International Policy Research Organisations

Purpose This field study evaluated the interactive effects of biochar (BC) and sewage sludge (SS) on P bioavailability and spinach yields for two seasons.

Method Treatments were combinations of biochar (0, 2.5 and 5 Mg ha-1 ) and sewage sludge (0, 6 and 12 Mg ha-1 ), or mineral fertilizer (200, 28, and 18.9 kg ha-1 ), amended in a randomized complete block design to Luvisol and Cambisol.

Results Significant (p < 0.05) yield increase of 53 and 65%, respectively occurred with increasing sole biochar doses on the Luvisol. Both applied alone and in combination with BC, the high rate of SS increased (p < 0.05) yields on the Luvisol over two seasons. Complimentary effects of 6SS+5BC on the Luvisol showed the highest yield increase for the study period. Co-application of amendments on the Cambisol decreased (p > 0.05) yields compared to sole amendments. Mehlich – 3 extractable P (M3-P) in control plots (CONT) increased between seasons, presumably due to P inputs from the irrigation water. Co-amendments on the Cambisol resulted in higher M3-P increase over mineral fertilizer than on the Luvisol in both seasons. Accumulation of M3-P in control plots confounded correlations between crop yields and available P. Higher P under BC compared to SS amended soils emphasize biochar capacity to capture P from irrigation water.

Conclusion The results suggest that combined low rates of SS and BC can have significant effects on P availability and crop yields. Biochar enhanced plant P uptake, but decrease in yields with simultaneous increase in M3-P between seasons warrants further research.

The article presents results of a survey conducted in the northern part of Botswana. The study was designed to assess the quantity of vegetable produced, production trend and constraints faced by farmers. The survey was done at Ditladi and Gulushabe in the farmer’s fields in May 2019 using a pre-tested survey questionnaire. Farmers were interviewed individually in their farms. Vegetable production and importation data was sourced from Horticultural sector and department of agricultural business promotion. Farmers (41.18%) perceived an upward production trend but data from agricultural offices indicate that production is fluctuating while generally low in all crops except cabbage. Farmers are faced with constraints such as gullies that limit the cultivable area, lack of implements, and lack of transport. The small size of fields is a bottleneck to most farmers. Prevalence of crop pests and diseases results in heavy application of synthetic chemicals. Cropping plan is neglected by more than half of the farmers interviewed. Farmers do not utilize available programs and financiers satisfactorily. They interact with government extension agents mostly on quarterly basis and are aware of climate change at the same time experiencing its consequences. There is a need for a joint effort for on-farm trials and information dissemination by the relevant stakeholders.

A total of 170 bambara groundnut (Vigna subterranea) accessions were evaluated using both simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers generated using genotyping-by-sequencing (GbS), of which 56 accessions were collected from West and East Java. Principal coordinate analysis (PCoA), population structure, and cluster analysis suggest that the East Java accessions could be a result of the introduction of selected West Java accessions. In addition, the current Indonesian accessions were likely introduced from Southern Africa, which would have produced a very marked founding effect such that these accessions present only a fraction of the genetic variability that exists within this species.

Crop resilience and yield stability are complex traits essential for food security. Sorghum bicolor is an important grain crop that shows promise for its natural resilience to drought and potential for marginal land production. We have developed sorghum lines in the Tx430 genetic background suppressed for MSH1 expression as a means of inducing de novo epigenetic variation, and have used these materials to evaluate changes in plant growth vigor. Plant crossing and selection in two distinct environments revealed features of phenotypic plasticity derived from MSH1 manipulation. Introduction of an epigenetic variation to an isogenic sorghum population, in the absence of selection, resulted in 10% yield increase under ideal field conditions and 20% increase under extreme low nitrogen conditions. However, incorporation of early-stage selection amplified these outcomes to 36% yield increase under ideal conditions and 64% increase under marginal field conditions. Interestingly, the best outcomes were derived by selecting mid-range performance early-generation lines rather than highest performing. Data also suggested that phenotypic plasticity derived from the epigenetic variation was nonuniform in its response to environmental variability but served to reduce genotype × environment interaction. The MSH1-derived growth vigor appeared to be associated with enhanced seedling root growth and altered expression of auxin response pathways, and plants showed evidence of cold tolerance, features consistent with observations made previously in Arabidopsis. These data imply that the MSH1 system is conserved across plant species, pointing to the value of parallel model plant studies to help devise effective plant selection strategies for epigenetic breeding in multiple crops.

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.