for crop production. We investigated phosphorus (P) availability to wheat crop and its correlations with different fractions of P in salt-affected soils in response to various phosphatic fertilizer’s application. Three different types of soils having electrical conductivity of soil extract (ECe) < 4 dS m−1 and sodium adsorption ratio (SAR) < 13.2 (mmol L−1)1/2, ECe 8 dS m−1 SAR 20 (mmol L−1)1/2 and ECe 12 dS m−1 and SAR 30 (mmol L−1)1/2 were used for this experiment. Different P fertilizers viz. control, diammonium phosphate (DAP), single super phosphate (SSP) and nitrophos (NP) were applied on these soils. The doses of nitrogen, phosphorus and potassium were remained same for all the treatments. The P fractions, agronomic parameters and P-availability to plants were determined. Results indicated increase in shoot dry weight (61%) and photosynthetic rate (9%) in SSP treated soil at EC 8 dS m−1 and SAR 20 (mmol L)1/2. The total P (7.6%) in soil and respiration rate (1.9%) in plant was recorded maximum in DAP treated soil at EC 8 dS m−1 and SAR 20 (mmol L)1/2, and membrane stability index (44%) in plant shoot, extractable P (23%) in soil and P concentration (22%) in shoot were recorded maximum in SSP treated soil at EC 12 dS m−1 and SAR 30 (mmol L)1/2. It was concluded that SSP fertilizer perform better in salt-affected soil for growth and yield of wheat compared to other phosphatic fertilizers.

Magnesium-doped biochars increase soil phosphorus availability by regulating phosphorus retention, microbial solubilization and mineralization

Despite fertilization efforts, phosphorus (P) availability in soils remains a major constraint to global plant productivity. Soil incorporation of biochar could promote soil P availability but its effects remain uncertain. To attain further improvements in soil P availability with biochar, we developed, characterized, and evaluated magnesium-oxide (MgO) and sepiolite (Mg4Si6O15(OH)2·6H2O)-functionalized biochars with optimized P retention/release capacity. Field-based application of these biochars for improving P availability and their mechanisms during three growth stages of maize was investigated. We further leveraged next-generation sequencing to unravel their impacts on the plant growth-stage shifts in soil functional genes regulating P availability. Results showed insignificant variation in P availability between single super phosphate fertilization (F) and its combination with raw biochar (BF). However, the occurrence of Mg-bound minerals on the optimized biochars’ surface adjusted its surface charges and properties and improved the retention and slow release of inorganic P. Compared to BF, available P (AP) was 26.5% and 19.1% higher during the 12-leaf stage and blister stage, respectively, under MgO-optimized biochar + F treatment (MgOBF), and 15.5% higher under sepiolite-biochar + F (SBF) during maize physiological maturity. Cumulatively, AP was 15.6% and 13.2% higher in MgOBF and SBF relative to BF. Hence, plant biomass, grain yield, and P uptake were highest in MgOBF and SBF, respectively at harvest. Optimized-biochar amendment stimulated microbial 16SrRNA gene diversity and suppressed the expression of P starvation response and P uptake and transport-related genes while stimulating P solubilization and mineralization genes. Thus, the optimized biochars promoted P availability via the combined processes of slow-release of retained phosphates, while inducing the microbial solubilization and mineralization of inorganic and organic P, respectively. Our study advances strategies for reducing cropland P limitation and reveals the potential of optimized biochars for improving P availability on the field scale.Graphical

Assessing phosphorus recovery from anaerobic digestion effluent of tapioca starch processing in a pilot – scale fluidized – bed homogeneous crystallizer: Effects of operation modes

