الفهرس 
ACKNOWLEDGEMENT
Effect of weed control treatments on weedsOnly 14 pages are availabe for public view
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Abstract
Two filed experiments were conducted at Mallawi Agricultural Research Station, Agricultural Research Center, El-Minia Governorate (Middle Egypt) during 2009/10 and 2010/11 seasons. The aims of this study were to:
1- Determine the critical period of weed infestation to sugar beet.
2- Determine the effect of some weed control treatments on yield, yield components, quality of sugar beet and its associated weeds.
Part I: Determine the critical period of weed infestation to sugar beet:
The first experiment:
The experiment included fourteen treatments which were:
1. Weed free for whole season.
2. Weed free for 2 weeks after sugar beet emergence.
3. Weed free for 4 weeks after sugar beet emergence.
4. Weed free for 6 weeks after sugar beet emergence.
5. Weed free for 8 weeks after sugar beet emergence.
6. Weed free for 10 weeks after sugar beet emergence.
7. Weed free for 12 weeks after sugar beet emergence.
8. Weed infestation for 2 weeks after sugar beet emergence.
9. Weed infestation for 4 weeks after sugar beet emergence.
10. Weed infestation for 6 weeks after sugar beet emergence.
11. Weed infestation for 8 weeks after sugar beet emergence.
12. Weed infestation for 10 weeks after sugar beet emergence.
13. Weed infestation for 12 weeks after sugar beet emergence.
14. Weed infestation for whole season.
The treatments were distributed in a randomized complete block design with four replications. The plot area was 10.5 m2. The normal cultural practices for sugar beet in the experiments were followed.
The results can be summarized as follows:
1- Dry weight of annual grassy, annual broad-leaved weeds and total annual weeds (g/m2) at the end of growing season reduced significantly by increased weed free periods treatments, but, the pervious traits not significantly decreased by increasing weed infestation periods treatments.
2- Root length significantly affected by weed removal treatments in both seasons, the highest root length values obtained from weed free for 8 weeks after emergence and weed free for 10 weeks after emergence as compared to weed infestation for whole season.
3- Weed infestation for 2 weeks after emergence and weed free for whole season gave the highest root diameter (cm) followed by weed infestation for 4 weeks after emergence, weed free for 12 weeks after emergence, weed free for 8 weeks after emergence and weed free for 10 weeks after emergence, on the other hand, the lowest root diameter were obtained from weed infestation for whole season in both seasons.
4- Results indicated that the number of leaves/plant significantly increased by all weed removal treatments. The highest number of leaves/plant were resulted from weed infestation for 4 weeks after emergence, weed infestation for 2 weeks after emergence, weed free for 10 weeks after emergence, weed free for whole season and weed free for 12 weeks after emergence treatments, in 2009/10 season. While, the highest values in 2010/11 season resulted from weed free for whole season, followed weed free for 10 weeks after emergence, weed free for 6 weeks after emergence, weed free for 12 weeks after emergence and weed free for 4 weeks after emergence treatments, respectively.
5- Weed infestation for 2 weeks after sugar beet emergence gave the highest leaves weight (g/plant) in the first season, whereas, in the second season the highest values obtained from weed free for whole season, the lowest values were obtained from weed infestation for whole seasons.
6- Results showed that weed removal treatments significantly increased the root weight of sugar beet plants in both seasons. The highest root weight was obtained from weed free for whole seasons followed by weed infestation for 2 weeks after emergence, weed infestation for 4 weeks after emergence, weed free for 12 weeks after emergence and weed free for 10 weeks after emergence, while, the lowest value was obtained from weed infestation for whole season followed by weed free for 2 weeks in both seasons.
7- Results showed that weed removal treatments significantly increased top yield (ton/fed) in the first and second seasons. The highest top yield (ton/fed) was resulted from weed free for whole season, but, the lowest value was obtained from weed infestation for whole season in 2009/10 and 2010/11 seasons.
8- Results indicated that root yield (ton/fed) significantly affected by weed removal periods in both seasons. Weed free for whole season gave the highest root yield (ton/fed) followed by weed infestation for 2 weeks after emergence, weed infestation for 4 weeks after emergence, weed free for 12 weeks after emergence and weed free for 10 weeks after emergence, but, the lowest value was obtained from weed infestation for whole season in both seasons.
9- Results showed that in spite of non-significant difference between weed removal treatments on total soluble solids (T.S.S %) in the first season, this trait was significantly affected in the second season. All weed removal treatments increased T.S.S%.
