Showing papers in "The South African Journal of Plant and Soil in 2005"
TL;DR: In this article, carbon storage in biomass and soils is examined in intact indigenous vegetation and under different land uses in thicket (250-400 mm mean annual precipitation), xeric shrubland (350 mm), karoo (250 mm), and grassland (900-1200 mm).
Abstract: Carbon (C) storage in biomass and soils is a function of climate, vegetation type, soil type and land management. Carbon storage was examined in intact indigenous vegetation and under different land uses in thicket (250–400 mm mean annual precipitation), xeric shrubland (350 mm), karoo (250 mm), and grassland (900–1200 mm). Carbon storage was as follows: (i) mean soil C (0–50 cm): thicket (T) = grassland (G) > xeric shrubland on Dwyka sediments (XS) > xeric shrubland on dolerite (XSD) > karoo (K) (168, 164, 65, 34 & 26 t ha−1, respectively); (ii) mean root C: T > G > XS = XSD (25.4, 11.4, 7.2 & 7.1 t ha−1); (iii) mean above-ground C including leaf litter: T>XS>G>K> XSD (51.6, 12.9, 2.0, 1.7 & 1.51 ha−1). Carbon stocks in intact indigenous vegetation were related more to woodiness of vegetation and frequency of fire than to climate. Biomass C was greatest in woody thicket and soil C stocks were greatest in thicket and grassland. Total C storage of 245 t ha−9 in thicket is exceptionally high for a semi-arid...
51 citations
TL;DR: Seeds of Cleome were found to be negatively photoblastic, and the phenomenon was more pronounced when the germination test was undertaken at 20°C and at light exposures of 12 h day−1 or longer; germination of photo-inhibited seeds was, however, improved by treatment with GA3.
Abstract: Seeds of Cleome (Cleome gynandra L.) are characterised by low germination and may require after-ripening. The dormancy characteristics and optimum conditions for seed germination of this species have not been explained. The objective of this study was to investigate the effects of temperature, light and pre-germination treatments (chilling, scarification, hydration and germination in the presence of KNO3 or GA3) on the germination of Cleome seeds. Seeds were germinated for 10 days and the final count of germination was used to determine seed performance. The highest germination percentage (60% and 80%, for a 2-year old and a 1-year old seed lot, respectively) of untreated seeds was achieved when alternating temperatures of 20–30°C (16 h—8 h) in the dark or constant 30°C in the dark were used. Among the pre-germination treatments, only scarification (puncturing of seeds at the radicle end) improved germination. Seeds were found to be negatively photoblastic, and the phenomenon was more pronounced when the ...
35 citations
TL;DR: Varieties ranged from pure Macadamia integrifolia, through hybrids of varying species proportions, to pure M. tetraphylla, and fall into at least seven major germplasm groups.
Abstract: Macadamia is an important horticultural crop of South Africa, and the major cultivars grown have a wide range of attributes. These cultivars originated from diverse backgrounds, but the genetic relationships between them are unclear. Here we describe new insights into the genetic identity, relationships, and species composition of 38 varieties of macadamia representing the diversity currently available within the macadamia industry of South Africa. The varieties were surveyed with the DNA marker system, RAF (randomly amplified polymorphic DNA). Varieties ranged from pure Macadamia integrifolia, through hybrids of varying species proportions, to pure M. tetraphylla, and fall into at least seven major germplasm groups. Local hybrid selections were genetically distinct from those of other selection origins. The cultivar 791 was unusual, identified as a tri-species hybrid containing a significant proportion of the wild species M. ternifolia. It was also shown that 741 u is the true 741 cultivar and 741s is ac...
27 citations
TL;DR: Smaller seeds were less sensitive to low water potential than large and medium seeds with respect to germination, but they may have less food reserves to emerge from deteriorating seedbeds.
