Mixed cropping is an important cropping system in char areas without an optimum seeding combination of chili, brinjal, radish and coriander. To identify this an experiment was conducted in two consecutive years to find suitable seeding ratio and to ensure maximization of yield and economic returns. The experiment was designed in a randomized complete block design with three replications. Four mixed cropping ratios with one sole chili viz. Chili (sole), 100% chili + 70% brinjal + 20% Radish + 10% coriander, 100% chili + 50% brinjal + 30% radish + 20% coriander, 100% chili + 30% brinjal + 40% radish + 30% coriander, 100% chili + 80% brinjal + 70% radish + 50% coriander were evaluated. The highest chili equivalent yield 29.9 t ha^-1 (29.7 t ha^-1 in 2019–20 and 30.1 t ha^-1 in 2020–21), gross return (10512 USD ha^-1) and gross margin (9233 USD ha^-1) was found from 100% chili + 30% brinjal + 40% radish + 30% coriander seeding ratio. On the other hand, the lowest chili equivalent yield 11.8 t ha^-1 (11.7 t ha^-1 in 2019–20 and 11.9 t ha^-1 in 2020–21), gross return (4167 USD ha^-1) and gross margin (2845 USD ha^-1) was found from Chili (sole) treatment. The maximum MBCR (241.7) was also recorded from the same 100% chili mixed cropped with 30% brinjal+ 40% radish + 30% coriander seeding combination. Finally, the combination of 100% chili + 30% brinjal + 40% radish + 30% coriander seeds has found great productivity and profitability in mixed cropping system.

Mixed cropping, chili, brinjal, radish, coriander, productivity and profitability

Mixed cropping, often referred to as polyculture, inter-cropping, or co-cultivation, is the process of planting two or more plants simultaneously in the same area and interdigitating them so that they grow together. But single crop systems have steadily supplanted mixed cropping (Clara et al. 2020). The aims of crop combinations are to obtain cash returns in manageable installments, particularly for irrigated crops; to improve labor distribution throughout the year; to make the best use of the space and nutrients that are available; to protect against weather, disease, and pest risks; to provide for daily needs like pulses, fiber, and oil seeds; and to obtain balanced cattle feed (Kumar et al. 2021).

Char ecosystem is a unique environment that demands unique solutions. The chars are riverine islands that are formed by the deposition of sediment carried by rivers. In Bangladesh’s history, environment, economy, and social life, chars have a special significance (Zaman and Alam 2021). The people living in chars are often marginalized and have limited rights to land and livelihood resources (Zaman and Alam 2021).

A common agricultural practice in Bangladesh is mixed cropping, especially in the char ecosystem. The simultaneous cultivation of two or more crops on the same piece of land has several advantages (Karim et al. 2017; Rahman et al. 2021). It is one of the adaptation measures adopted by char dwellers to cope with hazards such as floods, erosion, droughts, hailstorms, and cold waves. It increases output and ensures the farmer has access to food while reducing the spread of illnesses and pests. Legumes can also increase soil fertility by supplying nitrogen to the soil. This method also improves crop output and reduces soil erosion. The general idea is that growing many crops at once conserves land because they may ripen at different times in the same field and has many positive environmental effects. A dense plant stand results in a higher number of plants per unit area; the foliage and roots cover a larger area, increasing radiation (Keating and Carberry 1993), water (Morris and Garrity 1993a), and nutrient capture (Midmore 1993; Morris and Garrity 1993b); the balance of input and outgo of soil nutrients; the suppression of weeds and insect pests; the resistance of the plant to climate extremes (wet, dry, hot, and cold); the suppression of plant diseases; the increase in overall productivity; and the reduced workload associated with farming operations, which enables equal attention to be given to all crops (Sarker et al. 2022).

For small-scale farming where harvesting is done by hand, mixed cropping works well. The method has been effectively used to increase small farmers’ revenue and food production while reducing the possibility of a complete crop failure since even in the event of a failed crop, other crops in the field may still yield. In comparison to monoculture farming, mixed cropping also uses less nutritional inputs, such as irrigation, fertilizers, pruning, and insect management. As a result, it is frequently more economical.

Because two or more distinct crops are grown concurrently in the same area, mixed cropping lowers the probability of total crop failure. Compared to planting solitary crops, a successful mixed cropping system offers superior resource usage efficiency, varied crop output, and a higher financial return overall production per unit area. Farmers commonly mixed diverse crops like chili, brinjal, radish, and coriander with other leafy vegetables in the char ecosystem. But regrettably, when they sow seeds, they don’t use the proper seed-to-soil ratio. Only they use their own assumptions, and each farmer has a different one. As a result, the farmers reap a variety of benefits from their land. They don’t know what the ratio is for mixed cropping. Therefore, the ultimate objective of the current study is to determine the best-mixed cropping combinations of coriander, radish, chili, and brinjal while also ensuring that the land is used to its full potential for maximum yield and profit.

