OWIDO S.F.O., CHEMELIL M.C., NYAWADE F.O., OBADHA W.O.
Abstract
Soil compaction refers to the densification of soils by application
of mechanical energy. Compaction exists where farm operations involve heavy
machinery. Consequences of compaction may be reflected in seedling germination
percentages, growth rates and, ultimately, crop yields. We investigated the
effect of soil compaction on germination rates of bean (Phaseolus vulgaris)
from a Haplic phaeozem (silty clay loam) soil from Egerton University’s
Tatton Farm, Njoro, Kenya. Soil was compacted to respective bulk densities of
1,050, 1,200, 1,400, and 1,600 kg m-3 as treatments replicated four times in
a Completely Randomized Design (CRD). Seedling emergence through compacted soil
was monitored for 6 days, beginning from the 5th day after planting. Four emergence
parameters were evaluated: Ultimate Emergence (UE), Rate of Emergence (RE),
Mean Period of Ultimate Emergence (MPUE), and Modified Rate of Emergence (MRE).
Increasing levels of soil compaction significantly lowered both UE and RE but
not MPUE nor MRE. The variation of RE and UE with soil compaction was best described
by a non-linear function of the form Y=ae-bx. This relationship represented
a decrease in seedling emergence with increased soil compaction. Compaction
to bulk density between 800 and 1,200 kg m-3 was deduced as ideal for seedling
emergence from the studied soil.
Keywords:
soil compaction, dry bulk density, seedling emergence, Haplic
phaeozem