Masters Degrees (Soil, Crop and Climate Sciences)
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Browsing Masters Degrees (Soil, Crop and Climate Sciences) by Author "Ceronio, G. M."
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Item Open Access Chemical factors influencing dry bean yield(University of the Free State, 2000) Molahlehi, Lebone; Pretorius, J. C.; Ceronio, G. M.English: The abscission of the reproductive organs (flower buds, flowers and pods) of the common bean, Phaseolus vulgaris L., has proved to be a very serious problem affecting bean yields. The yield reductions are mainly significant under conditions of environmental stress, which aggravate production of the abscission causing hormones such as ethylene. The study therefore evaluated the effect of certain nutrients, other chemicals and ethylene (growth regulator) applied as foliar sprays to determine their effect in as far as abscission of the reproductive organs in beans is concerned. Glasshouse trials were carried out during the 1998/99 and 1999/00 seasons to investigate the possible preventative role of some micro and macro-nutrients, abscission inhibitors (e.g. Silver) and growth regulators (e.g. ethylene) all applied as foliar sprays. In another trial, three cultivars were compared where no treatments were applied. Data were collected and the following parameters were measured; number of flowers and pods that abscised, pods formed and abscised, pods that matured and could be harvested, dry pod mass at harvest, seed number per pod, dry seed mass per pod and total yield per hectare. Data were analyzed using a SAS software system and interpreted accordingly. The results of this study indicated that flower and pod formation might not be considered as the major factor affecting bean yields. The reason being that flowering percentage was not very different between the treated and the untreated plants. The abscission of flower buds, flowers and pods, however, was relatively high in general, indicating that this is possibly a primary factor affecting poor yields in beans. Ethrel, an ethylene releasing compound, applied as a foliar spray, aggravated the problem of flower and pod abscission. An ethylene antagonist (silver salt) had a slight alleviating effect on organ abscission but did not improve the final yield significantly. Molybdenum and potassium salts improved flower formation to a certain extent but had no real alleviating effect on organ abscission. This was also revealed in the lack of yield improvement. Foliar application of a copper salt as well as treatment with ComCat®, a natural product with biocatalytic properties, did not influence flower and pod abscission significantly, but increased the final yields to some extend. The latter indicates that other factors besides organ abscission could have had an effect on determining the final yield outcome. In the light of these findings, it is suggested that further studies be undertaken to test a wider range of chemicals for their potential to circumvent flower and pod abscission and improve bean yields. The latter could also include treatment at other growth stages, including post flowering. Other attempts could include an investigation into the effect of other known ethylene antagonists such as AVG (L-a.-(2-arninoethoxyvinyl)-glycinehydrochloride), an inhibitor of ethylene synthesis and NBD (2,S-norbornadiene), an inhibitor of ethylene action, on organ abscission and yield outcome in beans. As the results also showed that other factors besides organ abscission could have played a role in yield improvement, it might be worthwhile to investigate the effect of promising chemicals on physiological processes.Item Open Access The effect of nitrogen fertilisation on the growth, yield and quality of swiss chard (Beta vulgaris var. cicla)(University of the Free State, 2008-05) Motseki, Pontso Christina; Engelbrecht, G. M.; Ceronio, G. M.English: The sustainability of subsistence farming associated with the health of rural communities’ necessitated research on Swiss chard as it forms an integral part of food consumed by the poor in developing countries. Two separate pot experiments were carried out during the 2005/06 and 2006/07 seasons in the glasshouse of the Department of Soil, Crop and Climate Sciences at the University of the Free State. The objective of this study was to determine the effect of nitrogen fertiliser on growth, yield and quality of Swiss chard. The first pot trial was conducted to evaluate the effect of five nitrogen levels (0, 50, 100, 200, 400 kg N ha-1) and four application times on the growth, yield and quality of two Swiss chard cultivars (‘Fordhook Giant’ and ‘Rhubarb’). Two Swiss chard seedlings were planted per pot, filled with topsoil of the fine sandy loam Bainsvlei form. Two weeks after planting plants were thinned to one seedling per pot. Different nitrogen levels were applied to the relevant pots as follows: once every second, fourth, sixth or eighth week. It was only the total dry mass per plant and total nitrogen content per leaf of ‘Rhubarb’ plants that was significant higher than that of ‘Fordhook Giant’. The other parameters measured for the two cultivars did not differ significantly from each other. Nitrogen levels positively influenced the early growth, yield and quality parameters measured. It was the highest nitrogen level (400 kg N ha-1) that resulted in the highest number of leaves harvested, leaf fresh and dry mass, leaf area and leaf nitrogen content. Nitrogen application times significantly influenced only the early growth of Swiss chard plants