Integration of Pigeonpea (Cajanus cajan L.) Cover Cropping into Sorghum Systems for Weed Suppression and Nitrogen Conservation in Central Tanzania

African Journal of Agriculture | Vol. 13, No. 8, August 2026 | pp. 130–137

DOI: 10.46882/2026/AJA/000750

Article Type: Original Research Article

Title: Integration of Pigeonpea (Cajanus cajan L.) Cover Cropping into Sorghum Systems for Weed Suppression and Nitrogen Conservation in Central Tanzania

Names of Authors: Neema S. Mrema¹, Rashid A. Suleiman¹

Authors’ Affiliations: ¹Tanzania Agricultural Research Institute (TARI), Ilonga Centre, Kilosa, Tanzania

Abstract: Smallholder sorghum farmers in semi-arid central Tanzania struggle with aggressive weed infestations and low soil nitrogen levels, both of which severely depress cereal yields. Integrating leguminous cover crops like pigeonpea (Cajanus cajan L.) into sorghum (Sorghum bicolor L.) fields could offer an eco-friendly path to suppress weeds and fix nitrogen. This 3-year field study explored the agronomic benefits of three distinct intercropping patterns: T1 (Sole Sorghum), T2 (Sorghum + Pigeonpea intra-row intercrop), T3 (Sorghum + Pigeonpea 1:1 row arrangement), and T4 (Sorghum + Pigeonpea 2:1 row arrangement). Weed density, weed biomass, soil mineral nitrogen (N), and final crop yields were measured. The 1:1 row layout (T3) achieved the best results, cutting weed biomass by 62.4% at 45 days post-planting compared to the sole sorghum control (p < 0.05). Soil testing showed that the T3 pattern added an average of 42.6 kg N/ha into the soil root zone through biological nitrogen fixation and litter decay. Although intercropping led to a minor reduction in individual sorghum grain yield (3.12 t/ha in T3 vs 3.45 t/ha in T1), it generated an exceptional pigeonpea grain yield of 1.24 t/ha. This elevated the total system Land Equivalent Ratio to 1.38, confirming high land-use efficiency and economic returns.

Keywords: Sorghum bicolor, Cajanus cajan, Intercropping, Weed suppression, Land equivalent ratio, Sustainable farming

Manuscript Timeline: Received: June 04, 2026; Revised: July 10, 2026; Accepted: August 02, 2026; Published: August 31, 2026

Citation: Mrema, N. S., & Suleiman, R. A. (2026). Integration of Pigeonpea (Cajanus cajan L.) Cover Cropping into Sorghum Systems for Weed Suppression and Nitrogen Conservation in Central Tanzania. African Journal of Agriculture, 13(8), 130–137. DOI: 10.46882/2026/AJA/000750

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