DETERMINATION OF CRITICAL PERIODS FOR WEED COMPETITION BY THREE APPROACHES FOR ESKANDRANY AND RIVERA SQUASH TYPES

Squash as a vegetable crop strongly suffers weed competition through the short life season and is seriously affected by weed infestation. Thus, two types of squash were grown in two field experiments at the Horticulture Research Station, El-Kanater El-Khiria, Kalubia Governorate during 2015 and 2016 successive summer seasons, to evaluate the effects of weed species community associated with squash crop plants.Two types for early and late competition periods to determine the critical period of weed competition with squash crop through the use of biological curve, regression approach and economic analysis of cost. Each experiment included sixteen treatments representing the combination of two types of squash (Eskandrany cultivar and Rivera hybrid) and eight treatments of weed infestation i.e. four treatments. In the first type, weeds were removed at different periods (10, 20 and 30 days after sowing and for whole season) and in the second type, weeds were allowed to grow for different periods (10, 20 and 30 days after sowing until harvest and for the whole season). The main findings of this investigation showed that experimental field was infested by annual weeds for the whole season by 1.43 and 1.03 ton/feddan dry weight of weeds, exhibited yield loss of 57.1 and 56.3% squash per feddan than weed free yield plot, for the whole season in both 2015 and 2016 seasons, respectively. Also, the results showed that with both biological curve or mathematical , model function for treatments to axpect of 90% squash yield using accepted fitted model equations namely, quadratic equation for critical period of weed control for Eskandrany cultivar was 16.05 and 18.6 days for weed-free and being 2.94 and 2.36 days from planting for weed-competition in the first and second seasons from emergence, respectively. But under Rivera hybrid, for the critical period of weed control 16.39 and 12.1 days for weed-free and 3.03 and 4.29 days for weed-competition in the two seasons, respectively. Such results were emphasized by the differences between gross income or total cost. The critical period of weed-free and weed – competition were (16.1 and 12.7 days) for weed free as well as (2.94 and 3.4 days) for weed competition in 2015 and 2016 seasons, respectively. All weed competition treatments exerted significant efficiency in controlling annual weeds. Weed free for the whole season treatment gave the best control for annual weeds and gave the highest values of yield and yield components in two seasons. Eskandrany cultivar gave the highest reduction of dry weight for annual weeds and the highest value of plant dry weight in first and second seasons. While, Rivera hybrid gave the best values of fruit diameter (cm), fruit length (cm), No. of leaves/plant, fresh weight of fruit (g), plant yield (g), no. of fruit/plant, fruit weight (g) and total yield (ton/fed.) in the first and second seasons. Such information should be disseminated to farmers to keep squash yield losses exhibited from weed competition to maintain maximum squash yield per feddan. Economic feasibility showed that weed free for whole season under Rivera hybrid gave the highest values of gross income, net benefit and the percentage of benefit/cost compared to Eskandrany cultivar in both seasons. Correlation between dry weights of weeds was negative and highly significant with squash yield and its attributes at 5% level of significance meaning that weed impressed management is key for squash vegetable yields poduction with high economic feasibility for 20 days after sowing.