Abstract: Sub-optimal crop emergence and establishment is a problem in crop production owing to low soil moisture. The effects of seed priming (seed soaking) on cotton and maize germination at different water potentials (0, −10 kPa, −100kPa, −200 kPa, −500 kPa and −1500 kPa) were determined in laboratory experiments. The interaction of these treatments with cultivar was studied in cotton (CY889 and SZ93–14), and with seed size in maize (small, medium and large seeds of CG4141). Germination of cotton decreased progressively as water potential was lowered, but non-primed cotton seed was more sensitive to moisture stress than primed cotton seed. For maize, there was significant (P < 0.01) water potential × seed size and water potential × seed treatment interaction. Smaller seeds were less sensitive to low water potential than large and medium seeds with respect to germination, but they may have less food reserves to emerge from deteriorating seedbeds. Final germination percent of cotton and maize seed decreased as the...
26 citations
TL;DR: In this article, the effect of plant population density and irrigation on the water use efficiency of maize crops was quantified, with particular emphasis on the partitioning of water use into transpiration and direct evaporation of water from soil beneath the crop canopy.
Abstract: This study aimed to quantify the effect of plant population density and irrigation on the water use efficiency (q) of maize crops, with particular emphasis on the partitioning of water use into transpiration (T) and direct evaporation of water from soil beneath the crop canopy (Esc). A field experiment was undertaken using a split-plot design with watering regimes (rainfed and irrigation) as main plots and plant population density (66,667 and 133,333 plants ha−1) as subplots. Evapotranspiration (ET) was determined by monitoring soil moisture content at 7 d intervals using a neutron probe, Esc was measured daily using microlysimeters, and T was calculated as the difference between ET and Esc. An increase in planting density increased q by 24% under irrigation but reduced q by 17% under rainfed conditions. Esc was 4% less, and T was 9% greater at the highest plant population density owing to a larger crop leaf canopy. Irrigation increased both Esc and T by 41%. Neither Esc nor T were affected by the interac...
23 citations
TL;DR: In this article, the effect of different concentrations of hydrogen cyanamide (HC) and mineral oil (OIL) on budburst, yield, fruit quality and vegetative growth of mature 'Golden Delicious' apple trees were evaluated; the objective was to determine the presence of interaction between the rest-breaking effect of HC and oil when combined at varied concentrations.
Abstract: South African production areas receive insufficient winter chilling for apple production, necessitating the use of artificial means to break dormancy. Hydrogen cyanamide (HC) alone or in combination with mineral oil (oil) is used as a rest-breaking agent in many deciduous species. The effect of different concentrations of HC and oil on budburst, yield, fruit quality and vegetative growth of mature ‘Golden Delicious’ apple trees were evaluated; the objective was to determine the presence of interaction between the rest-breaking effect of HC and oil when combined at varied concentrations, and to determine appropriate concentrations of HC and oil, to enhance bud- burst, yield and fruit quality. Three trials were conducted in the Elgin valley (34 °S, 300 m) of the Western Cape, South Africa, in 1999 and 2000. The first trial evaluated four concentrations (0, 0.5, 1 and 2%) of Dormex® (hydrogen cyanamide 520 g-L−1) in combination with four concentrations of mineral oil (0, 1, 2, and 4%). The second trial used ...
22 citations
TL;DR: In this article, the effects of N fertilizer and aerobically composted cattle manure, applied separately or in combination, on maize (Zea mays L.) grain yields and net benefits were determined over three seasons.
Abstract: The effects of N fertilizer and aerobically composted cattle manure, applied separately or in combination, on maize (Zea mays L.) grain yields and net benefits were determined over three seasons. A field experiment was established on a moderately leached sandy loam soil (Typic Kandiustalf). Manure was a poor source of N. In the first year, increase in grain yield was much higher when manure (12.51 ha−1 and 37.51 ha−1) was combined with the 60 kg N ha−1 mineral N rate (40% and 25.1%, respectively), and a relatively smaller further increase of 17.5% was recorded for the 37.5 t ha−1 rate while there was a decrease of 3.7% for the 12.5 t ha−1 rate, when mineral N rate was doubled to 120 kg N ha−1. In the third season increase in grain yield was also much higher when manure (12.51 ha−1 and 37.51 ha−1) was combined with the 60 kg N ha−1 mineral N rate (66.2% and 16%, respectively) and relatively smaller further increases were recorded when the mineral N rate was doubled to 120 kg N ha−1 (21.4% and 15.1 %, respe...
