Meera V. Menon’s research while affiliated with Central Water and Power Research Station and other places

Agronomic management exhibits great influence on growth and yield of crops by modifying physical, chemical and biological properties of soil and plants. Field experiment was conducted during June to December, 2018 to assess the effect of agronomic management viz. light intensity, application of manuring and weed management on soil microclimatic variations and its effects on root yield of Sida hemp (Sida alnifolia L.). The treatments included two levels of light intensity (open and 50 per cent shade), two levels of manuring (no manure and FYM@10 t ha-1), and four weed management practices (black polythene mulching, organic mulching with paddy straw @ 5 t ha-1, hand weeding at 1,3,5 MAP (Month after planting) and no weeding). Higher soil temperature at 10 cm depth was observed in open condition and under black polythene mulching throughout the growing period. Higher soil moisture content at 15 cm depth was recorded under shade and black polythene mulching. Black polythene mulching resulted in increase in soil temperature and soil moisture content by almost two percent as compared to bare soil in open condition. The highest root yield of 14.66 t ha-1 was noticed in plots with black polythene mulching with FYM under open condition. Soil temperature and light intensity showed positive correlation with root yield.

A field experiment was conducted from December 2020 to March 2021 in a rice fallow under the Department of Agronomy, College of Agriculture, Vellanikkara to develop a viable weed management strategy in green gram. The lowest weed dry matter production was recorded in hand weeded plots, which was followed by the treatments where pre- mergence application of oxyfluorfen, imazethapyr, imazethapyr + imazamox and diclosulam was integrated with hand weeding. Grain yield and haulm yield was the highest in hand weeding,which was statistically on par with all the treatments where pre-emergence herbicide application was followed by hand weeding. The application of pre-emergence herbicides resulted in a reduction in the soil microbial count at flowering as compared to the untreated plots, however, the microbial population was recovered by harvest stage in the plots treated with oxyfluorfen, imazethapyr and imazethapyr + imazamox. Only diclosulam was found to have a pronounced inhibitory effect on the soil microbial population at harvest stage. Soil nutrient status was found to be higher in any of the weed management treatments as compared to unweeded control.

An experiment was conducted in the laboratory to evaluate the effect of herbicides on beneficial and pathogenic microorganisms. Eighteen treatments included six herbicides at three different doses viz., cyhalofop-butyl (80, 160 and 240 ppm), cyhalofop-butyl + penoxsulam (150, 300 and 450 ppm), bispyribac-sodium (25, 50 and 75 ppm), fenoxaprop-p-ethyl (60, 12 and 180 ppm), carfentrazone-ethyl (20, 40 and 60 ppm) and chlorimuron-ethyl + metsulfuron-methyl (4, 8 and 12 ppm) evaluated on beneficial microbial bioagents ( Trichoderma viride and Pseudomonas fluorescens ) and pathogenic microorganisms ( Rhizoctonia solani , Pyricularia oryzae and Xanthomonas oryzae pv. oryzae ). Results revealed that bispyribac-sodium and cyhalofop-butyl + penoxsulam had greatest inhibitory effect on pathogenic microorganisms Rhizoctonia solani (47.76 and 54.40%) and Pyricularia oryzae (49.07 and 61.12%), but showed no effect on Xanthomonasoryzae pv. oryzae , and were less harmful to biocontrol agents Trichoderma viride and Pseudomonas fluorescens at recommended doses, which were effective in control of broad spectrum of weed flora in rice ecosystem.

A field experiment was conducted to assess the effect of agronomic management on growth, yield and rhizosphere variations of Sida hemp (Sida alnifolia L.) during June 2018 to December 2018. Study comprised two growing conditions viz., open and 50 per cent shade, two levels of manuring viz., no manure and FYM@10 t ha-1 and four weed management practices viz., mulching with black polythene sheet, organic mulching with paddy straw @ 5 t ha-1, hand weeding and no weeding. Taller plants were observed under 50 per cent shaded condition. Open condition showed superiority in case of biomass yield per plant and root shoot ratio at all growth stages of Sidahemp. The highest root yield per plant was recorded in treatment combination, black polythene mulching with FYM under open condition (11.81g). Total population of bacteria, actinomycetes and fungi and soil microbial biomass carbon were significantly higher under open condition. Among manuring, FYM @ 10 t ha-1 recorded higher biometric characters, total population of bacteria, actinomycetes and fungi and soil microbial biomass carbon. Mulching with black polythene recorded higher biometric characters and root yield where as soil microflora and soil microbial biomass carbon were enhanced by organic mulching.