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BACKGROUND: Emergency medical services (EMS) personnel have already made substantial contributions to improving care for patients with time-dependent illnesses, such as trauma and myocardial infarction. Patients with sepsis could also benefit from timely prehospital care.METHODS: After training EMS personnel in recognising sepsis, we did a randomised controlled open-label trial in ten large regional ambulance services serving 34 secondary and tertiary care hospitals in the Netherlands. We compared the effects of early administration of antibiotics in the ambulance with usual care. Eligible patients were randomly assigned (1:1) using block-randomisation with blocks of size 4 to the intervention (open-label intravenous ceftriaxone 2000 mg in addition to usual care) or usual care (fluid resuscitation and supplementary oxygen). Randomisation was stratified per region. The primary outcome was all-cause mortality at 28 days and analysis was by intention to treat. To assess the effect of training, we determined the average time to antibiotics (TTA) in the emergency department and recognition of sepsis by EMS personnel before and after training. The trial is registered at ClinicalTrials.gov, number NCT01988428.FINDINGS: 2698 patients were enrolled between June 30, 2014, and June 26, 2016. 2672 patients were included in the intention-to-treat analysis: 1535 in the intervention group and 1137 in the usual care group. The intervention group received antibiotics a median of 26 min (IQR 19-34) before arriving at the emergency department. In the usual care group, median TTA after arriving at the emergency department was 70 min (IQR 36-128), compared with 93 min (IQR 39-140) before EMS personnel training (p=0·142). At day 28, 120 (8%) patients had died in the intervention group and 93 (8%) had died in the usual care group (relative risk 0·95, 95% CI 0·74-1·24). 102 (7%) patients in the intervention group and 119 (10%) in the usual care group were re-admitted to hospital within 28 days (p=0·0004). Seven mild allergic reactions occurred, none of which could be attributed to ceftriaxone.INTERPRETATION: In patients with varying severity of sepsis, EMS personnel training improved early recognition and care in the whole acute care chain. However, giving antibiotics in the ambulance did not lead to improved survival, regardless of illness severity.FUNDING: The NutsOhra Foundation, Netherlands Society of Internal Medicine (NIV).

Two separate pot trials were conducted at the research farm of the University of Pretoria to establish the efficacy of Black Urea as compared to normal urea and limestone ammonium nitrate as sources of nitrogen for maize (corn) fertilization. The aim was two‐fold: first to compare it as a banded nitrogen source, and second to compare it as a source of topdressed nitrogen at planting. In the first trial, the pots were not leached to establish the possible salt effects in the fertilizer band. In the second trial, the pots were leached to simulate normal field conditions. In both trials, Black Urea proved superior to normal urea.

The standard procedure in field experimentation is to use a randomized complete block (RCB) design, striving for the most homogeneous conditions as possible among plots in the same block. However, geostatistical concepts dictate that a spatial dependence exists for observations of a particular property, where closely spaced are more similar than those taken at a greater distance. The present study was conducted on an 18 ha lucerne (Medicago sativa) stand in which a 113 m X 145 m experimental area was demarcated. To determine spatial characteristics of soil and plant properties, 48 sampling points were selected using a 20 m square grid with an additional 75 points on a 2.5 m grid at five random node points. A RCB design trial was superimposed on the geostatistical grid design and consisted of seven pseudo (i.e. non-existent) treatments, replicated four times. Soil and plant samples were taken in June 2001 at all sampling points and plots and analyzed for various properties, including green biomass...

The farming community in the Mlondozi district in the Mpumalanga Province of South Africa has been part of a government liming intervention with the objective to ameliorate the serious soil acidity problem in the district. The current study was undertaken in order to evaluate the impact of the liming intervention and the risk of reacidification of the soil due to natural and agricultural activities. Acid production in the 0-250 mm depth varied from a measured 0.21 to 10.31 (mean 3.70 kmol H + ha -1 year -1 ) in crop production sites. Approximately 190 kg lime ha -1 yr -1 is required to maintain current soil pH levels under crop production. The rate of pH decline for the top 0-250 mm depth was between 0.051 and 0.918 (mean 0.237) pH units year -1 . In the absence of remedial lime applications, pH(H2O) values in most of the area are projected to decrease to the critical value of 5.68 or lower within 4 years. The upper and lower critical pH(H2O) were found to be between ca. 5.73 and 5.68. Below the lower critical value a reduction in crop production can be expected and above the upper critical value, accelerated acidification takes place. Soils with an extractable Al and acidity of

In this study, the soil buffer capacity (soil BC) was measured for 80 topsoil samples of the most dominant soil forms in a small-scale farming area. Soils used in the study ranged from weakly to strongly buffered, with soil BC values ranging from 0.12 to 2.23 cmol (+) kg -1 pH unit -1 . Relationships of soil BC over limited pH ranges showed that at soil BC(pH organic C > clay. At soil BC(pH4.5-6.5) the buffering mechanism was extractable Al > clay > CBD-Al > organic C > CBD-Fe. The main buffering mechanism between pH 6.5-8.5 was clay > CBD-Fe, organic C > CBD-Al. At the general pH range of buffering (4.5-8.5), clay > organic C > extractable Al > CBD-Al > CBD-Fe were the main buffering mechanisms. The main soil forms, viz., Clovelly and Hutton, tended towards lower soil BC, extractable Al (or acidity) and acid saturation, and higher pH, extractable Ca and Mg values, compared to the Magwa and Inanda soil forms which had higher soil BC but lower extractable Al (or acidity), pH and extractable Ca and Mg levels. Clovelly soils tended to have lower clay, CBD-Fe and CBD-Mn contents than the Hutton soils in the study area.