10- Data showed that weed removal treatments caused significantly increased the sucrose % in the second season only.
11- Data indicated that purity % of sugar beet increased without any significant difference between different weed removal and weed infestation treatments in both seasons.
12- Results illustrated that sugar yield significantly affected by weed removal treatments. The highest sugar yield (ton/fed) was resulted from weed free for whole season, but, the lowest value was obtained from weed infestation for whole season in 2009/10 and 2010/11 seasons.
13- The relationship between dry weight of total annual weeds at the end of growing season and root yield of sugar beet (ton/fed) was significant and negative in weed free and weed infestation treatments and prediction equation with R-sq value 73.1% & 82.3% and 10.2% & 48.3% in 2009/10 &2010/11 seasons, respectively.
14 -Determination the critical period for weed/sugar beet competition:-
a– Biological approach: -
The critical period of weed-sugar beet competition was between 2–10 weeks after emergence, when the period which sugar beet can tolerate weeds only for 2 weeks after sugar beet emergence and need prolonged period to be free from weeds arrives 10 weeks.
b – Regression approach (mathematical models): -
Application equation reported that to maintain 95% of sugar beet root yield (ton/fed) weeds should be not allowed to exceed 1-2 week after sugar beet emergence and the late duration of weed free period should be not allowed weed to exceed 13-14 weeks after sugar beet emergence.
c – Economic approach: -
Economic critical period of weed-sugar beet competition was found between 4–10 weeks after sugar beet emergence.
Part II: Effect of some weed control treatments on yield, yield components, quality of sugar beet and its associated weeds.
The dominant weed species in field experiments in both seasons were Avena spp., Phalaris spp. as annual grassy weeds, Brassica nigra L., Chenopodium sp., Sonchus oleraceus L., Medicago polymorpha L., Melilotus indica L., Anagallus arvensis, Ammi majus L., Euphorbia helioscopia and Rumex dentatus L. as annual broad-leaved weeds.
Fourteen weed control treatments were used as follows:
1. Safari 50 % WG (triflusulfuron methyl) at the rate of 12 g/fad. applied at 21 days after planting (DAP) followed by Select Super (clethodium) 12.5 % EC at rate of 300 cm3/fed. applied at 24 DAP.
2. Tegro 27.4% EC (phenmedipham + desmedipham + ethofumesate) at the rate at the rate of 1L/fed applied at 21 DAP followed by Select Super 12.5 % EC at rate of 300 cm3/fed. applied at 24 DAP.
3. Beet Up 16% EC (phenmedipham) at the rate of 1L/fed applied at 21 DAP followed by Select Super 12.5 % EC at rate of 300 cm3/fed. applied at 24 DAP.
4. Goltix 70% SC (metamitron) at the rate of 2L /fad. applied as pre-planting.
5. Goltix 70% SC at the rate of 2L /fad. pre-planting followed by Beet Up 16% EC at the rate of 1L/fed applied at 21 DAP.
6. Goltix 70% SC at the rate of 2L /fad. pre-planting followed by Safari 50 % WG at the rate of 12 g/fad. applied at 21 DAP.
7. Goltix 70% SC at the rate of 2L /fad. pre-planting followed by Tegro 27.4% EC at the rate at the rate of 1L/fed applied at 21 DAP.
8. Harness 84 % EC (actocholor) at the rate of 750 cm3/fed. pre-planting.
9. Harness 84 % EC at the rate of 750 cm3/fed. pre-planting followed by Beet Up 16% EC at the rate of 1L/fed applied at 21 DAP.
10. Harness 84 % EC at the rate of 750 cm3/fed. pre-planting followed by Safari 50 % WG at the rate of 12 g/fad. applied at 21 DAP.
11. Harness 84 % EC at the rate of 750 cm3/fed. pre-planting followed by Tegro 27.4% EC at the rate of 1L/fed applied at 21 DAP.
12. Hand hoeing twice (at 20 and 40 days after planting).
13. Hand hoeing thrice (at 20, 40 and 60 days after planting).
14. Un-weeded (control).
The results can be summarized as follows:
1. Results reported that all weed control treatments significantly reduced dry weight of grassy weeds (g/m2) in both seasons at 75 and 105 DAP( ). Hand hoeing thrice or twice recorded the lowest value of dry weight of grassy weeds in both seasons and different surveys time (75 and 105 DAP). followed by Tegro followed by Select Super, Beet Up followed by Select Super, Safari followed by Select Super, Harness followed by Safari, Harness followed by Beet Up, Harness followed by Tegro and Harness, but, the highest value of dry weight of grassy weeds were obtained from unweeded plots.