22 citations
TL;DR: The study indicated the existence of ample trait diversity in highland maize accessions, which can be exploited by hybridization and selection.
Abstract: Farmers in the highlands of Ethiopia have developed locally adapted maize varieties for more than 300 years. In order to assess the phenotypic diversity among traditional Ethiopian highland maize accessions, a total of 180 accessions were evaluated for agro-morphological traits in a replicated randomized complete block design. The accessions varied significantly for all of the measured traits. Cluster analysis revealed the presence of four major clusters. Accessions collected from the different regions were distributed over all the phenotypic clusters, reflecting wide variation within a particular region, but low differentiation among regions. The first principal component, which explained 40.4% of the total variation, was due to days to tasseling and silking, plant and ear height, leaf length and days to maturity. Traits directly selected by farmers (yield, kernels per row, rows per ear, and ear height) had the highest phenotypic coefficient of variation (PCV), whereas indirectly selected traits (ear dia...
22 citations
TL;DR: The supplementation of nitrogen through the spraying of KNO3 and urea is believed to be the reason for the observed greater flowering and yield results of the sprayed relative to the unsprayed trees.
Abstract: The effects of leaf applications of potassium nitrate (KNO3), alone and in combination with urea at different concentrations on flowering, fruit set and fruit quality of Tommy Atkins' mango grown in the rift valley of Ethiopia were evaluated. The trees were characterised by erratic flowering, continuous and high intensity of vegetative growth as well as irregular bearing. Uniform trees were selected for a randomised complete block design experiment with three replications and three trees per plot. Spraying was conducted initially on the immature postharvest flushes and then repeated after the flushes had matured and had dark green leaves. Potassium nitrate concentrations especially in combination with urea (5 litre solution of 4% KNO3+0.5 g urea tree−1 and 5 litres of 4% KNO3+I g urea tree−1) produced better results for most of the flowering and yield parameters. There was a non-significant difference for the qualitative parameters between the treated and non-treated trees. The supplementation of nitrogen...
20 citations
TL;DR: The Kariega × Avocet S doubled haploid population and linkage maps have emerged as valuable resources for further genetic studies of qualitative and quantitative traits of economic importance in bread wheat.
Abstract: A doubled haploid wheat population of 150 lines was constructed from the F1 of a cross between cultivars Kariega and Avocet S using the wheat-maize technique. Segregation and linkage analysis of 203 DNA markers, two storage protein markers and the stem rust resistance gene Sr26 yielded 31 linkage groups of which 28 were chromosome-anchored. These linkage groups covered the entire genome of 21 chromosomes. SSR markers were advantageous for chromosome anchoring and AFLP markers for consolidation of the various linkage groups. A significant feature of the linkage map is a relatively low level of polymorphism for markers on the D genome, viz, 18.5% of all markers mapped. The Kariega × Avocet S doubled haploid population and linkage maps have emerged as valuable resources for further genetic studies of qualitative and quantitative traits of economic importance in bread wheat.
19 citations
TL;DR: The conventional planting density, being used in NE Ethiopia is not the optimum density, as increases in grain yield were linear up to a population density of 166 666 plants ha−1, and further study to determine the optimum planting density is recommended.
Abstract: An experiment was conducted at two locations in northeastern (NE) Ethiopia to determine the effect of population density on the growth, yield and nitrogen use efficiency of sorghum (Sorghum bicolor L. Moench) under two levels of nitrogen fertilizer application. Eight treatments, which consisted of factorial combinations of two N fertilizer levels (0 and 80 kg ha−1) and four population densities (166 666, 88 888, 38 095 and 29 629 plants ha−1), were evaluated in a randomised complete block design with three replications. The results indicated that nitrogen fertilizer significantly enhanced leaf area index, dry mass production, crop growth rate, and grain yields. Nitrogen fertilizer also positively affected yield components. Leaf area index, crop growth rate (at the early growth stages) and leaf, stem and panicle dry mass production increased as population density increased. Grain and stover yields at harvest increased in linear responses to increases in population density. Head and seed number per unit are...
TL;DR: In this paper, four balanced nutrient solutions, with different boron (B) levels (0.02, 0.16; 0.32 and 0.64 mg l−1), were applied.
