Thesis (M. A. Agriculture (Agricultural Economics)) -- University of Limpopo, 2021 / Maize seeds differ according to varieties.The traditional maize varieties(also referred to as (Landraces)are maize varieties that have been cultivated and subjected to selection by farmers for generations.They retain a distinct identity and lack formal crop improvement. Improved maize varieties,on the other hand,are bred with characteristics such as drought and disease tolerance. This research was conducted to determine the attributes preferred by farmers when making a maize varietal choice.To be specific, the study aimed to achieve the following objectives:(i) Identify and describe socio economic characteristics of smallholder maize farmers’ in Mogalakwena Municipality; (ii) Analyse socioeconomic characteristics of smallholder maize farmers in Mogalakwena Municipality; (iii) Identify different maize varieties grown by smallholder farmers in Mogalakwena Municipality,and (iv) determine and analyse factors influencing farmers’choice ofa maize variety. Descriptive statistics and the Multinomial Logistic Regression Model were used for data analysis.The results of the study revealed that 64% of the respondents had formal education.This meant that they have the capability to grasp more information, if provided with trainings. It was found that 75% of the farmers did not have access to extension service which is supposed to play a significant role in agricultural information dissemination.The most grown maize variety was land race varieties which constituted 59.5%. This percentage was said to be resultant from limited access to the seed market. Infact,80% of the farmers had to travel an average of 42 kilomteres to access the market which also had a limited number of varieties.The Multinomial Logistic Regression Model revealed that only 5 variables (Educational level, farm size, yield, extension contact and knowledge of maize varieties )were significantat1%,5%,1%,1% and1%, respectively.The majority of farmers were old people with little access to extension service and an inadequate farming knowledge which lead to a highper centage of farmers continuing to grow landrace varieties. Based on the findings, this study recommend further research on attributes that influence farmers varietal choice and Government intervention in provision for resources and development of existing and new infracstrcture to encourage extension service delivery. Keywords:Landrace,improvemaizevariety,smallholderfarmer

Maize is the principal crop for food security and livestock feed in South Africa. It is also an industrial crop and the produce is exported to many countries in the world. Therefore there is high seed demand which prompts competition for breeding productive hybrids. However direct introduction of tropical hybrids into the warm temperate South African environments has not been successful. Competitive advantages can be obtained by implementing a “shuttle breeding” programme whereby part of the breeding is done in Zimbabwe and South Africa to minimise research and production costs. Introgression of temperate germplasm in tropical elite inbred lines can also be pursued to obtain adapted hybrids. The aim of this study was therefore to assess the effectiveness of introgression of temperate germplasm into tropical elite maize inbred lines as a strategy to enhance adaptability of new hybrids to South Africa, and also to determine both breeding and economic value of a “shuttle breeding” programme. To this end, the introgressed inbred lines and their hybrid progenies were evaluated in South Africa to determine the effect of the selection environment on their performance and genetic variation. Both genetic and economic gains were evaluated with a view to make recommendations to the small and medium scale enterprises with interests in the market. Introgression of temperate germplasm into tropical germplasm elite lines did not disrupt the heterotic groupings because most of the introgressed lines (86%) fitted into known existing heterotic groups. Only 14% of the introgressed lines did not show any inclination to towards the known heterotic clusters of their founder tropical parents. These lines were considered to be new recombinant inbred lines that showed little resemblance with their founder parents. Selection environment did not influence heterotic clustering of the introgressed lines, and genetic diversity was identified among introgressed lines developed in the same environment. Genetic variation was observed for the major economic traits and heritability of 21% to 91%. The introgression was effective for improving grain yield potential and ear prolificacy. Spearman’s rank correlation analysis on grain yield and ear prolificacy data showed significant positive correlation between selection environments such as Ukulinga in South Africa and Kadoma Research Centre in Zimbabwe. Therefore Kadoma