The use of dialysis membrane tubes filled with hydrous ferric oxide (DMT‐HFO) solution has recently been reported as an effective way to characterize phosphorus (P) desorption over a long term in laboratory studies. However, the DMT‐HFO method, similar to other soil tests, exploits 100% of the sample volume, which is much more than what the plant roots can exploit under natural conditions. One possible solution to mimic the root P uptake better by this method could be to modify the shaking procedure using different shaking periods. The objectives of this study were to investigate the influence of variable shaking times on the rate of P desorbed by the DMT‐HFO method and to relate the desorption indices generated with maize yield in a diferential P fertilizer trial. The effect of varying shaking options on the extractable DMT‐HFO‐Pi for the different P treatments showed a significant difference only for treatment MNPK. Significant correlations were obtained between the labile pool rate coefficients [kA1 (0...

Many agricultural fields that have received long-term applications of phosphorus (P) often contain levels of P exceeding those required for optimal crop production. Knowledge of the effect of the P remaining in the soil (residual effect) is of great importance for fertilization management. Plant P availability of residual P in soils is usually estimated using successive cropping experiments carried out in field or greenhouse studies. As this approach is very expensive and time consuming, more rapid soil test methods that can approximate this biological measure are required. The objective of this paper was to use a different approach to evaluate P availability (desorption) over a long period of time instead of the classical means of extraction. Thus, a modified sequential P extraction procedure using dialysis membrane tube filled with ferric hydrate solution (DMT-HFO) was used on the long-term P fertilized soils that received differential P treatments (PoLo, P1L1 and P2L1) to determine the changes...

In an attempt to characterize the phosphorus (P)–supplying capacity of a soil and to understand the dynamics of soil P, a procedure was followed whereby consecutive extraction procedures were carried out on a soil sample, first by dialysis membrane tubes filled with hydrous ferric oxide (DMT‐HFO), followed by subsequent P fractionation procedure. However, this combined method is lengthy and time‐consuming, and an approach to shorten these P desorption studies in soils was important. The major objective of this article, therefore, was to present a shortcut method as an alternative approach to the combined fractionation method. Comparison of the sum of DMT‐HFO‐Pi, sodium bicarbonate (NaHCO3)‐Pi, sodium hydroxide (NaOH)‐Pi, D/hydrochloric acid (HCl)‐Pi, and C/HCl‐Pi extracted by a conventional step‐by‐step method with the sum of DMT‐HFO‐Pi and a single D/HCl‐Pi extraction as a shortcut approach for all extraction periods resulted in a very strong and significant correlations. Both these methods were...

Knowledge on the availability of residual P in soils is of great importance for fertilization management. The use of dialysis membrane tubes filled with hydrous ferric oxide solution has recently been reported as an effective way to characterize P desorption over long-term laboratory studies. However, there is relatively little information relating the desorption indices of this method to plant parameters. The objective of this research was to relate the kinetic data generated using the DMT-HFO method to shoot dry matter yield of maize grown under greenhouse conditions. Accordingly, the labile pool rate coefficient (kA) showed a highly significant correlation with both shoot dry matter yield (r = -0.994**) and plant P uptake (r = -0.982**). The less labile rate coefficient (kB) also showed a significant correlation with both shoot dry matter yield (r = -0.856**) and P uptake (r = -0.893*). The correlation between the cumulative P extracted and shoot dry matter yield was highly significant. A strongly significant correlation was also observed between Bray 1P and shoot dry matter yield. Judging from the r-values, both the kinetic parameters and the cumulative amount of P desorbed could serve as reliable indices of plant available P revealing the effectiveness of this method in estimating the availability of residual P in soils. However, assessment of the reliability of this method at field level is important. Data from a wider range of soils is necessary to evaluate the universality of this method.

The concept of Precision farming is not new, and interest in the potential benefits gained momentum in the late eighties. The high cost of soil sampling and chemical and physical analysis by conventional laboratories has restricted the full implementation of this technique at the field level. Near infrared reflectance (NIR) could be a cost‐effective solution. Soil properties that have been calibrated include gravimetric soil water, clay content, buffer capacity, pH, electrical conductivity, titratable acidity, organic matter, mineralizable nitrogen, potential ammonia volatilization from urea, potential nitrification rate, and urease activity. A whole paradigm shift in philosophy is needed in soil testing to move away from the traditional approach of taking a perceived‐representative sample, in which all the spatial variation is lost, to using a combination of grid soil sampling at a sample intensity of 4 to 10 cores per ha and analysed separately using rapid but less accurate methods such as NIR.

