An adequate characterization of soil hydraulic properties is a necessary solution for agriculturally and environmentally oriented problems such as irrigation, drainage, runoff and pollutants movement. The three approaches to determine hydraulic properties of soils are field measurements, laboratory measurements and mathematical models. In situ measurements, though representative, have the inherent limitation of being costly and time consuming. Laboratory and mathematical techniques are more convenient but require extensive comparison to field results as bench mark for evaluation. The objective of this study was to characterize the hydraulic properties of Bainsvlei and Tukulu form soils utilizing the above mentioned three approaches and to compare the results. The laboratory methods selected were hanging water column and pressure plate apparatus. Undisturbed soil samples were used to determine θ-h relationships at 0-100 kPa suctions and disturbed soil samples up to 1500 kPa. The water retention characteristics for both soils were generally well defined with little variability between replicates. The main variations were due to texture differences between the horizons. The θ-h relationships were used to estimate textural and structural domains using empirical pore class limits and derivative curves. The suction value separating the structural domain from the textural domain varies from horizon to horizon. The boundary between soil pore categories cannot be taken as a fixed value for all soils and all types of soil use. The measured water retention data corresponded well with the fitted curve via the van Genuchten (1980) model, indicating that the model can be successfully used to describe θ-h relationships for Bainsvlei and Tukulu soils. Soil water sensors were calibrated using undisturbed soil samples in climate controlled room for five horizons of a Bainsvlei form soil and three horizons of a Tukulu form soil. Soil water sensors and circuitry show extremely low sensitivity to temperature fluctuations. Horizon specific calibration is essential to get accurate water content estimates from the sensors if used in different soil horizons. Our study demonstrate that horizon specific calibrations of the water sensors improves the accuracy of soil water content monitoring compared with the manufacturerâs generic calibration equation for the soils tested in this study. Hydraulic conductivity was obtained by measuring the hydraulic head and water content of the Bainsvlei soil form in situ with tensiometers and horizon specific calibrated ECH2O EC-20 probes, respectively. The profile was characterized with several relations of hydraulic conductivity and varied with depth. The reason for this was attributed to heterogeneous nature of the profiles due to variation in particle size distribution. The van Genuchten (1980) model laboratory method was used to predict K-θ relationships utilizing laboratory determined θ-h relationships. The K-θ relationships predicted from the θ-h relationships of the soil cores corresponded well with those determined by the instantaneous profile field method for water contents which they have in common. Thus it appears that this laboratory method is applicable to the soils studied, but the accuracy of the predicted values is quite sensitive to the matching factors. Thus, accurate measurement of these parameters is necessary for its successful use. The instantaneous profile field method is regarded as a reference method to measure in situ unsaturated hydraulic conductivity for both homogenous and layered soils (Hillel et al., 1972). There are, however, several site or profile characteristics that may limit this method (Bouma, 1983). Our studies show that it is not applicable on duplex soils with slow permeable C-horizons i.e. the Tukulu form profile at Paradys, because of negative hydraulic gradients within the profile due to impaired internal drainage. There is a need to adapt this method to duplex soils. Overall results indicate that from a practical perspective, the prediction of K-θ relationship from laboratory determined water retention data can be a viable alternative for determining the hydraulic properties of diagnostic horizons. The prediction of DUL using θ-h relationship has been found to be satisfactory.

A recently commercialized natural bio-stimulant, ComCat®, that contains three active brassinosteroids (BRs) of which two were identified previously, was scrutinized in this study for its potential to be applied in the agricultural industry. Concerning objective (1), seven biotests were employed to quantify the bio-stimulatory activity of ComCat® under laboratory and glasshouse conditions. The product was tested at different concentration levels and the 0.5 mg â-1 application repeatedly emerged as the optimum concentration in terms of contributing towards increases in all of the parameters measured. Treatment with ComCat® had little or no effect on seed germination, but especially root growth of seedlings from different crops was significantly and consistently induced. Concerning objective (2), two cultivars for each of five test crops were treated with ComCat® over two growing seasons under field conditions in order to ascertain their yield response. Some of the test crops, but not all, showed cultivar sensitivity to treatment with ComCat®. However, overall the significant yield increases measured in one or both cultivars of the five different test crops and in one or both seasons confirmed the potential of ComCat® to be applied in agriculture and to contribute to economic prosperity for a farmer. Concerning objective (3), gas chromatographic analyses of a crude extract of the product as well as semi-purified fractions thereof by, using internal BR standards, were employed to identify an unknown BR contained in ComCat®. This was confirmed to be 24-epi-brassinolide. The latter as well as the previously identified 24- epi-castasterone and 24-epi-secasterone are known to be active BRs of the brassinosteroid group. In conclusion, the bio-stimulatory characteristic of ComCat® was confirmed both in vitro and in vivo under laboratory, glasshouse and field conditions in this study. Significant yield increases in all of the test crops over two seasons in some instances, confirmed the potential of ComCat® to be applied sustainably in the agricultural practice. Based on the results obtained in this study, three possible application methods of ComCat® are suggested. These include 1) seed treatment, 2) foliar application or 3) soil application.

