Evaluation of Yield and Resource Use Efficiency in Triple Intercropping of Cucumber (Cucumis sativus), Green Bean (Phaseolus vulgaris) and Tomato (Solanum lycopersicum)

Tomato and cucumber are now produced by using a high amount of chemical nitrogen fertilizer and a variety of biocides. These are hazardous to human health and the surrounding environment. Intercropping these plants with a legume such as green bean not only improves nitrogen use but also helps to enhance environmental conditions. Based on these assumptions, the present investigation was carried out to determine the effect of intercropping bean with tomato and cucumber on yield and yield components, land equivalent ratio, and nutrient use efficiency in a triple intercropping system.

This experiment was conducted between 2015 and 2016 on a private farm adjacent to Shirvan in the Northern part of Khorasan Province. The experimental layout was based on a randomized complete block design with six treatments and three replications. Treatments were a different combination of single, double, and triple rows of cucumber, tomato, and green bean together with the pure culture of each one. Criteria measured were dry matter, yield accumulation, fruit weight, economical and biological yield, harvest index, land equivalent ratio, and also nitrogen, phosphorus, and potassium use efficiency.

As expected, dry matter yield accumulation in sole cucumber was higher than in other combinations, and a decreasing trend was observed when the ratio of cucumber was increased in intercropped. However, this was the reverse for tomato. Dry matter yield accumulation for green bean was higher in a single row intercropping than in others. Higher dry matter accumulation in intercropped seems to be associated with better resource use and lower interspecific competition and hence photosynthesis improvement. For cucumber, economic and biological yield in the pure stand was higher than the intercropped, while the harvest index was the highest in double rows intercropped. The economic and biological yield of green bean and tomato in pure culture was higher than in other treatments. In contrast, 1-row intercropping increased the green bean fruit in a plant by 18.42% and the tomato fruit weight in a plant by 62.38% compared to pure stand. Better light interception and efficient resource use seem to be the reason for better performance of intercropped compared with monoculture. However, nutrients use efficiency did not show a similar trend when nitrogen, phosphorus, and potassium use efficiency in single row planting was higher for bean and tomato; this was not a common trend in general. Single row intercropped showed a 27% increase in yield on the base of land equivalent ratio.