The chemical transformations of applied and residual soil phosphorus (P) into different pools in two soils [Alfisols], a red sandy clay soil [Haplo‐Palcustalfs] from Rustenburg, which is a high P fixing, and a red sandy loam soil [Pale‐Xerults] from Loskop, a low P fixing were examined after treatments with different P rates (0, 25, 50, 100, 150, and 200 mg kg−1) and incubation periods (1, 60, 120, 180, and 240 days) under laboratory conditions. A sequential P extraction procedure was carried out on each treatment combination to determine the changes in 1) soluble and labile, 2) adsorbed, and 3) occluded and residual P pools in each soil. By fractionating soil P into different pools, it was possible to observe the transformation and distribution of added and initial soil P into different pools after each incubation period. Although solution and labile P decreased with time of incubation, there were corresponding increases in adsorbed, occluded, and residual P. Loskop soil had more marked increase...

Application of sewage sludge to agricultural land is an economical and effective way to dispose of sludge. There are several beneficial as well as potentially detrimental effects when sludge is applied to soils. One important aspect is the danger of nitrate (NO3 −) leaching. Strict guidelines exist in South Africa concerning sludge disposal in terms of N application rates, but none for commercial fertilizer application. To evaluate the potential risk of NO3 − leaching from sewage sludge and commercial fertilizer, an incubation trial was carried out. The rate at which inorganic N became available from sludge and fertilizer was measured and compared. NH4 + concentration peaked after 7 days and NO3 − concentrations in the sludge treatment increased steadily up to 63 days. The rate of nitrification was initially faster in the fertilizer than in the sludge treatments, but overall, the sludge produced more NO3 − due to mineralization compared to commercial fertilizer. A higher risk of NO3 − leaching ex...

The history of standardization of analytical procedures, especially for soil analysis in South Africa, is discussed, as is the evolution of the quality assurance schemes currently in use by the Agricultural Laboratory Association of South Africa (AgriLASA). Schemes currently comprise soil, fertilizer, and plant material (two samples of each on a monthly basis), animal feeds, growth media, and irrigation water (two samples of each on a bi‐monthly basis). Reporting is done electronically, by fax and by post. Laboratories are encouraged to use at least two of these media to ensure timely receipt of results. The International Harmonized Protocol for Proficiency Testing of Chemical Analytical Laboratories, developed jointly by the AOAC International, ISO 1 and the International Union of Pure and Applied Chemistry (IUPAC), was adopted for statistical analysis of results using the following procedure: Laboratories do a single analysis or analyze in duplicate or triplicate as they would for a routine sam...

According to literature, the mechanism of P acquisition by roots is mainly through interception. Sufficient P uptake is only ensured by proper root development. Pot and field experiments were conducted to determine the percentage “exploitation” or “utilization” of the soil volume by roots and to study the influence of P on Zea mays root growth. For the two pot trials, four P levels (0, 20, 40, and 80 mg kg−1) were used, with additional N (100 kg ha−1) and K (75 kg ha−1). The field trial consisted of a high‐P (Bray‐1: 70 mg kg−1) plot and a low‐P (Bray‐1: 7 mg kg−1) plot, sampled to a depth of 80 cm. The Gompertz function was used to describe exploitation by roots as influenced by P application. Less than 5% of the soil volume was exploited by the root system for the pot and 0 to 10 cm depth in the field trial, with

Growing input cost in extensive and intensive agriculture production systems, as well as growing concern about environmental pollution in intensive production systems (e.g., the growing cut flower industry in southern africa) will force farmers in developing countries to reevaluate conventional approach to fertilization programs. Phosphate (P) desorption characterisation of soils under cultivation, to determine the time frame of applied P release, can be used to optimize fertilizer P programs. The desorption kinetics of residual and applied P to an acid sandy clay soil were investigated over 56 days using hydrous ferric oxide in dialysis tubes as a specific P sink, followed by a sequential P fractionation. P desorption kinetics were described with a two‐component first‐order model. Assumptions made were that two discrete P “pools”, (a labile P pool [SP A ] and less labile P pool [SP B ]), participated in the desorption process and that P release from the two soil pools follow first‐order kinetics...

In general, agricultural fields are managed as uniform units, ignoring spatial soil heterogeneity and its effects on growth and yield of field crops. This study was conducted from June 2001—February 2002 and examines the effects of spatial variation of soil properties on the winter yield of a two-year-old lucerne stand on two soil types using geostatistical procedures. Seventy-two sampling points (nodes) were laid out on a 20 m square grid, with an additional 90 sampling points laid out on a 2.5 m square grid at six randomly selected node points to ensure that the total spatial structure would be identified. From initial soil sampling and analyses, the two experimental soils were classified as belonging to the Stella and Pyramid soil families with inter alia mean clay contents of 45% and 46%, pH(H2O) values of 7.8 and 8.8, and mean P status (Ambic) contents of 18.3 and 6.4 mg kg−1 respectively. Green biomass lucerne yield was determined on six occasions at all nodes, while soil sampling (0–300 mm layer) a...