and the nitrogen content of leaves. Early plant growth reacted better where nitrogen was split into three equal applications (T4). The total nitrogen content of Swiss chard leaves was significantly higher where nitrogen was split into five equal (T2) or three equal (T4) applications. In the second pot trial the effect of different nitrogen sources applied at different levels on the growth, yield and quality of Swiss chard cultivars was determined. The response of Swiss chard plants to nine nitrogen levels (0, 100, 200, 300, 400, 500, 600, 700, 800 kg N ha-1) from six different nitrogen sources (ammonium nitrate, potassium nitrate, calcium nitrate, ammonium sulphate, urea ammonium nitrate and urea) were studied. Based on the findings of this study, nitrogen significantly influenced growth, number of leaves harvested, leaf fresh and dry mass, leaf area and leaf nitrate content of ‘Fordhook Giant’ plants with best results obtained at 800 kg N ha-1. Nitrogen sources did not influence either the total number of leaves harvested nor the fresh mass of harvested Swiss chard leaves. In both cases, ammonium nitrate gave the best results and calcium nitrate the poorest. Urea influenced the leaf area positively followed by urea ammonium nitrate, with calcium nitrate resulting in the smallest leaf area per plant. Dry mass of Swiss chard leaves was also significantly higher where urea was used as nitrogen source compared to where calcium nitrate was used. No significant differences amongst the other nitrogen sources. Ammonium nitrate and potassium nitrate significantly stimulated the accumulation of nitrate in Swiss chard leaves, whereas the other nitrogen sources did not play any role in nitrate accumulation in the leaves of Swiss chard.Item Open Access Effect of potassium humate on soil properties and growth of wheat(University of the Free State, 2008) Van Tonder, Johan Tobias; Ceronio, G. M.; Du Preez, C. C.English: Soil properties (biological and chemical) and crop response are dependent on the inherent soil organic matter content. Since South African soils are naturally low in organic matter content commercial humates serve as attractive soil amendments in improving soil quality. This is the result of commercialisation giving the impression that humates have biological and chemical properties similar to those in soil humus. In an attempt to substantiate these claims three separate experiments were conducted at the University of the Free State to examine the effect of K-humate on soil properties and wheat response during the 2006 growing season. The biological (bacterial and fungal count) response was evaluated in growth chambers by applying three different K-humate products at rates of 0, 3 and 5 L ha-1 in a band on a red loamy sand topsoil. Soil cores were sampled on a weekly basis for six weeks and microscopically analysed. Bacterial and fungal count differed significantly as a result of the product by application rate interaction but no consistency was found. Over time both the bacterial and fungal activity increased rapidly for week 2 and 3 but decreased at week 3 for the bacteria. Both the organisms’ reactions stabilised from week 3 to 6. The chemical soil properties were also tested in growth chambers but only K-humate (single product) was applied as a coating on granular 2:3:2 (22) fertiliser at 0 and 3 L ha-1 in a band 50 mm below the soil surface. The chemical soil properties showed no response after 5 months to the application of K-humate. A glasshouse experiment was also conducted to evaluate the growth and yield response of wheat on three textural class topsoil’s (8, 22 and 37% clay) and four K-humate applications (0 L ha-1, 3 L ha-1 single application, and 3 and 6 L ha-1 split application – 50% at planting and 50% at tillering). K-humate as a coating on 2:3:2 (22) granular fertiliser was banded and Greensulph (27) topdressed at the required fertiliser rate for a yield potential of 8 t ha-1. Plant growth parameters were analysed at tillering, stem elongation and maturity, both above- and below-ground. Virtually no significant influences were found with the K-humate application rate and soil texture interaction on the measured parameters. Notwithstanding this, positive effects were noticed and a split application whereof half of the K-humate was applied at planting and the other half at tillering showed the best results. A field experiment was also conducted to examine K-humates influence on wheat growth and yield. Two experiments was conducted, one under full irrigation (700 mm) with a yield potential of 8 t ha-1 and the other supplementary irrigation (350 mm) with a yield potential of 4 t ha-1. K-humate was applied as a coating on granular 2:3:2 (22) fertiliser and bandplaced either as a single application (0, 1.5, 3, 5 and 6 L ha-1) or a split application (5 and 6 L ha-1) 50% at planting and 50% (K-humate as a coating on Greensulph (27)) at tillering. Irrigation was applied using a line source irrigation system. The field experiment confirmed the results obtained in the glasshouse with virtually no significant effects as a result of the applied K-humate on the measured plant parameters.Item Open Access Effect of spray volume, water quality, adjuvants and ammonium salts on sethoxydim activity(University of the Free State, 1998) Chiconela, Tomás Fernando; Ceronio, G. M.; De Villiers, B. L.The effects of spray carrier, pH, adjuvants and ammonium salts, environmental factors, and spray volume on sethoxydim {2-[ 1-ethoxyirnino-butyl]-5-[2-( etylthio )propyl]-3- hydroxy-2-cyclohexen-1-one} activity in a glasshouse on