MSc.

Okra [Abelmoschus esculentus (L.) Moench.] is a warm season vegetable
crop cultivated mainly for its immature fruits. Weed control is an expensive
management practice in okra production which can influence productivity of both
crop and soil. Weed management practices can modify the micro environment of
crops, the extent depending on the method adopted, environmental conditions, and
other management practices. The present study was taken up in the Department of
Agronomy, College of Horticulture, Vellanikkara during March to June, 2016 to
assess the effect of weed management practices on microsite variations and their
consequent effect on growth and yield of okra. The treatments comprised of four
different organic mulches (mango leaves, paddy straw, newspaper and coir fibre
mat), mulching with black polythene sheet, hand weeding, application of pre
emergence herbicide and an unweeded control treatment.
Black polythene mulching positively influenced the yield and yield
attributes of okra and resulted in greatest plant height and number of branches.
Mulching with black polythene, hand weeding and herbicide treatment reduced
the number of days to harvest. Higher number of harvests and number of fruits per
plant were obtained with black polythene mulching. This treatment recorded a
fruit yield of 14.58 t ha-1, followed by the treatments paddy straw mulching and
newspaper mulching (11.16 and 11.01 t ha-1).
Crop uptake of nutrients was higher under black polythene mulch and was
lowest in unweeded control. Similarly, except for coir fibre mat mulching, all
other treatments with mulching showed higher uptake of nutrients, and
consequently, these plants showed higher relative chlorophyll content (SPAD
units). Mulching also improved the soil nutrient status as compared to hand
weeded, herbicide treated and weedy check plots. Available N and K were higher
in mulched plots while available P content was more or less similar in all the
plots.

Considerable effect of weed management practices on soil microclimate
was noticed. Black polythene sheet recorded higher soil temperature during the
entire crop period. Soil temperature in the plots with organic mulches was lower
than the plots without mulching. In general, the soil moisture content at different
growth stages of the crop was higher in all the treatments with mulching as
compared to treatments without mulching.
Higher population of soil microflora was observed with mulching as
compared to unmulched plots. Paddy straw improved soil bacterial and fungal
populations both at flowering and harvesting, whereas, actinomycetes were higher
under black polythene mulch. At flowering, total population of P - solubilsers,
nitrogen fixers and antagonists were higher under mulching with paddy straw. At
harvest higher microbial biomass carbon was found in black polythene mulched
plots, followed by paddy straw.
Higher weed control efficiency (more than 90 %) was observed with black
polythene mulching throughout the crop period. Among different organic
mulches, newspaper mulch recorded higher weed control efficiency followed by
paddy straw mulch. Mulching with coir fibre mat failed to reduce weed growth.
Mulching with paddy straw and newspaper recorded lower weed indices than
hand weeding and pre emergence application of pendimethalin.
The highest benefit:cost ratio of 3.02 was recorded for black polythene
mulching. Newspaper mulching and pre emergence spray of pendimethalin were
next with respect to B:C ratio.
Different weed management practices significantly influenced the micro
environment of the crop, and influenced the yield and yield parameters of okra as
well as the soil quality. Use of either organic (newspaper or paddy straw) or
inorganic (polythene) mulches is a better alternative to manual weeding or
herbicidal application for effective weed management and for better B:C ratio in
okra.