In general, agricultural fields are managed as uniform units, ignoring spatial and temporal relations between plant element uptake and yield. This study was conducted from June 2001 to February 2002 on a two-year-old lucerne stand and explores the spatial relationships between nutrient uptake and green biomass yield during both winter and summer growing seasons, as well as the temporal variation of lucerne yield during a growing season using geostatistical procedures. Green biomass yield was determined on six occasions at 162 sampling points across the field. The plant samples of both the June and February harvest were analysed while the soil was only sampled and analysed once in June 2001. Although the lucerne stand contained on average adequate concentrations of Ca, Mg, P and K, areas of K deficiency did occur in the field during both the winter and summer seasons. Weak linear correlations existed between plant elements and yield. Similarities were discernable between winter and summer spatial variation...

Priming, induced through the addition of oxidisable organic matter, releases or immobilises nitrogen and other nutrients in the soil. Moisture plays a very important role in priming as it stimulates microbial activity after a dry soil is wetted, especially with the addition of organic material and reduced mineral nitrogen fertilisers. This phenomenon was observed in the incubation experiments with different organic material and mineral fertiliser additions. The resulting graphs could be divided into three phases: Phase 1—nitrogen flush; Phase 2—growth; and Phase 3—depletion and expiration. Ammonium-nitrogen can be available for plant uptake two days after fertiliser application if a dry soil is wetted. When organic matter is added to soil, microbial activity is stimulated and immobilisation of ammonium can take place. The ammonium can be released later in the season for plant uptake, thus regulating its availability.

Ceramic samplers are used to extract soil solutions at different depths from the soil profile for chemical analysis. The advantage of this method is that samples can be taken at any time provided that the soil water potential is high enough to allow extraction of the water from the soil. An investigation was conducted to determine to what extent the CEC (cation exchange capacity) and selectivity coefficients of the samplers might influence the chemical composition of the water samples collected. This was due to criticism that the accuracy of the method may be influenced by the CEC of the samplers. The CEC of four Soil Moisture ceramic cup soil water samplers was determined. Two of these samplers had previously been installed in the field and two were new. The CEC of the sampiers did not vary much, although the used samplers had higher CEC values, which were ascribed to the contribution of clay particles contaminating the ceramic material. Selectivity coefficients for different cation combinations were cal...

In a trial to test the bioavailability of certain heavy metals from slags, twelve liming materials (including different slags) were applied at three different rates to an Acrisol (sandy loam, pH(Water) of 5.2 and CEC of 4 cmolc kg−1) from the South African Eastern Highveld. Two Ca(OH)2 incubations were done on the specific soil—one in a soil to solution ratio of 1:1 before the trial and another in a soil to solution ratio of 1:2.5 on the control treatment soil after the trial. The Calcium Carbonate Equivalents in HCl (CCE) and RH-values (Resin Suspension Method) were determined for each lime before the trial. After an incubation period of three months, the pH(Water) and pH(KCl) of each of the four replicates for every treatment was measured. An incubation curve and regression equation was drawn up for each lime using the average pH values. Lime recommendations for each lime to target pH-values of 5.8, 6.8, and 7.8 were modeled using the CCE and RH-values as well as the values from the two Ca(OH)2 incubati...

A study was conducted in a long-term field experiment initiated in 1939 at the University of Pretoria, South Africa. The aim was to assess the long-term effect of direct N and K and residual P fertilizers on chemical and microbial properties of soil and grain yield of maize in rotation with field pea. Long-term fertilization resulted in decreased total organic C (TOC) and basic cation contents, and had an acidifying effect on soil. The decrease in TOC was greater in simple fertilizer treatments (N, P, or K) whereas basic cation contents and pH declined more in balanced fertilizer treatments (NPK). Levels of total N were higher in the balanced than in simple fertilizer treatments. Soil microbial biomass and numbers of bacteria, actinomycetes and fungi were influenced by, and exhibited qualitative changes in response to, long-term fertilization. Crop rotation also exerted effects on chemical and microbial properties of the soil. Maize grain yield showed significant increases due to balanced fertilizer treatments. Responses of maize to simple fertilizer applications were not beneficial in terms of yield returns. The results suggested that judicious use of inorganic fertilizers may, in the long-term, maintain soil quality and productive capacity.

A study was conducted in a field experiment that has been ongoing for over 60 years at the University of Pretoria, South Africa. The aim was to compare the residual effects of manure and NPK fertilizers on selected soil nutrients, microbial properties, C and N inputs, maize tissue nutrient concentration and yield under long-term crop rotation. Total organic C, total N and available P levels were increased owing to residuai effects of manure alone or in combination with NPK fertilizers. C input in NPK-fertilized plots was about 47% higher than in manured plots. The estimated fixed N ranged from 52 kg ha−1 in the NPK plots to 164 kg ha−1 in the control plots. Increases in nutrient contents of manured plots were not reflected in microbial properties of the soil. Microbial biomass and numbers were generally higher in the NPK-fertilized than in the manured plots. The differential responses were attributed largely to differences in decomposability of organic materials. Organic material in the NPK treatment appe...

