Lydia Ndinelao Horn

Bambara groundnut (Vigna subterranea (L.) Verdc), an indigenous legume crop in sub-Saharan Africa, is a crucial source of protein. It is known for its ability to form symbiotic relationships with Rhizobia strains that fixes atmospheric nitrogen through the Biological Nitrogen Fixation (BNF) process. In Namibia, it ranks as the second most important legume after cowpea and is grown in the northern communal regions of the country where it is also consumed. The crop’s nutritional value beats that of many staple foods, providing comprehensive protein in addition to a significant amount of crucial nutrients, such as magnesium and iron, which help fight the major crisis of malnutrition in Africa. Despite its nutritional value, it has been neglected in scientific research and agricultural development programs. The crop faces challenges such as biotic and abiotic stresses, socio-economic constraints, and low yields. Its integration into sustainable food systems is urgently needed, given the challenges of climate change, food insecurity, and nutritional deficiencies. Improving Bambara groundnut requires identifying and selecting genotypes with desirable traits such as early maturity, drought tolerance, larger seed size, and higher yield. Significant genotypic and phenotypic variability exists within landrace populations. This chapter aims to examine sustainable cultivation practices, nutritional optimization, and food processing innovations in Namibia and elsewhere in the world. It emphasizes the need for improved agronomic practices, conservation agriculture, and breeding activities. The review also examines methods to broaden genetic diversity, utilize genomic resources, and employ high-throughput phenotyping to enhance the utilization of genetic resources in pre-breeding programs.

Crop production in small-scale farming communities in semi-arid Central Namibia faces significant challenges due to the high costs associated with irrigation and fertilizers. This study evaluated the impact of different irrigation levels (full and reduced) and six types of soil amendments—biochar, compost, zeolite, NPK, Be-Grow Boost (L) hydrogel, hoof and horn combined with a bone meal (HHB meal), and control on the economic benefits of cabbage production and assessed their feasibility. In the first experiment, irrigation was implemented at 79.6 m³ (100% of the water requirement) for four days a week, classified as full irrigation, and at 39.6 m³ (50% of the water requirement) for two days a week, termed reduced irrigation. Among the fully irrigated treatments, Be-Grow Boost (L) hydrogel, zeolite, and NPK demonstrated the highest Benefit-Cost Ratios (BCRs) at 3.81, 3.67, and 3.65, respectively. In the second experiment, irrigation schedules were adjusted to five and four days per week, using a total of 136.0 m³ (170% of the water requirement) and 124.8 m³ (150% of the water requirement) of water. The compost, HHB meal, and NPK application rates were also modified. The fully irrigated Be-Grow Boost (L) hydrogel, NPK, and reduced irrigation with HHB meal achieved the highest and comparable yields of marketable cabbage heads per hectare, with BCRs of 3.43, 3.24, and 3.29, respectively. In conclusion, utilizing fully irrigated Be-Grow Boost (L) hydrogel, NPK, and reduced irrigation with HHB meal could be effective practices for sustainable crop production in the semi-arid, sandy soil conditions typical of Central Namibia. Moreover, local biochar production could enhance sustainability by reducing overall production costs.

Background: The productivity of Bambara groundnut [Vigna subterranea (L.) Verdc] is gradually decreasing in subsistence farming systems due to various factors, including climate-related issues, socioeconomic limitations and farming practices. This study aimed to identify the reasons for this decrease by examining factors like farming methods, seed color preferences, input quantities and production constraints. Methods: A participatory rural appraisal study was conducted in the Mukwe and Ndiyona constituencies. Four villages per constituency were selected for the study. A structured questionnaire was employed to collect data on demographics, Bambara groundnut farming practices (including farm size, yield, uses and seed preferences), farming inputs and production constraints. Result: The study found that most farmers (77.8%) allocated less than one hectare of land annually for Bambara groundnut cultivation. Around 66.7% of farmers reported low yields, typically between 1 and 100 kg per season. Most farmers (85.7%) grew Bambara groundnuts primarily for household consumption, with only 14.3% focusing on income generation. Cream-seeded Bambara groundnuts were the preferred choice among farmers due to their early maturation, high yield potential and ease of preparation. The main production challenges identified in the region included field pests, low yields, lack of improved varieties, expensive labor and high seed costs. To address these issues, the study recommended breeding for improved varieties and using inoculants to increase crop output. These approaches aim to boost yields and provide nitrogen enrichment for subsequent crops.

In semi‐arid Central Namibia, poor sandy soils limit sustainable crop production. We assessed cabbage performance in two split‐plot field experiments. In Experiment 1, treatments comprised two irrigation levels: full irrigation (watered 3 days a week) and reduced irrigation (watered 2 days a week) as the main plot factor and six soil amendments (biochar; compost; zeolite; nitrogen, phosphorus potassium [NPK]; Be‐Grow boost [L] hydrogel; and hoof and horn + bone [HHB] meal) as subplot factors in three replications. Full irrigation produced a significantly higher yield (21.1 t ha⁻¹), head weight (0.958 kg) and larger head girths (42.1 cm). Biochar produced the highest marketable heads (24,884 heads ha⁻¹), water use efficiency (76.0 kg ha⁻¹ mm⁻¹) and the largest head girths (42.7 cm). In Experiment 2, water was applied 5 and 4 days a week for full and reduced irrigation; the application rates of compost, HHB meal, Be‐Grow boost (L) hydrogel and NPK were modified. The interaction of Be‐Grow boost (L) hydrogel, NPK and biochar with full irrigation and HHB meal with reduced irrigation produced more marketable heads (28,935, 28,009, 27,546 and 28,703 heads ha⁻¹, respectively). Therefore, full irrigation with these amendments could be used for resilient cabbage production in Central Namibia.