tomato (Lycopersicum esculentum L cv. Star 9001) and oats (Avena sativa L cv. SSH 241) were studied. Sodium bicarbonate, potassium carbonate and spray solution pH were antagonistic to sethoxydim phytotoxicity. Spray solution pH and ions present were antagonistic to sethoxydim phytotoxicity only when the spray carrier pH exceeded 6.5. Sadol and ammonium salts (ammonium nitrate and ammoruum sulfate) were equally effective in enhancing sethoxydim activity regardless of the presence of antagonistic salts. Bladbuff 5 was moderately effective in the enhancement of sethoxydim phytotoxicity only when sethoxydim was applied at 186.0 g ai.ha¹ and not at 139.5. Addition of Agral 90 and Break- Thru were not beneficial, or were both of little value as adjuvants with sethoxydim. Sethoxydim applications at temperatures ranging between 25 and 35°C were equally more effective as compared to 15°C. However, Sadol, Break- Thru and ammonium salts were most effective in enhancing sethoxydim performance at 25°C than at 15 or 35°C. When averaged across sethoxydim rates and the presence of sodium bicarbonate and in potassium carbonate in the spray solution, oat fresh top mass reduction increased as carrier volume was decreased from 875 to 175 l.ha¹. In all the experiments conducted, tomato plants did not show any injury to negative growth suggesting that sethoxydim may be considered for control of grass weeds in tomatoes.Item Open Access The effect of water quality on the growth and yield of irrigated crops(University of the Free State, 2006-05) Dikgwatlhe, Shadrack Batsile; Ceronio, G. M.; Van Rensburg, L. D.English: Salinity is a major limitation and threat sustainable crop production in South Africa and elsewhere in the world. An intensive study by Du Preez et al. (2000) on the water quality of the lower Vaal River system using international salinity indicators were conducted and it was concluded that unacceptable damage to crops would be experienced if the salinity of the irrigation water continued to increase at the projected rates. Following that, intensive germination and glasshouse pot experiments were conducted based on the projected longterm salt accumulation on irrigated soils. Little or no quantitative information on the subject was available for South African conditions. This study was also part of a WRC project titled: The effect of irrigation water salinity on the growth and water use of selected crops. The objective of this study was to quantify the effect of different saline irrigation water levels (electrical conductivity, ECi ) on the germination, growth and yield of selected crops, viz. wheat (Triticum aestivum L. - SST 806.), maize (Zea mays L. - PNR 6335), peas (Pisum sativum L. - Solara) and beans (Phaseolus vulgaris L. - Teebus) at different growth stages. These crops were subjected to five different ECi levels (15 - control, 150, 300, 450, 600 for wheat and maize, and additionally 1200 mSm-1 for wheat, and 15 - control, 75, 150, 225, 300 mS m-1 for peas and beans). Three stages were used for each crop, viz. tillering, flag leaf and maturity (wheat), 2, 4 and 6 wae - weeks after emergence (maize) and 5 wae - five weeks after emergence, flowering and maturity (peas and beans). Various morphological indicators presented on a relative scale were measured to quantify the impact of ECi levels on both below and above ground growth. When subjecting the crops to the different ECi levels, the salt tolerance of these plants was taken into consideration. These crops were affected at varying degrees, depending on the salt sensitivity of the crop involved. Interesting results were obtained for all the crops and based on the findings the study agreed well with the international accepted salinity classification system where wheat is classified as moderately tolerant and peas and beans as sensitive. Maize proved to be sensitive in this study, but it has to be noted that it was only at a very early growth stage. The water use of the pot experiment plants was found to be very high and this was attributed to the smaller volume of soil relative to the canopy. All plant growth indicators proved to be negatively affected over the selected ECi range. The reduction in growth for all crops followed a similar trend with increasing ECi levels. The EC of the saturation soil extract (ECe) was also measured in order to determine the rate of soil salinisation and was found to be 2 to 3 times that of ECi. The study also compared the responses of these crops by using primary growth indicators (leaf area, root mass, biomass and seed yield) and also attempted to determine the salt tolerance values using the regression coefficients. Therefore, all the objectives set for the study were achieved. The effect of salinity on a variety of other crops under South African conditions should be thoroughly and comprehensively investigated in future.Item Open Access Emergence response of sunflower cultivars (Helianthus annuus L.) to planting techniques and soil factors(University of the Free State, 2014) Schlebusch, L.; Ceronio, G. M.; Nel, A. A.English: South Africa mainly produces oil seed sunflowers of which 86% is produced in the Free State and North West provinces which are known for their sandy soils. Temperatures can rise to 42°C in these soils when planting commences during November to January. These conditions, in combination with other factors such as planting date and planting depth, soil type, different cultivars, and seedling vigour, can influence the emergence rate of sunflower seedlings. This will cause uneven stand which could affect the yield