Effect of crop plant density on critical period of weed competition in potato

Field experiments were conducted at the research farm of Bangladesh Agricultural Research Institute, Joydebpur during kharif-1 (March to July) seasons of 2005 and 2006 to identify the critical period of crop-weed competition for Indian spinach. Major weed species were Paspalurn commersoni, Echinochlaa crusgalli. Lie nv/nc india. Cyanotis axillaris and Cyperus rotundus. The lowest weed dry matter was 76.3 g m-2 in 2005 and l01.60 g m-2 in 2006 from the plots weeded up to 40 days after transplanting (DAT). The highest yields were obtained (74.82 t ha in 2005 and 48.48 t ha in 2006) from the weed free plots. The fresh yield of Indian spinach did not vary among no weeding upto 20, 30 and 40 DAT in 2006. But weeded plot upto 30 and 40 DAT produced identical yield in 2005. Maximum BCR (4.52) was obtained from weeded plots upto 30 DAT in 2005 but BCR (2.60) was same from weeded upto 30 and 40 DA F in 2006. On an average, highest BCR (3.55) was recorded from weeding upto 30 DAT. Results revealed that the critical period of crop weed competition lies between 20 and 30 DAT and two times hand weeding would be necessary within 30 DAT for maximum benefit. Key Words: Crop-weed competitions, critical period, weed management and Indian spinach. doi: 10.3329/bjar.v33i4.2306 Bangladesh J. Agril. Res. 33(4) : 623-629, December 2008

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The Concept and Application of Early Economic Period Threshold: The Case of DCPA in Onions (Allium Cepa)

Weed Science ◽

10.1017/s0043174500081753 ◽

1995 ◽

Vol 43 (4) ◽

pp. 634-639 ◽

Cited By ~ 17

Author(s):

Claudio M. Dunan ◽

Philip Westra ◽

Edward E. Schweizer ◽

Donald W. Lybecker ◽

Frank D. Moore

Keyword(s):

Weed Control ◽

Critical Period ◽

Crop Yields ◽

Economic Feasibility ◽

Control Measures ◽

Economic Losses ◽

Weed Competition ◽

Critical Periods ◽

Control Efficacy ◽

The Impact

The question of when to control weeds traditionally has been approached with the calculation of critical periods (CP) based on crop yields. The concept of economic critical period (ECP) and early (EEPT) and late (LEFT) economic period thresholds are presented as a comprehensive approach to answer the same question based on economic losses and costs of control. ECP is defined as the period when the benefit of controlling weeds is greater than its cost. EEPT and LEFT are the limits of the ECP and can be used to determine when first and last weed control measures should be performed. Calculation of EEPT accounts for the economic losses due to weed competition that occur between planting and postemergence weed control. In this way it is possible to better evaluate the economic feasibility of using preplant or preemergence control tactics. The EEPT for DCPA application is analyzed in the context of onion production in Colorado. The EEPT for DCPA application was calculated from an empirical regression model that assessed the impact of weed load and time of weed removal on onion yields. The EEPT was affected by control efficacy, weed-free yield, DCPA cost, and onion price. DCPA application was economically advisable in only one of 20 fields analyzed because of the tow DCPA efficacy (60%).

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Competition periods of crabgrass with rice and soybean crops

Planta Daninha ◽

10.1590/s0100-83582014000100004 ◽

2014 ◽

Vol 32 (1) ◽

pp. 31-38 ◽

Cited By ~ 7

Author(s):

D. Agostinetto ◽

L.C. Fontana ◽

L. Vargas ◽

L.T. Perboni ◽

E. Polidoro ◽

...

Keyword(s):

Environmental Impact ◽

Grain Yield ◽

Weed Control ◽

Critical Period ◽

Rice Cultivar ◽

Weed Competition ◽

Flooded Rice ◽

Reducing Costs ◽

And Control ◽

Impact Of Pesticides

Determining the periods of weed competition with crops helps the producer to choose the most appropriate time to use weed control practices. This strategy allows for the reduction of the number of herbicide applications, reducing costs and the environmental impact of pesticides. The objectives were to determine the period before the interference (PBI) of crabgrass (Digitaria ciliaris) competing with flooded rice, the critical period of interference prevention (CPIP) of crabgrass with soybean and the effects of competition on the grains yield and their components. Experiments were conducted with the coexistence of BRS Querência rice cultivar with crabgrass, for periods of 0, 7, 14, 21, 28, 35, and 110 days after emergency (DAE) and Fundacep 53RR soybean cultivar, whose periods of coexistence and control of crabgrass were 0, 7, 14, 21, 28, 35, and 156 DAE. Rice can grow with crabgrass infestation until 18 DAE, while soybean should remain free from the presence of crabgrass in the period between 23 and 50 DAE. The grain yield and its components, in the crops studied, are affected when grown with crabgrass.

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Maize/Weed Competition Experiments: Implications for Tropical Small-Farm Weed Control Research

Experimental Agriculture ◽

10.1017/s0014479700012801 ◽

1983 ◽

Vol 19 (4) ◽

pp. 341-347 ◽

Cited By ~ 10

Author(s):

R. Vernon ◽

J. M. H. Parker

Keyword(s):

Weed Control ◽

Critical Period ◽

Maize Yield ◽

Weed Competition ◽

Labour Demand ◽

Small Farms ◽

Yield Losses ◽

Small Farm ◽

Control Research ◽

Maize Yields

SUMMARYTwo sets of experiments examined the effects of weeds on maize yields using weeding methods typical of small farms in Zambia where oxen are used for cultivation. Maize yield losses of 30% due to weeds were evident with common weeding practices. A critical period of competition, during which the crop should be kept clean, was demonstrated from 10 to 30 days after emergence. This is a period of peak labour demand and the prospect of using chemical weed control to ease the situation is considered. The value of weed competition data, given its variability between sites, is discussed.

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Effects of Weeding and Row Spacing on Sugar Cane at the Kenya Coast

Experimental Agriculture ◽

10.1017/s0014479700011261 ◽

1981 ◽

Vol 17 (1) ◽

pp. 85-89

Author(s):

A. S. Abubaker ◽

A. M. Gurnah

Keyword(s):

Sugar Cane ◽

Critical Period ◽

Growing Season ◽

Weed Competition ◽

Row Spacing

SUMMARYUsing the sugar cane cultivar Co 421, competition from weeds for the whole growing season was compared at three row spacings with competition for periods ranging from 15–120 days at the start of the season or later, and weed-free conditions all through the season. The critical period for weed competition was the first three months, since weeding during the remaining 11 months did not improve yields, which were similar at row spacings of 1, 1·25 or 1·5 m. There were no interactions between the weeding and spacing treatments.

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