Farmers have largely depended on intensive soil cultivation to reduce nutrient stratification and therefore distribute nutrients homogeneously across the root zone for optimum crop productivity. This attempt however, has led to serious soil organic matter degradation and nutrient outflows. Consequently, food production for the increasingly growing world population was severely threatened. Crop residues as a source of organic matter and nutrients, when properly managed, can restore or improve soil fertility, and hence crop yields. The different residue management practices on some soil fertility indicators have been examined since 1979 in a long-term wheat trial at the ARC-Small Grain Institute near Bethlehem in the Eastern Free State on an Avalon soil. The observations established in 1999 indicated that soil nutrient and organic matter stratification still continues, therefore it was found necessary to further investigate the effects of these residue management practices on some soil fertility indicators, nutrient uptake and wheat grain yield. The applied field treatments include two methods of straw disposal (unburned and burned), three methods of tillage (no-tillage, stubble mulch and ploughing) and two methods of weeding (chemical and mechanical). Soil samples were collected in 2010 at various depths viz. 0-50, 50-100, 100-150, 150-250, 250-350 and 350-450 mm and analyzed for organic C, total N and total S as organic matter indices, pH, some macronutrients (P, K, Ca, Mg and Na) and CEC, as well as some micronutrients (Cu, Fe, Mn and Zn). At mid-shooting stage, plants were sampled in each treatment plot, oven-dried at 68 ºC, weighed, milled and analyzed for N, S, P, K, Ca, Mg, Na, Cu, Fe, Mn, and Zn. The grain yield data of wheat for the 26 years were supplied by the ARC-Small Grain Institute for use as a supplement to the soil data. The methods of straw disposal and tillage had variable influences on soil organic matter indices. Unburned straw increased total N and S, but reduced organic C when compared to the burned straw. No-tillage increased organic C only in the 0-50 mm soil depth when compared to stubble mulch and ploughing. No-tillage and stubble mulch resulted in a higher total N to a soil depth of 450 mm relative to mouldboard ploughing. Ploughing on the other hand, and to some extent stubble mulch, increased total S more than no-tillage in the upper 250 mm soil depth. Mechanical weeding enhanced these indices to 450 mm soil depth as opposed to chemical weeding. No-tillage and to some extent stubble mulch suppressed acidification in the upper 100 mm and lower 350-450 mm soil depths. Mechanical weeding also increased soil pH when compared to chemical weeding. No-tillage combined with either chemical weeding or straw burning suppressed acidification in the surface soil, whereas mechanical weeding combined with either no-tillage or mouldboard ploughing retarded acidification in the subsoil. The concentrations of P, K, Mg, Mn and Zn were higher in the burned treatments than in the unburned plots. The reverse was observed with Ca, Na and Cu. In contrast, mouldboard ploughing, and to some extent stubble mulch, resulted in an accumulation of Cu in the upper 100 mm soil depth when no-tillage served as a reference. Chemical weeding enhanced P, K, Mg, Na and CEC, but resulted in lower Ca, Cu, Fe, Mn and Zn contents when compared to mechanical weeding. The applied management practices were also tested on nutrient uptake and grain yield. Although not always significant, the burned straw increased nutrient uptake, but resulted in a lower wheat grain yield when compared to unburned straw. Despite the beneficial effects of no-tillage and stubble mulch on the fertility status of this Avalon soil, higher nutrient uptake and grain yield were perceived under mouldboard ploughing. Mechanical weeding also enhanced the uptake of most of the studied nutrients relative to chemical weeding. Mouldboard ploughing combined with either unburned straw or chemical weeding increased nutrient uptake and wheat grain yield. However, irrespective of the applied field treatments, nutrient concentrations in oat straw were below optimum levels, and possibly plants were already suffering acute nutrient deficiencies.