Growing two or more crops together on the same land is especially true in char areas are known as mixed cropping in farming and has various benefits to practicing non-cereal mixed cropping (chili, brinjal, radish and coriander), that increased total production and profitability through reducing the risk of crop failure, increasing soil fertility, and maximizing land use efficiency (Rahman et al. 2021).

Data from the study revealed that the yield was increased by 191 to 254% and profitability was 126–225% more in mixed cropping system over the sole chili cultivation. The yield increase rate varied over the sole crop due to the number of crops involved in the mixed cropping system. The reason for higher yield in char areas is mainly due to the combination of more non-cereal crops (brinjal, radish and coriander) cultivated together. In a Mungbean and sesame mixed cropping system, yield improved by 1–13% and profitability increased by 12–22%, were reported by Ali et al. (2007). According to Muoneke et al. (2007), Ram and Meena (2014), inter/mixed cropping increases the system yield of component crops overall while reducing the probability of crop failure due to weather conditions.

When compared to a single crop, mixed cropping yields more because it is more resilient to disease and insect damage, maximizes soil nutrient usage, reduces weed pressure, and has a greater ability to hold water due to its larger area coverage (Valentín et al. 2008). Furthermore, pests and diseases may not affect all crops equally. Also, certain crops could ward off pests and illnesses that harm other crops.

Mixed cropping also helps to increase soil fertility by reducing soil erosion and improving soil structure of the char areas (Lalotra et al. 2022). This is because different crops have different root systems that help to hold the soil together and prevent erosion. Because various crops have distinct root systems, soil erosion can be avoided, and soil structure can be improved. Deep-rooted crops have the potential to enhance water infiltration and loosen compacted soil. We found that while radish has a shallow root system whereas chili, brinjal and coriander have deep root systems. In that instance, radish typically absorbs nutrients from the upper soil level, while coriander, chili, and brinjal absorb nutrients from the deeper soil layer and break down the soil layer, which increases the pace at which water infiltrates the soil.

Farmers who practice mixed cropping may have access to a wider variety of crops to sell, so reducing their reliance on a single crop. Studies have revealed that mixed cropping has a number of benefits over sole cropping, including the complementary use of growth factors like soil nutrients, a decrease in the need for costly fertilizers and pesticides, light, water, a decrease in the incidence of pests and diseases, suppress weed pressure, decrease in soil erosion, a higher production of total biomass, more yield stability, sustainable intensification and increased household food security(Ram and Meena 2014; Dharam and Shankar 2016; Weltzien and Christinck 2017; Clara et al. 2020; Lalotra et al. 2022). Additionally, mixed cropping helps to maximize land use efficiency by allowing farmers to grow multiple crops on the same plot of land. An approach for optimizing resource use, mixed cropping regulates natural entities, lowers the chance of crop failure in unfavorable climates, and harnesses the synergistic interactions of biological components. It is important to keep in mind the following when selecting component crops for mixed cropping: crops should have different rooting depths, better leaf orientation, host specificity for pests, peak nutrient and water demands, different rooting behaviors, and less competition from other crops (Seran and Brintha 2010). Many family and root system crops were available for us to choose from during our investigation.

Finally, we can say, because of their extreme vulnerability to natural disasters (such hailstorms, cold waves, droughts, floods, and erosion) char areas have a significant impact on agriculture. Practicing of mixed cropping system helps to reduce these risks in char agriculture due to its ability to diversify farmers’ sources of income and lessen the impact of crop failure.

With a seeding ratio of 100% chili + 30% brinjal + 40% radish + 30% coriander, the greatest chili equivalent yield of 29.9 t ha^-1 (29.7 t ha^-1 in 2019–20 and 30.1 t ha^-1 in 2020–21), gross return (10512 USD ha^–1), and gross margin (9233 USD ha^–1) occurred. On the other hand, the Chili (single) treatment yielded the lowest equivalent yield of chili (11.8 t ha^-1; 11.7 t ha^-1 in 2019–20 and 11.9 t ha^-1 in 2020–21), as well as the lowest gross margin (2845 USD ha^–1). After two years of research, it can be said that 100% chili mixed with 30% brinjal, 40% radish, and 30% coriander yielded the highest crop and system yield and the best economic performance when compared to Chili (sole) cultivation. Make sure the subsidiary crop does not hinder the main crop’s growth or mature before or after the main crop in order to get the most advantage from it blended with it. In conclusion, mixed cropping of coriander, radish, brinjal, and chili is a profitable and productive cropping system in the subtropical climate’s char ecosystem.