Improved hybrid genetics and more efficient farming techniques have increased corn (Zea mays L.) production and grain yields for Mid-South farmers. Early planting is one technique to mitigate heat and drought stress that negatively influence grain production. The first objective was: a) determine the effect of early planting on grain yield, b) to determine the effects on physiological characteristics and c) determine if some hybrids are better suited for early planting. Data suggest there were yield advantages for early planted treatments. Starkville 2014 yields exhibited the greatest reduction of .80 Mg ha-1 for each week that planting was delayed. A second objective was: a) determine optimum plant density when planting early, b) determine population effects on physiological characteristics, and c) determine hybrid responses. Hybrids were evaluated at seeding rates ranging from 49,400 to 98,800 plants ha-1. Corn grain yield was maximized at 86, 450 to 98,800 plants ha-1.

Thesis (M.A. Agricultural Administration (Pasture Science)) -- University of Limpopo, 2014 / In the summer rainfall areas of South Africa small scale farmers, as well as commercial farmers experience low animal production due to a lack of good quality roughage. The nutritional value of the rangeland cannot maintain livestock during autumn and winter. Producing winter fodder could be expensive and literature showed that planting fodder radish and turnip might be a cheap relative option (not in sweet veld). Winter supplementation contributes largely to high input costs in livestock production, which can make this enterprise uneconomically. For this reason alternative winter feeding strategies should be investigated, like the use of Brassica and Raphanus species for feed supply, of high quality, in winter. Two Localities [Syferkuil, (University of Limpopo’s experimental farm (Limpopo) and Dewageningsdrift, (Hygrotech Experimental farm (Gauteng)] were used for this research project. On the two localities three different factors were tested:  Three planting dates (February, March and April)  Three cultivars (Nooitgedacht fodder radish, Forage star turnip (not on Syferkuil) and Mammoth purple top turnip)  Three cutting frequencies (first cut10 weeks after planting + regrowth; first cut 14 weeks after planting + regrowth and 18 weeks after planting, no regrowth). Samples (for dry matter production and nutritional value analysis) were collected at both localities as per cutting frequency treatments during the 2007 growing season. The samples were used to evaluate the influence of the mentioned treatments on total dry matter production, nutritional value, leaf production and tuber production of the three cultivars. At Syferkuil the DM production Nooitgedacht fodder radish was higher (5.23 to 5.9 t/ha) than that of Mammoth purple top turnip (3.24 t/ha) when planted in February. The same trend was seen during the March planting date (4.7 t/ha and 3.6 t/ha respectively for 18 W treatment). During the April planting date the highest production was higher (5.07 t/ha and 5.13 t/ha respectively) than that of the March iv planting date. The 10 Weeks + Re-growth cutting treatment resulted in general in the lowest production. At Dewageningsdrift (Gauteng) Nooitgedacht fodder radish produced the highest of all three cultivars at the 18 Weeks treatment, with the highest when planted in March (7.67 t/ha), 5.5 t/ha when planted in April and 5.3 t/ha when planted in February. For the rest of the treatments the DM production of Nooitgedacht varied between 2.9 t/ha and 4.6 t/ha. The highest DM production of Forage star turnip was 3.01 t/ha (10 W+R, February planting date), 1.35 t/ha (14 Weeks + Re-growth, March planting date) and 2.34 t/ha (18 Weeks, April planting date). The highest DM production of Forage star turnip was 2.96 t/ha (18 Weeks, February planting date), 2.59 t/ha (14 Weeks + Re-growth, March planting date) and 4.1 t/ha (18 Weeks, April planting date). An estimation of the grazing/feeding potential of the different cultivars, at different planting dates and defoliation/cutting treatments, was calculated by using the leave and tuber production (variable criteria) from each treatment. The period from the initial cut to the last regrowth cut was a second variable criterion that was used. The third criterion (non-variable) was the standard norm that the daily intake of a matured livestock unit (MLU) of 450 kg is 10 kg. According to the results the following example of a combination of treatments can be used to maintain ± 10 MLU/ha for the longest period in the winter in Limpopo: Plant 1.1 ha Nooigedacht radish in February, utilize from ± 27 April to 22 June, Plant 2.4 ha Nooigedacht radish in April, utilize from ± 22 June to 27 August, Plant 0.9 ha Mammoth purple top in April, utilize from ± 20 August to 3 Oct According to the results the following example of a combination of treatments can be used to maintain ± 10 MLU/ha for the longest period in the winter in Gauteng: Plant 2.1 ha Forage star turnip in February, utilize from ± 12 April to 13 June, Plant 1.7 ha Mammoth purple top in February, utilize from ± 7 June to 28 July, Plant 1.5 ha Forage star turnip in April, utilize from ± 18 July to 29 August, Plant 2.1 ha Forage star turnip in April, utilize from ± 17 August to 4 Oct.