2. Obtained results revealed that weed control treatments had a significant effect on dry weight of broad-leaved weeds (g/m2) at 75 and 105 DAP in both seasons. The highest broad-leaved weeds control percentage at 75 DAPS and 105 DAP, resulted from hand hoeing thrice and hand hoeing twice compared with unweeded in both seasons.
3. Results clearly indicated that weed control treatments significantly affected the dry weight of total annual weeds (g/m2) at 75 and 105 DAP in both seasons. Hand hoeing thrice and hand hoeing twice recorded the lowest values of dry weight of total annual weeds at different surveys time (75 and 105 DAP) in both seasons follow by Harness followed by Safari, Safari followed by Select Super, Tegro followed by Select Super, Harness followed by Tegro, Goltix followed by Safari, Harness followed by Beet Up, Goltix followed by Tegro, Beet Up followed by Select Super, Harness, Goltix followed by Beet Up and Goltix but, the highest value in dry weight of total annual weeds were resulted from unweeded plots.
4. Chemical and mechanical weed control treatments significantly affected root length (cm) in both seasons as compared to unweeded. Hand hoeing thrice, Harness followed by Safari, Hand hoeing twice, Safari followed by Select Super, Harness followed by Tegro, Tegro followed by Select Super, Goltix followed by Safari, Goltix followed by Tegro and Goltix followed by Beet Up gave the highest values of this trait with out any significance between these treatments in both seasons
5. Data revealed that root diameter was significantly affected by weed control treatments in both seasons. The application of hand hoeing thrice and hand hoeing twice gave the highest values of this trait as compared to unweeded treatments.
6. Data indicated that number of leaves/plant significantly influenced by all weed control treatments. Applying hand hoeing twice, Hand hoing thrice, Goltix followed by Tegro, Tegro followed by Select super, Safari followed by Select super and Harness followed by Safari produced the highest number of leaves/plant in first season. Whereas, in the second season, hand hoeing thrice, Safari followed by Select super and hand hoeing twice gave the highest values of this trait. The lowest values of number of leaves/plant resulted from untreated plots in the first season. In the second season the lowest values obtained from Goltix and untreated plots.
7. Leaves fresh weight (g/plant) significantly affected by weed control treatments in both seasons. All weed control treatments increased leaves fresh weight (g/plant) as compared to untreated plots in both seasons.
8. Root weight (g/plant) reacted significantly to the weed control treatments in both seasons. All studied weed control treatments were superior over the unweeded control. Applying hand hoeing thrice and hand hoeing twice produced the highest root weight without any significant difference between these treatments in both seasons.
9. Results showed a significant differences between weed control treatments in both seasons on their effect on top yield (ton/fed.), Applying hand weeding thrice, hand weeding twice, Harness followed by Safari, Safari followed by Select Super and Tegro followed by Select super gave the best results of top yield (ton/fed.) in the first season. In the second season, the highest top yield resulted from hand hoeing thrice and hand hoeing twice, respectively.
10. Data clearly showed weed control treatments significantly increased root yield (ton/fed.) in both growing seasons. Plots received hand hoeing thrice and twice gave the highest root yield in both seasons as compared to unweeded plots. Data also revealed that spraying with Harness followed by Safari and spraying with Safari followed by Select super resulted in higher root yield than the other chemical weed control treatment.
11. Results revealed that the sugar yield (ton/fed.) increased significantly by weed control treatments in both seasons as compared with unweeded check.
12. Data indicated that there wasn’t any significant difference between all weeds control treatments and the unweeded plots on total soluble solids (T.S.S %) in both seasons.
13. Results indicated clearly that sucrose % was increased significantly with weed control treatments compared with unweeded in the second season only.
14. Data revealed that purity % significantly affected by weed control treatments in both growing season. In the first season the highest value of purity percentage obtained from Safari followed by Select super, whereas, unweeded treatment gave the lowest value of this trait. In the second season Harness followed by Tegro gave the highest value of purity percentage. Meanwhile, unweeded plots gave the lowest value of this trait.
15. The relationship between dry weight of grassy, broad-leaved weeds and total annual weeds at 75 days after planting at 105 days after planting and root yield (ton/fed) was significant negative.
16. Data showed that all studied active ingredients were under acceptable daily intake (ADI).