A study was conducted on a long-term field experiment at the University of Pretoria, South Africa, that was established in 1939. The aim was to investigate the effects of residual manure on the characteristics of the total and microbial biomass and their nutrient contents in the soil and on maize yield under long-term crop rotation. It was found that total C, N and available P levels were increased as a result of manure application. Seasonally, these nutrients exhibited variations that appeared to be related to influences of crop rotation. Long-term soil N content in an adjacent native site remained relatively constant while it tended to increase in the control and manured plots. Soil microbial biomass content of C, N, and P and microbial populations were affected by previous manure application, as well as by crop rotation. The biomass and numbers of microflora were generally higher in the manured plots. Manure application also resulted in higher maize yields and had substantial residual effects. Relation...

Soil sampling by conventional methods as applied in the Republic of South Africa, provides average values. These are valuable for mapping to give an indication of general fertility. The time of sampling generally after the crop has been removed from the field is also not ideal. Values obtained vary markedly from values obtained during planting. In systems where fixed cultivation practices are followed (band placement of fertilisers and row crops) zones of concentration are created in the rootzone that have no resemblance to averages. Acid zones with general lower fertility that are created in this manner are permanent and where crops are subsequently planted in the same position, the intensity of the acidification is enhanced. In time this can cause plant growth in this zone to become impossible. Soil sampling as an aid in fertilisation programme planning requires that the spatial variation must be known. More regular sampling (annually) and possibly throughout the season, on a smaller area, that is representative and part of the system, will give the pattern of variation in the particular field. It must be stressed that acid soils require normal liming if the pH (H 2 O) is below 6. Acid zones in these soils formed by bandplacement of reduced nitrogen require much higher applications. The mixing of coarse amorphic lime with the fertilisers that are bandplaced can alleviate this. Possible advantages, for example, could be: effectiveness of fertilisers applied on low pH soils, is increased; chemical environment in the root zone is improved; stimulation of beneficial microflora; effectiveness of band applied herbicides may be improved; a strong tendency towards higher yields. No harmful effects were encountered in a study of these aspects. Unavailability of P due to the formation of less soluble Ca-phosphate as well as Zn-interactions are some of the theoretical possibilities, although none of these were encountered. Addition of coarse lime to fertilisers that are bandplaced, is a safe and affordable procedure.

AgriLASA (Agri Laboratory Association of Southern Africa) has 75 member laboratories participating in quality audits that service different sector's in Agriculture, Horticulture and Environmental needs. Most laboratories are fairly small and only render a limited service. In 1968 Government and the private sector agreed to rationalise and centralise laboratory services in SA. As frequently happens the ideal did not prevail and soon afterwards everyone reverted to doing their own thing. In 1996 the major role players in the private sector re‐evaluated their positions and as the trend to convert from Co‐operatives to Companies gathered momentum, pressure on laboratories to become self‐reliant increased. A complicating factor had always been that Government, to a large extent, subsidised analytical services in Agriculture. The first major amalgamation occurred with the combining of the laboratories of Northwest Co‐operative, Outspan International (Previous Citrus Exchange) and the in‐house feed labo...

Curbing soil erosion is essential to ensure the sustainable use of land within the Lesotho Highlands Water Project (LHWP) catchments. This study aimed (a) to produce initial soil loss modelling results in order to depict the distribution and extent of erosion in the catchment areas and (b) to use these models to screen different land use practices in order to eliminate those leading to unacceptable soil erosion rates. For modelling purposes, the catchment areas were subdivided into land facets, which served as a basis for soil loss prediction. Representative values of the factors considered by soil loss models were determined for each land facet and used as input data for the models. The SLEMSA, USLE and RUSLE models were subjected to theoretical evaluation and sensitivity analysis. The flexibility of the RUSLE model proved to be highly advantageous for application to the LHWP catchment areas. Potential soil loss displayed a distinct relationship with bio-physical and land use patterns. Long, ste...

ALASA is a non-profitable umbrella body for laboratories with agricultural relevance and was founded in 1993. Its mission is to promote the interests of member laboratories and to gain recognition for their services and to ensure the acceptable quality thereof. The main aims of ALASA are to establish and maintain standard analytical methods, promote the use of the standardized methods, rationalize methods, support and institute analytical quality assurance schemes and inter-calibration exercises and the promotion of accreditation of member laboratories. The main functions of ALASA are to liaison with interested parties, member laboratories and other organizations, to promote standardization and quality assurance, organization of suitable workshops, congresses and courses. ALASA is governed by its council consisting of a President, chairperson of the executive committee, secretary and treasurer. The elected chairperson and secretary of each sub-committee plus two additional members serve on the council. Currently the following sub disciplines are active: plants, soil and growth media, lime, fertilizer, feed, pesticide, water and wine. Sub-committees meet regularly to discuss and co-ordinate matters that concern the specific discipline and report back to the council. Problems which ALASA has encountered and which cause variation in analytical results are the incorrect application of methods, the use of different instrumentation and the use of non-standardized methods. Some of the main achievements of ALASA includes the compilation of standard analytical handbooks for soil (presently under revision), fertilizers and a combined book for plant and feed. Other achievements include the presentation of workshops where the correct methodologies for different methods, which cause reduced variation in the analytical results in the different control schemes, are discussed and explained.