In semi-arid regions, climate change has affected crop growing season length and sowing time, potentially causing low yield of the rainfed staple crop pearl millet (Pennisetum glaucum L.) and food insecurity among smallholder farmers. In this study, we used 1994–2023 rainfall data from Namibia’s semi-arid North-Central Region (NCR), receiving November–April summer rainfall, to analyze rainfall patterns and trends and their implications on the growing season to propose climate adaptation options for the region. The results revealed high annual and monthly rainfall variabilities, with nonsignificant negative trends for November–February rainfalls, implying a shortening growing season. Furthermore, we determined the effects of sowing date on grain yields of the early-maturing Okashana-2 and local landrace Kantana pearl millet varieties and the optimal sowing window for the region, using data from a two-year split-plot field experiment conducted at the University of Namibia—Ogongo Campus, NCR, during the rainy season. Cubic polynomial regression models were applied to grain-yield data sets to predict grain production for any sowing date between January and March. Both varieties produced the highest grain yields under January sowings, with Kantana exhibiting a higher yield potential than Okashana-2. Kantana, sown by 14 January, had a yield advantage of up to 36% over Okashana-2, but its yield gradually reduced with delays in sowing. Okashana-2 exhibited higher yield stability across January sowings, surpassing Kantana’s yields by up to 9.4% following the 14 January sowing. We determined the pearl millet optimal sowing window for the NCR to be from 1–7 and 1–21 January for Kantana and Okashana-2, respectively. These results suggest that co-cultivation of early and late pearl millet varieties and growing early-maturing varieties under delayed seasons could stabilize grain production in northern Namibia and enhance farmers’ climate adaptation. Policymakers for semi-arid agricultural regions could utilize this information to adjust local seed systems and extension strategies.

In semi-arid regions, climate change has affected crop growing season length and sowing time, potentially causing low yield of the rainfed staple crop pearl millet (Pennisetum glaucum L.) and food insecurity among smallholder farmers. In this study, we used 1994–2023 rainfall data from Namibia's semi-arid North-Central Region (NCR), receiving November–April summer rainfall, to analyze rainfall patterns and trends and their implications on the growing season to propose climate adaptation options for the region. The results revealed high annual and monthly rainfall variabilities, with nonsignificant negative trends for November–February rainfalls, implying a shortening growing season. Furthermore, we determined the effects of sowing date on grain yields of the early-maturing Okashana-2 and local landrace Kantana pearl millet varieties and the optimal sowing window for the region, using data from a two-year split-plot field experiment conducted at the University of Namibia-Ogongo Campus, NCR, during the rainy season. Cubic polynomial regression models were applied to grain yield data sets to predict grain production for any sowing date between January and March. Both varieties produced the highest grain yields under January sowings, with Kantana exhibiting a higher yield potential than Okashana-2. Kantana, sown by 14 January, had a yield advantage of up to 36.0% over Okashana-2, but its yield gradually reduced with delays in sowing. Okashana-2 exhibited higher yield stability across January sowings, surpassing Kantana’s yields by up to 9.4% following the 14 January sowing. We determined the pearl millet optimal sowing window for the NCR from 1–7 and 1–21 January for Kantana and Okashana-2, respectively. These results suggest that co-cultivation of early and late pearl millet varieties and growing early-maturing varieties under delayed seasons could stabilize grain production in northern Namibia and enhance farmers' climate adaptation. Semi-arid agro-region policymakers could utilize this information to adjust local seed systems and extension strategies.

After peanuts and cowpeas (Vigna unguiculata), the Bambara groundnut (Vigna subterranea (L.) Verdc) is the third most significant food legume in Africa. It is characteristically grown in marginal soils, is drought tolerant, and also has the potential for nitrogen fixation. Despite that, year-on-year Bambara groundnut yields are on a gradual decline due to a combination of abiotic and biotic stresses such as uneven annual rainfall and climate-induced changes in soil microbial community compositions, negatively impacting food security. Thus, the application of rhizobial inoculants at planting significantly improves yields in many leguminous crops. Moreover, symbiotic inoculants are well established in developed countries for improving nitrogen fixation and productivity in grain legumes. Sub-Saharan African countries, however, still under-utilise the above practice. In crop production, nitrogen (N) is the most frequently deficient nutrient since it stimulates root and shoots growth. Whereas nitrogen fertilisers can be used to supplement soil N levels, they are, however, also costly, at times inadequate, may not be timely in supply and may have deleterious environmental consequences. Hence, rhizobial inoculants are seen as a cheaper, easier, and safer method for improving N-fixation and crop productivity in grain legumes, as a result, smallholder farming systems are food secure. Thus, identifying the most efficient rhizobial strains for biofertiliser production for Bambara groundnut is of utmost importance to the farming communities.