This present study aimed to investigate the effects of two crystallization operation modes, batchwise operation (BO) and continuous operation (CO), on P recovery efficiency and characteristics of precipitates in a pilot – scale fluidized – bed homogenous crystallizer, using real anaerobic digestion (AD) effluent derived from tapioca starch processing as influent. Characterization techniques, including SEM – EDX, powder XRD, profile – matching, FT – IR, and crystal size distribution (CSD) analysis, were employed to identify phase compositions. Additionally, the purity and %P content of the target product were quantified using principles of hierarchical equilibrium thermodynamics and elemental analysis. As a result, the highest P recovery efficiency was 72.5 % for BO and 83.2 % for CO at a pH of 9 and a mixing rate of 400 rpm. Phase identification results revealed that struvite formed with Ca – rich solids, such as hydroxyapatite (HAP), notably exhibited higher impurity levels originating from CO modes. Precipitates from BO modes predominantly held 65 – 75 % struvite, with %P content ranging from 7.4 to 13.1 % — surpassing that of single superphosphate fertilizer (SSP, 18 – 22 % as P2O5), resulting in a suitable process in this study. Moreover, results obtained from the cost – benefit analysis (CBA) highlighted that BO scenario had economic viability (NP +0.05 to +1.53) with an estimate production cost of 3.47 USD/kg Premoved. Hence, the findings not only indicated that real AD effluent is suitable for P recovery, yielding high – quality struvite products, but also contribute to understanding the nuanced impact of crystallization modes on recovery yields and characteristics. This insight is invaluable for optimizing the process, leading to environmental benefits through reduced P and nitrogen discharge.

Enhancing chemical phosphorus precipitation from tapioca starch anaerobic digestion effluent in a modified pilot-scale fluidized bed reactor

This study aimed to evaluate the possibility of P precipitation as struvite from real anaerobic digestion (AD) effluent of tapioca starch processing. The results showed that at a pH of 9, and without Mg:P molar adjustment, P recovery was at 85%. The percentage of P recovery was increased to 90% and P contained in precipitates was at 11.80–14.70 wt% P, which is higher than commercial single superphosphate fertilizer (SSP, 18–22 wt% P2O5). This was achieved by controlling mixing at 200–400 rpm and upflow velocity at 50–200 cm min−1 inside a fluidized bed reactor (FBR). Based on SEM-EDX, powder XRD, phase identification by profile matching, and FT-IR analysis, the results demonstrated that recovered precipitates formed struvite predominantly. In addition, results of the woodchip ash additions and the one-way ANOVA based-RSM analysis revealed that mixing, the solution pH, and the woodchip ash intensely affected P recovery with the optimum condition found at 400 rpm, pH9, 4 g L−1, respectively. Ash addition enhanced P recovery efficiency but decreased the product's purity. Total costs of P recovery varied considerably from 0.28 to 7.82 USD∙(kg P)−1 depending on chemical consumption and %P content in recovered products. Moreover, the total cost was reduced by 57% from 7.82 USD∙(kg P)−1 (profit margin: −4.30 to −2.82) by a single mixing operation to 3.35 USD∙(kg P)−1 (profit margin: +0.17 to +1.65) employing coupling effect of mixing and Vup. The results indicate that P recovery from tapioca starch AD effluent not only provides a good-quality alternative slow-release P fertilizer, but also helps to curtail environmental problems due to excessive P and nitrogen discharge. These findings also demonstrate the ways of recovering nutrients from an abundant renewable resource that are relevant to simultaneous waste utilization during pollution controls.

Influence of Manures on Some Soil Fertility Properties, Yield and Agronomic Efficiencies of Soybean (Glycine max) on Degraded Acid Soil

Aluminum toxicity is a major limitation to leguminous crop production in acidic soils but mineral and organic fertilizer applications could ameliorate the condition. Thus, the focus of this study was to evaluate the influence of manures on post-harvest soil fertility quality, yield and agronomic efficiencies of soybean (Glycine max). The study had six fertilizer treatments: poultry manures, rabbit manures, pig manures, sheep manures, cattle manures, single super phosphate and the control (no soil additive) laid in a Completely Randomized Design (CRD), with four replicates. The experiment was conducted at the greenhouse of the Wesley University, Ondo, Nigeria. The treatments were applied at the rate of 40 kg P205ha-1 and the effects of treatments on yield parameters (biomass, grain yield and total dry weight), relative agronomic efficiencies, as well as soil fertility status were observed. Data analysis using ANOVA at 5% level of probability showed the application of poultry manure to have enhanced soybean grain yield and yield component. Poultry manure treatment had the highest mean total dry weight of 11.5 g while SSP resulted in the lowest yield (4.7g). The efficiency of available P released from the applied poultry manure was 2 times higher than the referenced single super phosphate fertilizer in Ondo. Poultry manure application again had higher RAEDSW than to chemical fertilizer. Thus, applications of poultry or pig manures at 40 kg P205ha-1 could be excellent materials as alternatives to mineral fertilizer (single super phosphate) for improving soil fertility, yield of soybean and its agronomic efficiencies.