Abstract: Problems with reduced yields owing to poor pollination where tomatoes are grown out-of-season in low cost greenhouses, motivated this study. Greenhouse tomatoes were planted in acid washed river sand. Four balanced nutrient solutions, with different boron (B) levels (0.02; 0.16; 0.32 and 0.64 mg l−1), were applied. The second flower cluster was covered with a transparent plastic bag and three relative humidity (RH) levels were applied to the isolated clusters. Dry (<10% RH) normal (60–75% RH) and moist (85–97% RH) air was constantly blown into the bags at ± 50 ml min−1. As a third factor at two levels, some of the clusters were vibrated daily with an electric vibrator (Poli-bee) and the controls not. The number of flowers per cluster, fruits per cluster, fruit set, weight of the cluster (yield), average fruit weight, seed production, fruit weight per number of seeds formed and fruits with blossom-end-rot (BER) were evaluated. Higher B-levels improved fruit set where trusses were not vibrated. A high RH re...
TL;DR: Three of the six accessions, namely Ambajeettee, AL-70 and ETS 2752 were chosen for their desirable properties in injera making and were characterised by high protein content, low tannins, intermediate endosperm texture, and white seed colours.
Abstract: Samples of 13 genetically diverse sorghum [Sorghum bicolor (L.) Moench] accessions were analysed for physical properties and chemical composition. The food (injera) quality and the phenolic (condensed tannins) content of six sorghum samples were also determined. The accessions showed a wide variation in protein (7.99 to 17.8%), lipids (2.52 to 4.76%), starch (51.88 to 85%), and amylose (12.30 to 28.38%) content. Grain weight varied in a wide range, and endosperm texture varied from intermediate to completely starchy. Linoleic acid (18:2) and oleic acid (18:1) were the major fatty acid constituents of sorghum lipids. Only a few significant correlations were observed among the physical and chemical properties. Three of the six accessions used for sensory analysis, namely Ambajeettee, AL-70 and ETS 2752 were chosen for their desirable properties in injera making. The chemical and physical properties of the selected accessions were characterised by high protein content, low tannins, intermediate endosperm tex...
TL;DR: It was shown that the level of resistance was not the same in all resistant cultivars and varied dramatically between cultivar and years when measured under severe D. noxia infestation.
Abstract: Russian wheat aphid, Diuraphis noxia (Kurdjumov), has been a serious pest of wheat in South Africa since 1978. Wheat producers observed that resistant cultivars, developed for control of this aphid, differed in resistance and questioned whether insecticide treatment would be economically justifiable. This study was undertaken to confirm and quantify the observed differences in sixteen resistant cultivars under field conditions. A split-plot field trial with four replicates was planted near Bethlehem, South Africa. The yield of each aphid- infested plot was expressed as a percentage of the yield of the corresponding aphid-free plot giving percentage yield retained after infestation for each cultivar. The percentage yield retained varied in 2000 from 33.0% to 119%; in 2001 from 28.3% to 150.0% and in 2003 from 28.4% to 109.2 %. Cultivars were ranked and classified into more resistant and less resistant groups for each year and an AMMI analysis was conducted. Some cultivars compensated for D. noxia infestati...
TL;DR: Tithonia diversifolia was tested as a low cost green manure in Malawi and it should prove to be a good green manure that can be afforded by small-scale farmers in these regions of Malawi.
Abstract: Locally available non-traditional green manure plants could potentially contribute to reversing the trend of declining soil fertility and raise maize yield in small-scale farms. In this study, Tithonia diversifolia was tested as a low cost green manure in Malawi. In a greenhouse incubation experiment, changes in soil nitrate (NO(3-), ammonium (NH4 +) and extractable phosphorus (Mehlich-3 P) were compared between treatments of T. diversifolia, Crotolaria juncea (sunhemp), Tephrosia vogelii, Mucuna utilis (velvet beans) and maize stover that were applied to the soil at an equivalent rate of 3 Mg dry matter ha−1. This was followed by a field study where three rates of T. diversifolia dry matter (1.5, 3.0, 4.5 Mg ha−1) were applied with or without triple superphosphate (TSP) supplement to maize grown at three locations in central and northern Malawi. The changes in laboratory incubated soil N03- and NH4 + levels were similar (P 0.05) among T. diversifolia, Tephrosia and Mucuna while the change in soil treated...