negatively. In an attempt to evaluate the influence of soil factors and planting techniques on sunflower emergence, three experiments were conducted in the greenhouse at the Department of Soil, Crop and Climate Sciences of the University of the Free State. These experiments evaluated the effect of seed size, planting techniques, and soil factors, and high soil temperatures on the emergence rate of selected sunflower cultivars. Three seed sizes (seed size one to three) of three cultivars (PAN 7049, PAN 7057, and PAN 7063) were planted at two planting depths (25 and 50 mm respectively) during three planting dates (September 2010, November 2010, and February 2011) to determine the influence on the emergence rate of seedlings. It was found that a smaller seed size, such as seed size three, emerged faster than larger seeds, seed size one. The influence of two planting depths (25 and 50 mm) during the previously mentioned planting dates with two soil types (Bainsvlei and Tukulu) on the emergence of sunflower seedlings was also tested. Cultivar emergence was faster at 25 than at 50 mm. It was also observed that the emergence rate was faster during February 2011 than during September and November 2010. Although the emergence was faster during February 2011, above ground growth (plant height and dry weight) was greater during November 2010 than during September 2010 and February 2011. The influence of four soil temperatures (35, 40, 45, and 50°C respectively) on the emergence of sunflower cultivars was tested. An under floor heating wire (23 kW) was attached to a galvanised metal grid and was used to simulate day and night temperatures in the top soil. The grid and seed were placed at a depth of 25 mm (planting depth). Emergence index declined gradually from 35 to 45°C, but a rapid decline in emergence index was observed from 45 to 50°C. Emergence can be measured or calculated as an emergence index. Emergence is determined as the moment that the seedling is visible above the ground and different formulas exist to determine the emergence. Experiments differ from one another and therefore different emergence index models were developed to accommodate the experiment methods or crop that was used. It can therefore be concluded that differences in emergence exist between cultivars. It is also necessary for producers to acknowledge that soil factors and planting techniques play a vital role during planting until the seedling emerge.Item Open Access Factors affecting maize (Zea mays L.) sensitivity to acetochlor(University of the Free State, 2009-12) Mphundi, Patricia Makuzana; Allemann, J.; Ceronio, G. M.English: A number of the commercially available maize cultivars were screened in order to establish their tolerance to acetochlor. These cultivars demonstrated significant differences in their tolerance, with some cultivars being tolerant and others sensitive to the herbicide. The cultivar PAN6Q521R was the most tolerant and DKC 73-76R was the most sensitive, while most other cultivars were intermediate in their sensitivity. This indicates that maize tolerance to acetochlor is genetically controlled. The influence of planting depth on maize tolerance to acetochlor was investigated using these two cultivars. Both cultivars were found to be more sensitive as the planting depth increased to 45 mm. However, seedlings of DKC 73-76R exhibited more phytotoxicity than PANQ6521R at all planting depths. The effect of seed size on acetochlor tolerance could not be determined with any clarity. Cultivar sensitivity to the herbicide as well as seed shape appeared to also play a role. In DKC 73-76R it appeared as though large flat seeds produced plants more tolerant to acetochlor than smaller flat seeds. The effect of soil type on acetochlor phytotoxicity on a tolerant (PANQ6521R) and sensitive (DKC 73-76R) maize cultivar was examined in two trials, one using an average application rate on all soils, and the second utilizing the recommended application rates for each soil. Acetochlor activity was found to be lowest on the clay loam soil (38% Clay) and highest on the sandy soil (8% Clay) in the first case, with severe phytotoxicity occurring on the latter soil. In the second trial bioactivity was similar on all soils, although greater on the sand. This indicated that the recommended application rate on sandy soils might need adjustment. The influence of temperature on maize tolerance to acetochlor was investigated at suboptimal (15/8oC), optimal (25/18oC) and supra-optimal (35/28oC) temperature regimes (day/night temperature respectively). Seedling growth of both cultivars was inhibited significantly by acetochlor at the optimum temperature regime (25/18oC). All results confirmed that DKC 73-76R was more sensitive to acetochlor than PAN6Q521R.Item Open Access Influence of nitrogen and potassium applications on the early growth and development of maize (Zea mays L.)