Growth and Yield Response of Groundnut (Arachis hypogea L.) to Inorganic Fertilisers at Luyengo, Middleveld of Eswatini

Groundnut is an important food and cash crop for smallholder farmers in Eswatini. However, its yield is very low partly due to poor soil fertility particularly calcium and phosphorus deficiencies associated with soil acidity. Thus, a field experiment was conducted to determine the effects of different inorganic fertiliser types on growth and yield of groundnut. The treatments were: a control with no fertiliser, [2:3:2 (22) at 300 kg ha-1], single superphosphate (100 kg ha-1), calcium nitrate (120 kg ha-1) and a combination of calcium nitrate (120 kg ha-1) and single superphosphate (100 kg ha-1). A randomised complete block design (RCBD) with three replications was used. Results showed highly significant (p&lt;0.01) differences among the fertiliser types on most of the growth parameters recorded. At 90% flowering, significantly highest number of leaves per plant (48.3), the tallest plant (42.17 cm), the highest canopy width (41.47 cm), the highest number of branches per plant (6.57) and plant dry biomass per plant (20.6 g) were recorded for treatments with calcium nitrate followed by the application of combination of calcium nitrate and single superphosphate. Similarly, most of the yield components and yield were significantly (p&lt;0.05) affected by the fertiliser types. Significantly highest numbers of total pods per plant (28.8), mature pods per plant (26.9), dry pod yield (950.6 kg ha-1), hundred seed mass (82.8 g), shelling percentage (70.6) and seed yield (671.6 kg ha-1) were recorded from a combination of calcium nitrate and single superphosphate fertiliser. Thus, combined application of 120 kg ha-1 calcium nitrate and 100 kg ha-1 single superphosphate fertilisers can be used to increase the productivity of groundnut in the study area.

Soil fertility indices of tropical loamy sand as influenced by bambara groundnut variety, plant spacing and fertilizer type

Agricultural sustainability ensues when cultivation of field crops and associated techniques improve not just crop yields but also management-responsive soil properties. Bambara groundnut as an underutilized crop lacks research-based information on its agronomic requirements. This paper reports the key fertility indices of a loamy-sand soil in southeastern Nigeria as influenced by soil and agronomic management practices involving factorial combinations of two bambara groundnut varieties (Caro and Olokoro), two plant spacings (30 cm × 75 cm and 45 cm × 75 cm) and four organic/inorganic fertilizer options. These fertilizer options were NPK 15-15-15 (NPK), single super phosphate (SSP), poultry manure (PM) and Control. The plots under Caro variety spaced 30 cm × 75 cm and grown with NPK or SSP fertilizer showed the highest CEC (8.40 cmol kg–1) and exchangeable K (0.15 cmol kg–1), respectively. Olokoro variety spaced 45 cm × 75 cm and grown with PM or SSP gave the highest total nitrogen (0.14%), soil pHwater (6.35), available phosphorus (107.60 mg kg-1) and exchangeable Ca (3.70 cmol kg-1). The interactions plant spacing × fertilizer type and crop variety × fertilizer type affected all the soil fertility indices studied, while crop variety × plant spacing affected soil pHwater, available phosphorus, CEC and exchangeable Ca and Mg. Generally, as main factors, Olokoro variety, NPK and 45 cm × 75 cm improved soil properties better than their counterparts.

Path Analysis between Pest Occurrence and Nutritional Status of Soybean under Phosphate Fertilization.