Soil acidification under tropical and sub-tropical conditions is a well known phenomenon. Because of cost implications in practice it is important that the best available liming materials be used. Various methods have been employed to distinguish between the effectiveness of such materials, most based on the principle of calcium carbonate equivalent. Many of these use relatively strong acids for dissolution of lime, at concentrations far greater than ever actually occur in even the most acid soils. Because contact exchange between the acidified sites and the liming material is considered to be vital, a method in which a slightly acidified cation exchange resin is used was developed (the resin exchange method). This method has been used by several laboratories in South Africa that take part in the quality control scheme run by ALASA. Several problems were experienced in achieving reproducibility between laboratories, that were diagnosed as being due to variations in applications of the method and especially lack of discipline in using a standardized resin. This resulted in a number of independent investigations into reasons for this apparent lack of reproducibility. Reasons for this included inherent particle size distribution in the sub-samples of liming material, resin properties, water quality and electrode maintenance and calibration. Under standardized and controlled conditions the method proved to be eminently satisfactory. An alternative possibility that is being investigated is the use of an unbuffered acid topsoil to replace the resin. A bulk sample could be homogenized and subdivided to provide an adequate supply.

The changes in applied and residual phosphorus (P) were examined in Avalon and Clovelly soils under cultivation by using the P fractionation method of Hedley, Stewart and Chauhan (1982). Soil P was separated into six major fractions of which some fractions were subdivided into organic (Po) and inorganic (Pi) P forms: P extracted by an anion exchange resin (Resin-P); 0.5 M NaHCO3-P (NaHCO3-Pi and Po); 0.1 M NaOH (NaOH-l-Pi and Po); ultrasonication in 0.1 M NaOH at 75 watt (NaOH-ll-Pi and Po); 1.0 M HCI(HCI-Pi); and H2SO4 digestion and H2O2 oxidation, (H2SO4P). General trends in soil P were evident over 15 years of cultivation. Resin-P, NaHCO3-Pi, NaOH-l-Pi, NaOH-ll-Pi and HCl-Pi were reduced in the Avalon soil, while only the NaHCO3-Pi and NaOH-ll-Pi decreased in the Clovelly soil. It is hypothesised that NaOH-l-Pi, which showed the largest decrease, was mainly responsible for the replenishment of the labile P pool. In the Po fraction, NaHCO3-Po and NaOH-ll-Po decreased with time in the Avalon soil, in con...

The postmining rehabilitation of coastal sand dunes north of Richards Bay (28°43′S, 32°12′E), South Africa, is resulting in the development of a series of known-aged stands of vegetation dominated by Acacia karroo (sweet thorn). Other broad-leaved species are establishing themselves in rehabilitating areas more than 12 years of age. Soils from rehabilitating stands 3–5, 9–12, 13–15, and 16–18 years of age, from two disturbed, unmined stands 30 and 58 years of age, and from a mature unmined stand were examined to assess age-related trends in selected soil properties. Individually, these stands represent a series of different developmental stages of a coastal dune successional sere. Soil organic material, percentage organic carbon and concentrations of sodium, potassium, magnesium, calcium, and nitrogen increased with an increase in habitat regeneration age. Concentrations of most of these elements were lower than those recorded on the 58-year-old unmined and mature unmined stands. Multivariate analyses suggest, however, that the similarity of these values for rehabilitating stands to those for the unmined stands increased with an increase in regeneration age. The growth response of Raphanus sativus (radish) plants, based on mass attained under experimental growing conditions in soil collected from these stands, suggests an increase in soil fertility with an increase in regeneration age.

Saline soils pose a great problem to reclamation of mined areas in arid regions. Experiments were carried out in order to determine the tolerance of six Namaqualand pioneer species to varying levels of salinity. Both perennial and ephemeral species were used and results of all species showed that increased salinity induced a significant decrease in biomass production. With increased salinity, biomass allocation towards the leaves increased, while that towards the stems decreased in both perennial and ephemeral species, but biomass allocation towards the other plant organs varied. Of the six species tested, the perennials seemed to be better suited for rehabilitation purposes under saline soil conditions.

Although there have been various quality assurance schemes operative in South Africa for several years, efforts were largely fragmented and informal. Initially the Fertilizer Society of South Africa, together with representatives of Government departments, cooperatives, private laboratories, research councils, and universities met informally to discuss the analysis of materials of agricultural importance: soils, plant material, fertilizers, liming materials, animal feeds, and waters. The need for a more formal structure was long felt and it came to fruition with the formation of Agricultural Laboratory Association of Southern Africa (ALASA) in September 1993. Apart from a constitution, there is a central council comprising representatives of subcommittees representing the different disciplines. Although lots has yet to be put in place, it is confidently expected that this will go a long way to ensuring reliable analyses of materials of agricultural importance in Southern Africa.

