Upholding Sunflower (Helianthus annuus) Yield and Profitability while Maintaining Soil Fertility Under Intercropping with Sunn Hemp and Mineral Fertilizer Application

Sunflower (Helianthus annuus L.) is one of Tanzania’s high-potential cash crops. Nonetheless, nutrient depletion, especially nitrogen (N), is limiting its productivity. The study was conducted in the semi-arid-Dodoma region in Tanzania where it adopted a randomized complete block design (RCBD) with six treatments each replicated four times. These treatments were T1; Control (sunflower pure stand) without mineral nitrogen (N) fertilizer, T2; Sunflower-Sunn hemp intercrop under 1:1 row ratio without fertilizer, T3; Sunflower-Sunn hemp intercrop under 1:1 row ratio with fertilizer, T4; Sunflower-Sunn hemp intercrop under 2:1 row ratio without fertilizer, T5; Sunflower-Sunn hemp intercrop under 2:1 row ratio with fertilizer and T6; Sunflower pure stand with fertilizer. Data that were collected were sunflower growth, and yield parameters, economic returns (gross income, net income, benefit-cost ratio-BCR), and soil chemical properties. Regardless of the site, T6 and T3 showed the best performance based on the sunflower growth and yield. For instance, at Kongwa the sunflower leaf area was highest in T3 (285 cm²) and T6 (282 cm²) with T4 having the least value of 149 cm². Economically, Kongwa outperformed Bahi. Specifically, based on treatments, T3 had the highest gross income both at Kongwa (US$ 3412 ha^-1) and Bahi (US$ 1756 ha^-1). This translated into respective net income and BCR of US$ 1639 and 698, and 7.50 and 3.20. Except for soil pH, the other chemical soil properties tended to increase significantly (p ≤ 0.05) under all the treatments containing integrated approaches like Sunn hemp and N fertilizer application relative to the sunflower pure stand. This study’s findings will help rural poor farmers achieve their nutritional, social, and economic needs, hence reducing poverty, and increasing food security.