PhD (Plant Production) / Department of Plant Production / Planting chickpea genotypes at different dates within the same season may expose the crop to different environmental factors (temperature and moisture) during their vegetative and reproduction stages. Thus, knowledge of optimum planting date that minimises extreme temperature and water stress conditions during crital stages of chickpea plant development may increase biomass and grain yield. The objective of the study was to determine the effect of planting date and genotype on aboveground biomass and grain yield of chickpea under climate change scenario in North Eastern Region of South Africa. The hypothesis tested was that planting date and genotype have an effect on biomass and grain yield of chickpea under climate change scenario. Thus, a study design incorporating a combination of field and modelling experiments was set to run in 2014 and 2015 winter planting seasons at the University of Venda, South Africa. Field experiments determined the effect of planting date and genotype on chickpea flower retention and pod abortion, aboveground biomass and grain yield, water use and radiation use efficiency, whilst modelling experiments calibrated and validated the FAO AquaCrop model to simulate chickpea aboveground biomass and grain yield using climate datasets (1950 - 2100), simulated from 15 global circulation models (GCMs) under the representative carbon dioxide concentration pathways (RCP) 4.5 and 8.5. Field experiments results showed significant effect of planting date and genotype on biomass and grain yield of chickpea. Planting early, particularly under well-watered conditions appeared to be the most suitable sowing period for chickpea in this region. In contrast, late planting had lowest biomass and grain yield. The high grain yield in early planting (1.99 t ha-1) was supported by greater yield components (seed weight (13.8 gm-2) and pod weight 23 gm-2), number of pods per plant (75 pods plant-1) and harvest index (43 %)). Moreover, plant phenological factors such as plant height (46 cm) and number of branches per plant (16 branches) were also greater in early planting, with late planting recording lowest values in all the measured parameters. In addition, the greater biomass and grain yield in early planting compared with the normal and late sowings was caused by greater intercepted radiation (91%), improved flower retention (45.2%) and minimised water use (174 mm) and pod abortion (13.6%). Late maturing genotypes (Range 4 & 5) showed greater water use efficiency of grain yield (7.3 & 7.1 kg ha-1 mm-1) and had the highest radiation use efficiency of grain yield, which was on average 7.2% (0.07 g MJ-1) greater than ICCV9901, and 15.6% (0.13 g MJ-1) greater than Range 1 & 3, but this depended on soil moisture availability. vi The simulation results, indicated a significant increase in temperature (by 4.2 to 5.5 oC) over a period from 1950 to 2100. This increase lead to a concomitant increase in chickpea evapotranspiration and accumulated growing degree days. Moreover, optimal planting date for chickpea shifted from mid-month of April during 1950 to end of May in 2100 and reduced growing season length from 140 days in 1950 to 85 days in 2100. Aboveground biomass increased from 2.0 & 2.05 t ha-1 in 1950 to 4.3 & 4.57 t ha-1 in 2100, respectively in RCP 4.5 and 8.5, whilst grain yield increased from 1.07 & 1.08 t ha-1 in 1950 to 1.68 & 2.21 t ha-1 in 2100, respectively under RCP 4.5 and 8.5. Planting dates that were recommended by AquaCrop model recorded the highest increase in aboveground biomass and grain yield compared with early, normal and late planting dates. Late maturing genotypes (Range 4 & 5) showed greater grain yield and biomass, whilst early and medium maturing genotypes had low biomass and grain yield. The study recommend early planting date together with late maturing chickpea genotypes (Range 4 and 5) in the region so as to improve water use