Mining activities along the west coast of South Africa will lead to salinization of the soil if sea-water is used in the mining process. Laboratory studies were conducted to determine the influence of leaching depth and the amount and frequency of irrigation on the growth of Atriplex semibaccata R. Br. Leaching depth as well as the amount and frequency of irrigation had no significant effect on biomass production. However, the interaction between leaching depth and amount of irrigation did influence the biomass production of Atriplex semibaccata. Root:shoot ratio increased as the amount of irrigation decreased.

The removal of sodium and chloride from a saline-mined soil by Mesembryanthemum barklyi N.E. Br. was investigated under laboratory conditions. The sodium, magnesium and chloride content of plants increased when grown on a saline soil, while the calcium, potassium, nitrogen and phosphorus content decreased. No significant difference in biomass production occurred between plants grown on saline and non-saline sandy soils.

The effect of varying phosphorus (P) supply on the growth, yield, leaf abnormalities, and nutrient composition was investigated for three lettuce cultivars (Chaparal, Wintercrisp, and Robinvale) in sand culture and soil. The leaf P content for optimum yields varied between 0.40 and 0.90% while higher than 0.90% P seemed to cause leaf abnormalities in Chaparal and Winter‐crisp. With high P supply, more calcium (Ca) was necessary to overcome the detrimental effect of P. In soil, maximum yields were obtained with a P supply level of 540 mg/kg P, while higher levels caused yield reductions. Soil analysis at the end of the experiment showed that a soil P content of 250 mg/kg P (Bray II) was associated with the best yield. When additional Ca was supplied to the soil, yield reduction due to high P supply was reduced. The leaf abnormalities which coincided with the high P supply were similar to those which have previously been described for auxin‐type herbicide damage on lettuce.

Construction details of an inexpensive, portable rain simulator are given. The dismountable components are easily transported on a light truck. The flat spray nozzles used produced rain with a >90% coefficient of uniformity over a 1-m2 test plot. Drop sizes and drop size distributions were determined using a flour pellet method. The appropriate equation of motion for accelerating drops and drag coefficients were used to calculate the impact velocity of individual drops and the kinetic energy of rain produced by various nozzles. Rainfall intensity can easily be varied in the range 10–150 mm h−1 and water consumption is low.

In a solution culture experiment with wheat, the influence of withholding P at early growing stages as well as varying the P supply on the growth and P content were studied. Increasing the P supply caused increasing P concentrations in roots and tops. When P was withheld for short periods after transplanting the seedlings, some deficiency symptoms appeared, which disappeared when P was reapplied at a later stage. Withholding P for only one week caused a restriction in yield which was aggrevated when P was withhold for longer periods. The P content of plants recovered when it was reapplied after a period of withholding P and even became higher than the control which received P throughout the growing period. It was concluded that the P uptake rate was higher when P was applied after a period without P. This higher rate of P uptake and restricted growth caused P to concentrate in the top growth. This could be caused by any factor such as a cold spell, which restricts P uptake, even for a short perio...

Sulphur is an essential nutrient for the production of the amino acids cysteine and methionine, which are important for protein syntheses. Previous studies showed that sulphur deficiencies are becoming common because of the tendency to use more concentrated and liquid fertilisers. The objective of this study was determining the threshold concentration values for sulphur in different soils, above which no yield increase can be expected with increased sulphur fertilisation. Four soils, low in sulphur, were selected and treated with five sulphur levels. After four to five weeks the first deficiency symptoms appeared at the lowest sulphur levels. The plants were harvested after ten weeks. It was found that sulphur had a definite effect on yields and 10 mg kg-1 in soil can be used as a threshold value.

Two acid soil samples from South Africa were sent to Wageningen University, Department of Environmental Sciences (WEPAL). WEPAL performed the milling, homogenization and splitting of the samples using their specialized equipment. Homogeneity tests were also performed. One sample was a buffered soil from Natal and the other an unbuffered soil from Pretoria University's research farm. The unbuffered soil was sent through both WEPAL and AgriLASA's proficiency schemes. A comparison of the two systems regarding analyses and statistical reporting are given. South Africa has gone a long way in standardization of methodology as well as extractants used. On the normal standard analyses e.g., pH, P (BRAY1), Ammonium Acetate Ca, Mg, K and Na, there are sufficient laboratories reporting in order to provide meaningful statistical analysis. On other types of analysis, which are not frequently done e.g., micronutrients, CEC, other extractants for P and Cations, the need exists to be able to compare with more laboratorie...