Research Centre will be recommended for use in breeding new maize germplasm lines for South Africa. Correlation among traits showed that ear prolificacy and plant height had significant (P<0.05) direct effects on grain yield thus direct selection of these traits will be emphasised in breeding new hybrids. Introgression of temperate germplasm into tropical elite maize inbred lines was effective for improving their adaptation to warm temperate environments. Positive genetic gains of 5-58% were realised for grain yield potential and 26-46% for ear prolificacy. Whereas 1% to 37% gains were realised for secondary traits such as plant and ear height, anthesis and silking days there was barely any improvement for root and stalk lodging, and grain moisture content at harvest. However, introgressed lines displayed impressive performance per se and inter se indicating potential for commercial production. The new inbred line 71-DMLF7_88 combined early physiological maturity, high ear prolificacy and grain yield potential qualifying it as a perfect parent for the warm temperate environments. At least six hybrids were stable and adaptable while four were considered to be ideal genotypes relative to standard commercial hybrids such as PAN6Q445B which is a market leader. The exceptional hybrids, 12C20264, 12C22766, 13XH349 and 11C11774 will be advanced in South Africa. The study also indicated significant economic gains when a shuttle programme is implemented to breed new hybrids following the introgression strategy. The “Shuttle breeding” programme attained a positive net present value (NPV) of $1, 834, 166. 00. This indicated an increase in shareholder value through an opportunity cost of 17% and 3% relative to conventional breeding programmes which are based in South Africa and Zimbabwe, respectively. Positive NPV and genetic gain achieved using the “shuttle breeding” programme makes it a viable option for small and medium scale seed companies with intention to breed and commercialise competitive products in South African. In general, the study revealed that introgression of temperate germplasm into tropical elite inbred lines using a “shuttle breeding” programme was effective for enhancing adaptability of tropical germplasm to the South African warm temperate environments. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

The majority of small-scale farmers in the Eastern Cape apply inadequate quantities of manure, inorganic (NPK) fertilizer and Gromor as lone fertilizers or tend to mix manure or Gromor with chemical fertilizers for crops, without any scientific basis (Mkile, 2001). Hence this study – aimed at achieving effective and efficient use of chemical fertilizers, manure and Gromor, either as lone fertilizers or mixed with one another, in maize production – was established. A three-year dry land field experiment, arranged in a RCBD with 3 replicates where cattle manure, chemical fertilizer and Gromor were mixed at different ratios – as treatments FM1 (10 percent fertilizer + 90 percent manure); FM2 (25 percent fertilizer + 75 percent manure); FM3 (50 percent fertilizer + 50 percent manure); MAP (100 percent fertilizer); M (100 percent cattle manure); FG1 (10 percent fertilizer + 90 percent Gromor); FG2 (25 percent fertilizer + 75 percent Gromor); FG3 (50 percent fertilizer + 50 percent Gromor); G (100 percent Gromor) and a control (with nothing applied) – was conducted at the Nolukhanyo agricultural project at Bathurst in the Ndlambe Local Municipality. Maize cultivars PAN 6480 and Sahara were used as test crops. Manure, Gromor and soil were analyzed for their nutrient composition. Data recorded involving number of kernels per cob-1, grain and dry matter (DM) yields for the 2010-11, 2011-12 and 2012-13 seasons, and leaf area index (LAI) – were subjected to Genstat Version 14.1 for statistical analysis. Grain yields of PAN 6480 and Sahara recorded in seasons 2010-11, 2011-12 and 2012-13 were significantly higher (p≤0.05) than those of the controls. In 2012-13, PAN 6480 on treatments FG3 and FG1 produced the highest grain yields (5 327 and 5 107kg ha-1) respectively, while in 2010-11 the highest yield was 3 780kg ha-1. In the 2012-13 season, Sahara on F treatment was the highest with 4 553kg ha-1 whilst there were no significant differences in F and M treatments. Dry matter yields of Sahara were higher than those of PAN 6480 in all seasons. The highest Sahara LAI obtained on FM2 was 5.85 in the 2012-13 season, whereas PAN 6480 had LAI of 4.77 on F treatment, followed by FG3 with 4.72 LAI. PAN 6480 number of leaves for 6 plants in m2 and LAI in week 8 of the 2012-13 season had a positive correlation, r2=0.84. PAN 6480 number of kernels and cob length in the same area correlated quite well (r2 =0.91). Chemical fertilizer corrects the imbalances of nutrients inherent in organic manures and increases both maize grain yields and dry matter yields, and also influences number of leaves and LAI. Treatments FG1, FG3 and FM1 of PAN 6480 resulted in high maize grain yields when planted 13 in late November of the 2012-13 growing season and when water in the soil profile was conserved as a result of good rains received prior to planting. Treatments FG1 (10 percent fertilizer + 90 percent Gromor), FG3 (50 percent fertilizer + 50 percent Gromor) of PAN 6480 produced the highest grain yields (5 107kg ha-1 and 5 327kg ha-1 respectively) in the 2012-13 season, whilst FM1 (10 percent fertilizer + 90 percent manure) gave the highest grain yield (of 4 277kg ha-1) for the same cultivar in the 2010-11 season.