The phytophagous insects select their host plants according to plant tissue nutritional quality. Thus, the objective of this study was to correlate the direct and indirect effects of phosphate fertilization on the nutritional status of the soybean crop and its relationship with the occurrence of insect pests. The effect of phosphate fertilization on soybean was evaluated using two phosphate sources, Single Superphosphate (SSP) and Monoammonium Phosphate (MAP), applied at five rates of P2O5. A sampling of insects initiated from stage V5 and was done weekly. Leaves were collected for nutrient analysis stage R1, in stage R9 was harvest was carried out. SSP or MAP phosphate fertilization in soybean affected the incidence of Chrysodeixis includens, Helicoverpa armigera, Elasmopalpus lignosellus and Euschistus heros. The plants treated with MAP had the infestation reduced compared with plants treated with SSP. Higher contents of Cu and Fe in the leaf reduces the incidence of insect-pests, whereas the opposite occurred with Mn. The occurrence of E. lignosellus reduced soybean yield. Therefore, the source and rates of phosphorus in soybean fertilization change the concentration of macro and micronutrients in the leaves and affect the behavior and incidence of pest species.

Use of single superphosphate fertiliser produced using Eppawala rock phosphate as a source of phosphorous for rice cultivation

Sri Lanka is an agricultural country totally depending on imported fertilisers for paddy cultivation. Importation of triple superphosphate fertiliser is a heavy burden on the country’s national economy. Hence, optimum utilisation of the locally available Eppawala phosphate deposit (EPD) will save a significant amount of foreign exchange. The objective of this study was to assess the effectiveness of locally produced Eppawala single superphosphate as a source of phosphate fertiliser for rice in comparison to triple super phosphate. Small tonnage of Eppawala single super phosphate (ESSP) was produced for the purpose of experiments using finely ground Eppawala rock phosphate (ERP: 90%

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

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

Standardization of Single Super Phosphate Fertilizer Formulation for Various Hazara Rock Phosphates

Standardization of Single Super Phosphate Fertilizer Formulation for Various Hazara Rock Phosphates

Acidithiobacillus thiooxidans IW16 and Sulfur Synergistically with Struvite Aggrandize the Phosphorus Bioavailability to Wheat in Alkaline Soil

Environmentally hazardous wastewaters from various origins could prove an impending source for phosphorus (P) recovery as struvite. This study aimed to employ an eco-friendly approach for P utilization from struvite, and to neutralize its alkaline effect in the soil through supplementation of sulfur-oxidizing bacteria (SOB) Acidithiobacillus thiooxidans IW16. Struvite precipitated and recovered from wastewater was tested for P release and bioavailability to grow wheat in alkaline soil under greenhouse conditions. Treatments were control (no P application), P from single superphosphate (SSP) fertilizer, P from struvite, P from struvite + sulfur (100 mg kg−1 of soil), and P from rock phosphate; and all these treatments were compared with and without SOB inoculation through irrigation water. Struvite application, especially with sulfur and/or SOB, maintained an adequate P level (as with SSP fertilizer) in both wheat plants and soil throughout the growing period. Wheat plant agronomic attributes were also improved with struvite as for SSP fertilization. Moreover, supplementation of SOB inoculum with struvite and other P sources significantly improved the P bioavailability and crop yield through increased phosphate solubility in alkaline soil. In conclusion, inoculation of SOB especially with sulfur (S) supplementation in struvite treatment caused the pH reduction of alkaline soil through S oxidation (H2SO4 formation), which solubilized the fixed-P in struvite as well as soil and thus improved P bioavailability to wheat plants. These findings strengthen the concept of struvite scavenging from wastewater for environmental safety, and to introduce it as an alternative resource for P fertilization.

Release of Heavy Metals from Dolomite Phosphate Rock after Activation with Organic Agent.

As high-grade phosphate reserves begin to diminish worldwide, low-grade phosphate rock such as that containing dolomite [CaMg(CO)] needs to be explored as a potential fertilizer. Activation of dolomite phosphate rock with humic acid substantially increased P availability by chelating Ca and Mg. However, the release potential of heavy metals during the activation process should be evaluated. In this study, an orthogonal experiment was designed to investigate the effects of major activating factors on the release of Cd, Cr, Cu, Mn, Ni, Pb, and Zn in activated fertilizers using a batch-equilibrium technique. The release potential of heavy metals from activated fertilizers was further compared with single superphosphate fertilizers made from the same dolomite phosphate rock. The activation process increased water-soluble Cr, Ni, and Zn by 39.8 to 65.7, 26.5 to 35.6, and 6.9 to 14.6 times, respectively, as compared with the original dolomite phosphate rocks, but there was a decrease in water-soluble Cd, Mn, Ni, Pb, and Zn by 1.4 to 5.4, 5.4 to 8.6, 2.3 to 3.7, 0.7 to 2.8, and 2.6 to 5.0 times, respectively, as compared with single superphosphate fertilizers. The release of heavy metals was affected by activating factors including dolomite phosphate rock type, particle size, humic acid dosage, and moisture content. Similar results were obtained with Mehlich-3 extraction, but levels of Mehlich-3-extractable heavy metals were less in activated fertilizers than in the original dolomite phosphate rocks, except Cu. These results indicate that activated fertilizers contain less bioavailable heavy metals than single superphosphate fertilizers and, therefore, are more environmentally friendly for application in agriculture.

