The impact of inoculation and seed dressing on doubled-up legume technology

Abstract

Rhizobium inoculation and seed dressing are some of the agronomic practices that affect crop productivity in doubled-up legume technology. Doubled-up legume technology is the practice of intercropping two compatible grain legume crops that have different root and shoot growth systems in the same field in order to maximise land and crop productivity. A field study with groundnut and pigeon pea as test crops was conducted at Innovation Africa at the University of Pretoria (IA@UP), South Africa during the 2020/2021 crop growing season to investigate the effect of inoculation and seed dressing with a fungicide and pesticide on doubled-up legume technology. The study involved twelve treatment combinations namely; Untreated sole pigeon pea (PP), Untreated sole groundnut (GN), Untreated PP-GN intercrop, Inoculated sole PP, Inoculated sole GN, Inoculated PP-GN intercrop, Seed dressed sole PP, Seed dressed sole GN, Seed dressed PP GN intercrop, Inoculated + Seed dressed sole PP, Inoculated + seed dressed sole GN, Inoculated + Seed dressed PP-GN intercrop. Each treatment was replicated three times using a randomized complete block design (RCBD). Parameters assessed included soil analysis, germination and survival %, Rhizobium and plant growth parameters, and yield and land equivalent ratios. Grain yield for both groundnut and pigeon pea indicated that treatments had a significant (P < 0.05) effect on grain yield. Furthermore, some sole treatments produced higher grain yield for both groundnut and pigeon pea than their respective intercropped treatments. The sole treatments for both groundnut and pigeon pea receiving both inoculation and seed dressing produced outstanding grain yields (2450.7 kg ha-1 and 2340.0 kg ha-1 respectively), as compared to the other sole crop treatments such as 1550.0 kg ha-1, 1959.0 kg ha-1 and 2264.7 kg ha-1 for groundnut and 931.0 kg ha-1, 1442.0 kg ha-1 and 1254.0 kg ha-1 for pigeon pea. For intercropped treatments, the inoculation and seed dressing treatments outperformed other treatments in terms of survival %, nodule efficiency and grain yield. Based on productivity, except for the untreated intercrop, all other intercropped treatments were more productive than their respective sole treatments. Groundnut–pigeon pea intercropping (doubled-up) with both Rhizobium inoculation and seed dressing was the best treatment since it resulted into higher land equivalent ratio (1.7054) and grain yields for both crops than any of the other intercropped treatments. Key words: groundnut, land equivalent ratio, pigeon pea and rhizobium