efficiency, radiation use efficiency, heat use efficiency and aboveground biomass and grain yield of the crop under the present time and under climate change scenario. The early maturing genotype (Range 1) and medium maturing genotypes (Range 3 and ICCV9901) may only be recommended under normal planting date, although there will not be any significant yield advantages compared with late maturing genotypes. The study also recommend the use of planting dates generated by AquaCrop model so as to improve biomass and grain yield when chickpea is sown under climate change scenario in Southern Africa. The yield improvement using AquaCrop recommended planting dates was partly caused by greater water use efficiency, heat use efficiency and corbon dioxide productivity. Given the potential importance of planting dates in improving current and future productivity of chickpea shown in the study, there is need to work on development of a sowing (planting date) criteria for chickpea in the / NRF

Thesis (M.Sc. (Pasture Science)) -- University of Limpopo, 2014 / Forage sorghum is widely grown in South Africa as annual summer forage to supplement pasture production for sheep, beef and dairy cattle. A number of sorghum cultivars are available commercially, and periodically some cultivars are added while others are withdrawn from the market. The potential yield figures and the nutritive value of these forage sorghum cultivars are generally not known. The management practices that improve forage sorghum production and quality include the time of planting and time of harvesting. The genetic makeup of different forage sorghum cultivars also accounted for a portion of the production and quality. A field experiment was conducted at Dewageningsdrift Experimental Farm (DWD), Moloto, Gauteng and Nooitgedacht Agricultural Development Center (NGD), Ermelo, Mpumalanga to study the influence of planting date on the growth potential of different forage sorghum cultivars. Three planting dates were used: mid-December 2006, mid-January 2007 and mid-February 2007. Thirteen different cultivars were incorporated in the trial to evaluate influence of the breeding history. The cultivars were defoliated at three different stages: cut repeatedly at six weekly intervals (Dt 1), cut repeatedly when it reached a grazing stage (± 800 mm high) (Dt 2) and once at the silage stage (soft dough) (Dt 3). At DWD the average total dry matter (TDM) productions, for the six week cutting treatment (Dt 1), were 10760 kg/ha, 5195 kg/ha and 1944 kg/ha for December, January and February planting date respectively. For the same treatment, at NGT, the average TDM productions were 6396 kg/ha and 1737 kg/ha for December and January respectively. The February planting resulted in the poor germination and seedling emergency. The seedlings did not survive due to low temperatures. The minimum of 13 ºC and 11.8 ºC as well as the maximum of 24.1 ºC and 23.0 ºC in February and March were below the required germination temperature (15 ºC). The highest producers that is available in the market were Jumbo, Sentop, Piper, Kow Kandy, and Sugargraze. Defoliated repeatedly at grazing stage (Dt 2), at DWD, resulted in average TDM productions of 8541 kg/ha, 4950 kg/ha and 2683 kg/ha for December, January and February, respectively. At NGT the average TDM productions were 7769 kg/ha and 3010 kg/ha for December and January respectively. The highest producers were Jumbo, Kow Kandy, Piper, Sentop and Sugargraze. The average TDM productions at the silage stage (Dt 3), at DWD, were 17923 kg/ha, 15015 kg/ha and 2529 kg/ha for December, January and February respectively. At NGT the average TDM production iii was 11856 kg/ha and 5350 kg/ha for December and January, The highest producers were Jumbo, Sugargraze, Kow Kandy, Sentop and Kow Kandy.December planting proved to be the best planting date for optimum DM production, compared to later plantings in January and February. Keywords Forage sorghum, cultivars, planting dates, defoliation stages, grazing stage, silage