(University of the Free State, 2000) Emmanuel, Willie President; Ceronio, G. M.; Du Preez, C. C.English: It is well known that appropriate band applications of N and/or K can result in optimum early growth and development of maize. Two pot experiments were conducted in a glasshouse at the University of the Orange Free State, Bloemfontein to determine the application levels at which the above mentioned phenomena occur. The first experiment was conducted to determine the influence of band placed N and/or K on the early growth and development of maize, while the second experiment was set up to determine the influence of K placement through banding, topdressing and a combination of banding and topdressing on the early growth and development of maize. The first experiment was conducted from January to March 1999 with the cultivar PAN 6479. Two types of soil were used in the experiment, viz. a sandy loam soil collected from Ficksburg and a sandy soil collected from Boshof The plant density was maintained at three plants per pot and the experiment was terminated four weeks after seedling emergence. A complete randomized design with a factorial combination consisting of two main factors, viz. four N and/or K band application levels which were replicated thrice, was used in this experiment. The application rates were the equivalent of 0, 20, 40 and 60 kg N or K.ha-¹ for a row spacing of 1.5 m. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were measured to determine the influence of different N and/or K applications on the early growth and development of maize. All the plant parameters measured showed that the interaction of N and K applications had no significant influence on the early growth and development of maize. The best results were obtained with an application of 20 to 40 kg N.ha-¹• An application of 20 kg K.ha-¹ provided the best results. The second experiment was conducted from October to November 1999. With the exception of the fertilization procedure, all other aspects pertaining to the execution of this experiment were the same as those used in the first experiment. This experiment was terminated six weeks after seedling emergence. The experiment consisted of two main factors, viz. four levels and three methods of K application, arranged in a factorial combination in a complete randomized design with four replications. The application rates were the equivalent of 0, 20, 40 and 60 kg K.ha-¹ placed through banding, topdressing and a combination of banding and topdressing for a row spacing of 1.5 m. With regards to the combination application, half of K was banded and another half topdressed. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were studied to determine the effect of different levels of banded, top dressed and a combination of banded and topdressed K on the early growth and development of maize. All the plant parameters studied showed that the interaction of K application levels and methods had no significant influence on the early growth and development of maize. It seems the best results were attained with °to 20 kg K.ha-¹ The second experiment was conducted from October to November 1999. With the exception of the fertilization procedure, all other aspects pertaining to the execution of this experiment were the same as those used in the first experiment. This experiment was terminated six weeks after seedling emergence. The experiment consisted of two main factors, viz. four levels and three methods of K application, arranged in a factorial combination in a complete randornized design with four replications. The application rates were the equivalent of 0, 20, 40 and 60 kg K.ha-¹ placed through banding, topdressing and a combination of banding and topdressing for a row spacing of 1.5 m. With regards to the combination application, half of K was banded and another half topdressed. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were studied to determine the effect of different levels of banded, top dressed and a combination of banded and topdressed K on the early growth and development of maize. All the plant parameters studied showed that the interaction of K application levels and methods had no significant influence on the early growth and development of maize. It seems the best results were attained with °to 20 kg K.ha-¹. A combination of banding and topdressing in the sandy loam soil and topdressing alone in the sandy soil provided the best results. Finally, it is recommended that field trials should be conducted in order to verify these glasshouse results under field conditions.The second experiment was conducted from October to November 1999. With the exception of the fertilization procedure, all other aspects pertaining to the execution of this experiment were the same as those used in the first experiment. This experiment was terminated six weeks after seedling emergence. The experiment consisted of two main factors, viz. four levels and three methods of K application, arranged in a factorial combination in a complete randornized design with four replications. The application rates were the equivalent of 0, 20, 40 and 60 kg K.ha-¹ placed through banding, topdressing and a combination of banding and topdressing for a row spacing of 1.5 m. With regards to the combination application, half of K was banded and another half topdressed. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were studied to determine the effect of different levels of banded, top dressed and a combination of banded and topdressed K on the early growth and development of maize. All the plant parameters studied showed that the interaction of K application levels and methods had no significant influence on the early growth and development of maize. It seems the best results were attained with °to 20 kg K.ha-¹. A combination of banding and topdressing in the sandy loam soil and topdressing alone in the sandy soil provided the best results. Finally, it is recommended that field trials should be conducted in order to verify these glasshouse results under field conditions.. A combination of banding and topdressing in the sandy loam soil and topdressing alone in the sandy soil provided the best results. Finally, it is recommended that field trials should be conducted in order to verify these glasshouse