TL;DR: In this article, an Estcourt profile with degrading peds was sampled and analysed and the results showed that both ferrolysis and redistribution of Fe-Mn are active during short periods of reduction in the E and interpedal pores of the B horizon.
Abstract: Geographic associations of duplex soils, like the Estcourt form, and plinthic soils, like the Avalon and Westleigh forms, such as are found in the Eastern Free State, are recognised worldwide These soils share redox morphology In duplex soils, the redox morphology is dominated by a contrast in clay content between the A or E horizon and the B horizon, indicating that degradation of silicate clay minerals dominates In plinthic soils, mottling due to redistributed Fe-Mn dominates Both features can be the result of ferrolysis In order to research this relationship, an Estcourt profile with degrading peds was sampled and analysed Undisturbed peds of the B- horizon were subdivided for analysis, together with disturbed samples of the A, E and C horizons The spatial variation of the colours, Fe, Mn, clay content and mineralogy in the profile indicates that both ferrolysis and redistribution of Fe-Mn are active during short periods of reduction in the E and interpedal pores of the B horizon Degradation of
TL;DR: As expected, phytotoxic effects increased with increasing application rates, but significant differences in germination percentage and seedling growth between similar rates of the two chemical treatments indicated that the SA combination treatment was more phytOToxic than Cruiser.
Abstract: Incubation studies were conducted to determine effects of two chemical seed treatments (Cruiser & SA-combination) on the germination and seedling vigour of canola (cv. Varola 44) seed. Germination percentages of the Cruiser and SA-combination treated seeds were not significantly reduced compared to untreated seeds (control) under favourable temperature and water conditions. After exposure to high temperature (41 °C) and humidity to accelerate ageing of the seed, germination and seedling vigour were reduced by both seed treatments. In contrast to differences in germination which decreased with time of incubation, the effect of both chemical treatments on seedling vigour increased as the incubation period increased. As expected, phytotoxic effects increased with increasing application rates, but significant differences in germination percentage and seedling growth between similar rates of the two chemical treatments indicated that the SA combination treatment was more phytotoxic than Cruiser.
TL;DR: In this article, three field trials done in this area showed no yield advantage of rotated maize and wheat in comparison with monoculture cropping, and the effect of crop rotation on yield was investigated.
Abstract: Crop rotation is the successive growing of different crop species on fields with the aim to assist sustainability. Monoculture cropping, the opposite of crop rotation, of maize was and still is the main practice in the summer rainfall area of South Africa. Declining farm profits in the 1980's and increased risk due to the liberalisation of the grain markets in the early 1990's led to renewed interest in crop rotation as a practice for economically sustainable grain production although limited research has been done locally. Results of three field trials done in this area showed no yield advantage of rotated maize and wheat in comparison with monoculture. In seven trials, maize and wheat crop yields were affected, mainly improved by crop rotation. An important benefit of crop rotation in comparison with monoculture cropping is the relative low production risk with or without an increase in nett-return. Possible causes for the effect on yield involve the change in the availability of soil water and nitrogen...
TL;DR: Results indicated that the Stirring Number and Falling Number methods are the most reliable for the determination of preharvest sprouting and α-amylase activity.
Abstract: Sprouting in wheat is common when rain occurs during harvest. This causes the moisture content of the grain to increase to a level at which germination takes place and α-amylase increases. Various methods can be used to determine α-amylase in cereals. The Falling Number method is currently widely used in the milling and baking industry. As well as being time-tested and reliable, this method is very sensitive to the presence of low levels of enzyme. However, it is often influenced by factors other than α-amylase, such as the nature of the starch, starch damage and environment. In this study various methods to determine preharvest sprouting and α-amylase activity were compared. All the methods evaluated showed significant correlations to each other and any of these methods could therefore be used to determine sprouting. Results indicated that the Stirring Number and Falling Number methods are the most reliable for the determination of preharvest sprouting and α-amylase activity.