Maize (Zea mays L.) is one of the most important food crops in sub-Saharan Africa (SSA); however its production is constrained by many factors. Grain yield is compromised by poor genetic performance and poor agronomic management. This calls for need to develop hybrids and exploiting heterosis of single crosses which are adapted to challenging environments. Currently, there is no popcorn hybrids developed in South Africa which is adapted to local conditions. As such, there is need to develop hybrids that cater for smallscale farmers in marginal environments. The objectives of the study were to determine i) standard heterosis, levels of variation and heritability for phenotypic traits in dent and flint maize hybrids; ii) the association between genetic distances and phenotypic traits in dent and flint maize hybrids; iii) mid-parent heterosis in popcorn hybrids, iv) the effect of secondary traits on grain yield in dent, flint and popcorn hybrids; v) genetic diversity and the relationship between traits in widely grown selected hybrids in Southern Africa; and vii) to compare effectiveness of phenotypic analysis models for determining genetic distances between hybrids. Popcorn, dent and flint hybrids were evaluated at two sites. The data was analysed using SAS, Genstat and Power marker statistical packages. The results revealed that the relationship between genetic distance and heterosis is dependent on the environment. Hybrids in top 10 at both sites were different indicating that there was a significant genotype x environment interaction. 13 new heterotic patterns that performed better than the controls can be utilized in heterosis breeding; however there is need to test them in different environments to check on their stability. Grain texture cannot be used to discriminate hybrids for yield because all patterns of dent x dent, dent x flint and flint x flint were present in the top 10 hybrids. Lines DXL124 and DXL158 dominated parentage of the top 10 hybrid rank for yield qualifying them as potential testers for specific combining ability in future studies. Heterosis in popcorn hybrids that performed better than the mid-parent can be utilized in heterosis breeding to exploit vigour, though there is need to test the hybrids in a number of different environments. The main direct factors contributing to yield were ear prolificacy, ear aspect, number of plants and shelling percentages qualifying them to be selected to boost grain yield. Phenotypic data and 91 SNP markers were used to estimate the genetic distance between the hybrids. The results indicated that hybrids that were in the same cluster belong to the same brand and were related in origin and pedigree. Both molecular and phenotypic data were effective in discriminating the hybrids into different clusters according to genetic background. SNP markers revealed nine clusters of hybrids, 12-trait model revealed eight clusters and five-trait model revealed six clusters at 85% genetic distance. The study indicates strategies that can be adopted to boost grain yield in dent, flint and popcorn hybrids. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Maize production in Africa is constrained by abiotic and biotic stresses. Breeders need to have information on the nature of combining ability of parents, their traits and performance in hybrid combination. This requires careful determination of genetic variability of parents, and studying associations between grain yield and adaptive traits to breed superior cultivars which are better able to withstand such stresses. Therefore, this study was aimed at selecting parental testers with best combining ability in hybrid combination with recombinant inbred lines (RILs); and studying the correlation between grain yield and its components in eastern and western South Africa. It was also aimed at determining genetic variation and associations among adaptive traits in hybrids involving RILs. The final objectives of the study were to determine cultivar superiority of testcrosses involving RILs, and to select the best cultivars within and across four different environments. The 42 RILs were crossed to 9 Zimbabwean tropical testers resulting in 1009 hybrids with sufficient seed for planting in trials. From these a sample