Thesis (M.Sc. (Agriculture Agronomy)) -- University of Limpopo, 2020 / Pigeonpea (cajanus cajan [L] Millsp.) is a legume crop which is grown mainly in the Semi-Arid Tropical (SAT) regions and it is mostly cultivated for its edible seeds. It has been identified as a possible substitute crop which can be bought by all people and it can also provide an acceptable amount of nutrition and protein in particular as it is not an expensive source of protein when compared to animal protein. Its ability to tolerate drought and fix atmospheric nitrogen makes it suitable for marginal areas with low rainfall and poor fertility. However, it remains one of the underutilized crops due to limited research on the crop’s diversification and adaptation. Smallholder farmers in the Limpopo Province cultivate landraces pigeonpea varieties that are characterized by late maturity, low grain yield and are sensitive to photoperiod and this makes it difficult for the cultivars to flower early and produce reasonable yield. The objectives of the study were to evaluate the nitrogen fixation, yield and yield components of exotic elite pigeonpea genotypes. The experiment was conducted at the University of Limpopo Experimental farm (Syferkuil) in Mankweng during the 2017/18 growing seasons. The trial was carried out in a Randomized Complete Block Design (RCBD) consisting of three replications. A total of 18 elite pigeonpea breeding lines obtained from ICRISAT in Kenya were planted at an inter-row and intra-row spacing of 1m and 0.5m respectively, in a row of 5m length with an alley way of 2m between the blocks. The standard management practices for pigeonpea were used for weed and insect control. The agronomic data collected included the number of days to first and 50% flowering, the number of days to 90% maturity, canopy width (m), plant height (m), peduncle length (m), number of primary branches, number of pods per plant, pod length (cm), hundred seed weight (g), calcium content, sodium content, magnesium content, phosphorus content, potassium content, iron content, zinc content, proportion of legume N derived from the fixation of atmospheric N2 (%Ndfa), amount of nitrogen fixed and the grain yield (kg.ha-1 ). The generated data was subjected to an analysis of variance using the Statistix 10.0 software. The Least Significance Difference (LSD) was used to separate the means that showed significant differences at an alpha level of 0.05. The results revealed significant differences in nearly all the pigeonpea variables (pod length, number of seed per pod, nutrient elements and the number of primary branches). Across genotypes, the number of days to 50% flowering ranged from 95 to 130 days, while the number of days to 90% maturity ranged from 172 to 220 days, with variety ICEAP 01154-2 being the earliest to flower and mature. Tall plants were observed by variety ICEAP 01541 (2.01m) followed by ICEAP 00902 (1.99m) and ICEAP 00850 (1.90m). Breeding line ICEAP 00673-1 recorded long peduncles with a mean of 0.94m. The number of pods per plant had a range between 56 and 482, while the pod length varied from 2.03 to 8.82cm. Variety ICEAP 00673-1 exhibited the highest number of pods per plant and with longest pods. The 100 seed weight varied from 9.43 to 16.97g among the genotypes. The higher calcium amount was observed in verities ICEAP 00979-1 with an average of 556 mg/L and the highest iron content was observed in ICEAP 01172-2 (14 mg/L). The potassium content ranged between 24 mg/L to 110 mg/L, with the variety ICEAP 00540 having the highest and the variety ICEAP 00850 having the lowest content. The sodium content ranged from 15 to 85.1 mg/L, with the variety ICEAP 01154-2 being the highest and the variety ICEAP 01147-1 having the lowest sodium content. The highest magnesium content was observed in ICEAP 00673-1 (141 mg/L). The phosphorus content ranged from 24.5 to 3.77 mg/L and the highest zinc content was observed in ICEAP 01541 and in ICEAP 00979-1 that had an average of 2.36 and 2.26 mg/L, respectively. The amount of nitrogen fixed from all the varieties ranged from 73.547 to 154.254 kg.ha-1 . The grain yield among the genotypes ranged from 89.24 to 785.29 kg.ha-1 . The top yielding varieties were ICEAP 01159 and ICEAP 00557 with grain yields of 785.29 and 661.51 kg.ha-1 . ICEAP 01159 and ICEAP 00557 are the varieties that produced the highest grain yields and they are recommended for cultivation and breeding purposes. / NRF (National Research Foundation)