TL;DR: It is suggested that NIRS can be developed as a rapid and accurate tool for the prediction of the nutritional value of feedstuffs, which makes it an attractive technique for routine quality control in the industry.
Abstract: Near infrared reflectance spectroscopy (NIRS) was evaluated as a tool for the fast and inexpensive prediction of nutritional values of feedstuffs. NIRS calibrations were developed for winter grain samples collected over three years in the Western Cape region of South Africa. Winter grains used in the study include oats, barley, triticale and wheat. Calibrations were also developed for maize samples collected throughout South Africa. Win- ter grain samples were analysed for ash, dry matter (DM), crude protein content (CP), fat content, acid detergent fibre (ADF), neutral detergent fibre (NDF), in vitro organic matter digestibility (IVOMD), lysine and methionine. The digestible energy (DE) content of winter grain samples was determined by the mobile nylon bag technique on pigs. Maize samples were analysed for ash, DM, CP, IVOMD and TDN (total digestible nutrients). Standard errors of prediction (SEP) and multiple correlation coefficients (r) for the different winter grain constituents were respectively; ash...
TL;DR: The feasibility of obtaining uniform spore deposition on Lens culinaris, a plant with compound leaves, was investigated using a settling tower and the coefficient of variation was inversely related to the spore quantity dispersed.
Abstract: An inoculation technique resulting in uniform spore deposition for obtaining reproducible and accurate data on host responses is required for quantitative studies of resistance expression. The feasibility of obtaining uniform spore deposition on Lens culinaris, a plant with compound leaves, was investigated using a settling tower. Uniformity of spore deposition on adhesive coated glass slides was assessed by dispersing 1,2,4 and 8 mg spores of Uromyces viciae-fabae, the causal agent of lentil rust, into the tower. When an 8 mg spore quantity was discharged the number of spores deposited per square centimetre did not vary significantly (P > 0.05) between the different locations of the glass slides on the target area. A linear, relation was found between mass of spores discharged into the tower and spores deposited. Counts for 1, 2, 4 and 8 mg were, respectively, 82, 244, 384 and 972 spores per square centimetre. Uniformity of spore deposition increased as the amount discharged increased, and the coefficien...
TL;DR: In this paper, a soil-less water-use-efficient "Ebb-and-Flood" production system, developed for areas with limited water resources, was compared with two conventional soil irrigation systems, using Amaranthus hypochondriatus L., locally known as Imbuya.
Abstract: Family scale vegetable production should be enhanced in rural areas in order to prevent vitamin A deficiencies. A soil-less water-use-efficient ‘Ebb-and-Flood’ production system, developed for areas with limited water resources, was compared with two conventional soil irrigation systems, using Amaranthus hypochondriatus L., locally known as Imbuya. The soil-grown plants were flood- and drip irrigated once every week, using nutrient solutions at two electrical conductivity (EC) levels of 1.80 mS cm−1 and 3.60 mS cm−1. The same volumes of nutrient solution were applied to these soil-irrigated plots as was used in the preceding week by the soil-less ‘Ebb-and-Flood’ system. With the soil-less ‘Ebb-and-Flood’ system, plants were fertigated five times per day and the containers were randomly allocated between the soil-grown field plots. Leaf yield as well as water use efficiency was highest when the high EC nutrient solution was drip irrigated. As part of the drip treatment, the dripper lines were covered with ...
TL;DR: Results from field testing of rust infected and rust-free lines showed that resistance was considerably improved without yield loss, and progress made with germplasm improvement by means of backcrossing is reviewed.
Abstract: Infection of dry beans (Phaseolus vulgaris L.) by rust, caused by Uromyces appendiculatus Pers.: Pers. (Unger), results in regular yield and quality losses in South Africa. The growing of resistant varieties is generally considered the most cost effective control measure. To meet this objective, rust resistance has been an important selection criterion since the dry bean breeding programme of the Agriculture Research Council (ARC) was initiated at Potchefstroom in the 1970's. The breakdown of resistance in earlier varieties indicated that pathogenic variation occurred in U. appendiculatus in South Africa and that a more coordinated resistance breeding programme, including race surveys, was needed. This article describes the approach that was followed at the ARC and reviews progress made with germplasm improvement by means of backcrossing. Rust resistance has been transferred from 16 donor lines, including the genes Ur-3+, Ur-5, Ur-11 and uncharacterized genes, to adapted germplasm. Results from field test...