of 87 hybrids with adequate seed were selected and planted at four sites for combining ability analysis. The hybrids were evaluated at four sites in two regions; western region (Potchefstroom research station) and eastern region (Cedara, Ukulinga and Dundee research stations), during 2011/12 season. The experiments were laid out as augmented alpha lattice design. Trials were managed in accordance with production culture for each region. All quantitative data was subjected to GenStat and SAS statistical softwares. The results from combining ability study indicated that the line general combining ability (GCA) effects played a non-significant role (p > 0.05) in determining grain yield, grain moisture and anthesis date, while they were significant (p ≤ 0.05) for the other traits such as ear prolificacy. The tester main effects were significant for all the traits except ear prolificacy and plant height. Results also revealed that all the traits were controlled by both additive and non-additive genes, where additive gene action had the most contribution to the traits. The non-additive gene action played a minor role suggesting the total GCA effects attributed to both lines and testers predominantly higher over the specific combining ability (SCA) for all traits. In general the additive effects were preponderant over the non-additive gene effects. One cross (L114 x T12) had a significant and positive SCA effect for grain yield. The correlation between grain yield and secondary traits (number of ears per plant, grain moisture content, ear height, plant height, ear position and anthesis date) suggested that indirect selection can be employed to enhance grain yield by breeding for these particular adaptive traits. Path analysis showed that plant height had the highest direct and indirect effect on grain yield indicating its importance among other secondary traits for grain yield enhancement. Phenotypic coefficient of variation (PCV) was higher than genotypic coefficient of variation (GCV) for all the studied traits across all the four environments. All the traits displayed high heritability at Potchefstroom except anthesis date which was highly heritable at Ukulinga. Cedara was the second best site for heritability of all the traits except for the number of ears per plant. The genetic advance for grain yield was the highest at Cedara followed by Potchefstroom, Dundee and Ukulinga. The hybrids exhibited different patterns of variation and distribution for all the traits. This indicated that selection strategies to exploit GCA should be emphasised. Association studies among grain yield and secondary traits such as ear length, number of ears per plant, plant height, anthesis date, silking date and ear leaf area revealed that there were significant phenotypic correlations between grain yield and secondary traits, and among the secondary traits. Ear length had the highest direct effect on grain yield at Ukulinga; number of ears per plant had the highest direct effect on grain yield at Cedara and Potchefstroom; whereas plant height had the highest direct effect on grain yield at Dundee. Grain yield was least affected by indirect factors at all the sites except Ukulinga, where anthesis date had the highest indirect effect on grain yield through silking date followed by plant height through leaf area. The study reveals that there is significant variation among the hybrids for mean performance, indicating that there is opportunity for selection. Overall the findings suggest that direct selection would be appropriate to enhance grain yield. Path analysis revealed that plant height had the highest direct and indirect effects on grain yield, indicating that plant height can be further exploited as the main trait in future breeding programmes for grain yield increment. Hybrid 10MAK10-1/N3 was the best hybrid at Ukulinga in terms of grain yield, relative yield and economic traits. Whereas hybrid T17/L83 was the best hybrid at Cedara in terms of grain yield and relative yield; however, T11/L102 was selected as the most elite hybrid with respect to grain yield, relative yield and economic traits. Hybrid T3/L48 was identified as thebest hybrid at Dundee with respect to grain yield, relative yield and prolificacy. At Potchefstroom the standard check PAN6611 was identified as the best hybrid in terms of grain yield and relative yield followed by developmental hybrid T1/L28; however, developmental hybrid T1/L28 was the best in terms of earliness, prolificacy and ear aspect. Stability coefficients and cultivar superiority index across the sites revealed that four developmental hybrids were identified as best hybrids and they performed better than the standard check. These hybrids will be recommended for further testing in advanced trials. With respect to cultivar superiority, the desired hybrids are required to combine high grain yield with economic and adaptive traits such