Long-term maize-pigeonpea intercropping increases productivity and rainfall infiltration in a degraded sandy soil in central Mozambique

Intercropping provides a pathway for the efficient utilization of growth resources that often leads to yield advantages and increased stability compared to sole cropping. In central Mozambique, extensification characterized by slash and burn with non use of fertilizer on degraded sandy soils is the dominant crop production strategy. In these systems, opportunities to improve crop productivity to generate higher organic matter are limited. A greater proportion of farmers are practicing maize (Zea mays L.) -pigeonpea (Cajanus Cajan) intercropping and an intercrop chronosequence can easily be identified. We evaluated two intercropping strategies practiced by farmers in central Mozambique, over two seasons, i.e. alternate row intercrops (48 000 plants/ha) and within-row intercrops (50 000 plants/ha) for both maize/pigeonpea and maize/cowpea. The other objective of this study was to evaluate the effect of duration of maize- pigeonpea intercropping on rainfall infiltration. Simulated rainfall with intensity of 70 mm hr-1 was applied for two hours to selected plots of maize and pigeonpea intercropping chronosequence. The durations of intercropping compared were zero, one, three and five years, zero years duration corresponded to continuous monocropping of maize. The advantage of maize/pigeonpea intercrops is that in successive years a ratoon crop of pigeonpea can be grown reducing investment costs of seed and providing erosion control early in the season when much of the field surface will be uncovered. The within-row intercrops were more productive with land equivalent ratios (LER) of between 1.2 and 1.6, compared with alternate row intercrops with LER values ranging between 1.05 and 1.40 for the two seasons. Although less productive, the alternate row intercrops had a greater potential of providing surface cover between the rows of the main crop. Results of infiltration measurements showed a four-fold increase in steady state infiltration in intercrop duration of five years compared to continuous maize monocropping. The final infiltration rates were 6, 8, 15, and 22 mm hr-1 for zero, one, three and five-year duration respectively. Run-off losses were 94, 88, 68 and 42% for zero, one, three and five-year duration, respectively. It is concluded from this study that steady state infiltration rate improves substantially with duration of maize-pigeonpea intercropping. Intercropping improves moisture conservation in agricultural systems especially where mulching with crop residues is not feasible due to competition for livestock feed. (Résumé d'auteur