| dc.description.abstract | A field experiment was conducted at Jomo Kenyatta University of Agriculture and
Technology between October 2001 and June 2002 to determine light, water and nitrogen
use in maize-pigeonpea intercrop system. The experiment was laid out as a randomized
complete block design (RCBD) replicated four times. Treatments included two pigeon
pea maturity types; two long duration (erect - ICEAP 00053 and semi-erect - ICEAP
00040) and one medium duration (ICEAP 00557) type intercropped with maize
(Katumani) or sole crop. Data on canopy light interception, soil water content changes,
crop dry matter accumulation, plant total nitrogen and soil mineral N at key phenological
stages were determined. Identification of a suitable reference crop to estimate the amount
of N fixed by pigeonpea using the difference method was done in a greenhouse
experiment. The experimental design was complete block design replicated three times.
Maize (Hybrid 511 and Katumani), sorghum (MB30 and IS 25545) and cotton (Hart 89
M and Uka 591146), were evaluated as reference crops. Sorghum and cotton varieties
were also included in the field experiment as reference crops.
Maize and sorghum accumulated more shoot and root dry mass compared to pigeonpea
both in the field and greenhouse experiment, hence they were unsuitable to be reference
crops. Cotton had similar rooting characteristics and phenological development with
pigeonpea. Cotton was a suitable reference crop for the long duration but not the medium
duration pigeonpea in the greenhouse and in the field. Long duration cultivars had the
highest plant N uptake in the field and contributed high amount of N through litter fall
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and biological fixation compared to medium duration because of higher biomass
production. Soil mineral N increased over time during the growing season, possibly due
to N contribution through litter fall. Intercropping maize and pigeonpea showed a better
use of light than in sole crop. There was a temporal separation in light use in the
intercrop system because maize established faster than pigeonpea, hence utilized light
early in the season. Pigeonpea intercepted more light when maize was harvested.
Long duration pigeonpeas extracted more water than medium duration pigeonpea at the
depth of 70-90 em late in the season and maize extracted at 30 -50 ern, possibly
indicating that either the long duration pigeonpea had more roots at that depth or the roots
were efficient in the extraction of the available soil water an example of spatial separation
in water use. Sole maize grain yield in the two seasons were similar (3578 and 3419
kg/ha in season 1 and 2 respectively). Long duration erect pigeonpea had the highest total
dry matter hence high yields than long duration semi-erect and medium duration. The
average pigeonpea grain yield at the end of the season was 4560, 3203 and 2687 kg/ha
for the long duration erect, long duration semi-erect and medium duration respectively.
The land equivalent ratio (LER) was 1;23, 1.29 and 1.33 for the long duration erect, long·
duration semi-erect and medium duration pigeonpea respectively. There was an increase
total biomass, maize grain yield and total N uptake from plots that were previously
intercropped than plots with continuous maize crop, which indicated the residual benefits
of incorporating pigeonpea in the maize cropping systems. This benefit may be through
litterfall decomposition and/or Nrecycling. | en |