as high ear prolificacy, low grain moisture, and low ear aspect score (desired) for them to adapt to production environments in South Africa. There was significant variation among the top 25 yielding hybrids. At least 5 hybrids combined high grain yield with the desired complimentary adaptive traits such as quick moisture dry down, prolificacy and ear aspect. The results showed that there is variation in the performance of high yielding genotypes within all the sites, and that agronomically superior cultivars can be identified. The study shows that there is significant variation among the RILs since they interacted differently with the 9 tropical testers. Even among the top 25 selections of RILs in each environment there was still variation for combinations of the desired traits. Significant associations among grain yield and other economic and adaptive traits were observed with implications for breeding strategy. Above all the significant variation gives large score for future breeding of new unique lines. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Low cover crop biomass production is a major obstacle to the success of conservation agriculture currently promoted as panacea to the inherent problem of soil erosion and loss of soil productivity in the Eastern Cape (EC). Therefore, this study evaluated cover crop management strategies for optimizing biomass production for better soil cover, soil nitrogen (N) and phosphorus (P) fertility, weed control and maize yields. The strategies tested are cover crop bicultures, selection of an adapted lupin cultivar and seeding rate, and the feasibility of rain fed winter cover cropping. The cover crop experiments were carried in rotation with summer maize between the winter of 2009 and summer of 2010/2011. Biculture trial was carried out by seeding oat (Avena sativa) and vetch (Vicia dasycarpa) at three mixture ratios and as sole crops under irrigation. On a separate irrigated trial, two lupin cultivars (Lupinus angustifolius var Mandelup & Qualinock) were seeded to a range of seeding rate, 40 to 220 kg ha-1. To study the feasibility of rain fed winter cover cropping, oat, vetch, rye (Lolium multiflorum), barley (Hordeum vulgare), radish (Raphanus sativa) and triticale (Triticale secale) were relayed into a maize crop in February, March and April of 2010. The irrigated trials were followed with SC701 maize cultivar, whilst the rain fed trial was followed with DKC61-25 maize cultivar. Bicultures gave higher cover crop biomass than sole vetch, increasing with an increase in the oat component of the mixture. Increased N and P uptake was observed with bicultures compared to sole oat, however, the levels were comparable to sole vetch. Sole vetch increased soil inorganic N and P at maize planting, whilst the slow decomposition by sole oat residue resulted in mineral lock up. Bicultured cover crop residues had intermediate decomposition rates and resulted in optimum levels of inorganic N and P for prolonged periods compared to sole crops. Weed suppression by the bicultures was comparable to sole cover crops. Biculturing technology significantly (P<0.05) increased maize grain yield compared to sole oat and the yields were comparable to those from sole vetch. For lupins, 206 kg ha-1 seeding rate gave the optimum biomass yield. Weed dry weights in both cover crop and maize crop decreased with an increase in lupin biomass. Comparable soil total N and inorganic P values at maize planting, were observed from plots planted to 120, 180 and 220 kg ha-1. Maize grain yield increased with an increase in lupin seeding rate. The study on rain fed winter cover cropping had most cover crop species’ biomass decreasing with each delay in planting except for radish, which increased. Vetch produced the highest amounts of biomass from February and March planting whilst radish had the highest biomass in April planting. The two species resulted in the greatest N improvement compared to the other species. Regardless of the grazing, the grass specie residues managed to persist to the next cropping season and the residue remaining were comparable to that of radish and vetch. Late-planted cover crops had the greatest residue remaining than early-planted, as a result, April planted cover crops provided better weed suppression than March and April planted. Vetch provided the highest maize grain yield (4005 kg ha-1) whilst all other species tested had comparable grain yields. The results suggested that bicultures could be grown to give sufficient biomass for both weed suppression and soil fertility improvement. Furthermore, increasing lupin plant densities improve its function as a cover crop with respect to weed suppression, soil fertility improvement and maize yields. The study also showed that for dry land systems, February and March planted vetch and April planted radish can provide the greatest biomass and maize yield improvement.

