The increasing use of agrochemicals for weed control has raised concerns about their ecotoxicological effects on soil micro-biota communities and soil functions which serve as indicators of soil quality. Thus, this study was conducted to evaluate the effects of continuous field applied herbicides glyphosate, paraquat, atrazine and their combined forms over a period of five years on soil organic carbon, bacterial and fungal population in Akure, Ondo State Nigeria. Soil samples from farmer's field which have been exposed to continuous herbicide application were collected and analysed for physio-chemical properties, organic carbon, total bacterial and fungal population. Simultaneously, soil samples designated as control were collected from adjacent fields with no history of herbicide application and analysed. Results showed a significant (P=0.05) 86% and 128% increase in bacterial population from glyphosate and atrazine treated fields respectively and 42% decrease in paraquat and Glyphosate + paraquat fields when compared with the untreated field. A significant 35% decrease in fungal population was observed in fields applied with atrazine and a further 10% decrease in fungal populations in all herbicide treated fields irrespective of herbicide type and combinations when compared with the untreated field. These changes also correlates with the abundance of beneficial microbes such as Pseudomonas aeruginosa, Pseudomonas fluorescens, Proteus mirabilis, Aspergillus flavius with a probable influence on plant growth promotion and potentials for biodegradation of persistent herbicides. SOC, SOM and pH was significantly (P=0.05) increased in atrazine and atrazine + paraquat treated fields when compared with the untreated fields and other herbicide treatments.

Purpose. Jute mallow (Corchorus olitorius L.) is a mucilaginous vegetable and fiber crop cultivated in the tropics, where catnip (Nepeta cataria L.) and Mexican sunflower (Tithonia diversifolia L.) are common weeds. Hence, the study investigated the growth, yield, and nutrient level of jute mallow in weed-free, catnip, and Mexican sunflower environments. Methods. The study involved two screen-house experiments in a Completely Randomized Design (CRD) with six replications. The treatments were 0 (control), 2, 4, 6, 8, and 10 weed plants per pot in both experiments. These are 0, 100, 200, 300, 400, and 500 weed count per square meter equivalent, based on the surface area of the pots used. Mexican sunflower and catnip plants interacted with jute plants in the first and second experiments, respectively. Growth parameters of jute mallow were recorded weekly from 5 to 8 weeks after sowing (WAS), and harvesting was done at 8 WAS. The proximate composition of jute was evaluated using standard procedures outlined by AOAC. The data collected were subjected to analysis of variance (ANOVA), and means were separated using Duncan Multiple Range Test (DMRT) at P < 0.05. Results. Catnip and Mexican sunflower negatively impacted the morphological features of jute mallow from 100 plants per square meter upwards. Catnip and Mexican sunflower, at 300 and 100–500 plants per square meter, respectively, reduced the dry weight of jute mallow. The crude protein content of jute mallow was also lessened by Mexican sunflower at some point. Conclusions. The study recommends that the density of catnip and Mexican sunflower plants interacting with jute mallow should be maintained below 100 plants per square meter to prevent yield loss.

The cohabitation of weeds with crops may not always pose problems. Weeds are plant pests that negatively impact crop yield. However, it is essential to determine when pest status is reached in crops for weed management decisions in crop production. Field experiments were conducted during the rainy seasons of 2017 and 2018 at the research farm of the Institute of Agricultural Research and Training Ibadan (7o38' N 3o 84' E), located in the rainforest-savanna transition agroecology of southwestern Nigeria. The experiments consisted of nine weed management practices and a weedy check arranged in Randomised Complete Block Design with three replications. Weed density and weight, along with okra's morphological attributes such as the number of leaves, leaf area, plant height and stem girth, were recorded 9 weeks after sowing (WAS). At commercial maturity, unlignified okra pods were harvested from 9-12 WAS. Simple linear correlation and regression analysis between weed parameters and okra traits was performed. The result showed a negative relationship between weed growth and okra yield in both trials. The negative impact of weeds on some morphological traits of okra probably led to the reduction in okra yield. However, plant height and number of nodes did not significantly (P < 0.05) influence okra yield. Weeds attained pest status for okra at a weed density of about 14.17 plants/m2 with weed dry and fresh weights of 10.05 g/m2 and 54.86 g/m2 , respectively. Hence, weed management is necessary for okra production to reduce yield loss.

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