The nutrient requirements of two new flowering bulbous plants, Ornithogalum and Lachenalia, were studied using a sand culture technique. For the short-season Lachenalia, sufficient nutrients must be supplied at an early growth stage. The long-season Ornithogalum requires a good nutrient supply over a longer period, for both vegetative and bulb growth. The P and K requirements for both genera are not very high but adequate K levels are important at an early growing stage due to the low K content of the bulbs. The same is true for N in the case of Lachenalia. However, the N content of Ornithogalum bulbs is high and a low N supply at the early growing stages had little effect on yield.

A sandy and a sandy clay-loam soil from two dedicated (sacrificial) sewage sludge disposal sites were incubated with a total lime equivalent of 45 Mg·ha-1. Both these soils were acidified (pH 4.0 to 4.2) and had a significant accumulation of organic material (organic C of 2.9 to 3.7 %) compared to non-polluted soils (organic C of 0.6 to 1.0 %). The limed soils did not attain the desired pH of 6.5 after 6 months\' incubation due to a high buffer capacity. After incubation, soil samples were taken from the incubated pots and the levels of Al, Fe, Mn, Cu, Zn, Pb and Cd were determined by atomic absorption spectrophotometry (AAS) after extraction with NH4-EDTA and BaCl2. Most of the metals extracted with BaCl2 (except Mn in the sandy soil and Cd in both soils) decreased after liming. The EDTA-extractable Mn, Fe, and Cd in both soils and Cu and Pb in the sandy clayloam soil increased after liming, whereas Al and Zn, decreased in extractability (Statistically significant differences could not be determined for the trial due to the trial not having been designed for the results that were obtained). Similar results were reported in the literature for EDTA metal extraction but the phenomenon was not elaborated upon, except for Cr. The increased extractability of some of the metals after liming could negatively influence the use of EDTA as an extracting agent in proposed heavy-metal guidelines for similar sacrificial soils. Should liming be considered as a strategy to decrease metal mobility in sacrificial soils, the observed increase in extractability becomes a cause for concern and should receive attention in further research. Water SA Vol. 31 (2) 2005: pp.271-274

The effect of varying P concentrations on the growth, yield and development of leaf abnormalities, nutrient content and uptake of other nutrient elements was investigated for lettuce.Three cultivars (Chaparal, Wintercrisp and Robinvale) were studied in sand cultures and soil. The frequency of changing the nutrient solution had an effect on the P level that gave the highest yields or which caused reduced yields and leaf abnormalities. The leaf P content for optimum yields varied between 0.4 and 0.9%, while higher P contents caused leaf abnormalities in Chaparal and Wintercrisp. With high P concentrations, more Ca needed to be taken up to overcome the detrimental effect of P. In soil, maximum yields were obtained with 540 mg kg−1 P applied. Soil analysis at the end of the experiment on these treatments showed that a P content of 250 mg kg−1 P (Bray II) coincided with the highest yields. Yield suppression due to high P concentrations was reduced when the Ca concentrations was increased. The leaf abnormalitie...

In a water culture experiment with wheat, the influence on growth and nutrient uptake of varying the P supply from 0,02 to 5 mmol H2P04 - dm-3 and the NH4 +:N03 - ratio from 0:15 to 12:3, with a Hoagland nutrient solution (No 2) as control, was studied. Poor growth due to low P supply was characterized by a higher root:top growth ratio than plants which received adequate P, indicating that under these conditions root development of wheat takes preference over top growth. Root P was also higher than top growth P with low P supply, indicating that wheat requires a certain level of P in the roots before P can be transported freely to the tops. It was postulated that N03 - reduced the detrimental effect on growth of high P supply by causing P to be precipitated as Ca3(P04)2 in the roots, while with high P and N supply, more Ca2+ is required for balanced nutrition. Increased NH4 + supply increased the P demand with added P apparently reducing the antagonistic effect of NH4 + on Ca2+ uptake. This is especially important in highly leached acid soil where the Ca2+ content tends to be low and fertilization early in the season should be carefully planned.

In 'n waterkultuureksperiment met koring is die invloed van verskillende P-toedienings (0,02 tot 5,0 me H2PO4 dm−3) en van verskillende NH4:NO3-verhoudings (0:15 tot 12:3) met 'n Hoagland-voedingsoplossing (no. 2) as kontrole bestudeer. Normale groei is reeds by 'n laer P-voorsiening (0,2 me dm−3) as die kontrole (1,0 me dm−3) verkry. Die hoogste P-voor-sieningsvlakke het opbrengs verlaag by die laagste NH4: NO3-verhoudings. Beter opbrengs is verkry met intermediare NH4:NO3-verhoudings, waarvoor hoer P-voorsiening noodsaaklik was. By hoe P-voorsiening het chlorose-simptome tussen die blaarnerwe voorgekom wat vererger het met hoer NH4:NO3-verhoudings. Plantontledings dui daarop dat behalwe by die hoogste NH4: NO3-verhouding, die chlorose-simptome toegeneem het met hoer P-status in die bogroei. Die teenoorge- stelde tendens het ten opsigte van die P-status in wortels voorgekom. By hoe P-voorsiening is dit moontlik dat NO3 die vervoer van P vanuit die wortels na die bogroei verminder en gevolglik die simptom...