The experiment was conducted at the experimental farm of faculty of agriculture, New Valley branch, Assiut University that located along 10 km off New Valley government road to Assiut (25°31’26” N, 30°36’33” E, altitude 283 m). Soil at the site are virgin sand, characterized by high salts ranged from 3 : 40 dS/m that suitable for widespread growing of common reed (Phragmites australis) and was found in large areas.
Herbicides and Adjuvants
Glyphosate (Rowand up 48% WSC, Monsanto®) and fluazifop-P-butyl (Fusilade Max 12.5 % EC, Syngenta®) herbicides. Nitric acid 62%, sulfonic acid 83% and urea 46% additives were purchased from reputed chemical suppliers in Egypt. Treatments consisted of glyphosate and fluazifop-P-butyl with adjuvants are given in Table 1. Urea nitrate and urea sulfonyl were produced by mixing of urea with nitric acid and sulfonic acid respectively.
The trials were conducted from September 2016 to December 2017. The first approach consisted of foliar applications of glyphosate and fluazifop-P-butyl herbicides with adjuvants without cutting off stems during seed filling stage. Plots, 3 x 2 m were arranged end-to-end a randomized complete block design (RCBD) with three replications. The second approach, combined cutting of stems and foliar applications. Plots, 3 x 2 m were arranged end-to-end a split-block design with three replications. Herbicides applications were the main factor and cutting levels the subplot factor. Phragmites were cut in autumn during flowering stage. The stems were cut with a machete at two levels 10 and 30 cm then the cut material was removed by hand. Foliar herbicide was applied 4-5 weeks after cutting when re-sprouted shoots were approximately 1 m height. Autumn treatments of herbicides were applied on 27 November 2016.The air temperature was 25±2 °C in autumn and air humidity 40%. The herbicide was sprayed by backpack sprayer at 600 L/ha. Six different treatments were applied individual in appropriate weather conditions (low wind and no precipitation). Control treatments were applied with water only.
Efficacy of herbicides
Responses of the reeds to each treatment were evaluated after one month (on 27th December 2016) and one year (on 27th November 2017) of treatment. Responses were determined using many parameters that were relative importance value (RIV), percentage of dense reduction and chlorophyll content.
RIV were determined to assess the efficacy of herbicide treatments by the following equations according to Mozdzer et al. (2008).
RIV = (d/D × 100) + (h/H × 100) + (c/C × 100)
Where (d = the stem density within an individual quadrat, D = maximum stem density of all quadrats, h = mean height within an individual quadrat, H = maximum height among all quadrats, c = percent cover reeds within an individual quadrat, and C = maximum percent cover reeds among all quadrats).
Density was measured using 0.5 m × 0.5 m quadrat fixed places in each plot and the shoots falling within the frames of the quadrat were counted, by the number of living stems in 1 m2 present in quadrats randomly placed within the common reed clumps (Ramalingam et al. 2013). Percentage cover was rated visually by two independent observers based on a scale of 0-100 (0= no living weeds present and 100= no reduction in weed biomass) (Monteiro et al. 1999).
Reduction of common reed density was determined using the following formula of Mulla et al. (1971).
% Reduction = 100 – C1/T1 × T2/C2 × 100
Where C1 ; C2 are the means of stems numbers/m2 in pre-treatment and post-treatment in control area respectively. T1 ; T2 are the means of stems numbers/m2 in pre-treatment and post-treatment in treatment areas respectively.
Chlorophyll a, b content was determined according to method described by Krishnan et al. (1996). Leaf samples (100 mg) were placed in a graduated tube containing 25 ml of 80% acetone and the chlorophyll was extracted without grinding and centrifugation, by incubating the leaf tissues into the solvent in a dark place at incubation temperatures of 4±2ºC. The contents of the tubes were shaken occasionally to accelerate the pigments extraction. After 48 hours of incubation the extract liquid was filtered through glass wool to remove leaf pieces and transferred to another graduated tube. The liquid extract was made up to a total volume of 25 mL with 80% acetone. The chlorophyll content was spectrophotometrically analyzed, in a UV visible spectrophotometer (PG Instruments T80 UV/VIS Spectrometer – United Kingdom) using 3 mL sealed quartz-glass cuvettes with a path length of 1 cm. The chlorophyll content was calculated as mg/g by the following equations cited in Dere et al. (1998).
Chlorophyll a = 11.75 A662 – 2.350 A645
Chlorophyll b = 18.61 A645 – 3.960 A662
Randomized complete block design over cutting and treatments was used with three replications. Analysis of variance (ANOVA) was carried out using Proc Mixed of SAS package version 9.2 (SAS 2008) and means were compared by Duncan comparison at 5% level of significant (Steel ; Torrie, 1981).