Maize was grown in the upland areas surrounding an inland valley
in central Nigeria in a randomized
block experiment using six cultivation techniques (manual cultivation with
a hand hoe (MC);
ploughing in both directions to throw up a ridge (DPL); single ploughing
with the seed placed on the
ridge (SPL); ridging with a wooden, single tine, locally made
‘bush’ plough (BPL); single ploughing
with the seed placed in the furrow (FPL) and ridging with a conventional
ridger (RID) with or
without pre-emergence herbicide (PEH) with two replicates. Initial
cultivation times ranged from 29
to 70 h/ha (BPL<RID<SPL<FPL<DPL<MC). Total weeding
time ranged from 220 to
512 h/ha (MC<DPL<RID<FPL<BPL<SPL) with PEH and from
to 763 h/ha (MC<SPL<DPL<RID<FPL<BPL) without PEH. Ox
cultivation techniques were associated with
higher weeding times and larger weed burdens. Total times for all
field operations were 568–758 h/ha
(MC<FPL<DPL<BPL<SPL<RID) with PEH and 791–870
h/ha (BPL<MC<SPL<DPL<RID<FPL) without PEH. Thus,
although ox cultivation saved time at the most critical time
of year (cultivation and planting), it did not save time overall.
Amongst the ox cultivation techniques, work inputs were
6·3–34·1 MJ/ha (BPL<FPL<SPL<RID<DPL)
and draught forces 387–1377N (BPL<DPL<FPL<SPL<RID).
Yields of maize cobs were 2·55–4·0 t/ha
(SPL<FPL<MC<RID<DPL<BPL) with PEH
and 1·65–3·55 (RID<BPL<FPL<DPL<MC<SPL)
without PEH. Except for SPL, PEH was
associated with increased yield especially when used with ox cultivation.
As regards crop yield, time inputs and work input, there was no
advantage to be gained from using
a separate (and expensive) ridger for maize compared with a locally
made plough or the plough also used for the main cash crop (rice).
At 1992 prices, the cost of PEH was about the same per ha as the
price of labour saved on weeding,
but additional benefits associated with PEH use were the avoidance of
mid-season labour bottlenecks and an overall increase in crop yield.