Abstract
The effect of agrochemicals on the growth and yield of Boro rice in haor ecosystem
was conducted at Purbo Tethulia village, Mohanganj Upazila in Netrakona District
of Bangladesh. Five studies were conducted of which first one was conducted to
survey on agrochemicals used by the farmers and second to fifth experiments were
conducted to estimate the effect of different agrochemicals such as fertilizers,
dolomite, insecticides and herbicides on growth and yield of Boro rice cvs. BRRI
dhan28 and BRRI dhan29 in haor ecosystem during the Boro seasons of 2011-12 and
2012-13. The various agrochemicals viz., NPK, dolomite, insecticides (Diazinon,
Quinalphos and Carbofuran) and herbicides (Pretilachlor, Triasalfuran and
Pyrazosalfuran-ethyl) with five doses of each comprising control, 50, 100, 150 and
200% of the recommended dose (RD) were used for the experiments two to five
while hand weeding was done as a comparison treatment with experiment five. In
experiment one, ninety four farmers were selected under study for collecting data
through personal interview. The findings revealed that majority (63%) of the
farmers had medium use of agrochemicals while 23% had low and 14% had high
use of agrochemicals. Plant height, tiller numbers hill-1, total number of spikelets
panicle-¹, grains panicle-1, 1000-grain weight, grain yield, straw yield and biological
yield) were the highest with recommended doses of the agrochemicals used in both
the varieties in 2011-12 and 2012-13. In view point of pollution by agrochemicals
on agroecosystem of haor, pollution index increased with the increasing levels of
agrochemicals (NPK fertilizer, dolomite, insecticide and herbicide) applied over
recommended dose while 200% of RD of each of NPK and 200% RD of each of
dolomite on both the varieties and 200% RD of Pyrazosalfuran-ethyl on BRRI
dhan28 exibited higher pollution (HP) index. The variety BRRI dhan29 was more
productive with best adaptability in the studied area while 100% recommended
dose of each of NPK, dolomite, insecticides especially Diazinon and herbicides
especially Pretilachlor can be used effectively for plant nutrition, crop protection
with minimum pollution of the ecosystems achieving high production. In order to
save production resources, maintain high productivity and at the same time protect
the haor ecosystem from pollution recommended dose of agrochemicals should be
used without any hesitation under the present context.