National Agricultural Extension Representatives

The effects of biochar and sewage sludge application on spinach (Spinacia oleracea L.) yield and soil NO3 - content were investigated in typical soils of Botswana (Luvisol, Cambisol) under field conditions. Ten treatments with 3 levels of biochar (0, 2.5, 5 tons ha-1 ) and sewage sludge (0, 6, 12 ton ha-1 ) were applied in 2 subsequent seasons. Significant (p < 0.05) yield increase on the Luvisol occurred if sewage sludge was added at 12 Mg ha-1 with or without biochar. A combination of 6 Mg ha-1 sludge and 5 Mg ha-1 biochar application resulted in the highest crop yield over 2 seasons. On the Cambisol, only marginal yield increase occurred upon high rates of sole organic amendments and chemical fertilizer, while coapplications decreased yields. Decrease in soil NO3 - content caused yield declines in the second season, while P uptake increased significantly (p < 0.05). Correlations between yields, soil NO3 - and leaf N contents were insignificant (p > 0.05). On the Cambisol, a significant regression model for sludge and soil NO3 - was determined. Therefore, one – time combined application of 6 Mg ha-1 sewage sludge and 5 Mg ha-1 on the Luvisol, and 12 Mg ha-1 sewage sludge are recommended for spinach production on the Luvisol and Cambisol, respectively. In subsequent seasons, crop productivity could be maintained by application of mineral N in order to mitigate over-application of P.

Biochar can influence bioavailability of micronutrients and crop yields in sewage sludge-treated soils, but the mechanisms of its effects remain poorly understood. Therefore, this field experiment was conducted on a Luvisol and Cambisol to investigate the bioavailability and uptake of some micronutrients and spinach (Spinacia oleracea L.) yields grown in soil amended with biochar and sewage sludge. Ten treatments arranged in randomized complete block design with three levels of biochar (0, 2.5, 5 t/ha) and sewage sludge (0, 6, 12 t/ha) and combinations thereof were applied. High rate of sole sewage sludge, and its combination with biochar significantly (p < 0.05) increased yield on the Luvisol. On the Cambisol, only marginal yield increase resulted from high rates of sole organic amendments and chemical fertilizer, while co-applications decreased yields. Co-amendments generally increased bioavailability of micronutrients relative to sole amendments in the order Fe > Cu = Zn, with greater increase on the Cambisol, but uptake of micronutrients decreased with co-application rates of amendments. Contents of micronutrients in plant leaves were within the normal range, except for a combination of highest dosage of co-amendments on the Cambisol (Fe; 560 mg/kg), which resulted in leaf necrosis and 7% yield depression. The results showed greater yield response of spinach to co-application of amendments on the Luvisol.

Common bean (Phaseolus vulgaris L.) is a vital source of nutrients worldwide. It is one of the most consumed grain legume in Botswana. Fourteen Andean common bean genotypes were evaluated in four environments (two seasons and two diverse agro-ecologies) to determine the effect of genotype and environment interaction and yield stability. The genotypes were grown in a randomized complete block design with three replications. Grain yield data was analyzed on additive main effects and multiplicative interaction (AMMI), cultivar superiority index, Wricke’s ecovalence and Finlay and Wilkinson regression. There was a lack of variation among the selected genotypes, while environment and genotype × environment interaction (GEI) was significant (P <0.01), which is an opportunity to select stable genotypes across environments. AMMI model for total variation revealed that the environment effect was dominant at 36.83%, genotype × environment interaction at 19.82%, while genotype alone was 3.38%. The cumulative sum of squares of the first two interaction principal component axes (IPCAs) accounted for 76.13% of interaction. Stability coefficients consistently identified genotypes DAB494, CAL96 and DAB541 as the most stable and well adapted, besides the low yield realized. These genotypes are useful for stability breeding purposes and for introduction to the semi-arid environment of Botswana.

Tepary bean is gaining interest around the world as a dryland field crop. A two-year field experiment was conducted to determine the effect of plant spacing on the agronomic performance and fodder quality of the crop. A split-plot design was used with three replications, four cultivars (GK010, GK011, GK012, and Motsumi) were assigned to main plots, while subplots were three intrarow plant spacing (10 cm, 20 cm, and 30 cm). Four agronomic variables and eight chemical compositions, including in vitro dry matter digestibility (IVDMD) of husk, stem, and leaf, were measured. Spacing significantly (P < 0.05) influenced plant biomass, pod yield, harvest index, and seed yield, while cultivar affected only pod yield and seed yield. Plant biomass increased with plant spacing where 10 cm produced 936 kg/ha; 20 cm, 750 kg/ha; and 30 cm, 611 kg/ha for 2015–2016 while 10, 20, and 30 cm were observed for 1568 kg/ha, 1135 kg/ha, and 889 kg/ha, respectively, in 2016–2017 season. &ese trends are attributed to the higher plant population in the narrow row spacing. GK012 consistently outperformed other cultivars for plant biomass, pod yield, and seed yield and has a potential for further selection. Fodder nutritive qualities were not affected by cultivar, while spacing only influenced IVDMD. &e three plant parts were significantly (P < 0.05) different for all the nutritive qualities. Leaves had significantly (P < 0.05) lower values of ADF, CF, and NDF compared to those of stem and husk an indication of relatively higher digestibility of the leaf. Acid detergent fiber (40%), neutral detergent fiber (53.65%), crude fiber (35.45%), ash content (12.29%), dry matter (93.09%), and IVDMD (70.66%) were recorded. &is study revealed that tepary bean forage has good nutritional content, except for the low phosphorus level. For higher agronomic performance, tepary cultivars should be planted at a spacing of 10 cm without compromising forage quality