Fundação de Amparo a Pesquisa do Estado de São Paulo / The objectives of this dissertation were to determine the cardinal temperatures of sweet potato and compare the simulation of node appearance with the plastochron model (linear) and with Wang and Engel model (nonlinear) and the best way input air temperature in the models and to assess the effect of planting dates on tuber initiation and storage root yield of sweet potato in a subtropical environment. Models calibration and the test were with data of number of nodes on the main stem of sweet potato plants, collected at seven planting dates in 2010, 2011 and 2012 growing seasons. The tuber initiation and storage root yield were assessed in an experiment with four planting dates in 2011 and 2012 growing seasons. The experiments were conducted in the experimental area of the Department of Plant Science, UFSM, Santa Maria, RS, with cultivar Princesa at planting density of de 25.000 plants ha-1. The experiment was a complete randomized block design with four replications. The version with mean temperature was superior to the version with the minimum and maximum temperature as input in both models. The plastochron and Wang and Engel models showed similar performance, with RMSE ranging from 2.1 to 2.2 nodes respectively. Both models can be used to simulate the development of sweet potatoes when it is cultivated in the recommended period. Outside this period is suggested to use the model of Wang and Engel. The conditions of temperature and photoperiod modified the tuber initiation in each planting date, indicating that short photoperiods accelerate its occurrence. The storage root yield was higher when planting was done in late winter due to the longer duration of tuber bulking which coincided with periods of high solar radiation and temperatures favorable to the growth and development of sweet potato. Keywords: Ipomoea batatas. Phenology. Modeling. Planting dates. / Os objetivos desta dissertação foram determinar as temperaturas cardinais da batata-doce e comparar a simulação da emissão de nós com o modelo do plastocrono (linear) e com o modelo de Wang e Engel (não linear) e a melhor forma de entrada da temperatura do ar nos modelos e avaliar o efeito de diferentes datas de plantio no início de tuberização e produtividade de raízes tuberosas de batata-doce em ambiente subtropical. A calibração e o teste dos modelos foram feitos através de dados de número de nós na haste principal de plantas de batata-doce, coletados em sete datas de plantio nos anos 2010, 2011 e 2012. O início de tuberização e a produtividade foram avaliados em um experimento com quatro datas de plantio em 2011 e 2012. Os experimentos foram conduzidos na área experimental do Departamento de Fitotecnia da UFSM, Santa Maria, RS, com a cultivar Princesa na densidade de plantio de 25.000 plantas ha-1. O delineamento experimental foi blocos ao acaso com quatro repetições. Melhor predição dos modelos foi obtida com o uso das temperaturas cardinais 12 °C, 30 °C e 40 °C. A versão da temperatura média diária do ar foi superior a temperatura mínima e máxima diária do ar em ambos os modelos. Os modelos plastocrono e Wang e Engel apresentaram desempenho semelhante, com a RQME variando de 2,1 a 2,2 nós respectivamente. Os dois modelos podem ser utilizados para simular o desenvolvimento vegetativo da batata-doce quando cultivada na época recomendada. Fora desse período sugere-se usar o modelo de Wang e Engel. As condições de temperatura e fotoperíodo modificaram o início de tuberização em cada data de plantio, indicando que fotoperíodos curtos aceleram sua ocorrência. A produtividade de raízes tuberosas foi maior quando o plantio foi realizado no final do inverno, em decorrência da maior duração da fase de acumulação de amido, que coincidiu com os períodos de alta radiação solar incidente e temperaturas favoráveis ao crescimento e desenvolvimento da batata-doce.