Uptake of rare earth elements by citrus plants from phosphate fertilizers

Rare earth elements (REE) are a group of the periodic table formed by 17 chemical elements (lanthanoids plus yttrium and scandium). They have been used in different field applications. In agriculture, they can be found in some phosphate fertilizers at levels one or two orders of magnitude higher than those found in normal agricultural soils. Citrus plants are known to present high levels of REE when compared to most other species, however, there is little information about bioavailability of REE in phosphate fertilizers for citrus plants. This work focuses on the study of REE behavior by the application of increasing doses of single superphosphate fertilizer in Rangpur lime (Citrus limonia Osbeck) plants in a greenhouse study. The technique used was instrumental neutron activation analysis (INAA). The results showed that the fertilizer has caused significant increases in the content of REE in the citrus plant tissues, with higher concentrations in leaves than in branches. The highest substrate-leaf transfer factor was observed for La (0.0047), though the concentrations in the plants followed the same order found in the substrate, i.e. Ce > La > Sm > Eu > Sc. There was an increase of rare earth elements concentrations in Rangpur lime plants by superphosphate fertilizer application.

Efficacy of Manually Prepared Single Super Phosphate Fertilizer on Rain-Fed Wheat Crop under Sub-Humid Climate

Efficacy of Manually Prepared Single Super Phosphate Fertilizer on Rain-Fed Wheat Crop under Sub-Humid Climate

Influence of P-enriched compost application on economics and P use efficiency of a maize–wheat rotation system

Crop phosphorus (P) deficiency and poor utilization of added P is a major agricultural problem due to reduced solubility of soil P and rapid fixation or precipitation of applied P fertilizer in alkaline and calcareous soils. The effects of P-enriched compost and single superphosphate (SSP) fertilization on maize and wheat yields and P use efficiency in a maize–wheat rotation system were studied for three years. On a three-year average, grain yields of maize and wheat after application of P-enriched compost were increased by 18% and 24%, respectively, in comparison with sole addition of a recommended dose of SSP fertilizer. P-enriched compost addition to soil increased maize and wheat yields by 12% and 17%, respectively, compared to P fertilizer plus FYM incorporation. Soil available P concentration and P uptake were affected significantly by the addition of P-enriched compost. On average, increases in P recovery, use efficiency, and agronomic efficiency of 52%, 18%, and 43% were recorded in maize and increases of 50%, 23%, and 49% in wheat. P-enriched compost application yielded 30% and 32% higher economic returns in maize and wheat than SSP fertilization alone.

Fortification of Locally Developed Single Super Phosphate With Zinc Sulphate for Enhanced Zinc Nutrition to Maize Crop Under Calcareous Soil Conditions

A study was carried out in calcareous soil (low in ABDTPA extractable phosphorus and zinc) to evaluate the effect of zinc fortified locally developed single super phosphate fertilizers on maize grown in summer 2016. Zinc fortified fertilizers were prepared in laboratory of soil science department, University of Agriculture Peshawar, Pakistan. Treatments consisted of mixing two levels of zinc 5 and 10 kg ha-1 with SSP during its formulation by three methods of fortification coating, blending and reaction along with separate application and no application of zinc or a control treatment. Results showed the two levels of zinc mixed by different methods with SSP significantly influenced various appraised parameters of maize crop variety. With varying zinc level and fortification methods thousand grain weights, biomass yield and zinc concentration in leaves and grain were influenced significantly. Zinc at the rate of 10 kg ha-1 fortified with SSP through coating method produced maximum yield and yield components. Zn concentrations were higher in grains than leaves. It was concluded form the study that zinc (at the rate of 10 kg ha-1) mixed with phosphate fertilizer by coating produced highest maize grain yield and this method can be recommended for calcareous soil conditions of Peshawar.