The influence of temperature on yield and quality of carrots were examined using two pot trials that were conducted in the glasshouse and growth chambers at the Department of Soil, Crop and Climate Sciences, on the Bloemfontein campus of the University of the Free State in 2009 and 2009/10. In the first trial the influence of four temperatures (10, 18, 26 and 32°C) on the growth, yield and quality of two pre-pack carrot cvâs. Nectar and Star 3002 were studied. Carrot seed were sown in 0.34 m x 0.34 m x 0.35 m pots, filled with topsoil of the sandy loam Bainsvlei form. Pots were kept in the glasshouse at 20°C (±1°C) for four weeks to allow the seedlings to establish and reach the first true leaf stage whereupon they were moved to the controlled environment chambers at different temperatures for 20 weeks. Growth parameters such as leaf number, plant height and leaf growth were significantly influenced by temperature and all these parameters performed the best at 10°C at the end of the growth season irrespective of cultivar. Root fresh and dry mass did not differ significantly between the two cultivars but the affect of temperature was significant. The highest root fresh mass for both cultivars was also obtained at 10°C, with âStar 3002â with the highest mass (39.12 g) followed by âNectarâ (34.26 g). Both cultivars exhibited the highest root dry mass at the lower temperature treatment (10°C) with âStar 3002â having a higher root dry mass (4.15 g) than âNectarâ (3.87 g). External quality parameters such as root length and diameter differed significantly between the temperature treatments and only the length of carrot roots did not differ significantly between the cultivars. Both âNectarâ and âStar 3002â exhibited the longest roots at 10°C and the shortest roots at 18°C. Root diameter for both cultivars was significantly greater at 10°C than at 18°C. The only defects observed were green shoulder and misshapen roots. Although not significant, the percentage green shoulders and misshapen roots were higher at 18°C than at 10°C. Carrots were significantly firmer at the low temperature (10°C) than at 18°C. The total soluble solid content of carrots however, grown at 18°C was significantly higher than those grown at 10°C. In the second pot trial the influence of four dual temperatures (15/5, 24/10, 28/20 and 35/25°C) on the growth, yield and quality of two pre-pack carrot cultivars âNectarâ and âCS 1006â was studied. Based on the results of this study, temperature influenced leaf number and plant height of both cultivars, although not always significantly, during the 32 weeks of growth. Leaf number and plant height of carrot plants were greater at 15/5°C treatment. Yield parameters and the external quality parameters such as root length; diameter and absence of defects were also influenced significantly by temperature. Carrot root length and diameter were significantly influenced positively by lower temperatures (15/5°C) and absence of defects such as green shoulder and hairiness were significantly influenced negatively by higher temperatures (28/20°C). Some of the internal quality parameters such as firmness, total soluble solids, carotene, β-pinene and caryophyllene were also significantly affected by temperature. Firmness, total soluble solids and carotene were significantly influenced by lower temperature (15/5°C) whereas β-pinene and caryophyllene were significantly influenced by higher temperatures (28/20°C). Free choice profiling (FCP) was carried out in order to investigate how semi-naïve panelists described and perceived carrot samples cultivated under different temperature conditions. This method allowed participants to use their own attributes to describe and quantify the food product. The FCP procedure generated six descriptors on the attribute taste and one on aftertaste. The two carrot cultivars grown at the higher temperatures (24/10 and 28/20°C) had descriptors like bitter, sour, bland and chemical, with a definite aftertaste while carrot cultivars grown at lower temperatures (15/5°C) had descriptors such as sweet and carrot taste

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 itâs 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.

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Lignocellulosics (LC) are the most abundant and under-utilised renewable resource of energy in the world. The present study is concerned with finding alternative uses to LC as an animal feed using environmentally friendly technologies. The major biological constraint for using LC is related to the low accessibility of cell wall polysaccharides to both cell-free and microbial enzymes. This can only be overcome by some type of processing. This study emphasises the use of physical (steam) and biological (enzymic) treatments. Results have shown that both low (LT) and high temperature steam treatment (HT) are efficient methods for solubilising hemicellulosic sugars and depolymerising lignin. However, HT leads to higher losses of both sugar and dry matter. Higher improvement in fibre bio-availability was obtained with HT and yet, this effect was more evident from enzymic hydrolysis data compared to rumen fermentation. LT can be used for upgrading LC since exogenous chemicals are added. HT showed to be an attractive alternative for producing animal feed and substrate for enzymic saccharification without requiring chemicals. The effects of steam treatment on fibre physical structure were particularly important. Greater effect was noticed under HT in combination with rapid decompression. It was suggested that rapid decompression should be avoided in the context of animal feeding. Experiments on toxic compounds indicated that furans have negligible toxicity to rumen micro-organisms. Phenolic compounds, however, are potentially toxic and can affect the pattern of rumen fermentation, gas production and adhesion of bacteria to substrate.

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