Planting date, seeding rate, soil texture, and row configuration are important factors in soybean production. Each of these factors can impact overall production and yield of soybean immensely. Growers can have difficulty making decisions about how to best manage their production systems with these factors in mind. Therefore, research was conducted from 2019 to 2021 at the Delta Research and Extension Center in Stoneville, MS, to evaluate the agronomic performance, yield components, and weed control of soybean planted with different planting dates, row configurations, soil textures and/or seeding rates. Common row configurations utilized in Mississippi soybean production were compared to a triple-row configuration on raised beds. First planting dates occurred from late-April to early-May and second planting dates followed three weeks later. Each row configuration was planted at 320,000 seed ha-1 for agronomic studies. Seeding Rate Study was initiated where triple-row configuration plots were planted at 320,000, 445,000, and 553,000 seed ha-1. Total dry matter (TDM) was determined by removing a m-2 in each plot at soybean growth stage R6.5 and allowing samples to dry down and weigh them. Harvest index was determined by collecting seed from TDM samples and weighing them. Pod node-1, seed number, and node plant-1 were determined by collecting five random plants from each plot and counting the total number of pods, seed, and nodes. Soybean planted on silt loam at the first planting produced lower seed weight, seed number, and harvest index than soybean on clay soil at either planting date. Two row configurations, single- and triple-row, were planted on raised beds for weed control studies. Programs included PRE only, EPOST, LPOST, PRE fb EPOST, PRE fb LPOST, and PRE fb EPOST fb LPOST. Herbicide timings included 7, 14, 21, and 28 DA-crop emergence and each timing was followed by a sequential application 14 d after the initial application. Triple-row configuration had lower plant densities and produced lower yield than single- and twin-row configurations. Triple-row configuration soybean planted on clay soil and at 445,000 and 553,000 seed ha-1 produced greater yield than any other seeding rate or soil texture.

Thesis (M.Sc. (Pasture Science)) --University of Limpopo, 2014 / Due to shortage of adequate pasture in large parts of South Africa, winter survival poses a problem to farmers. A shortage in winter grazing is the major problem on most farms in South Africa. Animals loose weight in winter which leads to low reproduction, production of milk, mutton and meat. The winter feed shortages counteract also the possible good performance of animals during summer. Winter supplementation contributes largely to high input costs in livestock production, which can make this enterprise uneconomically. This study was done at two different localities: Hygrotech’s experimental farm at Dewageningsdrift, Gauteng and Nooitgedacht Agricultural Development center, Mpumalunga. Five winter fodder crop cultivars (Witteberg oats, Overberg oats, LS 35 stooling rye, LS 62 stooling rye and Cloc 1 Triticale) were planted on six planting dates (05 April, 04 May, 06 June, 20 July, 20 August and 26 September). Five cutting treatments were applied on Dewageningsdrift:  First cut 8 weeks after planting and after that re-growth every six weeks (Ct 8),  First cut 10 weeks after planting and after that re-growth every six weeks (Ct 10),  First cut 12 weeks after planting and after that re-growth cut every six weeks (Ct 12),  First cut 14 weeks after planting and after that re-growth cut every six weeks (Ct 14),  First cut when more than 50% of plants were in the reproduction stage (RS). The same cultivars that were used at Dewageningsdrift were used on Nooitgedacht ADC. Only one planting date was applied here that was 02 February 2007. The cutting treatments differed also from that on Dewageningsdrift. Material was cut for the first time when it reached a grazing stage (± 50-60 cm high) and after that re-growth was measured four weeks. The main conclusions from the study were that, Witteberg oats has retained its nutritional value longer than other cultivars. LS 35 stooling rye was an early or short duration growing cultivar, if planted in February to April it will provide grazing early/Mid-winter. However it can also be planted in July to grow in spring. LS 62 stooling rye is a medium to long duration growing cultivar which optimum production period will be in late winter and spring. Witteberg oats is a medium/late producer and a long duration growing cultivar, thus if planted early (April) it can provide grazing until late winter. Overberg oats is an early/med long duration growing type, if planted in April it will produce mid-winter, planted in May to July it will produce late winter and planted in August it will provide spring grazing. Cloc 1 triticale is a long duration growing type. It will produce late winter when planted in April to July and in spring when planted in August/September.