Genetically modified (GM) white and yellow maize, Zea mays, has been commercially released and cultivated in South Africa since 1997/1998. The traits expressed are insect resistance and herbicide tolerance conferred by the bacteria Bacillus thuringiensis (Bt) Cry genes and Agrobacterium 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase gene, respectively. The Cry genes have been used widely to control lepidopteran insect pests but insect resistance to GM Bt crops has been a concern since the introduction of this technology. A management strategy includes refugia planting of 5% non-Bt plants, with no insecticide application, and 20%, where insecticide application is allowed. These refugia are designed to allow the survival of insect pests within restricted planted zones. However, in South Africa there are reports of Bt-resistant stem borer (Busseola fusca) (Fuller) (Lepidoptera: Noctuidae) and non-compliance with refuge planting. The aims of this study were two-fold: 1. To conduct a survey among KwaZulu-Natal (KZN) GM maize growers to ascertain information such as level of compliance with refuge planting and to determine which refugia were predominantly planted and reasons thereof; 2. To conduct a replicated field trial to determine yield, insect borer damage and economic benefit of the 5% unsprayed and 20% sprayed refuge options (including three configurations namely strip, perimeter and block and a 5 and 20% ‘refuge-in-a-bag’ option). The survey indicated that 28 out of 29 (96.6%) KZN Bt maize growers plant the 5% non-sprayed refuge with 27 (96.4%) of those respondents planting the strip configuration for the purpose of insect management (75%) and ease of planting (32.2%). The survey also showed that 7 (seven) i.e. 21.9% of KZN Bt maize growers observed borer damage and although growers are now fully compliant with refugia planting requirements, initially 7 respondents (24.1%) did not comply with or plant refugia correctly. Furthermore, 7 respondents reported insect borer damage in their maize with 4 of the 7 instances (57.1%) likely stemming from incorrectly planted refugia. vii No significant differences in yield or insect damage were observed between the 5 and 20% refugia for any of the planting configurations in the field trial. However due to costs involved with insecticide application and labour required for the operation in the 20% option, these treatments were less economically advantageous than the non-Bt control. The 20% block and strip configurations had a cost benefit ratio of ZAR 7.21 and ZAR 6.67 respectively, earned per R1 spent by the grower compared with ZAR 7.76 in the sprayed control. The cost-benefit comparison for the 5% block and strip configurations was ZAR 8.48 and ZAR 7.71, respectively compared with ZAR 9.44 in the unsprayed control. In addition, the 20% seed mixture limited borer damage to 4.95% when compared with 15.77% damage in the sprayed control (ANOVA, F pr = 0.124). The seed mixtures are not available commercially and the results from the survey indicated that some education and marketing by the seed companies would be advisable prior to their release to the farming community. In order to determine which of the refuge options between 5 and 20% would be more advantageous for growers overall, regardless of the planting configuration; data were grouped and analysed. There were no significant differences in either the yield or insect damage for the 5 and 20% refugia, but the cost-benefit calculations indicated that the 5% option was more cost effective – for the 5 and 20% refugia, ZAR 7.97 and ZAR 7.15 respectively, earned per ZAR 1 spent by the grower (ANOVA, F pr. = 0.03). This is because no insecticide was used in the 5% treatments. Mean ear damage comparisons between the 5 and 20% refugia showed that the 20% refuge in the perimeter configuration incurred the least damage (2.65% ear damage) compared with 5% perimeter (10.86% ear damage), although the reasons for this are not clear. While the results of the field trials showed no significant differences in insect damage and yield with regard to choice of refuge configuration, monitoring insect resistance management remains an integral part of Bt maize crops in South Africa, in order to delay further resistance development and to prolong the viability of Bt technology. / Agriculture and  Animal Health / M. Sc. (Agriculture)

