The results of weed flora indicated that the dominant weed species were related to broadleaf. Several investigators reported that approximately 70% of weed species in sugar beet fields are mainly broadleaf annual such as redroot pigweed (Amaranthus retroflexus) (Weaver and Williams 1980; Schwizer and May 1993 and Heidari et al. 2007; Lobmann 2019).
Weed elimination in sugar beet was achieved by Betasana-Trio and Tigro herbicides as well as Select Super herbicide. These results indicated and confirmed that Betasana-Trio and Tigro herbicides are specified to broadleaved weeds. Similar tendency was recorded for the narrow-leaved weeds where these results indicated and confirmed that Select Super herbicide is specified to narrow-leaved weeds. Mousa et al. (2015) reported that all weed control treatments decrease significant various weeds categories than untreated check and hand hoeing twice was the most superior treatment on reducing the fresh weight of weeds species in both seasons, and gave significant effect on the second one only. Hand hoeing twice gave the highest significant percentage with Rumex dentatus and Chenopodium murale by 83 and 90%, respectively, compared to untreated control. Also, he added that the total broadleaf and total broadleaf and grassy weeds were significantly reduced by 54 and 91%, respectively, compared to untreated check in the second season. Our findings are consistent with those obtained by Attia et al. (2011), Vasel et al. (2012), Wujek et al. (2012) and Deveikte et al. (2015).
Regarding the effect of herbicidal treatments on sugar beet leaf pigmentation, the results indicated that although the mode of action of most of these herbicides is a classical photosynthesis inhibitor, they possessed higher selectivity and did not affect sugar beet leaf chlorophyll content; meanwhile, all of the treatments surpassed the control. Such superiority in chlorophyll content may be due to the lesser competition between sugar beet plants and the associated weeds as indicated in Table 3). The results emphasized that all the herbicidal treatments except Tigro at the lower dose did not affect sugar beet pigmentation of leaves. Chitband et al. (2014) reported that PSII inhibitor herbicide such as chloridazon controlled weeds at higher doses more than other herbicides (except of Portulaca oleracea) by 90 percent reduction in aboveground dry matter yield.
Applying Betanal MaxxPro, hand hoeing twice, Tigro at 1.0 l fed−1 and Betasana-Trio 0.9 l fed−1 produced high values of root yield t fed−1. These treatments significantly increased root yield t fed−1over the unweeded check by 79.4, 68.8, 42.9 and 33.9%, respectively. Such superiority of these treatments in increasing sugar beet yield characters may be due to the lesser coemption of weeds to sugar beet, especially at the early growth stages, which reflected on number and weights of the different species. Similar results were obtained by Soroka and Gadzhiev (2006) who reported that when sugar beet and weeds grow together 30 days after emergence of sugar beet, the root yield decreased by up to 45%. Also, Attia et al. (2011) and Majidi et al. (2011) reported that the use of herbicides may reduce yield losses, as herbicides can reduce the weed infestation. Mehmeti (2004) showed that using a combination of broadleaved herbicides caused weeds to be controlled and root yield to be increased. These results are in accordance with those recorded by Wujek et al. (2012), Mobarak et al. (2012) and Abou-Zied et al. (2017).
The data of the effect of weed control treatments on sugar beet root quality exhibited clear differences in sugar beet quality parameters, which affected sugar extraction process. In general, although the weed treatment with Betanal MaxxPro contained the highest gross sugar %, it could not compensate the relatively lower yield to achieve the highest sugar yield fed−1. It seems that α-amino-N component is related to sugar detracting, where it lowers the Qz % parameter. Sugar beet plants treated with Betanal MaxxPro possessed the maximum purity parameters (high Qz % and low soluble non-sugars (potassium, sodium and α-amino nitrogen content of beet). This resulted in the superiority of gross and extractable sugar yields fed−1. In this respect, Dale et al. (2005) found that white sucrose produced per unit area did not differ among post-herbicide treatments and sugar and non-sugar contents were not affected by the herbicide treatments. It was reported that sugar yield values followed that of root yield because the herbicide did not have any influence on the amount of sugar beet root quality parameters (Dale et al. 2006).
Moreover, Dale et al. (2005) found that white sucrose produced per unit area did not differ among post-herbicide treatments and sugar and non-sugar contents were not affected by the herbicide treatments. Sugar yield values followed that of root yield because the herbicide did not have any influence on the amount of sugar beet root quality parameters (Dale et al. 2006). Mahmoud and Soliman (2012) indicated that sugar yield per feddan in the first season increased in five treatments (crus 2.5 kg fed−1 + handweeding, Betanal MaxxPro + hand hoeing, hand hoeing twice, crus 2.0 kg fed−1 + handweeding and crus 2.5 kg fed−1) as they gave 5.4, 4.98, 4.73, 4.64 and 4.35 t fed−1, respectively, with percentage from unweeded check 251.87, 232.02, 220.56, 216.33 and 202.64%, respectively. The unweeded check gave the least sugar yield per feddan (1.7 t fed−1); also harness and crus 2.0 kg fed−1 gave lower sugar yield than the rest of treatments (2.64 and 2.84 t fed−1, respectively) with percentage from unweeded check 155.15 and 166.79%, respectively.