English

Cowpea can obtain N through biological nitrogen fixation (BNF) through symbiosis with rhizobacteria. However, nodulation and BNF are influenced by edaphoclimatic factors that may bring about benefits or damages to the process, and the availability of nutrients is among the main factors that affect BNF and phosphorus (P). Thus, the present study aimed to determine the effectiveness of doses and sources of soluble P on nodulation, accumulation of nutrients, N and P absorption and use efficiency in cowpea plants inoculated with or without rhizobacteria. The experiment was conducted in a greenhouse at the Federal Institute of Education, Science and Technology, Rond&ocirc;nia, Colorado do Oeste-RO Campus, Brazil. The experimental design was randomized blocks in a 5 x 2 x 2 factorial arrangement, corresponding to five P rates (0, 20, &nbsp;40, 80 and 160 kg ha-1 of P2O5), two soluble sources of P2O5 [single superphosphate (SSP) and thermophosphate], absence and presence of inoculation, with four replication. The findings of this study show that inoculation with Bradyrhizobium sp. promotes increment in the dry matter production and increases N and P absorption efficiency in cowpea plants. The single superphosphate led to higher N and P absorption efficiency, production of shoot dry matter and production of nodules, when compared with thermophosphate. Inoculation with Bradyrhizobium sp. associated with SSP fertilization promotes higher P absorption efficiency in cowpea plants. Therefore, increase in P rates promoted increments in P concentrations in cowpea leaves. Key words: Vigna unguiculata (L.), Bradyrhizobium, phosphorus, fertilization, nutrition.

Velvet Bean and Cowpea Residual Effects on Maize Crop in Smallholder Farming Areas of Zimbabwe

On-farm research was conducted in Dendenyore Communal Land and Zana Resettlement areas of Hwedza District, Zimbabwe from 1999 to 2001. The objective of the study was to evaluate the effects of velvet bean and cowpea on growth and yield of maize in legume-maize rotation system. A total of 14 treatments, which consisted of forage legume and maize crops were examined. The experiment was established in a randomized complete block design with 9 replicates. On-farm sites were the replicates. The results show a significant residual effect of velvet bean and cowpea, when grown with single super phosphate fertiliser, on the maize stover and grain yield. They indicate significant phosphorus residual effects on a subsequent maize crop on sandy soils. Forage legumes contribute to residual soil fertility in fallen leaves and roots that increases yield of subsequent crops. The results also reveal that biomass production in perennial leys, grazed during the dry season, would be greater in the second season than in the establishment year. The results also indicate that in the velvet bean systems, especially green manure, nitrogen is lost very early in the season. This may lead to lack of synchrony between nutrient availability and crop uptake. The maize after green manure system had a nitrogen use efficiency of about 11 kg/kg of nitrogen applied. These results show the residual potential of forage legumes in reducing nitrogen fertiliser need for subsequent maize crops in mixed livestock-cropping systems.

Superphosphate fertiliser application and cadmium accumulation in a pastoral soil

ABSTRACTAt Winchmore, single superphosphate fertiliser has been applied annually to grazed pasture plots since 1949. To determine whether or not cadmium (Cd) in the fertiliser had accumulated in the soil, samples were collected at intervals (0–0.075, 0.075–0.15, 0.15–0.25, 0.25–0.50, 0.50–0.75 and 0.75 –1.00 m) to a depth of 1 m, the Cd concentration and bulk density measured and Cd density calculated. The relationship between Cd density and depth was curvilinear and the slope or curvature increased with increasing fertiliser application rate. Nearly 100% of the Cd stock was located in a depth of 0–0.5 m and 36% in the uppermost 0.075 m depth. Leaching calculations using Burn’s equation accurately estimated the measured Cd stock’s vertical distribution. Estimating the inputs to soils from fertiliser and atmospheric deposition and the loss by leaching and outwash accounted for the measured Cd stock. We concluded Cd accumulated in these soils at a rate determined by the fertiliser’s Cd concentration and application rate.