Soil nitrogen dynamics and relationships with maize yields in a gliricidia–maize intercrop in Malawi
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Date
1999-04
Journal Title
Journal ISSN
Volume Title
Publisher
Kluwer Academic Publishers
Abstract
Many soils of southern Africa are severely N deficient, but inorganic fertilizers are unaffordable for most sub-
sistence farmers. Rotations and intercrops of legumes with crops may alleviate N deficiency through biological N 2
fixation and redistribution of subsoil N to the surface. We monitored soil inorganic N dynamics for two seasons in a
gliricidia [Gliricidia sepium (Jacq.) Walp.] – maize (Zea mays L.) intercrop in the unimodal rainfall area of southern
Malawi. One maize crop per year was grown with or without interplanted gliricidia, in factorial combination with
three rates of N (0, 24 or 48 kg N ha −1 ). Application of gliricidia prunings increased (p < 0.001) topsoil (0 to
20 cm) inorganic N at the end of the dry season and during the early rains. Differences between plus and minus
gliricidia treatments were less when total inorganic N to 1-m depth was summed. A greater proportion of the
total inorganic N to 1-m depth occurred in the topsoil (0 to 20 cm) when gliricidia was present, suggesting that
redistribution of subsoil N to the surface accounted for part of the N increase by gliricidia. Gliricidia lowered (p <
0.05) subsoil water content during drier periods. Gliricidia plots accumulated more (p < 0.01) ammonium-N during
the dry season. Nitrate-N remained constant during the dry season but rose rapidly in gliricidia plots after the onset
of rains. A 2-factor model including preseason inorganic N and anaerobic N mineralization potential accounted for
84% of the variability in maize yields for the two seasons’ data combined. The combination of preseason inorganic
N and potential N mineralization appears to provide a good estimate of N supply to maize in systems receiving
both organic and inorganic sources of N.
Description
Keywords
agroforestry, Gliricidia sepium, inorganic nitrogen, maize, nitrogen mineralization