Detta arbeta har utförts för att undersöka hur höstplantering av täckrotsodlad gran (Picea abies) och tall (Pinus sylvestris) överlever och utvecklas jämfört med vårplanterad. Detta i ett led för att se om man kan utöka planteringssäsongen för att få en jämnare arbetsbelastning över säsongen både i plantskolorna och ute i fält. Man har undersökt hur en planteringstidpunkt på sensommaren och hösten påverkar granplantors överlevnad jämfört med plantering på våren. Studien är utförd som en survey studie i södra Sverige på täckrotsplantor av gran som planterats på medelboniteter 2007-2009 och inventerats 2010. Höst och vårplanterade granplantor är jämförda parvis med samma planttyp, ålder, proveniens och geografiskt område. Följande saker har jämförts; plantor per hektar, höjdtillväxt, toppskottstillväxt, rothalsdiametern, frostskador, viltskador samt snytbaggeskador. Höstplantering av täckrotsodlad gran (Picea abies) ger ett lika bra resultat som vårplantering vad gäller överlevnad hos plantor. Höjdtillväxt och diametertillväxt blev något bättre på de höstplanterade plantorna jämfört med vårplanterade efterföljande vår. Höstplanterade plantor skadades något mer av frost än de vårplanterade gjorde, speciellt första säsongen. Vårplanterade plantor fick något mer viltskador än höstplanterade vilket kan bero på färre frostskador. Vårplanterade plantor skadades något mer av snytbagge än de höstplanterade. Snytbaggeskadorna var störst på de torra jordarna i östra området. Höstplantering av täckrotsodlad tall (Pinus sylvestris) gav ett lika bra resultat när det gäller överlevande plantor som gran. / This work has been performed in order to investigate if Norway spruce (Picea abies) and pine (Pinus sylvestris) container-grown seedlings planted in autumn gives the same quality as planting in spring in terms of surviving plants. This is in part to see if one can extend the planting season to get a more even workload over the season, both in nurseries and in the field. The study is designed as a survey study in Southern Sweden on container-grown seedlings of Norway spruce and pine planted 2007-2009 and inventoried 2010. The following things have been compared; plants per hectare, height growth, leading shoot growth, stem diameter, frost damage, damage by wild animals and pine weevil damage. Planting of Norway spruce (Picea abies) container-grown seedlings in autumn gives the same quality as planting in spring in terms of surviving plants. Height growth and diameter growth were slightly better the following season for seedlings planted in autumn compared to seedlings planted in spring. Seedlings planted in autumn were damaged by frost more than seedlings planted the spring, especially the first season. Seedlings planted in spring were slightly more damaged by wild animals than seedlings planted in autumn which may be because of less frost damage. Seedlings planted in spring were slightly a little more damaged by pine weevil than seedlings planted in autumn. Pine weevil damage was greatest in the arid soils in the eastern area. Container-grown seedlings of pine (Pinus sylvestris) planted in autumn gave equally good results as seedlings planted of Norway spruce.

Thesis (M.Sc. (Agricultural Economics)) -- University of Limpopo, 2023 / The agricultural sector plays an important role in South Africa regardless of the small contribution of 1.88% it has to the GDP of the Country. Small-scale maize farmers’ decisions to adopt adaptation options in response to climate change and variability are influenced by socioeconomic, institutional, and environmental factors, indicating that decision patterns can be very specific to a given locality. The study aimed to analyse the determinants of small-scale maize farmers’ willingness to pay for changing planting dates in the face of climate change. This study had two main objectives, to identify and describe the socio-economic characteristics of small-scale maize farmers, and to determine factors influencing the small-scale maize farmer’s willingness to pay for changing planting dates in the face of climate change in Makhuduthamaga Local Municipality. The study used primary data with a sample size of 150 small-scale maize farmers. Descriptive statistics and the Probit Regression Model were employed when analysing data. The study employed purposive sampling in the data collection process and three villages were selected. Probability was proportional to sample size and was used to select the number of small-scale maize farmers for the sample frame of each village. About 58% of the sampled small-scale maize farmers were willing to pay for changing planting dates in the face of climate change, as opposed to 42% of those not willing to pay for changing planting dates. Empirical results from the analysis reported that age (10%), educational level (1%), level of income (1%), years of farming (10%), total output (1%), exposure to climate information services (5%), and use of indigenous forecast (1%) out of twelve explanatory variables were found to be significant. Based on the empirical findings of the study it is recommended that government officials together with other stakeholders such as NGOs and research institutions should invest in the education of small-scale maize farmers through knowledge systems such as (presentations, conferences, seminars, abet etc). Government policies and strategic investment plans that support improved small-scale maize farmers’ accessibility to climate information are also recommended.

MSc (Plant Production) / Department of Plant Production / See the attached abstract below