results under field conditions.Item Open Access Influence of organic fertilisers on the yield and quality of cabbage and carrots(University of the Free State, 2008-11) Mbatha, Alice Nompumelelo; Engelbrecht, G. M.; Ceronio, G. M.English: The use of organic fertiliser as an alternative to inorganic fertiliser increased among subsistence farmers in rural areas in KwaZulu Natal. No clear recommendations exist for the application of different organic fertilisers on vegetables. Two field trials were conducted at Umsunduze Training Centre, KwaZulu Natal during the 2005 and 2006 seasons. The effect of three different organic fertilisers (chicken, kraal manure and compost) were investigated on the growth, yield and quality of cabbage cv. Conquistador and carrots cv. Kuroda. Four application rates were used for each organic fertiliser (chicken manure: 0, 6.25, 12.5 and 25 kg 10 m-2; kraal manure: 0, 12.5, 25 and 50 kg 10 m-2; compost: 0, 25, 50 and 100 kg 10 m-2). Each treatment combination was replicated four times. Organic fertilisers were incorporated into the soil one month before planting. Number of leaves and plant height were measured for the first 8 weeks after planting for both crops. Fresh and dry mass was determined at harvesting for both cabbage and carrots. Cabbage head and carrot shoulder diameter, carrot root length and carrot root total soluble solids were measured at harvesting. Both crops were graded (cabbage into 3 and carrots into 5 classes) according to their external appearance. After harvesting, soil analysis (2005 and 2006) and plant analysis (2006) were done for both crops. Chicken manure applied at 12.5 or 25 kg 10 m-2 showed a significant increase in the growth rate of cabbage during the first 8 weeks after transplanting in both seasons. During 2005, fresh mass of cabbage that received 12.5 or 25 kg 10 m-2 chicken manure was significantly higher and of better quality than the other organic fertiliser treatments. In 2006, the fresh mass and quality of cabbage that received 50 kg 10 m-2 kraal manure, 25 kg 10 m-2 chicken manure or 100 kg 10 m-2 compost was significantly higher than the other organic treatments. Dry mass also significantly increased when 25 kg 10 m-2 chicken manure was applied. Compost significantly increased the nitrogen, phosphorus, potassium, sulphur and calcium content, while kraal manure significantly increased the phosphorus, potassium and magnesium content of the soil after two years of application. It was in most cases the two highest application rates (Rate 2 and 3) that significantly influenced the chemical properties of the soil. Only chicken manure significantly influenced the nitrogen content of cabbage heads. Carrot plants that received chicken and kraal manure at Rate 2 or 3 produced the most number of leaves while the tallest carrot plants were obtained where 25 kg 10 m-2 chicken manure or 50 kg 10 m-2 compost was applied, at 8 weeks after planting. Different organic fertilisers and application rates did not significantly influence the fresh mass and root length of carrots. Dry mass of carrots that received 25 kg 10 m-2 chicken manure, 50 kg 10 m-2 kraal manure or 25 kg 10 m-2 compost was significantly greater than plants that did not receive any fertiliser in 2006. High organic fertiliser rates (Rate 3) significantly increased shoulder diameter. In 2005, chicken manure and compost significantly decreased total soluble solid content of carrots. In 2006, the highest total soluble solid content was obtained with 12.5 kg 10 m-2 chicken manure. An increase in the organic fertiliser rate promoted the development of hairy carrots in 2005 and carrots that received compost (Class 3) was of a poorer quality than those that received chicken or kraal manure (Class 2) in 2006. Compost significantly increased the phosphorus, potassium content and NIRS organic matter of the soil and kraal manure only significantly increased the sulphur content of the soil after two years of application. Chicken manure (25 kg 10 m-2) and 100 kg 10 m-2 compost significantly increased the nitrogen content of carrot roots, while the calcium content was significantly lowered where chicken manure was applied. Kraal manure significantly increased the iron content and 6.25 kg 10 m-2 chicken manure increased the total carbon content of carrots.Item Open Access Response of a sandy soil and maize plants to zinc fertilizers(University of the Free State, 2014) Wessels, C. F.; Du Preez, C. C.; Ceronio, G. M.English: Maize in Southern Africa is the most important crop for animal and human nutrition. Soil fertility, its management and understanding have an unmistakable role to play in modern agriculture. Maize is prone to zinc deficiency and is known to decrease yield as well as lowering nutritional value. Zinc is reported to be one of the most important micronutrients for the growth and development of maize. An incubation and glasshouse experiment was conducted to evaluate the response of plant available zinc in sandy soil when fertilized with ZnSO4, ZnO and ZnEDTA at different rates. For this purpose a range of extractants were used: HCl, Mehlich I, DTPA, EDTA and Ambic II. In the incubation experiment, two almost similar sandy soils differing only in acidity were treated with the three zinc fertilizers to increase the zinc content with 0 mg kg-1, 1 mg kg-1, 2 mg kg-1, 3 mg kg-1 and 4 mg kg-1. Each treatment was repeated five times. Fertilizers were applied as a solution, and after application soil went through three wetting and drying cycles before plant available zinc was determined in them. In the mentioned glasshouse