Abstract

Wilkson Makumba, Festus K. Akinnifesi and Bert H. Janssen

The concept of competition or complementarity between tree and crop roots for below ground resources have been a major debate in simultaneous systems. Root studies were conducted in three cropping systems, namely: sole maize, pigeon pea/maize intercropping and Gliricidia sepium (Gliricidia)/maize intercropping, with the objective of understanding the potential for competition or otherwise. Pigeon pea and maize root development was monitored at 21, 42 and 63 days after planting (DAP) . Also soil mineral N and Olsen P were assessed along the soil profile up to 200 cm depth. Maize roots developed faster than those of pigeon pea during the first 42 days after planting and there was little overlapping of maize and pigeon pea roots. However, the roots of both pigeon pea and maize had its peaks at 63 DAP, suggesting potential competition during reproductive growth stage of maize. In Gliricidia/maize intercropping, maize had the highest root density averaging 1.02 cm cm-3 in the top 0 -4 0 cm soil layer, whereas gliricidia had lower root length density (0.38 cm cm-3 ) in the top 0 - 40 cm soil layer compared to 0.65 cm cm-3 in the subsoil (40 - 100 cm) . In Gliricidia/maize intercropping, mineral N was increased by 34 - 44 kg ha-1 in the 0 - 100 cm soil layer, whereas Olsen P decreased by 32 kg ha-1 in the entire 0- 200 cm soil profile compared to the sole maize plot. Pigeon pea may be the “loser” in an association that involved both maize and Gliricidia. Because maize had more roots growing within 0 - 40 cm soil layer than Gliricidia it is able to take advantage of the nutrients from the applied Gliricidia prunings in the ridges. The study confirmed root compatibility between Gliricidia and maize and nutrient pumping from deep soil layers.