Genetically modified (GM) white and yellow maize, Zea mays, has been commercially released and cultivated in South Africa since 1997/1998. The traits expressed are insect resistance and herbicide tolerance conferred by the bacteria Bacillus thuringiensis (Bt) Cry genes and Agrobacterium 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase gene, respectively. The Cry genes have been used widely to control lepidopteran insect pests but insect resistance to GM Bt crops has been a concern since the introduction of this technology. A management strategy includes refugia planting of 5% non-Bt plants, with no insecticide application, and 20%, where insecticide application is allowed. These refugia are designed to allow the survival of insect pests within restricted planted zones. However, in South Africa there are reports of Bt-resistant stem borer (Busseola fusca) (Fuller) (Lepidoptera: Noctuidae) and non-compliance with refuge planting. The aims of this study were two-fold: 1. To conduct a survey among KwaZulu-Natal (KZN) GM maize growers to ascertain information such as level of compliance with refuge planting and to determine which refugia were predominantly planted and reasons thereof; 2. To conduct a replicated field trial to determine yield, insect borer damage and economic benefit of the 5% unsprayed and 20% sprayed refuge options (including three configurations namely strip, perimeter and block and a 5 and 20% ‘refuge-in-a-bag’ option). The survey indicated that 28 out of 29 (96.6%) KZN Bt maize growers plant the 5% non-sprayed refuge with 27 (96.4%) of those respondents planting the strip configuration for the purpose of insect management (75%) and ease of planting (32.2%). The survey also showed that 7 (seven) i.e. 21.9% of KZN Bt maize growers observed borer damage and although growers are now fully compliant with refugia planting requirements, initially 7 respondents (24.1%) did not comply with or plant refugia correctly. Furthermore, 7 respondents reported insect borer damage in their maize with 4 of the 7 instances (57.1%) likely stemming from incorrectly planted refugia. vii No significant differences in yield or insect damage were observed between the 5 and 20% refugia for any of the planting configurations in the field trial. However due to costs involved with insecticide application and labour required for the operation in the 20% option, these treatments were less economically advantageous than the non-Bt control. The 20% block and strip configurations had a cost benefit ratio of ZAR 7.21 and ZAR 6.67 respectively, earned per R1 spent by the grower compared with ZAR 7.76 in the sprayed control. The cost-benefit comparison for the 5% block and strip configurations was ZAR 8.48 and ZAR 7.71, respectively compared with ZAR 9.44 in the unsprayed control. In addition, the 20% seed mixture limited borer damage to 4.95% when compared with 15.77% damage in the sprayed control (ANOVA, F pr = 0.124). The seed mixtures are not available commercially and the results from the survey indicated that some education and marketing by the seed companies would be advisable prior to their release to the farming community. In order to determine which of the refuge options between 5 and 20% would be more advantageous for growers overall, regardless of the planting configuration; data were grouped and analysed. There were no significant differences in either the yield or insect damage for the 5 and 20% refugia, but the cost-benefit calculations indicated that the 5% option was more cost effective – for the 5 and 20% refugia, ZAR 7.97 and ZAR 7.15 respectively, earned per ZAR 1 spent by the grower (ANOVA, F pr. = 0.03). This is because no insecticide was used in the 5% treatments. Mean ear damage comparisons between the 5 and 20% refugia showed that the 20% refuge in the perimeter configuration incurred the least damage (2.65% ear damage) compared with 5% perimeter (10.86% ear damage), although the reasons for this are not clear. While the results of the field trials showed no significant differences in insect damage and yield with regard to choice of refuge configuration, monitoring insect resistance management remains an integral part of Bt maize crops in South Africa, in order to delay further resistance development and to prolong the viability of Bt technology. / Agriculture and  Animal Health / M. Sc. (Agriculture)