experiment maize was planted in 40.5 L pots using a complete randomized block design. The same zinc fertilizers were used as for the incubation experiment but application rates differed. One of the soils used for the incubation experiment was selected and treated to increase its zinc content with 0 mg kg-1, 0.5 mg kg-1, 1 mg kg-1, 2 mg kg-1 and 4 mg kg-1. Phosphorus and nitrogen were added to the soil at a constant rate. Fertilizers were dissolved in water and applied as a solution on soil before thoroughly mixed. Maize were planted 50 mm deep and soil was maintained at drained upper limit during the growing period. During the five week growing period stem thickness, plant height and number of leaves were measured weekly while leaf area, root length, root mass and plant available zinc were measured at the end of the growing period. The experiment was repeated at two planting dates. After the growing period soil was sampled for zinc and phosphorus analysis. Concerning zinc source used, ZnSO4 was superior followed by ZnEDTA and ZnO in most of the measured plant parameters as well as plant available zinc content. Plant available zinc content at the end of the incubation experiment differed between the two soils. Extraction methods used to determine plant available zinc content led to different values. For both soils used in the incubation experiment Ambic II, DTPA and EDTA tend to extract more zinc than HCl and Mehlich I. Zinc fertilizers and application rates had a significant effect on plant parameters in the glasshouse experiment. The two plantings differed from each other. The effect of ZnO and ZnEDTA on aerial and subsoil growth parameters was not consistent throughout the glasshouse experiment. Most of the plant parameters showed an impaired development at increasing application rates. This phenomenon however did not occur in the plant available zinc content at the end of the growing period. Extraction method used to determine plant available zinc content at the end of the glasshouse experiment differed. However, the order differs from the results obtained in the incubation experiment. For both experiments the Ambic II and EDTA methods tend to extract the highest amount of zinc from the soil. Zinc source and application rate had a significant effect on both the concentration and uptake of zinc in/by maize. Again ZnSO4 was superior in increasing uptake and concentration of zinc by/in maize, with ZnO and ZnEDTA being inconsistent. Considering the reasons for this study it is clear that ZnSO4 was superior over ZnO and ZnEDTA. This could be attributed that with ZnEDTA and ZnO there were no compensation for the S in ZnSO4. Furthermore the ZnEDTA used was synthetically prepared and may be less effective than natural products. Zinc fertilizer and application rate also proved to have an effect on plant available zinc content and maize growth response.Item Open Access Response of maize to phosphorus and nitrogen fertilizers on a soil with low phosphorus status(University of the Free State, 2013) Coetzee, Pieter-Ernst; Ceronio, G. M.; Du Preez, C. C.Maize (Zea mays L.) is an important cereal crop not only in the world but more specifically in South Africa. Therefore, understanding maize’s nutrient requirement becomes an importance factor especially during the vegetative growth period. Nitrogen (N) and phosphorus (P) are reported to be two essential nutrients for both accelerated vegetative growth and maximum yield. Addition of these two plant nutrients should include consideration of both form and total nutrient concentration, since these two factors determine availability and accessibility. In order to evaluate the response of maize to P sources and P application rates as well as N sources a glasshouse experiment was conducted in 40.5 L pots filled with a dark brown sandy-loam topsoil pertaining a medium soil pH of 5.5. Treatments consisted of three main factor treatments viz. N source (urea and limestone ammonium nitrate - LAN), P source (monoammonium phosphate - MAP, nitrophosphate - NP and ammonium polyphosphate - APP) and P application rate (0, 10, 20, 30 and 40 kg P ha-1). Treatments combinations were replicated three times and independently subjected to a randomized complete block design with a factorial combination. The experiment was repeated on two planting dates. Treatments and treatment combinations were band applied to dry soil in a single 0.34 m line, 50 mm below and 50 mm away from the maize seeds; which were planted with a between row spacing of 0.91 m, 50 mm below the soil surface. After planting the soil was watered and maintained at field capacity for a duration of five weeks after emergence. The aerial parameters of three plants per pot were measured on a weekly basis following emergence while the subsoil parameters were taken at the end of the five week vegetative growing period. Both aerial and subsoil parameters showed responses to nitrogen source; which was strongly reflected during both plantings. Plants treated with LAN yielded both greater aerial and subsoil measurements compared to urea, primarily ascribed to immediate availability after application in addition to ease in uptake. Both aerial and subsoil parameter response to phosphorus source and P application rate, though apparent throughout both plantings, was more prominent during the first planting. Monoammonium phosphate and NP (orthophosphate sources) yielded greater aerial measurements compared to that of the APP (polyphosphate source). Subsoil parameter results comparing phosphorus sources were inconsistent. Subsoil parameters of the