TL;DR: In this paper, the authors developed a yield prediction model for maize grown on two semi-arid ecotopes, i.e. the Glen/Hutton-Ventersdorp and Glen/Oakleaf-Dipene ecotope, located in the Free State Province.
Abstract: A yield prediction model is necessary, together with long-term climate data, to calculate the long-term yields needed for making a quantitative productivity evaluation of a crop ecotope in the form of a cumulative probability function (CPF). In this study the development of such a model for maize grown on two semi-arid ecotopes, i.e. the Glen/Hutton-Ventersdorp and Glen/Oakleaf-Dipene ecotopes, located in the Free State Province, is described. A fairly reliable empirical relationship was obtained between the total above ground biomass and a water stress index using the results of 22 field experiments on these ecotopes. The model consists of the regression equation which describes this relationship viz. Yb = 15238 ISI + 1067 (R = 0.69) where Yb is the predicted total above ground biomass in kg ha−1 and ISI is an integrated stress index for a particular growing season. The stress index is based on the ET/Eo relationship during the growing season.
TL;DR: In this paper, chemical composition and digestibility values were obtained to provide a database for accurate values of hay and straw types produced in the Western Cape area of South Africa by collecting 10 different localities in the Swartland and Ruens areas.
Abstract: Chemical composition and digestibility values were obtained to provide a database for accurate values of hay and straw types produced in the Western Cape area of South Africa. Straw and hay samples were collected from 10 different localities in the Swartland and Ruens areas of South Africa. Barley hay had the highest IVOMD value (753.2 g kg), followed by wheat (744.9 g kg), triticale (720.4 g kg) and oats (697.7 g kg). Wheat hay had the highest TDN value (670.7 g kg), with oats having the lowest value (627.5 g kg). Oats was higher in NDF (602.8 g kg) compared to the other hay types. ADF values of barley (297.9 g kg), oats (342.4 g kg) and triticale (323.0 g kg) differed significantly. Oat straw had a much higher IVOMD value (392.0 g kg) compared to the other straw types. Barley had the lowest IVOMD value (293.2 g kg). The TDN value of oats (444.8 g kg) was higher than for the other straw types. Barley straw had the highest NDF value (817.7 g kg), which differed from oats (781 2 g kg) and triticale (795.4 g kg). There were significant differences in the ash, CP, IVOMD, TDN and ADF contents of straw produced in the Swartland and Ruens areas. Ash, CP, IVOMD and ADF values of cereal straw samples were higher when produced in the Ruens. NDF values were higher in cereal straw samples from the Ruens, except for barley (from the Swartland), which had a higher NDF value. The TDN value of cereal straw was higher for the samples collected in the Ruens compared to those from the Swartland, although wheat and triticale showed higher TDN values when sampled in the Swartland. These differences should be taken into account when hay and straw from the different areas are used in formulating a balanced diet. This accentuates the importance of routine analysis of hay and cereal straw before use in diet formulations.
TL;DR: In this article, the effect of calcium, applied as a seed coat or priming osmoticum, on green beans (Phaseolus vulgaris L.) under field conditions was examined.
Abstract: Cotyledonal cracking is a physiological disorder, which appears as one or a few transverse fissures across legume seed cotyledons early during seed germination or seedling emergence. The fissures hinder translocation of nutrients to the developing seedling and cause stunted seedling growth and low yield. The objective of this study was to examine the effect of calcium, applied as a seed coat or priming osmoticum, on cotyledonal cracking in green beans (Phaseolus vulgaris L.) under field conditions. Seeds of six green bean cultivars (‘Imbali’, ‘Elangeni’, ‘Tongati’, ‘Sodwana’, ‘Tokai’ and Outeniqua') were primed or coated with CaSO4, CaCI2 and Ca(NO3)2 solutions (1,10, 50,100 and 1000 mM). Control seeds were not primed or coated. Dried (~ 10% moisture content on fresh mass basis) seeds were planted in the field at three sites in KwaZulu-Natal, South Africa. A significant reduction in cotyledonal cracking occurred in response to increased calcium molarity, however, no effect of the anions of the calcium sal...