Common bean (Phaseolus vulgaris) is the most consumed legume crop in the world, and one of the most consumed legume crops in Botswana. This study aims to identify constraints and opportunities in common beans production in order to enhance common bean production in the country. A survey was conducted among 287 farmers in two districts of Southern and Chobe with farmers selected by multi-stage sampling technique. The majority of farmers were female (66.1%), a few farmers planted common bean (11.5%). Slightly more than a quarter (27.8%) of farmers were above the age of 65 years. Constraints to production included pests and diseases, damage by animals, lack of labour, drought, and lack of seeds. Seven percent of farmers assumed that common bean was a drought tolerant crop and 33% of farmers said common bean taste better than other pulses. However, only 21% preferred to grow it. More farmers (13.2%) grew common bean in the Southern district than farmers in the Chobe district (7.0%). Farmers who grew common bean bought their seeds from Agro dealers (76%) with an average amount of 6kg of seed purchased at a time at an average price of $1.11 kg-1 . Common bean was planted on 7% of the arable land that was planted. Most of the farmers (87%) were not trained in common bean production and received little or no assistance from extension officers resulting in little knowledge by farmers about the production of common beans. Strategies to create awareness are needed to facilitate access and mobilise farmers to adopt common beans to improve their livelihoods. This is particularly encouraged in agro-ecological zones such as Chobe with high yield producing potential. Development of seed systems and release of varieties tested in Botswana agro-ecological zones, would increase the production of common bean to improve food security and nutrition, and reduce import bill in Botswana

Common bean is the most consumed legume by humans and hence significant for global food security and nutritive value mainly iron (Fe) and zinc (Zn). The objective of the study was to evaluate the effect of harvesting time and genotypes on proximate and mineral composition of common bean. Two field experiments were carried out in Sebele (24o 33′S, 25o 54′E, 994 m above sea level) horticultural fields during summer 2018/2019. Treatments included two common bean genotypes DAB 564 (white) or 520 (red) and three harvesting stages as the early, mid and late season harvest. In both seasons, genotype and harvesting time significantly (P < 0.05) influenced proximate, macro and micro mineral composition of common bean seeds. Generally genotypes studied had a sufficient amount of proximate and mineral content with crude protein, iron (Fe) and zinc (Zn) content as the most abundant minerals at a range between 20-22%, 33-101 mg g-1 and 41-45 mg g-1, respectively across harvesting times. Genotype DAB 564 (white coloured) significantly (P < 0.05) produced seeds with the highest concentration of proximate and mineral contents especially zinc (45 mg g-1) and iron (70 mg g-1) content irrespective of season. Harvesting common bean seed early or mid-stage produced high seed concentration of proximate, micro and macro mineral content across genotype or season.

Background: Crop yields in the semi-arid regions are low due to climatic and soil related constraints. Soybean as one of the most important legume crops grown worldwide, has a role to contribute nitrogen to improve nutrient poor soils in Africa. A study was conducted to examine the effects of Bradyrhizobium spp inoculations on the growth and yield of soybean varieties in a glasshouse.

Methods: The study was arranged in a randomized complete block factorial design, with factor A being two soybean varieties (Bimha and Status) while factor B was inoculation using four Bradyrhizobium strains and the uninoculated control.

Result: Bradyrhizobium inoculation significantly (P<0.001) affected days to 50% flowering, days to emergence, nodule number, root dry weight and grain yield and yield traits. Parameters that were affected by both inoculant strain and variety included days to 50% flowering, days to emergence, number of pods per plant, pod weight and number of seeds per pod. The interaction effect of variety and Bradyrhizobium inoculant strain was observed only on number of pods per plants. Our study shows that soybean grows well when inoculated with Bradyrhizobium inoculants, in semi-arid conditions of Botswana.

In this video, documents the backstopping visit to Habu Community (Botswana) conducted by CCARDESA in early December 2022

This catalogue is a compilation of 18 APPSA R&D subprojects from 2020 to 2022

Deciphering the constraints in SADC’s agricultural cross[1]border trade: Policy