fertilized zone were significantly greater with the use of MAP (orthophosphate), while APP (polyphosphate) yielded significant greater subsoil parameters within the unfertilized zone. Both aerial and subsoil parameter measurements taken either throughout or at the end of the vegetative growth period were overall significantly greater when P was applied at 40 kg P ha-1. Subsoil parameter response in and away from the fertilizer band was however inconsistent. The aerial dry plant material was analyzed (Omnia Nutriology®) to evaluate the effect of the three main treatments on the quantitative nutrient concentration as well as the uptake thereof. Nutrient concentration and uptake was used to determine the synergistic or antagonistic effect of treatments or treatment combinations. Nutrient concentration measurements were inconsistent for N source, however total uptake proved to be more efficient with the application of LAN compared to urea. Both nutrient concentration and uptake was greater with the application of both the orthophosphate sources (MAP and NP) compared to the polyphosphate source (APP). The 40 kg P ha-1 application yielded a synergistic response to the total uptake of S, N, P, Ca and B, while a synergistic nutrient concentration response was found with the control treatment for N, Mg, Cu and Zn nutrients. Nutrient uptake was also stimulated by an increasing rate of P.Item Open Access Using seasonal rainfall with APSIM to improve maize production in the Modder River catchment(University of the Free State, 2011-11) Nape, Kholofelo Moses; Steyn, A. S.; Ceronio, G. M.English: In order to meet the food requirements of an ever-growing population, agricultural production needs to increase. This is especially true for maize production in South Africa as it is the staple food for a large portion of the rural indigenous population. Climate variability is one of the major causes of volatility in agricultural production and causes uncertainty for maize production at the subsistence level. Small-scale farmers within the Modder River Catchment have a poor quantative understanding of seasonal rainfall and their relationship to their management strategies. In countries prone to high seasonal climatic variability, crop growth models such as APSIM can be used to assist farmers in making decisions regarding the suitability of different management strategies. This means that climate forecasts could be translated into crop production, while alternative management practices would be associated with different economic outcomes. The opportunity arose to aid these farmers by optimising rainfed maize production. Subsequently, the objective of this study was to produce an advisory for small-scale rainfed maize farmers in the Modder River Catchment. Historical rainfall data (1950-1999) from selected rainfed maize production areas within the Modder River Catchment were used to calculate the seasonal rainfall totals for October to December (OND) and January to March (JFM). During dry seasons, the expected rainfall totals was less than 101.0 and 147.5 mm for OND and JFM, respectively. During wet seasons, the expected rainfall totals was more than 204.0 and 267.5 mm for OND and JFM, respectively. Recommended management practices were employed to validate APSIM using observed environmental and maize yield data for the 1980/81 to 2004/2005 seasons in the vicinity of Bloemfontein. Maize yields were simulated using two medium growth period cultivars (PAN 6479 and Pioneer 3237) under different planting dates, plant population densities, fertiliser applications and weeding frequencies. The model simulated PAN 6479 better than Pioneer 3237. For Pan 6479, the best set of management practices corresponded to a R2 of 0.66, D-index of 0.89, modelling efficiency of 0.59 and RMSEu/RMSE of 0.88. For Pioneer 3237, the modelling efficiency values under different management practices were negative. Stepwise linear regression was used to select those yield predictors that adhered to a partial R2 value greater than 0.0001 at a significance level of 0.15. In general it‟s usually better to plant early (November) regardless of the seasonal rainfall scenarios. Advisories were set up to convey information regarding the best, second best and worst set of management practices under each seasonal rainfall scenario. These advisories also include the related field costs along with potential yields and economic benefits at the 25, 50 and 75% probability levels for each set of management practices. For example, during AN-AN rainfall conditions, the best set of management practices involved planting during 16-30 November and 1-15 November, weeding twice, 50 and 75 kg ha-1 N and using 21 000 and 18 000 plants ha-1 for PAN 6479 and Pioneer 3237, respectively. Farmers would spend R1 798 ha-1 on field costs when planting PAN 6479, while obtaining a yield of 2 854 kg ha-1 and making a profit of R1 972 ha-1 at the 50% probability level. For Pioneer 3237 the field costs would amount to R2 338 ha-1, while realising a yield of 4 232 kg ha-1 resulting in a profit of R3 253 ha-1 at the same probability level. The recommended management practices under various seasonal rainfall scenarios could assist small-scale rainfed maize farmers to increase their yields and maximise the associated profit. Unfortunately, site-specific calibration of APSIM is required against observed sets of climate, soil and yield data for which the associated management practices are known before these advisories can be used by extension officers to advise small-scale farmers within the Modder River catchment.