abstracts - INCDCSZ Brasov

PAR and cumulative dry matter were plotted for each plot. The slop is the radiation use efficiency
(RUE).
Results and Discussion
Results of this investigation showed that by higher density of weeds, LAI and height of potato
reduced and vertical leaf area distribution, LAD and light interception changed. By increasing weeds
density and its interference, leaf area percentage in the second layer of canopy increased from 45 to 50
percent. Maximum LAI and LAD were obtained in upper layers of canopy. Amaranthus retroflexus
and Chenopodium album reached to their LAD and maximum light interception in 55 to 80 cm of
height in various treatments, while this point in potato was 40 cm. In other words, weed by putting
more leaf are upon the potato canopy and more height and of course more light interception, can
reduce potato yield. Results showed that by increasing weeds interference, light interception of potato
was reduced. So, in 8 plant of lambsquarter per meter of row , potato light interception was reduced
43.3 and 53.5 percent in 2004 and 2005. In third level of redroot pigweed (8 plants per meter of row)
reduction of potato light interception was 56.5 qnd 66.8 percent in 2004 and 2005, respectively. By 2
redroot pigweed per meter of row, RUE of potato increased 2.8 percent in comparison with control. It
means redroot pigweed suppressed potato by shading. In the first and second levels of density of
lambsquarter (2 and 4 plants per meter of row) results were similar. Average of potato RUE was 1.56
and 1.83 g/MJ intercepted PAR (for redroot pigweed treatment) and 1.72 and 1.89 g/MJ intercepted
PAR in 2004 and 2005. On average, redroot pigweed and lambsquarter reduced RUE of potato by 10.5
and 4.6 percent.
Table 1- Change (%) in dry matter, absorbed PAR and RUE of potato in comparison with control in 2004.
Weed Density
Emergence time
Treatments
2 plants/m of row
4 plants/m of row
8 plants/m of row
8 days before potato
4 days before potato
Same time to potato
Dry Matter
Change in comparison with control(%)
Absorbed PAR
RUE
C. album A. retroflexus C. album A. retroflexus C. album A. retroflexus
-18.7 -21.8 -19.2 -22.1 +2.1 +2.8
-24.8 -39.7 -25.2 -25.2 +0.9 -19.4
-37.9 -47.3 -29.1 -24.9 -12.2 -30.3
-36.3 -47.1 -19.8 -29.1 -19.2 -22.6
-30.4 -38.8 -17.3 -22.2 -14.1 -19.2
-22.3 -24.2 -14.9 -16.3 -7.9 -9.7
Table 2- Change (%) in dry matter, absorbed PAR and RUE of potato in comparison with control in 2005.
Change in comparison with control(%)
Treatments
Dry Matter
Absorbed PAR
RUE
C. album A. retroflexus C. album A. retroflexus C. album A. retroflexus
2 plants/m of row -12.9 -19.2 -15.3 -18.5 +2.6 -1.3
Weed Density 4 plants/m of row -19.5 -27.6 -20 -24.9 +0.5 -3.2
8 plants/m of row -26.5 -34.7 -22.7 -27.1 -5.4 -9.9
8 days before potato -26.9 -35.2 -22.5 -27 -5.1 -10.8
Emergence time 4 days before potato -22.8 -25.1 -22.4 -24.9 -1.1 -3.2
Same time to potato -13.9 -18.9 -16 -18.5 +3.2 +0.4
Selected References
Crook, T. M., and Renner, K. A. 1990. Common lambsquarter competition and time of removal in
soybean. Weed Sci. 38, 358-364.
Haverkort, A. J., Uenk, D., Veroude, H., and Van de Waart, M. 1991. Relationships between ground
cover, intercepted solar radiation, leaf area index and infrared reflectance of potato crop. Potato
Res. 34, 113-121.
Hock, S. M., S. Z. Knezevic., and A. R. Martin. 2006. Soybean row spacing and weed emergence time
influence weed competitiveness and competitive indices. Weed Sci. 54, 38-46.
Keating, B. A., and Carberry, P. S. 1993. Resource capture and use in intercropping: Solar radiation.
254