Recurring drought conditions have always been an endemic feature of climate in South Africa, limiting maize development and production. However, recent projections of the future climate by the Intergovernmental Panel on Climate Change suggest that due to an increase of atmospheric greenhouse gases, the frequency and severity of droughts will increase in drought-prone areas, mostly in subtropical climates. This has raised major concern for the agricultural sector, particularly the vulnerable small-scale farmers who merely rely on rain for crop production. Farmers in the Luvuvhu River catchment are not an exception, as this area is considered economically poor, whereby a significant number of people are dependent on rain-fed farming for subsistence. This study was therefore conducted in order to improve agricultural productivity in the area and thus help in the development of measures to secure livelihoods of those vulnerable small-scale farmers. Two drought indices viz. Standardized Precipitation Evapotranspiration Index (SPEI) and Water Requirement Satisfaction Index (WRSI) were used to quantify drought. A 120-day maturing maize crop was considered and three consecutive planting dates were staggered based on the average start of the rainy season. Frequencies and probabilities during each growing stage of maize were calculated based on the results of the two indices. Temporal variations of drought severity from 1975 to 2015 were evaluated and trends were analyzed using the non-parametric Spearman’s Rank Correlation test at α (0.05) significance level. For assessing climate change impact on droughts, SPEI and WRSI were computed using an output from downscaled projections of CSIRO Mark3.5 under the SRES A2 emission scenario for the period 1980/81 – 2099/100. The frequency of drought was calculated and the difference of SPEI and WRSI means between future climate periods and the base period were assessed using the independent t-test at α (0.10) significance level in STATISTICA software. The study revealed that planting a 120-day maturing maize crop in December would pose a high risk of frequent severe-extreme droughts during the flowering to the grain-filling stage at Levubu, Lwamondo, Thohoyandou, and Tshiombo; while planting in October could place crops at a lower risk of reduced yield and even total crop failure. In contrast, stations located in the low-lying plains of the catchment (Punda Maria, Sigonde, and Pafuri) were exposed to frequent moderate droughts following planting in October, with favorable conditions noted following the December planting date. Further analysis on the performance of the crop under various drought conditions revealed that WRSI values corresponding to more intense drought conditions were detected during the December planting date for all stations. Moreover, at Punda Maria, Sigonde and Pafuri, it was observed that extreme drought (WRSI <50) occurred once in five seasons, regardless of the planting date. Temporal analysis on historical droughts in the area indicated that there had been eight agricultural seasons subjected to extreme widespread droughts resulting in total crop failure i.e. 1983/84, 1988/89, 1991/92, 1993/94, 2001/02, 2002/03, 2004/05 and 2014/15. Results of Spearman’s rank correlation test revealed weak increasing drought trends at Thohoyandou (ρ = of 0.5 for WRSI) and at Levubu and Lwamondo (ρ = of 0.4 for SPEI), with no significant trends at the other stations. The study further revealed that climate change would enhance the severity of drought across the catchment. This was statistically significant (at 10% significance level) for the near-future and intermediate-future climates, relative to the base period. Drought remains a threat to rain-fed maize production in the Luvuvhu River catchment area of South Africa. In order to mitigate the possible effects of droughts under climate change, optimal planting dates were recommended for each region. The use of seasonal forecasts during drought seasons would also be useful for local rain-fed maize growers especially in regions where moisture is available for a short period during the growing season. It was further recommended that the Government ensure proper support such as effective early warning systems and inputs to the farmers. Moreover, essential communication between scientists, decision makers, and the farmers can help in planning and decision making ahead of and during the occurrence of droughts. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)