Sesame is an important oilseed crop cultivated worldwide. However, research has focused on biochar effects on grain crops and vegetable and there is still a scarcity of information of biochar addition on sesame. This study was to assess the effect of biochar addition on sesame performance, with a specific emphasis on growth, yield, leaf nutrient concentration, seed mineral nutrients, and soil physicochemical properties. A field experiment was conducted on an upland field converted from paddy at Tottori Prefecture, Japan. Rice husk biochar was added to sesame cropping at rates of 0 (F), 20 (F+20B), 50 (F+50B) and 100 (F+100B) t ha⁻¹ and combined with NPK fertilization in a first cropping and a second cropping field in 2017. Biochar addition increased plant height, yield and the total number of seeds per plant more in the first cropping than in the second cropping. The F+50B significantly increased seed yield by 35.0% in the first cropping whereas the F+20B non-significantly increased seed yield by 25.1% in the second cropping. At increasing biochar rates, plant K significantly increased while decreasing Mg whereas N and crude protein, P and Ca were non-significantly higher compared to the control. Soil porosity and bulk density improved with biochar addition while pH, exchangeable K, total N, C/N ratio and CEC significantly increased with biochar, but the effect faded in the second cropping. Conversely exchangeable Mg and its plant tissue concentration decreased due to competitive ion effect of high K from the biochar. Biochar addition is effective for increasing nutrient availability especially K for sesame while improving soil physicochemical properties to increase seed yield, growth and seed mineral quality.

We evaluated the fatty acid compositions in relation to yield and soil nutrients from four fields A, B, C, and D with continuous monocropping histories of 0–3 years, respectively, in Japan from 2015 to 2016. Results showed that, in both evaluation years, seed yield did not significantly differ among the fields although field A produced the highest mean seed yield and 1000-seed weight. Between fields A and C, 1000-seed weight showed significant differences. The contents of seed-saturated fatty acids lauric and myristic decreased in only fields C and D whereas oleic, linoleic, and linolenic acids increased in field D. Only field A produced the highest contents of lauric and myristic acids whereas field D produced the highest contents of linoleic and linolenic acids. The soil total N and exchangeable K contents tended to decrease as exchangeable Mg content significantly increased on the fields with long duration of cropping, fields C and D. Principal component analysis revealed significant positive correlations between soil exchangeable K, and total N contents with 1000-seed weight and lauric acid, as exchangeable Mg content was related with oleic, linoleic, and linolenic acids. Therefore, the high oleic, linoleic, and linolenic acids from field D were mainly attributed to high soil exchangeable Mg content, whereas the high 1000-seed weight, lauric acid and myristic acid were due to the high soil exchangeable K content in field A. Overall, the fatty acid composition quality on the long-duration continuously monocropped fields could show high economic value at the expense of yield under this management practice in continuous monocropping.

Background: Soil fertility decline due to nutrient mining coupled with low inorganic fertilizer usage is a major cause of low crop yields across sub-Saharan Africa. Recently, biochar potential to improve soil fertility has gained significant attention but there are limited studies on the use of biochar as an alternative to inorganic fertilizers. In this study, we determined the effect of maize stover biochar without inorganic fertilizers on soil chemical properties, growth and yield of tomatoes (Solanum lycopersicum L.). A field experiment was conducted in 2022 for two consecutive seasons in Northern Uganda. The experiment included five treatments; inorganic fertilizer (control), biochar applied at rates of 3.5, 6.9, 13.8 and 27.6 t ha⁻¹. Results: In this study, maize stover biochar improved all the soil chemical properties. Compared to the control, pH significantly increased by 27% in the 27.6 t ha⁻¹ while total N increased by 35.6% in the 13.8 t ha⁻¹. Although P was significantly low in the 3.5 t ha⁻¹, 6.9 t ha⁻¹ and 13.8 t ha⁻¹, it increased by 3.9% in the 27.6 t ha⁻¹. Exchangeable K was significantly increased by 42.7% and 56.7% in the 13.8 t ha⁻¹ and 27.6 t ha⁻¹ respectively. Exchangeable Ca and Mg were also higher in the biochar treatment than the control. Results also showed that plant height, shoot weight, and all yield parameters were significantly higher in the inorganic fertilizer treatment than in the 3.5, 6.9, and 13.8 t ha⁻¹ treatments. Interestingly, maize stover biochar at 27. 6 t ha⁻¹ increased fruit yield by 16.1% compared to the control suggesting it could be used as an alternative to inorganic fertilizer. Conclusions: Maize stover biochar applied at 27.6 t ha⁻¹ improved soil chemical properties especially pH, N, P and K promoting growth and yield of tomatoes. Therefore, maize stover biochar could be recommended as an alternative to expensive inorganic fertilizers for tomato production in Northern Uganda.

Sesame (Sesamum indicum L.) is one of the most ancient oilseed crops cultivated for its edible oil and uses in food. Sesame seeds are very nutritious and confer health benefits. However, its potential production in Uganda has not been fully realized. The objective of this review was to summarize the trends in sesame production, export quantity, export value, challenges, and strategies for sustainable sesame seed production in Uganda. The review revealed the sesame seed production and area harvested generally increased from 1996 to 2007 but significantly decreased between 2008 and 2018. The review also revealed that while the export quantities and values were low, they gradually increased from 2009 to 2016. The decreased production between 2008 and 2016 could have been due to challenges such as pests and diseases, loss of soil fertility, prolonged drought, poor agronomic practices, poor yielding varieties, and lack of access to credit. Therefore, it is recommended to improve breeding programs and soil management practices; strengthen agricultural credits and extension services to support marketing of sesame seeds; and improve agronomic practices and farmer knowledge on improved techniques such as sowing methods, plant spacing, intercropping practices, pests and disease control measures. These could boost sesame production in Uganda given the high domestic and global demand for sesame seeds and provide an opportunity to expand sesame production throughout Uganda. Research should focus on how to increase seed yield on farmers’ fields and bridge the yield gap between researchers and farmers while adopting good agronomic practices.