TL;DR: Endosulfan has a low toxicity to bees and will therefore control N. natalensis without a detrimental effect on pollination, and remains more effective over longer periods than contact insecticides.
Abstract: No insecticide is currently registered for Nysius natalensis Evans (Hemiptera: Orsillidae), control on sunflower [Helianthus annuus L. (Asteraceae)]. Field as well as laboratory trials were conducted to evaluate efficacy of insecticides for N. natalensis control. During budding prior to anthesis, insecticides were applied aerially. These were endosulfan, a mixture of dichlorvos + monocrotophos, mevinphos, a mixture of endosulfan + cypermethrin, methomyl and cypermethrin Compared to the untreated control, all insecticides provided effective control of N. natalensis. However, re-infestation by the pest occurred in all treatments after five days. A laboratory evaluation of the efficacy of the contact action of eleven insecticides in controlling N. natalensis adults on sunflower heads during application or immediately thereafter was conducted. Insecticides were representative of different groups and modes of action. These were carbosulfan, methomyl, endosulfan, demeton-S-methyl, dichlorvos, chlorpyrifos, mala...
TL;DR: The different seed germination responses of the test species to an aqueous leaf extract of African wormwood raises the possibility of developing a bioherbicide from the extract.
Abstract: Herbicide resistance in weeds is a phenomenon threatening sustainable cereal production in the winter rainfall region of South Africa. Every possible weed control measure that may be used to complement chemical weed control measures should be investigated. The effect of aqueous leaf extracts of the aromatic shrub African wormwood (Artemisia afra) on germination of selected crop and weed species were investigated. The selected plant species included wheat (Triticum aestivum L.), herbicide resistant and non-resistant ryegrass (Lolium spp.), canola (Brassica napus) and lucerne (Medicago sativa). Various dilutions were investigated and the original extract was the most effective in inhibiting seed germination as compared to the inconclusive results from further dilutions. The original extract that completely inhibited seed germination in canola, had no significant negative effect on seed germination of wheat and lucerne. The reduction in seed germination of both the resistant and non-resistant ryegrass was hi...
TL;DR: In this paper, the potential of pine litter for use as a substrate in the propagation of vegetable transplants in trays was evaluated, and the sub-optimum pH and electrical conductivity of the pine litter were evaluated.
Abstract: The study evaluates the potential of pine litter for use as a substrate in the propagation of vegetable transplants in trays. Sub-optimum pH and electrical conductivity of pine litter were addresse...
TL;DR: In this paper, the effects of foliar sprays of 1, 3, and 5% mono-potassium phosphate (MKP), 2% urea ammonium phosphate (UAP), and 1% monoammonium phosphate(MAP) applied 4 or 6 weeks after full bloom (WAFB) on rind texture and juice acid content of selected Citrus spp. on rough lemon rootstock were evaluated from the 1998/99 to 2000/01 seasons.
Abstract: Rind coarseness of fruit of Citrus spp. is a general problem in the Citrusdal region of South Africa (Western Cape Province), often limiting the percentage of exportable fruit. Acid content of the juice of Citrus fruit is an important determinant of juice quality, and fruit with too high juice content are not preferred by consumers. The effects of foliar sprays of 1%, 3% and 5% mono-potassium phosphate (MKP), 2% urea ammonium phosphate (UAP) and 1% mono-ammonium phosphate (MAP) applied 4 or 6 weeks after full bloom (WAFB) on rind texture and juice acid content of selected Citrus spp. on rough lemon rootstock were evaluated from the 1998/99 to 2000/01 seasons. Foliar sprays of MKP and MAP reduced TA of ‘Thoro Temple’ tangor when applied 6 WAFB, and MKP, UAP and MAP improved rind texture of the tangors (‘Nouvelle’ and ‘Thoro Temple’) and oranges (‘Shamouti’ and ‘Valencia Late’) without affecting juice and SS contents.